The Telecommunications Illustrated Dictionary, Second Edition (Advanced & Emerging Communications Technologies)

The

TELECOMMUNICATIONS ILLUSTRATED DICTIONARY 2nd Edition

Advanced and Emerging Communications Technologies Series Series Editor-in-Chief: Saba Zamir Data and Telecommunications Dictionary, Julie K. Petersen The Telecommunications Illustrated Dictionary, Second Edition, Julie K. Petersen Handbook of EmergingCommunications Technologies: The Next Decade, Rafael Osso ADSL: Standards, Implementation, and Architecture, Charles K. Summers Protocols for Secure Electronic Commerce, Mostafa Hashem Sherif Protocols for Secure eCommerce, Second Edition, Mostafa Hashem Sherif After the Y2K Fireworks: Business and Technology Strategies, Bhuvan Unhelkar Web-Based Systems and Network Management, Kornel Terplan Intranet Performance Management, Kornel Terplan Multi-Domain Communication Management Systems, Alex Galis Fiber Optics Illustrated Dictionary, Julie K. Petersen

The

TELECOMMUNICATIONS ILLUSTRATED DICTIONARY 2nd Edition JULIE K. PETERSEN

CRC PR E S S Boca Raton London New York Washington, D.C.

Cover Background Credit: The cover background photograph portrays a dramatic moment in space research and wireless communications as the Student-Tracked Atmospheric Research Satellite for Heuristic International Networking Experiment (STARSHINE) is launched into space from the cargo bay of the Space Shuttle Discovery. [NASA photo.]

Library of Congress Cataloging-in-Publication Data Petersen, Julie K. The illustrated telecommunications dictionary / Julie K. Petersen.—2nd ed. p. cm. — (Advanced and emerging communications technologies) Rev. ed. of: Data & telecommunications dictionary. c1999. Includes bibliographical references. ISBN 0-8493-1173-X (alk. paper) 1. Telecommunication—Dictionaries. 2. Data transmission systems—Dictionaries. 3. Computer networks--Dictionaries. I. Petersen, Julie K. Data & telecommunications dictionary. II. Title. III. CRC Press advanced and emerging communications technologies series. TK5102.P49 2002 621.382′03—dc21

2002017481 CIP

This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonable efforts have been made to publish reliable data and information, but the authors and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage or retrieval system, without prior permission in writing from the publisher. The consent of CRC Press LLC does not extend to copying for general distribution, for promotion, for creating new works, or for resale. Specific permission must be obtained in writing from CRC Press LLC for such copying. Direct all inquiries to CRC Press LLC, 2000 N.W. Corporate Blvd., Boca Raton, Florida 33431. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation, without intent to infringe. Text design and layout by the author. Illustrations and photos by the author unless otherwise credited.

Visit the CRC Press Web site at www.crcpress.com © 2002 by CRC Press LLC No claim to original U.S. Government works International Standard Book Number 0-8493-1173-X Library of Congress Card Number 2002017481 Printed in the United States of America 1 2 3 4 5 6 7 8 9 0 Printed on acid-free paper

Preface to the 2nd Edition Expanded, Revised, and Updated Background It took almost 4000 hours to write the first edition of this dictionary and more than 2200 additional hours were devoted to expanding and updating it to create the second edition. It was heartening to be informed that the first edition is now used in training and certification programs all around the country and has been recommended by some of the top professional engineering organizations in the world. For those endorsing the first edition of Data & Telecommunications Dictionary, you’re going to find The Telecommunications Illustrated Dictionary is even better. First-time readers and owners of the first edition will appreciate the effort that has gone into this standard-setting reference. The dictionary was designed to meet a broad range of needs, and there is something for everyone, from working professionals to students and lay readers. Telecommunications is a diverse and exciting industry that interests engineers, system administrators, and hobbyists alike. The Telecommunications Illustrated Dictionary offers many unique features not found in other similar references: Historical Evolution This is the only telecom dictionary that systematically charts the evolutionary history of telecommunications up to the present and even into the future. It helps students and practitioners understand what goes into a technology, when it was invented, why it was developed, how it has changed, and how it is used in current practice. There are many advantages to this approach, including a greatly extended shelf life for your purchase. Technology books tend to become obsolete in a few months. This reference will be valuable long after succeeding versions are published because it includes fundamental physics and engineering concepts that underlie most telecommunications products. Web Addresses

While this book is not an Internet directory, the author felt that any dictionary published in the current day and age should contain Web site URLs for significant standards bodies, trade organizations, and not-for-profit associations. This dictionary includes hundreds of Web addresses carefully selected for stability and relevance to the content of the dictionary.

RFC Listings

Over 3000 RFC documents shape the format and evolution of the Internet. These important documents can be searched online, but sometimes it helps to get an overview of what is available first. Appendix F includes a categorized listing of some of the more significant RFCs.

Illustrations

This dictionary contains more than 400 illustrations, charts, and diagrams to make it easier to understand related standards, concepts, and formats. The information in the charts could have been listed sequentially as individual definitions, simplifying the author’s job, but they convey far more information when arranged as tables and charts, making the information easier to find. In many cases, the author has worked out the relationships among the terms to organize them functionally rather than alphanumerically to further convey their relationships and meaning. Quick-guide charts to ITU-T Series Recommendations have also been included, with extensive work to functionally categorize some of the larger archives.

High Content Level

The raw number of definitions in a dictionary is not always the best indicator of the overall amount of information provided. Since this is an encyclopedic dictionary, the definitions are longer than those in glossaries and most regular dictionaries. This approach is appropriate for a subject such as telecommunications where concepts are more dependent upon one another than, say, words in an English language dictionary. It would have been easy to split many of the longer definitions into two or three smaller definitions, in order to claim over 20,000 entries (for marketing purposes), but it wouldn’t have increased the overall content of the book and, in fact, would have reduced the clarity of the conceptual relationships among the different technologies. This edition contains about 35% more content than the first edition.

The Changing Face of Technology Jonathan Winter, founder and curator of the American Radio Museum, is to be credited with emphasizing the importance of radio history to modern-day electronics. He describes how technology has become “invisible,” in the sense that it is now largely hidden within circuit boards and highly-integrated silicon chip technologies. He points out that the only way to get an in-depth or even an introductory understanding of what is happening within those circuits is to look at the evolutionary development of capacitors, transmitters, storage batteries, and all the breakthrough achievements that have brought us to this remarkable moment in our current telecommunications history. The author extends gracious thanks to the Museum for the time and effort Mr. Winter and his assistant Paul devoted to demonstrating and explaining the many historical radio and other electronic artifacts. Winter also kindly permitted the exhibits to be photographed by Classic Concepts and reproduced in this reference.

Research The evolution of computers and the World Wide Web has been full of surprises and has dramatically changed the tools used by writers and researchers. The first edition of this dictionary was produced on a 20-MHz system with a 2400-baud dialup modem connected to an ISP that greeted the author with busy signals more often than not. Fast access to the Internet in those days was $500 a month, too much for a writer’s budget. Thus, the use of the Web as a research source for the first edition was not practical, not only because of Internet access limitations, but because Web content in the mid-1990s was minimal and unsophisticated. To complicate matters further, top level domain names were expensive, most people had user accounts rather than their own domains and the account addresses kept moving; they couldn’t be listed in the dictionary because they were likely to change before the volume was printed. This has all changed in a surprisingly short time. Computers and Internet access are now fast and cheap, and a rich variety of resources is available on the Web. Many sites are sophisticated and even beautiful, and sorting the wheat from the chaff now takes more time than locating good information. One thing hasn’t changed, however, and that is the perpetuation of erroneous information over the Net by well-intentioned individuals. The author discovered that many sources blindly copy “facts” from each other without seeking authoritative sources (often without attribution). Birth dates and invention dates are frequently wrong, and distinctions such as the difference between a patent and a caveat to file are frequently overlooked. As a trivial but telling example, the rumbatron is an important technological forerunner to the linear accelerator, yet a search on Google in December 2001 didn’t bring up a single “hit” for rumbatron. On a hunch, the author searched “rhumbatron” and got more than a thousand hits. This result was surprising, considering the author had ferreted out a document in the coinventor’s handwriting in which it was clearly spelled “rumbatron.” The Internet is great for sharing information, but it can also spread misinformation worldwide in mere seconds. So who is to be believed? A coinventor, or 1000 well-meaning posters on the Web? For now, regarding “rumbatron” and more important but similar aspects of fact, the author has selected the coinventor, but continues seeking out corroborative sources, a process that can take weeks or months beyond the time allotted for preparing a manuscript. It is the author’s hope that this extra effort will facilitate an accurate portrayal of the origins and evolution of the technology. The commitment to creating a good reference is not without a price. This dictionary sells for more than similar volumes and extra legwork is required to satisfy professional standards. It is the author’s firm belief that the reader understands these economics and is entitled to the author’s best effort. An astonishing time of change and innovation is at hand that deserves to be well documented. In the end, no reference is perfect, including this one, and no doubt small details could be argued indefinitely by historical and technical scholars, but the author’s goal remains the same – to make this the world’s best dictionary covering the field of telecommunications.

Julie K. Petersen, April 2002

Preface & Acknowledgments to the 1st Edition

C

reating a technical reference for a field that changes by the minute is a particular challenge and this book would not have come about without the assistance and support of a great number of dedicated librarians, museum curators, and museum volunteers, who gave graciously and generously of their time and energy. They patiently answered my numerous and persistent questions and pointed the way to original and, in some cases, rare references. Special thanks go to the Bellingham Antique Radio Museum, which provided a provocative and educational look into the development and construction of historic and present-day communications technologies, and permitted me to photograph the fascinating collection. Several local independent book stores deserve thanks for providing leads to turn-of-the-century early editions on telegraph and telephone technology: Michael’s Books, Eclipse Books, Henderson Books, and Village Books. Old books, historical artifacts, diagrams, and schematics are more important to the study of contemporary electronics than many people realize. Since the development of semiconductors, technology has become ‘invisible,’ that is, you can no longer see what a component does or how it works by simply looking at it, or taking it apart and putting it back together. Yet, to work in design and engineering-related fields still requires an understanding of the underlying physical and relational concepts. For this reason, a number of basic historic devices and schematics are included here to give a better understanding of the background and inter-relationships of electronics and the roles they play. Sources In the course of developing this dictionary, I discovered that many references are derivatives of each other and do not go back to original sources, instead perpetuating common lore that lacks verification and accuracy. For the Data & Telecommunications Dictionary, I made special efforts to seek out the origins of various telecommunications inventions, discovering that Morse probably didn’t develop Morse Code, that the Wheatstone bridge was described but not invented by Charles Wheatstone, and that printed circuit boards were invented at least 12 years earlier than previously acknowledged. These stories give life to what might otherwise be a dry reference, and a few more important antecedents and surprises are similarly documented in these pages. Dictionaries tend to be ethnocentric. Language is partly responsible for this, as it is difficult for most authors to access or read foreign references. I was aware, while writing this book, that there are undoubtedly foreign contributions to technology, particularly from Asia, an ancient culture, that might be commonly overlooked and not acknowledged. The Web helped. It enabled me to locate information on early inventions and cultural contributions from Russia, the Orient, India, and the West Indies that were not documented in any of the written references I had so carefully and persistently ferreted out. We can look forward to more of these unsung heroes coming to light as the global populace comes online. Their stories are inspiring and intriguing and, even if their contributions didn’t reach the mainstream of western culture in terms of human endeavor, they have made important contributions that are worth acknowledging. Format In reviewing other references, I noted that most dictionary authors avoid the time and effort required to find out which entries are spelled in upper or lower case, choosing to begin every entry with a capital letter. This may save work, or satisfy some aesthetic need, but it does not fulfill one of the functions of a reference, which is to provide you, the reader, with correct spellings, or at least to suggest the conventional spellings of the various terms. In the telecommunications industry, there is a lot of variation and, in some cases, no definitive answer, but there are discernible patterns, so I have endeavored to find reputable sources and to provide good guidelines. In general, protocol names and commercial products or commercially derived technologies begin with capital letters; software commands, generic technologies, and general concepts are spelled with lower case letters.

In the same vein, American authors tend to Americanize the spellings of European organizations (organisations), inventors, and commercial products. This reference seeks to respect the names assigned by foreign countries (e.g., Fibre Channel rather than Fiber Channel). There are a few exceptions. In some cases an Americanized version is used so often it becomes an ad hoc standard, and may be used here somewhat interchangeably, depending upon the context, e.g., ISO is expressed by many Americans as International Standards Organization when it is actually the International Organization for Standardization. Recent Technologies In surveying other computer references I discovered that some authors convey the mistaken impression that Microsoft invented everything. Without taking any credit away from the bestknown commercial software vendor, in fact, most of the significant computer technologies were developed long before Microsoft was founded, by pioneers at Bell Laboratories, the IBM research labs, Xerox PARC, Dartmouth College, Carnegie-Mellon, and many small independent design and development firms. I have taken pains to include Joseph Henry, the Lorimer brothers, Gary Kildall, Alan Kay, Jonathan Postel, Konrad Zuse, and many lesser-known contributors, so that this reference reflects a more accurate slice of history. As such, it credits the Kenbak-1* as the first microcomputer, three years prior to the introduction of the Altair. I felt readers would appreciate this attention to accuracy. I only wish there had been more time to delve into the ‘real’ history of computing and telecommunications. Many references steer clear of documenting recent technologies, particularly satellite projects, new products of significance, important protocols, and organizations developing and supporting them. I now understand why. No sooner did I list a new development, when another stepped in to take its place. I further discovered that it takes as long to research a definition of a new technology (you essentially have to learn it before you can describe it) as it does to research an entire page in many types of prose books. To deal with obsolescence, I have tried to present information in its broader context, since the concepts remain, even if the mechanics change over time. It is hoped this approach will extend the useful life of this reference, and that over time it will retain its value because it documents not just current products, but the overall development and evolution of the industry. Special Thanks The author would like to thank Saba Zamir for suggesting the topic and Mimi Williams for her patience and assistance. Jonathan Seagrave provided a sounding board for some of the tougher physics questions associated with the first edition. Finally, special thanks go to Dan Suslo, Craig Butler, and Paul Carpentier, who went out of their way to offer support and assistance during the final and most difficult parts of assembling this extensive project. Your efforts are remembered and greatly appreciated. Julie K. Petersen, July 1998

*Note that the Arkay CT-650, Simon, and other pioneer systems are also listed.

About the Author Julie K. Petersen is a technology consultant, author, educator, and outdoor enthusiast, living in the Pacific Northwest. In her not-so-spare time she enjoys reading, music, film, strategy games, and interesting cuisine. She has been using computers and telecommunications technologies on a daily basis since 1979 and reflects on her early telecommunications experience: “My first modem was one of those “suction cup” models that you had to hide in a corner away from the radio or TV (or noisy roommates) to get it to work. Those were fun times, actually, even though many computer components were unreliable. The printed circuit board for my modem interface was small and subject to ‘curl’ when the computer had been on for a while and got hot. To make matters worse, the DC/DC converter on the board was temperamental. It took monumental patience to keep the thing working so I could get a good connection and stay online for 15 minutes at a time at 300 blazing baud! I took to telecommunications and computers right away, even though I had no prior experience with technology. I think what matters most is attitude and curiosity. By 1979, I was following the careers of the up-and-coming computer hobbyists, Gates and Allen and “the two Steves” (Wozniak and Jobs) and subscribing to some of the earliest personal computer magazines. I met Cap’n Crunch and many of the early Amiga developers on FidoNet in 1985. Back in January 1981 I had even written some text adventure games, but I was living in a town of only 12,000 and couldn’t find out how to access commercial distribution channels. Too bad. Those early games developers made a lot of money. :-) Computer and telecommunications systems in 1979 were simple enough that you could fully understand how they worked and fix and upgrade them yourself. Now it takes 60 people to design the average computer system. In the late 1970s, bulletin board systems (BBSs) were just becoming popular. The idea of linking to other people with modem-equipped computers was new and very exciting. The early BBSs didn’t even require passwords; they were on the honor system. As computing spread, the idea of selfpolicing went by the wayside. Too bad. Security is now one of the biggest challenges facing telecommunications professionals, especially with the entire commercial world coming online. I found out by accident that I was an “early adopter,” using USENET, FidoNet, Internet Relay Chat, and Web browsers almost as soon as they were installed. It was not until I began researching the history of these services that I realized that they had been available in my area only for a few hours or days before I discovered them; I assumed they had been in existence much longer. I mention this to express how lucky I was. Many of the “celebrities” of current telecommunications and computing technology were visible and vocal on networks in those days, and I had a chance to meet them and discover not only their brilliant visions, but their characteristically wry and devilish humor. It’s harder now to feel that same sense of community. Because of fans, harrassment, and the dilution of USENET groups by inappropriate discussions that are off-topic, many of these pioneers have become invisible, hiding behind handles (pseudonyms) when they participate at all. They sometimes turn up on moderated chats on IRC, but with millions of participants joining in to ask questions, there aren’t as many personal, in-depth discussions as in the early days of networking. But for each thing that is lost, something else is born. The “bleeding edge” is rarely profitable but you get to interact with techies who pursue it because it is exciting, challenging, and forces us to take a philosophical look at our priorities, values, and even our existence and relationship to evolving “digital intelligences.” Telecommunications is a toolbox in which every tool can be used for good or bad. Unchecked, telecommunications can grow into the mythical Hydra, threatening our safety and security and growing new heads at every opportunity. Instead, it is my hope that engineers, system administrators, and decisionmakers will make an effort to develop and use the technology to improve quality of life, not to create a civilization where people are slaves to the computer, spending all their time entering, seeking, and cataloging the vast and growing amount of information that telecommunications make possible. I wrote this dictionary to help the reader save time and learn about the technology. That’s my contribution. I hope, in turn, that readers will use some of that time to contribute to the development of future technologies that seek to enhance our quality of life rather than lengthening the work week. That’s the best possible use we could make of the products of our inventive minds.”

How to Use The Telecommunications Illustrated Dictionary General Format

There are two sections to this reference: (1) a main alphabetical body, with numeral entries at the end, after Z and (2) several appendices with various charts, an extended section on ATM, a quick lookup acronym dictionary, and a timeline of telecommunications inventions and technologies. Entries Dictionary entries follow a common format, with the term or phrase in boldface, followed by its abbreviation or acronym, if applicable. Pronunciation is included in cases where it may not be obvious. Alternate names (e.g., William Thompsom, a.k.a. Lord Kelvin) are cross-referenced. The body of the entry is included next, with multiple definitions numbered if there are several meanings for a term. Finally, where appropriate, there are cross-references, RFC listings, and URLs included at the end, in that order. Abbreviations In many cases, the term and its abbreviation are described together so the reader doesn’t have to look up abbreviated references to understand a particular entry; for example, cathode-ray tube will often be followed by (CRT) and Federal Communications Commission by (FCC) so the words and their commonly used abbreviations become familiar to the reader. Web Addresses Web addresses based upon Uniform Resource Locators (URLs) are listed for nonprofit, not-for-profit, charitable, and educational institutions and, in a few rare instances, for commercial enterprises with particular relevance for telecommunications or with substantial educational content on their Web sites. For the most part, commercial URLs are not included. If the address isn’t listed, it can often be guessed (http://www.companyname.com/) or otherwise easily located through Web search engines listed in Appendix D. RFCs Request for Comments (RFC) documents are an integral part of the Internet, and extremely important in terms of documenting the format and evolution of Internet protocols and technologies. For this reason, RFC references are listed with many of the Internet-related references and can be found in numerous RFC repositories online. There is also a partial list of significant or interesting RFC documents listed according to category in Appendix F. Diagrams and charts Illustrations are included as close to the related definition as was possible in the space provided. Extensive listings of the various ITU-T Series Recommendations are included in almost every chapter because they are the standards upon which most Internet technologies, telecommunications standards, and commercial products are built. Charts are usually included on the same page as the related definition or the one following. term or phrase abbreviation or acronym pronunciation

definition

cross-references Request for Comments reference number Web address (URL)

Bootstrap Protocol BOOTP. (pron. boot-pee) An IP/UDP client/server means of storing and providing configuration information. BOOTP evolved in the ARPANET days to allow diskless client machines, and other machines which might not know their own Internet addresses, to discover the IP address, the address of a server host, and the name of a file to be loaded into memory and executed. This is accomplished in two phases: address determination and bootfile selection; and file transfer, typically with TFTP. This has since evolved into Dynamic Host Configuration Protocol (DHCP). See Address Resolution Protocol, Dynamic Host Configuration Protocol, Reverse Address Resolution Protocol, RFC 951. http://www.urlgoeshere.org/

Contents Preface Alphabetical Listings A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Numerals Appendices A. Telecommunications Timeline B. Asynchronous Transfer Mode (ATM) C. ITU-T Series Recommendations D. List of World Wide Web Search Engines E. List of Internet Domain Name Extensions F. List of Request for Comments (RFC) G. Bibliography H. Acronyms and Abbreviations I.

Telephone Area Codes

J.

Dial Equivalents, Radio Alphabet, Morse Code, Metric Prefixes/Values

K. ASCII Character and Control Codes

a 1. symb. acceleration. See Acceleration 2. symb. anode. See anode. 3. abbrev. area. 4. abbrev. atto-. See atto-. A 1. symb. acoustic velocity. See acoustic velocity. 2. symb. ampere. See ampere. 3. symb. gain. See gain. A & A1 leads See A/A1. A & B Numbers 1. Designations for two of the commonly-used wireless communication service categories available through Inmarsat satellite relays. Inmarsat A & B services are commonly used for shipto-shore communications. The Inmarsat A & B Numbers vary depending upon the ship and which satellite a ship is using, but include voice, facsimile, and data lines. See Inmarsat for a chart of service categories. 2. In mobile radio systems in general, but especially cellular, the A Number is a designation for the originating call point, signaling towards the network, and the B Number is the destination or answering point. A & B bit signaling In communications networks, control or status information about the communications line itself may be interspersed with the data content that is being transmitted through that line. This is a form of in-band signaling. A & B bit signaling is a technique of inserting signal state information into particular bits at intervals in the data transmission, thus robbing a certain number of bits from the total transmission. For example, A bits are used in voice communications implemented over T1

A

superframe (SF) networks to indicate outbound call signaling, with B bits as mirrors to the A bits. Through bit robbing, the A and B signal bits are carried in each 6th and 12th frame, respectively, of each of the 24 T1 subchannels. The types of supervisory information contained in these signal bits is relevant to switched voice or switched data services, including ring, busy, off-hook, and on-hook states. In extended superframe (ESF), A, B, C, and D bits may be robbed from the 6th, 12th, 18th, and 24th frames. In some telephony systems, tone signaling is converted to A & B bit signaling for interoperability. There is a trade-off when bits are robbed. Since the available bits are not all used for data, the total throughput is less when measured over time. However, for less demanding voice communications, for example, the difference in speed and quality of the signal is not subjectively apparent to the listener. Diagnostic T1 channel decoders typically show the A and B bit signaling status, along with other alarm, frame loss, or error conditions. Newer T1 systems based on B8ZS line-code substitution don’t use this bit-robbing technique. A battery 1. A low voltage battery historically used to provide current to filaments or cathode heaters in electron tubes, now commonly used for small electronic appliances such as cameras, calculators, pen lights, etc. See battery. 2. An A battery is a historic nonrechargeable wet cell called an air cell, with

FCC-Designated Communications Frequency Blocks Block

Blk. Size Frequency

Paired Frequency

Notes

Date

A Block

30 MHz

1850-1865 MHz

1930-1945 MHz

MTA Broadband PCS

1994-1995

B Block

30 MHz

1870-1885 MHz

1950-1965 MHz

MTA Broadband PCS

1994-1995

C Block

30 MHz

1895-1910 MHz

1975-1990 MHz

BTA Broadband PCS

1995-1996

D Block

10 MHz

1865-1870 MHz

1945-1950 MHz

BTA Broadband PCS

1996-1997

E Block

10 MHz

1885-1890 MHz

1965-1970 MHz

BTA Broadband PCS

1996-1997

F Block

10 MHz

1890-1895 MHz

1970-1975 MHz

BTA Broadband PCS

1996-1997

A

carbon electrodes providing an average power of 2.0 volts. See talk battery. A Block A Federal Communications Commission (FCC) designation for a Personal Communications Services (PCS) nonwireline license granted to a telephone company serving a Major Trading Area (MTA) which grants permission for broadcasters to operate at certain FCC-specified frequencies. See band allocations. See FCC-Designated Frequency Blocks chart. A cable A 50-pin data cable commonly used for SCSI peripheral connections. See A connector. A carrier alternate carrier. A Federal Communications Commission (FCC) designated nonwireline competitive telephone cellular service carrier which is not the established local wireline carrier (B carrier). See B carrier. A channel In a system with two or more audio channels (e.g., stereo), the designation for the left audio channel, usually connected to the left speaker or microphone. Audio cables are sometimes color-coded to aid recognition, with white conventionally used for the left channel and red for the right. A connector A standardized 50-pin electrical data connector as defined by ANSI which is typically used for connecting SCSI devices such as hard drives, cartridge tape drives, etc. SCSI-2 and SCSI device connectors are not physically compatible, for the purposes of connection, but are electrically compatible so that they can be daisy-chained to coexist on the same bus. For some devices, manufacturers provide P connector (68-pin) to A connector adaptors to enable newer peripherals to be used in older computers. There are also a few P connector-like devices made with 50-pins so that a device can be connected without an adapter. See P connector. A interface See air interface. A law See A-law encoding. A link See access link. A minus, A- The negative polarity of a voltage source, for example, the negative terminal of an A battery. A News An early UUCP-based news-reading software program released in 1979. It was developed by Tom Truscott, Jim Ellis, and Steve Bellovin, with enhancements and modifications a year later by Steve Bellovin, Steve Daniel, and Tom Truscott. It inspired many subsequent programs for reading Internet discussion lists. See newsgroup, USENET. A operator In historic manual telephone trunk lines, established in the early 1900s, one of two operators working together on separate switchboards to handle incoming and outgoing calls. The A operator would handle the switchboard calls coming from outside the local exchange area and relay them to the B operator at another switchboard for connection to local subscribers and vice versa. A plus, A+ The positive polarity of a voltage source, for example, the positive terminal of an A battery. A port In a Class A, dual-attachment (dual ring) Fiber Distributed Data Interface (FDDI) token-pass-

ing network, there are two physical ports, designated PHY A and PHY B. Each of these ports is connected to both the primary and the secondary ring, to act as a receiver for one and a transmitter for the other. Thus, the A port is a receiver for the primary ring and a transmitter for the secondary ring. The dual ring system is configured to provide fault tolerance for the network. Port adaptors can be equipped with optical bypass switches to avoid segmentation, which might occur if there is a failure in the system and a station temporarily eliminated. FDDI ports can be connected to either single mode or multimode fiber optic media, providing half duplex transmissions. LEDs are commonly used on port adaptors as status indicators. Optical bypass switches may in turn be attached to the port adaptors. See dual attachment station, Fiber Distributed Data Interface, optical bypass, port adaptor. A Programming Language APL. A high level, interactive computer programming language, APL descended from a notation system developed by Kenneth E. Iverson at Harvard in the late 1950s. It was developed to facilitate the description of certain mathematical concepts and evolved into APL when Iverson joined IBM in the early 1960s. APL did not resemble any programming language with Englishlike syntax. It initially required a special keyboard and incorporated many special characters and Greek letters. It has been extended over the years to include more syntactically familiar elements. It is suitable for succinctly describing systems that are more amenable to mathematical representation rather than English-language structure representation, making it suitable for scientific, aeronautic, statistical, and similar applications. Brad McCormick has published an oral history of APL on the Web. A Series Recommendations A series of ITU-T recommendations providing guidelines for administration, working methods, and communication of information by personnel and working groups. These guidelines are available as publications from the ITU-T for purchase and many in the A Series are downloadable without charge from the Net. Since ITU-T specifications and recommendations are widely followed by vendors in the telecommunications industry, those wanting to maximize interoperability with other systems should be aware of the information disseminated by the ITU-T. A full list of general categories is listed in Appendix C and specific series topics are listed under individual entries in this dictionary, e.g., B Series Recommendations, C Series Recommendations, etc. See A Series Recommendations chart. A-0 A software programming tool developed by Grace Hopper in the early 1950s at Remington Rand (which merged with Sperry Corporation). Cumbersome paper tapes and punch cards were common at the time and Hopper was seeking more efficient ways to handle code. Binary coding was long, tedious to generate, and difficult to debug. Hopper developed A-0 to compile from higher level symbolic code (more understandable to humans) to machine

Examples of ITU-T A Series Recommendations Recom.

Year

A.1

2000

A.2

2000

A.3

1996

A.4 A.5

2000 2000

A.6

2000

A.7 A.8 A.9

2000 2000 2000

A.11 A.12 A.13 A.23

2000 2000 2000 1996

A.30

1993

Description

A

Work Methods for Study Groups of the ITU Telecommunication Standardization Sector Presentation of contributions relative to the study of questions assigned to the ITU-T Elaboration and presentation of texts and development of terminology and other means of expression for Recommendations of the ITU Telecommunication Standardization Sector Communication process between ITU-T and Forums and Consortia Generic procedures for including references to documents of other organizations in ITU-T Recommendations Cooperation and exchange of information between ITU-T and national and regional standards development organizations Focus Groups: Working methods and procedures Alternative approval process for new and revised Recommendations Provisional working procedures for the Special Study Group on IMT-2000 and Beyond Publication of ITU-T Recommendations and WTSA proceedings Identification and layout of ITU-T Recommendations Supplements to ITU-T Recommendations Collaboration with the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) on information technology. Annex A is the Guide to ITU-T and ISO/IEC JTC1 cooperation. Major degradation or disruption of service There are also supplements available on quality and interoperability.

language (more understandable to computers). See B-0; Hopper, Grace Murray. A-1 time An atomic time scale established by the U.S. Naval Observatory. The origin is set at 1 January 1958 zero hours Universal Time with a second unit equal to 9,192,631,770 cycles of cesium at zero field. See atomic clock, Universal Time. A-law encoding A pulse code modulation (PCM) coding and companding scheme used outside North America as the CEPT standard. A-law is commonly used for analog-to-digital conversion for encoding speech by sampling the audio waveforms and applying logarithmic quantization. See E carrier, Mu-law coding, pulse code modulation, quantization. A-scope, R-scope A specialized radar tracking scope for indicating the range of objects being detected, displaying all targets as illuminated vertical blips, scanning repeatedly from left to right. See B-scope. A/A1 Conductor leads in key telephone systems to implement hold functions. When a line is placed offhook, the A lead is shorted or bridged to the A1 lead to put the line on hold. A similar concept is the MB/ MB1 bridge that puts the affected line into an unavailable or busy state. The bridged states may be indicated by LEDs, depending upon the phone design. Line sensing products that sense A and A1 lead con-

trols on key telephone lines are of interest to firms that make heavy use of telephone services and automation, such as telemarketers. Line sensors can detect current and line status and, if desired, activate a relay to allow dialers and other devices to be interfaced with key systems. They may also provide key phone control leads for telephone equipment not using key system units. A/B Roll, AB Roll A basic type of editing that is widely used in predominantly analog video studios. In general, there are two video sources, typically two cameras, two VCRs/VTRs, or one of each (designated A and B) and one destination, typically a live broadcast link or recording machine (e.g., another VTR). The A and B sources may be manually controlled or remotely controlled by handheld wireless controllers or an integrated video editing controller (VEC). A VEC that can control both decks from one console is the easiest, most comfortable, and most precise way to control the two video sources, especially if it can process industry standard SMPTE time code. The A/B Roll analogy has been implemented in some digital video systems, but given the random access nature and efficiency of digital storage and retrieval, it’s perhaps not the best model. On analog A/B Roll systems, the editor may spend much time rolling tape,

especially if the A and B sources are both prerecorded video tapes, and it can take considerable time to find and mark all the segments of tape that will eventually be edited together. To facilitate this process, many editing decks include jog/shuttle dials for quicker searches, and some have memory capabilities that allow the user to mark several edit segments and roll automatically to those segments in the desired sequence. A digital version of the traditional A/B Roll is much more direct in that files are read in quickly from any number of sources and assembled visually on a timeline until everything is ready to store or rerecord. The results can be previewed as often as desired before transferring the intermeshed segments to the final medium, without arduous tape rolling required to relocate relevant segments in serially-recorded media. Digital editing or nonlinear editing has numerous advantages, but many video houses have tens of thousands of dollars tied up in analog equipment and training, and the transition to digital will take a few years. Eventually the more fluid and flexible digital assembly methods will supersede A/B Roll, especially with the growing demand for multimedia productions for distribution through the Internet. A/B switch 1. A dial or switch with two settings for controlling sources of input and output to a circuit. Typically an A/B switch enables the user to mechanically complete a circuit between one of two inputs and one output or between one input and one of two outputs. A/B/C and A/B/C/D switches are also common. See A/B switchbox, switcher. 2. A setting on various appliances allowing a user to select between two operating modes, such as wireline or nonwireline, or between two optional frequencies. 3. In cellular communications, many new transceivers have an A/B switch that enables the user to select between a wireless or wireline connection when roaming.

A/B switchbox front and back. Passive switchboxes are commonly used to interconnect computers with various peripherals. For example, a serial cable leading to a modem could be plugged into the input connection, and A and B could each be connected to a different computer to share a modem. Another configuration is to connect a computer to the input connection, and attach A to a modem and B to a printer, so that a computer with one serial port can alternately use two peripherals. Most common data switchboxes have female 25-pin D connectors, as shown here.

A/B switchbox A very common, usually passive, connection-routing device selected by a switch and providing receptacles or sockets for various connec-

tors. Most inexpensive switchboxes provide mechanical routing for low-voltage electrical circuits. More advanced switchboxes may provide automated switching or digital switching services. Mechanical switch settings are usually selected by a dial, a lever, or buttons. A/B switches are commonly used with video circuits and computer peripheral devices, though they are generic to almost any electrical device where line resources are shared. In computing, A/B switchboxes help manage shared resources. They can be used to switch a serial communications line between a printer and a modem or facsimile machine, or between two different printers, such as a laser printer and a pen plotter. These serial boxes commonly have 25-pin D connectors on the back, one for the input, which may be from the computer, and two for the output, which may be a printer and modem (or vice versa). A gender changer or converter (e.g., 9-pin) is sometimes needed to connect the selected cable to a computer with a 9pin socket. On the front of a switchbox, there is usually a blank space for labeling the connections. A/B/C and A/B/C/D switchboxes are also common. A crossover switchbox is similar to a straight switchbox, but provides multiple input and output combinations, and usually has four or more ports on the back for attaching the input and output connectors. Switchers are similar to switchboxes, and are frequently used in live broadcasts and video editing to select among various video sources (cameras, VCRs) and computer-generated signals. Video switchers (sometimes called selectors) typically use RCA and BNC connectors to accommodate standard video cables. More recent video switchers may also have S-VHS ports. See switcher. A/D 1. analog/digital. 2. analog to digital. A/D conversion Conversion of analog to digital signals, often for transmission over data networks or for sampling by computer applications such as speech or voice recognition software or music sequencing and editing software. The advantage of converting to digital format is that many types of processing can be applied to the data, including image or sound editing, sequencing, compression, encryption, error-correction, and more. Some common A/D conversion applications include: • Analog sound capture through a microphone with the data being digitized for use over a digital mobile communications link or for use with a computer to capture music or voice as digital samples for later processing or playback. • Analog image capture for transmission to a computer or videoconferencing unit for digital transmission over the Internet. See audiographics. • The use of modems for modulating analog telephone signals into digital serial transmissions for use by a computer processing the data. A/UX A 32-bit Unix operating system designed for use on Apple Macintosh computers in addition to or in place of the Apple operating system. A/UX is derived from AT&T’s UNIX (when capitalized, UNIX

refers to the registered trademark of X/Open Company), BSD, with full POSIX compliance and System V Interface Definition (SVID) compliance. A/ UX provides The X Windows System, sh, csh, and ksh. A/V audio/visual. An abbreviation that has been used colloquially for a long time to refer to a wide variety of audio/visual media and devices, including film projectors, video tape players, laserdisc players, televisions, and just about any educational or entertainment broadcast or playback unit that provides both sound and images. A/V switch A device that enables various audio/visual sources to be selected as needed. An A/V switch is particularly useful in situations where space or cost limits the available resources as when monitors, speakers, or other components are shared among multiple inputs. A/V switches are common in video editing studios and are now becoming common in home entertainment centers, that is, consumer audio/ visual systems that allow selection between a variety of services or components such as satellite or cable television, DVD players, VCRs, etc. A4 An international paper size standard (ISO and JIS), commonly used in Europe, corresponding to 210 x 297 mm (8.27 x 11.69 in.). Similar to this in North America is letter sized paper which is 8.5 x 11 in. Some but not all laser printers can accommodate A4. Some facsimile machines, most plotters, inkjet printers, and dot matrix printers have enough leeway on the carriage size or printing surface to accommodate European paper sizes. AA See Automated Attendant. AAA See authentication, authorization, and accounting. AAAC all aluminum alloy cable. See ACSR. AAAI See American Association for Artificial Intelligence. AAAS See American Association for the Advancement of Science. AABS See Automated Attendant Billing System. AAC 1. See abbreviated address calling. 2. See Aeronautical Administrative Communications. AACS See attitude and articulation control subsystem. AAL ATM adaptation layer. See asynchronous transfer mode, and see the appendix for several pages of extended definitions and diagrams. AAMOF An abbreviation for “as a matter of fact” which is used in email and on online public forums. See AFAIK, IMHO. AAP 1. See Advanced Adaptive Protocol. 2. See applications access point. AAPI See Audio Applications Programming Interface. AAPT See American Association of Physics Teachers. AAR See automatic alternate routing. AARP See AppleTalk Address Resolution Protocol. AAS authorized application specialist. ab- A prefix commonly used with names of practical

electrical units in the centimeter-gram-second (CGS) electromagnetic system, e.g., abampere. AB Roll See A/B Roll. abacus An ancient computing device, historically descended from boards with sand that were used as accounting and counting aids. Native Americans used a type of abacus using grains as counters. Other cultures used beans or stones. One familiar form of Chinese abacus consists of beads resting in grooves or strung on wires within a frame. The beads are separated by a bar into upper and lower regions. In the version shown in this diagram, the values of the beads are assigned from bottom to top, and right to left. In the first row each lower bead represents one, while in the upper row, each bead represents five. From there, each row of beads increases in value by a factor of ten compared to the previous row.

This common Chinese abacus, a type of manual calculator, is one of many arrangements of boards, beads, and frames. There are usually 13 vertical rungs with two beads on the top level and five on the bottom separated by a bar, though this configuration may vary from region to region and with the size of the abacus itself. Variations are still used in commerce in many Asian and Eastern European regions.

ABAM An older Western Electric (now Lucent Technologies) cable designation for 22-AWG, 110ohm, individually shielded, twisted pair cable that is typically used in central office trunk line, circuit line, T1, and T1 to E1 channel service installations. Newer adaptations of ABAM are often listed by vendors as ABAM/T1 cable. For T1, ABAM has a drive capability of up to about 200 meters and a loss of about 0.4 dB/30 meters. A higher gauge fuse cable is sometimes used in conjunction with ABAM for aerial installations. See category of performance for newer cable types. See fuse cable. abampere, ab-ampere In the centimeter-gram-second (CGS) system, an absolute unit for current. Since the abampere is often too large for practical convenience, current is described instead in terms of amperes (one-tenth of an abampere). See ampere. abandoned call See call abandons. abandoned call cost An economic calculation to estimate the amount of revenue lost. Abandoned call cost estimates are primarily used by businesses whose customers order products or services through

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the telephone, or whose inquiries lead to sales later on. It’s impossible to know how many of the calls would have generated revenue and how many would have been completed later, but business owners may benefit from rough estimates based on the number of abandoned calls times the percentage of anticipated sales resulting from those calls. See call abandons. Abbe condenser A simple type of two-lens condenser invented by Ernst Abbe. It is used in photomicrography, where sufficient lighting is important. The condenser is located below the stage of a microscope so it can collect, direct, and spread light up onto the object being examined and recorded. It aids visibility in high magnification environments. Abbe, Ernst (1840-1905) A German mathematician and physicist who worked at Zeiss Fabrications and later became an owner. He developed a number of optical theories and invented a variety of optical condensers and metering instruments. See Abbe condenser. abbreviated address calling AAC. In data network information routing, calling an address with fewer than the normal number of characters, usually from a table or file in which abbreviated address codes are stored. Similar in concept to speed dialing or abbreviated dialing on phone networks. abbreviated dialing AD. 1. A feature of a phone which allows a short dialing sequence to replace a longer one. The abbreviated sequence can be programmed in and associated with a longer number; then, when the shorter sequence is dialed, the system connects to the associated phone number. Also known as speed dialing. 2. A priority telephone service using special grade circuits, in which two or more subscribers can connect calls with fewer than usual dial tones. ABC 1. arbitration bus controller. 2. See AtanasoffBerry Computer. 3. automatic bass compensation. A circuit that increases the amplitude of bass notes to create more natural sound at low volumes. Used especially for playing back music recordings. 4. automatic bias control. See bias. 5. Automatic Bill Calling. A billing method for coin phone calls that is being superseded by calling card billing. 6. automatic brightness control. A circuit that senses ambient light levels and adjusts a display device automatically in order to optimize brightness levels for the viewer. ABCD bits In network systems, a method for signaling using robbed bits, which provide in-band status information. The number of bits robbed depends upon the system. In Extended SuperFrame systems, four bits, designated ABCD, are utilized. See A & B bit signaling, Extended SuperFrame, robbed bits. ABEC Alternate Billing Entity Codes. See Alternate Billing Services. abend abnormal end. Abnormal or premature termination of a task or process, one which cannot be handled by available error recovery mechanisms. An undesired abend may result in a program or operating system hanging or crashing. In workstation level computers, abend problems with

applications software are usually handled by the operating system so that the system itself does not crash, and there are usually mechanisms for killing individual processes that are locked or hung so that other processes are not affected. System-level abend problems on well-tuned networks are actually relatively rare. Some, not all, of the microcomputer single-tasking systems, and less robust task-switching or multitasking systems, experience abend problems that may require a system reboot. (As a point of interest, this dictionary was originally created on a workstation that hasn’t crashed in over five years of 24-hour a day operations.) See abort. aberration 1. Deviation from expected shape, behavior, or path. 2. Failure of an image to coincide point-by-point with its original, as in a television image or facsimile. ABF air-blown fiber. See blown fiber. ABIST autonomous built-in self test. The capability of a system to automatically run built-in diagnostic routines. ablation 1. Removal of a part. 2. The process of removing parts, such as small holes, grooves, or pits in order to encode information on a medium. Many computer storage media are recorded by ablating thin layers of plastic or metal, e.g., optical media such as compact discs. ABM See asynchronous balanced mode. ABME asynchronous balanced mode extended. abnormal 1. Deviating from the normal, average, or expected. 2. A state, operation, or physical configuration that does not fit within expected, practical, or desirable norms. 3. The author’s favorite interpretation of abnormal is when Gene Wilder played Dr. Frankenstein in Young Frankenstein and his assistant mistakenly selected the brain of someone he mistook for Mr. A. B. Normal for implantation into Frankenstein’s monster. abnormal propagation In broadcast transmissions, undesired influences from atmospheric or ionospheric changes that interfere with signal integrity. Terrestrial impediments, unplanned movement, and reflective interference may also cause the abnormal propagation of transmission signals. In fiber optic transmissions, scratches or breaks in the tiny fibers can cause the laser light beams to diverge from their expected paths, causing abnormal signals. In computer networks, on a larger scale, data files, mail messages, viruses, or other communications may abnormally propagate through a system in unexpected quantities or directions due to accidental or deliberate manipulation of headers and routing information. abort 1. Stop prematurely or abruptly, cut off in miduse or transmission. 2. To terminate the transmitting or receiving of a message in progress. 3. To stop a software program or process in progress. An abend may be one type of abort, but abort more often signifies a situation in which a process is cleanly or voluntarily terminated without compromising system operating functions. 4. To terminate user access through a network or during a login, usually due to

detection of unauthorized access or tampering. abort delimiter In Token-Ring networks, a type 1 soft error signal transmitted if an internal hardware error has been detected or if a token bit of the Access Control Field is set to Token rather than Frame. An unsigned 8-bit integer is used for the Abort Delimiter Transmitted Errors field (tmac.errors.abort). The Abort Delimiter Transmitted counter is incremented when an abort delimiter is transmitted by a station and the total number is reported to the Ring Error Monitor. If excessively high numbers of abort delimiters are transmitted, the network needs attention. abort sequence 1. A series of processes, functions, states, or steps that leads to an abrupt end to the current function or transmission. Abort sequences are sometimes provided for safety reasons or may be a convenience to end a process that was initiated unintentionally (or which isn’t behaving in the desired way). 2. At the algorithmic or network protocol level, an abort sequence may be a pattern of sequential data that signals that an abort should be initiated. Abort sequences may be specifically defined for certain systems. They may restore a previous state or abort in such a way that current work is minimally disturbed. Sometimes there are established applications or hardware procedures for initiating an abort sequence. It is important to design abort sequences so they cannot be accidentally initiated and so they are not initiated by data sequences that unintentionally resemble abort sequences. Above 890 decision A 1959 decision of the Federal Communications Commission (FCC) granting permission for private construction and use of point-topoint microwave links. Thus, private companies, especially in remote locations, could utilize frequencies above 890 Mhertz for communications with oil rigs, power plants, gas pipelines, research stations, etc. The decision came about partly because of changes in technology, which made it less expensive and easier to use the higher frequency ranges for communications. This resulted in pressure to make these capabilities more widely available. Microwave Communications Inc. (MCI) was the first private commercial carrier service to take advantage of the Above 890 decision. See Telecommunications Act of 1996. ABR 1. See available bit rate, cell rate. 2. See autobaud rate. abrasion resistance A quality of a material to resist surface wear and tear during fabrication, installation, or use. Many rubbers, plastics, and metals are treated to increase their abrasion resistance. Network cables are often wrapped in a variety of gels, synthetic insulators, and metal sleeves to prevent abrasion, especially those used in harsh environments (e.g., deep sea installations). Neoprene and polyurethane are used for outdoor fiber optics cables, for example, while polyvinylchoride (PVC) is suitable for indoor cables. Abrasion resistance is quantitatively expressed in various ways, depending upon the industry and the type of material. abs abbrev. absolute value. See absolute value.

ABS See Alternate Billing Services. abscissa Conventionally the horizontal axis or X-axis in a Cartesian coordinate system. Absent Subscriber Service, Vacation Service A service offered by local telephone carriers that retains the absent subscriber’s phone number at a reduced rate so the subscriber will get the number back later, and that provides a standard recorded message to any people who call while the subscriber is away. absolute address In computer programming, the actual address in which a unit of data is stored (in contrast to a pointer to its storage location). 2. The binary address which directly designates a storage location. absolute altitude Altitude described relative to the surface of the Earth, as distinguished from altitude measured relative to sea level. absolute coding Machine level instructions that can be processed directly by a computer processor. absolute delay The time interval between two synchronized transmission signals from the same or different sources. absolute error 1. A means of expressing a deviation from a standard or expected value in terms of the same units as the units of the value. In statistical population distributions or other scatter distributions, this is a common way of indicating a deviation. 2. The absolute value, that is, the value without regard to sign, equal to the value of the error. absolute gain In antennas, the gain (boost or increase) in a given direction and polarization when compared against an isotropic reference antenna, typically expressed in decibels. If a direction for the antenna is not specified, then radiant energy in all directions is assumed and gain is measured along a selected axis. See gain, isotropic antenna. absolute position Position on an agreed-upon coordinate system, e.g., a system with a point of origin defined as the center of the mass of the Earth (geocentric). absolute scale In its generic sense, any reference or quantitative scale based on an agreed-upon fundamental or unvarying value. Many phenomena are adapted to a scale to help us understand their characteristics and provide an absolute reference from which to chart their relative attributes. Absolute scales are widely used by scientists in their research and descriptive statistics. A well-known example is the absolute temperature scale or Kelvin scale. See absolute zero, Kelvin scale. absolute standard An assigned mass of one unit applied to a specified particle or object so that it can be used as a reference guideline. absolute temperature Temperature measured or calculated with relation to an absolute scale such as the Kelvin scale. See absolute scale, Kelvin scale. absolute URL On the Internet, a Uniform Resource Locator (URL) that describes a complete and direct path to a file, Web page or other Uniform Resource. For example, http://www.4-sights.com/ is an absolute URL. Absolute URLs are useful for upper-level

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files in an account with many cross-referenced files linked together. If within the index.html page at that address, for example, there are references to other pages on the same site, it is common to use relative URLs to name them. It saves time typing in long Web page addresses when coding in HTML, and it means that if the domain name changes from 4-sights.com to newname.com all the subreferences to other pages don’t have to be changed as well, since they may be designated as ../Examples/filename.html rather than http://www.4-sights.com/Examples/filename.html Even if the domain name stays the same, if all the files are moved up one level in the folder hierarchy or down one level, relative URLs don’t necessarily have to be changed, but absolute URLs do. Thus, absolute URLs are best used for the top Uniform Resource in a linked hierarchy and are also commonly used when a URL on another site is referenced, but they are not necessarily the best choice for subfiles or files in subordinate directories that may potentially need to be moved as a block. absolute value A numerical notation and corresponding mathematical concept of the magnitude of a value without respect to its sign. Thus, the numeral -5 without respect to sign is written 5. absolute zero The lowest point in an absolute temperature scale system, zero degrees Kelvin; the low point at which there is thought to be no molecular activity and thus no heat energy, which can also be expressed as -273.15° centigrade or -459.67° Fahrenheit. The Kelvin scale is named after William Thompson (Lord Kelvin). absorption 1. The process by which particles penetrate and are subsumed by matter. 2. Penetration of a substance or wave into another substance. A sponge will absorb water and vegetation will absorb radio waves. 3. Dissipation, as of a wave, into another material as a result of its interaction with the other material. Sometimes this is desirable, as in soundediting studios. See acoustics. 4. The process by which particles entering matter are reduced, or reduced in energy, as a result of interaction with that matter. 5. The reduction of energy that occurs as particles pass through or into another substance as a result of interaction with that substance. In radio wave frequencies, absorption tends to occur more readily at the highest frequencies, e.g., microwaves. Absorption can also be used as a means to add information to a signal. See absorption modulation, scattering. absorption band 1. The radiant energy of a range of electromagnetic waves or frequencies absorbed by a substance. The concept is useful in fiber optic cable fabrication. When Bragg gratings are incorporated into optical fibers to tune them to certain frequency ranges, the pattern is incorporated into the fiber with lasers corresponding to the absorption band of the doped fiber. 2. Depending upon the matter in which absorption occurs, a region of electromagnetic frequencies wherein the absorption coefficient reaches a relative maximum. See absorption coefficient. absorption coefficient A measure of the fraction of electromagnetic energy (e.g., light) absorbed per unit distance in a medium. This may be used to express

attenuation within a medium. The absorption coefficient + scattering coefficient = attenuation coefficient. See absorption index. absorption current Current flowing into or out of a capacitor after its initial charge or discharge. absorption fading Slow fading of transmission waves due to various absorption factors along the path. Complete fading or significant dissipation is known as absorption loss. Depending upon the transmission medium, degree of loss is sometimes expressed in terms of decibels over distance. absorption index A measure of the fraction of electromagnetic energy per unit distance at a given wavelength absorbed in a medium of a given refractive index. Thus, it is a more contextual measure than absorption coefficient that is useful for studying and describing transmission characteristics such as ionospheric absorption. absorption loss The portion of a transmission that is lost due to interaction with another material through partial reflection or complete absorption into the material. This interaction may cause the conversion of energy into other forms, such as heat. absorption modulation A means of modulating the amplitude of a wave, such as a radio carrier wave, by absorbing the carrier power using a variable-impedance device. See amplitude modulation. absorption wavemeter An instrument for measuring frequency or wavelength and sometimes the amplitude of the harmonics of that frequency by absorbing energy from the circuit being tested. When absorption is at its maximum, the wavemeter is tuned to the corresponding frequency of the circuit. This instrument is often used in conjunction with antenna systems. Abstract Machine Notation AMN. A language for specifying and designing software systems of relevance to abstract machines (virtual robots could be considered a type of abstract machine). See B-Technologies. abstract syntax A means of specifying notational rules independently of the encoding used to represent the information. This is useful for defining and developing systems that may be implemented or expanded without foreknowledge of the final configuration of the system or by personnel other than those specifying the initial layers of the system. Abstract syntax is often used in open architectures and object-oriented environments. See Abstract Syntax Notation One. Abstract Syntax Notation One ASN.1. A data definition notation system defined in 1988 as ISO X.208, superseding CCITT Recommendation X.409. ASN.1 provides flexibility and extensibility and supports the definition of a variety of basic and complex data types. ASN.1 grew out of a need for a way to relate abstract and transfer syntaxes that were emerging in the early 1980s, in a machine- and application-independent manner. Open Systems Interconnection (OSI) uses ASN.1 to specify abstract objects to facilitate the process of defining higher level layers without foreknowledge of specific lower layer

objects that might later be incorporated into the system. ABT See advanced broadcast television. abuse numbers A database of phone numbers known to be inappropriate for outgoing calls (i.e., numbers not associated with typical business transactions). Some venders provide an option to track and highlight calls to specified abuse numbers so they can be readily identified on billing statements. ABX See Advanced Branch Exchange. AC 1. See Authentication Center. 2. See alternating current. AC biasing In recording processes, a technique of adding a high frequency to aid in linearizing the recording head. AC powered phone Most small residential phones draw current from the phone line, but if the phone has extra features, such as electronic displays and speakerphones, or if it is a multiline business phone system, then dedicated alternating current (AC) from a wall socket is generally passed through a transformer to supply additional power to the phone. Battery systems also exist, typically for backup power or to hold stored settings in case the AC source fails. Private branch phone systems can consume a significant amount of power if many calls are being processed and may require power from both the phone switching cabinet (through the line) and from an AC power source serving the phone console. AC ripple Undesired modulation in an alternating current (AC) circuit. Filtering may be employed to reduce or eliminate ripple. AC to DC converter A device for converting alternating current (AC) to direct current (DC). The current that comes from most wall sockets is AC current, but many devices including answering machines, feature phones, modems, etc. require DC current and will include a converter attached to the power cord or incorporated into the device. It is unwise to interchange these power converters, as they have widely varying specifications. Most will list the voltage and amperage on the converter, and some will list the corresponding voltage and amperage on the device itself (usually on the underside). Installation of incorrect converter cords can damage sensitive electronic devices. If the device is NOT labeled, it is prudent to mark it as soon as you take it out of the box, with a felt pen or label, so that if the converter and the device get separated from one another, you can correctly match them again. AC13 A British private telephone signaling system. See SSAC13. AC15 1. A British private telephone signaling system. See SSAC15. 2. A model of guitar amp used by the Beatles. AC/WPBX Advanced Cordless/Wireless Private Branch Exchange. ACA 1. See American Communication Association. 2. See Australian Communications Authority. 3. See Automatic Circuit Assurance. AcademNet A Russian academic/research network. http://www.academnet.magadan.ru/

Academic Computing Research Facility Network ACRFNET. A wide-area network connecting research facilities and laboratories across the U.S. Academy of Motion Picture Arts and Sciences AMPAS. A professional, honorary organization composed of more than 6,000 professionals in the motion picture industry. It was founded as a nonprofit corporation in May 1927. Membership is by invitation of the Board of Governors to individuals with significant achievements. Life members are designated by a unanimous vote of the Board of Governors. AMPAS supports and advances the arts and science of motion pictures and recognizes outstanding contributions to the industry through various programs, especially through Academy Awards. With the increase in Internet content delivered in multimedia formats and with increased digital distribution of motion picture products (e.g., DVD), the film industry will likely have a strong influence on the future form and content of information transmitted through telecommunications technologies. Already, as of 2001, the computer games industry and the motion picture industry had begun to significantly overlap. http://www.oscar.org/academy/ ACAR aluminum conductor alloy-reinforced. See ACSR. ACARD 1. Advisory Council for Applied Research and Development. U.K. advisory organization superseded in 1987 by ACOST. See ACOST. 2. Acquisition Card Program. ACAT See Additional Cooperative Acceptance Testing. ACATS See Advisory Committee on Advanced Television Service. ACB 1. Annoyance Call Bureau. 2. Architecture Control Board. 3. ATM Cell Bus. 4. automatic callback. Accademia del Cimento A group consisting of Florentine experimenters, founded in 1657 by the students of Galileo, dedicated to carrying on scientific study. Based partly on the writings of W. Gilbert, the participants carried out important early experiments in magnetism and contributed the use of the pendulum as a tool for studying the attractive properties of materials. See barometer. Accelar routing switch A commercial switcher/ router device from Bay Networks that makes switching decisions based on Internet Protocol (IP) addresses embedded in the local area network (LAN) switch hardware, without proprietary protocols or appended bits. See IP switching. accelerated aging, accelerated life test A design and diagnostic technique that involves subjecting a process, material, or mechanism to short-term conditions that simulate long-term use and environmental influences. Accelerated conditions simulate factors such as weather, movement, mechanical stress, chemical exposure, use, etc. Accelerated Graphics Port AGP. A dedicated graphics video slot incorporated into motherboards

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or PC interface cards that supports Intel AGP specifications. AGP can access system memory in conjunction with a dedicated graphics frame buffer. AGP supports several modes at different clock speeds. This standard is superseding older video formats like PCI buses that may be incompatible with devices increasing in popularity, such as DVD. accelerating electrode A device in an electron tube, such as a cathode-ray tube, that increases the velocity of the electron beam. acceleration The expression of a change in velocity over time. Acceleration is commonly expressed in meters per second per second. An international standard value for acceleration due to gravity on a free-falling object in a vacuum has been established as 9.807 meters per second per second. acceleration voltage In a cathode-ray tube, the accelerating potential which controls the average velocity of electrons directed toward the imaging surface from an electron gun. The voltages are tuned in conjunction with the magnetic coil through which the electrons pass to create the sweep and image frames that help build the picture on the tube. accelerator A system, process, chemical, organic substance, or device that acts on something to speed it up. Accelerators are used in many areas including, but not limited to, studies of elementary particles, chemical reactions, transmission circuits, and computer systems. accelerator board, accelerator card A peripheral card designed to fit into a computer slot that increases the speed of the system, usually by increasing the CPU speed, or by taking over some of the more demanding of the CPU’s functions, such as graphics manipulations. Games players love these. accentuation 1. Intensification, emphasis. 2. In transmissions, the emphasis of a particular channel or frequency, often to the exclusion of others. Accentuation is found in the high frequencies in frequency-modulated (FM) transmitters. Acceptable Use Policy AUP. A license or purchase agreement setting out limitations, restrictions, and acceptable uses which are binding to the purchaser or receiver. For example, a number of freely distributed network software programs stipulate that they may not be used or sold for commercial purposes. acceptance angle 1. In microphone acoustics, a conical region at the front area of the microphone where the sound is effectively captured. 2. In fiber optic cable transmissions, an angle calculated with respect to the fiber’s axis to be effective in ‘capturing’ the incoming light rays and propagating them along the fiber when coupled into optical fiber bound modes. A laser beam entering the fiber at an angle that is greater than this conical acceptance angle is coupled into unbound modes. The acceptance angle is related to the diameter of the fiber channel and the cladding layer (the material that surrounds the fiber core). Acceptance angles vary, but for commercial plastic optical fiber, it is generally around 58°, for glass it may be similar to plastic or perhaps as high as 82°. Light guides made from quartz have smaller

acceptance angles, which are dependent upon the fiber bundle length and the wavelengths being used, usually about half of that of a plastic fiber. acceptance period A period, usually of a few weeks, during which a product or service is evaluated by the receiver as to its conformance to the agreed-upon specifications. It is more commonly a stipulation of custom installations than of off-the-shelf products. Acceptance differs from a warranty in that it applies mainly to initial configuration during the ramp-up or installation period, whereas a warranty may cover other factors and last several months or years after purchase and installation are complete. acceptance test A test, which usually follows installation, that demonstrates that the product or services purchased conform to the agreed-upon specifications. An acceptance test may be contractually required by the purchaser before making final payments on the purchase. access 1. n. The point through which a circuit or communications device is entered, or the point at which the communications process is entered and initiated. 2. v. To gain entry into a circuit or communications device. Phones are generally accessed by dialing a number, although an access code may be required on a secure system. Dialing “9” first to obtain an outside line is a common access procedure. Account codes are sometimes used to assign billing to specific departments or individuals. Access codes may be used by installation or maintenance technicians to initiate services or procedures not available to the subscriber. Secured computer systems are accessed by logging in with or without a password. See access code. access arm The positioning mechanism that supports a read/write head for reading from or writing to magnetic or optical storage media. On a computer hard drive, the access arm moves across the disk and positions the head directly to within thousandths of an inch of the area of magnetic particles to be read (or written). See seek time. access carrier An interconnect agreement through which a carrier can gain access to the services and network facilities of another carrier. access charge 1. The charge made for access to a computer system or network. An access charge may be assessed on a periodic basis or per time or volume of use. Internet Service Providers typically charge flat monthly rates, although some will assess extra charges for storage, peak-time connects, access to chat areas, or special online services. 2. The Modified Final Judgment (MFJ) which broke up the Bell system included the rationale and stipulation that users should be able to choose a long-distance carrier, thus changing the way in which long-distance access charges were structured. Compensatory restructuring resulted in two categories of access charges: Customer Access Line Charges (CALCs), and Carrier Access Charges (CACs). The first applies to local phone loops and varies according to the subscriber (residential or business) and the characteristics of the service. The latter applies to service providers connecting to the local exchange

circuits and varies according to factors such as distance. Adjustments and modifications in order to implement the many changes have subsequently occurred. See Telecommunications Act of 1996. access code One or more characters that must be entered in order to obtain use authorization to a system such as a phone or network. Access codes are generally used for security, monitoring, and billing purposes. They can also be used by technicians to set up a system for use with specified features and, more recently, to program a telephone system. Some typical telephone access code implementations include (1) dialing codes to access an outside line or to dial a long-distance number (dialing “9” is common), (2) dialing an access code to bill the call to a particular line or department, (3) dialing a code to obtain authorized use on a privileged system. access control 1. The policies, procedures, and system configurations controlling security or utilization of resources. Access control operates on many levels, including building access, system access, applications access, network access, device access, and computer operations access. See access code. 2. A physical or virtual control point, gateway, or other filter or security system that selectively allows data to pass through according to general or specific parameters, which may include priority level, data characteristics, sender, receiver, etc. access control field An informational field in the header of a synchronous multimegabit data service (SMDS) cell which provides access to a shared bus, which in turn provides access to the SMDS network. access control list ACL. A list, table, or database that provides a reference for various levels of security within a system. It can be as simple as a list of names in the hand of a doorway security guard, or as sophisticated as a tiered database of levels of security for different people and processes on a computer network. On bulletin board systems (BBSs), many access control lists include a series of software flags for each user which can be toggled individually by the sysop to control user access to services such as chat, email, doors, downloads, etc. The “twit bit” is a flag that basically labels a user as a “loser,” in BBS parlance. In other words, the twit is someone who has been flagged for limited access because s/he exhibits immature behavior and can’t be trusted with access to any of the powerful features. access control method A system for controlling access to systems, processes, or devices on a network. A variety of general guidelines and specifically defined systems for particular types of networks and protocols have been developed. Access control can be set up “by user,” “by workstation,” “by application,” “by file,” “by network,” or a combination of these, which may be hierarchical. Examples of particular types of access control on specific types of networks include carrier sense multiple access (CSMA) on Ethernet systems and token passing schemes on IBM Token-Ring networks. See Media Access Control.

access coupler A connecting device used between physical network segments, such as fiber optic cable legs, to allow signals to be passed to the next leg. Access couplers are sometimes used in conjunction with relays and amplifiers, depending upon the type of signal and the distance being traversed. access delay In a packet-switched network, a performance measure for polling systems, calculated from the time of arrival of a data packet to the time it is retransmitted. access group A group of accounts or individuals who have specific, defined levels and types of privileges within a system, which may be different from individual privileges and from other groups. For example, on a private branch exchange (PBX), a group of managers may be designated as having access to long-distance or outside lines, whereas a new employee may be assigned to a group with limited privileges until an evaluation period has passed. On a computer network, an access group may have certain read and write file privileges which differ from individual privileges and the privileges of other groups. Thus, they may be permitted to run only certain applications, look at certain directories, etc., according to settings established by the system administrator. access line 1. The physical link between the subscriber box and the local telephone switching center. From the subscriber box to the telephones is considered inside wiring and may be installed by the subscriber or, for a fee, by the phone company. See local loop. 2. In BBSs, the line through which the caller accesses the BBS modem. There may be multiple lines, sometimes with different baud rate capabilities. Historically, BBSs have been accessed through phone lines but, increasingly, BBSs are interfacing with the Internet to provide online access through telnet. 3. In frame relay systems, a communications circuit that connects a frame relay device to a frame relay switch. access link A link. A connection point in a network that enables access to resources on the other side of the link. In Signaling System 7 (SS7) it specifically refers to a dedicated signaling link that is not associated with any particular physical link. access mechanism A device for moving and positioning an access arm, usually on random access read and/or write media. access method Logical guidelines established by International Business Machines (IBM) in the 1960s for input and output access to computing resources, particularly those that are shared, as on local area networks (LANs). By consolidation of instructional sequences in common procedures, functions, and subroutines, the overall structure can be simplified. access module AM. In general, an access module is an included or optional interface that allows transmission lines or peripherals to connect to a main unit such as a computer, a microscope, a milling machine, or a telephony service unit. Depending upon the unit, it may include specific connectors, voltage or data selection switches, and sometimes signal conversion,

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compression or decompression electronics. In microscopy, access modules can allow video recorders, still cameras, or projection devices to be attached. In computing, printers, modems, and other peripherals are commonly connected through peripheral cards, a type of access module. In wireless and wireline services, a mechanism to provide electrical or optical connections with various transmission cable ends (RJ-x jacks, BNC connectors, ST connectors, 25-pin D connectors, etc.) so they can be readily connected to service supply units. Access Network Termination ANT. Typically a device that provides coupling to the user end of the communications line. Depending upon the type of transmissions service, such a device may provide signal splitting, framing and deframing, cell header processing, encryption/decryption services, and other termination/translation functions needed at the subscriber end of the communications circuit. Thus, a cable modem is an example of an ANT device as it provides access to a fiber optic line and termination/translation services for interfacing a personal computer. See access module. access software provider Defined in the Telecommunications Act of 1996, and published by the Federal Communications Commission (FCC), under SUBTITLE A—Telecommunications Services as: “... a provider of software (including client or server software), or enabling tools that do any one or more of the following: (A) filter, screen, allow, or disallow content; (B) pick, choose, analyze, or digest content; or (C) transmit, receive, display, forward, cache, search, subset, organize, reorganize, or translate content.” access tandem AT. A central office telephony switching system that provides distribution services for outgoing or incoming traffic between End Offices. access tandem switches Specific types of switches that are used to connect End Offices to Interexchange Carrier (IXC) switches or to interconnect central office (CO) switches. access time 1. The interval between a signal or instruction to access information or a device, and the time it takes to successfully retrieve that information, or interact with the device. Depending upon the system, the access time may or may not include the time it takes to display the requested information to the user. For example, in a database query on a computer system, the access time may be two seconds to search and retrieve a long list of names and addresses, but it may take twenty additional seconds to fully display all the listings, and the access time may not include the display time or may include the display time for the initial information, but not the time during which the software may be building additional viewable information below a scrolling window. Access time is described in terms of units appropriate to the average time and device involved. For example, access time for a process may be described in CPU clock cycles, for data access on

storage media by seek time in milliseconds or fetching in nanoseconds. 2. In magnetic storage devices, the interval during which the access mechanism, once information is requested, moves across the medium to the desired location and successfully reads the data. access unit AU. 1. In Token-Ring networks, a wiring concentrator that connects the end stations. The AU provides an interface between the Token-Ring router interface and the end stations. Also known as Media Access Unit (MAU). 2. In many X.400-based commercial software applications, the AU works in conjunction with mail servers to provide synchronization between post offices and other services, such as directories, address books, etc. 3. In advanced television (ATV) systems, the AU is a coded representation of a presentation unit. Thus, it may be the coded representation of an audio frame or coded data for an image, including stuffing, up to the point where the next access unit begins. See ATSC Digital Television Standard. access.bus A serial communications bus topology protocol developed jointly in the mid-1980s by Digital Equipment Corporation and Philips Semiconductors, for connecting peripheral devices such as mice, keyboards, card readers, scanners, etc. to computers through a four-wire serial bus. See Universal Serial Bus. Accessible Information on Development Activities AIDA. Formerly known as IDAI, AIDA is a Development Gateway (DG) pilot project which encompasses tens of thousands of individual projects related to the International Development Markup Language (IDML). The DG provides support software and documentation to facilitate the conversion of data into IDML format. See International Development Markup Language. accounting server A software application, sometimes operating from a dedicated, secured computer that monitors network usage, stores the information, and may assess charges for usage based on CPU time, real time, time of day, department, or some other measure appropriate to the type of use. ACCS Automatic Calling Card Service. accuracy 1. Degree of conformity to a stated or observed value considered to be optimal or correct. See calibration. 2. Precision. 3. Degree of freedom from error. AC/DC, AC-DC 1. alternating current/direct current. 2. An electrical appliance that can operate on alternating current (AC) or direct current (DC). 3. Euphemistically used to designate something or someone that operates in two modes or “swings both ways,” especially in alt.xxx USENET discussion lists. ACD See Automatic Call Distribution. acetate A cellulose acetate chemical compound that was once commonly used as a coating for storage media such as audio recordings. This application has been superseded by various types of magnetic storage and compact discs. ACF Advanced Communication Function.

ACG See automatic call gapping. achromatic 1. Uncolored; unmodulated; neutral; black and white; grayscale. 2. In the visual spectrum, lightwaves that are not dispersed or singled out according to a particular wavelength. ACIA asynchronous communications interface adapter. A data formatting device that translates signals between the computer and a peripheral such as a modem. ACK See acknowledge. acknowledge, acknowledgment ACK. A message or signal from the receiver to the sender confirming receipt of data or accurate receipt of data. In handshaking, ACK sometimes also signifies that the receiver is ready for further data. ACK and NACK are commonly used on bidirectional communications systems, in which data can transmit in only one direction at a time. See negative acknowledge. ACL 1. See access control list. 2. Applications Connectivity Link. 3. Association for Computational Linguistics. ACLU See American Civil Liberties Union. aclastic Having the property of not reflecting light. ACM 1. See Association for Computing Machinery. 2. Automatic Call Manager. An administrative and operations system that handles inbound and outbound calls integrated with a database. Telemarketing, teleresearch, and collection agencies make use of these types of systems. 3. Address Complete Message. A call setup message in ATM networking that is returned to indicate that the address signals required for routing the call have been received by the called party. The ACM is sometimes sent in conjunction with other routing messages. ACO 1. Additional Call Offering. 2. alarm cutoff. A switch that suppresses an audible alarm, while not affecting a corresponding visual alarm. ACOnet Austrian Academic Computer Network. An ATM-based Austrian research network funded by the Austrian Ministry of Science, Transport, and Art. ACOnet interconnects about a dozen universities and provides international links to other countries through EBS-Vienna. http://www.aconet.at/ acorn tube A very small vacuum tube named for its squat, rounded shape, which has electrodes leading directly through the glass on several sides. It was developed for use at extremely high frequencies. While most vacuum tubes have been superseded by transistors and other modern electronics, there are still high frequency applications where vacuum tubes are practical. ACOST Advisory Council on Science and Technology. A U.K. organization which superseded ACARD in 1987, ACOST is a government advisory and coordinating body on policy and research. acoustic Relating to sound phenomena, the science of sound, as well as biological structures and nonbiological apparatus for generating, conveying, controlling, or apprehending sound. In music, an acoustic instrument doesn’t typically have an electronic pickup because it depends upon its physical structure and the surrounding medium to create and

convey the desired sounds at the desired intensity. acoustic coupler Any device that is designed to interface with an audio sending and/or receiving circuit to provide amplification or conversion between analog and digital audio signals. The coupler is usually designed to exclude extraneous noise that could interfere with a signal and may be a self-contained unit or a peripheral interfaced with another system. Acoustic couplers that resemble large suction cups (sometimes called suction cup modems) were incorporated into early modems to provide a way to interface telephone handsets with computers. The coupler was designed so that the outbound modem signal played into the mouthpiece microphone and the inbound signal played from the earpiece speaker into the modem. See acoustic modem. acoustic echo canceller AEC. In many telephony devices, the microphone is only inches away from the speaker. Thus, sounds from the speaker can reach the microphone and interfere with the clarity of communications. Unpleasant screeching, echoes, or howling may occur. An acoustic echo canceller reduces or eliminates this unwanted interference. Echo cancellation is accomplished in a number of ways with one or more electronic filters placed in various positions in the signal path, depending upon the system. In some advanced systems, ambient background sounds are also filtered and ‘cancelled’ to improve the clarity of the audio signal. acoustic feedback See feedback. acoustic model In software applications, a means to apprehend and interpret sound input, such as speech, by breaking it down into smaller units and then using those together to build an aural representation or interpretation of input combined from these units into larger words and speech patterns. Early attempts at speech recognition were hit-andmiss, and very person-specific, but new programs can transcribe speech into text with a useful degree of accuracy up to about 70 words per minute. Computerized speech used to be characterized by very flat, mechanized sounds but, with faster processors and better methods and sound samples, natural sounding voices can be generated. Many automated phone voice applications now use speech generation for messages, queries, and instructions. See phonemes, sampling, speech recognition. acoustic modem A modulating/demodulating computer peripheral that converts the digital signals created by a computer into audible tones that can be coupled with the transmitting end of a telephone handset or other audio transmissions device so they can be sent through an analog phone line. The device then converts the audible tones generated by the other end of the transmission back into digital signals for the computer to interpret. The modem is usually attached to the computer by means of an RS232 (EIA-232) interface, although some acoustic modems designed for the early Apple computers were connected through the joystick port. Acoustic 300-baud modems were prevalent on personal computer systems in the late 1970s. These were gradually superseded by direct connect modems in

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the 1980s. Acoustic modems have many limitations. They tend to be bulky, as they need sufficient shielding around the transmitting and receiving electronics to prevent the tones from crossing over and interfering with one another. They are subject to interference from external noises. They work well only with old-style phone handsets. The newer, flatter ones do not get sufficient shielding or contact with the couplers to transmit clean tones, and they do not generally employ any sophisticated data compression capabilities, resulting in slow transmission speeds. See acoustic coupler, direct connect modem.

Acoustic couplers were designed so that the handset of a telephone could rest in the rubber sound shields. Since the sizes and shapes of handsets began to vary at about the same time that acoustic modems were distributed, the physical connection was often less than satisfactory and stray room noises could interfere with transmission. This type of coupler has been superseded by direct connect modems and is now useful only in specialized situations (as when using a payphone).

acoustic telegraph Messages conveyed by sound, such as bells ringing specific tones or sequences (still used in many European churches), drumbeats, horns, or shouts that are passed from one person to the next (still used on large sailing vessels, railroad lines, or other areas where other means of distance communication are not available). In the early days of electrical telegraphs, a number of inventors were seeking ways to use tones to convey more information over a single line than was possible with the simple on/off system that was gaining widespread use. Experiments in trying to send tones led to the invention of the telephone, and so the technology leap-frogged over the acoustic telegraph. Basic telegraphic systems were used for a long time concurrently with the evolution of telephones. acoustic velocity (Symbol - a) The speed of sound (technically, velocity is the rate of motion in a direction). A measure of acoustic velocity is valuable in many communications fields and also facilitates the determination of other measures such as distance or the ‘thickness’ or permeability of a medium or particulate environment. acoustical Doppler effect A characteristic of a sound when there is motion that causes the object emitting the sound to be moving farther away or closer in relation to the listener. The perceived pitch of the sound changes from the pitch that is being emitted. As an

example, imagine standing by a railroad track when a train goes by, blowing its whistle. Although the effect is not dependent upon the pitch of the whistle being constant, imagine that the train whistle is a constant note at one pitch. As the train moves toward the listener, the perceived pitch of the whistle rises, and as it passes and moves away from the listener, it falls. This effect occurs due to the characteristics of the sound waves traveling through air relative to the rate of change and the distance of the wave from the listener. It can readily be heard on musical instruments that short strings vibrate at a higher pitch than long strings of the same thickness and materials. Now imagine ripples in a pond from a stone thrown in the center. The ripples close to the source are higher and those farther from the stone are shallower; that is, the amplitude of the wave diminishes as it moves away from the source. Similarly, as the train moves through the air and is oriented differently with respect to the listener, the characteristics of the sound waves change, resulting in different pitches reaching the ear. Acoustical Society of America ASA. A scientific society founded in 1928 after an initial meeting at the Bell Telephone Laboratories in New York. It began publication of its professional journal in 1929. ASA merged with three other societies in 1931 to form the American Institute of Physics. ASA has been involved in research, development, promotion, and standardization efforts in the field of acoustics. http://asa.aip.org/ acoustics 1. The art and science of sound production, transmission, and reception. 2. The sound-carrying capacity, in terms of quality, fidelity, and loudness, of an environment such as a concert hall or recording studio. See anechoic. acoustics, architectural The art and science of the propagation of sound in enclosed structures (concert halls, museums, classrooms, auditoriums, etc.) or circumscribed environments (amphitheaters, stadiums, landscaped areas such as parks, etc.). Reverberant sound fields are created, studied, and adjusted to suit the needs of the structure. Concert halls and theaters are designed to carry the fullness and dynamic ranges of music or voice to as many listeners as possible within the building, while still minimizing noise that might disturb activities outside the building. acoustics, engineering The art and science of sound control in electronic structures, including amplification, propagation, dampening, and the harnessing of sound to carry information, as in data and broadcast transmissions. acoustics, musical The art and science of sound control and propagation through acoustical and electronic instruments (many electronic sounds are created by digitizing the sounds of acoustical instruments). It involves the careful study of sound in relation to materials, shapes, resins (which help wood to retain its resilience and vibratory qualities), sound transfer through sound boards and bridges, and much more. Much of the history of musical acoustics is based upon the subjective observations of individuals with good craftsmanship and good musical ears,

but in recent years scientific instruments have given us additional tools with which to craft instruments and propagate musical sounds. See patch, sampling. acousto-optic modulation A technique which can be used quite effectively for color control, dimming, and blanking in laser light beams. The beam is shone through an acousto-optic crystal. The modulation is applied with electrical impulses to the crystal to influence the intensity of the beam. Three beams can be used, red, green, and blue, as in a cathode-ray tube, to provide color modulation. This is known as polychromatic acousto-optic modulation. Other applications of acousto-optics can be used to tune filters. See modulation. ACP See activity concentration point. acquisition 1. The gathering, receipt, and possession of data. 2. The process of orienting toward and acquiring data, that is, seeking a source; setting up the necessary protocols; aiming an aerial; scanning network inputs or broadcast frequencies; and receiving the transmission. acquisition and tracking A data detection or receiving system such as radar that seeks out a signal, locks in on it, and orients toward the source of the signal while receiving. acquisition time The time required to seek out and lock on to the source of the desired signal. Commonly used in microwave transmissions such as radar and satellite communications. ACR 1. abandon call and retry. 2. allowed cell rate. In ATM, an available bit rate (ABR) service parameter that describes the current allowable sending rate in cells per second. See cell rate. 3. attenuation to crosstalk ratio. ACRFNET See Academic Computing Research Facility Network. Acrobat An Adobe Systems commercial page layout software application used to create documents containing text and graphics. The Acrobat Distiller takes PostScript code and interprets it into objects that can be displayed on a variety of platforms supporting the freely available Acrobat Reader program. The Acrobat Portable Document File (PDF) is popularly used to distribute documents on the Web. Since it retains font/image formating, the PDF files can be displayed or printed in professional layout formats. PDF is also becoming popular for forms handling, since the files can be designed to be selectively edited by a user. Thus, they are useful for electronic, paperless processing of government forms such as business license applications, for example. In addition to software downloadable from the Net, a number of word processing and desktop publishing programs will export Acrobat-distilled PDF files and the resulting files may be several times smaller than the original, dending upon the contents. Distilled PDFs typically use a .pdf file name extension. See Portable Document Format. acronym A word that is formed by taking the first letter or letters from each of a number of successive words in a phrase or compound term. An acronym is a special form of abbreviation that has wordlike

cadence and sound properties and may, because of its ease of pronunciation and mnemonic qualities, eventually become part of the general vocabulary. Examples include scuba (self-contained underwater breathing apparatus), radar (radio detecting and ranging), and BASIC (Beginner’s All Purpose Instruction Code). ACS 1. See Advanced Communication System. 2. See Australian Computer Society. 3. automatic call sequencer. A simple form of automated phone call handler which hands off calls to available agents. ACSE See Association Control Service Element. ACSL See Advanced Continuous Simulation Language. ACSnet The Australian Computer Society national computer network, which maintains links to national networks in other countries. There are close ties between the Australian government and the ACS, with the ACS providing information and critical debate to computing policies in government and, further, representing Australia in the International Federation for Information Processing (IFIP). ACSR aluminum conductor steel-reinforced. Although aluminum is light and a good conductor, aluminum cables with steel cores tend to be bulkier and heavier than copper. ACT 1. See Applied Computer Telephony. 2. See Authorization Code Table. ACTA See America’s Carriers Telecommunications Association. ACTAS See Alliance of Computer-Based Telephony Application Suppliers. actinism A property of radiant energy in the X-ray, ultraviolet, and visible parts of the spectrum to promote chemical changes. ACTIUS See Association of Computer Telephone Integration Users and Suppliers. activation fee, setup fee In many communications services, there is an activation or setup fee associated with starting a new account. This fee covers the service provider’s administrative costs of installing the account and providing the new user with operating instructions, passwords, etc. Sometimes providers will waive activation fees in order to attract new subscribers. active communications satellite A communications satellite that employs transponders (a type of repeater) or other means of amplifying and forwarding (relaying) a signal, usually with the frequencies shifted so the uplink and downlink transmissions do not interfere with one another. Unlike the larger passive satellites launched in the 1960s, newer active satellites can amplify a signal without the extra bulk needed in earlier systems. Virtually all current satellites are active. active jamming The deliberate interposition of signals intended to disrupt communications such as radio or radar transmissions. active line A communications channel that is currently being used. While no human communication may be taking place, if it is a data line, there may nevertheless be meaningful activity on the line, such

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as computer processes interacting with one another. active lines In a television image, those lines that are visible to the viewer at any one time. Since a frame consists of many sweeps of the beam, only some of the possible lines may be seen by the viewer at any one time, but because the transition is so fast, the image is perceived as continuous. Those lines that are not active are blanked. See blanking, frame, scan line. active matrix display Usually a liquid crystal display (LCD), active matrix is a means of brightening an electronic display by adding transistors to individual elements to maintain the image between successive scans or refreshes of the screen. Thus, the screen appears to refresh more quickly and gives a crisper, more contrasting appearance that aids in legibility. Color laptops frequently incorporate this technology and active matrix screens are gradually replacing passive matrix screens. ActiveX Descended from Microsoft’s Object Linking and Embedding (OLE) but intended to run over the Internet and to compete with Sun’s Java, ActiveX provides a means to utilize animation, sound, and interactive elements, for example, in Web documents. ActiveX components are somewhat similar to browser plugins, or Java applets. See ActiveX Controls, Java. ActiveX Controls Microsoft ActiveX controls are interactive objects created individually by developers. They can be embedded in various Web-related applications. ActiveX controls can be programmed in a variety of languages, including Visual BASIC, Java, or C++. They can then be readily shared with other programmers. A number of commercial vendors of authoring and page layout display systems have incorporated ActiveX Controls into their software. activity concentration point ACP. A place in a network at which there is a high traffic load, in other words, a focal point for higher activity than is ordinarily found in other locations in the system, as in computer network servers. activity reports Automated usage logs that are generated by computing devices and usually accessible through a file or printout. Activity reports can provide information about times and types of use, errors, and sometimes transmitter/recipient information. Activity reports are commonly available on facsimile machines, high-end printers, and some electronic photocopiers. There are disadvantages to the glut of information and statistics that can quickly and easily be generated by electronic systems; there aren’t sufficient hours in the day to evaluate all of it, nor is there sufficient storage space to keep hardcopy versions, and there is the danger of turning people into human robots, doing the drudge work of feeding information into computers or trying to evaluate the output all the time rather than using them to increase free time and quality of life. Some corporations now require their employees to wear sensors that monitor and record all their movements and activities within the premises. Some individuals are understandably concerned about this

excess of detailed electronic monitoring of employee actions and its implications for privacy and abuse. They are further concerned about what happens to these reports, who can see them once the employee has left the company, and whether employees have regular opportunities to assess their accuracy and interpretation. ACTRIS See Association for Cooperation in Telecommunications Research in Switzerland. ACTS 1. See Advanced Communications Technologies and Services. 2. Advanced Communications Technology Satellite. 3. See Association of Competitive Telecommunications Suppliers. 4. Automatic Coin Telephone Service. An automated system for handling payphone traffic, it directs the user on how much money to insert, handles calling card calls, provides diagnostic and tuning information to technicians, etc. In areas without ACTS service, calls are handled by TSPS operators.

ACTS, the Advanced Communications Technology Satellite, was a project of the late 1980s and 1990s in which the Space Shuttle was used to deploy a communications satellite with large reflective surfaces. Top left: ACTS relationship to the shuttle and the Earth, illustrated in 1987. Top right: ACTS in Earth orbit over the ocean after release by the Space Shuttle Discovery in the early 1990s. Bottom: Advanced Communications Technology Satellite (ACTS) parabolic antennas. [NASA/GRC image; NASA/JSC image detail; NASA/GRC image, August 1996.]

Actual Measured Loss AML. A telephony system evaluation statistic used to express traffic management efficiency. It is sometimes compared to Expected Measured Loss (EML) to provide a measure

of deviation from desired or mandated service efficiency levels. actuator A mechanical or electromechanical positioning mechanism used to aim an antenna so it can remotely or automatically scan the arc of a satellite. ACUTA See Association of College and University Telecommunications Administrators. AD See administrative domain. ADA 1. A high level, structured, data-typed programming language, somewhat like an extended Pascal, developed by and mandated within the Department of Defense, but not popular outside of this circle. It has been criticized by some programmers as being cumbersome and difficult to use. The language is named after Ada Lovelace, the technically astute daughter of Lord Byron. There have since been variations on ADA, including ADA++, which in turn has been superseded by ADA 95. See Lovelace, Ada. 2. Average Delay to Abandon. The average length of call duration for a caller held in a queue who hangs up before being connected with the callee. ADACC Automatic Directory Assistance Call Completion. Adams, Scott Founder of Adventure International in 1978, Adams created a microcomputer games empire by developing and marketing a series of text adventure games that were wildly popular in the early 1980s. Over the last twenty years, the availability of entertainment products like the Scott Adams games has strongly influenced users to purchase computers and to upgrade graphics, sound, and network cards for multiplayer games. adapter A device to connect one type of component, system or connector to other components, systems, or connectors to provide physical and electronic compatibility on each end of the connection. An adapter is used when the two connections do not naturally couple with one another. Related to adapters are connectors, which are most often small passive devices, simply passing information or current through, while adapters tend to be combined with active, signal-processing or enhancing components, or with gender changers, extenders, or splitters. See adaptor, adopter. adapter card See peripheral card. adaptive antenna array A series of antennas grouped and arranged so the combination of antennas provides enhanced reception or transmission over individual antennas. An antenna array can be configured to monitor signals or signal conditions or to use input from other sources, such as computers, and to adapt to them as appropriate. For example, in a directional antenna array, if the signal shifts due to movement on the part of the sending antenna, the array may be able to move or swivel to optimize the signal level (as in elliptical satellite orbit communications). For wireless communications, adaptive arrays with horizontal extensions are being installed on existing cell towers to direct beams towards mobile terminals in order to increase capacity. Sector antennas may sometimes be housed in the same physical structure as adaptive array antennas

to reduce the footprint of the assemblage, but care must be taken to arrange them so they do not cause distortion. See Butler antenna; antenna, smart. adaptive communication A communications system that incorporates intelligence and feedback mechanisms to optimize signal or data transfer. In telephony, a cordless phone may automatically switch channels to find a better signal if the current one deteriorates. In the telephone switching system, a phone call may be routed through another trunk if congestion is detected. In computer network systems, the system may reroute packets if one of the hops in a journey changes or becomes unavailable. adaptive differential pulse code modulation ADPCM. An ITU-T standard for voice digitization and compression in which sample rate speeds are related to the variation in the samples, thus using fewer bits than pulse code modulation (PCM), which is commonly used in digital voice coding, if the sample speeds are slow. An analog voice can be carried on an up-to-32 Kbps channel. ADPCM can be used over digital networks such as frame relay systems. adaptive routing A system of routing in networks that utilizes intelligence in addition to information in routing tables, to establish best routes, fastest routes, or alternate routes in the case of obstructions in the usual paths. See hop-by-hop routing. adaptor A person who physically or otherwise directly modifies a system, component, or instrument to perform a different function or to perform a function or set of functions in a different way. See adapter, adopter. ADAS See Automated Directory Assistance Service. ADB See Apple Desktop Bus. ADC, A/DC 1. analog-to-digital converter. A technology that is widespread in telecommunications and increasingly important for wideband wireless lowvoltage devices. 2. automated/automatic data collection. ADC Telecommunications A global supplier of telecommunications quality assurance and testing products, founded in 1935. ADCA 1. Aerospace Department Chairman’s Association. 2. See Automatic Data Capture Association. ADCCP Advanced Data Communication Control Procedures. A bit-oriented, ANSI-standard communications protocol related to High Level Data Link Control (HDLC). ADCIS 1. Aged & Disability Care Information Service. 2. analog/digital CMOS ICs. 3. See Association for the Development of Computer-Based Instruction. Adcock antenna A transmitting/receiving antenna with two or more vertical conductors arranged so that the pickup is minimized in the horizontal wires. Adcock antennas can be arranged in arrays to provide directional transmitting/receiving; one such array system resembles the configuration of the number five on a throwing die. ADCU Association of Data Communications Users. add-on 1. More commonly known as three-way

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calling or add-on conference, a telephone subscriber feature that enables the connection of a third phone into an ongoing conversation. It is usually accomplished by putting the conversation on hold, calling the third party, and returning to the initial call with the third party linked into the call. 2. See applications processors, peripheral device. ADDACC See Automated Directory Assistance Call Completion. additive increase rate factor AIRF. In ATM, an available bit rate (ABR) service parameter for controlling cell transmission rate increases is called the additive increase rate (AIR). AIR is signaled as the additive increase rate factor (AIRF) where AIRF equals AIR times the maximum number of cells permitted for each forward RM-cell (Nrm) divided by the peak cell rate (PCR). Additional Cooperative Acceptance Testing ACAT. A method of telephone testing in which a technician at the central office works in cooperation with a carrier-provided technician at the carrier premises to test line integrity conditions such as noise, jitter, distortion, signal-to-noise ratios, and other typical transmission characteristics and possible sources of interference in a new installation. address A locator, usually in the form of a number, of a position in memory or other storage medium, such as a hard drive or floppy diskette. A telephone number is a unique address on a phone system, used to establish a connection. An email address is a unique identifier used in the transmission, receipt, and storage of electronic messages over a network. There are directories on the Web that store the email addresses of specific individuals or companies on the Internet, or that can retrieve a name and address, given a specific email address. The individuals whose addresses are listed are not necessarily aware of the fact. See address, MAC; ego surfing; electronic mail. address, Internet An Internet address, or Internet Protocol (IP) number, is a unique host name identifier on the Internet. IP addresses can be expressed as numbers, 255.0.0.0, or as a full DNS name, www.4-sights.com. A registration process is required to obtain a unique address on the Internet. See Domain Name Service, InterNIC. address, MAC A Media Access Control (MAC) address is a device address on a network. See MAC address, Media Access Control. address filtering Decision-making on a network as to which data packets will be permitted to continue. For example, a filter evaluates the source and destination Media Access Control (MAC) address and compares it against any specific restrictions or instructions that have been set up for the system. On a general level, address filtering can be used to keep out messages from unwanted sources, such as bulk commercial mail senders, and to reject messages to local destinations that may no longer exist, or that may be restricted. See firewall. address resolution AR. On the Internet and local area networks (LANs) using ATM, the conversion

of an Internet Protocol (IP) address or local address into its corresponding geographical/physical address. It may be done in stages, through a discovery process, with the layer address being sought first and other parts of the address, such as a Media Access Control (MAC) address, being resolved at a more local level. This hierarchical approach can streamline the amount of information that needs to be processed and carried initially and provides the flexibility to reorganize machines, switches, and routers at the local network level. Address resolution is done by broadcasting from the sender to a number of nodes at the general destination and then responding to a specific destination, once information has been sent back from the appropriate end station to show where it is. See address, Address Resolution Protocol, MAC address, Media Access Control. Address Resolution Protocol ARP. A protocol used to systematically, dynamically discover the low level physical network system that corresponds to an Internet Protocol (IP) address for a given host. ARP is used over physical networks that can handle broadcast packets (not all networks have a broadcast layer) to all the hosts, or the relevant hosts, on the system. By broadcasting to a general destination and then evaluating the responses by the local hosts, the specific address can be discovered and resolved without all the information about all possible destinations being stored at the originating system. See address, address resolution, MAC address, RFC 826. address space 1. There are a number of definitions for address space, that is data storage locations, as they relate to computer memory. Computer operating systems handle addressing in various ways. For example, some OSs cannot put a large block of information across noncontiguous segments of available memory. In these systems, if the system has been running for some time, with many processes writing to memory, they may “bog down” due to memory fragmentation. Others can map the memory and use the noncontiguous spaces provided they are not too small or too numerous. Systems also vary in their ability to clean up memory once an application has been closed down, or a process completed, and may not release the memory to other programs or processes. On these systems, it may be necessary to reboot at intervals to clean up the system. Philosophies differ. Some feel the OS should clean up the system, others feel the programmer responsible for the application should clean up when the application is terminated. The second, cooperative system may not work as well in environments where software is unnaturally terminated (aborted rather than closed down normally). Address space is also related to hardware configuration. Some systems can address memory only in chunks of limited sizes, up to a fixed amount. Others can dynamically map the memory space up to relatively large sizes (e.g., 256 Mbytes of RAM). Address space on specialized devices, such as digital cameras, may be limited to the size of a memory storage card or internal components. 2. The total amount of available memory that may be

directly used, which may be broken up by other data or across memory segments. 3. A single contiguous segment of memory that may be directly used. address translation gateway ATG. A Cisco Systems DECnet routing software function for routing multiple, independent DECnet networks. ATG enables the user to establish address translation for selected network nodes. addressable point On a computer display, any point that can be directly written or read by the system. Unknown to many consumers, many of the older microcomputer systems could not directly read or write every point on a display. Some could address only odd or even points in the horizontal or vertical directions, limiting the power and flexibility of graphics imaging and painting programs. For example, some systems could draw lines (and thus the edges of windows and dialog boxes) only on every other line, so programmers could not precisely position the boxes and had to make the widths divisible by two (or one side would disappear). Systems with these limitations are no longer common. addressee The intended recipient of a written message or data communication. See email. addressing In computer programming and operations, a means of keeping track of stored information so it can be accessed in the future as needed. ADF 1. See automatic direction finder. 2. automatic document feeder. A built-in or optional device on a printer, photocopy machine, facsimile machine, or scanner that holds a sheaf of paper, usually unattached single sheets, and feeds these pages individually through the machine. Some machines have a series of paper trays for different sizes or types of paper and can cycle through the trays as needed or automatically select the paper size. ADIO, A/D I/O abbrev. analog/digital input/output. adjacent Near; next to; directly before or after; beside. Having a shared border, contiguous with. If something is adjacent, then no other device or process of the same kind is between it and that to which it is adjacent. For physical devices, the adjacent entities may or may not be physically touching or connected by cables or other means. adjacent channel interference Due to demand, broadcast spectrums are subdivided into narrow bands in order to accommodate many channels. When broadcast channels are adjacent, the signal from one may interfere with the ones close by. Most people have experienced this type of interference in AM car radios; as they move farther from the signal of the current selected station, adjacent stations (or stronger stations) may be heard over the desired station. For this reason, some of the better radios are equipped with adjacent channel selectivity circuitry which rejects the transmissions of adjacent channels to provide cleaner reception. adjunct 1. Something that is additional to, or joined to, something else, but that is not essentially part of it. 2. Assistant, aide, associate. 3. A peripheral device that enhances a system, without being essential to its basic operation, such as a computer micro-

phone, joystick (gamers would argue that this is essential), modem, telephone headset, etc. Adjunct System Application Interface ASAI. A set of AT&T technical specifications for the controlling of private branch exchange (PBX) telephone systems by computers. ADK application-definable keys. Keys that can be assigned to perform an application-specific function or to insert or display a menu, or symbol, or other feature for quick access, as desired by the user. ADM 1. adaptive-delta modulation. 2. add/drop multiplexer. administrative domain AD. The group of network hosts, switches, and routers and their interconnections that are managed by a specified administrative authority, such as a system administrator on a small network or a network control center for a larger network. Administrative Operating Company Number AOCN. In the telephone industry, AOCN providers handle a variety of national call routing and rating databases and services to telephone companies. AOCNs may also obtain NXX and other telephone codes on behalf of their clients. Individual Operating Company Numbers (OCNs) are assigned to telephone companies to aid in this administration, as AOCNs serve multiple vendors. Vendors are required to select an AOCN. NECA Services, Inc., a company evolving from the National Exchange Carrier Association, Inc., was established in 2000, to provide AOCN services to telecommunications vendors. CHR Solutions, Inc., is also authorized to provide AOCN services and may enter and update information in Traffic Routing Administration (TRA) databases. See Operating Company Number. admittance (symb. Y or y) In an electrical circuit or material, a measure of the facility with which the current flows through the circuit or material. Admittance is rather whimsically expressed in mho units, which is ohm spelled backward, since ohms are used to express impedance, the reciprocal of admittance. Contrast with impedance. ADN See Advanced Digital Network. Adobe Systems Incorporated A California and Seattle-based company, Adobe is best known for PostScript, Acrobat, PageMaker, Premiere, and Illustrator, software products which are aimed at the large number of home and professional publishers, communications specialists, and graphics users. See Acrobat, PostScript. Adonis A computer network of the Institute for Automated Systems in Moscow, Russia. ADONIS Article Delivery Over Network Information Systems. A project of a group of well-known technical publishers for electronically publishing hundreds of scientific/technical journal articles. ADONIS data is made available on digital media and targeted for distribution to educational institutions and other relevant markets. adaptor A person or body (e.g., corporate entity) that makes use of or takes on a particular concept, style

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of management, technology, or device. The term is often used in reference to those who are early to adapt a new or unproven (bleeding edge) technique or technology. See adapter, adaptor. ADP automated data processing. ADPCM See adaptive differential pulse code modulation. ADQ See Average Delay in Queue. ADR 1. achievable data rate. 2. aggregate data rate. 3. analog to digital recording. 4. ASTRA Digital Radio. Radio based on the ASTRA European satellite system. ADRMP See autodialing recorded message player. ADRT approximate discrete Radon transform. A mathematical technique used in situations where substantial redundancy is expected or encountered. See discrete cosine transform, Fourier transform. ADS 1. advanced digital system. 2. See AudioGram Delivery Services. 3. automated data system. ADSL See Asymmetric Digital Subscriber Line. ADSL Forum An international association of ADSL professionals formed in 1994 to promote and disseminate information about asymmetric digital subscriber line (ADSL) services, fast communications over copper wires. The Forum provides technical and marketing information, including conferences and analysis of ADSL-related technology http://www.adsl.com/ ADSP See AppleTalk Data Stream Protocol. ADSTAR Automated Document Storage And Retrieval. ADSU ATM Data Service Unit. A device for connecting to various data interfaces (e.g., in ATM networks) to support networking through standard connectionless and connection-oriented adaptation layers. ADT abstract data type. Software objects and structures that can be dynamically queried to determine their data types. In other words, the data type may not be known by the querying entity in advance. ADTV See advanced-definition television. ADU asynchronous data unit. advance ball A mechanism for supporting and steadying a cutting stylus (mounted just ahead of it) which is used for recording media such as phonograph platters. Most information storage is now done by rearranging magnetic data, or creating pits, rather than by cutting grooves into a physical medium. See acetate. ADVANCE Project A project of the European Community Telework Forum (ECTF) to stimulate and coordinate leading global telework development throughout Europe, in conjunction with other organizations committed to this goal. The stimulation of new types of businesses, particularly small businesses and the support of existing businesses, are key goals of the project. See European Community Telework Forum, telework. advance replacement warranty A type of warranty return/replacement service in which the replacement device or component is shipped prior to the returned

item so the user can continue usage until the problem is corrected or the unit replaced. This service is valuable if the essential component’s absence would negatively affect productivity. It’s important to check billing policies on ARWs because some companies will bill a credit card until the return unit is received and then apply a credit, all of which may be prone to error and confusion if not monitored carefully. Advanced Adaptive Protocol AAP. A network protocol designed to adapt dynamically to the available connection bandwidth, optimized to the application and device type. Advanced Branch Exchange ABX. Not in common usage, but a phrase used to distinguish traditional voice-only telephone exchange branches from those providing newer integrated voice/data capabilities. advanced broadcast television ABT. A general category encompassing audio/visual broadcast technologies that offer substantial quality and resolution improvements over traditional analog television services that prevailed until the 1990s. ABT systems typically offer better sound, higher resolution images, and interactive options. ABT services offered through cable are now usually digital, but analog/ digital hybrid systems will continue to exist as the nature of wireless radio transmissions is analog. Because of entrenched commercial consumer television technologies, the implementation of ABT has lagged far behind its technological development. However, as the buying public has become better informed about ABT-related products through marketing and the Internet, the demand for advanced services and home entertainment systems has increased, particularly in North America, Western Europe, and Japan. advanced common-view ACV. A time-referencing technique used to transfer frequencies and times of various of the standards that contribute to Coordinated Universal Time. Advanced Communications Technologies and Services ACTS. A European program for furthering communications technologies and infrastructures in the areas of multimedia, photonics, high-speed networking, mobile communications, and more. Over 200 projects have been part of the ACTS program providing valuable test and implementation information for European network development and deployment. See BLISS, BONAPARTE, BOURBON, BROADBANDLOOP, UPGRADE, WOTAN. http://www.infowin.org/ACTS/ Advanced Continuous Simulation Language ACSL. The first widely successful commercial software language to facilitate the simulation or modeling of the behavior of continuous systems described by time-dependent, nonlinear, differential transfer functions. This generic simulations tool is useful in a number of fields, including aeronautics simulations, control system design, toxicology, heat and fluid movement analysis, and chemical process dynamics. ACSL components include graphic modeling, simulation, mathematical analysis, open application program interface, visualization, and others. ACSL assets were acquired from MGA Software, Inc., in 1998 by Aegis Research Corporation with

the intent of integrating ACSL with HLA Lab Works software. advanced-definition television ADTV, ADT, ATV. A general category of television technologies and related services that encompasses improved resolution and picture quality over traditional analog television up to the 1990s. See Advanced Television Systems Committee. Advanced Digital Network ADN. A commercial leased-line 56 Kbps digital phone subscriber service. Advanced Intelligent Network AIN. A telephone services architecture based around Signaling System 7 (SS7), and possible future versions of SS7, intended to integrate ISDN digital capabilities and cellular wireless services into a personal communications system (PCS). The AIN grew out of the Intelligent Network (IN) system initiated by Bell Communications Research (Bellcore) in 1984. It can dynamically process calls by evaluating ‘trigger points’ through the call handling process. Currently a newer technology to AIN is in development, called Information Network Architecture (INA), that may coexist with AIN or eventually supersede it. See Information Network Architecture, Intelligent Network, Personal Communications System. Advanced Metal Powder AMP. A durable metal powder technology suitable for use in high-capacity, very dense storage technologies such as backup tape cartridge media. AMP enables smaller particles to be used and can be coated with thinner coatings to create dense recording surfaces with higher magnetization levels than traditional media. AMP is used in Super DLTtape. See Advanced Thin-layered and High Metal Media. Advanced Mobile Phone Service AMPS. An analog cellular communications system utilizing frequency modulation (FM) transmissions. AMPS was the first standardized cellular phone service (1983) to use the 800 to 900 MHz frequency range, which is still the predominant type of cellular system in the world. NAMPS (Narrowband Analog Mobile Phone Service) is an interim enhancement to AMPS, which uses frequency division as a way of sectioning the bandwidth, a tradeoff that increases calling capacity but may also increase interference. See AMPS, cellular phone, mobile phone, cell, cluster, roaming. Advanced Network and Services ANS. A nonprofit organization founded jointly by the National Science Foundation, Michigan Education and Research Infrastructure Triad (MERIT), IBM, and MCI in September 1990 to develop a gigabit network to benefit American education and research. Initially ANS planned two independent networks running over the same system of physical lines. Various issues emerged as controversial, such as corporate access, cost of operations, and use of the MCI backbone topology, which was criticized as being insufficiently robust and lacking in redundancy. Advanced Peer-to-Peer Networking APPN. A distributed networking system, now included in the Systems Network Architecture (SNA) developed by

IBM. APPN workstations are dynamically defined to reduce the need for extensive changes when the network is reconfigured. APPN provides optimization of routing between devices, direct communication between users, direct remote station communication, and transparent sharing of applications over the network. Advanced Peer-to-Peer Networking+ APPN+, APPN Plus. An enhanced IBM APPN which includes faster throughput, dynamic rerouting and congestion control, and other features to make it competitive with TCP/IP. See Advanced Peer-to-Peer Networking. Advanced Photo System APS. A new consumer format for film photography introduced in 1996 which is now supported by major film manufacturers. APS comprises (1) a smaller drop-in cassette that automatically winds into the camera, (2) the capability of easily changing rolls that are partially exposed (with supported cameras), and (3) a wound negative that is stored in the film cartridge. When processed, the index prints are labeled to include the cassette number to facilitate matching prints and negatives for storage and reordering. The cassettes are about 20% smaller than standard 35mm film cassettes. Mid-film cassette exchange is enabled by magnetic data storage on the cassette which records how many frames have been exposed and automatically winds to the appropriate point. Symbols on the cassette indicate the exposed/unexposed/developed status of the cartridge so cartridges don’t have to be hand labeled to keep track of multiple rolls. Archive boxes are available from vendors for storing cartridges and their corresponding index print sheets.

The NASA/JPL Web site includes interesting conceptual drawings of the Advanced Radio Interferometry between Space and Earth (ARISE) project, including 3D images and large color posters, like the one pictured here, that can be downloaded for use in science education programs. [NASA/JPL image.]

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Advanced Radio Interferometry between Space and Earth ARISE. An advanced space communications/sensing project consisting of one or two 25meter radio telescopes stationed in high Earth orbit (HEO). In conjunction with Earth-based telescopes, the ARISE will use very long baseline interferometry (VLBI) to obtain the highest resolution images of the most energetic astronomical phenomena. The data collected will aid scientists in studying the structure and evolution of the universe. The ARISE Web site is coordinated through NASA/JPL with information on the equipment, the science, and the potential benefits of this type of cosmological research. http://arise.jpl.nasa.gov/ Advanced Satellite for Cosmology and Astrophysics ASCA. A cosmic X-ray astronomy mission in which the U.S. provided a scientific payload to the Japanese project, the fourth of its kind. ASCA (formerly called Astro-D) was launched in February 1993. It was the first such mission to use CCDs for X-ray astronomy. The technology is highly sensitive and especially useful for observing emission lines and absorption edges. ASCA carried four large-area X-ray telescopes; two for use with a gas imaging spectrometer (GIS) and two with a solid-state imaging spectrometer (SIS). The observing program was available to participating Japanese and U.S. institutions and members of the European Space Agency. In July 2000, attitude control was lost and in March 2001, ASCA re-entered Earth’s atmosphere.

A diagram of the ASCA satellite when it was called Astro-D. The four X-ray telescopes are shown in the ‘nose’ on the lower left. The S-band and X-band frequency antennas are between the solar panel ‘wings’ behind the nonspin and spin sun sensors. [NASA/ASCA diagram, public domain.]

Advanced SCSI Programming Interface ASPI. A SCSI host adapter-independent programming interface released by Adaptec in the late 1980s. ASPI permits multiple device drivers to share a disk controller by providing a consistent device driver interface. Typically developers have had the burden of supporting many different host adapters, writing several, sometimes dozens of individual device driver definitions and programs for their users. The user then either has to install and load them all or search through them at installation time, trying to locate the right device driver for the hardware peripheral,

often a time-consuming, hit-or-miss process. With ASPI, vendors can make their products ASPIcompatible, so software can talk to the hardware without many extra files or hit-or-miss installation effort on the part of users. While there are similar systems from other vendors, this is one of the more popular ones. Advanced Synthetic Aperture Radar System ASARS. A realtime, high-resolution aerial military reconnaissance system for locating ground targets. The system is capable of surveying over 100,000 square miles per hour. It has been installed in SR-71 Blackbird aircraft as the Blackbirds are fast and capable of flying to great heights, and thus suitable for use as sensor platforms. In addition to classified military applications, ASARS-2 has been used to assess damage from natural disasters such as floods and earthquakes. ASARS technology has been the basis for the development of other radar technologies, including the HISAR and Global Hawk systems. advanced telecommunications capability This is defined in the Telecommunications Act of 1996 and published by the Federal Communications Commission (FCC) as: “ ...without regard to any transmission media or technology, as high-speed, switched, broadband telecommunications capability that enables users to originate and receive high-quality voice, data, graphics, and video telecommunications using any technology.” Advanced Telecommunications Institute ATI. ATI, located at the Stevens Institute of Technology, promotes and supports the research of advanced telecommunications applications and services. http://www.ati.stevens-tech.edu/atihomepage/ advanced television, advanced TV ATV. A generic category for television broadcast technologies that supply better audio and/or video characteristics than are generally associated with the traditional NTSC system in North America. Various means of digital manipulation at the broadcasting or receiving ends can result in better picture viewing or sound without changing the underlying broadcast format, while others require a completely different way of sending and encoding a signal. High Definition Television (HDTV) is a type of advanced TV. See Advanced Television Systems Committee, ATSC Digital Television Standard. Advanced Television Enhancement Forum ATVEF. A consumer electronics, broadcast, and cable networks industry alliance promoting the creation and distribution of enhanced television technologies at costs accessible to general consumers. See Advanced Television Forum, ATVEF Enhanced Content Specification. http://www.atvef.com/ Advanced Television Evaluation Laboratory ATEL. A world-class subjective evaluation facility, conformant to ITU-R Rec. 500. ATEL was one of three primary labs used to test advanced television systems that led to the Final Report of the Advisory Committee on Advanced Television Service (ACATS). ATEL is used by the Advanced Video Systems Group of Communications and Research

Centre Canada (CRC) to conduct research and testing. The Advanced Video Systems Group conducts leading-edge research in video technologies and human visual perception as they relate to a wide variety of broadcast and multimedia applications. See Advanced Video Systems Group. http://www.crc.ca/ Advanced Television Forum ATVF. A nonprofit corporation that addresses global issues related to content and technology for enhanced TV technologies including commercial implementation of these technologies. http://www.atvf.org/ Advanced Television Systems Committee ATSC. An international committee establishing voluntary technical standards for advanced television systems. The ATSC has established Recommended Practices for the industry. The ATSC Technology Group on Distribution released the ATSC Digital Television Standard in September 1995 (Document A/53). The same year, the ATSC also published Guide to the Use of the ATSC Digital Televison Standard (A/54). The Digital Television Standard was, in large part, adopted by the Federal Communications Commission (FCC) in December 1996 and also adopted by Canada and some Asian and South American countries. The influential standards document was revised by the ATSC and released as A/53A in April 2001. It specifies the technical parameters of advanced TV systems, including input scanning formats, preprocessing, and compression parameters, the service multiplex, transport layer characteristics, and the transmission subsystem. The implementation of these standards may require licensing of patented technologies. For a summary overview of highlights of the standard, see ATSC Digital Television Standard. ATSC Standards documents can be downloaded from the Web. http://www.atsc.org/ Advanced Television Technology Center, Inc., Advanced Television Test Center ATTC. A private, nonprofit, corporate laboratory facility established in 1988 to test and recommend practical technology solutions for delivery and display of new U.S. terrestrial broadcast transmission systems. The ATTC, located in Alexandria, Virginia, was established as a result of Federal Communications Commission (FCC) Advisory Committee on Advanced Television Service (ACATS) research into advanced television (ATV) systems. It was determined that paper specifications for ATV would not be sufficient to fulfil the ACATS mandate and that a test facility was needed to evaluate various hardware configurations. The ATTC was colocated with the Cable Laboratories ATV facility. The primary mandate of the Center is to facilitate the implementation of digital television technologies. The Center further supports education of engineers and other broadcast professionals through seminars and certification information. Articles and research reports are available online in Adobe PDF format. In 1990, Harris Corporation provided the radio frequency Test Bed used in testing the digital television systems. See Advisory Committee on Advanced Television Service, Association for Maximum Service Television, Harris Broadcast Communications.

http://www.attc.org/ Advanced Thin-layered and High Metal Media ATOMM. A super-thin, super-smooth coating developed by Fujifilm that enables a magnetic layer over a nonmagnetic layer of titanium to be coated. This highly smooth surface improves read/write head-tomedia contact and reduces spacing loss in order to support high-density recording and storage capacities. Using Advanced Metal Powder (AMP), the smaller, more thinly coated particles have a higher magnetization level. See Advanced Metal Powder. Advanced Tracking and Data Relay Satellite System ATDRS. A NASA project to provide a shared communications service between the Earth and a geosynchronous orbit position. Among other things, the ATDRSS would facilitate launch and landing planning, testing, and execution. The system consists of relay satellites and two independent ground terminals. Planning studies for Phase B began in the early 1990s, and the satellites were expected to provide services until about 2012. Advanced Very High Resolution Radiometer AVHRR. A broadband device for sensing passive radiation emitted from the Earth and its atmosphere. AVHRR technology is used on orbiting satellites, notably the National Oceanic and Atmospheric Administration’s (NOAA’s) Polar Orbiting Environmental Satellites (TIROS and NOAA-x) that have carried it as of 1987. The AVHRR provides global collection of data as the satellite orbits the Earth 14 times a day. Data formats include High-Resolution Picture Transmission (HRPT), Local Area Coverage (LAC), and Global Area Coverage (GAC). Data are both recorded and continually transmitted. The EROS Data Center (EDC) receives data from over the conterminous U.S. about six times a day and, since 1990, also receives global LAC and GAC data. AVHRR data are suitable for many applications, including the research, mapping, and monitoring of vegetation (forests, grasslands, tundra), agriculture, and land cover. See Global Area Coverage. Advanced Video Systems Group AVSG. A Canadian research group engaged in high technology multimedia and broadcasting studies, including broadcast television, high-definition television, and 3DTV. The AVSG utilizes the Advanced Television Evaluation Laboratory for its research. More specifically, it studies video technologies as they relate to human perception. The Group has strong ties to the Video Quality Experts Group (VQEG), an international association of experts tasked with validating objective measures of picture quality for broadcasting. See Advanced Television Evaluation Laboratory. Advisory Committee on Advanced Television Service ACATS. A committee of private sector individuals providing broad representation from the television broadcast industry reporting to the Federal Communications Commission (FCC) to recommend improvements to existing National Television Systems Committee (NTSC) television broadcast standards. The original North American NTSC standard was adopted by the FCC in 1941, with NTSC color standards adopted in 1953. Since then, there have

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been many improvements in technology, but sluggish commercial implementation and consumer adaptation of advancements hindered the commercial success of advanced technologies. ACATS was formed in response to this industry lag and to the fact that technologies in other nations appeared to be advancing ahead of U.S. standards. Since its formation, ACATS has narrowed its focus and made recommendations on advanced television (ATV) service to the FCC. The Committee began to concentrate on advanced television technologies in 1987 and adopted/presented their Final Report in October/November 1995. Surprisingly, digital systems were not a significant focus of the Committee until 1990, when the convergence of computer technologies and broadcasting began to make a significant impression. In the Final Report, ACATS optimistically suggested ways in which commercial television could be brought into closer line with technological advances and provided advisement on ATV technical standards, based on theory and laboratory research. Research was conducted primarily at the Advanced Television Test Center (ATTC), a private, nonprofit organization, Cable Laboratories, Inc. (CableLabs), a research and development consortium of American cable TV system operators, and the Advanced Television Evaluation Laboratory (ATEL), a facility of the Canadian Department of Communications. After narrowing many initial proposals, one EDTV system and five HDTV systems were laboratory tested from 1991 to 1992, resulting in the one analog system being eliminated from further consideration. It was then decided to combine the remaining digital systems into one “best system” rather than to continue the expensive process of developing and testing four separate systems which were, in many ways, converging. Thus, the Digital HDTV Grand Alliance was formed. The ACATS Technical Subgroup continued to work with the Grand Alliance and the Alliance was exhorted to retain a flexible approach and retain the public process aspect of development. The Alliance/ ACATS system was tested and evaluated in the field in 1995, with the Final Technical Report based upon the results. At the time the Report was released, the broadcast system was the only one in the world to incorporate and support both scanning techniques (including progressive scanning formats). While the system was recommended for terrestrial ATV broadcasting, the Committee considered it to be sufficiently broad in its formulation to accommodate many computer media delivery technologies. Thousands of public documents were generated during the course of the project, including a number of interim reports and recommendations. A report to the U.S. Congress was presented in 1989. A subgroup of the U.S. Government’s Information Infrastructure Task Force endorsed the Report, along with the 1994 NIST/ARPA Workshop on Advanced Digital Video, and the Information Technology Industry Council. Much of the volunteer work and all out-of-pocket expenses were underwritten by Committee members. Laboratory work was funded by sponsors and grants.

See Advanced Television Systems Committee, Digital HDTV Grand Alliance. http://www.atsc.org/ Advisory Committee on Public Interest Obligations of Digital Television Broadcasters PIAC. A committee established by U.S. Presidential Executive Order #13038 to study and advise on public interest responsibilities for those granted digital television licenses. Because airspace, that is, broadcast spectrum frequencies, is a limited and prized commodity legally belonging to the American people, those being granted licenses have a compensatory responsibility to serve the public interest, not to engage only in for-profit commercial enterprises. To fail to require commercial broadcasting companies to support public services and diverse subscriber communities through broadcasting would be like granting commercial industries unrestricted access to the resources of public parks without consideration for the needs and desires of the public itself. NTIA is the Secretariat for the Advisory Committee. The Committee was comprised of members of the public, the broadcasting and computer industries, academics, and labor representatives. The Committee’s final report “Charting the Digital Broadcasting Future” was released in December 1998. Recommendations made by the Committee in the report include • disclosure of public interest activities by broadcasters on a quarterly basis • drafting of an updated voluntary Code of Conduct to reinforce public interest commitments • adoption of a set of minimum public interest requirements for broadcasters in services for public benefit • improvement of education through broadcasting • balancing of the economic benefits of new multiplexing technologies with the choice of a fee, contribution, or provision of multicasted channels for public interest purposes • improvement of the quality of political discourse through free airtime before a major election and removal of prohibitions or bans on sale of airtime to state and local political candidates • cooperation with emergency communications specialists for effectively transmitting disaster warning information • support for digital programming for the disabled • encouragement and furtherance of diversity in broadcasting • exploration of alternative approaches inherent in the new television environment for serving public needs and interests In addition to Committee recommendations, a number of dissenting opinions and alternate recommendations were submitted and provided in Section IV of the Advisory Committee’s report.

The report itself was criticized by some as too lenient. In general, it recommends voluntary compliance and, in fact, provides for approximately two years of experimentation with new frequencies before the full mandate would take effect. From the point of view of detractors, the situation could be described as giving out experimental expense accounts and then saying two years later, “don’t forget to make some voluntary charitable contributions with the money we gave you.” Some questions lingered after release of the report. Can commercial entities be relied upon to serve consistently the public interest without strong incentives and directives to do so? Will the full potential of new advanced television technologies be realized if subscribers are seen only as consumers and not as participants in the building of an information society? Thus, in October 1999, Vice President Al Gore wrote to the Chairman of the FCC tasking the FCC with taking “... the next critical step: examining how broadcasters can fulfill their obligation to serve the public interest. Because of the critical importance of television to our nation, we believe that Americans should have the opportunity to participate in the process, we urge the Commission to institute a public proceeding to consider the public interest obligations of digital television broadcasters.” Thus, there are ongoing important issues faced by the government, the broadcast industry, and the public which remain relevant and subject to scrutiny and debate in an environment driven by a powerful broadcast industry that seeks voluntary self-regulation. See Alliance for Better Campaigns, Benton Foundation. advocacy Providing support, promoting acceptance or use. Advocacy has played a prominent role in the evolution of the Internet and in computer development and marketing. Because the interests of promoters of universal access for technology are not always consistent with the goals of government or big business, many users’ groups and advocacy forums have been established online. Almost every USENET newsgroup devoted to a specific computer platform has an advocacy section for the discussion of issues related to platform design, acceptance, and use. AE 1. acoustic emission. 2. Application Entity. AEA 1. See American Electronics Association. 2. See American Engineering Association. AEC See acoustic echo canceller. AECS Plan Aeronautical Emergency Communications System Plan. A voluntary system of communication established and organized for the provision of emergency communications to the U.S. President and federal government representatives. AECT See Association for Educational Communications and Technology. AEEM Aerospace Engineering and Engineering Mechanics. AEGIS Advanced Electronic Guidance and Instrumentation System. Aegis System An advanced, automatic tracking and detection phased-array radar used by the U.S. Navy

since 1973 to perform simultaneous searching, tracking, and missile guidance functions. AEP See AppleTalk Echo Protocol. aerial A term applied to conductive wires or structures used in transmissions. The term is derived from the fact that most wires are suspended from poles, towers, or other aerial structures high enough to provide safety from interference and electrical hazards and to receive or send unimpeded signals. Sometimes aerials are distinguished as signal receivers, and antennas as signal senders. And sometimes the opposite distinction is made, so there isn’t much consistency in usage. Since insect antennas can be considered as receiving units, it might make sense to call the receiver the antenna. Because of the lack of standardization of the terms, and because many of the same concepts of design and construction apply to both sending and receiving structures, this dictionary groups most of the information on aerials and antennas under the heading of antenna. See antenna. aerial cable Transmission-receiving circuits that are strung through the air, typically supported by utility poles to keep them out of reach since many carry hazardous levels of current. Contrast with buried cable. aerial distribution Aerial cabling configuration, with wires running through the air among buildings and poles. Various insulators and amplifiers or repeaters are used in many cable installations to protect signals from interference or to extend them over distance. Aerial distribution puts hazardous wires out of reach and is an alternative to underground or wallbased distribution. See distribution frame. Aerial Experimental Association AEA. A research organization promoted by Mabel Gardiner Hubbard Bell, the wife of Alexander Graham Bell, to support his strong interest in kites and future aviation. It was established in 1907 by a small group of aviation enthusiasts. aerogram 1. A European term for correspondence that is lightweight, and intended to be transported on planes. Charles Lindbergh, the pilot, was one of the early pioneers of air mail service. Many countries of the world have high postal rates for air mail, based on weight. Aerograms are often written on very light, fine paper, or even on paper that folds into its own envelope, rather than requiring a separate envelope. 2. A letter sent by airwaves, as through radiotelegraphy. Radiograph is another early name for a radio telegraph. Aeronautical Administrative Communications AAC. A service of the aeronautical industry serving cockpit voice communications. Data connectivity that includes AAC is part of the Aeronautical Telecommunication Network (ATN). aeronautical broadcasting Various government and commercial services providing information to the aeronautics industry, especially regarding meteorological conditions. Aeronautical Mobile Satellite Service AMSS. A global mobile communications service implemented using Inmarsat geostationary satellites. Through a

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dedicated range of radio frequencies operating in discrete FDMA channels, the system provides information to aircraft worldwide (with some limitations near the Earth’s north and south poles). Three types of channels provide unidirectional dedicated communications and a fourth type of channel provides bidirectional communications. Channels are selected on the basis of the type of transmission (data or voice) and the length of the message. Information relevant to weather forecasting is also conveyed through AMSS. See Aeronautical Telecommunication Network. Aeronautical Telecommunication Network ATN. A system of cooperative data networks that together comprise a global aviation intercommunications structure which includes both fixed and mobile stations. It enables government air traffic control authorities and various aviation communications services with a variety of transmission types to interconnect. The system is being set up according to standards and guidelines developed by various prominent aviation and engineering organizations and is based on the Open Systems Interconnection (OSI) model. See Aeronautical Mobile Satellite Service. aerospace Space consisting of: (1) the Earth’s atmosphere above ground, the region in which much broadcasting and travel occurs, and (2) the space beyond, into which satellites, probes, and spacecraft are launched. Also, the industries and sciences concerned with space travel and communications. Aerospace & Electronic Systems Society AESS. A society of the IEEE for members interested in the design, testing, and analysis of large, complex systems such as sensor systems for communications and navigation. The AESS sponsors individual chapters, conferences and panels and publishes AESS Transactions and the AESS Magazine. http://aess.gatech.edu/ Aerospace Industries Association of America, Inc. AIA. A trade association founded in 1919 that supports American manufacturers of commercial aircraft, engines, spacecraft, missiles, and related equipment. AIA represents its membership’s needs and goals to the media, the public, other related organizations, and the U.S. Congress. http://www.aia-aerospace.org/ AES 1. Application Environment Standard, Application Environment Service. 2. atomic emission spectroscopy. 3. See Audio Engineering Society. AES 90 The first large-scale commercial word processor, introduced by a Canadian company, Automatic Electronic Systems, in 1972. The system featured magnetic storage, with commands such as “Memorize” for saving a file, built around a custom microprocessor. Word processing on the AES system did not become widespread until the mid-1980s, as the business world was slow to make the transition from typewriters to word processors. AESS See Aerospace & Electronic Systems Society. AEW 1. aircraft early warning. 2. airborne early warning. Includes not only warnings of aircraft, but other airborne objects such as missiles and probes.

AF audio frequency. A spectrum of wavelengths that can be heard. For humans this is from about 30 hertz up to about 20 kilohertz, although the upper level declines to about 16 to 18 kilohertz by adulthood. AFAIK An abbreviation for “as far as I know” used in email and online public forums. See IMHO. AFAST Advanced Flyaway Satellite Terminal. A family of commercial, modular, portable satellite terminals operating in the C-, Ku-, and X-band frequencies, from California Microwave, Inc. (CMI). AFC 1. advanced fibre/fiber communications. 2. Australian Film Commission. 3. See automatic frequency control. AFCEA See Armed Forces Communications and Electronics Association. AFE 1. See analog front end. 2. antiferroelectric. affiliate In the Telecommunications Act of 1996, published by the Federal Communications Commission (FCC), the term affiliate has a specific meaning as follows: “... a person that (directly or indirectly) owns or controls, is owned or controlled by, or is under common ownership or control with another person. For purposes of this paragraph, the term ‘own’ means to own an equity interest (or the equivalent thereof) of more than 10 percent.” See Federal Communications Commission, Telecommunications Act of 1996. affine redundancy A phrase attributed to Michael Barnsley, who used it to describe the characteristics of fractals in terms of their self-similarity, and their likelihood of looking more like parts of themselves, than parts of other things. See fractal. affirmative In voice communications where signals are weak or noise is present, a synonym for “yes” which is intended to be clear and unambiguous. AFI Authority and Format Identifier. In ATM, part of the network level address header. AFIPS American Federation of Information Processing Societies. A national organization of data processing societies which organizes the National Computer Conference (NCC). AFK An abbreviation for “away from keyboard,” used especially on public chat channels on the Internet and on BBS chat rooms to indicate someone with his or her hands full who can’t type (eating, reaching for a book), or who is away for a while to answer a door, a phone, to help a child, or visit the washroom. AFK messages should be taken with a grain of salt, as the person may have stepped out to go to the store, attend a class, or engage in other activities that keep him or her away from the keyboard for extended periods. See also BRB. AFM 1. Adobe Font Manager. 2. Adobe Font Metrics. 3. antiferromagnetism. AFMR antiferromagnetic resonance. AFNOR Association Française de Normalisation. The national standards organization of France. http://www.afnor.fr/ AFOSR See Air Force Office of Scientific Research. AFP See AppleTalk Filing Protocol.

African Telecommunications Union ATU. Descended from the Pan-African Telecommunications Union (founded in 1977), the ATU was established in December 1999 by the 4th Exta Ordinary Session of Plenipotentiaries of the Pan African Telecommunications Union (PATU). The ATU seeks to make Africa an equal and active participant in the global information community by supporting and promoting the development of telecommunications policies, human resources, and technologies. http://www.atu-uat.org/ AFS See Andrew File System. AFT Automatic Fine Tuning. See automatic frequency control. afterimage A visual image that may appear in pale outline or as a complementary color if an object is viewed for some time without moving, after the source of the image has changed or disappeared. The concept is important in designing display technologies. See persistence of vision. AFTRA American Federation of Television and Radio Artists. A trade organization representing performers, founded in 1937. http://www.aftra.org/ AFV audio-follow-video. In many broadcast systems, audio and video are recorded and/or transmitted separately. In AFV, the audio signals are automatically routed together with their associated video signals. agate line In typography, a unit of measurement typically used by periodicals to communicate column sizes for articles and ads. 14 agate lines = 1". Agate line measurements may cross columns, since display ads and images for headline stories are often two or more columns wide. AGC 1. AudioGraphic Conferencing. ITU-T terminology related to transmissions protocols for multimedia. See audiographics. 2. See automatic gain control. AGCOMNET A U.S. Department of Agriculture voice and data communications network. aged packet In packet-switched networks, a data packet that has exceeded a prespecified parameter such as node visit count or elapsed time. Aged packets may be handled in a number of ways, depending upon their nature and the configuration of the network. They may be discarded, assigned a different priority, or returned to the originator. Agency of Industrial Science and Technology AIST. A Japanese organization that is part of the Ministry of International Trade and Industry (MITI) that superintends research laboratories acknowledged for their technological innovation. agent 1. Representative, broker, one who acts in place of or on the authority of another. 2. One who handles customer inquiries and procures services or products for that customer, often through other firms. Real estate agents serve as liaisons between sellers and buyers, and travel agents are liaisons between airlines and travellers. Many long-distance providers are agents who procure services through other companies or through leased lines rather than by installing their own physical equipment. 3. On net-

works, software agents are frequently used in client/ server transactions to gather, organize, or exchange information according to security and priority levels usually established by the server. 4. On computers, in a general applications sense, agents are products (such as utilities or plugins) that do long, tedious or complex tasks, in conjunction with, and generally on behalf of, server software or user applications. AGFNET Arbeitgemeinschaft der Grossforschungseinrichtungen. A German SNA-based computer network serving post-secondary institutions and research facilities. aggregate bandwidth In a stream carrying more than one communication through some system of multiplexing, the aggregate bandwidth is the total combined bandwidth. aggregation The bringing together or combining of physical, data, or radiant waves as in cables or transmissions. Aggregation typically refers to bringing together in terms of proximity, usually without a merging of information or electrical characteristics. However, some types of data are aggregated through an interleaving process, while still keeping individual portions true to their origins. Multiplexing is often used in conjunction with, or as a means of, aggregation. Agents sometimes aggregate, that is bundle, services for consumers. Cable companies sometimes aggregate certain types of stations into package deals for cable subscribers. aggregate transmission The multiplexing of the transmissions of large numbers of users over a network backbone. aggregator A service agent, broker, or liaison who coordinates negotiations on behalf of a block of subscribers, usually to get reduced rates. Billing is done by the service provider once the service has been established or facilitated by the aggregator. Agility Communications A California-based company formed in 1998 to take advantage of commercial opportunities in dense wavelength optical networking. Agility is developing laser-based tuning for very high channel capacity communications based on Bragg reflectors. See Bragg reflector. aging 1. v.t. A process of storing materials until their properties become essentially stable or reach a desired set of characteristics. 2. v.i. The characteristics of a material or process over time under a certain set of conditions. This may be an improvement, a deterioration, or simply a change. agonic In magnetism, an imaginary line connecting all points on the earth where the magnetic declination is zero. See declination, isogonic, magnetic equator. AGP See Accelerated Graphics Port. AGT 1. Alberta Government Telephones. 2. AudioGraphics Terminal. AGU 1. address-generation unit. 2. Automatic Ground Unit. Ah ampere-hour. AHEN 1. Alabama Home Educator’s Network. A network to enhance communication among home schoolers. 2. Alberta Higher Education Network.

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3. Alternative Higher Education Network. Formally the Alternative Colleges Network. AHT Average Handle Time. A call management phrase that describes the amount of time it takes, on average, to take a call, talk to the caller, and handle the caller’s needs at the end of the call. For example, on a typical sales call, it may take a minute to connect with the desired person, fifteen minutes for the call, and twenty minutes after the call to log the caller’s feedback and arrange to have a sales brochure sent to the caller. AI 1. Airborne Interception. A radar-assisted fire control system used in military interceptor aircraft. 2. See artificial intelligence. AIA 1. See Aerospace Industries Association of America, Inc. 2. American Institute of Architects. 3. Application Interface Adapter. A software utility which converts client function calls to standard SCSA messages. AICE See Australian Institute of Computer Ethics. AIEE American Institute of Electrical Engineers. It was consolidated with IRE to form the IEEE, an influential body of engineering professionals. See IEEE. AIFF See Audio Interchange File Format. AIIM See Association for Information and Image Management. Aiken, Howard Hathaway (1900-1973) An American Harvard student and engineer who proposed development of a large-scale calculating machine, a historic forerunner of later electronic digital computers. The motivation for the machine was to create a system to solve cumbersome math equations, and the inspiration came from the writings of Charles Babbage and the Hollerith tabulating systems. Aiken was working on his doctorate when he conceived the idea and wrote a report. He subsequently received financial support in the 1940s from the President of International Business Machines (IBM), Thomas J. Watson, to build the Automatic Sequence Controlled Calculator, later renamed the Harvard Mark I. The success of the project led to the development of further computers in the series, including the Mark II, Mark III, and Mark IV computers, each building upon the experience of the previous system. The success of the Mark I and the motivation provided by World War II helped spur the development and financing of these very large-scale computers. They were soon put into service by the U.S. Navy for calculating ballistics and other related equations, and Grace Hopper joined the computer project as a programmer. Aiken retired from Harvard in 1961. See Harvard Mark I to Harvard Mark IV. AIM 1. amplitude intensity modulation. 2. See Ascend Inverse Multiplexing protocol. 3. See Association for Interactive Media. 4. ATM inverse multiplexer. AIN See Advanced Intelligent Network. AIOD See Automatic Identified Outward Dialing. AIP ATM Interface Processor. A Cisco Systems commercial router network interface (ATM layers AAL3/ 4 and AAL5) for reducing performance bottlenecks

at the User Network Interface (UNI). AIR 1. additive increase rate. In ATM, a traffic flow control available bit rate (ABR) service parameter which controls cell transmission rate increases. See cell rate. 2. Airborne Imaging Radar. 3. All India Radio. 4. See Association of Independents in Radio. air bridge In electronics, a suspended interconnect, usually of metal. air capacitor, air condenser A capacitor/condenser whose dielectric is air. air cell A type of electrolytic wet cell once widely used in phone applications. It consists of separate cells connected in order to increase the voltage. Polarization is reduced because oxygen from the air combines with hydrogen from the carbon electrode to form water. These historic cells had a useful life of a thousand or so hours, and required sufficient ventilation. See dry cell, wet cell. air column A channel of air, usually with certain size specifications or sound characteristics, within a piece of equipment, instrument, or chamber. Air column cables sometimes employ air as a dielectric, thus enabling a lighter, more flexible cable than one with a solid dielectric. See air-spaced coaxial cable. air conditioning Running air through a system to alter its characteristics to make it suitable for people, equipment, or both. An air conditioner can affect temperature, humidity, and ion balances. Air conditioners are often used to cool work rooms in hot climates, and to cool equipment that generates heat but may be damaged by the heat if the air temperature is not kept down. Many large supercomputing installations require cooling, and chip manufacturing plants condition the air to keep it free of dust, smoke, and other particles. air core transformer A type of transformer designed to overcome some of the limitations of iron core transformers. At the higher frequencies used by broadcast communications, various problems such as the eddy effect and the skin effect will interfere with transmissions. Thus, air core coils and transformers, carefully tuned, can overcome some of these problems by eliminating the core. Air Force Office of Scientific Research AFOSR. Descended from a small office of the Air Research and Development Command in 1951, AFOSR became the single manager for basic research within the U.S. Air Force in 1975. It provides the opportunity to direct leading edge research and technologies, through the Air Force Research Laboratory, to laboratories of the U.S. Department of Defense and U.S. industry. http://afosr.sciencewise.com/ air gap A region of air through which an electrical spark or magnetic current travels, as in spark gaps in gasoline engines. air-incident recording AIR. A recording mechanism for magnetic media storage products (tape, hard drives, etc.) that utilizes a recording layer on top of a substrate layer. The substrate helps protect the recording head from brief impacts with the surface, a system that works best in a sealed, stable environment. Contrast with substrate-incident recording.

air interface, airlink interface, A interface A radio frequency-translating interface for wireless communications. In cellular communications, the air interface is the radio-frequency-based connection between a Mobile End System (M-ES) and a Mobile Data Base System (MDBS). If the user is traveling, the MDBS may change as the user moves from one cell to another. As an example, an air interface enables Cellular Digital Packet Data (CDPD) to be deployed over AMPS. In local area wireless networks (LAWNs), the air interface is the radio frequency portion of a network that enables computers to exchange data without wires. In North America, LAWN air interfaces typically operate in unlicensed 900-MHz and 2.4-GHz frequency regions. In European HIPERLAN implementations, radio spectrum has been dedicated to wireless computer networks. There are many ways to implement a mobile air interface and the International Telecommunications Union (ITU) has encouraged global standardization efforts for mobile phone technologies through its International Mobile Telecommunications 2000 project (IMT-2000). Several air interface proposals were part of this project (e.g., wideband CDMA). There are now two common air interface (CAI) standards for CDMA, cellular (TIA/EIA/IS-95A) and PCS (ANSI J-STD-008). More recent air interface schemes, such as TDMA/ TDD systems, can deliver capacity that is hundreds of times greater than older systems and as much as forty times greater than many 3G systems. Systems with data rates up to 40 Mbps are commercially available. Testing and troubleshooting of wireless networks presents a special set of problems. The airwaves are full of radio signals, all coexisting at various frequencies and strengths. Nevertheless, vendors offer diagnostic instruments that measure field strength and, more recently, have begun to offer instruments that can decode the protocols (voice and data) used in the air interface, in order to fine-tune the system and fix or prevent potential problems. Devices for evaluating Quality of Service (QoS) are also available for auditing air interface transactions for a variety of wireless technologies. See B interface, C interface, Cellular Digital Packet Data, D interface, E interface, Global System for Mobile, HIPERLAN, I interface, local area wireless network. air miles Accumulated miles traveled on a particular airline or under a special program. Air miles programs are marketing tools used by airlines and their affiliates to calculate bonus trips, class upgrades, and other customer incentives. The term air miles has become very broad, since air miles can now be accumulated in a variety of ways, including through long-distance calls, hotel stays, rail trips, etc. Air Route Surveillance Radar ARSR. A long-range radar system that provides information on aircraft locations over a broad geographic area by transmitting the information to a display system in a track-

ing tower or center. air time Time spent online, broadcasting, or engaged in two-way or multiple connect wireless conversation. A measure of accumulated air time is used by service providers as an accounting tool for scheduling, billing, and time management on shared systems. air-blown fiber ABF. See blown fiber. air-spaced coaxial cable A type of cable assembly design that incorporates air as a dielectric in order to minimize the loss of signal. Since there is no way to suspend the central core exactly in the middle of the column of air, air-spaced cables require spacers which are usually of some type of plastic, inserted at intervals over the length of the cable, sufficiently far apart to let the air do its job (and to prevent moisture from entering), and sufficiently close together that a twist or bend in the cable doesn’t allow the inner core to make contact with the next layer. See coaxial cable. airbrush A painting tool that combines a fine spray nozzle with an air compressor to create fine gradations and details. In computer imaging, a functionally similar tool has been incorporated into paint programs to allow the creation of subtle blends and misty effects. The density of the individual dots, and the shape and extent of the spray area are usually configurable. aircraft earth station A mobile satellite transceiving station that, instead of being stationed on the ground, is installed on board an aircraft. AIRF See additive increase rate factor. airline miles See air miles. airplane dial A type of rotary dial common on old radio systems that, when turned, moves a needle-like indicator back and forth in an arc, or straight line according to a marked gauge, similar to the gauges seen in airplane cockpits. Airplane dials are often used along with sliders on analog systems and with pushbuttons on analog/digital systems. Airport Surveillance Radar ASR. Short-range radar coverage for airports and their immediate surroundings to facilitate the management of terminal area traffic and to provide the option of instrument approach assistance. airtime, air time 1. The time during which a specific broadcast is active (airs). 2. Time allocated to a specific broadcast, whether or not it is used. 3. The time spent on a radio phone call. This information is frequently used in billing calls, as in cellular phone systems. Unlike wired systems where toll-free numbers or busy numbers are not billed, many wireless services bill for the amount of time the call is online, regardless of whether it is connected to a toll-free or local callee. AIS 1. See alarm indication signal. 2. Automatic Intercept System. 3. See Association for Information Systems. 3. automated information system. AIST See Agency of Industrial Science and Technology. AISTel Associazione Italiana per lo Sviluppo delle Telcomunicazioni. Italian Association of

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Telecommunications Development. http://www.telecom-italia.org/ AIT 1. assembly, integration and testing. 2. Atomic International Time (more correctly known by TIA). See International Atomic Time. 3. See automatic identification technology. AITS 1. Administrative Information Technology Services (University of Illinois) 2. Advanced Information Technology Services. 3. Associazione Italiana Tecnici del Suono. Italian Technical Association for Sound. 4. Australian Information Technology Society. AIX Advanced Interactive Executive. An International Business Machines (IBM) implementation of Unix. AJ anti-jam. A communications signal structured so that it is resistant to jamming or interference. AJP American Journal of Physics. AKA also known as. 1. Alias, handle, nickname. 2. False or fraudulent name. Al aluminum. AL Adaptation Layer. See ATM in appendix. ALA See American Library Association. ALAP See AppleTalk Link Access Protocol. alarm Warning signal, a signal to indicate an error or hazardous situation. Alarm signals are generally designed with flashing lights or raucous noises to attract immediate attention. In electronic equipment, alarms are signaled by various messages, flashing elements, or sounds and may or may not indicate the priority level and possible location or cause of the problem. alarm indication signal, alarm indicating signal AIS. 1. In ATM networking, a signal indicating that a failure has occurred. There are specific AISs in SONET circuits. Failure is declared if these conditions persist for a specified time period. • A line alarm indication signal (L-AIS) is an error condition in which a defect pattern is detected in specific bits in five consecutive frames. • A STS-path alarm indication signal is one in which specific consecutive bytes and the STS SPE contain all ones. • A VT-path alarm indication signal is applicable to VTs in floating mode. The AIS alerts the downstream VT Path Terminating Entity (PTE) of an upstream failure. The defect is detected as all ones in specific bytes and three contiguous VT superframes. 2. Blue signal, blue alarm. A signal that overrides normal traffic during an alarm situation. ALASCOM A commercial, regional communications service, consisting of satellite earth stations, fiber optic, and microwave links serving the state of Alaska. Alaska Public Radio Network APRN. A local news network serving the unique needs of the State of Alaska, which has an unusual profile consisting of small, discrete, diverse ethnic populations spread over an enormous geographic region. Alaska further has a population that is unusually dependent upon

radio broadcasting for news and social interaction due to its harsh and changing weather conditions and its scarcity of modern social/cultural amenities in geographically isolated communities. Thus, it faces technological and programming challenges beyond those of most other American states. APRN was founded in 1978. http://www.aprn.org/ albedo A ratio of the amount of electromagnetic radiation reflected by a body to the amount incident upon it. This reflectance may be described in the context of a portion of the spectrum (as the visible spectrum) or of the whole spectrum. The concept is used in telecommunications in relation to satellites and other celestial bodies. Albedo is complementary to absorptivity; it is often expressed as a percentage. ALBO automatic line buildout. In data transmissions, a means of automatic cable equalization. ALC 1. automatic level control. 2. automatic light control. ALDC adaptive lossless data compression. ALE 1. Application Logic Element. 2. Atlanta Linux Enthusiasts. 3. See automatic link establishment. alert signal, alerting signal A transmission signal designed to gain the attention of an administrator or user. In computer networks, alert signals signify many things, such as imminent shutdown of a system, talk requests, new user logins, newly arrived email, etc. On telephone networks, alert signals are often used to indicate an incoming call.

A 200-kilowatt Alexanderson motor used for radio frequency alternation for the Radio Corporation of America (RCA) in New Jersey. [Scientific American Monthly, October 1920.]

Alexanderson alternator A high-frequency generator designed by E.F.W. Alexanderson that was used in pioneer transatlantic communications. One of the historic uses of the Alexanderson alternator in broadcasting was at the Fessendon station which, in 1906, broadcast Christmas music to surprised and delighted listeners. Alexanderson received a patent for his generator in November 1911 (U.S. #1,008,577). Alexanderson antenna A vertically polarized wired antenna used for low frequency (LF) and very low frequency (VLF) transmitting and receiving that is not commonly used above amplitude modulation (AM) frequencies. Alexanderson, Ernst F. W. (1878-1975) A pioneer

developer of radio alternators in the early 1900s. GE had been contracted by Fessendon to develop a high frequency alternator for his pioneer radio station in 1904. Ernst Alexanderson was assigned to the project and achieved this significant engineering feat. He was involved in some of the early television development that was occurring in the 1920s and demonstrated a home television receiving unit. The Alexanderson alternator and Alexanderson antenna are named after him. See Alexanderson alternator. Alexandre, Jean A French artist and inventor who was one of the earliest inventors of telegraph technology. Alexandre tried unsuccessfully to gain a direct audience with Napoleon to demonstrate what may have been dial-based electrical telegraph. Some have reported that his system was seen in 1801 or 1802, decades before the Wheatstone telegraph. He later went on to invent navigation and water filtration systems. See Salvà i Campillo, Francesc; telegraph history. Alford, Andrew (1904-1992) A Russian-born American inventor of antennas for radio navigation and communication. In 1940, Alford co-authored “Ultrahigh-Frequency Loop Antennas” in AIEE Transactions. After working for many years in telegraphy and navigation firms, Alford joined the Harvard Radio Research Lab in the mid-1940s to devote more time to electronics design. He was the founder of the Alford Manufacturing Company which coinvented (with Kear & Kennedy) pioneer frequency modulation (FM) antennas. These led to systems that could simultaneously broadcast multiple FM programs from a single transmissions source. Alford maintained a lifetime interest in antenna technologies. In his seventies, he continued to work and receive patents for his inventions, including a Doppler VOR ground station antenna for air navigation (U.S. #3,972,044 1974) and a two-frequency localizer guidance system and monitor (U.S. #3,866,228 1975 and #4,068,236 1978). Alford antenna There were many antennas designed over the decades by Andrew Alford, most of which are called Alford antennas and many of which are still in use. His invention of the localizer antenna system won him a place in the National Inventors Hall of Fame. Junctions for an Alford FM antenna wind through the 87th floor of the Empire State Building. One of Alford’s earlier designs is the horizontallypolarized, omnidirectional slot antenna, introduced in 1946. It is commonly implemented as a long metal, tubular antenna with a long, narrow slot or series of slots. While not the most efficient antenna design for every use, it is easy to build and has some advantages over common dipole antennas. Thus, it is popular for amateur radio enthusiasts for weak signal communications and as television repeating units. The design can be adapted to antenna beacons or used for fixed radio stations and satellite ground stations. The Alford loop antenna is a rectangular loop antenna, with each of the corners slightly infolded toward the center to lower impedance at the nodes. It

is used in navigation applications. See diagrams. ALGOL Algorithmic Language, Algebraic Oriented Language. A computer programming language developed in the 1950s by P. Naur, and others, for manipulating mathematical algorithms. C is said to be evolutionarily descended from Algol (with an intervening language called B). algorithm A procedure consisting of a finite series of steps, defined to solve a problem or execute a task. The solution to the problem does not necessarily have to be known to create an algorithm to seek out a solution, or a path toward a solution. Logical/mathematical algorithms are widely used in the computing industry. The algorithm itself may not have a fixed number of steps, since an algorithm can be designed to be self-modifying, but the initial tasks, as set out by a programmer, for example, are finite. See brute force, heuristics. ALI 1. See ATM line interface. 2. See automatic location identification. alias n. 1. Pseudonym, assumed name, substitute or alternate name. 2. On operating system command lines, a short, easily remembered label for a longer, harder to remember label or command. Most systems will allow users to set up aliases at boot-up time, or in a file that can be reread while the system is running, to update the aliases. On Unix systems, a convenient alias is ll in place of ls -la. It’s easier to type and displays more information in the subsequent directory listing, including permissions, file size, etc. 3. On Macintosh systems, there is a menu command to alias a filename. When selected, it causes an extra icon to appear, matching the original, under which the user can modify the name of the application, if desired, to better remember its function. This can be placed on the Desktop (or anywhere that’s convenient), in place of the original icon which may be buried several folders deep or have an obscure name. When double-clicked, the alias then finds the original and launches it on behalf of the user. 4. Online, many users will assume an alias identity, known as a handle, or nickname, in order to present a friendlier, more interesting, or more obscure face to others. 5. In computer imagery, a visual artifact consisting of rough, staircased edges. This may result from low sampling, or from low resolution in the output device. See aliasing. aliasing 1. In imaging, a visual artifact that causes rasterized images to take on a staircased effect when displayed or translated into resolutions that are too coarse to clearly resolve the image. See antialiasing. 2. In audio, a frequency distortion that occurs in sampling when the sampling rate and the frequency interact in undesirable ways. A filter can sometimes reduce distortion. aligned bundle A bundle of fibers or wires, in which the relative positions of each of the ends at one end are retained at the other end. In fiber optic transmissions, the bundling alignment is quite important to the quality of the transmissions. ALIT See Automatic Line Insulation Testing. all-dielectric cable A cable consisting of dielectric

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Alford Antenna Patented Design Examples Andrew Alford was a significant pioneering inventor of many types of antennas, several of which bear his name. This is a brief selection of some of the innovative patented designs developed by Alford in the 1940s. Many of the concepts pioneered by Alford are still used today.

A portion of the patent for an electronic beacon modulator submitted in 1941 and granted U.S. patent #2,310,202, in 1943.

A portion of the patent for a wing-type dipole antenna granted to Alford in 1963 as #3,114,913.

A portion of the patent for a loop antenna submitted by Alford, in 1946, and awarded patent #2,508,085, in May 1950.

A patent for an ‘island antenna’ designed for installation on aircraft granted to Alford and two co-inventors in 1963 as #3,086,204.

materials (insulating materials) that has no metal conductors as are found in most conventional cables. all-wave antenna A multipurpose antenna designed to broadcast and/or receive a wide range of frequencies. All-wave antennas may include a number of different types of receiving structures on one basic supporting structure, and even better may be possible through careful antenna alignment (i.e., it may tilt or rotate manually, or electronically on servos). All Call Paging A capability enabling a spoken message to be broadcast through a phone system, to all speakers and phones on that system. See hoot’n’holler. all number calling Most people are now familiar with phone addresses consisting entirely of numbers, but in older phone systems in many regions of North America, a unique phone ID consisted of two letters, usually indicating the region or neighborhood, followed by five numbers. Thus, the number 525-1234 would have been called Larch 51234, Ladysmith 51234, LA 51234 or something to that effect. This was a somewhat more poetic and easy-to-remember system than the current all number system. All number calling was instituted to provide more numbers, as human populations and the demand for phone lines increased. In most areas, all number calling was in place by the 1960s. Since numbers are difficult for many people to remember, companies often request “gold numbers,” numbers that correspond to letters which spell out the name of the company or some aspect of its service. all routes broadcast ARB. One of two types of route discovery frames that are common, namely all routes broadcast (ARB) and single route broadcast (SRB). In frame-based networks such as Token-Ring networks, ARB is a common method of source routing in which a message is carried in an all routes broadcast (ARB) frame, and every possible route is traversed between the end stations. For efficiency, a spanning tree structure is typically used to organize the routing pattern. See all routes broadcast. all routes explorer ARE. In ATM networks, a means of sending a transmission through all possible routes, which is useful for exploring paths for future transmissions. In source routing, an explorer frame is sent out to determine a path to a given destination. There are all routes and spanning tree explorer frames. See all routes broadcast. all trunks busy ATB. A telephony trunk group condition wherein all the trunks in the group are busy. Statistical reports are generated indicating how often the condition occurs and the duration of ATB conditions. A tone indicator or recording may be provided to a caller indicating that all trunks in a specific routing group are unavailable. The tone sequence sounds like a fast busy signal. ALLC See Association for Literary and Linguistic Computing. Allen, Paul (1953- ) The renowned cofounder of Microsoft Incorporated, Paul Allen was Bill Gates’ teenage Seattle high school friend and business partner, and he co-authored a number of early program-

ming projects with Gates. Together they founded Traf-O-Data around 1972 and worked on commercial programming contracts. Allen discussed a number of ideas for creating and selling microcomputers with Gates, but Gates didn’t get as fired up about hardware ideas as he did about software, and these ventures were not aggressively pursued. After graduation, Gates went to Harvard and Allen took a job with Honeywell in Boston. When Allen was in Harvard Square, he learned of the Altair computer from the January 1975 issue of Popular Electronics magazine. He and Gates discussed the article together and conceived the idea of developing a BASIC interpreter for the MITS Altair. Apparently others had called MITS with a similar idea. Allen and Gates had previously had access to computer code for a BASIC interpreter when they were working at Dartmouth, so Allen developed a simulation environment for the 8080 processor on a DEC PDP computer, and he and Gates developed a BASIC interpreter in a few weeks. Allen flew to the MITS offices in New Mexico to demonstrate the software and, remarkably, it worked the second time they fed the tape through the machine. Gates and Allen moved their business to Albuquerque to work in cooperation with MITS, and Allen became their VP of Software. Allen always had an interest in hardware as well as software, and when the transition from 8-bit to 16-bit machines was taking place, Allen originated the idea of the Apple SoftCard emulator, to straddle the two markets, and to provide greater flexibility while Microsoft moved into 16-bit software development. The single most important alliance in Microsoft history was the contract to develop an operating system for International Business Machines (IBM), under controversial and competitive circumstances with Gary Kildall, the developer of the CP/M operating system. The text-based QDOS system, based upon a mid-1970s manual for Kildall’s CP/M, was their flagship to success. They purchased QDOS, developed by Tim Paterson, and developed it into PC-DOS for IBM and MS-DOS for Microsoft. Later Paul Allen left Microsoft to pursue other interests, including investments in a number of ventures, and in 1994 he founded the Paul Allen Group to monitor the performance of the various companies in which he has significant investments. He maintains regular contacts with the investment, computer, and entertainment communities. See Altair; Gates, William H.; Microsoft BASIC; Microsoft Incorporated. Alliance of Computer-Based Telephony Application Suppliers ACTAS. A trade organization established to promote the distribution and development of computer-based telephone applications and standards. ACTA is associated with the Multimedia Telecommunications Association (MMTA). Alliance for Better Campaigns A public interest group founded in 1998 to improve public participation in elections by promoting campaigns in which the greatest number of voters could be reached in the most engaging way. As would be expected, broadcast telecommunications media are central to many

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of the Alliance’s aims. The Alliance supported a recommendation by the Gore Commission in 1998 to support the voluntary provision of airtime for campaign messages, particularly in the month leading up to a campaign. The Gore Commission further exhorted the Federal Communications Commission (FCC) to bring their jurisdiction into play if broadcasters did not voluntarily comply with the provision of air time for these campaign messages. See Advisory Committee on the Public Interest Obligations of Digital Broadcasters. http://www.bettercampaigns.org/ Alliance for Telecommunications Industry Solutions ATIS. An organization of industry professionals from North America and World Zone 1 Caribbean service providers. ATIS was initially the Exchange Carriers Standards Association (ECSA) in 1983, when it was created as part of the Bell System divestiture. It became ATIS in 1993. ATIS is concerned with a variety of issues ranging from telecommunications protocols and interconnection standards to general administrative operations of systems among competing carriers. ATIS has cooperated on many projects with the U.S. Federal Communications Commission (FCC). See Committee T1, Ordering and Billing Forum. http://www.atis.org/ alligator clip A long-nosed metal pressure clip with small teeth on the inner surface of the clip for grasping small objects or wires. Often two clips are mounted on a firm base to make them free-standing. They are commonly used in electronics to hold wires and various components, especially for soldering, or for establishing temporary electrical connections. They are also used to secure badges to clothing or baggage where a firm, temporary connection is needed. allocate To apportion or earmark for a specific purpose. Resource allocation is an important aspect of computer and network operations. Memory, storage space, CPU time, and printers are queued and prioritized as part of the allocation process. Allocation is also essential to broadcasting and two-way radio communications, as there are only a limited number of frequencies available, and these must be carefully administrated to avoid interference and to maximize the number of regions in which they can be reused. alloy A combination of a metal or metals with nonmetals, or of metal with metal, accomplished through the intimate fusing or amalgamation of the components. Alloys are often created to combine the better qualities of the components. For example, blending gold with a stronger metal provides the greater malleability and beauty of gold with the greater durability of the alloyed metal. ALM 1. airline miles. See air miles. 2. AppWare loadable module. 3. automated loan machine. A type of commercial access point, similar to withdrawal ATMs, in which financial services in the form of quick loans can be negotiated through an automated teller machine. almanac 1. Publication containing astronomical and meteorological data useful for navigation/position-

ing technology. 2. A file detailing satellite orbits and related atmosphere and time information. alnico An iron alloy with aluminum, nickel, and cobalt, sometimes with various combinations of cobalt, copper, and titanium added. It is commonly used to make permanent magnets, used in many electronics components including speakers, motors, meters, etc. Alouette-I, Alouette-A Canada’s first research satellite, launched in September 1962, to study radio communications in the northern reaches and the ionosphere. The project originated at the Defence Research Telecommunications Establishment. A Thor-Agena launch vehicle was used to place the satellite in orbit. Alouette somewhat resembled a fat metal pumpkin with slender antennas spiking out of the top and sides. The Alouette was followed by the International Satellites for Ionospheric Studies (ISIS) program in which Canada and the U.S. jointly developed several more satellites. Three years after Alouette-I, the Alouette-II was launched. AlouetteI operations were terminated September 1972, Alouette-II similarly lasted 10 years. The follow-up ISIS-I and ISIS-II satellites were in orbit for 20 years each. A huge number of scientific papers and many volumes of scientific sounding data were produced as a result of these long-lived projects. See ANIK. ALOHA A method of radio wave transmission in which transmission can occur at any time. This means many transmissions may happen simultaneously and may cause interference, but sometimes it’s a practical way to deal with unusual situations. The basic idea is to send out a signal, see if there’s a response, and if there isn’t, send again. Pure ALOHA and slotted ALOHA are variations. Pure ALOHA is very much a free-for-all and has been used for packet radio communications since the early 1970s. It has a low capacity rate, usually only about 18%. In slotted ALOHA, the transmissions are slotted according to time access, which may provide about double capacity of pure ALOHA. The name is derived from a failing satellite whose use was donated to researchers in the South Pacific. Since capacity outstripped demand, the loose ALOHA method fitted the circumstances. ALOHANET An experimental frequency modulation (FM) transmission in which data frames are broadcast to a specific destination, developed by the University of Hawaii. See Aloha, packet radio. alpha channel A portion of a data path, usually the first 8 bits in a 32-bit path, which is used with 24and 32-bit graphics adapters to control colors. Popular paint programs like Adobe Photoshop allow the contents of alpha channels to be individually manipulated to create special effects. alpha testing In-house testing of software or hardware. In software alpha testing, employees attempt to find and eradicate all the bugs, flow control, and user interface issues that can be determined by internal staff. See beta test. Alphanet Telecom A new Internet protocol-based long-distance company based in Toronto, Canada. Phone, fax, and data transmissions will be jointly

available as IP-based calling services leased through private carriers. alphanumeric A set of characters comprising the upper and lower case letters of the English alphabet from A to Z, and the numerals 0 to 9. On some devices, lower case letters may not be included. alphanumeric display A very common, usually inexpensive type of display on consumer appliances and electronics in which basic letters and numbers, and sometimes a few symbols, can be seen well enough to be understood for simple tasks. Alphanumeric displays are commonly based on liquid crystal diode (LCD) or light emitting diode (LED) technology. Alphanumeric displays are used in digital clock radios, microwaves, calculators, music components, handheld computers, and many other items. ALPS See automatic loop protection switching. ALT See automated loop test. Altair 1971 is the year that commercial distribution of personal computers really began, when the Kenbak-1 Digital Computer was advertised in the September issue of Scientific American magazine. Thereafter, a steady trickle of assembled units and kits, including the Micral, Mark-8 and Scelbi-8H, foreshadowed the growing interest in hobbyist and home computers. None of these predecessors to the Altair sold in significant numbers. Then, at the end of 1974, Edward Roberts’ MITS company introduced the Altair 8800, which was featured on the January 1975 cover of Popular Electronics magazine. This exposure was a significant boost to its visibility. International Business Machines (IBM) released the 5100, the first significant corporate competitor, the same year, but it failed to catch on and was quickly forgotten. The Altair was designed by Roberts, William Yates, and Jim Bybee. The introductory price for the first three months was $395 for the kit, and $650 for a fully assembled unit. Programming was accomplished by means of small dip switches on the front of the computer; if the power was interrupted, the programmer had to start all over again and the available memory was infinitesimal by today’s standards, only 256 bytes. It featured an 8-bit Intel 8008 central processing unit (CPU) and room for the addition of up to 15 peripheral cards. Later Altair-compatible buses incorporated Intel’s upgrade to the 8008, the 8080, which was significantly faster. Through marketing, a little luck, and the growing interest of electronics hobbyists, the Altair line was the first to capture successfully the hearts and imaginations of computer pioneers, and Micro Instrumentation and Telemetry Systems (MITS) sold more than 40,000 units by the time the company was sold in 1978. The Altair was a history-making invention; despite its modest capabilities, it became wildly popular with insightful hobbyists who grasped its potential and significance. The Altair bus, more commonly remembered as the S-100 bus, was quickly copied, and a number of clones, most notably the IMSAI 8080, began to appear. MITS set to work adding to its prod-

uct line, creating a Motorola-based version, the Altair 680. The mass market computer had been born, and the industry quickly shifted into high gear, with far-reaching changes to society. Paul Allen and Bill Gates, friends not long out of high school at the time of the release of the Altair, provided MITS with a BASIC interpreter just in time for it to be included with fully assembled versions of the machine, thus launching Microsoft Incorporated, the world’s best-known software company. Steve Wozniak, inspired by the little kit computer, designed his own computer circuit board and, with Steve Jobs, formed Apple Computer, Inc., another of the world’s most successful computer hardware/ software companies. See Alto, Geniac, Intel MCS4, Kenbak-1, IMSAI 8080, LINC, Mark-8, Micral, MITS, Scelbi-8H, Simon, Sol, SPHERE System, STPC 6800, TMS 1000.

The Altair 8800 was available assembled or as a kit from MITS, a New Mexico-based company. It was introduced late in 1974 and was prominently featured in the January 1975 issue of Popular Electronics.

The November 1975 issue of Popular Electronics featured an article on building the Motorola MC6800based Altair 680 by Edward Roberts and Paul Van Baalen. This was likely a strong factor in introducing the Motorola MC6800 CPU to hobbyist hardware designers.

Altair 680 A Motorola and American Micro-Systems, Inc. 6800 CPU-based computer from MITS, the same company which released the Intel 8008based Altair a little less than a year earlier. The Altair 680 was featured in an article in the November 1975 issue of Popular Electronics as having a builtin TTY interface, a capacity of 72 program instructions, and room for up to five interface cards. The 680 was intended to appeal to hobbyists who liked the architecture of the MC 6800, and who were

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looking for a smaller, less expensive kit to build. The 680 was less than a third of the size of the Altair 8800 and much less expensive to build. See Altair. Altair bus The original data bus that was developed by MITS for the Altair computer line. Later vendors changed the name to S-100 bus, and it became common in many different computers in the late 1970s and early 1980s. Altair Users Group, Virtual There is a Virtual Altair Users Group on the Internet, comprised of hobbyists who still build, repair, and operate Altair computers. One of the participants, Tom Davidson, hosts an excellent Web site with schematics and circuit board images. http://hyperweb.com/altair AltaVista One of the major World Wide Web search engines on the Internet, AltaVista draws from one of the larger Web database catalogs online. It was started by Louis Monier in Spring 1995 and was made a public search resource in December 1995. In June 1998 it was acquired by Compaq. A year later, a majority share was purchased by CMGI, Inc. http://www.altavista.com/ alternate access carriers A telephone service vendor other than the Local Exchange Carrier (LEC) can be authorized under competitive Federal Communications Commission (FCC) guidelines to provide alternate access. Alternate Billing Services ABS. Telephony services that permit collect or bill-to-another-number services to callers. ABS is especially applicable to long-distance calls. Alternate Billing Entity Codes (ABEC) are an administrative tool used more specifically by Inter Exchange Carriers (IECs) to bill third parties for long-distance services. Some Billing Services providers provide code administration for ABEC. Alternate Mark Inversion AMI. A line transmission code used for T1 and E1 lines in which successive marks alternate in polarity (negative and positive). This bipolar signal format is used on DS-1 lines, for example. A mark or a 1 is represented by alternating negative (minus) and positive (plus) voltages, with neutral representing zero. If two of the same signals occur in succession, a bipolar violation (BPV) occurs. The ones density requirement on lines using the AMI signal format are typically either B8ZS or HDB3. See B8ZS, bipolar signal, Coded Mark Inversion, HDB3. Alternate Regulatory Framework ARF. A means of regulating local telephone companies intended to further competition within Local Access Transport Areas (LATAs). Since 1987, it has been called the New Regulatory Framework. alternate route AR. An alternate data or telephone communications route selected when the initial choice is unavailable due to load or a break in the path. In telephony, sometimes called second-choice route. alternate routing In both circuit switching and packet switching network systems, there are times when the initial attempt to trace and complete a transaction between a sender and the destination is unsuccessful. This situation can be due to high traffic,

compromised intermediary switching links, destinations that are unavailable, etc. In most circuit switching implementations, the transmission cannot go through until an end-to-end connection is set up, dedicating an established path to the call, so alternate routing to find another way to connect the requested call must take place before any data (or voice, in the case of a phone call) can be sent. In telephony, alternate routing usually involves locating a less busy trunk. In contrast to circuit switching, packet switching does not require the establishment of an end-to-end connection before data can be sent; it can be sent regardless of whether it is known if the destination is reachable or available. Packet switching is used in dynamic environments where it is not known, or cannot be known, which routing nodes may be available, which route is most efficient, and whether the destination is online at any particular time. The packets are sent by various means, usually through hopby-hop systems, and the packets from an individual message may be broken up and sent through different routes if a bottleneck or break occurs in the original path. At the destination, separated packets are reassembled, and there are usually several attempts to deliver the information before it is returned (in the case of most email) or abandoned (in the case of lowpriority data). To facilitate alternate routing, packet system routers may have extensive routing tables listing a wide variety of connections within that region of the network. See router. alternate use AU. The capability of a communications system to switch from one mode of service to another, e.g., between data and voice. See alternate voice/data. alternate voice/data AVD. A transmission system that can be used for voice and data over one line, by alternating the services as needed, usually switched manually, as between voice through a telephone or data through a modem. Some modems are equipped with speakerphone capability to allow switching between voice and data, and further to detect the mode of an incoming transmission in order to switch to the correct mode automatically. More flexible and sophisticated systems are always being developed, and some success with newer, faster modems has been achieved to allow simultaneous voice/data communications. See simultaneous voice/data. alternating current AC, ac. A very commonly used form of electrical current with a periodically reversing charge-flow with an average value of zero. Unlike direct current (DC), alternating current (AC) varies continuously in its magnitude. For the supply of electricity to businesses and residences, it is set to reverse about 50 to 60 times per second, depending upon regional electrical codes. Voltages in North America are supplied as 120 plus or minus about 10% for regular wall outlets, and to 220 for heavy duty outlets (for dryers, stoves, etc.). Voltages in Western Europe are set to 220. Alternating current is typically used in commercial and residential power circuits leading to wall

sockets, whereas direct current is typically used in battery-operated devices and sensitive electronic components. The large converters/transformers attached to the power cords of small components such as modems convert the AC power from the wall circuit to DC power compatible with the component. Given the greater sensitivity of electronic components, plugs now commonly have one wide leg and one narrow leg, to correspond with wider and narrower holes in newer wall or extension cord sockets. The wider and narrower pins correspond to the different characteristics of the wires to which they are connected, with one being a hot or live wire, and the other being a neutral or grounded wire. Much of early communications technology was based on direct current (DC) as a power source. Telephones had talking batteries and common batteries. These batteries were large, leaky, wet cells, which were inconvenient if moved or exposed to fluctuating temperatures. Surprisingly, Thomas Edison was opposed to alternating current for the power supply for communications circuits, and hotly contested the concept with Nikola Tesla. More than fifty years after the invention of the telegraph, AC power for telegraph systems was still considered a novel idea, but the shortage of batteries, and their high cost, provoked French and Swiss engineers to experiment with AC generators, as described in the Annales des Posts, Télégraphes et Téléphones in September 1919. Eventually the advantages of AC power were better understood, and its use became common. See B battery; direct current; ground; impedance; surge suppressor; talking battery; Tessla, Nikola. alternator An electronic or electromagnetic device for producing alternating current. altimeter An instrument for measuring altitude. Altimeters are essential in aviation, and not uncommon in cars. There are also handheld and wrist-worn altimeters for researchers, forest service workers, and mountain climbers. Many altimeters are based on the same principles as barometers, using relative pressure (usually set initially at sea level) as a means of showing changes in pressure, and hence altitude. Since pressure changes, altimeters must be adjusted. Global Positioning System (GPS) consoles can provide information on location and altitude that is derived from satellite data and is not dependent on air pressure. Radio altimeters, developed in the late 1930s at Bell Laboratories, indicate distance above ground by reflecting frequency modulated (FM) radio signals off the surface of the Earth, and measuring the reflections. See barometer, Global Positioning System. Alto A pioneering computing system developed at the Xerox PARC laboratories around 1973. The Alto was the inspiration for the graphical user interface incorporated into the Macintosh line of computers, and later into Microsoft windowing software. Some argue that the Alto was the first microcomputer, but that honor really belongs to the Kenbak-1 (1971), or perhaps the Simon (1949, 1950), and the commer-

cially successful Altair (1974), since the Alto was never available to the general public in its original form, and its price tag was thousands of dollars. Nevertheless, many of the revolutionary graphical user interface ideas that filtered out to the commercial world were developed and implemented on the Alto. See Altair; Kay, Alan; Kenbak-1; Macintosh computer; Microsoft Windows; Simon; Xerox PARC. ALU 1. arithmetic and logic unit. An integral part of most computer processors’ logic architecture for performing operations. 2. See average line utilization. aluminum A silvery, dull, malleable, light, inexpensive metallic element with good electrical conductivity and resistance to oxidation. Aluminum is somewhat brittle but is still commonly used in cables, antennas, reflectors, and other communicationsrelated structures. AM 1. See access module. 2. active messages. 3. active monitor. 4. See amplitude modulation. AM broadcasting Transmission through amplitude modulation technologies on approved AM frequencies with the appropriate AM broadcasting license. In the United States, AM stations are spaced at 10 kHz intervals, ranging from 540 to 1700 kHz. See amplitude modulation, band allocations, broadcasting, FM broadcasting. AM/VSB amplitude modulated vestigial sideband. See modulation, sideband. amalgam n. Blend, composite, alloy, mixture. amalgamate v.t. Unite, blend, consolidate, or merge. For example, amalgamating metals may help reduce the effects of chemical deterioration. AMANDDA, AMANDA Automated Messaging and Directory Assistance. amateur bands Frequency spectra set aside by regulatory authorities for the use of amateur radio operators. These are geographically subdivided, with some ranges designated for international use. Not all countries permit broadcasts by amateurs, licensed or unlicensed. In the U.S., the airwaves are legally owned by the American people and licensed in trust to qualified individuals and groups through the Federal Communications Commission (FCC). amateur call sign A set of identification characters licensed to amateur broadcasters by a regulating agency such as the U.S. Federal Communications Commission (FCC). Call signs in the U.S. indicate the country and region of the licensee. Amateur Packet Radio Network AmprNet. A network of amateur packet radio hosts using TCP/IP network transmissions protocols with addresses assigned in the .ampr.org domain. The sharing of packet radio communications among amateur radio buffs began with packet bulletin board systems (PBBSs) similar to the BBSs that were being used by computer hobbyists in the early and mid1980s. The main differences between the two were that computer BBSs were primarily interconnected by land-based telephone lines and modems, whereas packet radio BBSs were interconnected by wireless

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radio frequency communications through terminal node controllers (TNCs) with a broadcast distance of about 20 miles or so. Relays were still necessary for long-distance packet communications. When the Internet and TCP/IP became well established, many computer buffs shut down their BBSs and migrated to the Internet. Packet radio followed suit, forming the AmprNet to take advantage of lowcost global airwaves and simultaneous two-way communications to exchange messages. Amateur Radio Emergency Service ARES. A public service organization of licensed Amateur Radio Operators of the American Radio Relay League (ARRL) who voluntarily provide emergency communications for public service events. ARES cooperates with state and local governments and the American Red Cross. http://www.ares.org/ Amateur Radio International Space Station ARISS. An organization established to research and support the use of amateur radio in space; ARISS evolved out of the Space Shuttle Amateur Radio Experiment (SAREX). It serves as an educational outreach tool and an experimental communications testbed. It also provides backup for emergency space communications and a medium for “off-duty” communication with friends and family members. A Memorandum of Understanding was signed between ARISS and various national radio organizations in 1996 along with agreements with NASA and the Russian Energia. NASA liaises with the public through its Division of Education programs and Web site. Leadership and consultation are provided by the ARRL and AMSAT. ARISS designs, builds, and operates amateur radio equipment in cooperation with International Space Station programs. It established ISS Ham as a technical team to support hardware development, training, and operations while in orbit. While the initial communications of SAREX and ARISS were audio only, video is also an important aspect of radio communications and slow scan television (SSTV) is included in ARISS projections. See Space Shuttle Amateur Radio Experiment. http://ariss.gsfc.nasa.gov/ amateur radio operator, ham radio operator A radio broadcasting hobbyist permitted to transmit radio signals over specific frequencies. Most licenses that permit amateur transmissions require that the operator be licensed and fulfill certain requirements. In the U.S., also often called ham radio operator. amateur satellite service A radio communication service using space stations or Earth-orbiting satellites for the purposes of the amateur radiocommunications service. See amateur service, AMSAT, OSCAR. See AMSAT-OSCAR Satellites Chart. amateur service Radio communications services for the purpose of self-training, intercommunication, and technical investigations carried out by amateurs, that is, licensed or otherwise authorized persons interested in radio technique solely with personal, educational, or nonpecuniary aims. amateur television AmTV, ATV. Black and white or color image broadcasts through amateur radio

frequencies, with or without accompanying sound broadcast. Some amateur enthusiasts prefer to use ATV to mean fast scan TV over amateur bands, and SSTV for slow scan image transmission. With advancements in television technology, advanced television has begun to be identified with the ATV abbreviation, occasionally causing confusion. In the future it may be advisable to use AmTV to designate amateur television. See slow scan television. amber A very light, transparent or semitransparent, warm golden substance arising from the fossilization of tree resin from pine trees that have been extinct for millions of years. Amber floats in water and occasionally washes up on the coasts of Europe after storms, intermingled with kelp and other natural debris. Sometimes insects can be found imbedded in the amber, preserved for centuries. Amber can be highly polished and has been used for jewelry for thousands of years. The chief importance of amber to telecommunications is its static electrical properties, which can be observed by rubbing amber with a cloth (or on your hair) and using it to attract small fragments of tissue paper. In fact, the Greeks observed this property, and Plato recorded “... the wonderful attracting power of amber ...” in his Timaeus dialog. The Greek word for amber is elektron. ambient n. Environment, atmosphere, mood, surroundings. ambient noise, room noise The general acoustic noise level of an environment, usually measured in decibels. The ambient noise in terminal rooms with printers or other equipment may be sufficient to cause hearing loss over time. Technicians who work long hours with high speed printers should wear ear protection. AMDM ATM multiplexer/demultiplexer. America Online AOL. A large, commercial Internet Services Provider (ISP) that provides access to the Internet, AOL-specific forums, news, email, and other features. AOL evolved from Quantum Computer Services, conceived by S. Case and J. Kimsey as a computer BBS providing online information and consumer services through modems. In 1989 Quantum was renamed to America Online and was launched with realtime chat, email, and special interest forums. Case became President of the company in 1990 and CEO in 1993. AOL became a publicly traded company in 1996. In 1998, it acquired Compuserve and ICQ, two well-known network services, as well as MapQuest, in 2000. In 2001, AOL completed a merger with Time Warner. America’s Carriers Telecommunications Association ACTA. A U.S.-based trade organization, representing commercial long-distance vendors (nondominant interexchange vendors). Of significance is the fact that ACTA has lobbied the Federal Communications Commission (FCC) to bar longdistance digital telephony over the Internet. The focus of ACTA is to provide representation for its members to various legislative and regulatory bodies, and to further the business activities of its members.

American Association for Artificial Intelligence AAAI. A nonprofit organization founded in 1979 to advance education in and scientific understanding of thought and intelligent behavior and their embodiment in machines. http://www.aaai.org/ American Association for the Advancement of Science AAAS. Descended from the Association of American Geologists and Naturalists, the AAAS was formed with a broader mission in 1848 to promote the development of science and engineering in the United States. http://www.aaas.org/ American Association of Physics Teachers AAPT. The AAPT supports professional and research physics and physics education through activities and publications, including the American Journal of Physics, Physics Today, and The Physics Teacher. Physics and engineering (applied physics) are at the heart of the understanding and development of all communications systems. http://www.aapt.org/ American Bell Telephone Company In 1875, the Bell Patent Association was formed by Alexander Graham Bell with investors willing to finance his telegraphy research. Two years later, in 1877, The Bell Telephone Company was formed by Bell, who included his associate, Thomas Watson. The company was formally incorporated in Massachusetts in 1878. Theodore N. Vail was hired as the general manager and had a long association with the company and its successors. In 1878, the Bell Telephone Company and the New England Telephone Company were consolidated into the National Bell Telephone Company. Then, in 1880, American Bell Telephone Company was incorporated. In 1881, American Bell purchased Western Electric Manufacturing Company and developed it into Western Electric Company, the equipment manufacturing arm of American Bell. American Bell was the parent of the American Telephone and Telegraphy Company (AT&T). AT&T was established in New York as a subsidiary in 1885 for handling long-distance calls. These two were then merged into AT&T in 1899. See AT&T; Vail, Theodore N.; Western Electric Company. American Civil Liberties Union ACLU. A prominent, nonprofit, nonpartisan, civil liberties organization founded in 1920 which now has more than 1/4 million members. The ACLU monitors and protects freedom and takes action against violations of civil liberties wherever they may occur. The ACLU has a strong presence on the Web in light of the fact that many new freedom-related legislative actions have been taken as a result of the growth of the Internet. The ACLU publishes ACLU Online and the biweekly Cyber-Liberties Update electronic magazine. The ACLU deals with many telecommunications issues including Web censorship, online privacy, encryption, and more. http://www.aclu.org/ American Communication Association ACA. A not-for-profit association founded to promote academic and professional research, theory, criticism, and debate on human communications. ACA publishes The American Communication Journal, a professional, peer-reviewed, online publication. http://www.americancomm.org/

American Engineering Association AEA. A national nonprofit professional association supporting and promoting American leadership in engineering. http://www.aea.org/ American Electronics Association AeA. A Washington, D.C.-based professional association with offices in the U.S. and abroad, founded in 1943. AeA is dedicated to helping member companies excel in a global competitive market. AeANET is AeA’s means of communicating industry news, surveys, and public policy issues to its membership. In 2001, the AeA presented a public policy report to the 107th U.S. Congress asserting the importance of adapting to a new global Information Age. As its Public Policy priorities, the AeA listed expansion of science and math education, protection of privacy, simplification of Internet taxation, export controls, restoration of Presidential fast-track trade negotiating authority, monitoring of China’s conformance with World Trade Organization (WTO) agreements, and broadband deployment through forbearance in regulation and the promotion of competition. The report further lists statistics for the high-technology industry in the Quick Facts Appendix 3 section. http://www.aeanet.org/ American Institute of Electrical Engineers AIEE. Formed as a result of growing electrical development in the 1800s and the International Electrical Exhibition in 1884, to represent the profession and develop standards for the industry. Norvin Green, president of Western Union Telegraph Company, was the first president. Alexander Graham Bell and Thomas A. Edison were among the first six vice-presidents. AIEE was presented The Clark Collection in 1901 by Schuyler Skaats Wheeler. The Clark Collection was one of the world’s great libraries of electrical technology. Andrew Carnegie further donated $1.5 million for AIEE premises. AIEE was merged with the Institute of Radio Engineers (IRE) in 1963 to form the IEEE. See IEEE, Institute of Radio Engineers. American Library Association ALA. A governing body and support group for American Librarians. The ALA provides member services, workshops, conferences, and administrative support. The organization has a long history of service to the public and its members. The ALA Code of Ethics goes back to a Suggested Code of Ethics proposed in 1930. The author acknowledges the generous help received from many librarians in the creation of this dictionary. http://www.ala.org/ American Mathematical Society AMS. A large professional society dedicated to promoting mathematical research and education, founded in 1888. Headquartered in Providence, R.I., the AMS sponsors conferences, member services, online resources (e.g., MathSciNet) and a large number of mathematical publications. http://www.ams.org/ American Mobile Satellite Corporation AMSC. A commercial provider of seamless mobile communications services across North America under the SkyCell trademark. Hughes Communications is the largest shareholder, joined by AT&T Wireless,

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Singapore Telecom, and Mitel Corporation. A variety of services are marketed to government agencies, emergency organizations, and major corporations. AMSC is permitted to provide domestic mobile satellite services (MSS) in the upper L-band. American Morse Code, Railroad Morse A system of dots and dashes used to represent characters for distance communications, quite possibly developed by Alfred Vail, while working with Samuel Morse. Due to the fact that American Morse includes some characters with internal spaces, which can be confusing to some, it is not often used, International Morse code is preferred. See Morse code. American National Standards Institute ANSI. A significant U.S. private sector, nonprofit, standardspromoting body based in New York. ANSI was founded in 1918 by a group of engineering societies and government agencies. The ANSI Federation contributes the enhancement of global competitiveness of U.S. businesses by promoting the development and support of consensus standards and conformity assessment systems. Information on the many important ANSI standards is available online in the ANSI searchable database. http://www.ansi.org/ American Public Power Association APPA. A national American service organization representing local or publicly-owned electric utility companies. http://www.appanet.org/ American Public Radio See Public Radio International. American Radio Museum A diverse, well-selected collection of over a hundred years history of antique radio and electrical technologies, including a Tesla coil, Nipkow disc, Leyden jars, static generators, phonographs, and significant makes and models of crystal detectors and historic radios. Descended from the Bellingham Radio Museum, the ARM is located in the Pacific Northwest. The founder and curator is Jonathan Winter. http://www.antique-radio.org/radio.html American Radio Relay League ARRL. Founded in 1914 by Hiram Percy Maxim, with assistance from Clarence D. Tuska and a number of their colleagues, the ARRL is now a worldwide organization with almost 200,000 members, headquartered in the United States. Tuska was a youthful tinkerer and radio hobbyist when he met Maxim. The ARRL name is derived from the way in which amateur radio operators, constrained to certain power levels and frequencies, would cooperate by relaying messages from one person to another in order to send over greater distances or difficult terrain. The ARRL cooperates with various radio groups and governing authorities such as the International Telecommunications Union (ITU) and the Federal Communications Commission (FCC). Its members have contributed to many of the technological milestones in communications history, including the pioneering of frequencies that were originally thought to be useless (and hence were assigned to amateurs). More recently, amateur radio enthusiasts have cooperated in satellite communications projects with AMSAT.

The ARRL monthly publication QST has been available for more than 80 years. See AMSAT, International Amateur Radio Union. The ARRL’s call letters are W1AW. http://www.arrl.org/

QST has been published for its members by the American Radio Relay League (ARRL) since 1914.

American Sign Language Ameslan. A system of gestures to indicate words, phrases, and letters without speech over short distances or, if televised, over long distances. Ameslan is a specific variation of sign language. When you see “Closed Captioned for the Hearing Impaired” on the corner of a broadcast television program, it indicates that sign language interpretation of the speech content of a program is available as an optional service. Used primarily for instruction and communication among the deaf, sign languages are also useful in environments with much noise, where earphones are used, or where quiet is important (e.g., recording studios). Ameslan is a very expressive and often aesthetic mode of communication which employs a characteristic grammar and syntax different from English. Gestural sign languages are more universal than spoken or written languages because they incorporate many intuitive and cross-cultural modes of physical expression. Speech through signing, in general, is more readily learned by many children than spoken language, with some children learning to communicate simple concepts through basic gestures at six to 12 months of age. Signing can also be used to communicate with learning disabled or autistic children, some of whom may have difficulty acquiring spoken language skills. While signing is primarily visual, it is also useful for individuals who are both blind and deaf. Helen Keller, who was befriended by Alexander Graham Bell, is the most well-known example of a blind and deaf person who learned to communicate with her tactile senses, through signed letters spelled into her hand, or by her into the hand of another. American Speaking Telephone Company A historic telephone company, based upon the Edison

transmitter, established by Western Union in 1877 to compete with the Bell Company. With hundreds of thousands of miles of telegraph lines already installed throughout North America, that could be adapted for telephone transmissions, Western Union was seen as a real threat to the Bell empire. American Standard Code for Information Interchange ASCII. An important, alphanumeric 7-bit (128-character) communications standard widely used around the world for the transmission of textual messages. ASCII is a simple system, used on telegraph systems and computers. It doesn’t support formatting attributes such as bold, italic or underline, and it is primarily useful for English and western European languages. ASCII often functions as a lowest common denominator for textual communications since it is supported by most electronic mail, word processing, text editing, and desktop publishing programs, which may otherwise be incompatible. Differing formats are often resolved through ASCII translation and conversion. See ASCII for a chart showing the characters, control characters, and hex, decimal, and octal values for each. See ASCII and see Appendix for a chart, EBCDIC. American Telephone and Telegraph Company AT&T. See AT&T for an explanation of the company’s origins, history, and technologies. American Voice Input/Output Society AVIOS. A not-for-profit organization dedicated to promoting and supporting speech applications research and technologies. Speech applications include voice recognition, speech recognition, and speech generation, all of which are now important input and output capabilities of computer systems and digital telephony networks. http://www.avios.com/ American Wire Gauge, Brown and Sharpe Wire Gauge AWG. A standardized wire diameter measuring system, exclusive of covering, for nonferrous conductors such as copper and aluminum. With a range from 1 to 40, lower numbers denote thicker wires, higher ones denote thinner wires. Generally, for a specific material, the current-carrying capability increases as the diameter of the wire increases and the AWG number decreases. AWG 1 corresponds to a diameter of 7.35 mm with an amp rating of ca. 191, while AWG 40 corresponds to 0.799 mm and an amp rating of ca. 0.02. With finer wires manufactured and used for finely detailed electronics circuits, some charts extend the gauge sizes down to 0000 (11.68 mm). Since heavier wires are usually more expensive, consumers tend to purchase the thinnest wire that will accomplish the task at hand. It’s important to get wire that not only is adequate to carry the current desired, but that is strong enough to bend and stretch, especially around connectors, panels, punch-down blocks, etc. If the wire breaks at the connection point, it’s not very useful. See Birmington Wire Gauge. Ames Research Center ARC. A research organization dedicated to creating new knowledge and technologies within NASA’s areas of interest. ARC was formed in 1939 by the U.S. National Advisory Com-

mittee on Aeronautics (NACA), which became part of National Aeronautics and Space Administration (NASA) in 1958. Ameslan See American Sign Language. AMHS See Automated Message Handling System. AMI 1. See Alternate Mark Inversion. Amiga computer A remarkable personal computer system for its time, the Amiga was developed by Jay Miner (hardware), Carl Sassenrath, R.J. Mical, and others in the early 1980s. The original Amiga team members were part of the Hi-Toro company, a small development company whose members created the Lorraine, which was bought out by Commodore Business Machines in the fall of 1984 and developed into the Amiga. Commodore shipped the Amiga 1000 a year later with limited memory and no expansion slots. These compromises were presumably to keep the price down, although Jay Miner, the hardware developer, and Father of the Amiga envisioned the Amiga 1000 with a megabyte of memory and several expansion slots. The Amiga was well equipped for 1985 with full serial, parallel, and joystick ports, full-color graphics, the ability to run multiple screens simultaneously in different resolutions, NTSC video compatibility, built-in 4-channel (16-voice) stereo sound, fast graphics display with coprocessing chips, and a Motorola MC68000 CPU chip running at 7.15909 MHz with 32/16-bit internal/external addressing. The Amiga had a fully preemptive multitasking operating system (working quite well in only 256 kilobytes of memory) which came with both a graphical user interface (GUI) and a text command line interface, both available for use at the same time. It helps to remember that in 1985 most personal computers lacked peripheral ports and employed singletasking, monochrome graphics, and command line interfaces for prices ranging from $3,000 to $6,000. The Amiga 1000 offered everything built in, including monitor and sound, for under $2,000. The only other computer at the time significantly competitive with the Amiga was the Atari ST (the Apple IIgs never quite made the grade). Other Amiga models, including the 2000, 3000 and 4000, and updates to the OS were released over the next several years, followed by a new type of product from Commodore, the CD32. At first the Amiga was hotly competitive with the Atari 520ST, which also supported good sound and graphics. Eventually, approximately five million Amigas were sold worldwide, many configured by NewTek as Video Toaster systems, thus launching the desktop video industry. Just as the Amiga was hitting its stride and had found a strong commercial niche as the platform for desktop video, Commodore-Amiga folded, an unfortunate blow to the future of the technology. The Amiga is historically significant not only for providing the first viable platform for desktop video, but for its many capabilities that have subsequently been incorporated into other systems (certain patented aspects of the Amiga have been used by

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prominent computer companies in today’s mainstream products), showing the prescience and desirability of its design and features. Even a decade after its release, most personal computers lacked many of the Amiga’s early capabilities, despite faster CPUs and other advances in technology.

AML 1. See Actual Measured Loss. 2. analog microwave link. 3. ARC Macro Language. A line-based interpreted programming language for the ArcInfo GIS, from ESRI. 4. Aurora Macro Language. An object-oriented, event-driven language for the Aurora Editor, a text editor from nText Research. AMLCD active matrix liquid crystal display. See active matrix display. ammeter, ampere meter An instrument for measuring the flow of electric current in alternating or direct current in ampere units. In communications circuits, where current may be very small (below one ampere), milliammeters and microammeters are used. When used as a measuring and diagnostic instrument, an ammeter is connected in series with a circuit to measure the current as it passes through. If the total current is above the range of the ammeter, or is such that it might cause damage to the sensitive instrumentation, part of it may be predirected through a shunt connected in parallel. See ampere, shunt.

The first of the Amiga line of computers, the Amiga 1000 was released in August 1985. It featured preemptive multitasking, built-in serial and parallel ports, a Motorola MC68000 CPU with coprocessor chips, two mouse/joystick ports, composite or RGB color graphics up to 640 x 400 pixels (more in overscan mode), and two-channel (16-voice) stereo sound.

Despite the popularity of the computer, CommodoreAmiga folded in 1994 due to problems in executive management and marketing. The Amiga product line was acquired by a German company, Escom, AG, (Amiga Technologies) and was later sold to Gateway, Inc., in 1997. Developers’ conferences were reinstituted the same year. Gateway subsequently licensed use of the technology and trade identifiers to Amino Development Corporation, later known as the Amiga Corporation. Amiga conferences were still being held as of March 2001. See Amiga CD32; Commodore Business Machines; Mindset computer; Miner, Jay. Amiga CD32 This MPEG 68EC020-based computer/game console released in 1993 was the last product promoted by Commodore, Inc., before it was bought out by Amiga Technologies. The small, sub$350 unit was capable of playing standard MPEG, CDTV, and CD-I video CDs off the shelf and could function as an Amiga computer with an optional infrared keyboard. The CD32 supported 24-bit color, at resolutions up to 1280 x 512 pixels, and 8-bit stereo sound, with 18-bit CD-DA. The CD32 came with a game controller and built-in CD player. It was one of the first commercial systems to provide MPEG capabilities at 352 x 288 at 25 fps in PAL mode, and a little less in NTSC mode. S-Video, composite video, and radio frequency (RF) output were provided. See Amiga computer. AMIS See Audio Messaging Interchange Specification.

Historic drawings are often useful for understanding basic mechanics and electronics. The above diagram shows the basic structure and components of a historic ammeter. The ammeter is descended from the galvanometer. [Popular Mechanics, May 1907. ]

AMN See Abstract Machine Notation. AMP See advanced metal powder. ampacity The current-carrying capability, in amperes, of a circuit or cable. Typically ampacity is specified in product descriptions to indicate various types of cable assemblies, which may collectively consist of various combinations of wires and insulating materials. AMPAS See Academy of Motion Picture Arts and Sciences. ampere, amp (symb. – A) A unit of measurement of flow of electric current, named after A. Ampère. It is a practical meter-kilogram-second unit of electric current equivalent to a flow of one coulomb per second, or to the steady current produced by one volt when applied across a resistance of one ohm. The international ampere was traditionally expressed as the steady current that will deposit silver at the rate of 0.001118 grams per second when flowing through a neutral silver nitrate solution. The accepted scientific definition has since been replaced by a SI unit of electric current defined as a

constant current that, in two straight parallel infinite conductors of negligible cross section placed one meter apart in a vacuum, would produce a force between conductors of 2 x 10-7N m-1. See volt, watt. Ampère, André-Marie (1775-1836) A French physicist and mathematician who described and developed terminology for the nature of electricity. He also sought, in 1820, to formulate a combined theory of magnetism and electricity following some of the investigations of H. C. Ørsted. In 1826, Ampère published an important paper, the “Memoir on the Mathematical Theory of Electrodynamic Phenomena, Uniquely Deduced from Experience” in which he described electrodynamic forces in mathematical terms. Many later experimenters built on Ampère’s ideas, and his discoveries led to the development of magnet-moving coil instruments. The ampere unit of measure of electric current is named after him. See ampere, galvanometer.

André-Marie Ampère was inspired by the discoveries of Ørsted and worked with Arago to follow them up. Together they further investigated electrical and magnetic forces from which Ampère sought to formulate a unified theory to explain these phenomena.

Ampère’s rule Based on his discoveries in electromagnetism, André-Marie Ampère described a method for determining the direction in which a magnetic needle orients itself when in the vicinity of a current of electricity. See left-hand rule, right-hand rule. ampere-second A unit of electric charge flowing past a point in a current-carrying wire per second with a constant current of one ampere. Thus, amperes times seconds equals coulombs. See coulomb. amplifier A device or system that increases the magnitude or intensity of a phenomenon such as sound. This is accomplished in electronics through an increase in power, voltage, or current. Amplifying a signal doesn’t necessarily make it louder, bigger, brighter, etc. than the original. The effect of amplification at the receiving end, or at a transfer point, may increase the signal that is received above its characteristics at the point it is received, but not

necessarily above the original. Some systems are intended to increase the signal above the level of the original, as in public address systems and blow horns. Amplification systems seek to minimize the possible amplification or introduction of noise in the signal, while increasing the meaningful parts of the signal. See regenerative relay. amplitude 1. The measure of the magnitude or extent of some property, movement, or phenomenon. 2. The magnitude of variation in some changing quantity from an established value such as zero, or from its extents. See amplitude modulation. 3. In a diagrammatic representation of a wave, the measure of the magnitude from the highest point in the waveform, to the lowest. amplitude distortion Assuming a fundamental wave in a steady-state system, an undesirable condition in which the outgoing waveform differs from the incoming waveform sufficiently to affect the perception or informational content of the signal. amplitude equalizer Corrective electronics, usually passive, designed to compensate for less than desirable amplitudes over a range of frequencies. Equalizers are used in audio recording and playback, especially for music. amplitude fading In an amplitude-modulated carrier wave, fading is the attenuation of the amplitude across frequencies, more or less uniformly. amplitude modulation AM. A very common means of adding information to a carrier wave. A basic radio wave carries no information. By varying or modulating the amplitude in a predetermined way, signals can be created which can be reconstructed as data, sound, or images at the receiving end of the transmission. This system was adopted in the early telegraph systems and is familiar in the form of AM radio broadcasts. AM radio typically requires about 10 kilohertz of bandwidth and is more subject to noise than frequency modulated (FM) radio. Designations of AM radio frequencies is under the jurisdiction of the Federal Communications Commission (FCC), and the they have changed from time to time. In 1993, the FCC increased the upper limit of the AM band from 1605 kHz to 1705 kHz. Once frequency modulation (FM) was developed by Armstrong, it was thought that its superiority would overshadow amplitude modulation, but AM radio stations are still common decades later. One of the simplest ways to modulate is to create intervals of current that are either on or off, as in Morse code telegraph communications and some types of binary computer signaling. Most computer modems use amplitude modulation and demodulation to convert from digital computer transmission signals to analog telephone transmission signals, and back again at the receiving modem. Various types of amplitude modulation have been developed, and other nonamplitude modulation techniques exist, such as frequency modulation, in which the frequency of the signal, rather than its amplitude is varied. See absorption modulation, amplitude shift keying, frequency modulation, modem, modulation, quadrature phase shift keying.

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The top amplitude modulation (AM) diagram (A) shows an unmodulated ‘carrier’ signal. The middle (B) shows the signal modulated so that the amplitude varies through time. The bottom (C) shows the ‘modulation envelope’ which conveys useful information, such as magnitude of the modulation.

amplitude separation In television transmissions, the separation of the incoming signal into a video component and a synchronization signal component. amplitude shift keying, intensity modulation, on/off keying ASK. A basic type of modulation that employs a constant-frequency signal, with two different signal levels used to represent binary values. In its simplest form, one state is represented by the lack of presence of the carrier, and the other by the presence of the carrier at a constant amplitude, hence on/off keying (OOK). AmprNet See Amateur Packet Radio Network. AMPS Analog/Advanced Mobile Phone Service. An analog mobile phone service developed by Bell Laboratories in the 1970s. AMPS evolved out of Bell mobile phone services with improved sound quality and features that were installed in the mid- to late1960s. Then, in 1972, a significant patent was awarded which described handoffs during travel between cells, setting the stage for future mobile phone services. AMPS was first implemented in 1978 in the U.S. and Korea. It uses the same bandwidth as a landline voice channel but is modulated onto a frequency-modulated (FM) carrier using frequency division multiple access (FDMA). This system is still a significant analog service but is slowly giving way to digital systems offering more features and better call security. See cellular phone, DAMPS, NAMPS. AMR See anisotropic magneto resistance.

AMS 1. Account Management System. 2. See American Mathematical Society. 3. American Meteorological Society. 4. Attendant Management System. 5. automated management system. AMSAT The Radio Amateur Satellite Corporation. A global organization of amateur radio operators who share an active interest in building, launching, and communicating amateur radio technology through noncommercial satellites. AMSAT was founded in 1969 as a result of the 1961 Project OSCAR satellite launchings. AMSAT was established as a not-forprofit educational organization to foster amateur participation in space research and communication. See the AMSAT-OSCAR Satellite Projects chart for some of the satellite projects following the initial OSCAR series. Many early launchings have piggybacked as secondary payloads on weather satellites. More recently, AMSAT satellites have shared launch vehicles with other commercial and scientific craft. In the mid-1990s, AMSAT became associated with ARISS amateur radio experiments aboard the International Space Station. Soon after, it became involved in the international Phase 3D satellite project, also called AMSAT-OSCAR 40 (AO-40). This project supports cameras, sensors, and transmitters and receivers in several radio frequency bands, including S, K, U, V, L, and X bands. It is the fourth of AMSAT’s high-altitude, global communications satellites, designed to replace earlier satellites that failed on launch or were no longer functional due to limited lifespans or technical failures. As of April 2001, efforts were underway to recover AO-40. In general, the satellite was in good condition, with some individual glitches that didn’t impinge on overall health. However, since orbit 201, when it predictably lost its solar lock, it was officially in a state of “hibernation” (unable to sense the Sun) with the magnetorque system off until solar lock could be reinstituted. AMSAT now consists of a number of loosely affiliated organizations around the world, some bearing the AMSAT name with extensions, working together through cooperative rather than formal arrangements. AMSAT sponsors discussion lists and publishes a weekly online report on satellites, covering almost three dozen individual orbiting bodies, including space stations. Many AMSAT enthusiasts are highly skilled technicians, and their knowledge and expertise have contributed to developing new technologies, in cooperation with a number of agencies, including the European Space Agency (ESA). See Amateur Radio International Space Station. See OSCAR for a chart of the earlier satellite projects. http://www.amsat.org/ AMSC See American Mobile Satellite Corporation. AMSC-1 A commercial satellite, operating in the Lband frequencies, owned by American Mobile Satellite Corporation. AMSC-1 provides voice, data, facsimile, paging, and other mobile communications services, particularly to commercial transport companies. Communication is through satellite phones or cellular/satellite hybrid phones.

AMSS 1. See Aeronautical Mobile Satellite Service. 2. Airborne Multi-Spectral Scanner. An aircraftmounted scanning spectrometer for acquiring highresolution imagery. 3. See Asian Mobile Satellite System. AMTOR amateur teleprinting over radio. AMTS See Automated Maritime/Marine Telecommunications System. AN access network. analog 1. Relating to, similar to, linear, continuous with. 2. Circuits or devices in which the output or transmission varies as a continuous function of the input. Here are two examples commonly used to illustrate the distinction between analog and digital display and selection systems: Time Piece Displays. Most analog watches have continuously sweeping minute and hour hands that move through a 360 degree arc through the action of internal rotating gears. Contrast this to a digital watch which stays on a one-minute setting until the next has been reached, and then ‘flips over’ the display to the next minute in discrete units. Dials and Buttons. In older AM radios, the turning of an analog radio dial will move the station pointer in a continuous path through the

various frequencies, and the transitions can be heard as the signals from various stations get stronger and weaker. In newer car radios, a push-button digital system is often used (sometimes in conjunction with an analog dial) to store the locations of preferred radio stations. Pushing the buttons ‘jumps’ to the desired stations without passing through the intervening frequencies. Traditionally, phone conversations were processed as analog transmissions over copper wires. Gradually, digital switches were introduced, but the link to the customers’ premises remained analog. With newer digital systems being produced, especially for mobile communications, and phone over Internet. When computers were first remotely accessed over analog phone lines through modems, it was necessary to convert the digital signals from the computer to analog signals through modulation. With the growing availability of ISDN, end-to-end digital transmissions are possible. See digital, ISDN, modem. anamux analog multiplexer. ANC All Number Calling. anchor 1. Something that serves to steady or hold, such as a guy wire or stake. 2. In hypertext programming, an element enabling links to related information. The

AMSAT-OSCAR Satellite Projects - Selected Overview Satellite

Launch

Notes

Phase II Satellites - developmental, low-orbit, operational, longer lifespan. See OSCAR. Phase III Satellites - operational, high elliptical orbit, longer lifespan. Phase IV Satellites - operational, high geostationary or drifting geostationary orbit, long lifespan. AMSAT-OSCAR 1

12 Dec. 1961

Phase-4A. 10 lb., beacon, 22-day orbit. Initiated by a U.S. west coast group. Nonrechargeable batteries. Elliptical orbit at 421 kilometers. Quarter-wave monopole antenna. Morse code telemetry. U.S. Air Force launched.

AMSAT-OSCAR 4

21 Dec. 1965

TRW Radio Club construction. Elliptical orbit at 34,000 kilometers (intended for circular orbit). No telemetry. Sleeve dipole and monopole antennas.

AMSAT-OSCAR 8

5 Mar. 1978

Phase-2D. Circular LEO at 910 kilometers. Several antennas. Battery failed June 1983.

AMSAT-OSCAR 10

16 Jun. 1983

NASA/NORAD #14129. Phase-3B. Similar to OSCAR I, with some improvements. Coatings provided better temperature control. On-board propulsion. High-altitude, elliptical, synchronous-transfer Molniya orbit at 35,449 kilometers.

AMSAT-OSCAR 13

15 Jun. 1988

NASA/NORAD #19216. Phase-3C. Linear analog transponder. Magnetorquer stabilization. Elliptical orbit at 38,000 kilometers, Molniya. Carried RUDAK-1, which failed.

AMSAT-OSCAR 16

22 Jan. 1990

NASA/NORAD #20439. PACSAT. Sun-synchronous near-polar LEO at 800 kilometers. Store-and-forward file server and AX.25 protocol. Digital repeater.

A

anchor delimits the two ends of the hyperlink, designated with a tag as follows: link text

anchor frame 1. In HTML coding, a frame (a defined section of the display) that contains at least one anchor tag (e.g., ) pointing to addresses, data, or images to be associated with that frame. The TARGET tag can be used to specify that an anchor applies to a specific frame if there is more than one frame associated with a page. 2. In advanced television (ATV) technologies, a video frame used for prediction, most commonly an I-frame or P-frame. B-frames are not used as anchor frames. See ATSC Digital Television Standard. Anchorage Accord An ATM Forum document comprising Foundation Specifications needed to assemble an ATM network infrastructure. This important suite established criteria for maintaining interoperability of ATM products and services. There were five dozen specifications listed in the Anchorage Accord, including intercarrier specifications, LAN emulations, interface requirements, physical layer specifications, traffic management specifications, and testing suites. The approval of the Accord was announced by the ATM Forum Technical Committee in April 1996. The step was an important one in forging working relations among theorists, specifications developers, and commercial implementers and was instrumental in furthering the acceptance and adoption of ATM as a networking technology. The Committee assured developers that specifications would be downwardly revised if interoperability problems were found in actual implementation. In August 1997, six additional specifications were announced, mainly to facilitate Internet connections and the transmission of converging multimedia data over ATM (e.g., voice or video over ATM). The Accord documents can be downloaded free of charge from the ATM Forum specifications archive on the Web. See asynchronous transfer mode. http://www.atmforum.com/ ancillary charges Charges for optional or valueadded services. AND See Automatic Network Dialing. Anderson bridge A device, usually employing a galvanometer, that measures reactance in order to determine capacitance or inductance by balancing against a frequency standard. Andreessen, Mark Andreessen developed the first version of Mosaic, the precursor to the Netscape Navigator browser, in early 1993 while at the National Center for Supercomputing Applications. He was working with the Software Development Group developing for Unix. In 1994, he joined forces with Mark Bina, some of his colleagues at the University of Illinois, and developers from Silicon Graphics to form Mosaic Communications. They essentially rewrote the code, as the new Mosaic company didn’t have the rights to market the version developed at the University. The company also had to change its name, so as not to infringe on the University rights

to “Mosaic” as a tradename. The new company was called Netscape Communications and is now wellknown for creating the Web browser known as Netscape Navigator. Andrew File System AFS. A distributed file system named for Andrew Carnegie and Andrew Mellon. AFS grew out of a collaboration between CarnegieMellon University and International Business Machines (IBM). anechoic 1. Not echoing or reflecting sound. 2. An environment without noise, or without significant noise. Sound recording rooms are designed to echo as little as possible, with thick, porous materials resembling foam egg crates absorbing the sound so it is prevented from reflecting back to the recording equipment. Speakerphones work better in anechoic environments. See acoustics. angle brackets < > Symbols very commonly used in programming code as delimiters or arithmetic operators. These are best known as greater than (>) and less than ( P+++>> L++ E W+++$ N++ o-- K? w? O M+ V !PS !PE Y++ PGP t+@ 5++ X++ R tv b+++$ DI+ D-- G++ e+++> !h !r !z -----END GEEK CODE BLOCK----Geissler tube A type of sealed dual-electrode gasfilled tube that glows when current passes through it. The color of the glow varies with the types of gases used, and the wave characteristics can be influenced by the amount and type of current applied. Historic versions of the Geissler tube, named after the inventor J. Heinrich Geissler, resembled glass lanterns or candles mounted on a metal or wood base with a straight or spiral illumination up through the center of a second, protective glass bulb (sometimes filled with a colored liquid to enhance the effect of the primary illumination in the inner tube). Some of the

smallest, earliest tubes lacked a stand and protective bulb but came in a variety of creative and charming shapes resembling short strings of hollow glass beads. Early Geissler-style tubes were used for signs and lamps, more recent variations are used as scientific research and calibration instruments. Over the decades, Geissler tubes have played a role in many pioneer aspects of electronics and telecommunications leading to the development of the light bulb, flash bulbs, a number of projection technologies, and the discovery of cathode rays. In contemporary calibration tubes, the central region of the tube is usually narrower than the ends. The very narrow region in the center induces strong spectral lines for sample comparisons. The Geissler tube is useful for calibrating optical instruments and as a reference tool. It has also been used in conjunction with imaging technologies as a low-cost experimental rotating mirror photodetection device. Educational versions of the Geissler tube often have more than one tube, each with different contents. These are useful for teaching about gases, induction, fluorescence, and other related concepts. For example, an energized Geissler-style tube can be used to illustrate magnetic field influences on charged particles. Geissler tube effects may be observed by the unaided eye or with scientific instruments such as spectroscopes. See cathode-ray tube, Crookes tube. Geissler, Johann Heinrich Wilhelm (1814-1879) A German physicist and glassblower who established a workshop in Bonn, where he crafted scientific apparatus. One of his more significant inventions was a type of mercury air pump that is still in use today for evacuating the air from bulbs and various laboratory apparatus. In collaboration with Julius Plückers, Geissler did experiments to measure the density of water. He also created instruments for the measurement of vapor. Modern refinements of the Geissler tube, that he developed in the late 1850s, are still used for scientific calibration. See Geissler tube. GEM See Graphics Environment Manager. GEMS See Global Environmental Monitoring System. gender A designation widely used to cable connectors to indicate whether they are female “innies,” or male “outies,” that is, whether they have holes or extended pins. If it is a simple round or squarish connector like a switchboard or composite video connector, the female end is usually called a plug while the male end is usually called a jack. Most common switchboxes for computer data connections have female connectors. Male and female connectors are both found on the backs of computers, and vary from platform to platform and sometimes even from brand to brand. This variation is inconvenient for users, who often have to pay extra money for gender changers, but cable and connector manufacturers don’t seem to mind the extra business.

gender bender/changer/converter A small connecter designed to change the gender of a plug or receptacle in order to enable connection to another plug or receptacle. The male end is the one in which the contact points protrude from the connecter. The female end is the one in which the contacts are depressed. Thus, a simple gender bender has two female ends or two male ends. Switchboxes and adaptors sometimes also perform gender bending functions. Adapters/extenders (male on one side, female on the other) are sometimes erroneously called gender benders, because they superficially resemble them, but have different genders. Gender benders are usually passive devices that do not influence the signal passing through the device. See adapter, extender, switch box.

Gender benders are commonly used to make connections between cables with the same male or female contacts facing one another. Some common gender benders used with serial cables include (A) DB-25 regular; (B) DB-25 slimline; (C) DB-9 regular. The slimline models are convenient for portable devices, such as laptops, for connecting to modems or printers.

General Instrument Corporation GIC. A broadcast technology corporation which is significant because it was the first to suggest an all-digital broadcast system to the Advisory Committee on Advanced Television Service (ACATS) for consideration for recommendations to the Federal Communications Commission (FCC) and the U.S. Congress. Subsequent to the GIC proposal, the focus on digital systems greatly increased, and ACATS and other advisory bodies brought the thinking about television technologies into closer alignment with recent digital advancements. In a separate, but related matter, General Instrument Corporation sought, through the U.S. courts, to hold the FCC to the mandate to ensure “Competitive Availability of Navigation Devices” (e.g., cable settop boxes) to maintain the right of competitors other than cable companies to produce and distribute these virtual navigation devices. However, as of June 2000, the court decision was to reject GIC’s challenge to an FCC separation requirement for hybrid navigation devices. See Advisory Committee on Advanced Television Service. General Magic A California-based commercial venture established in 1989 that focuses on providing innovative, cost-effective computer-Internet-telephony products for mobile applications. Products

G

include Portico, a development name for integrated voice/data communications and information services, and DataRover integrated voice/data hardware devices General Packet Radio Service GPRS. A wireless high-speed data communications standard operating over Global System for Mobile Communications (GSM) networks. GPRS is a packet-based air interface using existing circuit-switched GSM networks. GPRS offers enhancements to basic GSM. It provides functional connections with the Internet that were not possible with earlier systems. It can operate at speeds ranging from 9.6 Kbps to 115 Kbps (with plans for rates up to 384 Kbps) and offers live connections to mobile users such that users can be online continuously, without paying minute-byminute fees other than when uploading or downloading information. The higher data rates possible with GPRS not only reduce connect time costs but enable broader-band services, such as videoconferencing, to be implemented on mobile devices. Full implementation of these higher data rates are somewhat dependent upon the evolution of the underlying GSM technologies but will likely be realized over the next two years or so. Many see GPRS as a bridge between GSM and 3G mobile services. General Protection Fault GPF. A common fault condition encountered by users of Microsoft Windows software when applications memory conflicts occur. At the very least, applications should be closed up. Unfortunately, it may also be necessary to reboot the system. General Radiotelephone Operator License GROL. A lifetime operator’s license granted by the Federal Communications Commission (FCC) upon successful completion of competency requirements. The license is required for individuals who adjust, maintain, or service FCC-licensed marine, aviation, and international radiotelephone transmitters. It conveys the operating authority of the Marine Radiotelephone Operator License and requires the Written Element 1 and Written Element 3 exams to be passed. Some related FCC radiotelephone authorizations include the First, Second, and Third Class Radiotelegraph Operator Certificates. These require exams, in some cases Morse Code competency, and are valid for five-year terms (renewable). A GROL-licensee may also be granted a Ship Radar Endorsement on qualifying and passing the Written Element 8 examination. This permits the repair, maintenance and internal adjustment of ship radar equipment. There are also licenses specific to the Global Maritime Distress and Safety System. See GMDSS Radio Operator License. General Switch Management Protocol GSMP. An IETF standards-track packet network administration protocol to control a frame- or cell-based label switch. GSMP is an asymmetric protocol supporting master (controller) and slave (switch) interactions. GSMP provides a means to query and report connection, port, switch, and Quality of Service (QoS) information and statistics for MPLS label switch devices from or to a third party controller.

Thus, GSMP can be used to query switches, to establish and release connections, to modify a multicast connection, and to manage switch ports. It can also notify the controller of asynchronous events. Multiple instantiations of a single controller can be used to control multiple switches and partitioning is supported for the control of a single switch by multiple controllers. The capability to query and report switch-related configuration and statistical status is particularly valuable for remote switch operations and, as the protocol evolves, is desired for optical network configurations as well. Initially, GSMP was developed to work with static switch partitions; however, dynamic forwarding to multiple administrative domains might be feasible for future versions of GSMP. GSMP does not make significant assumptions about the underlying hardware over which it is transmitted and thus can be implemented in a variety of types of networks. As a separate standards-track document, packet encapsulations for GSMP transport have been defined for ATM, Ethernet, and TCP networks: • In ATM networking, GSMP packets are variable length and encapsulated directly in ATM AAL-5 with an LLC/SNAP header. • For Ethernet, GSMP packets are transmitted after the Ethertype 0x880C identifier up to a maximum length of 1492 bytes. • In TCP/IP, GSMP is transmitted after a prepended TLV header field of type Ox88-0C and an integer indicating the length of the following GSMP message. The message is processed after its successful receipt. TCP/IP encapsulation can also be transmitted with authentication. With the evolution of GSMP towards an industry standard in the late 1990s, there has been interest from the commercial and developer communities in defining GSMP for other environments, including experimental switches and patented, proprietary switches. Thus, GSMP for FSR switches (VTT Information Technology) and ForeRunner (Sprint) switches are of interest to developers. See flow, Ipsilon Flow Management Protocol, RFC 1987, RFC 2026. Generalized Trunk Protocol GTP. A telephony protocol enabling complex Channel Associated Signaling (CAS) and Common Channel Signaling (CCS) protocols to be executed in peripheral devices in order to remove some of the processing load from the main processor. generations, computer In evolutionary terms, computing systems and computer software have been roughly grouped into a generational hierarchy, with each step in the hierarchy represented by a numeric designation. Many of these generations are overlapping, and the later ones tend to become less distinct and more concurrent than the earlier ones. The following categorization gives a very general overview of previous computer generations, with some propositions on definitions for future trends and possibilities.

Computer Generations – Hardware 1st – Large, vacuum. The early large-scale computer systems were powered and controlled by vacuum tube technology in the 1950s. They needed elaborate hand wiring, significant cooling and maintenance, and provided limited computational capabilities and memory. 2nd – Large, transistor. The invention of the transistor greatly changed computing. Now much more could be done in much less space and new possibilities opened up in the early 1960s. Memory increased, virtual memory schemes were implemented, programming languages improved, and the idea of reusable code began to spread, championed largely by Grace Hopper. Timesharing systems were developed. 3rd – Large-scale ICs. Integrated circuits provided the next significant step in computing hardware, from the mid-1960s to the mid-1970s. Again, computers became smaller and more powerful, memory increased, languages developed, and computing was entering the mainstream. Intercompatibility and networking began to develop, as did higher level languages that could be learned and used by lay programmers. 4th – Microprocessors. Computers suddenly became accessible to homes and businesses in the mid1970s, when single processor boards could be built, and a variety of general and special purpose languages could be developed by a larger community of programmers for a growing community of users. Very soon, the single-board computers outstripped the capabilities of their roomsized predecessors and computing began to become a mainstream technology. 5th – Parallel processing. With the development of less expensive, smaller computers, it also became economical to use multiple processors, and to develop languages and algorithms to take advantage of parallel systems and distributed, networked environments. Networking grew to the point where the global network, the Internet, was reaching into every corner of the world. Most of this evolution occurred from the late 1980s to 1990s. 6th – Parallel entities. In the author’s opinion, there are two important aspects to sixth generation computers. One is the type of knowledge processing that will be needed to handle the burgeoning information on global networks. Another is the development of high-speed transport systems that are beginning to match and exceed the processing speed of computer central processing units (CPUs). When the communications links between computers match the processing speed of the computers themselves, a fundamental, significant change occurs, in that the system begins to function as a single entity rather than as separate, intercommunicating systems. Where this will lead is yet to be seen. This technology began trickling out in the early 1990s and will probably continue

to build momentum through the turn of the century. 7th – Abio/Bio systems. The author has speculated on what may constitute seventh generation systems and believes that integrated human-computer (or at least bio-electronic) systems may be the next qualitatively different level of computer development that will occur after, or more probably concurrently with, fifth and sixth generation systems. Applied engineering of neural network systems began in the early 1960s, yet when the author proposed the feasibility of human/bionic hybrids in late 1970s, the feedback was disbelief and horror. Even by the mid-1980s, there was strong opposition to the idea, and many said it could never happen. Since then, the use of bionic hearts and limbs and other nonbiological systems has grown and brain implants to provide auditory and visual stimulation have been successful. The author believes that younger generations will accept these electronic/mechanical enhancements as a matter of course. At a conference in the mid-1990s, the author heard about a patented human-electronic interface invented by Howard Davidson, a scientist known for his work with subminiature components. Davidson has engineered a design for “jacking in” to the brain through a tiny, aesthetic electronic device worn like an earring. 8th – Metacomputers. Are there potential computer generations beyond those described above as seventh generation? George Dyson and other authors who have speculated about meta-intelligences, those that arise from the aggregate processing and communications of smaller units which function as a whole on a higher level than it may be possible for us to apprehend or comprehend, have pointed to the future possibilities for eighth generation computing systems, or digital intelligences. Someday the entire world will be networked with high-speed devices and human intelligences might be directly interfaced with these machines. Then, just as individual cells in our body are not aware of the specific thoughts and functioning of our brains, as individual humans we may not be aware of the specific thoughts and functioning of the telecommunications and computer network as a broader entity. This far-flung idea of a vaster digital intelligence or a vaster digital/biological intelligence makes some people uncomfortable, but that doesn’t mean it can’t happen, or that it isn’t already happening.

generations, computer languages Programming languages have evolved to support different systems, different capabilities, and different styles of thinking and programming. There is no cut-and-dry way to describe the evolution of languages, since many were designed to suit specific needs and are not directly comparable. Nevertheless, it can still be valuable to look at some of the trends and general categories in the industry that describe generations of computer languages.

G

Generations – Computer Languages 1st – Machine code. Low level microcode and machine languages which interacted on the hardware and systems levels. Knowledge of computer architecture was necessary to program machine or microcode. First generation languages were difficult to debug, lengthy, and to most programmers, tedious. Most programming up until the 1960s was done in this way. 2nd – Symbolic low level. In the 1960s and 1970s, there began a transition to symbolic languages (which originated in the 1950s), which used mnemonic symbols, labels, and shortcuts to represent machine code, and which could be more easily written and debugged. Like machine code, however, assembly language program listings were still very long and knowledge of the low level architecture of the processor was still necessary. 3rd – Symbolic high level. Assembly language was difficult for many programmers to learn, as knowledge of the hardware was required and assembly was generally not portable to other systems. New, more portable languages, which could be individually interpreted or compiled on the machine on which the software was going to run began to emerge. Some early ones included ALGOL, FORTRAN, and COBOL. These high level languages used syntax that more nearly approximated the English language, and the software could more easily be ported to other systems. Debuggers were developed to further ease the burden of finding errors and removing them. 4th – Symbolic high level. The development of BASIC and various educational scripting and authoring languages made it possible for even new programmers to exercise a moderate amount of control over the execution of computer programs, and these languages were popularly implemented on microcomputers starting in the mid-1970s and 1980s. Many of these languages are interpreted, so the programmer doesn’t have to acquire the technical expertise to compile and link executables. 5th – Symbolic AI. These languages are similar to symbolic high level languages in many aspects of syntax and execution, but they differ in terms of the way they process data and in the kinds of data that they are optimized to handle. Fifth generation languages came predominantly out of research laboratories doing artificial intelligence, neural network, and fuzzy logic work, often with languages like LISP and PROLOG. These languages are good at modeling virtual worlds, making inferences, and modifying themselves while running. They are good at parsing and interconnecting data and concepts in a way that is difficult with 3rd and 4th generation languages.

generator In its basic sense, a machine that is designed to convert mechanical energy into electrical energy, or one that converts direct current (DC) into alternating current (AC). Dynamo. Generic Access Profile GAP. A profile is defined by the Open Systems Interconnection (OSI) model as a combination of one or more base standards and association classes, necessary for performing a particular function. The GAP specifies well-defined compatibility levels for DECT products, as an extension of an ETSI-published Public Access Profile (PAP) incorporated into Digital European Cordless Telecommunications. (DECT). See Digital European Cordless Telecommunications. Generic Addressing and Transport Protocol GAT. A digital telephony protocol for exchanging Application Protocol data units (APDUs) between service provision points. It may be used between a terminal and a network or within or among networks. The recommendations for GAT use with ISDN/B-ISDN is described in ITU-T Q.860. generic cell rate algorithm GCRA. In ATM networking, an algorithm used to enforce a particular performance level with regard to cell traffic. The GCRA evaluates the cell to determine whether it conforms to the established cell traffic contract. In a network switch, the UPC function will typically incorporate an algorithm such as GCRA to enforce conformance with the specified parameters. See leaky bucket for a fuller explanation and example. See cell rate for related concepts. generic flow control GFC. In ATM networks, a means of controlling traffic flow. A field in the ATM header can be used to designate flow control parameters. This field is evaluated en route, as appropriate, and is not included in the final delivered communication. See cell rate. generic flow control field GFC. In ATM networking, traffic flow control is an essential aspect of moving cells from one place to another. In the ATM header, there are priority bits which can be set to inform the end-station that congestion control may be implemented by the switcher. See cell rate. Generic Security Service Application GSSA. An IETF elective proposed general Internet standard. See RFC 2078. GENIAC Genius Almost-Automatic Computer (in the tradition of the UNIVAC, ENIAC naming convention). The GENIAC was a personal computing device designed by Edmund C. Berkeley and possibly also Oliver Garfield in the mid-1950s. Berkeley was an insightful author, robotics entrepreneur, and the designer of what was likely the first desktop computer ever invented, the Simon. Garfield was an author, engineer, and business person in much the same vein as Berkeley. Unfortunately, the partnership ended up in disputes and Garfield ended up with the name Geniac while Berkeley continued marketing computing devices under the name Brainiac. The GENIAC kit was originally sold through Berkeley Enterprises, Inc. Documentation was furnished through Oliver Garfield’s GENIACS: Simple

Electric Brain Machines, and How to Make Them bound with the Manual for Geniac Electric Brain Construction kit No. 1. Once assembled, the GENIAC could play simple games and do basic computations. The kit sold for varying prices from about $15.95 to $19.95 (about two days’ wages). Logical functions were carried out electromechanically, through rotary switches operating in a cascaded sequence that could be configured for different computing experiments. For information on the GENIAC Calculator, see Garfield, Oliver. See Berkeley, Edmund C.; Brainiac; Simon. genlock A device that takes a composite video signal and creates synchronizing pulses so the signal can be combined with signals from other devices such as computers, video cameras, etc. For example, a live feed from a TV set or a signal from a VCR can be fed into a genlock interfaced with a computer. The video image usually is displayed under the computer image and appears on the monitor as a combined image. Genlocks are often used to add computer subtitles to video, which are then transmitted as a composite signal to a broadcast medium or saved on a recording medium (usually tape). The first widespread distribution of microcomputer genlocks was in 1986 for the Amiga computer, and many local cable companies continue to use them for community events broadcasts. geographic information system GIS. Any system in which terrain information is gathered, processed, and stored, usually for later retrieval for analysis, long-term comparisons, mapping, navigation, etc. An enormous amount of geographic information is gathered by orbiting satellites, geocoded, and stored on high storage-capacity computer systems. Land-based tracking of networks, utilities, and transportations systems is also carried out with GIS systems. See geoInterface, Landsat. geographic interface This term has two meanings: (1) interfaces designed for users to access and manipulate geographic data, and (2) an evolutionary step in computer user interfaces which models the world in a simulated 3D environment as visual objects or functional constructs. The second meaning represents a relatively new approach to computer user interfaces. The idea has been around for a while, but the resources to implement it have been cost prohibitive until recently. In the early 1970s, microcomputer user interfaces consisted of dipswitches for input and small blinking lights for output (see Kenbak-1 and Altair). They were replaced by simple monochrome, text-based interfaces by 1975 (see SPHERE System). In the early 1980s, developers began producing graphical user interfaces (based largely on 1970s research at Xerox PARC), and it was not long after that the first experimental geographic interfaces began to appear. Just as a graphical user interface might show a file cabinet icon to indicate a file area, a geographic interface might show an illustration of a room with an illustration of a real-looking file cabinet with drawers that open and close when they are clicked or

otherwise activated, and files that slide in and out and display their contents. It’s a type of virtual environment that can exist in a simulated 3D space with gloves and goggles, or on a 3D-2D simulated space on a flat monitor. It’s computing and graphics intensive and takes a long time to develop, but it has a lush, tactile appeal that many people like, and it will probably continue to gain popularity. With global object modeling standards, there may eventually be a large library to draw upon for this type of interface so individual developers can build on existing objects rather than continually reinventing the wheel. See geoInterface, graphical user interface, objectoriented, Open Systems Interconnection. geographic north The region on the Earth called the North Pole from which imaginary lines of longitude emanate to meet again on the other side at geographic south. It is the general direction in which the northseeking needle on a compass points, as magnetic north is near geographic north. See magnetic north. geoInterface, IBM Geographic Interface International Business Machine’s geographic information systems (GIS) interface. GeoInterface was designed to allow users to visualize, analyze, and manipulate IBM Geographic Facilities Information System (GFIS) data on OS/2 and Microsoft Windows systems. It works with IBM’s VisualAge object-oriented programming environment in client/server and detached mode systems. Practical uses of this system include tracking and analysis of demographic information, transportations system planning and administration, telephone, cable TV (CATV), and computer networks, utility distribution systems, etc. Georgia Rural Telephone Museum Located in a former 18,000-ft cotton warehouse, built in 1911, the Georgia Rural Telephone Museum opened officially in 1995 in Leslie, Georgia. The building was established across the street from the Citizen’s Telephone Company. It includes about 2,000 historic telephones and other examples of communications equipment. http://www.sowega.net/~museum/ Geostationary Meteorological Satellite GMS. A geostationary satellite system of the Japan Meteorological Association (JMA) and the National Space Development Agency (NASDA) that is affiliated with World Weather Watch (WWW). The GMS system senses the region over Asia and the western Pacific at 140 degrees E longitude. It is similar to the U.S. GOES system. The first GMS was launched from the U.S. in 1977, and new satellites have beem put into orbit every four or five years since from the Tanegashima Space Center in Japan. GMS-5, which has been operational since the mid1990s, provides data on cloud patterns (including volcanic activity), water vapor distribution, and sea surface patterns to more than two dozen countries. The Japan Weather Association provides hourly GMS images online. GMS systems also serve as communications relays for forwarding information obtained from ships, aircraft, and communications buoys and provide assistance in emergency search and rescue operations. By the late 1990s, the GMS

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system was being designed to take on a broader role, serving not only as a meteorological sensing system and relay station, but also as an air traffic control support system. In February 2000, the GMS-4 system, launched in 1989, was taken out of service and moved out of the way into a higher region for its final orbit. The GMS5 system, launched in 1995, is still operational and apparently in good working order, but a transition is being made to a new system of satellites, the Multifunctional Transport Satellite (MTSAT) series, beginning with MTSAT-1R and MTSAT-2. Despite its age, GMS-5 is expected to be able to operate until the MTSAT platforms come online around 2003. See Multifunctional Transport Satellite, National Space Development Agency. Geostationary Operational Meteorological Satellite GOMS. Also known as Elektro, the GOMS system is a three-axis-stabilized imaging satellite that is part of the Russian Federation Planeta-C Meteorological Space System. The first of the series of satellites was launched in October 1994, with each platform expected to last at least three years. GOMS orbits over the Earth’s equator at longitude 76°50´ E. GOMS senses infrared images of the Earth’s surface and cloud cover, provides continuous coverage of atmospheric patterns, detects potentially hazardous phenomena, measures sea surface temperatures, and monitors space-borne energy particles. Aboard the satellite, a radiometric line scanner images the Earth, digitally encodes the information, and transmits it to a ground station for preprocessing and eventual dissemination as satellite products. The communications portion of GOMS includes satelliteto-ground transmissions, ground-station intercommunication relays, and transmission to users on an operational basis.

In a geostationary orbit, the movement of the satellite keeps pace with the movement of the Earth and is thus within the same general visual and communications region at all times, as seen from the Earth.

geostationary orbit A type of orbit that is timed with the movement of the body it is orbiting so the period is equal to the average rotational period of the orbited body. If, in addition, the orbit is circular, the satellite will appear to be not moving when viewed from the ground, hence the name. In simpler terms, if you place a satellite in a circular

orbit about 35,900 to 42,164 kilometers above the Earth, it will appear to remain in the same place because of its synchronized relationship to the Earth’s orbit. This type of orbit has some advantages for communications. The satellite can always be counted on to be available at the same location, and at that high altitude not many satellites are needed to provide global coverage. The main disadvantage is that powerful sending and receiving stations are needed to send and receive signals to/from such a high orbit. Geostationary orbits were described by Arthur C. Clarke in the 1940s and 1950s in considerable detail and with remarkable foresight. Also called geosynchronous orbit and fixed satellite orbit. geosynchronous orbit See geostationary orbit. GEOTAIL A Japanese research satellite launched in 1992 to study the structure and dynamics of the tail region of the Earth’s magnetosphere. The orbit of the satellite was planned so it would cover the magnetotail over a wide range of distances. It contains instruments to measure the magnetic field, the electric field, plasma, energetic particles, and plasma waves. http://www.gtl.isas.ac.jp/ German Space Operations Center GSOC. A complex located near Munich, Germany, that was originally established to support the first German research satellite (AZUR), launched in 1969. GSOC is a facility of the German Space Missions Directorate (DLR) that prepares and executes national and international cooperative space flight projects through the main facility and a number of remote satellite ground stations. GSOC responsibilities include not only mission preparation, acquisition, rocket operations, and payload administration, but also the development of software support systems for mission support, data handling, and ground operations. One of the interesting experiments undertaken by GSOC and its associates is the GPS Small Satellite Mission Equator-S (launched in 1997). Before this mission, Global Positioning System (GPS) receivers could be used only in near-Earth regions, well below the orbiting height of the GPS satellites themselves. This experiment successfully demonstrated that GPS receivers could be used at altitudes up to 34,000 kilometers. http://www.gsoc.dlr.de/gsoc.htm GETS See Government Emergency Telecommunications Service. GFP See global function plane. GFC See generic flow control. GGP See Gateway to Gateway Protocol. ghost 1. A shadow image on a monitor with phosphor burn-in. When a phosphor-coated display device continually displays the same image (especially if it is a bright one) an undesirable pale image that does not disappear when the screen is refreshed may be burned into the display surface, thus interfering with the display of desired images. This ghost image indicates permanent damage to the monitor (unless the coating is replaced). See screen saver. 2. In audio communications, a quieter repeat or echo of a conversation. ghost, broadcast In broadcast images on a television screen, a slightly offset, pale copy of the desired

image caused by secondary transmission of the original signal. Terrain can cause reflections of the direct signal that arrive at the receiver just slightly delayed and make the image appear slightly blurred or double. ghost port In the early days of computing, software was in its development stages and was not always written to handle processes in a secure manner. Thus, when users left a system or terminated a remote connection in an unexpected way, the process itself did not necessarily terminate, allowing the next user into the currently open account or process. It would sometimes allow timeshare users, for example, to log in to the previous user’s account through the ghost port (the unterminated session) and access the files. Ghost ports are less common now, with standard operating systems and more security-savvy programmers developing the software, but hackers are still sometimes aware of security holes and programs and methods that create ghost port access to less robust systems. The phrase can also refer to an access port to a computer system that is visible to technical users but invisible to nontechnical users, in other words, one accessible through system commands or procedures that are inherent to the system (as opposed to being hacked into the system) but not generally known outside of techie circles. Thus, ghost port refers to a port that is left behind and is mistakenly assumed to be a new port or one that is visible or apparent only to a subset of computer users. ghosted icon A graphical user interface convention in which an icon is displayed in a toned down or paler version of itself to indicate that it is not currently active or available for selection by the user. If you click on a ghosted icon or ghosted image, nothing is likely to happen except that you feel foolish for having tried anyway. Ghostscript A PostScript graphics language that is part of the Free Software Foundation’s GNU project. Ghostscript is almost fully compatible with Adobe’s PostScript. Ghostscript is a great tool for viewing and printing PostScript files. Adobe PDF readers, freely available on the Internet, are now beginning to supersede the use of Ghostscript for viewing and printing PostScript files. GIAC See Global Incident Analysis Center. giant magnetoresistance GMR. A resistance effect discovered in the late 1980s by P. Gruenberg in Germany and A. Fert in France. Large resistance changes were observed in materials comprised of alternating, very thin layers of metallic elements when exposed to high magnetic fields at low temperatures. Other scientists were excited by this discovery and began to study many different types of materials and configurations of layers to better understand the effect and to see whether it could be produced without subjecting the materials to very low temperatures. IBM researchers such as S. Parkin took a particular interest in this area of research. It was determined that very thin combinations of nonmagnetic metals between layers of magnetic metals could induce the nonmagnetic layer to change its orientation.

Oscillations in the magnetic alignment were also detected and it was noted that resistance was low or high depending upon whether the layers were in parallel or antiparallel arrangement. GMR research has led to a new category of supersensitive hard disk drives and, since this is a general reproducible effect, no doubt many other practical applications will be developed. See Kerr magnetooptic effect. .gif The conventional graphics file name extension used for CompuServe’s Graphics Interchange Format (GIF) raster-format graphics files. See Graphics Interchange Format. giga- (abbrev. – G when combined) (pron. jig-a) A prefix for 109 or 1,000,000,000 in the SI system. One billion. In computing, a giga is 230 or 1,073,741,824 (a multiple of 1024). Giga- has long been used in supercomputing, mainframe, and scientific applications, but it was relatively unknown in lay language until the mid-1990s when gigabyte (Gbyte) hard drives dropped to consumer price ranges. It used to be a lot of storage space. Ten megabytes used to be a lot of storage. In fact, whole community BBS systems used to run on five megabyte drives in the early 1980s. Now two gigabyte drives are considered to be average. See atto-. gigabit GB. (pron. jig-a-bit) 1,073,741,824 (230) bits. Gigabit Ethernet GbE. Ethernet networking capabilities capable of supporting half and full duplex transmissions at speeds of 1 Gbps (one billion bits per second). Fast Ethernet, the predecessor to Gigabit Ethernet, is a widely installed international open standard. In 1997, the IEEE approved the P802.3ab study group’s proposed 1000Base-T standard for full duplex Gigabit Ethernet signaling over Category 5 networking systems. This approval led to the IEEE 802.3z Working Group ratifying a standard for Gigabit Ethernet, in June 1998, that included three physical layer specifications (one for shielded copper wire, two for optical fibers). Gigabit Ethernet was developed because vendors and users wanted the benefits of a scalable high speed network to support existing Ethernet frame and protocol characteristics to enhance rather than obsolete existing systems. Gigabit Ethernet uses the same frame format, media access control, and flow control characteristics as slower Ethernets. Gigabit Ethernet provides a practical way to set up a backbone for interconnecting Ethernet and Fast Ethernet networks, and provides an Ethernet upgrade path as the technology becomes cheaper. The types of applications that require enhanced Ethernet implementations include scientific modeling, multimedia communications, data warehouse search and retrieval, and others. The most significant competitor to the faster versions of Ethernet is asynchronous transfer mode (ATM). Gigabit Ethernet is implemented at the physical (PHY) and media access control (MAC) layers. It supports the same frame format and size, and carrier sense multiple access with collision detection (DSMA/CD) as Ethernet, and Fast Ethernet. Quality

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of service (QoS) is not inherent in Gigabit Ethernet, which is primarily a high speed connectivity mechanism, but is incorporated through other standards. RSVP is one way of providing quality through an open standard that can be incorporated into a Gigabit Ethernet system. Objectives for link distances include multimode fiber optic links up to 550 meters, single-mode fiber optic links up to 3 kilometers, and copper-based links up to 25 meters, and Category 5 unshielded twisted pair (UTP) links up to 100 meters. A Gigabit Media Independent Interface (GMII) is also being studied. Cabling specifications include 1000BASE-CX Wire-based transceivers or physical layer (PHY) devices for short-haul shielded copper cable connections up to 25 meters. 1000BASE-T

Wire-based transceivers of physical layer (PHY) devices for four-pair twisted-pair copper cable connections up to 100 meters.

1000BASE-SX Optical transceivers or physical layer (PHY) devices for cabling through optical fibers at 770 to 860 nanometer wavelengths. Based upon Fibre Channel signaling for multimode fiber. 1000BASE-LX Optical transceivers or physical layer (PHY) devices for cabling through optical fibers at 1270 to 1355 nanometers. Based upon Fibre Channel signaling for single-mode or multimode fiber. 1000BASE-LH Long-haul multivendor specification. See asynchronous transfer mode, Ethernet, Fast Ethernet, Gigabit Ethernet Alliance. Gigabit Ethernet Alliance GEA. A California-based multivendor open forum established in 1996 to promote the development and acceptance of Gigabit Ethernet technology and to actively support and accelerate the standards process. The GEA supports IEEE activities with regard to the development and ratification of Ethernet standards, particularly the High-Speed Study Group, the IEEE 802.3 Working Group, and the IEEE 802.3z Gigabit Ethernet task force. The group provides technical resources for implementation and product interoperability. In June 1998, it ratified a standard for Gigabit Ethernet. See Gigabit Ethernet. http://www.gigabit-ethernet.org/ Gigabit Interface Connector GBIC. An interface, commonly sold as a hub-compatible peripheral card, used in Gigabit Ethernet uplinks. A hub may have slots for more than one GBIC. The GBIC enables an optical cable to be connected to an appropriate port by converting electrical impulses into laser light signals for transmission over a medium such as Fibre Channel. It is sometimes also called a Gigabit Interface Converter. See Gigabit Ethernet.

gigabyte GByte, GB. (pron. jig-a-bite) 1,073,741,824 (109) bytes. Data rates are often described in gigabits per second (Gbps) or, for very fast rates, may be described as Gigabytes per seond (GBps). Gigabytes are also used to describe the storage capacities of a large number of tape and hard drive storage media. Gigabyte System Network GSN. See Hippi-6400. GIGAMO A gigabyte-class magneto-optical storage technology developed by Fujitsu Limited and Sony Corporation, announced in November 1998. It was the first widely available magnetic-induced super resolution (MSR) technology, providing 1.3 GBytes of storage on a 3.5-inch disc with a 5.92 MBytes per second transfer rate. GIGAMO retains the same cartridge size and disc diameter as ISO/IEC 15041 standards but has higher linear bit densities. The data storage capacity is about twice that of the widely adapted 640-MByte CD-ROM discs, and the technology is backwardly compatible, using the same write heads as earlier systems. See magnetic super resolution. GIGO garbage in, garbage out. An abbreviation to describe a situation in which output cannot be better than its corresponding input, with the implication that it is the fault and responsibility of the developer or data entry person if the system gives back bad or incomplete information. See garbage in/garbage out. GII See global information infrastructure. GIIC See Global Information Infrastructure Commission. gilbert A centimeter-gram-second (CGS) unit of magnetomotive force equal to 10 divided by 4p ampere-turn. It is named after William Gilbert. Gilbert, William (1544-1603) An English physicist and physician who investigated electrostatic charges in various substances. He observed that magnetized iron lost its attractive power when heated to red heat and published De magnete (On the magnet) in 1600. He emphasized the distinctions between the magnetic effect of substances, such as lodestone, and the attractive properties of amber, a distinction previously promoted by J. Cardan in 1550 but at the time still not widely considered. In his treatise, he used the word electrica to describe attractive phenomena. Gilbert established that the Earth is a large magnet, thus explaining the general behavior of compass needles. The gilbert unit of magnetomotive force is named after him. See gilbert, versorium. GILC See Global Internet Liberty Campaign. Gilder’s law Bandwidth capacity will roughly double in capacity every six or nine months or so. This law, in a sense, takes over from Moore’s law, with chip processing capacities doubling about every 18 months to two years. With the emphasis away from single user systems towards network technologies, the same general idea is being applied to the growth and evolution of network transmission technologies. The term is attributed to Greg Papadopoulos at Sun Microsystems in honor of George Gilder, a business technology commentator and strong proponent of optical network technologies. See lambda switching, Moore’s law.

Gill, Jonathan “Jock” (ca. 1946- ) In 1992, Gill served as a Clinton/Gore campaign consultant on electronic publishing and email access and became the Director of Special Projects in the Office of Media Affairs from 1993 to 1995, during the Clinton Presidential Administration. He is probably best known for developing email access to White House documents and, in 1994, being the first manager of the U.S. President’s Web site, allowing users to take a virtual tour of the White House and find information on contacting government agencies. Gill is the founder of Penfield Gill, Inc., a media communications and planning company. GILS See Government Information Locator Service. gimbal A mechanism or material that permits an attachment to be freely suspended or inclined in such a way that the suspended attachment remains level, or so the attachment can be inclined in any direction or several directions. Marine compasses and gyroscopes incorporate gimbal mechanisms. gimp Extremely flexible wire or cable. Wire that can be easily threaded, woven, or spiraled. Gimp is wound up and attached to telephone handsets to allow a length of wire to tighten up like a spring when not in use, so the talker doesn’t have to interrupt the phone conversation to reach the refrigerator. Gintl, Julius Wilhelm (1804-1883) An Austrian physicist and telegraph director who was one of the first to propose a practical means to transmit telegraphic communications in both directions at the same time. Up to this time, telegraphs were one way, thus tieing up the lines for returning messages until the current message was finished. Using two batteries and a compensation method, Gintl devised twoway communications in 1853. Two-way or duplex telegraphy was an important means of increasing line capacity that was later refined and extended by other inventors. See duplex telegraphy. Ginzton, Edward Leonard (1915-1998) A Ukrainian-born American inventor and professor who emigrated to San Francisco in 1929, Ginzton headed up the Microwave Laboratory at Stanford. He developed further applications with the Klystron technology developed by the Varian brothers, the cofounders with Ginzton of Varian Associates, in 1948. In the late 1950s, he headed up the Stanford linear accelerator project. In 1959, he became the CEO of Varian Associates, remaining as Chairman until 1984 and serving on the Board until 1992. Ginzton is remembered not only for his technical achievements with the Klystron tube and Stanford linear accelerator, but also for his pioneering management policies. Ginzton was instrumental in establishing employee incentives and benefits long before such practices were common or mandatory. His policies aided him in attracting top talent to the firm and provided a new model for employee relations in the emerging Silicon Valley community. He also chaired the National Academy of Sciences committee that advised on the Clean Air Act of 1971 and, with David Packard, supported the development of minority-owned businesses.

Ginzton has been recognized through numerous awards, including the IEEE 1969 Medal of Honor and induction into the 1995 Silicon Valley Engineering Council’s Hall of Fame. When the Microwave Laboratory at Stanford University broadened in focus, around 1970, it began to be called the E.L. Ginzton Laboratory. It is an independent lab for engineering and physics research. See Klystron, magnetron, Silicon Valley, Varian Associates. Giorgi System A system of measurement in which the units are meter, kilogram, second, and ampere (MKSA). GIP See Global Internet Project. GIS See geographic information system. Gisborne, Frederic Newton (1824-1892) An English-born Canadian inventor who devised new ways of insulating communications cables against harsh environments. With the financial backing of Americans, most notably Cyrus Field, Gisborne was a strong motivational and administrative force in linking Europe and North America, in 1858, with the first successful transatlantic telegraph cable and the first successful permanent cable a few years later. Leading up to this important historical achievement, Gisborne studied telegraphy in Quebec in the 1840s, excelling in his courses and subsequently accepting a head position with the Montreal Telegraph Company. He then was involved in the founding of the British North America Electric Telegraph Association (BNAETA) and, on its behalf, negotiated unsuccessfully with eastern Canadian governments to set up a Halifax-to-Quebec telegraph line. Thereafter, Gisborne took the position of superintendent of the Nova Scotian telegraph lines. He sought backing from the government for an underwater line from Halifax to Newfoundland, expressing an interest in solving the problems associated with undersea installation and maintenance. In 1851, the Nova Scotia Electric Telegraph Company was established to oversee existing lines and create new ones. In 1852, Gisborne left his position with the Nova Scotia Electric Telegraph Company to establish the Newfoundland Electric Telegraph Company. His association with financier Cyrus Field began in 1854 when Gisborne contacted Cyrus’ brother, Matthew D. Field, on behalf of the financially stressed Newfoundland telegraph project. The American collaborators purchased the assets of the Newfoundland Electric Telegraph Company and settled its debts, traveling the difficult wilderness journey to St. Johns, Newfoundland, in spring 1854, to present the charter for a proposed New York, Newfoundland, and London Telegraph Company. The first undertaking of the expanded venture was to link Newfoundland with neighboring regions and with the U.S. Thus, submarine cables were installed between Cape Breton, Newfoundland, and Prince Edward Island, and telegraph lines were installed across the perilous Gulf of St. Lawrence (though not on the first try). With the involvement of the U.S. collaborators, who envisioned oceanic telegraphy, Gisborne’s ambitions increased. He became determined to establish a cable between Canada and Ireland. Despite months of

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harrowing travel and political arrangements further aggravated by financial difficulties, Gisborne continued to pursue his goal of establishing a transatlantic cable. Gisborne’s contribution is sometimes overlooked, as he pulled out of the partnership near its successful completion, due to distrust and disagreements with his collaborators, but he was an important contributor, both to the inception and progress of the project. See Field, Cyrus West; Gooch, Daniel; gutta-percha; transatlantic cable. GITS Government Information Technology Services. GL See graphics library. Gladstone-Dale law The refractive index of a substance varies with a change in temperature or volume according to a formula in which the index of refraction (n) plus one, over the density (r), equals a constant (k). glass house colloq. A term to describe the large, glassed-in, controlled environments used to house and protect (and in some cases air-condition) large computer installations. These environments still exist, to some extent, in supercomputing systems, but technological advances have decreased the size and fragility of many computers, and glass houses are no longer needed for small or medium-sized computing systems. Glass houses or clean houses are still used in chip manufacturing environments to provide a carefully regulated environment where temperature, humidity, and even tiny particles can affect the structure and functioning of certain delicate or microminiature components. glass insulator A historic type of insulating safety device ranging in size from about 6 inches to about 18 inches that was very commonly used to support live wires on utility poles. See insulator, utility pole for a chart and more detailed information. GLIS See Global Land Information System. glitch 1. Unexpected, small, but annoying problem, usually causing a delay or minor informational error. This term is usually applied in instances where repetition of the problem is unlikely or infrequent. 2. Undesirable brief surge or interruption of electrical power. Global Area Coverage GAC. One of the sample data set archives of the National Oceanic and Atmospheric Administration (NOAA) derived from the Advanced Very High Resolution Radiometer (AVHRR) sensors onboard TIROS and NOAA-x satellites. As the satellites orbit, they collect Local Area Coverage data, which is stored, combined, and compressed into GAC, available for download. In order to compress the data from LAC to GAC levels, four pixels in a scanline are sampled and averaged and the fifth pixel is skipped, with the process repeating to the end of the scanline. The following two scanlines are then skipped, thus creating a pattern for each three scanlines on through the data file. GAC resolution is approximately 7.6 km. Various agencies distribute data products based on GAC downloads. For example, the SeaWiFS GAC Level 1 consists of radiance data from combined

north-to-south scan swaths with file sizes of about 19 MBytes. SeaWiFS GAC Level 2 is taken from Level 1A data that has been further processed, calibrated, and corrected. Unusual conditions may also be marked within the data. The National Science Foundation, the Office of Naval Research, and other organizations have provided support to a number of research and educational associations for GAC data. See Advanced Very High Resolution Radiometer. global area network GAN. A network that is accessible to most or all nations in the world. The Internet is the closest thing we have to a GAN, although it is not yet ubiquitous or accessible by all nations or people. Global Atmospheric Research Program GARP. A program in the 1970s to study atmospheric trends and patterns and to extend the range of daily weather forecasts over a longer period than was previously possible. The GARP Atlantic Tropical Experiment (GATE) was the first major experiment in the GARP, carried out in 1974. GATE is of interest, not only because it was international in scope, but because it involved intercommunication among a host of research ships, aircraft, and communications buoys. In the late 1970s and early 1980s, NOAA meteorological satellites were designed and launched to support the GARP. NOAA-7, for example, launched in 1981, had sensors for measuring the Earth’s atmosphere, surface, and cloud patterns. The GOES system of sensing satellites also form part of the GARP. See GOES. Global Atmosphere Watch GAW. A United Nations Commission for Atmospheric Sciences monitoring and assessment program that uses technology to track pollution, ozone, and other aspects of atmosphere composition around the world. Global Business Communications Systems GBCS. An AT&T business, which was rolled in with the AT&T Laboratory restructuring of Bell Laboratories in 1995-1996, along with the Network Systems Group, AT&T Paradyne, Microelectronics, and Consumer Products. GBCS is moving into the area of multimedia and secure telecommunications services. Products include a Unix-based server that works on a private branch exchange (PBX) to provide videoconferencing capabilities over data networks such as Ethernet and IBM Token-Ring. The server software is called Multimedia Communication Exchange (MMCX) and was implemented first on Unix stations, with the intention of porting it to PC operating systems. Global Change Master Directory GCMD. A NASA multidisciplinary database project originating from the Goddard Space Flight Center (GSFC) Global Change Data Center. The GCMD includes both national and international remote-sensing data sets contributed by more than 800 U.S. and worldwide organizations, including NOAA, NASA, DOE, NSF, EPA, USGS, educational institutions, and others. It is of interest to anyone interested in planet change, particularly climatic change. The data includes temporal and geographic information and some parts are interlinked with relevant external

information. The GCMD relational database is now searchable online through the GCMD Web site. The data is of particular interest to climatologists, agriculturalists, hydrographers, mineralogists, and others. http://gcmd.gsfc.nasa.gov/ Global Data Processing System GDPS. A system of preparing and disseminating cost-effective meteorological analyses and forecasts. The GDPS retrieves, assesses, decodes, sorts, and analyzes the data in preparing for making it available for distribution. GDPS is one of three integrated core components of the World Weather Watch (WWW) system. It is administrated by the World Meteorological Organization. GDPS data are valuable for weather forecasting and meteorologically related agriculture, climatology, and aeronautics industries. See Global Observing System, Global Telecommunication System. http://www.wmo.ch/web/www/DPS/gdps.html Global Development Gateway GDG. A major World Bank initiative proposed through the GDG Principles discussion forum hosted by Bellanet. The GDG is sponsored by the World Bank to promote information exchange, access, and development. global directory An internetwork computer database that stores various types of information related to the various networks. The information may be user login names and passwords, shared database resources, group member lists, device directories that can be accessed by more than one network, or pointers to various applications or documents common to the various networks. The Internet has a number of global directories of file databases, archives, etc. See Gopher, Archie, Veronica. Global Environmental Monitoring System GEMS. Administrated by the United Nations Environment Programme (UNEP), GEMS was established as part of the Earthwatch program in 1975 to support and strengthen environmental monitoring in participating countries and to improve the collection

and evaluation of environmental data. Computeracquired and -processed information is an important part of this effort. See Global Resource Information Database. global function plane GFP. An architecture within which the modular functionality for Intelligent Network (IN) services may be globally constructed. The GFP functions are described as service-independent building blocks (SIBs). The IN is viewed as a single entity within the GFP. GFP is defined in ITU-T Q.1201 which describes a generic IN GFP model, service-independent building blocks, and services and features offered through a global service logic. Global Incident Analysis Center GIAC. A SANS Institute center that creates and disseminates reports of malicious activity on the Internet submitted by system administrators and network security professionals worldwide. GIAC maintains a large archive of security-related papers available for free download. http://www.giac.org/ global information infrastructure GII. A term used since the mid-1990s by international standards committees with regard to goals, standardization, and development of global interconnected telecommunications systems, including the technology, applications, and related services. Global Information Infrastructure Commission GIIC. An independent, nongovernmental initiative inaugurated in July 1995 to promote leadership in the private sector and cooperation between private and public sectors in developing information services and networks. GIIC fosters economic growth, education, and quality of life through activities such as developing an accessible and diversified global information infrastructure. The GIIC operates as a project of the Center for Strategic and International Studies (CSIS). CSIS is a U.S.-based private organization founded in 1962 to conduct research in global public policy. http://www.giic.org/, http://www.csis.org/

GSM General Categories Category

Notes

Media

GSM works over frequency-modulated (FM) signals using a combination of time division multiple access (TDMA) and frequency division multiple access (FDMA). Peak output power varies with the type of transmitter (mobile station class), ranging from 0.8 to 20 watts. Frequency hopping is used to reduce interference and multipath fading, and encryption increases security. The data rate is 270 Kbps.

Transceiving There is a base transceiver station (BTS) associated with each cell operating on fixed frequencies unique to its region. Honeycomb-like clusters are handled by base station controllers (BSC), which, in turn, are controlled (routed, switched, handed over) by Mobile Service Switching Centers (MSC). Information

There are databases associated with GSM that aid in the administration of subscriber information and those that aid in the administration of security and associated authentication mechanisms. There is also an equipment identity register (EIR), which keeps track of equipment types and configuration, and can block calls on stolen units.

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Global Internet Liberty Campaign. A human rights group that includes the American Civil Liberties Union (ACLU), the Electronic Freedom Foundation (EFF), and other member organizations. Global Internet Project GIP. A private sector organization founded in 1996, consisting of senior level managers representing global software and telecommunications industries with high stakes in Internet development. As part of its activities, GIP encourages the education of world decision-makers in the potential evolution and uses of the Internet. http://www.gip.org/ Global Land Information System GLIS. An interactive database system developed by the U.S. Geological Survey (USGS). It provides data that is valuable in the study of the Earth’s land surfaces. Samples and information about GLIS products are available online. Topics within the GLIS database include climate, geology, hydrology, land cover, and others. There are aerial photographs, satellite images, and digital line graphs to serve a variety of needs. The aerial photographs, for example, include sources such as the National Aerial Photography Program, National High Altitude Photography, and various radar systems. http://www.earthexplorer.usgs.gov/ Global Maritime Distress and Safety System GMDSS. A maritime safety system which incorporates automated distress calls using Digital Selective Calling (DSC). In the late 1970s, maritime experts began to develop systems for updating safety and distress communications, resulting in the 1979 draft of the International Convention on Maritime Search and Rescue. GMDSS advocates a global search and rescue plan and a Global Maritime Distress and Safety System (GMDSS) as a communications infrastructure for the overall plan. The system is based upon a combination of Earth-based and satellitebased radio services, emphasizing ship-to-shore marine signaling through relatively user-friendly consoles. GMDSS signaling is quickly superseding the decades-old Morse code-based system. In addition to the automation of distress signals, it calls for the shipboard downloading of maritime safety information as a preventive measure. In 1996, the Telecommunications Act was written to encompass U.S. marine vessels, and ships were required to install GMDSS equipment by 1 Feb. 1999. All vessels subject to Chapter IV of the Safety of Life at Sea (SLOAS) convention must be fitted with GMDSS equipment (with stipulated exceptions) as must mobile offshore drilling units (MODUs). Implementation of GMDSS has not been without problems. It has been criticized for false alarms and general reliability problems, and many nations have been slow to adopt the system. See COSPAS/ SARSAT, NAVTEX. global mobile personal communications services GMPCS. A phrase coined by the ITU-T to describe mobile communications through low Earth orbit (LEO) satellite systems but later broadened to include other modes of mobile communications (geostationary FSS, MSS, “Little LEOs” and wideband LEOs). GMPCS was the discussion theme of the

World Telecommunication Policy Forum (WTPF), resulting in a set of principles and recommendations described in the “WTAC Report to the SecretaryGeneral [of the ITU-T] on GMPCS” in January 1996. Global Navigation Satellite System GLONASS, GNSS. A satellite system deployed by the Russian Federation defense department, which has much in common with the American Global Positioning Service (GPS) in terms of satellite placement and the types of information transmitted. The 24 GLONASS system satellites are orbiting in three planes. Unlike the GPS system, GLONASS claims to plan to use the same levels of signals for civilian (CSA) and government use (SA), and civilian use is guaranteed for about the next decade. By the late 1990s, the project had been divided into two stages: (1) GNSS-1, the first generation Russian GLONASS and U.S. GPS system and (2) GNSS-2, the second generation system including civil access with improved positioning and services. The MIT Lincoln Laboratory conducts research on the GLONASS system and reports progress and observations on the project on their Web site. http://vega.atc.ll.mit.edu/glonass/ Global Network Navigator GNN. A Web-based information service providing lists of and information about new services, sites, and related resources on the Internet. Global Observing System GOS. A system for obtaining standardized observations of the Earth’s atmosphere and ocean surfaces from ground, sea, air, and space-based observation platforms. GOS is one of three integrated core components of the World Weather Watch (WWW) system and is administrated by the World Meteorological Organization. GOS data are valuable in weather forecasting and meteorologically related agriculture, climatology, and aeronautics. Space data are available through the Environmental Observations Satellite (EOS) system comprised of five near-polar and five geostationary environmental observation satellites with a variety of imaging and sounding sensors. See Global Telecommunication System, Global Data Processing System. http://www.wmo.ch/web/www/OSY/GOS.html Global One An international commercial joint venture of Sprint, Deutsche Telekom, and France Telecom. Global Online Directory GOLD. A commercial product from VocalTec that works in conjunction with their Internet Phone software. Internet Phone lets you plug a microphone into your personal computer and use it as a phone transmitter to communicate with another person with Internet Phone capabilities. The computer speaker provides the equivalent of the phone receiver. Long-distance calls can be placed as though they were local calls through your ISP, without long-distance charges. Internet Phone connections are full duplex, connecting through the TCP/IP transport protocol. In addition to the features of a conventional phone call, chat lines and other digital enhancements are available. GOLD is the global directory that stores information about Internet Phone users who can be contacted, just

as the names of phone subscribers can be accessed through a phone directory. Global Ozone Monitoring Experiment GOME. A satellite-borne ozone European Space Agency (ESA) research project launched in April 1995 on board the European Remote Sensing Satellite (ERS-2). GOME is a nadir-viewing passive spectrometer that senses atmospheric trace constituents by measuring solar radiation scattered by Earth’s atmosphere. Cloud characteristics, aerosols, and surface reflection can also be measured. GOME is designed to sense in the visible and ultraviolet spectra from 240 to 790 nanometers. See GOME Data Processor. http://auc.dfd.dlr.de/GOME/ Global Positioning System GPS. A space- and ground-based 24-hour navigational system originally designed and used by the U.S. military (see Navy Navigation Satellite System), funded and maintained by the U.S. Department of Defense (DoD). It provides the means to monitor, update, and maintain orbiting satellite systems and to determine a location on or around the Earth through information from these systems. GPS uses the known positions of satellites as reference points for discerning unknown positions on or above the Earth. There are now over 20 satellites in the system (some are spares), more-or-less evenly spaced, orbiting in 12-hour cycles at an altitude of about 10,898 miles (about 400 miles higher than the original NNSS). A system of sophisticated ground stations with antennas, coordinated by a master control station, administers, deploys, and maintains the satellites and updates them when needed to correct for clock-bias errors. A variety of types of information can be computed from information from several satellites, including a location or position of a stationary or moving object, and coordination of time. This information can be incorporated into software applications in vehiclemounted or handheld positioning receivers. From military operations, to recreational navigation on the ocean in a kayak, to airline navigation, GPS provides a wealth of data with which to determine latitude and longitude, altitude, and velocity. This information can further be combined with maps to record or suggest routes. GPS satellites transmit timed binary pulses in addition to information constants about the current location of the satellite. The synchronized atomic clocks aboard the satellites permit the transmission of precise timing tags. The combination of the speed of transmitted electromagnetic waves and the atomic clocks installed in GPS satellites provides remarkably accurate timing pulses. The GPS Master Control Station (MCS) is operated by the 50th Space Wing’s 2nd Space Operations Squadron in Colorado. This squad is responsible for monitoring, controlling, and operating the GPS satellite constellation. The U.S. Air Force Space Command Space and Missile Systems Center in Los Angeles, California, is the executive agent for the Department of Defense (DOD) acquiring GPS satellites and equipment.

There are thousands of GPS users worldwide. Personal GPS devices can be purchased for as little as $180 to $450, and more sophisticated ones are used in all industries that rely on location information: airlines, shipping firms, ferries, military divisions, etc. For greater details on individual aspects of GPS, see differential GPS, EAGLE, Intelligent Vehicle Highway Systems, GPS Operational Constellation, GPS Navigation Message, local differential GPS, NAVSTAR, Precise Positioning Service, Standard Positioning Service, wide area differential GPS.

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NAVSTAR Global Positioning System (GPS) satellite from the 24-unit constellation of planes and satellites that provides military and civilian navigation and positioning data. The nine-ton satellites orbit the Earth every 12 hours, emitting continuous positional signals. The signals can be used to calculate time, location, and velocity, depending upon the capabilities of the GPS receiver. The system is controlled and operated by the 50th Space Wing out of Schriever AFB, Colorado. [U.S. Air Force Space Command image.]

Global Resource Information Database GRID. A global network of environmental data centers cooperating to generate and disseminate key environmental geo-referenced and statistical data sets and information products. GRID centers are equipped to prepare, analyze, and disseminate environmental data that may be used as the basis for environmental assessments. GRID is associated with the Earthwatch program and the Environment Assessment Division of the United Nations Environment Programme (UNEP). It was established in 1985, evolving gradually out of the 1972 United Nations Conference on the Human Environment held in Sweden. Following the conference, UNEP was created to provide a focus for a Global Environment Monitoring System (GEMS) that led to GRID. There are a number of GRID centers around the world, including in the U.S., South America, Europe, Russia, Nairobi (UNEP headquarters), Asia, and

New Zealand. For example, the United Nations Environment Programme (UNEP) and 1987 World Commission on Environment and Development project in cooperation with the Government of Norway established a GRID environmental information center in Arendal, Norway. GRID-Arendal was opened as a nonprofit foundation in August 1989; it communicates and cooperates with other GRID centers. global search and replace A function in text editing, word processing, and desktop publishing programs that allows the user to find and replace a selected entry throughout the entire document, which may span more than one file. Search-and-replace functions can be constrained in several ways, by limiting the changes to the highlighted (selected) text on the current page, or they may be global, to include the entire current document or a multifile document. Global Software Defined Network GSDN. A highvolume commercial virtual private network service from AT&T that utilizes AT&T’s Worldwide Intelligent Network (WIN) to interconnect networks in the U.S. and other countries. GSDN selects an economical route for external calls and provides internal services, including order entry, tracking, file transfers, and teleconferencing services. GSDN is aimed at business networks. Global Standards Collaboration GSC. A framework for the exchange of information regarding global standards development for interconnectivity and interoperability of systems and devices. Thus, the GSC has been bringing together senior officials from regional, national, and international standards bodies since 1988. Participating bodies include the International Telecommunication Union (ITU), the International Organization for Standardization (ISO), the European Telecommunications Standards Institute (ETSI), and others. Focal areas are discussed at large conferences. For example, global radio standardization was the key topic for the 2000 meeting in Sapporo, Japan. Other topics of current interest include number portability for mobile communications, universal personal telecommunications (UPT), and intelligent networks. http://www.gsc.etsi.org/ Global System for Mobile, Groupe Spéciale Mobile GSM. A digital cellular technology developed jointly by the telecommunications administrations of Europe. The Groupe Spéciale Mobile was founded in the early 1980s, and the Global System for Mobile (GSM) was first publicly announced in 1991 and has since been standardized in Europe and Japan. GSM was the first fully digital system to provide mobile voice connections, data transfer services, paging, and facsimile at full duplex or half duplex rates up to 9600 bps. GSM operates in two frequency ranges: 890 to 915 MHz for signaling information and 935 to 960 MHz for information transmissions. GSM is a set of standards specifying a digital mobile communications services infrastructure. It is based on a 900 MHz radio transmission technology and specifies related switching and signaling formats. An 1800 MHz Digital Cordless System (DCS) has also been added. Since mobile systems typically

support roaming, and since the multicultural makeup of Europe provides a unique challenge in providing compatible services, interoperability has been emphasized in the GSM specifications. GSM can be described in three categories: communications media, transceiving systems, and information systems, as shown in the GSM General Categories chart. The GSM subscriber identity module (SIM), also known as a smartcard, is a security feature which handles encryption and authentication. It includes memory storage which can be used for dialing codes or other information related to the service. The SIM is also a means to download and display call-related information. See Future Public Land Mobile Telecommunication System, Personal Communications Network. Global Telecommunication System GTS. A system of terrestrial and space-based data circuits for interconnecting meteorological telecommunications centers. GTS is one of three integrated core components of the World Weather Watch (WWW) system and is administrated by the World Meteorological Organization. GTS data are valuable in weather forecasting and meteorologically related agriculture, climatology, and aeronautics. The GTS provides rapid and reliable dissemination of observational meteorological data. The GTS is organized into a Main Telecommunication Network (MTN), Regional Meteorological Telecommunication Networks (RMTNs), and the National Meteorological Telecommunication Networks (NMTNs). The World Meteorological Centres (WMOs) are located in Russia, Australia, and Washington, D.C., and there are more than a dozen regional hubs in Asia, South America, Africa, Europe, and other locations. See Global Observing System, Global Data Processing System. http://www.wmo.ch/web/www/TEM/gts.html Global Title Translation GTT. A telephony and administration and routing function that enables added feature functionality in commercial systems such as Local Number Portability (LNP), calling card services, and mobile roaming support. GTT determines destination addresses in Signaling System 7 (SS7) and other relevant network systems. When a call is initiated, GTT determines the destination and may include additional information, depending on the feature service. GTT may support multiple global title addresses. Global Transaction Network GTN. AT&T’s extensive 800 service phone network, which was introduced in 1993. This service supports enhanced features, providing more flexible routing and numbering services which can be used, for example, by airline reservation systems. Globalstar A system of 48 small bent pipe communications satellites orbiting at 1400 kilometers (LEO), for providing voice and data services (data files, paging, facsimile). Globalstar was established in 1991 as a joint venture of Loral Space & Communications, Ltd., QUALCOMM, Inc., and a number of corporate partners. Launching began in

February 1998. In 1999, Globalstar launched four more systems, bringing the total satellites to 12. By 2000, the system was operational and the number of satellites increased to 48 over the next two years. Globalstar services can be accessed with vehiclemounted or handheld devices resembling cellular phones, and the system is integrated with cell phone services through dual-modem handsets. Remote users can access the system through Globalstar service providers, with fixed-position and wireline phones. Globalstar is intended to enhance rather than replace existing cellular and other phone services. Services are aimed at international business travelers, commercial vehicle operators, marine craft, field scientists, and others. The competitive aim is low cost for service and accessories. GLONASS Global Navigation Satellite System. A Russian Federation Global Positioning System similar to the U.S. NAVSTAR system. GLONASS is managed by the Russian Space Forces. GLONASS provides all-weather positioning coordinates, velocity references, and time information from virtually any point on or near the globe. More specifically, the GLONASS system aids in managing air and marine traffic, in supporting emergency and safety systems, geodesy, cartography, and ecological monitoring. Like the American GPS system, GLONASS is two-tiered. It provides standard precision navigation signals (SPs) with horizontal accuracy to about 63±6 meters and high-precision navigation signals (HPs) with authorization and specialized equipment. The GLONASS system has launched more than four dozen satellites since the first was put into operation in October 1982. Early satellites had a lifespan of about two years, while later satellites lasted about four or five years. In general, the launches have been successful, although in 1987 and 1988 there were a number of failures. Since 1989, the orbiting platforms have included geodetic reference satellites. In February 1999, the Russian Federation made an open declaration of increasing international cooperation with regard to national satellite navigation technologies and international navigation systems. The constellation status is reported, within a few days, on the GLONASS Web site. http://www.rssi.ru/SFCSIC/english.html Glossary of Telecommunications Terms, FCC A short glossary of telecommunications terms related mainly to delivery of broadcast services to consumers provided by the Federal Communications Commission (FCC). Glossary of Telecommunications Terms, Federal Standard Originally introduced in 1976 as MILSTD-188-120, this archive has evolved through several revisions to become the Telecom Glossary 2000. It is provided through the U.S. National Communications System in print, CD-ROM, and Web formats, with increasing emphasis on electronic development and dissemination. The Glossary is mandated for use by all Federal departments and agencies for the preparation of telecommunications documentation

and is available from the National Technical Information Service. Definitions from the previous standard were revised and updated by the FTSC Subcommittee to Revise FED-STD-1037B. The subsequent version, FEDSTD-1037C (1996), was further updated to Telecom Glossary 2000, with many of the new definitions drawn from T1 Standards and Reports. The Glossary includes standard definitions for telecommunications terms related to antennas, computers, transmissions media (e.g., fiber optics), networks, audio/video technologies, radio communications, etc. Sources include government publications and those of prominent telecommunications organizations including the ITU, ISO, and the American National Standards Institute. The Glossary has been reviewed by the National Communications System Member Organizations, the Federal Telecommunication Standards Committee members, members of relevant industries and Federal agencies, and by the general public. Telecom Glossary 2000 was discussed through members of the T1A1 Ad Hoc Glossary Group. GMDSS See Global Maritime Distress and Safety System. GMDSS Radio Maintainer License A license granted by the Federal Communications Commission (FCC) to maintain radiocommunications aboard ships that are equipped to comply with Global Maritime Distress and Safety System (GMDSS) regulations. It further confers the operating authority of the General Radiotelephone Operator License and the Marine Radio Operator Permit. A licensed maintainer is required by ships that conduct at-sea maintenance. The license requires FCC Element 1, Element 3, and Element 9 exams to be passed. GMDSS Radio Operator License A license granted by the Federal Communications Commission (FCC) to individuals deemed capable of handling radiocommunications aboard ships that are equipped to comply with Global Maritime Distress and Safety System (GMDSS) regulations. The licensee may operate basic equipment and make antenna adjustments. The license further confers the operating authority of a Marine Radio Operator Permit. Applicants are required to pass the Element 1 and Element 7 written exams. GMPCS See global mobile personal communications by satellite. GMR See giant magnetoresistance. GMS See Geostationary Meteorological Satellite. GMSK See Gaussian minimum shift keying. GNN See Global Network Navigator. GNOME An open source (freely available) user software environment and applications framework available to developers as part of the GNU project. GNOME is typically distributed with BSD and GNU/Linux distributions and is available for other platforms as well. The goal of the GNOME project is to provide a user-friendly graphical desktop environment and a

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developer-friendly base of tools for creating GNOME-compatible software applications to augment or replace commercial operating systems and development environments. As the project has evolved, it is also being extended to include a set of commonly used office productivity tools. One of the more interesting aspects of GNOME is that it can be internationalized in order to make it possible for developers around the globe to create applications in the language syntax that is most comfortable for them. One of the secondary goals of the GNOME project is to make GNOME developer tools and documentation available in every known world language (an ambitious goal but likely to result in a rich choice of options even if it is not literally achieved). GNOME also takes into consideration the maximizing of accessibility for people with disabilities, through the GNOME Accessibility Project. http://www.gnome.org/ GNSS See Global Navigation Satellite System. GNU Acronym for “GNU’s Not Unix!” A Unix work-alike developed under the aegis of Richard Stallman of the Free Software Foundation (FSF). See Free Software Foundation, GNOME. GNU as A GNU family of assemblers used to write software code for a variety of object file formats. The original GNU assembler for the Digital Equipment Corporation (DEC) VAX system was written by Dean Elsner. Many subsequent programmers and even some commercial vendors have enhanced and maintained the software. See Free Software Foundation. GNU C compiler GCC. A C compiler supporting ANSI standard C, C++, and Objective C. The GNU C library includes ANSI C, Unix, and POSIX functions. GNU Emacs A powerful, extensible, scriptable display editor distributed by Berkeley programmers with BSD, and by many other distributors and commercial vendors. Emacs is so powerful and so well liked by power editor users, many have half seriously referred to it as an operating system. The first Emacs was written in 1975 by Richard Stallman. GNU Emacs, which was enhanced by Stallman with true LISP integrated into the editor, was introduced in the mid-1980s. GNU Emacs is widely available on Unix systems. GNU graphics A set of graphics utilities for plotting scientific data, with support for GNU plot files on various systems and output devices, including PostScript, The X Window System, and Tektronix devices. GNU’s Bulletin A semiannual newsletter about various GNU projects, produced and distributed by the Free Software Foundation. go local A command to instruct software to connect to a local connection (usually in the same room or vicinity), usually through a serial null modem interface. Godwin’s law “As a USENET discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches one.” The implication is

that a long discussion eventually degrades to the point that it is no longer productive. GO-MVIP Global Organization for Multi-Vendor Integration Protocol. GO-MVIP is a nonprofit trade association which took over the development and promotion of MVIP in 1994, in order to assure its development and maintenance as a practical, robust common integration standard. GO-MVIP seeks to continue to develop and establish the design specifications for further versions of MVIP. See MVIP. http://www.mvip.org/

An artist’s conception of an EROS meteorological satellite system, which was essentially the concept for the GOES satellites. This April 1961 drawing indicates the field of view and orientation of the proposed AEROS geostationary satellite. [NOAA In Space Collection image.]

An example of a visible image from the GOES 8 satellite on 16 July 2001 with a line drawing of North America and parts of Central and South America superimposed to aid in locating geographical features. [NOAA FSL image.]

GOES Geostationary Operational Environmental Satellite. A geosynchronous satellite system providing environmental monitoring data to various governmental organizations and the public. GOES systems began broadcasting, as we know it today, in 1974, having evolved out of early SMS- weather satellite systems. Almost a dozen satellites were launched between the early 1968 magnetometer and

infrared sensor-equipped satellites and the more sophisticated multisensor satellites of the late 1990s. With each launch, adjustments and improvements have been made to the systems. Vertical temperature and moisture sensors were added to GOES-4, and additional signal relay capabilities were added to later GOES systems. The original GOES satellites were spin controlled, meaning that they used the physics of spinning to maintain attitude control. Since the mid-1990s, however, with the launching of GOES-8, the configuration has changed to a threeaxis-stabilized system. This configuration changed not only attitude control, but also the means by which the sensors were installed and operated. Doppler radar sensors were added to the more recent satellites and have become an indispensable aspect of creating and interpreting weather maps. The Pacific GOES has been used for operating the Pan-Pacific Educational and Cultural Experiments (PEACESAT) to enhance medical, cultural, and educational resources in the Pacific island nations. GOES data is available to the Command and Data Acquisition Station, the National Weather Service, the Forecast Systems Laboratory (FSL) of the National Oceanic and Atmospheric Administration (NOAA), and many others. NOAA handles the operations of the satellites. GOES sensors provide continuous weather monitoring along with information that can be used to estimate rainfall during more violent storms (e.g, hurricanes) and snow accumulations and cover. Ice flows on large bodies of water can also be monitored with GOES data. Even the weather in space, in terms of various magnetic and energy particles, is monitored by GOES sensors. The GOES Space Environment Monitor (SEM) mission provides a better understanding of space weather through the National Space Weather Program. Space weather forecasts aid not only in probe, shuttle, and satellite missions, but also in providing valuable cosmological information to physicists and astronomers. Satellite images with a variety of characteristics (visible, infrared, water vapor, etc.) from GOES sensors are available through the Forecast Systems Laboratory. gold A malleable, metallic chemical element with high conductivity, which makes it useful for specialized electrical applications. Gold contacts are often found on sensitive electronics connectors in the computer and video industries. Copper and silver are also good conductors, with copper being the most widely used for electrical installations. GOLD See Global Online Directory. gold disk, gold disc 1. The master or final copy of a product (software, music CD, laserdisc, etc.) from which mass production replicas are made. 2. A special limited edition distribution. Collectors’ edition. Gold disc music CDs sometimes are marketed as higher quality pressings with special inserts and special tracks that may not be included on a regular copy of the CD. gold number, custom number, vanity number A phone number specifically selected so that it is easy to remember, particularly if the letters associated

with the number spell out a word or other mnemonic. There is typically an extra fee associated with getting a gold number. Sometimes people get lucky, and their number just happens to be easy to remember or to spell something interesting. Goldstone Deep Space Communication Complex One of the complexes of the NASA Deep Space Network (DSN) that provides radio communications for interplanetary spacecraft. The complex is further used for radio astronomy and radar observations of our solar system and the universe beyond. Other complexes in the Network are located in Madrid, Spain, and Canberra, Australia. See Deep Space Network.

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Large beam waveguide parabolic antennas at the Goldstone Deep Space Communication Complex in the Mojave Desert in Goldstone, California. The 34meter dishes are used for astronomical research and radio space communications. [NASA/JPL image, 1990.]

golfball printer, daisy wheel A printer with a round, rotating, impact printhead like those found on IBM Selectric typewriters and daisy wheel computer printers. The rotating head is embossed with the character set and impacts with the printing ribbon causing particles, dyes, or inks to be deposited on the print medium. GOME See Global Ozone Monitoring Experiment. GOME Data Processor GDP. A ground segment system designed to process data from the satellitebased Global Ozone Monitoring Experiment (GOME). Raw data is processed by the GDP into Level 1 radiances/reflectances and Level 2 trace gas quantities data that are made available to interested parties. A number of images and other data sets are also available, some of which may be downloaded by FTP. The GDP was jointly designed and developed by German, Dutch, and U.S. organizations and is administrated by the European Space Agency (ESA). Processing is handled at the DFD, the German Remote-Sensing Data Center. See Global Ozone Monitoring Experiment. GOMS See Geostationary Operational Meteorological Satellite. Gooch, Daniel (1816-1889) An English locomotive engineer and businessman who aided in the installation of the first successful permanent telegraph

cable link between North America and the British Isles. At a relatively young age, Gooch was appointed the locomotive superintendent of the Great Western Railway (GWR). In 1840, Gooch contacted gifted engineering designer Isambard K. Brunel about designing an engine works for GWR (this association between the two talented engineers was to take an interesting turn more than a decade later). Using new technology and the results of experiments in atmospheric resistance, Gooch designed locomotives that could travel at faster speeds than previous models. He was also a supporter of wide gauge technology, despite the trend to smaller gauges. Gooch designed more than 300 locomotives in his career as an engineer. In the 1860s, Gooch resigned his position with GWR to put his efforts into telegraphic communications. He became Chairman of the Telegraph Construction and Maintenance Company and a director of the Anglo-American Company. In the meantime, Brunel had been designing the Great Eastern (originally the Leviathon). The Great Eastern was purchased by Gooch and his colleagues for cable laying and was instrumental in laying the first transatlantic communications cable, the feat that Gooch is best known for, despite his many other accomplishments. See Great Eastern. good condition In many rating systems, good condition indicates a product with minimal abrasions from wear and tear, and mechanisms that are in good working order. Good condition does not imply any information about the age of the product or its remaining useful life. Often sandwiched between fair condition and excellent or like new condition. goodput A generic measurement of network data successfully received, effective throughput; in contrast, discarded cells, or transmitted cells in a congested link, are called badput. See cell rate, throughput. Goodwin, Hannibal (1822-1900) An American minister and inventor who created celluloid film in 1885 and received a patent for rollable film in 1887. For many years, motion picture films were known as celluloids, and individual animation frames used to create frame-by-frame animation are still known by the abbreviated form cells. gopher The command for initiating a Gopher client on a text-based system is “gopher” (all lower case), and “xgopher” is a similar client command that works with The X Window System. See Gopher. Gopher A document system developed by P. Lindner, M. McCahill, B. Alberti, F. Anklesaria, and D. Torrey at the University of Minnesota in the early 1990s to provide a local campus information server. The Gopher service quickly grew to become a worldwide resource. It is a client/server distributed document delivery system, i.e., a means of locating information on the Internet through a simple menu-like text interface (or graphical Gopher client) or of sending information through electronic mail. It is also possible to set bookmarks, Gopher information locations that are frequently used. Links to various Gopher servers together comprise a virtual community

known as Gopherspace. The Gopher text menu interface is being superseded by graphical Web interfaces. See Veronica, RFC 1436. Gopherspace The Gopher document system is composed of many widely distributed document repositories and Internet services in Cyberspace. Hence, the Gopher facilities online are called “Gopherspace” by many their users. See Gopher. GORIZONT A Russian geostationary telecommunications satellite launched in 1996. GoS grade of service. A phrase to describe service levels, which usually are individually defined on an industry basis. See class of service. GOS See Global Observing System. GOSIP Government Open Systems Interconnection Profile. A U.S. government version of the Open Systems Interconnection system which is required in many government data network installations. Gosling, James Gosling is best known for his contributions to the Java programming language, developed at Sun Microsystems, Inc. He was associated with Bill Joy, Mike Sheradin, and Patrick Naughton on Project Stealth in 1991. Project Stealth’s goal was to develop a distributed network in which the various electronic devices could intercommunicate. See Java; Joy, William. Government Emergency Telecommunications Service GETS. A service of the U.S. National Communications System for meeting national security and emergency preparedness (NS/EP) requirements for the use of public, defense, or federal telephone networks by authorized users. GETS provides emergency access and processing in local and long-distance telephone networks through a dialing plan and personal identification number (PIN). GETS services are provided through major long-distance networks, local networks, and leased networks through a universal access number and common telephone devices (desk phone, cell, phone, fax line, etc.). Once authenticated through the PIN, the caller receives special handling that may include priority and/or enhanced routing. See National Communications System. http://gets.ncs.gov/ Government Information Locator Service GILS. An ISO standard metadata scheme for describing government information resources with the intent of streamlining the management of information for efficient search and retrieval. GILS is an open, costeffective, scalable data standard to facilitate the search for collections of information and specific information within a collection. GILS extensions allow specific categories of data to be managed and searched. GILS is based on the ISO 23950 search standard and can be approached in somewhat the same way as information searching may be approached in a reference library. See Dublin Core, International Development Markup Language. http://www.access.gpo.gov/su_docs/gils/index.html GPF See general protection fault. GPRS See General Packet Radio Service. GPS See Global Positioning System. GPS Control Segment A general overall category

of the GPS system which comprises a main tracking station, in Falcon Air Force Base, Colorado, and subsidiary tracking stations worldwide as part of the U.S. Department of Defense’s Global Positioning System. The tracking stations take the signals from the satellites and incorporate them into orbital models that are further used to compute precise, individual, orbital data and clock corrections. Portions of this orbital ephemeris are sent via radio transmissions to GPS receivers. See GPS Space Segment, GPS User Segment. GPS Navigation Data Satellites in the Global Positioning System (GPS) send out two microwave carrier signals, one of which provides navigation information in the form of a series of time-lagged data frames sent over a specific time period. Subframes are also included for checking data integrity. The satellites are equipped with atomic clocks, and clock data parameters are sent and related to GPS time. Orbits are described by transmitting regularly updated ephemeris data. See Global Positioning System, Universal Coordinated Time. GPS Operational Constellation The system of over 20 more-or-less evenly spaced, orbiting satellites (some of which are spares), equipped with atomic clocks, in the Global Positioning System (GPS) Space Segment. These satellites orbit the Earth twice a day at about 11,000 miles altitude, transmitting information used in the U.S. Department of Defense’s Global Positioning System. The orbital planes are inclined at about 55 degrees in relation to Earth’s equatorial plane. From any one point on Earth, it is generally possible to locate between five and eight satellites, four or five of which are typically used to compute location and timing information. The satellites transmit two microwave carrier signals; the L1 frequencies carry the navigation message (with data describing the orbit and clock parameters) and SPS code signals, and the L2 frequencies monitor ionospheric delay of PPS receivers. See Global Positioning System. GPS receiver/display A fixed or mobile Global Positioning System (GPS) device that interprets GPS information and computes graphics, text, locations, maps, or other displays that provide the user information about position, time, and sometimes velocity. A graphical display of latitude and longitude is common. Receivers vary from room-sized systems to small handheld units from $180 up to hundreds of thousands of dollars. GPS consoles are used by surveyors, have been combined with map databases to provide car consoles, and have also been incorporated into ‘smart cars’ that can steer themselves. It is not unrealistic to predict that someday small GPS systems will be designed into wristwatch-style personal locators for travellers, sales representatives, hikers, et al. See Global Positioning System, Intelligent Vehicle Highway System. GPS Space Segment A general overall category of the GPS system that consists of GPS satellites deployed and administered by the U.S. Department of Defense as part of its Global Positioning System. See GPS Control Segment, GPS User Segment.

GPS translator A Global Positioning System translating capability to support technologies that require precise positioning and trajectory tracking data. This type of data is of importance to missiles and rockets and other high-velocity acceleration devices. Translator GPS systems support midcourse corrections, safety operations, and downrange tracking. They are a cost-effective option to certain radar tracking systems and a higher-accuracy option to portable GPS receiver systems. A vehicle or interceptor device installed with a GPS translator captures the GPS signals, translates them to an appropriate communications frequency, and transmits them to a ground-based station for further processing. The use of ground-based stations also makes it possible to store the data in larger storage media for subsequent playback and analysis, a capability that is impractical in most on-site GPS devices. IEC is a commercial vendor of GPS translators that has been providing and developing the technology since the 1980s. It has supplied translator systems to both the U.S. Navy and the U.S. Air Force. IEC has recently introduced a family of digital GPS translators that can support encryption for greater security, and it is developing a smaller, more powerful Translated GPS Range System (TGRS), in cooperation with the Air Force. GPS User Segment A general overall category of the GPS system that includes GPS receivers and users of the U.S. Department of Defense’s Global Positioning System. See GPS Control Segment, GPS Space Segment. GR generic requirement. grabber colloq. A graphical user interface (GUI) tool that looks like a little hand, and is used to grab or otherwise activate or drag screen elements. Commonly seen on Macintosh computer applications. graceful close A program or process that shuts down cleanly, with no stray windows, files, buffers, or problems. On many single user computers, shutting off the system may leave stray files or applications in a state that is different from the ideal closing state. On these, there may be a system shutdown selection (e.g., Macintosh), which cleans up before shutting off the computer. In layer-oriented networks, graceful close refers to a connection that is terminated at the transport layer with no loss of data. Grade 1 to 5 twisted pair See twisted pair cable. Grade B signal A radio-frequency broadcasting signal defined by the Federal Communications Commission (FCC). It is a measure of the strength of a television broadcasting station’s signal at a specific location. The purpose of the rating is to define minimum acceptable standards of quality for viewing purposes in the context of defining whether a specific subscriber is served or unserved by the signal. When the Satellite Home Viewer Improvement Act (SHVIA) was passed in 1999, it included a requirement that the FCC re-evaluate the Grade B signal standard to determine if it should be changed or replaced with something else for determining whether

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a household is unserved (unable to receive a signal of an acceptable level). Since it is impractical to go out and measure radio signal strengths in the vicinity of every subscriber in the U.S., the FCC created a computer model for satellite companies and television stations to predict whether a given household is served or unserved. This computer model went through several versions in order to include the effects of buildings, terrain, and land cover variations that could impede radio-frequency signals. If the predicted model is under dispute, a person may request a waiver from local TV stations serving the area. If the waiver is granted, the person becomes eligible to receive distant signals. If the parties cannot agree whether a subscriber is served or unserved, the American Relay Radio League (ARRL) has been designated as an independent, neutral entity for the purpose of arbitration and designating the party, with input from the satellite provider and TV station, to conduct an actual field test of signal strength. grade of service GoS. A service level indicator evaluated on an industry basis according to the type of service provided. In some industries a hierarchical category scale is applied to various levels or definitions of service. In telecommunications, grade of service is typically described in statistical terms related to the speed and probability of connecting, and the characteristics of the connection, etc. See class of service, quality of service. gradient Gradual change in elevation, color, or texture along an axis. Gradual blend or transition. See gradient fill. gradient fill A common feature of paint programs that allows the user to fill a defined area with graduated tones ranging from one specified color or shade of gray to another. The number of colors in the palette and the two end-tones selected will affect the smoothness and visual appeal of the transition, with more tones generally creating a more pleasing effect. Radial fills can be used to simulate 3D surface areas, as lighter areas appear as highlights. Graham Act A U.S. 1921 act in which telephone companies were granted exemptions to the provisions of the Sherman Antitrust Act. It enabled AT&T, more than any other company, to expand and exert further monopolistic control over the telephone networks. See the Kingsbury Commitment, Modified Final Judgment. Gramme, Zénobe Théophile (1826-1901) A Belgian engineer who emigrated to France, Gramme developed a direct current (DC) generator, featuring a ring armature in 1869 and 1870. Together with Hippolyte Fontaine, Gramme opened a factory called Societé des Machines Magneto-Electriques Gramme. In 1873, at the Vienna Exposition, it was noticed by a mechanic that an electrical connection from another generator could power the armature of the first generator, thus exhibiting the characteristics of a motor. It was an important historical advancement in industrial and transportation technologies. Gramophone, Gram-O-phone A phonograph technology patented by Emile Berliner in 1888, three

years after the introduction of the Graphophone by Bell and Tainter. The Gramophone used a flat 7-in. disk with lateral grooves, the earliest of which were single sided. It played at 70 rpm, and the playing time was about 2 or 3 minutes, the same as an Edison cylinder. The model E, introduced in the early 1900s, played at 78 rpm on 7-in. disks. See Graphophone, phonograph, phonograph record.

A Gramophone developed by Canadian inventor Emile Berliner in 1888. It could play for about 2 or 3 minutes at 70 rpm. [Classic Concepts image.]

grandfather clause A previously existing object, structure, statute, ownership right, or policy that may continue despite subsequent restrictions or regulations that would prevent its creation or continuance. A grandfather clause grants a type of pardon, special permission, or immunity. For example, military surplus purchased by a civilian in the 1960s may be regulated in the 1990s such that similar items may not be purchasable by current civilians (such as radiation bunkers). If the ownership is protected by a grandfather clause, when restrictions are imposed or reinstated, current civilian owners might not have to give up the property (but also may not be able to sell it, except perhaps back to the government). Building codes are often subject to grandfather clauses. If you purchase a house built in 1920, it may not be subject to the same offset, materials, or safety regulations as current structures. Voting and immigration laws have certain grandfather clauses. Immigrants to the country prior to a certain date do not require the same documents and eligibility requirements as later immigrants. In telecommunications, phones and various electronic components built or installed before a certain date may not have to meet all current Federal Communications Commission (FCC) regulations. grandfathered in Instated or installed before certain restrictions or regulations were put in place that would otherwise prevent creation, installation, or operation. See grandfather clause. graphechon A special-purpose memory electron tube used in computer and radar applications. The graphechon can store an electrical charge pattern,

similar to the functioning of an iconoscope, and recover the pattern at different scanning rates. graphic equalizer A component providing a set of controls for adjusting the tonal qualities at several frequencies in an audio system, usually a music system. The equalizer is not a stand-alone component; it works in conjunction with other components such as receivers, phonographs, tape players, CD players, etc. It frequently has a series of vertical analog sliders for making individual adjustments. Graphical Kernel System GKS. An official standard for 2D graphics in the mid-1980s, evolved from the Core. A 3D extension was subsequently developed, and GKS-3D became a standard in 1988. See Core, PHIGS. graphical user interface GUI. A way of facilitating communication between a human and a device, usually a computing machine, by presenting the information in the form of visual metaphors. A graphical user interface works in conjunction with a variety of physical input devices, including speech recognition hardware, mice, keyboards, stylus pens, touchscreens, and joysticks. They provide a means to select and control the various visual elements, which commonly include menus, drag bars, buttons, icons, and window gadgets. Video games like Pong were early electronic adaptations of simple GUIs. Many of the earliest applied GUI ideas in general use today were developed at Xerox PARC and incorporated by Apple Computer into the Macintosh operating system. graphics accelerator A chip or circuit board integrated into a computer system to relieve the CPU of some of the functions related to the processing and display of graphics. Graphics tend to be computing intensive, and sharing the load can significantly speed the display and refresh of images. Graphics accelerators are often sold as peripheral cards that can be plugged into a slot. See graphics coprocessor. graphics character A character displayed on a computer screen in terms of its rasterized (or sometimes vectorized) shape. Some systems display characters out of a storage bank which is preset, and may not be configurable. The old TRS-80 Model I computers shipped with upper case letters only. If you wanted upper and lower case characters, you had to install an optional chip in place of the character chip that came with the system. These hard-wired characters displayed quickly but were not very flexible. In subsequent systems, the characters on the screen were displayed as though they were images, even if they were text characters, making it possible to greatly vary the size, shape, and proportions of the letters and symbols. graphics controller, graphics display processor Specialized computer hardware to improve raster displays by taking some of the load from the CPU. Graphics controllers can speed up scan conversion, and the composition, display, and movement of graphics images and primitives. See cathode ray tube, frame buffer. graphics coprocessor A chip designed to speed computer graphics composition, display, or refresh by

sharing the load with the system CPU. Coprocessors are sometimes designed for very specific tasks, such as updating a screen, or storing and displaying graphics primitives, hardware sprites, and the like. Unlike graphics accelerators, which are often sold to consumers as optional system-enhancing peripherals, graphics coprocessors are more commonly sold integrated into the system, often on the motherboard. See graphics accelerator. graphics device interface GDI. Physical and virtual connections between graphics hardware components and the computer CPU. Since graphics applications tend to be CPU intensive, it is very common for other graphics hardware (accelerator cards, frame buffers, blitters, etc.) to be incorporated into a system to facilitate the fast creation, display, and refresh of images on a variety of output devices. graphics engine The part of a computer architecture supporting the graphics functions of the machine, particularly graphics composition, buffering, display, and fast refresh. Graphics engines are typically designed to handle many of the functions in hardware, so there is a minimum of on-the-spot software calculations. Enhanced graphics standards and graphics engines are being developed to support features such as realtime animation; hardware pan, zoom, compression/decompression; instant resolutionswitching; and video signal support. Graphics Environment Manager GEM. An early graphic user interface (GUI) developed by Gary Kildall’s Digital Research, the same company that created the popular CP/M text-based operating system in the 1970s. GEM was first demonstrated publicly at the COMDEX computer industry trade show in 1983 and shipped a few months later. The interface greatly resembled the Macintosh interface that Apple had developed after observing development research at the Xerox PARC laboratories. GEM did not become widely distributed, with the exception of providing a front-end to Xerox’s Ventura Publisher, a desktop publishing programming that was widely used for documentation page layout on Intelbased microcomputers in the later 1980s. Graphics Interchange Format GIF. (GIF ought to be pronounced “gif” given that the G stands for “graphics,” but its author apparently uses “jif.”) A proprietary raster graphics format introduced by CompuServe, Inc. in 1987. GIF is an 8-bit graphics format developed with the patented Lempel-ZivWelch (LZW) compression, whose implementation requires a royalty agreement from Unisys Corporation. The level of compression varies with the type of image and number of colors, but 3 or 4 times compression ratios are common on a typical color image. Due to patent issues, CompuServe agreed in 1994 to secure a license agreement to distribute the LZW technology and issued the Graphics Interchange Format Developer Agreement to provide software developers permissions under CompuServe’s software license agreement with Unisys. GIF is particularly suitable for images that have a small number of distinct colors, as opposed to images that have a great variety of subtle color changes.

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It also handles line art, grayscale images (through color palette gray matching), and sharp color boundaries better than formats optimized for other characteristics. Because GIF is a 256-color format rather than a 24-bit color format (~1.6 million colors), 24bit images will be dithered and adjusted and may not fully satisfy the needs of the user. GIF will support transparency, which is sometimes desired in order for a background image to be displayed behind the GIF image or through parts of the GIF image as though there were holes. Transparency is often used by Web designers to produce special effects in Web pages, such as buttons with irregularly shaped edges. GIF is one of the three most common graphics formats supported by World Wide Web browsers, the other two being PNG and JPEG. PNG is an open, nonproprietary format, developed to supersede GIF. In January 1995, CompuServe announced the GIF24 project for designing a replacement format for the original 8-bit GIF, and a month later officially announced that Portable Network Graphics (PNG) would be used as the basis for GIF24. Support services for GIF users is provided in the form of the CompuServe Graphics Support Forum (GO GRAPHSUPPORT). It is CompuServe’s central distribution area for GIF-related information. See Lempel-Ziv-Welch, Portable Network Graphics. VHS Super-VHS Hi-8mm CD+G laserdisc

The variety of standardized recording and playback media for graphics and multimedia products is increasing. Some of the more common formats supporting both images and sound are shown here. It may be that DVD-related formats, which hold more information in less space, will eventually supersede most or all of the above technologies.

graphics library GL. The writing of graphics routines for computers is time intensive and specialized. For that reason, many companies decide to purchase graphics libraries rather than to write their own. These library routines consist of a collection of commonly used graphics primitives and actions (lines,

circles, dots, fills, patterns, etc.) that can be dynamically called from the graphics library or compiled and linked into the software executables as needed. graphics mode A setting on dual-display mode systems (typically older IBM-compatibles) that permits the access and display of individually addressable pixels for the rendering of images and graphics characters. Some systems distinguish between text and graphics modes and will display only in one mode or the other. With faster processors, the trend is toward the more flexible graphics modes, with graphics characters. This frees the user from having to select a mode and switch between them. Graphophone A phonograph system patented in the 1880s by Chichester Bell and Charles Tainter, in competition with Thomas Edison. The Graphophone used wax cylinders recorded with vertical grooves. Edison later responded by creating wax cylinders but was not able to commercially mass-produce them. The products were sold by the Columbia Phonograph Company. See Gramophone, phonograph, phonograph record. graticule A diagnostic and measurement screen used in conjunction with cathode ray tubes (CRTs). The screen is calibrated and placed on the front of the tube, with the tube image showing through so the relationship of the displayed image to the screen can be observed. grating A series of narrow slits or grooves specifically designed and oriented so that they will reflect electromagnetic waves in a spread pattern. Antenna reflectors sometimes incorporate a grating design. gravity cell, crowfoot cell A type of voltaic wet cell suitable for providing small currents at a constant electromotive force. It derives its name from the way the lower and upper chemical solutions (e.g., copper sulphate over zinc sulphate) align themselves in relation to each other. Gray, Elisha (1835-1901) A physicist and inventor who developed many early telegraph technologies at about the same time Alexander Graham Bell was working to develop a harmonic telegraph. Gray was mechanically apt and had publicly demonstrated an early version of a harmonic telegraph, a device to send tones over wire, before Bell applied for a patent for his version. Gray filed a caveat for a patent the same day as Bell filed for the patent on what is now considered to be the first telephone, thought of as a speaking telegraph at the time. In 1867, Gray developed a new telegraph relay instrument. In conjunction with his partner, Enos M. Barton, Gray organized the Western Electric Manufacturing Company in 1869 and expanded by buying out the Ottawa, Illinois Western Union offices. Late in 1873, Gray reports having noticed different vibratory properties in human tissue (an idea pioneered by Meucci) and described the placing of a galvanometer in the circuit with a microphone for transmitting human speech through wires. This observation resulted in a patent application that was not accepted until three years later as Gray had to substitute animal tissue for human to satisfy the Patent Office. Gray filed a patent similar to Bell’s only hours

after Bell, and his company was later purchased by Bell. In the 1880s, telegraphs that would transmit handwriting were developed and Gray patented a telautograph which could lift the pen between letters permitting more natural characters to be transcribed, and sold the rights to a company founded with his name. See telephone history. Gray, Stephen (1666-1736) An English experimenter who authored an article for Philosophical Transactions in 1720, describing various investigations of attractive properties and light-producing properties of various “electrics.” He discovered that a substance electrified by friction could pass this property to another substance. He enlarged on the prior work of Gilbert, demonstrating that Gilbert’s “non-electrics” could conduct electricity from one body to another and could be electrified if insulated with a conductor. His association with the Royal Society of London indicates that he was likely familiar with the work and writings of F. Hauksbee, and he continued some of the interesting lines of inquiry first investigated by Hauksbee. In the late 1720s, Gray began a fruitful collaboration with Granville Wheler, a member of the Royal Society. Gray and Wheler were to discover that substances could be roughly divided into additional substances that readily conducted “electric virtues” and those that did not. See inductance.

Enos Barton helped establish Gray & Barton, the forerunner to Graybar Electric Company, Inc., in partnership with Elisha Gray.

Gray & Barton A telecommunications company established by Elisha Gray and Enos Barton in 1869 when Elisha Gray bought out George Shawk’s interest in the partnership. The physical facility was an electric shop abandoned by the Western Union Telegraph Company. In 1872, it became Western Electric Company, which supplied components to the Western Union Telegraph Company and later became an exclusive manufacturer for the Bell System. See Graybar Electric Company, Inc.; Western Electric Company.

gray market product One of several types of products that are not fully endorsed by the manufacturer. Examples include a product sold by an unauthorized distributor; a product that might be second rate in some way, which normally wouldn’t be sold by reputable dealers; or a return item that is promoted as being new. In electronics, beware of gray market products from questionable vendors. Find out the history of the company, the warranty terms, and ask if the company deals in gray market products, especially if the price is too good to be true. gray scale See grayscale. Gray Telephone Pay Station Company A company formed to commercialize the rotary payphones that were common from about 1930 to the 1960s. Graybar Electric Company, Inc. A spinoff of the Western Electric Company in 1925, this company handled electrical distribution. The name derives from the original founders of the Gray & Barton company, founded by Elisha Gray and Enos Barton in 1869. In 1928-1929, the employees purchased the company from Western Electric Company, and it is still one of the largest employee-owned companies in the United States. Graybar Electric continues to do business after more than sixty years, globally supplying almost a million different electrical and telecommunications products. See Gray & Barton, Western Electric Company. grayline The region in any particular place where the Sun is rising or setting. This information is of interest to those trying to determine a radio signal transmissions path using the characteristics of the Earth’s ionosphere to help propagate the signal. There are software programs containing extensive databases of thousands of cities, designed to generate a grayline chart and display a world clock to assist amateur and professional radio operators in sending and receiving radio communications. Some grayline generators also include azimuth projection maps (Great Circle maps) which can help the user determine where radio signals may be arriving from different parts of the world, depending upon location and time of day. See ionosphere. grayscale Visual information represented in shades of gray, i.e., with no color. In computing terms, many people confuse the terms monochrome and grayscale. Monochrome refers to one active color, whether it be white, black, green, or amber. Many older computer monitors were monochrome monitors. Grayscale refers to two or more (usually 8, 16, or 32) shades of gray typically ranging between white and black. Grayscale monitors are less expensive than color and are very suitable for desktop publishing and other black and white and grayscale printrelated applications. grayscale monitor A monitor capable of displaying a variety of levels of intensity, perceived as shades of gray. Most grayscale monitors can display from 16 to 64 levels of gray, though 32 is comfortable for viewing tones and details. A grayscale monitor is not the same as a monochrome monitor (sometimes imprecisely called a black and white monitor), which has pixels of the same intensity (on or off, and light

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or dark, depending upon the brightness setting), which are usually white, green, or amber. See monochrome monitor. great circle In geometry, an imaginary circle on the surface of a sphere that is defined as the intersection of the surface and a plane passing through the center of that sphere. See Great Circle. Great Circle The name given to routes based upon Earth’s spherical geometry, the Great Circle is a navigational concept to describe the shortest distance over the Earth’s surface (assuming it was flat) between two specified points. Airlines use Great Circle routes to minimize travel distances, especially over long distances. The polar aircraft route from Vancouver, BC on the west coast of North America, which passes over Greenland and Iceland, to London or Amsterdam is roughly a Great Circle route. Great Circle geometry is also of interest to radio operators sending and receiving signals that are propagated through the Earth’s ionosphere. See grayline, great circle. Great Eastern A massive six-masted coal-powered paddlewheeler constructed in London between 1854 and 1858. The ship measured almost 700 feet in length and 120 feet in breadth. It was originally a passenger ship but was not financially successful in this role. Later it was purchased at auction by Daniel Gooch and his colleagues, Cyrus W. Field and Brassey, and outfitted for laying cable, a role that better suited the vessel. Large cable tanks were installed for storing and spooling the communications cable. In July 1865, the ship was used in an unsuccessful attempt to lay the transatlantic cable. A year later, the ship left Ireland with almost 3,000 nautical miles of cable in her hold, spooling more than half of it into the ocean over the next two weeks before docking in Newfoundland, Canada, and finally establishing the first permanent, successful telegraph cable to link the British Isles and North America. See Gooch, Daniel; transatlantic cable.

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12345678901 A design and layout 12345678901 12345678901 term referring to a 12345678901 12345678901 block of text that is 12345678901 inserted into a design 12345678901 12345678901 12345678901 as a spacesaver to 12345678901 represent the text to 12345678901 12345678901 be inserted later. ipso 12345678901 facto pro bono ad infinitum tempis fug

Often an ad layout is designed visually 1234 1234 1234 before the content is ready for 1234 insertion. A newspaper story may be 1234 1234 laid out before the writer has finished 1234 1234 editing the copy. Later, the finished text 1234 1234 1234 is substituted for the greeked text ipso 1234 facto pro bono ad infinitum temp i

greeking A design and layout term referring to a block of text that is inserted into a design to indicate the presence of text and to serve as a spacesaver until the actual copy or content is available. Often an

ad layout is designed visually before the content is ready for insertion or a Web page is laid out before all the content has been proofed. In these circumstances, particularly in electronic layout, “dummy text” (frequently Greek or Latin characters or nonsensical text) is placed in the text box to indicate size, shape, and typefaces, or to help in visualizing and selecting these components. green 1. Young, inexperienced, naive, not hardened or aged. 2. Ecological, environmentally friendly, resource-conserving (as in power saver systems). Green products are represented as being kinder to the environment in terms of resource use, manufacture, materials (low in toxic materials or by-products), or operation than similar products by other manufacturers. See ISO 14000. Green Book 1. The most technical of the three PostScript reference books produced by Adobe Systems, PostScript Language Program Design. See Blue Book, Red Book. 2. A standard Smalltalk reference Smalltalk-80: Bits of History, Words of Advice by Glen Krasner. See Kay, Alan. 3. A Compact Disc interactive (CD-I) standard that followed from the original Red and Yellow Book CD standards. Green Book standards, created by Sony and Philips, describe a hardware system and data recording format for multimedia disc recording that is suitable for entertainment programs. Green Code printer The first commercial typewheel style telegraphic printer embodying the start-stop synchronization concepts developed by Howard Krum. green gun In a color cathode-ray tube (CRT) using a red-green-blue (RGB) system, the green gun is an electron gun specifically aimed to excite the green phosphors on the coated inside surface of the front of the tube. Sometimes a shadow mask is used to increase the precision of this process, so the red and blue phosphors are not affected, resulting in a crisper color image. See shadow mask. green machine A physically robust computerized device or system designed and built to military specifications for field work. Green Paper The popular name for a paper titled A Proposal to Improve the Technical Management of Internet Names and Addresses which was issued for comment by the U.S. Department of Commerce’s National Telecommunications and Information Administration (NTIA) in 1998. See White Paper. Green’s theorem See Stoke’s theorem. green-gain control In a color cathode-ray tube (CRT), as in a television or computer monitor, a matrix resistor that can be varied to control the intensity of the green signal. Greene, Harold H. (ca. 1924-2000) A German-born American Judge, Greene was a lawyer and prominent, highly-respected member of the U.S. federal judicial system. He served the U.S. in military intelligence roles in World War II. In terms of telecommunications judgments, Greene is best known for the Modified Final Judgment (MFJ) and long divestiture proceedings leading to the breakup of AT&T in the

1980s. Judge Greene has also made important court decisions on Western Electric Company, Inc. (1991). See Modified Final Judgment. Greenwich Civil Time GCT. See Coordinated Universal Time. Greenwich Mean Time GMT. A time and geographic reference established by an agreement of 25 countries in 1884. Using astronomical instruments, a local time was established at the Greenwich Meridian in England, after which the world’s regions referenced their time in relation to GMT. It is also known as Zulu time. GMT is normally expressed in 24-hour clock notation. The international standard for time for satellite communications and scientific research has since become Coordinated Universal Time, which is based on atomic rather than astronomical clocks. See atomic clock, Coordinated Universal Time. Gregorian calendar See Julian calendar for the evolution of the Julian and Gregorian calendars. grep generalized regular expression parser. A very powerful, very useful Unix pattern matching, parsing utility (it takes a whole book to describe its many operating modes and uses) which allows selective search and display of computer data. At its simplest level, grep can help you search for instances of your best friend’s name in a directory full of old email messages; at its most sophisticated, it can parse and display complex patterns of instances of information. Grep increases in versatility when used with other commands through a pipe. Egrep (full expressions) and fgrep (fixed strings) are variations of grep. This very simple example of a grep search of an RTF file for the string “CRT” shows grep at its most basic level. abiogen@frodo: /1.2GB/users/abiogen/RTF $ grep CRT DictG.rtf \pard\tx20\tx3320\fc0\cf0 CRT \pard\tx20\tx7560\fc0\cf0 (CRTs) \b0 In a color cathode-ray tube (CRT), as in a television screen, a matrix resistor which can be varied to control the intensity of the green signal. \b0 In a color cathode-ray tube (CRT), using a red-green-blue (RGB) system, the electron gun which is specifically aimed to excite the green phosphors on the inside coated surface of the front of the tube. Sometimes a shadow mask is used to increase the precision of this process, so the red and blue phosphors are not affected, resulting in a crisper color image. See shadow mask.

grid A filtering structure, often used in vacuum tubes, that has the appearance of a grid or small set of blinds, and controls the flow of electrons from a cathode to an anode. Since this structure allows the flow of electrons to be manipulated, it may be called a control grid. A large part of electronics involves the harnessing of electrons through cathode rays, and grids are an essential control component in many devices.

GRID See Global Resource Information Database. grid, reference A visual guide used in the background of drawing, painting, layout, and CAD programs to help align visual elements and objects. Sometimes a SNAP function will be available in conjunction with the grid, in which the objects will SNAP to designated positions on the grid, to align objects with mathematical precision that cannot be obtained visually. grid battery Within electron tubes, there is usually an electron flow element called a grid, which selectively controls the movement of electrons from the cathode to the anode. A grid battery supplies a bias voltage to the grid in the electron tube for this purpose. See electron tube, grid bias. grid bias In an electron tube, a constant potential applied between the controlling grid and the anode to which the electrons are attracted. The grid bias, or C bias, is used to establish an operating point. A small cell may be used to supply voltage so the grid has a greater negative charge than other elements. See electron tube, grid battery. grid cap At the top of some electron tubes there is a small cap that attaches to the controlling grid to act as a terminal. Sometimes a spring clip is incorporated into the grid cap to create the electrical connection. grid modulation In a grid-controlled electron tube with a carrier signal, a voltage can be applied to modulate that signal in order to add information to the signal, as in a radio transmitter. See modulation. grinder Before the development of electric motors, a term for the people who turned cranks to operate mechanical equipment, including a variety of telecommunications devices. gritch Complaint, gripe. grok To understand, to get the essential idea of, to comprehend in a moment of insight. grommet A ring-shaped insulator, usually made of plastic or rubber, used as a spacer inside air insulated cables or in panels which require wires to be strung through them, so the inserted wire doesn’t touch the materials on the outside edge of the grommet. groove An indentation in a recording medium, often cylindrical or platter-shaped, that has minute variations which encode information. By creating both horizontal and vertical variations, it is possible to encode two tracks of information, as in a stereo vinyl record. Optical media usually store information in pits rather than grooves. See phonograph. ground 1. The surface of the Earth. A large conducting body, such as the Earth, that provides a destination for electrical current. 2. A conductor that makes a connection with the Earth, through which power can drain. v. To put in or place in contact with a ground, such as the Earth or a conductor in contact with a ground. To make an electrical connection with a ground. To provide a path through which an electrical current will drain to the ground, such as a lightning rod on a house. A ground is usually established as a safety precaution to direct unwanted or unanticipated electrical charges away from areas where it might cause harm to structures or beings. On an

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ocean-going vessel, where the ground connection cannot be placed into the Earth or onto a structure connected with the Earth, a device can be grounded on the bed plate of an engine. 3. A voltage reference point in an electrical circuit. Although it may not actually be touching the ground, it is a reference point whose operation would not be changed if it were grounded to the Earth.

A long conducting spike, pushed deep into damp soil makes a good ground for antennas. In the early days of telephones and telegraphs, grounding spikes were often driven into the moist ground near outhouses.

ground absorption A loss of transmission energy due to dissipation through the ground. Bounced airwave transmissions are particularly susceptible to ground absorption. Ground absorption may also be greater in regions of soft, uneven terrain. ground button A button found on some electrical components and power strips to reset components that require a ground start after a power failure. See ground start. ground clamp A device to connect a grounding conductor to a grounded object. Water pipes are commonly used as grounding objects, as are long metal spikes (often used near phone installations). At the turn of the century, when grounding pipes were not readily available, it was common for a telephone service ground wire to be pushed into the Earth in the damp ground in the vicinity of an outhouse. ground junction In semiconductor fabrication, a ground junction can be formed by growing a crystal from a melt. See semiconductor. ground lead A ground to which other conductors are attached so the ground lead can direct unwanted electrical current to the ground (usually the Earth). Heavy metal spikes are sometimes used as ground leads under external phone connection boxes. ground noise Residual, usually low level, noise associated with a communications transmission in which no actual information is being transmitted, but which has low-level hisses or hums associated with the transmission devices or media. This type of noise also occurs in many analog audio recording technologies.

ground potential A reference potential associated with the Earth at a particular location. The ground potential at that position is considered the zero potential, and other potentials are referenced against it as a baseline. ground return 1. A lead to the ground at the end of the circuit, for the return of a signal. 2. A type of circuit employing the ground as a return to complete the loop. The characteristics of ground circuits were discovered somewhat by accident by early experimenters, particularly when long telegraph cables began to be strung. It was discovered that it was possible to send signals along a single wire, as long as each end of the connection had contact with the ground, so the completion of the circuit happened through the ground rather than through a returning (second) wire. ground scatter propagation A means of propagating radio waves through a series of hops between the Earth and the ionosphere, rather than following a great circle path. When the signal returns from the ionosphere to the Earth, contact with the terrain scatters it broadly in many directions. See ground wave, ionospheric wave. ground start In telephony, it is necessary to take control of a line before it can be used. There are two common ways in which to do this, with a ground start or a loop start. The ground start is the type commonly found in business and other multiple line phones. When you pick up a phone, the plunger is released (off-hook) and the station detects a grounded circuit through the ring conductor. This is done so that transfer can be directed to the central office or main switching panel, if desired. See loop start. ground state A reference descriptor, used to describe the lowest state or energy level of a system, as an atomic system. ground station An Earth-based station (although the station may actually be located off the ground in a ground-based tower) used for sending, receiving, processing, or relaying communications signals. The term ground station is typically used to describe services that are partly air-based or space-based, such as satellite communications systems. Traditional broadcasting stations are not usually called ground stations because they bounce signals from ground to ground or from ground to ionosphere to ground, without passing through a space transponder, relay, or other sky-based node. Ground stations may be primary senders/receivers or ground hubs, which relay information or strengthen signals, as in M hop systems. See M hop, satellite. ground wave A transmitted radio wave that stays close to the ground. Radio waves travel in various directions from the point of transmission, some moving out through the ionosphere, others toward the ground. Ground waves are affected by the surface composition and topography of the surface over which they travel. Very rough or heavily vegetated terrain will interfere with the transmission of ground waves, while smoother surfaces, such as plains or calm waters, may permit transmission for hundreds of miles. See ionospheric wave, radio.

grounding strap A bracelet-like material or component usually worn on the wrist, and common in the electronics assembly and repair industries. The grounding strap prevents discharge from the hands that might damage static-sensitive components. If you must touch electronic components (as when plugging new memory inside a computer), use a grounding strap or, at the very least, touch a ground such as the power supply, and then install the chips or boards without moving too much or shuffling your feet in the carpet. See ground.

Electronics technicians routinely wear grounding straps when working with components. Single-use grounding straps are sometimes included with electronics products that are installed by consumers. This disposable 3M wrist strap was shipped with a computer circuitry upgrade product.

Group 1 to 4 See facsimile formats. group address A single address that is a logical name for a list of addresses. It may refer to multiple mailing lists, multiple devices, multiple users, or multiple receivers. A group address is used for management simplicity to provide a single reference point for a group of information. Group Asynchronous Browsing GAB. A means to improve and evolve information search and retrieval data mining on the Internet through the World Wide Web and existing community-based browsing by groups and individual Web users. GAB was introduced by Wittenburg, Das, Hill, and Stead of Bellcore in the late 1990s. GAB includes a resource discovery utility called WebWatch, that draws the users’ attention to changes in known documents. group busy tone In telephone trunks, sometimes the system is at capacity and cannot route any additional calls until volume decreases. In this case, a group busy tone (a fast busy) may be sent out to those attempting to place a call. See fast busy. group hunting In telephony, the process of searching for available lines in a designated group of trunks. See hunting. group modulation The process of shifting or collectively modulating a set of signals that have already been individually modulated or multiplexed. It is often done to achieve a block frequency shift.

Such frequency shifts may be done to bring a signal into a range that can be handled by the equipment or may reduce interference between incoming and outgoing signals in a repeater or relay circuit. groupware Software that runs on a network, so a number of designated users or all users on the system may use it, either simultaneously or up to a certain number of licensed users at a time. There are two types of groupware: (1) software that is accessible and usable by the group, but the data generated by the software is specific and local to the user; and (2) software accessible and usable by the group in a type of conference atmosphere, in which the changes made in the software, and perhaps even being viewed by the user, will be seen by other members of the group as soon as the data is updated. Whiteboarding is a type of groupware application. Groupware is popular in corporate cooperative work environments. Grout, Jr., Jonathan An inventor and entrepreneur who established one of the first marine reporting telegraphs in North America, which extended from Martha’s Vineyard to Boston. It was an optical telegraph, a type that had been used in France and other European nations but, up to this time, was not definitely established in North America. The U.S. patent office recorded a patent issued to Grout in October 1800. Unfortunately, the original patent document was apparently lost in a fire in 1836. The service established by Grout, presumably based on the patented system, operated during the early 1800s but went into bankruptcy by 1807. The old signal station still remains. Grove battery A historic, dependable zinc/sulphuric acid and platinum/nitric acid primary cell normally used on closed circuits. The Grove battery provided 1.96 volts per cell. This type of battery was used by Morse in his early telegraph systems. growler An electromagnetic circuit diagnostic and magnetizing/demagnetizing tool that emits a low growling sound when a short circuit is detected. GRSU 1. Generic Remote Switch Unit. 2. Geographic Remote-Sensing Unit. grunt colloq. A telephone pole and line installation crew member who works on the ground (as opposed to one who climbs the poles). Grunts are also commonly called groundmen or groundworkers. GS trunk ground start trunk. See ground start, loop start. GSA 1. General Services Administration. 2. See Global Standards Collaboration. GSFC Goddard Space Flight Center. GSM See Global System for Mobile Communications. GSMP See General Switch Management Protocol. GSN Gigabyte System Network. See Hippi-6400. GSO geosynchronous orbit. See geostationary orbit. GSOC See German Space Operations Center. GSSAP See Generic Security Service Application. GSTN general switched telephone network. A public switched telephone network (PSTN).

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GTE Corporation Formerly General Telephone and Electronics Corporation, GTE is a major international telecommunications provider that originally supplied basic local telephone services but now includes long-distance, wireless, airline services, online directories, Web, and video services. It is building a national private coast-to-coast data network in the U.S. and wireless paging systems overseas. In 1997, GTE acquired BBN Corporation, an end-toend Internet provider, and Genuity, Inc. to broaden its base of new telecommunications technologies. GTN See Global Transaction Network. GTP 1. general telemetry processor. 2. See Generalized Trunk Protocol. 3. Geophysical Turbulence Program. A scientific research program established through NCAR in the early 1960s. 4. Global Thinking Project. A Web-based educational environmental science project. http://www.gtp.org/ 5. GNOME Translation Project. A primarily volunteer effort to translate GNOME software applications and documentation to every known language. See GNOME. 6. Green Transport Plans. An employee travel plan service of the U.K. Department for Transport, Local Government, and the Regions. GTT See Global Title Translation. guard arm 1. A crossbar placed over wires, running in the same direction as the wires, to prevent contact with debris, people, animals, or other wires. 2. A wood or metal extension to prevent or selectively permit access (e.g., into a restricted facility). Horizontal guard arms commonly pivot to a vertical position to permit access and may be triggered by motion sensors or signals from automated password or key card systems. guard band 1. A narrow broadcast bandwidth safe region interposed between communications channels in order to minimize interference between adjacent channels. Guard bands are particularly prevalent in frequency multiplexed systems, where maximum use of available bandwidth is achieved by dividing the available frequencies into smaller channels. 2. A safety zone in a circuit or chip, around the active portions of the circuit, to prevent electromagnetic interference with adjacent circuitry. guard circle The smooth, ungrooved, inner portion of a phonograph record, or other revolving storage medium, protecting the stylus from moving into the center post and being damaged. guard wire A wire near live wires, such as on utility poles, positioned so that if the live conducting wires break or fall, they will come in contact with the guard wire and be grounded, rather than causing danger. guardian agent A pun on guardian angel in the sense that it is a software tool intended to protect innocent eyes from sites that some person in authority over the user deems unsuitable. With the vast and varied information on the Internet easily accessible through the World Wide Web, some parents and teachers are concerned about the type of Web browsing children might attempt. Software developers have responded to this concern by developing tools to lock out specific known sites or to flag sites with particular

characteristics. There is no completely reliable way to screen out all such sites on the Web, especially since there is no consensus on what people consider objectionable. A child could quite innocently search for the word ‘beaver’ for a biology project. The resulting hit list wouldn’t be restricted to Canada’s national animal; it would also list every slang sense of the term found on commercial sites, home pages, poetry pages, sex sites, and more. There is a trade-off between a user being able to access search engines and the potential harm from stumbling over an unintended site. While North American society has become more liberal in recent years, there are sites that are simply not suitable for children (and not of interest to discerning adults) that may be screened out by guardian angel agent programs. A new source of problems not yet fully addressed by guardian agent programs is junk email (spam). Irresponsible vendors are distributing massive quantities of email selling black market pharmaceuticals, drugs, and DVDs at tempting prices, as well as distributing extremely explicit photos that are obscene by almost any standards. With current Web browsers and graphical email clients, pornographic images automatically pop up in the email reading program without the reader having to click any links in the message. Thus, large colored photographs of bestiality, underage girls engaged in sex with adults, or images of women naked in change rooms (who didn’t know they were being photographed by hidden cameras) are designed to pop up instantly on the screen in the email client window or a separate window, before the reader has a chance to assess the message and delete it. These images can be seen by anyone in the same room with the computer. Children and many teens do not possess the emotional maturity to deal with this type of information and some children are frightened by it. There is no guarantee that there will be an adult in the room to explain the images or allay their fears. Many school-aged children have email addresses listed on personal Web pages or school Web pages which make them automatic targets for undiscriminating junk email robots. Email filters and guardian agent programs do not always screen these messages because the senders are careful to avoid using words or subject lines that are commonly filtered. While concern focuses on ways of locking out particular types of sites and figuring out ways to stem the flow of obscene or illegal email, another serious danger on the Net is somewhat overlooked. Innocent adults and children will sometimes mistake the personality of a person on the Web as being the “real” person. This is understandable, but naive. It is easier to misrepresent oneself or to cover up hostile or dangerous intentions on the Net than in person. This type of danger is more difficult to detect with a software agent than obscene or tasteless Web sites. Global communications are here to stay, and it will be necessary to educate users of all ages to cautiously evaluate personal contacts developed through this new medium. It’s a new world, and mature and practical strategies have to be developed to enable positive

relationships online and to avoid ones that may be emotionally or physically harmful. guarding 1. The incorporation of points in a circuit where excess current or leakage are drawn off. 2. The process of maintaining a circuit in its busy state for an interval after it has been released, in order to assure a minimum period of time elapses before the actual disconnect occurs. Guericke, Otto von (1602-1686) A German engineer, inventor, and statesman, von Guericke is credited as the inventor of the air pump, in the mid-1600s. The pump design was later improved by experimenters such as R. Boyle and F. Hauksbee. Guericke also did experiments to study the rotation of the Earth that he described in 1672 in Experimenta nova Magdeburgia de vacuo spatio. In the course of his research, he created a spinning model to simulate the Earth. Because Guericke noticed that a feather was alternately attracted to and repelled by the spinning globe, the model has been credited by some as the first frictional generator, though von Guericke did not specifically design it to create friction for electrical experiments. See Hauksbee, Francis. GUI See graphical user interface. guidance system A system that evaluates terrain, sensors, flight information, driving information, or other data pertinent to the object being guided and reacts accordingly. Guidance systems are used with many airborne objects and transport systems (missiles, radio-controlled models, aircraft, etc.) and underwater systems (torpedoes, submarines, diving robots). Some guidance systems incorporate means to hide the guidance control signals so a target doesn’t know the object is coming. A guidance system typically consists of one or more sensing devices (optical, radar, infrared, sonar), intelligent evaluation of the data from those sensing devices (human, computer, or both), and a controlling system that reacts with input from the information processed from the sensing devices. Dolphins, bats, and some insects have sonar systems that aid them in navigating through water and air, respectively. In dolphins, this perceptual system is so sophisticated that the mammal can actually see the shape of an object inside another object. In spacecraft, guidance systems are primarily used for trajectory and directional control during the firing of thrusters. Out in space, it’s not possible to use hills, trees, and other terrain markers as reference points. Instead, the positions of celestial objects, such as stars, suns, or planets, are used. See attitude and articulation control subsystem, chaff, frequency hopping, intelligent vehicle highway systems. guided wave An electromagnetic wave whose path is controlled or directed by a structure or process acting as a conduit, channel, or waveguide. Physical waveguides can be quite sophisticated and are mathematically related to the wavelength of the wave being guided. Reflected waves are a type of guided wave in the sense that the reflection may be carefully organized to channel the wave in the desired direction. For example, a parabolic receiving antenna

dish reflects transmission waves into a feedhorn mounted at a specific distance from the dish. See waveguide. guru Sage, wizard, admired expert. guru meditation error On the Amiga computer, a whimsical presentation of the error identification number that was displayed on early versions of the operating system if the system crashed. It was removed in versions 2.0x and up, and the OS itself was much less subject to crashes in the updated versions. gutta-percha A latex substance present in a number of Malayan evergreen trees, including the Palaquium oblongifolium. The trees are like high-resin rubber trees that can be girdled or felled to tap the milky substance inside. The substance is processed and molded for shipment. Gutta-percha came to the attention of Westerners in the 1840s through samples sent to London by Pacific region travelers. Gutta-percha was a tough, natural rubbery substance that came to be used extensively for insulation, general manufacture, a variety of adhesives, and even golf balls, until the late 1940s. For a while, almost any moldable rubber-like material was referred to as gutta-percha and many of these materials were used in the manufacture of bindings, frames, molded containers, and costume jewelry. Sometimes gutta-percha would be mixed with other substances to provide coloration and embossed with interesting patterns and pictures. When synthetic plastics became commercially widespread, the use of gutta-percha declined. However, dental guttapercha has had a useful life of more than 100 years, and it is still popular for root canal plugs and temporary fillings. Dental gutta-percha has recently been improved with the development of bacterially resistant formulas. Gutta-percha softens and stretches when warmed and hardens without becoming brittle when cooled. With the addition of stabilizers to protect it from oxidation, it can last longer in extreme environments than India rubber. This versatile material is historically important because it enabled the laying of communications cable in unfriendly environments, such as ground and deep sea installations. Gutta-percha was a significant factor in the success of the first transatlantic telegraph cable. See transatlantic cable. gutter In page design and layout, a columnar margin between two facing pages of a bound document. Technically, the blank space between columns on a single page is not a gutter; however, not all programmers know this, and some software will label this area as the gutter and will prompt the user for the width of the gutter. It would be nice if programmers and managers would solicit the input of professional specialists when applying terminology in computer programs. In the meantime, users of this dictionary will know the difference. guy wire A slender support line used to brace and steady an apparatus that might sway or fall. Guy wires are often used in multiples, spaced around whatever they are supporting, and are frequently used for narrow high structures such as transmission towers, aerials, masts, and poles. Guy wires are usually

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thin, to minimize wind resistance.Consequently, they sometimes have small telltales, fine pieces of cloth or plastic attached to the wire, to discourage birds from flying into them or people from tripping over them. Guy wires are useful in areas that are exposed to surf or high winds. guyed Supported by guy wires. Tall antennas and radio towers are often reinforced with guy wires to withstand high winds. See guy wire. GVNS global virtual network service (e.g., as in ISDN Q.85 community of interest services). gyrofrequency The frequency at which charged particles naturally rotate under the influence of the Earth’s magnetic field. The frequency varies with the type of particle. gyroscope, gyro A device designed to maintain its axle in a constant vector while rotating. A gyroscope is typically designed to rotate through two axes that

are perpendicular to the central structure and to each other. It is called a gyrocompass when it is oriented with the axle pointing northward. gzip GNU zip, a widely used file compression program developed by Jean-Loup Gailly that incorporates Lempel-Ziv coding algorithms with 32-bit CRC. Gzip is widely used on Unix systems and IBMcompatible disk operating systems, especially for compressing and decompressing files to save transmission times for phone line uploads and downloads. Gzip uses a deflate compression format derived from the freely distributable zlib source code distributed by Gailly and Mark Adler. Gzipped files may be unzipped by typing “gunzip [filename]” (the command must be typed all in lower case) at the command line, with relevant optional parameters. On a Unix system, see the man pages on gzip for more information on zipping, listing, and unzipping files. See compress, uuencode, zip, RFC 1952.

h 1. abbrev. hecto-. See hecto-. 2. abbrev. horizontal. 3. symb. horizontal linear polarization (ITU). H channel An ITU-T-defined transmission channel on packet-switched networks consisting of aggregated B channels (bearer channels), as are used on an ISDN system. See ISDN. H drive In analog video, a periodic signal related to the horizontal component of a frame that is constructed with sequential, repeating line scans. The relationship between horizontal sync and vertical sync is such that the pulses can be combined on a single wire. Together they comprise a composite video signal. The H drive sends a short horizontal sync pulse during the horizontal blanking interval when the beam moves from right to left without tracing a line on the screen. A composite signal can be represented as Csync-red-green-blue and transmitted over four wires. Many computer monitors use a five-wire RGBHV system in which the H and V represent horizontal and vertical sync pulse components. See negative-going video. HAARP High Frequency Active Auroral Research Program. A scientific research effort established in Arctic Alaska for studying the ionosphere, with an emphasis on using the results to better understand and enhance communications systems. A highpower, high-frequency, phased-array radio transmitter is used to stimulate a well-defined region of the ionosphere while an ultra-high frequency (UHF) incoherent scatter radar (ISR) is used to measure the effect in terms of densities and velocities. See grayline, ionosphere, planar antenna array. http://www.haarp.alaska.edu/haarp/ H0 Channel In ATM networking, a 384-Kbps channel consisting of six contiguous DS-0s (64 Kbps) of a T1 transmission line. hack v. 1. To quickly cobble together a program. 2. To create something quickly from available materials, a make-do solution, not necessarily elegant, although it could be, given limited resources. 3. To create a small, quick entertaining showpiece designed to illustrate a cool idea or interesting capability. See Schwabbie. 4. To seek to compromise or enter an area/process for which the person does not have authorization. hack into To find a means of entrance other than the

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normal way, to compromise the security of a system by exploiting a weakness or lesser-known characteristic, to deliberately break into a computer system, network, or computer process without authorization. hacker 1. A person who hacks into a system, i.e., gains entry by exploiting the hardware or software architecture through black boxes, stolen or guessed passwords, Trojan horses, design flaws, or back doors. Sometimes called cracker to signify someone using these techniques for illegal purposes such as cracking a password or serial number. See cracker. 2. A person who acquires a sophisticated, in-depth knowledge of a system and applies this knowledge to configuring or programming the system with a high level of expertise or complexity. An elite programmer, engineer, or technician. Two popular books on this subject are Hackers by Stephen Levy and The Cuckoo’s Egg by Clifford Stoll. Hacker’s Dictionary, The An electronic and print dictionary that evolved from The Jargon File in the early 1980s. The Hacker’s Dictionary was an expanded version of The Jargon File with added commentary, published by Harper and Row in 1983, edited by Guy Steele. The co-editors/contributors were Raphael Finkel, Don Woods, Mark Crispin, Richard M. Stallman, and Geoff Goodfellow. After nearly a decade in which it remained essentially unchanged, The Hacker’s Dictionary was expanded beyond the artificial intelligence (AI) and hacker cultures to include terms from a broad variety of computers. The 1990s version, called The New Hacker’s Dictionary, is maintained by Eric S. Raymond and Guy L. Steele Jr. See Jargon File, The. hairpin pickup coil A device with a one-turn coil, shaped like a hairpin, used for transferring ultra high frequency (UHF) energy. hairpinning The routing of information or data through a switch in a main facility or network host and sending it out again through another switch or routing device. HAL-9000 No computer-related dictionary would be complete without mention of the intelligent computer in the science fiction movie classic 2001: A Space Odyssey. HAL stood for “Heuristically Programming Algorithmic Computer” and apparently the one-letter shift that spells out “IBM” was not intentional,

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or so say the makers of the film. If not, it’s a strong enough coincidence to create an apocryphal legend. HALE See High Altitude Long Endurance. half duplex In a circuit, one-directional transmissions. Often half duplex circuits can transmit in either direction, but not simultaneously. Many systems which technically have bidirectional capabilities are operated in half duplex mode to reduce interference and echoes. Modems, satellite voice lines, some cellular radios, and speakerphones are often used in half duplex mode. half-life A property of radioactive decay used as a quantitative measure, of interest to many different branches of science. Radioactive decay happens at widely differing rates for different materials, so halflife is not a fixed measure, but one based on our knowledge of the properties of the materials being described. The first half-life of a substance is the interval during which half the radioactive material is left unchanged. The second half-life is the next interval, during which half of the remaining radioactive material is unchanged, and so on. These half life measurements are used by many scientists including astronomers, nuclear physicists, archaeologists, and geologists. half tap A bridge that is placed across conductors without disturbing the normal functioning of the conductors. half tap, network In data network communications, a duplicate path established between nodes or systems. A half tap provides redundancy where new cable is being run, as in circuits where fiber optic is replacing copper, but where it’s not desirable to disrupt the existing network until the new cabling is functional. half tap, telephone In telephone communications, a duplicate service installed on the subscriber side of the demarcation point (usually on the customer premises). This may be done in instances where there is a problem with the original circuits, or where a new system is being installed and the old one is left in place until the new one has been tested and is known to be functional. half wave antenna An antenna designed so that its electrical length is equal to half of the wavelength of the signal being received or transmitted. halftone A printing technique developed in the late 1800s that takes advantage of human spatial integration to simulate tonal gradations with an ordered series of dots of various sizes and sometimes various shapes. When fine details are seen by humans at a distance, the eye-brain averages and integrates the image so that it appears as levels of gray, even though the dots are of the same color and intensity (usually black against a light surface). Halftone images are commonly used in many types of printing jobs including newspapers and magazines. Observed closely with a magnifying glass, the dots can be seen. Desktop publishing software typically has settings to control halftone resolutions and screen angles. Newspapers are usually printed with 60 to 85 line screens, magazines at 85 to 150, and art prints at 150

to 200. The first newspaper halftone was printed in 1869 in The Canadian Illustrated News by Canadian publisher G. E. Desbarats. Hall constant A description of the relationship between current-carrying conductors and magnetic fields. The Hall constant = (transverse electric field) / (magnetic field strength) x (current density). Hall effect If you take a current-carrying semiconductor with a magnetic field perpendicular to the direction of the semiconductor’s current, a voltage is created that lies perpendicular to both the current and the magnetic field of flux. It has practical applications in generators and modulators. Hallwachs, Wilhelm (1859-1922) A German physicist who developed a type of refractometer and who confirmed some of the pioneer photoelectric work of Heinrich Hertz. In 1888, Hallwach described his discovery of the photoemissive properties of certain substances when exposed to light by using an electroscope. He demonstrated that photoelectric cells could be used in cameras, a big boost to the evolution of television, which was just being developed at that time. Hallwachs effect In a vacuum, a negatively charged body discharges when exposed to ultraviolet light. The effect is named after Wilhelm Hallwach. ham operator colloq. Amateur radio operator. A hobbyist radio operator engaging in noncommercial radio communications. Ham operators are primarily involved in personal, public service, and training communications over approved radio frequencies. Hams have also had a long history of voluntarily aiding in search and rescue, emergency, and disaster relief communications to augment government or commercial communications or in situations where no other support is provided. The frequencies in use for amateur communications are fairly standardized throughout the globe and hams have long communicated across international borders. In the U.S., ham communications and the issuance of ham radio licenses are administrated by the Federal Communications Commission (FCC). Ham operators come in all ages, shapes, sizes, and colors and represent a wide spectrum of abilities, professions, and technical expertise. See American Relay Radio League. ham-in-space program A cooperative technical, educational, communications effort of amateur radio operators worldwide. See AMSAT, Mir, OSCAR. Hamming code A linear error detection/correction code system named after R. W. Hamming of Bell Laboratories. It can detect single- and double-bit errors in data transmissions and correct single-bit errors. Hamming codes lend themselves to matrix representation. See error correction. Hammond, Fred (1912-1999) A Canadian engineer, collector, and curator, Hammond was a co-builder of Hammond Manufacturing Company, in 1927, one of the largest historic electrical/electronic equipment manufacturers in Canada. The company started as Oliver S. Hammond’s (Hammond’s father) basement shop during World War I and evolved into O.S. Hammond & Son, including Fred Hammond and his

brothers. In 1986, Hammond Manufacturing became a public company, trading on the Toronto Stock Exchange (TSE). Hammond began building radios in the early 1920s and earned his first amateur radio license in 1929. He founded the Southern Ontario Chapter of the Quarter Century Wireless Association and helped build it into the largest local chapter. He was honored by the Canadian Amateur Radio Hall of Fame in 1996 and has received many other awards of appreciation and recognition over the years. Hammond will probably be best remembered for founding the Hammond Museum of Radio, a center that demonstrates and shares his love for radio technology for future generations. Hammond held amateur radio license VE3HC, inherited from his father. See Hammond Museum of Radio. Hammond, Jr., John Hays (1888-1965) An American engineer and inventor who developed radio control (RC) systems for vessels in the 1910s. As a schoolboy, Hammond was already experimenting with circuits and sensors. His social circle included many of the great inventors of the time, including Thomas Edison and Nikola Tesla, a fact that likely provided inspiration and encouragement for his talents. While at University, he met Alexander Graham Bell and studied radiodynamics and emerging telephony technologies. Starting as a patent clerk, Hammond familiarized himself with the patent process and, in a few years, amassed more than 100 patents. He studied many aspects of radio technology, including frequency modulation (FM), radio tuning, telephony, guidance systems, and much more. Many of his patents were later purchased by the U.S. military for use in radio-controlled guidance systems. See frequency hopping. Hammond Museum of Radio Named after its originator, Fred Hammond, the museum began as a personal collection in the early days of radio and grew steadily to the point where it was moved to a new, larger facility at the Hammond Manufacturing Company’s South Transformer Plant in Guelph, Ontario, Canada, in September 1999. The collection includes hundreds of historic radio receivers and transmitters and represents many of the important developments in wireless technology. Many of the systems are still in working order or have been restored to working order. Of special interest is the Collins Collection, likely the largest operational exhibit of Collins Radio equipment in the world. The museum also hosts special exhibits to commemorate the discoveries and designs of a variety of radio pioneers. http://www.hammondmuseumofradio.org/ HAN See home area network. See fiber to the home, home ATM network. hand off See handoff. handle A pseudonym, a nickname, often very creative, humorous, or obscure. A handle indicates your personality, your interests, or helps preserve anonymity. Handles are frequently used on the Internet in various email messages or postings to public news forums or chat groups. handoff, handover 1. The process of passing on a

message or transmission to the next leg in a route that takes more than one type of communications medium or more than one transmitting region. A make-before-break handover is one in which the transfer to the new leg is carried out in such a way that the user does not perceive a break in communications. 2. The process of a communication being passed through various ‘hands,’ usually because the user is mobile, as from one zone to another, one station to another, one transmitter to another, or one frequency to another. 3. In cellular communications, the transfer of the call from one cell to the next as the subscriber moves through the various cells. Handoffs often involve frequency shifts. 4. The process of passing a caller to another agent, as from a receptionist to a sales representative or technical support person. Hansen, William Webster (1909-1949) An American physicist and educator with a pioneering interest in the use of high-frequency radio waves (microwaves) in particle acceleration research. Hansen joined the staff at Stanford University in 1934. He was an associate of Martin Packard, working on a team with renowned physicist Felix Bloch. In the 1930s, Hansen began his association with Russell and Sigurd Varian, working in the basement of the Stanford physics building. When the inventive Russell Varian sketched out an idea for a Rumbatron Oscillator or Amplifier, in July 1937, it was Hansen who had provided the basic rumbatron concept and the calculations to support the viability of Varian’s idea, leading to the invention of the Klystron tube. Hansen subsequently did important work in microwave theory and passed on the knowledge through courses at Stanford while the Varians developed practical applications of the Klystron technology for radar and communications. Following World War II, Hansen returned to his research interests and pioneer work in disk-loaded accelerators. He demonstrated a linear accelerator in 1947, sponsored by the Office of Naval Research. It led to the later creation of the Stanford Linear Accelerator Center (SLAC) and many discoveries in basic particle physics and X-ray spectroscopy. The basement lab had evolved into the Microwave Laboratory, which eventually became the Ginzton Laboratory and the Hansen Experimental Physics Laboratory. See Ginzton, Edward; Klystron; Mark accelerators. handset A human interface communications transceiver unit, most often associated with telephones. It’s the part we pick up and hold to our ears and mouths in order to listen and speak on the phone. Handsets come in a variety of shapes, some of which have names in the telephone industry. The older round handsets familiar on rotary phones are G style, whereas the newer square ones more common on mobile phones and phones with the buttons on the handset are K style handsets. handsfree A communications unit that does not require the user to hold it in order to be able to communicate with the caller. Headsets and speakerphones are examples of handsfree units in the

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telephone industry. Some phone systems permit handsfree menu selection or dialing through voice recognition. Car-mounted cell phones are becoming more prevalent, so the driver can have both hands on the wheel and concentrate on driving, rather than holding the cellular handset. For computer input devices, a voice recognition system can be used along with a headset to create a handsfree unit. handsfree telephone Any telephone appliance that provides handsfree operation for some or most of its operations, such as a voice operated phone or computer (e.g., for spoken dialing), a speakerphone, a headset, etc. See handsfree. handshake Communication between two systems to manage synchronization of the transmitted and received signals, often established with ACK or NACK signals, with tones, keywords, or header packets. Handshaking is an essential component of most communications systems and is often incorporated into the transmission protocol itself. Handshaking can be done between people, between machines, or both. The most familiar form of handshake is the verbal “Roger” that allows the other person on a line to know that you’ve finished talking and she or he can go on. On public chats on the Internet, where dialogs are typed rather than spoken, “GA” (Go Ahead) serves the same purpose. In verbal communications, this “Roger” handshake is sometimes accompanied by electrical signals that set the half-duplex communications direction to favor the person who is currently talking. In modem communications, handshakes are used to acknowledge a signal, to coordinate baud rates, and to orchestrate the transmission, receipt, and data, so the signals don’t override or clobber one another. handshaking See handshake. handwriting recognition A software application, often coupled with a scanning device or a stylus that resembles a pen, that interprets written script or translates it into computer-readable text. Pen computing uses this type of technology and is of use to those who don’t know how to type or don’t want to. Since handwriting is widely variable, most systems need to be trained to recognize an individual’s writing and, even then, the results may not be perfect. Nevertheless, in the shipping industry, scientific field work, and other areas, handwriting recognition is useful, and the technology will eventually improve to the point where anyone’s handwriting can be recognized and interpreted by a computer. See Personal Digital Assistant. hang up v. To disconnect from a transmission (two words when it is a verb). On modems, ATH is the Hayes-compatible command for hanging up. On phones, a hangup (one word when it is a noun) occurs when the button is pressed for at least a specific amount of time. In some areas, the callee may not be able to hang up this way if the caller is still on the line. It doesn’t work the other way though; if the caller hangs up and the callee is still on the line, the transmission is disconnected. Many Internet Service Providers (ISPs) will automatically hang up (terminate) a computer connection if there is no activity

after a certain amount of time, such as 10 minutes. hard copy An image or document that is readable by looking directly at the medium on which it is transcribed, as on a piece of paper, cardboard, stone, or parchment. A soft copy must be accessed with some type of technology in order to be viewed, manipulated, or displayed. Soft copies commonly exist on hard drives, floppy diskettes, tapes, CDs, and other magnetic or optical media. hard disk drive, fixed disk drive HDD. A data storage device most often associated with digital computing systems although it is also useful for storage in computerized milling machines and other industrial automation products. In the early days of computing, program code and data were stored on paper tapes, punch cards, and magnetic tape spools and cassettes. All of these early devices, as they were implemented at the time, were essentially linear/serial devices with limitations in the speed and flexibility of data access and storage. In the 1950s, IBM engineers claimed leadership in data storage with the invention of a high-speed random-access device. The release of the 305 Random Access Method of Accounting and Control (RAMAC), in 1956, made it possible to store five megabytes on 50 24-inch discs. The machine weighed more than a ton. In the early 1970s, sealed disks known as Winchester disks were introduced and the name became generic for disk drives for several years. Floppy disk drives were an inexpensive alternative to the new, expensive hard disk drives sold during the 1970s and the 1980s, but by the late1980s, hard disk drives became the dominant storage medium and floppy drives were used mainly for program distribution and swapping small files among computer systems. In 1986, the American Society of Mechanical Engineers declared IBM’s contribution as an International Historic Mechanical Engineering Landmark. The following year redundant arrays of independent disks (RAID) technology was patented. The hard drive as we know it is based on a rotating circular platter with a read/write head that never travels very far from any specific location on the platter, thus providing not only random access, but also highspeed access, compared to previous methods. One or more magnetic platters are permanently contained within a fixed housing (as opposed to cartridges or other portable storage devices), hence the name hard or fixed disk. When a drive is formatted, the magnetic particles are aligned to a specific pattern and, from that point, data is written by influencing the particles and read by detecting the state of the particles on the magnetic surface. Compared to floppy diskettes, the hard drive can hold far more information and is safe from dust and fingerprints. IBM’s claim that hard drives would revolutionize computer storage was correct, as hard drives quickly superseded tape drives for most realtime applications. (Tape was retained for backup purposes due to its lower cost and was later reintroduced as a randomaccess removable medium, popular in the 1990s.) Hard drives were originally expensive washing machine-sized devices purchased by institutions for

mainframe computers, but by the early 1980s, hard drives were smaller and more accessible and available for the desktop market as well. A five megabyte hard drive in a breadbox-sized housing could be purchased for under $1,000 and soon smaller, higherstorage drives were available for a few hundred dollars. By the early 1990s, it was possible to buy booksized hard drives with a gigabyte of storage for under $1,000 and, with improvements in technology and new formats, two-gigabyte drives were less than $200 by the year 2000. Another consequence of smaller drives was portability. By the early 1990s it was possible to equip portable computers with highcapacity drives and removable hard drives were built into some models. Hard drives have been developed in a number of formats, too numerous to list here. However, the most common hard drive controller/hard drive formats used on desktop systems during the 1980s and 1990s were 1. Small Computer System Interface (SCSI) – a robust format that could be daisy-chained (usually up to seven devices) to include several drives or could be used in RAID systems. SCSI was installed in most Motorola-based machines including Macintosh, Amiga, and many workstation computers. 2. Integrated Drive Electronics (IDE) – a more limited master/slave format introduced to bring the price down on drives for popular Intel-based machines serving price-conscious consumer markets. These drives became prevalent on IBM/ IBM-licensed computers sold to homes and small businesses in the 1990s. Due to limitations in capacity and expandability, a new enhanced IDE format was introduced as EIDE. EIDE was essentially a move to give IDE the capabilities familiar to SCSI users. Improvements in hard drive capacity have been strongly tied to the ability of the read/write head to read and write data of finer precision and higher densities. Thin films were introduced in the late 1970s, along with the run-length-limited (RLL) data-encoding scheme. In the early 1990s, IBM introduced magnetoresistive head technologies based on discoveries in the late 1980s of high magnetic field effects on crystals. With more sensitive sensors came highercapacity hard drives, with significant breakthroughs resulting from the development of giant magnetoresistive (GMR) head technologies. SCSI and IDE had a relatively long reign, considering the pace of computer technology, but Universal Serial Bus (USB) drives were making inroads by 2001. The USB data transmission standard was developed by a consortium of companies (Compaq, DEC, IBM, Intel, Microsoft, NEC, Northern Telecom) in the mid-1990s. USB hard drives have several advantages over previous formats, including small size, hot-swapping capability, portability, and high capacity, all at a reasonable price. FireWire is another format gaining popularity. FireWire was developed by Apple Computer and the IEEE 1394 Working Group. Its principal advantage is speed,

which makes it suitable for hard drive and other demanding transmission technologies (e.g., video). Given their many benefits, USB and FireWire may quickly supersede both IDE and SCSI formats on consumer machines, although updated SCSI formats, including Ultra SCSI and Wide Ultra SCSI may continue to serve workstation and service provider environments where very high transmission speeds are desired. See disk controller, redundant array of inexpensive disks, superparamagnetic. hard sectored A storage medium, usually magnetic, in which the various boundaries or sectors are physically designated with holes, pits, ridges, or other markers to indicate their extents. Hard sectored media are becoming less common than soft sectored as they are less transportable between different systems. hard transfer A term for an electronic monetary transaction involving the actual exchange of funds between individuals or banking institutions. A hard transfer often follows a soft transfer. A paper check is a type of soft transfer. It is a monetary transaction that is not actually finalized until the money is withdrawn from the bank. Similarly, online there are many monetary transactions that are soft transferred and later hard transferred from the actual bank or other financial institution. hard tube A type of electron tube that has a high vacuum environment within the sealed glass bulb. hard wired See hardwired. hardware The physical circuits and devices associated with systems, especially computerized systems, that are fixed or hard wired and unlikely to be altered by the user. Contrast with software (although the distinction is not actually cut and dry), which is selected and swapped out by the user, modified, or overwritten. See firmware, software. hardware flow control A capability built into most of the high speed serial card modem combinations that helps to handle data flow control. Use of hardware flow control may also require the use of a hardware flow control cable. hardware interrupt On computing systems, a call to the software to interrupt the current process in order that it may temporarily listen to or interact with a hardware device interfaced with the system. See interrupt, IRQ. hardwired 1. A circuit that is intended as permanent or is not expected to change in the near future, and thus it is wired in such a way as to make it efficient to produce or easy to use, rather than making it amenable to change. Contrast this arrangement to patch bays and breadboards, which are intended to prototype temporary circuits and are easy to change. Programs or pathways built into computer motherboards are typically hardwired, whereas the various useradded peripherals, especially those that fit into slots or chips designed to be swapped out when better technology is developed, are considered to be modular or configurable and not hardwired. 2. People who are hardwired are said to be set in their ways, not amenable to change or open to new ideas. 3. An idea or system that is hardwired is one that is entrenched,

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difficult to change for various reasons, including politics, economics, or complexity. Harmon, Leon D. A Bell Telephone Laboratories researcher who initiated a project to simulate the functions of biological nerve cells by means of simple transistors. These could be closely associated with one another in arrays and were applied in a simulation of mammalian eye nerves. His work was featured in industry journals in the late 1950s and in the film Thinking Machines in 1960. Harmon chaired workshops sponsored by the National Science Foundation (NSF) in the mid-1970s. Harmon was a pioneer cyberneticist interested in machine simulation of aspects of human perception. Long before most others, Harmon could see the practical applications of recognition technologies. In this vein, he coauthored a number of articles on character recognition, human face recognition, and automation of these processes by intelligent systems in the early 1970s. He also collaborated in a number of projects with Ken Knowlton, and together they did experiments in scanning images and reconstituting them with computer algorithms, thus creating some of the first examples of computer graphics and image processing as they relate to human perception. See Knowlton, Kenneth; neural network; Shroeder, Manfred R. harness A securing system of straps, combination connectors, or other means used to consolidate multiple cables so they can be handled more easily as a unit. Harris Broadcast Communications, Harris Corporation An international, publicly-traded commercial provider of advanced broadcast technologies, Harris is one of the pioneer developers and providers of digital broadcast technologies. It contributed the radio frequency Test Bed for the Advanced Television Test Center in 1990, was first to market with a number of digital television exciter and transmissions products, the first to transmit a commercial HDTV signal, and the first to establish an operating digital television air-chain. Harris also broadcast the first major live high-definition television (HDTV) sports event in 1997. In 1999, Harris and the CPB/ WGBH National Center for Accessible Media demonstrated digital closed caption and descriptive narration technologies at the National Association of Broadcasters conference. In April 2001, Harris announced a business arrangement with Dotcast, Inc., to provide digital content through a revolutionary network that takes advantage of advances in broadcast technology. It provides popular computer services available on the Internet, through new digital broadcast technologies in a oneto-many relationship rather than a one-to-one relationship as is typical of Web browsers. Harris Corporation is also a provider of computer security products, distributing network analyzing and scanning software to clients such as the Canadian Public Works and Government Services. Harris has contributed to the development of the European Digital Video Broadcast (DVB) standard. See Advanced

Television Test Center; Association for Maximum Service Television, Inc.; KLAS-TV. Harrison, John (1693-1776) A British clockmaker who devised a means, in the 1770s, to create a portable chronometer to aid in marine navigation by determining longitude, even when being bumped around by heavy seas. Several countries have acknowledged Harrison’s contribution with commemorative postage stamps. Harvard Mark I A historically significant, largescale, automatic computer constructed by Howard H. Aiken and IBM engineers in the early 1940s. The concept was proposed by Aiken as he was finishing his graduate work at Harvard University in 1939. In his report, Aiken envisioned a calculating machine that embodied some of the concepts of Charles Babbage, one that could handle cumbersome mathematical equations too lengthy or time-consuming for humans. Aiken’s concept led to support from International Business Machines (IBM) to build the machine at the IBM labs in Endicott. Although most often remembered as the Mark I, it was also known at the time as the IBM Automatic Sequence Control Calculator. The Mark I was a 35-ton electromechanical behemoth that had a number of characteristics to distinguish it from basic calculating machines, making it a true historic computer. It used magnetically-operated switches to handle the logic patterns, included central processing units and multiple storage registers, and could run (and rerun) instructions stored on prepunched paper tape. For the realization of Aiken’s goals, it was capable of working out mathematical equations to 23 significant digits. By the spring of 1944, the machine had been moved from the IBM labs to Harvard University and began to be known as the Mark I. At Harvard it was put into service by the U.S. Navy for military calculations in the aftermath of World War II. Three programmers were involved on the project in the 1940s; the best remembered is Grace Hopper, who joined the project in 1944, after Richard Bloch and Robert Campbell. See Aiken, Howard; Hollerith, Herman; Hopper, Grace. Harvard Mark II The second in the series of largescale computing machines developed under the direction of Howard Aiken, the Mark II was designed to replace some of the mechanical elements of the Mark I with electronics. It also took advantage of some of the improvements in electronics technologies that had occurred since the early 1940s. World War II and the need for fast, complex computations provided motivation for funding and building more advanced computers after the success of the Mark I computer. The Mark II was completed in 1947 and Aiken put his attention to the development of the Mark III. Harvard Mark III Third in the line of large-scale computing machines developed under the direction of Howard Aiken, the Mark III was delivered in 1951 to the U.S. Naval Surface Weapons Center. It improved upon earlier Mark computers and on many

competitors by incorporating drum memory with separate drums for instructions and data. Harvard Mark IV Fourth in the line of large-scale computing machines developed under the direction of Howard Aiken, the Mark IV was the last in the series, with Aiken working on the project until 1952. Hauksbee the Elder, Francis (ca. 1666-1713) An English artisan and experimenter who built on the work of R. Boyle and associated with Isaac Newton. Hauksbee did studies in static electricity and created a pump, in the early 1700s, that apparently improved upon earlier designs and prevailed for the next century and a half. The availability of pump technology was important not only for commercial pumping of oil and water, but because the ability to create a good vacuum was invaluable to scientific exploration and the study of sound transmission, magnetism, and electricity. A Hauksbee air pump, ca. 1708, is listed in the King George III Collection at the London Science Museum, and there is a ca. 1720 Hauksbee pump in the Museum of the History of Science in Oxford. When he was joined by James Hodgson, in 1702, Hauksbee was already employed by the Royal Society to demonstrate experiments. By 1705, he was an instrument supplier and became a fellow of the Royal Society, the same year he reported on his experiments with producing light in a mostly evacuated mercury vessel. At about the time he started giving science lectures with James Hodgson. Hauksbee’s research led to further experiments, and the observation that lampblack particles would move up and down very rapidly and make an audible sound when a glass tube that had been rubbed was held above the particles. Following this observation, he devised a rotating wheel to allow the glass to be rubbed at a great rate, in essence inventing a friction generator. In 1709, Hauksbee described his discoveries in his self-published Physico-Mechanical Experiments on Various Subjects. The book was republished in Italian in 1716 and in English by J. Senex in a larger edition with several new experiments, in 1719. In 1754, a French edition was released. Hauksbee also described experiments with capillary action in Philosophical Transactions, in 1712. Hauksbee did not have an extensive formal education and was not highly literate, but his mechanical aptitude and talent for experimentation were exceptional and earned him the respect of his peers. See barometer; Boyle, Robert; Gray, Stephen; Guericke, Otto von; Hodgson, James. [Source for birth/death dates: Jeanette (Jan) Shermer, descendant.] Hauksbee the Younger, Francis (ca. 1687-1763) An English instrument maker and scientist, the nephew of Francis Hauksbee, the Elder, listed here mainly to distinguish him from his uncle of the same name with whom he is often confused (Hauksbee the Younger was also a member of the Royal Society). Hauksbee carried on the tradition of experimentation and scientific inquiry of his uncle and set up an outlet for the distribution of scientific devices. The

Charles Townshend Papers list a 1757 communication about a Francis Hauksbee having developed medicine for the treatment of venereal disease. Hayes Microcomputer Products Inc. One of the early entrants to the modem market, Hayes set many of the industry’s de facto standards for serial communications through modems. Hayes modem control commands are still widely used. See AT commands. Hayes Standard AT commands See AT commands. HBA See host bus adapter. HBS See Home Base Station. HCI 1. See Host Command Interface. 2. human computer interface. 3. See Human Computer Interface standards. HD See half duplex. HDB3 High-Density Bipolar Three. A signaling scheme used in high-speed digital networks, especially phone networks. HDB3 is based upon Alternate Mark Inversion (AMI) and uses positive and negative pulse states. If four or more zeroes are sequentially transmitted, HDB3 inserts a violation code, an enhancement on basic AMI transmission. The insertion of the violation bits facilitates the reconstruction of the signal at the receiving end. HDB3 and other enhanced signaling schemes have been superseding AMI. See Alternate Mark Inversion, B8ZS. HDD See hard disk drive. HDLC See High Level Data Link Control. HDSL See high bit-rate Digital Subscriber Line. HDT Host Digital Terminal. HDTV See High Definition Television. head A device for reading, writing, or removing data from a volatile storage medium (usually magnetic). VCRs, hard drives, floppy drives, and tape recorders all have heads that touch, or nearly touch, the surface of the storage medium in order to transmit the information to the logic circuits or mechanisms that decode the information into human-meaningful form or to write to the storage medium. head thrashing If read and/or write heads on storage mechanisms encounter hardware or software problems, especially bad sectors, the mechanism may start to oscillate rapidly, sometimes uncontrollably. This can lead to damage to the head or the data if not terminated in time. header 1. Identifying text printed in a block at the head of a file or document. Header information frequently includes file format, version, date of creation, author, and typographic information. Header files are common to word processing, desktop publishing, and EDI applications. 2. A commonly used system routine contained in a separate file and referenced during program compilation and linking. System windowing routines and graphics routines are frequently linked in from header files. A header provides modularity and a write-once-use-many solution to many programming tasks. 3. In ATM, the protocol control information located at the beginning of a protocol data unit.

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header area In an EDI file, the area that contains the header information for the document. See EDI, header. Header Error Control HEC. In ATM transmissions, an error detection mechanism contained in a byte at the end of the 53-byte ATM header. It corrects single bit errors and is efficient over transmissions media with low bit error rates (BERs) such as fiber optic cable. In ATM carried over wireless transmissions, the signal is not as clean as a fiber optic signal, and the BER rate can be substantially higher. Satellite transmissions tend to be especially bursty, a situation not handled well with a single bit error mechanism. Some satellite service providers have compensated for this by developing a variety of solutions, including interleaving of cells to isolate the data from burst errors. See ATM Link Enhancer. headlight antenna A small radar antenna with a beam like a searchlight that can be housed in the wing of an aircraft. headphone A listening device designed to fit comfortably on the head, with vibrating diaphragms for one or both ears. Designed so the user can listen to private audio input (communications, music, etc.) without distraction from outside noises and without disturbing others. headset A radio or telephone transceiver unit worn on the head or wrapped around the ear (sometimes referred to more specifically as an earset). Headsets are typically used by professionals who sit and take many calls, including receptionists, console attendants, telemarketers, and reservation takers and by those on the move, including truckers, warehousers, and ground staff. Headsets are also becoming a consumer item for use with cellular phones (so drivers can keep both hands on the wheel) and other handsfree applications. heap memory A type of local memory storage that is dynamically allocated while a program is running. Heap memory is usually of more concern to applications programmers than to users, but there are some applications in which heap memory needs to be set prior to running the software in order to provide enough working room for memory-intensive applications. On some systems, heap memory is limited to a maximum of 64 kilobytes. heat sink A structure for dissipating or radiating heat away from a heat-generating device such as a semiconductor. Heat sinks often resemble open coils, flat fence rails, or other repeated, spaced elements, usually of metal, that are configured to increase their surface area, and thus their radiating capacity. Some CPUs require surprisingly large heat sinks. Considering that many of these are in competition with similar processors that are smaller and cooler, one wonders if the heat is excessive and unnecessary. Heathkit EC-1 Educational Analog Computer A historic hobbyist computer, introduced in 1959 or 1960 as a Heathkit, a Daystrom product line that was very popular with computer hobbyists in the late 1970s and early 1980s (until it became cheaper to buy a system than to build one from a kit). The EC-1 (Educational Computer-1) was one of the earliest

low-cost desktop computers, selling for $199, and one of the last of the analog computers. It had a steel chassis supporting rows of knobs and status lights, looking much like the Altair digital computer that came out a decade and a half later, and it could do basic calculations. It was marketed mainly to educational institutions teaching applied physics and mathematics. See Altair, Arkay CT-650, GENIAC, Kenbak-1, Simon. Heaviside layer See Kennelly-Heaviside layer.

English telegrapher and physicist Oliver Heaviside made philosophical and mathematical contributions to our understanding of electrical phenomena.

Heaviside, Oliver (1850-1925) An English physicist who started as a telegrapher. He later became interested in electricity and began publishing on that subject in 1872. He made thorough studies of Maxwell’s equations and then set about simplifying them to two equations expressed in two variables. Along with J. J. Thompson, Heaviside theorized about the electromagnetic reactions and mass of electrically charged particles in motion. See KennellyHeaviside layer, Maxwell’s equations. HEC See Header Error Control. hecto- (symb. - h) A Système Internationale (SI) unit prefix for 100 or 102. Heisenberg uncertainty principle Proposed by W. Heisenberg in 1927, the uncertainty principle has since become a fundamental principle of physics. (Heisenberg formulated a model of the structure of an atom in the 1930s which has held up well over time.) In studying movement of electronics, Heisenberg proposed mathematically that it is not possible to determine precisely both the position and the velocity of a material particle at the same time. The uncertainty increases as the size of the particle decreases. Many researchers have generalized this principle and restated it in various broader contexts, but most commonly it is brought up when describing the results of quantum experimental results. It is said that these

are determined in part by the point of view and methods of the researcher. For example, if light is studied as a particle phenomenon, it appears to behave as a particle phenomenon. If it is studied as a wave phenomenon, it appears to behave as a wave phenomenon, at least as far as the observers and measuring instruments are concerned. In other words, attempts to pin down precisely the location of an electron obscures its energy level, and vice versa, thus challenging the absolute nature of the world suggested by classical physics. Heisenberg, Werner (1901-1976) A German physicist responsible for deriving a theory of atomic structure and proposing the uncertainty principle in 1927, which has since become widely associated with his name. Heisenberg built on the work of previous physicists and mathematicians, including Hermann Weyl. For his contributions, he was awarded a Nobel prize in 1932. In the 1940s, he acted as the director to the Kaiser Wilhelm Institute for Physics. Near the end of the second World War, Heisenberg was captured by American troops and taken to Britain. When he returned to Germany, he helped found the facility that became the Max Planck Institute for Physics. During his later years, he was working to formulate a unified field theory of elementary particles.

Werner Heisenberg was a Nobel laureate who studied the motion and behavior of electrons at the quantum level and challenged many of the accepted notions of classical physics.

held call See hold. helical antenna, helical beam antenna An antenna designed with a helical (spiral) conductor wound in a circular or polygonal shape. The axis of the helix is usually mounted parallel to the ground. The circumference size of the helix in relation to one wavelength affects the angle of radiation. heliochrome [sun color] An older word for a color photograph, that is, one photographed in color as compared to one photographed in grayscale and tinted by hand using oil pigments. Color photography was not widespread until the 1960s.

heliograph [sun writing] A visual signaling system employing light signals, which was established around 1865 by H. C. Mance. The heliograph took advantage of the production of glass mirrors in the 1840s to increase the distance over which sunlight could be reflected. It used adjustable mirrors mounted on tripods and could convey messages in Morse code in daylight up to about 100 miles. In the United States, leaf shutter versions of the heliograph were developed to interrupt the light signals instead of directing the angle of the mirror as was done with the earlier British heliographs. Most visual signaling systems were superseded by wire telegraphy, but the heliograph survived for several decades, probably because it used Morse, which was then becoming widely accepted, and because it required no external power source. Since heliograph signals and microwave transmissions share some of the same line-of-sight characteristics, heliographs were resurrected to research the placement of microwave relay stations, and the heliograph is still sometimes used for military communications in regional conflicts where other means of communication are scarce. heliography [sun recording] A type of early photographic process, also called sun drawing, which was pioneered by French inventor, Joseph Nicephore Niepce, in 1816. Originally Niepce used a camera similar to the camera obscura to imprint temporarily an image of light onto paper coated with silver chloride. It was several years before he developed the process to the point where the image could be permanently preserved. See Daguerré, Louis; photography. helionics The science of the conversion of solar energy to electrical energy. heliotrope [sun turning] An early surveying instrument that employed the sun’s rays to triangulate from mountain prominences. This instrument was developed and used for the highly successful engineering feat of surveying India in the 1800s. It may also have been used for signaling. It was later adapted as a heliograph by H. C. Mance in Britain and used for many decades for daylight signaling of military communications up to 100 miles. helium-neon laser A type of low power gas laser, commonly used in light shows and monitors. This laser produces warm color tones in the red-orange range. helix, helical shape A spiral, continuous coil. Many types of springs employ a helix shape. In radio transmissions, a horizontal- and vertical-polarized wave combined as circular polarization, is transmitted in a helical fashion so that it can be picked up by both horizontal- and vertical-polarized antennas. Hellman-Merkle A trapdoor knapsack cryptography system principally designed by Ralph Merkle, with input from Martin Hellman, who was a collaborator with Whitfield Diffie on another cryptography system. The Hellman-Merkle scheme was found to be breakable and was reported as such in 1982. See Diffie-Hellman.

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hello A ubiquitous greeting to indicate a person’s acknowledgment of a call (see handshake), especially on a telephone. Since people may have been greeting one another face-to-face with “hello” before the invention of the telephone, it’s likely that its use as a standard greeting originated quite naturally. Nevertheless, on early telephones there was probably some discussion as to the best way to alert the callee of the incoming call and of the most natural way to initiate a call. Hello Girls One of the many historic colloquial names given to the female telephone operators. Others include Voice with the Smile, Central, and Call Girls. Helmholtz, Hermann von (1821-1894) A German physicist who expressed relationships between fundamental phenomena, such as heat and light, by treating them as manifestations of a single force, a concept we now associate with energy. Helmholtz further sought to generalize the concepts put forth by James Joule. Helmholtz encouraged the work of Heinrich Hertz, who became one of the true pioneers in the discovery of the physical existence and properties of radiant energy (radio waves). The Hermann Helmholtz Association of German Research Centers (HGF) continues Hermann Helmholtz’s tradition by supporting research on scientific, technological, and biomedical topics through a consortium of centers. See Hertz, Heinrich. http://www.helmholtz.de/ help desk A central information and assistance facility found in many large public-service or retail commercial institutions. The help desk is sometimes combined with the reception desk. In the computer industry, the analog to the help desk is the technical support line. Unlike help desks where you can tell if someone is available to help you and where you typically wait only five or ten minutes, tech support lines may be automated so that you don’t know if you’ll ever be served by a human being, and it’s not unusual for large companies to keep you on hold for one to three hours, a situation that shouldn’t be considered acceptable. henry A unit of inductance in a circuit (self-inductance or mutual inductance of two circuits) such that the electromotive force of one volt is produced when the inducing current varies at the rate of one ampere per second. Named after Joseph Henry. Henry Ford Museum & Greenfield Village The largest indoor/outdoor museum complex in the U.S. providing authentic historical artifacts and educational activities. Among other fields, it features exhibits on the history of transportation and communication, including Thomas Edison’s Menlo Park Laboratory. The Henry Ford Museum is located in Michigan State. http://www.hfmgv.org/ Henry magnet Joseph Henry experimented with electromagnets in the 1820s and 1830s, creating a number of different configurations. The Henry magnet is a type of experimental magnet, powered by a quantity battery, that he called a “quantity magnet.” The horseshoe-shaped magnet was wrapped with several layers of insulated wire connected in paral-

lel. Henry also experimented with a magnet powered by an intensity magnet that could power devices at a distance. Henry based his magnets on his studies of electromagnetism and the work of previous magnet researchers. As an improvement to earlier attempts, Henry’s powerful quantity magnet could transform enough electrical energy into mechanical energy to be useful. Thus, Henry himself experimented with the practicability of the electromagnet for powering rudimentary telegraphic systems and he communicated his ideas to many eminent inventors who built upon his ideas and put them into commercial use. See Henry, Joseph. Henry, Joseph (1797-1878) A gifted American physicist who began experimenting with magnetism in 1927, Henry produced a high-power industrial electromagnet in 1931. He incorporated his various discoveries into many practical devices, including telegraphs, relays, and electromagnetic motors. Joseph Henry actively encouraged and assisted other researchers, in addition to carrying on experiments himself, a fact that was not always publicly acknowledged by the many inventors who benefited from his generosity. Morse, Wheatstone, and many other inventors were assisted by the information communicated on both sides of the Atlantic by Joseph Henry. Joseph Henry advocated a science and research focus for the great Smithson endowment that eventually became the Smithsonian Institution, and he was appointed its first Secretary in 1878. He also cofounded the U.S. National Academy of Sciences. The henry, a unit of inductance, is named after him (1891). See Henry magnet.

magnet battery power source

Over the years, Joseph Henry developed many types of experimental electromagnets and generously shared his technological discoveries with other inventors.

HEP high energy physics. HEPIC High Energy Physics Information Center. An informational link among worldwide HEP resources to assist researchers in locating sources and resources. One of the services is a global search facility for searching across HEP Web servers that is updated about once per month. HEPIC is funded by the U.S. Department of Energy Division of High Energy Physics. It is supported by the Fermilab Computing Division. http://www.hep.net/

hermetic seal A seal that is airtight and leaktight, and is sometimes used to preserve a gaseous environment, inside a sealed device, that is different from the gaseous composition outside. Hermetic seals are generally intended to be permanent. Hermetic sealing is used in a variety of industries, including electronics and electrical installation. Herrold, Charles D. “Doc” (1875-1948) An American inventor and educator, Herrold is one of the first experimenters to transmit voice over distance. He did this through Station FN in the Garden City Bank Building, beginning in 1909. He became known by amateurs for his station SJN broadcasts. When Lee de Forest’s transmitter failed, Herrold provided music and news to the 1915 World’s Fair about 50 miles away. He had other interests as well and was awarded a patent for the Arc Phone in 1915. In 1922, he was broadcasting at 833 kHz through station KQW from San Jose, California. See KDKA, radio history. hertz Hz. A unit of frequency expressed as one cycle per second, named after H. R. Hertz. Hertz antenna An antenna system that uses distributed capacitance to determine its resonant frequency, which, in turn, is influenced by the physical length of the antenna. This antenna is used in applications where ground reflection is not a necessary factor for its functioning. Unlike Marconi antennas, a Hertz antenna is not dependent on the ground or the body of a vehicle as a resonant conductor. This type of antenna is common for television and frequency modulated (FM) broadcasts. See antenna, Marconi antenna. Hertz, Heinrich Rudolf (1857-1894) A German physicist who demonstrated important properties of electromagnetic radiation, discoveries that later experimenters applied to facilitate the transmission of radiant energy. By 1887, the physical existence of radio waves had been established. He also contributed a streamlined reformulation of Maxwell’s equations that was widely accepted. The Hertz antenna and hertz unit of frequency are named after him. See Helmholtz, Hermann. Hertzian waves Electromagnetic waves in the range from about 10 kHz to 30,000 GHz. James ClerkMaxwell had proposed that rapidly vibrating electric currents would emit waves, and Hertz experimentally confirmed this proposition. The waves are named after him. See radio wave. Hertzstark, Curt (1902-1988) A Viennese inventor who devised handheld calculator technology that was patented in the late 1930s, but wasn’t produced until the mid-1940s. Its accuracy apparently rivaled many modern devices. See Zuse, Konrad. hetero- Prefix for different, other, not usual. It is often used to describe a mix or variety. heterodyne v.t. To produce a beat between two frequencies, which could be of various kinds: audio, optical, or radio. In radio heterodyning, an electrical beat can be selectively created and controlled by heterodyning a received signal current with a steady introduced current. The frequency thus formed can then be further processed by amplification, as in

repeater stations or filtering. See beat, beat frequency, heterodyne repeater. heterodyne repeater A frequency repeating system commonly used in the propagation of radio signals that uses heterodyning to create an intermediate frequency through demodulation, which is amplified, modulated, and retransmitted over the next leg. This technique is less subject to distortion and loss through modulation/demodulation than baseband repeating. Heterodyne repeating may be used in conjunction with baseband repeating if the signal is traveling through several legs and some channels need to be dropped off at the baseband stations. See Armstrong, Edwin H.; baseband repeater. heuristic problem-solving An exploratory problem solving strategy that employs successive trial and evaluation of the results in such a way that the results can be used in the subsequent trials to “home in” on a solution. Heuristics are often used in artificial intelligence programs where the result is not known in advance, and where brute force methods are inappropriate due to the large number of possible choices and outcomes. Chess playing programs, for example, use a combination of heuristics to handle novel situations and databases of known moves and strategies. Heuristics are common in robotics, where a robot may have to interact with an unknown or unpredictable environment. See algorithmic problemsolving, brute force problem-solving, neural network. Hewlett, William R. (1913-2001) An American inventor and business tycoon, Bill Hewlett was a founder of Hewlett-Packard along with David Packard. An instrumentation engineer, Bill Hewlett invented an audio oscillator which was used by Disney Studios in the production of Fantasia. He was a past president and director of the Institute of Radio Engineers (now the IEEE), an honorary trustee of the California Academy of Sciences, and held many other professional and civic leadership positions. A prominent Silicon Valley pioneer and philanthropist, Hewlett was known personally by many of the prominent personalities in the emerging small-scale computer revolution. Hewlett-Packard Company HP. In 1938, Dave Packard and Bill Hewlett, both graduates of Stanford University, began working out of a garage in Palo Alto, California. Their first product, an audio oscillator resulting from Bill Hewlett’s research of negative feedback, was designed to test sound equipment. It was a new type of design, utilizing an incandescent bulb to provide variable resistance. This product was followed by a harmonic wave analyzer. Their first big client was Walt Disney Studios. Disney ordered eight oscillators for the production of the movie Fantasia. From these beginnings, Hewlett and Packard formed a partnership on New Year’s day in 1939; a toss of a coin decided the company name. HP was officially incorporated in 1947. Since then Hewlett-Packard has become a wellknown supplier of calculators, computers, software, printers, and other accessories to the computing

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industry. The firm is known for good quality products (their calculators have been known to survive the “drop-kick” test) and a corporate culture that seems to produce happier employees than many other companies in the industry. In 1996, David Packard, successful businessman and philanthropist, died at the age of 83, followed by William R. Hewlett, in 2001. HF, hf 1. hands free. 2. See high fidelity. 3. See high frequency. HFC See Hybrid Fiber Coax. HFU hands-free unit. An abbreviation applied largely to telephony products such as cell phones that can be used in a car without taking hands off the steering wheel or telephone headsets that can be used by receptionists without taking their hands off a keyboard. Hi band A video standard developed by the Sony Corporation in 1989 to support 500 lines of resolution on a TV screen. This resolution falls between NTSC and High Definition Television (HDTV). See Hi8mm. Hi-Band IR An infrared-remote technology used for remotely controlling a variety of consumer devices such as car stereo systems. Hi-OVIS Highly Interactive Optical Visual Information System. A Japanese cable television delivery system employing different types of cable for different parts of the service network. Hi8mm A high-quality, analog, tape-based compact video system developed by Sony, Hi8mm became especially popular in the late 1990s. Hi8mm has many benefits, including small cassettes, only 2.5 x 3.6 in. for two hours pf recording/playback at regular speeds. The long play time gives Hi8mm an advantage over S-VHSc (compact S-VHS). The small cassette format enables video camcorders and playback decks to be compact as well. The sound quality is excellent, compared to older technologies, and features stereo sound, though not all Hi8mm camcorders have two microphones. The video resolution of 400 lines and signal-to-noise ratio of 40 to 50 dB are equal to S-VHS and far superior to 240-line 35 to 45 dB VHS formats. For analog recording, Hi8mm is likely to remain a viable, favorite format for some time. It will probably eventually be superseded, however, by digital technologies offering 500+ lines of resolution, CDquality sound, and digital nonlinear editing capabilities without conversion. HiFD A 3.5-in. floppy diskette system developed jointly by Sony and Fujifilm, introduced in 1997. HiFDs are double-sided, with a magnetic storage capacity of up to 200 megabytes. hibernation A resting state, one of low energy usage and activity. A term often applied to the sleep mode on portable computers, which powers down during times of low activity to extend battery life. Hibernation has also long been applied to software applications that lie dormant waiting for some event causing them to become active, or to run at a higher priority level. The event that rouses the program can

be many things, including the time of day, input from an interface device such as the mouse or keyboard, activity of users, or data from another program. See sleep mode. hickey A spot, halo, or other imperfection in the ink or toner of a printout caused by undesired extraneous particles, dried ink, etc. hierarchical file system An organizational structure common to system and user files that arranges files in folders or directories in a descending tree. hierarchy A group of items, people, or processes ordered according to some type of structure or rank, usually top-down or bottom-up. A hierarchy may be nested. Hierarchies are generally designed to facilitate the location of some item within the hierarchy or to simplify the understanding of its contents. People in an organization, and files or discussion groups on a computer or network system are often assigned positions within hierarchies. High Altitude Long Endurance HALE. Pilotless platform crafts intended to float above commercial aircraft at about 20,000 meters, which have been proposed as two-way communications links capable of carrying phased antenna arrays. The HALE systems are experimental and a number of systems from helium to jet-engine propulsion have been proposed. The cost relative to traditional satellites makes HALE transceivers attractive to developers. Actual deployment of these systems has to take normal aircraft safety and traffic patterns into consideration. high ASCII There really isn’t such a thing, since ASCII defines the lower 128 characters (0 to 127), but “high ASCII” and “extended ASCII” are often used to describe characters above decimal values of 127, which are different on each system. See extended ASCII. high bandwidth slang Descriptive of a person with high level, wide-ranging intellectual abilities. The author first heard this phrase in the early 1980s among hard-core programming friends in computer users groups and suspects it originated spontaneously in a number of places and subsequently spread through networks such as Fidonet. Other computerrelated terms that have been applied metaphorically to human intelligence include high baud rate, high clock speed, and multitasking. high bit-rate Digital Subscriber Line HDSL. A digital transmissions technology that can transmit DS-1 or E-1 transmissions for longer distances over the traditional, unshielded twisted-pair wire that is widely installed in telephone circuitry. HDSL is typically used in digital loop carrier systems, private branch networks, and cellular antenna systems. Unlike earlier technologies, HDSL transmits over multiple lines without repeaters and uses techniques to pack more information in less bandwidth. It provides rates up to 1.544 Mbps over DS-1 or 2.048 Mbps over E1 in the 80 to 240 kHz bandwidth range. See Digital Subscriber Line, DS-. High Definition Television HDTV. In 1987, the Federal Communications Commission (FCC) acknowledged that the NTSC television was out of date and

formed an Advisory Committee on Advanced Television Service (ACATS) to recommend a revised television standard for the U.S. Most of the improved systems proposed to the FCC were analog or hybrid analog/digital. The FCC stated a preference for a simulcast HDTV system and identified four digital systems. These were extensively analyzed, leading to an ACATS recommendation that digital HDTV should be adopted. In 1993 an alliance was formed in cooperation with ACATS to create an HDTV system, with a specification released in 1994. high Earth orbit HEO. An orbiting region around the Earth into which certain types of communications satellites are launched. There are advantages and disadvantages to high orbits. The main advantage is that it takes fewer satellites to provide global coverage. Disadvantages include the higher cost of launching, the higher amplification needed for signals to travel the greater distances, and the effects of radiation. The lifespans of high-orbit satellites tend to be around twelve to fifteen years. Most high-orbit satellites travel at about 20,000 to 40,000 kilometers outside earth. High Earth orbit satellites are typically used for geostationary satellites such as the U.S. Global Positioning System (GPS). See low Earth orbit, Global Positioning System, medium Earth orbit. high fidelity A playback system that reproduces the original so well that it is indistinguishable, or almost indistinguishable, from the original source. This quality is often accomplished through fast transmission and wide bandwidths. In audio systems, high fidelity is frequently abbreviated hi-fi. high frequency A signal frequency defined as the range from 3 and 30 MHz. High Level Data Link Control HDLC. An ITU-T standard bit-oriented data link layer communications protocol originally developed by ISO for managing synchronous serial transmissions over a link connection. In HDLC there are separate bit patterns for control and data representation. high level language A computer programming language at the user level, designed to be as close to a natural language as possible and generalizable to a variety of platforms. FORTRAN, BASIC, and COBOL are probably the best-known and most widely used high level languages. High level languages are often interpreted, but may be compiled for the specific platforms on which they will be running. As languages become closer to machine level, they also tend to be more symbolic and, thus, more difficult to read and write. They also increase in platformdependency. For contrast, see assembly language, low level language, machine language. high pass filter A filter designed so it doesn’t pass waves below a specified cutoff frequency (greater than zero), and the transmission band extends upward indefinitely from that cutoff point. See low pass filter. High Performance Computing Act An act of the U.S. Congress which was passed in 1991 to facilitate and promote the development and evolution of interconnected computer networks serving

educational institutions, research laboratories, and industry. High Sierra standard A compact disc standard introduced in 1986 by the High Sierra Group (named after the hotel and casino at which the group met). It was subsequently adopted by ECMA (ECMA-119) and ISO (ISO 9660) and released with slight revisions. See ISO 9660. High Speed Data Unit HSDU. A physical data communications device to provide a high-speed data channel together with control signals from, for example, a serial connection. HSDU may be software configurable and may operate in synchronous or asynchronous modes or both. high speed networking This is a relative phrase and will change as the technology advances but, in the mid-1990s, high speed networking was generally considered to be around or over 100 Mbps. Examples of high speed network technologies include asynchronous transfer mode (ATM), Fast Ethernet, and Fiber Distributed Data Interface (FDDI). high speed printer Printers with the capacity to feed paper, print on it, and eject (and sometimes collate) at industrial speeds that exceed consumer printer speeds by a significant margin. The speed that constitutes high speed changes as the technology improves and is set arbitrarily, often by marketing managers. Most consumer printers print at about five or six pages per minute (about 100 to 150 lines per minute). It’s reasonable to say that a high speed printer, such as a line or page printer or fast laser printer, has an output of about 500 lines per minute, or about 15 pages per minute or faster. High Speed Technology HST. A U.S. Robotics proprietary, high-speed, full duplex signaling and error control transmission protocol. U.S. Robotics manufactures modems complying with this protocol and some dual-standard modems that are both HST and V.32 bis capable. See Microcom Networking Protocol, modem, V Series Recommendations. High Speed Token-Ring HSTR. An enhanced commercial Token-Ring technology developed by International Business Machines (IBM). HSTR can run Token-Ring and Ethernet on one medium, support source routing through data packet headers, and was based on existing standards, including Fibre Channel. Aimed at a market similar to Ethernet, HSTR appears to be primarily supported by those upgrading legacy Token-Ring systems. See Token-Ring. high usage groups In the telephone industry, high usage groups are trunks between main switching offices that are established as priority routes to handle the majority of transmissions. High usage trunk groups are intended to hand off overflow traffic to alternate trunks. See erlang. high-threshold logic HTL. A concept used in physics and electronics especially with regard to computer circuit designs. Voltage thresholds are voltage levels at which more or less voltage may have no further effect or at which more or less voltage (at the high or low thresholds, respectively) could damage a system or render it inoperable. They are also points

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at which state changes may occur due to unconditioned or noisy signals. In transistor-based devices, the threshold voltage is related to performance levels and is often used to control the characteristics and operation of a system. Conventionally, on portable devices, lowered power is associated with degraded performance and power leakage. However, the use of high-threshold transistors is seen as one means to extend battery life on low-power devices, such as cellular phones, while in standby power mode without adversely affecting performance. High-Density Bipolar 3 See HDB3. High-performance Network Forum HNF. Developers and promoters of the HIPPI GSN standards. European High-performance Network Forum (EHUG) works in cooperation with HNF and coordinates an annual network technical symposium. http://www.hnf.org/ high/low tariff A charge that is selectively made according to a type or level of service. For example, some Internet Service Providers (ISPs) charge different rates for connection time depending upon the speed at which the subscriber’s modem connects. A bulletin board service (BBS) may quote two levels of service depending upon whether or not the user wants to access the games sections. In phone services, two prices may be quoted for a subscriber call, one cost per minute over high density trunks and a different cost per minute over low density trunks. Hindenburg disaster The terrible crash and flaming destruction of the Hindenburg dirigible in New Jersey in 1937 is etched forever in the minds of those who heard the live radio broadcast of its demise. This historic tragedy was relayed and captured by new technology, radio and tape recordings, in a way that had not been possible prior to the establishment of the broadcast radio industry. HIPERLAN high-performance radio local area network. A European standard for local area networks (LANs) that are interconnected through radio frequency transmissions rather than through wires. Unlike North American radio-based LANs, that are largely based on sharing unlicensed 900-MHz and 2.4-GHz spectrums, HIPERLAN was allocated dedicated spectrums in the 5.15- to 5.30- and 17.1- to 17.3-GHz frequency regions by CEPT, in 1992. A draft standard was developed by ETSI and presented as a functional specification in 1995. The availability of dedicated bandwidth increases the probability of reliable service with less chance of outside interference. See air interface, local area wireless network. HIPPI High Performance Parallel Interface. HIPPI is a point-to-point high speed data transfer technology created at Los Alamos in the 1980s. HIPPI operates over twisted-pair copper cable for distances up to 25 to 50 meters (longer with cascaded switches) and distances up to 300 meters, or 10 kilometers over multimode or single-mode fiber cables. HIPPI was originally developed for supercomputing applications but is starting to be adapted to other environments with the dramatic drop in price of the

technology, particularly the switches. Transmission speeds include 800 Mbps and 1.6 Gbps (simplex or duplex). HIPPI can be employed with SONET over distances and over satellite transmission links. HIPPI is an ANSI standard with a series of documents spelling out the standard and its various switching and encapsulation characteristics. See HIPPI-6400. HIPPI-6400, SuperHIPPI High Performance Parallel Interface. Officially it is now known as Gigabyte System Network (GSN). A very high bandwidth, low latency network transmission technology which offers gigabytes-per-second transfer rates, much faster than the capacity of Gigabit Ethernet, ATM, or Fibre Channel. Based on the HIPPI standard, but with enhancements in error correction and lower latency rates, HIPPI-6400 uses a fixed-length cell of 32 bytes. Transfer rates that are as fast as, or faster than, the internal workings of an individual computer on a network will change computing in a significant way. With this development, the network is no longer a bottleneck and individual computers attached to the network can theoretically function as individual parts of the same organism, that is, as a massively parallel computing system. Fast transfer rates with high bandwidth also make it easy to support a diverse variety of protocols, providing flexibility. SuperHIPPI can support applications like uncompressed digital movies and HDTV signals. See HIPPI, Scalable Coherent Interface. Historic Speedwell Located in New Jersey, this museum features telegraph history through the daily life of the Vail family and their association with Samuel Morse. Morse had a close association with the Vail family who provided space, materials, and expertise to assist him in fabricating the inventions for which he is known. The Vail family is also known for the great success of AT&T. See Vail, Alfred; Vail, Theodore. hits 1. Number of system or application accesses of a specified type within a specified time period. 2. The number of attempts of illegal entry to a system within a specified time. This information is used to gauge security needs and adjust procedures, if necessary. hits, query In a database query, the number of items that match or contain the search criteria. If the initial number of hits brings up too many matches, it is usually advisable to narrow the search, and vice versa. Web search engines often bring up too many hits on the first try, but advanced search options allow the user to specify conditionals and priorities. hits, Web site On a World Wide Web site, the number of times a page or component of a page, is accessed or downloaded in a specified period. For marketing purposes, this information may be further analyzed according to time of day, specific items of interest, number of hits by different users, since one user may access a site multiple times, and subsequent ratio of hits to sales. HNF See High-performance Network Forum. HNS See Hughes Network Systems. HOBIS Hotel Billing Information System. Hodgson, James (1672-1755) A British mathematician and lecturer, Hodgson was evangelizing

scientific achievements at an important time in history when many significant historical figures, including Isaac Newton, Defoe, Hauksbee, and Boyle, were influencing the future of science and trade. Hodgson had been an assistant to the Astronomer Royal Flamsteed since 1696, but left that position in late 1702 to become a lecturer. Hodgson was versed in natural philosophy, experimental science, and mathematics, and joined Francis Hauksbee the Elder at the Royal Society during its leadership by Newton. In 1703, he became a fellow of the Society. As a lecturer, Hodgson advertised seminars in astronomy and philosophy promoting the discoveries of members of the Royal Society and demonstrated experiments. Hodgson began to write technology books by 1704 and apparently also tutored in the sciences. Hauksbee, a demonstrator for the Society, had an interest in these lecturers and the two began to work together, thus creating a forum for practical embodiments of Newton’s theories and some of Hawksbee’s own inventions. In 1706, Hodgson published The theory of navigation demonstrated. In 1709 he became a mathematics master at the Royal Mathematical-School in Christ-Hospital. In 1736, he published The Doctrine of Fluxtions Founded on Sir Isaac Newton’s Method, one of the early textbooks on calculus. Hodgson was an important impetus in bringing experimental science (which was still a relatively recent concept) and mathematics to the common man, primarily merchants, navigators, and tradespeople who recognized the value of new technologies to their professions. He is also one of the first to voice the basic principles of sonar, suggesting that sound could be used to estimate the distances of ships at sea and of land objects. See Hauksbee the Elder, Francis. Hoff, Jr., Marcian Edward (Ted) (1937- ) An American engineer who, in response to a request from a Japanese company for a calculator chip, designed the Intel 4004, in 1971. This highly significant invention was the first commercially successful microprocessor chip, and it launched the microcomputer industry. Hoff became a manager in the Applications Research division of Intel Corporation in 1968 and joined the 4004 development project. In 1983, he became Vice President of Atari, Inc., which was well known at the time for home computer systems and, in 1984, was awarded the IEEE Centennial Medal. In 1990, he was appointed Chief Technologist at FTI Teklicon, Inc. hold 1. To pause, to cause to remain in a particular position or situation. 2. While attempting a computer login, the user may be queued or put on hold until fewer users are on the system. This hold usually manifests as a pause after typing the username or after typing the username and password. On popular archive sites, there may be a hold period or increased lag time while accessing a system. Sometimes it’s better to log on later during off-peak hours, or to find a less busy mirror site, if one exists. 3. On phone

systems where the receptionist is busy with other calls, or the automated system is queuing the caller for the next available operator, the user is usually put on hold, sometimes for extraordinarily unreasonable lengths of time (especially if it’s a long-distance call). On systems that don’t have music or a recording informing you that you are in the queue, it is sometimes difficult to know if you are still on hold or have been cut off. On multiline systems, a call can often be put on hold by one individual and picked up by another (line hold). On some systems, the hold call can be continued only on the main console or by the person originally putting the call on hold (exclusive hold). Hold Recall An optional telephone feature that alerts you to the fact that someone is on hold. On most multiline systems and some residential phones, the line on hold will be identified by a flashing LED or, on more sophisticated systems, with beeps or voice messages. hold time 1. In circuits, the time interval after the clocking of a trigger circuit during which data must remain unaltered. 2. In welding or soldering, the time during which the welded object must be held relatively steady in order for the weld or solder to harden. 3. In telephony, the length of time a caller is kept waiting, and waiting .... holding beam A diffused electron stream used to regenerate charges applied to the surface of a storage tube. holding coil In a communications circuit, an additional coil in a relay for each direction of a transmission that can be opened or closed independently of the main circuit to enable a single circuit to accommodate alternate two-way communications. holding gun In an electron storage tube, the source of the electrons that make up the holding stream. holding time In telecommunications, the entire duration of a call from the time the connection is requested until it is completed and disconnected. The actual time during which the connection is established is only a portion of the holding time, although it’s usually the time that is billed. Holding time is important, for example, in tracking sales calls. How long does the sales representative or telemarketer actually stay on the line trying to connect a call and handle the entire transaction, as opposed to the amount of time actually spent with the customer? If there is a large discrepancy, another method may need to be tried. Holding time is also important in computer or telephone circuit planning and management because the time spent connecting and queuing the caller may affect capacity and efficiency as much as that portion of the call during which the communication takes place. holding trunk In telephone communications, a queue wherein a call is held until availability is established or an alternate route is found. holiday factor A concept in service and retail industries that accommodates changes in rates of service use or product purchase during holidays. The

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transportation, retail, and telecommunications industries tend to have patterns of higher usage during holidays and need to factor in extra staff, lines, products, etc. to handle the demand. Holidays may also create decreased demand, in which case shutdown or reduction of unneeded systems may result in cost savings. Hollerith card Historically, a sturdy, rectangular, piece of card stock organized into rows and columns that were individually labeled and further organized into sections. A circular hole was punched in the card to select the coded data in that region of the card. The punched holes could later be read and decoded to reassemble the original information. This concept was born out of the cards used to store loom patterns on Jacquard looms. In the 1920s, IBM, the evolutionary heir to the Hollerith Tabulating Company, introduced a patented rectangular hole that made it possible to encode almost twice as much information as the original round hole cards. Hollerith cards were used to store historic computing machine code in the days before tape, diskette, and hard drive storage. The punched card was, in effect, a binary storage system with the unpunched or punched locations representing off or on and corresponding to no or yes responses to a predefined parameter. As the storage capacity of these cards was quite limited, many cards were needed to store a body of information. Punch cards, in general, can be fully punched and read in again with mechanical or optical devices, or partially punched to provide a record without the mess and waste of chad and read again with sensing devices. In the case of Hollerith cards, the punched cards were read by an electrical reader that completed a circuit and activated a relay when a pin passed through a portion of the card with a hole. With the use of gang punches with selectable templates, up to 40,000 cards a day could be punched. The computer cards commonly used in library books, until bar codes became prevalent in the 1990s, are descended from Hollerith cards. See Hollerith Electrical Tabulating Machine, Jacquard loom, zero punch.

A sample of a punched Hollerith card in which the card has been organized in sections and labeled with alphabetic or numeric markers. [Railroad Gazette, April 1895.]

Hollerith code A 12-level code designed by Herman Hollerith in 1889 for use on Hollerith cards which, in turn, were used with the Hollerith Electrical Tabulating Machine. The card is sectioned and labeled and the code was implemented in the form of holes punched at specified intervals in designated rows and columns, with each column corresponding to an alphabetic or numeric character, in order to form a semipermanent record that could be read and interpreted in the future. This code was widely used in early computing days to store program instructions and data. Over time, variations were developed and EAI and ANSI standards were established to govern the configuration of the cards, holes, and data encoding. Hollerith code survived much longer than the Hollerith Machine, which was superseded by electronic computers. Hollerith code continued to be used in microfilm records, e.g., for storing microfilm image data and is still covered in Information Technology (IT) courses. For the processing of textual information, it has been superseded by other systems, including EBCDIC and ASCII. See Hollerith Electrical Tabulating Machine. Hollerith Electrical Tabulating Machine A mechanical-electrical data processing mechanism for quickly and accurately recording and classifying individual data from a variety of sources. It was developed by Herman Hollerith in the early 1880s. Hollerith’s machine came to prominence when it was selected (over a system developed by A. Graham Bell) to tally the results of the 11th U.S. Census, in 1890. Before Hollerith’s invention, it had taken almost a decade to process the results of a U.S. census. With the use of the Tabulating Machine by the Population Division of the Census Office, thousands of entries could be tabulated in a single day, thus greatly expediting the recording of over 60 million cards, one for each person included in the census. The 1890 census was processed in only a year. The Census Office continued to use the Hollerith Machine for further statistical analysis of specialized groups within the population. For example, in 1901, Bell was using the Hollerith machine to compile and process information from the census relating to the blind and deaf, with assistance from his wife on selecting and organizing the format and priorities related to the data (an important aspect of setting up the punch configuration and tabulation). After the census, other organizations with statistical tabulating needs looked into the use of the machine, including accounting and transportation firms. There were two main aspects to the Hollerith Machine: the adjustable punching mechanism for creating the data cards and the electrical pin-based reading mechanism for processing the cards, activating relays, and incrementing a counter. The letters and numbers organized on the punch mechanism’s keyboard could be altered to suit the type of data that was being entered. The Hollerith Machine received much publicity as a result of the 1890 census and caught the attention of other institutions, especially statistical and auditing

companies and departments. Variations and improvements were developed, with the tabulating and sorting functions sometimes implemented separately and sometimes housed in one unit. The Hollerith mechanical tabulating mechanism was to be an important impetus in the development of advanced calculators, the forerunners to early computers. See Harvard Mark I; Hollerith, Herman; International Business Machines.

The Hollerith Electric Tabulating System showing the punch on a movable arm poised over the card holder and a lettered and numbered keyboard hole alignments for the various data that were to be entered and stored on punched cards. [The Manufacturer and Builder, V.22, 1890.]

A Hollerith reader, the sorting and tabulating mechanism that was used to process the individual cards into statistical data once they had been punched with information relevant to the application. [Railroad Gazette, April 1895.]

Hollerith, Herman (1860-1929) An American engineer who devised a historic tabulating machine, in 1884, which he further developed with the concept of punched cards as an information storage medium. In 1889 he received a patent for his machine to compile statistics (U.S. #395,782). Hollerith was subsequently contracted to carry out the storing and reading of U.S. census information, beginning with the 1890 U.S. census. Following the success of this

invention, he formed the Tabulating Machine Company, in 1896, to market the technology. In 1911, it was merged with other companies to become the Computer Tabulating Recording Company, the historic beginnings of International Business Machines (IBM). See Hollerith Electrical Tabulating Machine. hologram A type of imaging using lasers, based on the recording of an optical interference pattern produced by the interaction of two or more waves from the same source. The effect of viewing a holographic image is a sort of 3D, when moving the head around and focusing on different parts of the image. In most cases, it is not fully a 3D effect, as the image is usually recorded on some flat (with transparent depth) medium such as glass or transparent plastic (although the technology itself is not limited to this form of presentation). The image is typically more ethereal than a photograph, since it is viewed through “layers” of the transparent medium. Projected holographic images hold great promise for 3D virtual reality, and scientists have been working on holographic memory modules for computers that potentially can store enormous amounts of information in small three-dimensional components. It has been suggested that human memory may share some functional similarities with holograms.

A later version of a Hollerith machine, a circuit closing press that was of interest to freight rail administrators in the 1890s. Passing the cards through an electrical reader caused a circuit to be closed and a relay to be activated whenever a hole was encountered. Displays of the progress of the reader could be read off status dials by the operator and logged or compared against charts, freight sheets, or other information. [Railroad Gazette, April 1895.]

holy wars Interminable subjective online discussions on subjects that have no definitive answer in a general context and have been beaten to death, such as

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your-computer-versus-my-computer arguments by people who have used only one type of computer. home In computer interfaces that distinguish regions of the screen for different functions, one corner is usually designated as the home position, that is, a position to where a pointing device may return, or where a cursor might start again after the region has been cleared or a new window opened. On English language-based systems, for example, the home position in a text window is usually the top left corner. If the text were being typed in another language that tracks from right to left, such as Hebrew, the home position would be the top right of the window or screen, or bottom right if it is bottom to top reading. In PostScript page layout programming, the home position is generally considered the bottom left corner, as it is with a number of printer graphics languages. Some systems have a home key as a one-step shortcut to position the cursor in the home position. home ATM network HAN. A broadband home network for providing connectivity with a variety of services and devices (computers, television, appliances, etc.). See ATM Forum, fiber to the home, RBB. home computer A computer configured for basic functionality and ease of use, in a price range low enough to be attractive to general consumers. home page A World Wide Web concept referring to the first, primary, or main page of a set of hypertext linked pages on a particular host, or belonging to a particular individual or organization. Web pages are not inherently hierarchical, since any page can link to any other, but humans tend to grasp concepts more easily when information is organized in a top-down or bottom-up manner, and home pages reflect our preference for this type of organizational structure. A home page serves as a jumping off point, table of contents, or general site information map to help navigate the rest of the links. Commercial sites tend to have home pages that showcase product information and entice the user to explore the rest of the site. Personal sites often show family relations, professional credentials, and personal interests. Educational home pages usually provide information on course offerings, faculty, and facilities. See HTML, hypertext, World Wide Web. home run A centralized wiring topology, like a star topology, in which cables to individual units or consoles all lead back to the central switching system. Most private branch systems, almost all key systems, and many of the smaller computer network systems have this type of cabling arrangement. In home run wiring, which has little or no redundancy, a severed line will cut off the end station from all other stations. See topology. Homebrew Computer Club A historic, influential, electronic thinktank and tinkerer’s organization, founded in California in 1975. Steve Wozniak is one of the most famous of the Homebrew members. The Altair was demonstrated at a Homebrew meeting, with homebrewers jumping on the opportunity to

write applications for this early computer. homeostasis A state in which there is a tendency toward balance, stability, or equilibrium. A state in which there is no change. homing 1. Zeroing in on an intended destination or target. 2. Approaching an intended destination by holding some parameter of navigation constant (with the exception of altitude). 3. In guidance systems, transmitting, receiving, and evaluating signals in order to locate a target. Bats and missiles use homing systems. 4. In telecommunications, homing is the selection of a route through which a call can be set to the next switching center, especially in toll systems, which may pass through several specified switching stations. homing pigeon One of the earliest means of distance communications, used at least as early as several hundred years BC in ancient Greece. Homing pigeons could be taken on journeys and then set free to fly home with messages. At first, just the appearance of the pigeon represented a prearranged signal. Later, an actual message, written on papyrus, skin, or reed was likely attached to the bird’s leg. Unfortunately, homing pigeons became extinct following the second World War. homodyne reception See zero beat reception. Honeywell Kitchen Computer Honeywell, in a blaze of optimism that is unique in entrepreneurial history, introduced one of their Series 16 computers as a home computer for the kitchen through the Neimann-Marcus catalog for $10,000, in 1969. It could store recipes, was programmable, and included kitchen accessories. To put the price in perspective, it cost roughly the same as four new cars or a small starter home, or five years’ gross wages for a person earning minimum wage. Even now, almost half a century later, there are few computers in kitchen environments, and it would be incredibly difficult to sell one for the modern equivalent of $80,000. As you might expect, the Kitchen Computer flopped. The Series-16 computers, from which the Kitchen Computer was born, were originally designed by Computer Control Company and bought out by Honeywell. They were released at about the same time as the Digital Equipment Corporation (DEC) PDP8 minicomputers. The Series-16 computers included the DDP-116 (1965), the DDP-516 (1966), and the DDP-316 (1969). The DDP-316 was essentially a physically reduced-size version of the DDP-516. By 1960s standards, the 316 line would probably be considered minicomputers, as they had 16-bit registers, with core memory and a memory read/write time of between 1 and 2 microseconds, which was pretty good compared to the low-cost microcomputers that came out a decade later. The main unit of the smaller models was about the size of a deep 17´´ CRT monitor. Like the later Altair, the units had lots of switches and status lights on the front panel. The Kitchen Computer was technically known as the H-316 Pedestal Model. Series-16 rack- and table-top models were available as well. Despite its spectacular lack of success in the kitchen

market, the Series-16 technology was not completely lost, as it eventually made its way into components used in the ARPANET (as interface message processors for connecting hosts), a more suitable market for cutting-edge, pioneer computing technologies. See Altair, PCP series computers. hook switch, switch hook The hook switch was originally designed not just to terminate a connection so the next call could come through, but served also to disconnect from a battery source so it wouldn’t be quickly used up, and later an electrical source. Modern telephones draw current from the line and don’t require a separate battery to operate the basic calling and receiving functions, but the hook switch, the hook on the side of an old traditional box phone or the buttons (plungers) on top of a traditional rotary desk phone, are still used for disconnecting a call, and sometimes for generating a tone (if they are held down briefly, which doesn’t cause immediate disconnection). See hooking signal. hook switch dialing On older wall box phones and rotary pulse phones, it was possible to dial a number by depressing the hook carefully for each number you wanted to dial. (Depressing the hook switch for too long would disconnect the line.) This is even possible on some of the older pay phones. See hook switch. hookflash A signal-sending mechanism whereby the hook on an old-style phone or button plunger on a newer phone is quickly depressed to signal the initiation of a service or operation. hoot’n’holler, holler down, shout down, squawk box A dedicated, four-wire, open phone circuit connecting speakers or speakerphones at each end of the connection round the clock. It’s like a 24-hour public address system using phone lines with full duplex, two-way communication. Other phones on the system can be picked in order to listen to the conversations ongoing on the speaker system. Hoot’n’holler systems are useful in industrial yards, institutions, and fast-paced financial floors where numbers of free-moving individuals look to centralized sources of information or engage in communal dialog at different locations. hop n. 1. The extent of an individual transmission path between two nodes (with no intermediate nodes). 2. In radio, the extent of a transmission from Earth to ionosphere and back. 3. In frame relay, the extent of an individual trunk line transmission path between two switches. 4. In an IBM Token-Ring network, the extent of an individual transmission path between two bridges. 5. In cellular communications, where the user may be traveling through several transmission zones during the course of a call, a hop is a change in the radio frequency channel. hop by hop/hop-by-hop routing In contrast to a system that predetermines a route before sending a transmission, hop-by-hop routing creates a route along the transmission path, a step at a time, by using routing information at switchers along the way. There are advantages to both. A predetermined route

may be an efficient one, designed to speed the transmission through faster links or perhaps by choosing the shortest path. This is common on small or local systems. On the other hand, on a large system like the Internet, there may be millions of possible routes, too many to store in the routing tables at the source of the transmission. In this case, hop-by-hop routing is a scalable technique that makes use of the best information at each station to progressively build a path for the data. It has been suggested that ATM implementations of hop-by-hop datagram forwarding on the Internet are no longer adequate to handle traffic volume and improvements have been suggested. See cell switch router, RFC 2098. hop channel In cellular communications, a radio frequency (RF) channel that is available to continue transmissions for a user with a call in progress who is moving through zones. Available channels are needed to continue uninterrupted transmission while the user is on the move. See cellular, hop, mobile communications. hop count The sum of the number of hops that make up a route between its source and destination, or between a specified segment of the route. In radio communications, the number of times the wave bounces from the Earth to the ionosphere and back. In networking, the hop count is the number of segments between individual nodes or routers, a number that is recorded in Internet Protocol (IP) packets on packet-switched data networks. In cellular, the number of times a radio frequency change occurred during the course of a call. Hop counts are one means to gauge the efficiency of a system and to configure or tune it for better performance. hop off To exit one type of system and complete the route on another. For example, you may initiate a facsimile transmission on the Internet, that then hops off to a phone line and a dedicated facsimile machine. Or, you may make a voice call from a telephone that is routed through a voice translation program and interfaces with the Internet and becomes an email message at the destination. In this case, the hop off is from the phone system to the Internet, or, conversely, you can consider it a hop on to the Internet, if you are considering the Internet as the main portion of the transmission route. Hopper, Grace Murray (née Grace Brewster Murray, 1906-1992) An American mathematician, physicist, and educator, Hopper was an originator of software compilers and developer of the COBOL programming language. She earned a Ph.D. from Yale in 1934 and spent many years as a lecturer, research scientist, and programmer for various organizations, including the U.S. Naval Reserve. Hopper became involved in many of the important computer development projects at the end of World War II. In 1944, she joined Howard Aiken’s Harvard Mark I project as its third programmer and later worked on the Harvard Mark II. Hopper is perhaps best known for relating a story in which a technician found a bug inside a Harvard Mark II and solved a problem by removing it. Grace

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apparently glued the bug into the computer logbook and, in the 1970s, announced that she would be contributing it to the National Museum of American History. Thus, the term computer bug was popularized. In the late 1940s, Hopper left the academic world to join the Eckert-Mauchley Computer Corporation where she had the opportunity to put her software theories to practical use. In the early 1950s, when new ideas about programming and reusing existing code began to evolve, she made what was probably her biggest contribution to the field. She became a champion of ideas that led to high-level languages, compiled software, and more efficient coding methods, even though many professionals claimed at the time that such things were impossible (they couldn’t see past the physical wiring of computers to a time when electronics would be used to channel signals automatically). In spite of detractors, Hopper contributed significantly in the transition from paper tape and punch cards to coding languages such as C-10. She further proposed that computers could be programmed in English, an idea that was ridiculed, and developed a compiler for business use with an English-like syntax for nontechnical programmers that evolved into COBOL. Hopper’s contributions were too significant to pass unnoticed, in spite of a tendency to downplay the accomplishments of women at the time. In 1969, she was awarded the Data Processing Management Association Computer Science Man-of-the-Year Award. In 1973, she became the first woman recognized as a Distinguished Fellow of the British Computer Society and, in September 1991, was awarded the National Medal of Technology by the U.S. President. See A-0, B-0, bug, Harvard Mark I.

Grace Murray Hopper was an American mathematician, physicist, lecturer, and one of the first computer programmers in the days when programming involved rearranging the wires within a vacuum-tube computer system.

hops See hop count. horizontal blanking interval, horizontal blanking time The period during which a display is suppressed on a cathode-ray tube (CRT) to allow the electron gun to return from the right side of the screen to the next display position down and on the left side of the screen (assuming left to right and top to bottom scanning as is present on most standardized framebased video display systems). See blanking, cathoderay tube, frame, sweep. horizontal cross connect The interconnection between a horizontal distribution system and a telecommunications central wiring location such as an equipment or patch panel closet or bay. horizontal distribution frame The equipment and structural elements that facilitate the interconnection of interfacility cabling configurations, as between subscribers and substations and central offices. The frame technically does not include the wiring but directs and contains it. Horizontal distribution frames are usually built into flooring or crawl spaces, hence the name. See distribution frame. horizontal link, inside link In ATM, a link between two logical nodes belonging to the same peer group. horizontal resolution A quantification of the amount of information that is contained on a single horizontal line of a rasterized output device such as a monitor or printer. On raster monitors, horizontal resolution is expressed in terms of pixels, usually about 800 to 1024. On black and white laser printers, horizontal resolution on consumer machines ranges from 300 to 1000 dots per inch (dpi), and on prosumer and industrial printers from 1000 to 2700 dpi. Thus, the total would be the number of inches times the dpi. A resolution of about 600 dpi or greater is needed to show clean lines and curves, without staircased artifacts, for common printed documents. A resolution of about 72 pixels per inch or higher on a grayscale or color display is preferred for video displays. Colors and shades of gray can be used to antialias a display to give it a higher perceptual resolution. horizontal scan rate A measure of the scan speed of electron beam display devices, usually described in hertz (Hz), as in cathode-ray tubes (CRTs) that sweep repetitively from left to right and top to bottom. The horizontal scan rate describes how many horizontal scan lines per unit of time (usually seconds) can be displayed. At a particular scan rate, the number of lines that can be displayed decreases proportionally as the refresh rate increases. Multiscan computer monitors permit a variety of scan rates and resolutions, most ranging from about 40 to 75 Hz. See cathode-ray tube. horizontal segment In wiring distribution systems, the wiring route from individual NAM or IO locations to the riser closets through ceilings or floors, usually up to a maximum of about 250 feet. horn alert An electronic connection for sounding a horn or loud buzzer to signal an incoming transmission during times when the user might be some

distance from the communications device. Horn alerts are used for after-hours phone calls or doorbells, for cellular phones in cars, and for a variety of security systems. horsepower hp. A unit of power designated as equal to raising 33,000 pounds one foot in one minute, which can also be expressed as an English gravitational unit of raising 550 pounds one foot in one second. In the U.S., a unit of power equal to 746 watts. See watt. host 1. One upon whom others depend for shelter or sustenance. 2. The main organizer and holder of an event. 3. It’s a little difficult to define host as it relates to computer systems because different groups of computer personnel have given host and client opposite meanings in the past. For consistency with the English meaning of the word and popular usage, this dictionary defines host as a main server or controlling system, and the client as a subservient system in terms of priority or capabilities. See client. host bus adapter HBA. A computer storage or network transmissions connectivity device. HBAs can be built into the motherboard or they may be available as optional peripheral cards. PCI Local Buscompatible HBAs are prevalent, but there are also HBAs for other formats, including FC-AL (Fibre Channel) and CompactFlash. The HBA handles lowlevel hardware controller interaction, including data I/O to the controller registers and data transmissions. HBAs are of interest for storage area networks (SANs), data warehouses, RAID systems, signal processing, video editing systems, and other high-capacity/high-throughput applications. HBAs for other formats such as CompactFlash can be used to insert very small CompactFlash or hard drive devices (e.g., matchbox-sized 320-MByte hard drive) directly onto a peripheral card. Depending upon the type of HBA, there is typically a connection point on the card for attaching a fiber optic or copper duplex cable. If fiber optic connection is provided, there may be a gigabit interface converter (GBIC) as well. The HBA may have LED status lights to indicate power and port activity, similar to the status lights on a modem or network hub. As of summer 2001, speeds up to 2 gigabits/second were possible, and most PCI-based HBA devices supported 32- or 64-bit addressing. There has been a trend toward adding larger buffers to increase performance. Although PCI is a widespread standard for peripheral cards, not all HBA PCI cards support all operating systems; there are different flavors of HBAs. Multiple HBA cards may be inserted into a system, up to a vendor-specified maximum, depending upon power and configuration. HBAs are shipped with individual IEEE standard unique address identifiers. For Fibre Channel connectivity, a World Wide Name (WWN) is derived from the given IEEE address identifier to handle arbitrated loop activity. A software configuration utility may be used to establish a relationship between the HBA physical device and the logical HBA number assigned.

host carrier In telecommunications, the main carrier through which billing is channeled. In systems where a call goes through various networks or providers, carriers may have arrangements with the host carrier to bill through them to save paperwork and other administrative costs. host computer A computer in a network providing primary operations and applications that are run through clients or remote terminals at other locations. A network may have more than one host, and some hosts may be specialized for modem access, email distribution, printing, and other tasks. The term host is related more to function than raw hardware capabilities but, due to resource sharing economics, the host frequently has greater capabilities (more memory, storage, peripherals, etc.) than the clients accessing it. host site 1. A repository or other archive site accessed by remote users through client programs such as Telnet, FTP, Web browsers, and others. The host site is the one on which the administrative tasks and storage are carried out. 2. A computer bulletin board system, which typically hosts email, chats, games, and file uploads and downloads. hot 1. Connected; live; ungrounded current-carrying conductor. A term frequently applied to electrical wires. 2. A hot chip is one that either runs at a high temperature and requires cooling, or one that has a fault that causes it to emit more heat than is normal and is likely to fail soon. See heat sink. 3. Stolen. 4. Topical, popular, desired by a large following. 5. Titillating, arousing. See hot chat. hot cathode, thermionic cathode A hot cathode is one that produces a stream of electrons (a cathode ray) by means of thermionic emission. Thus, heat (thermal energy) that is associated with the cathode provides the energy boost needed to liberate the beam of electrons that comprises the cathode ray. Electrical current is used to provide the heat and replace the electrons that stream away from the cathode. New types of hot cathodes have been developed for use with electronic devices, such as the waveguide tubes used in micro- and millimeter-wave communications. Barium-dispenser thermionic cathodes have been of particular interest to researchers. These new cathodes are suitable for environments where small size and low power requirements are advantages, as in Earth-orbiting satellites and deep space probes. NASA has a facility for cathode research and development and the evaluation of new materials, called the Thermionic and Non-Thermionic Cathode Research and Development Test Facility. Thermionic cathodes are used in electronicallypulsed injectors for high energy physics research on superconductors. They have also been considered for use as electron-beam scrubbing devices, that is, the beam could be used to clean hard-to-clean surfaces for specialized industrial applications. Thermionic cathodes are also of interest in consumer applications. For example, Philips Display Components, the largest manufacturer of CRTs for computer monitors and television sets, has teams of materials

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scientists working on new generation versions and applications of cathodes. For electron beams that are significantly brighter than conventional thermionic cathodes, thermal field emission (TFE) cathodes are being developed. These high-resolution emitters can be used in electron beam testing equipment and low-accelerating scanning electron microscopes (SEMs). See cathode-ray tube. hot chat Realtime conversations on a number of public or private chat forums in which sex is frankly discussed between two or more parties. Private conversations are engaged in by using private messaging commands on public forums or by opening password-protected by-invitation private channels. See Internet Relay Chat. hot cut, flash cut The transition from one circuit to another while the system is in operation, hopefully without disruption to components or current users. Hot cuts are used when switching from an old wiring system to a new one, or when switching around physical routing paths. On individual computer systems, components are sometimes hot swapped, although it is never recommended. Never hot cut a component that is being accessed. It is especially inadvisable to hot cut most types of drives (floppy, CD-ROM, hard drive, etc.). (RAID systems are an exception.) Keyboards and mice are not usually damaged by hot cuts, but make it a habit to power off a system before making hardware configuration changes. See half tap, hot swap, redundant array of inexpensive disks. hot docking Inserting a component into a docking bay (as in laptop docks or video bays) while the system is powered on. This is generally inadvisable. Whenever possible, power off all components before connecting electrical circuits. Some newer components are being developed for use in hot docking environments, such as high-capacity disk storage systems and consumer storage devices such as USB peripheral devices that include hard drives, card readers, and graphics tablets. Hot docking is very convenient for the user as it is not necessary to close applications and power down a system to attach or swap a peripheral device. hot key combination 1. A combination of keys that when pressed simultaneously will perform a specific function or engage a memory resident program, such as a printer utility. It is handy for background processes that are frequently needed but would be distracting if running in the foreground along with other current process. 2. A combination of keys pressed simultaneously to perform a specific operating system function. For example, on an Amiga, Amiga-Amiga-Ctrl reboots the machine. On an IBM-compatible running MS-DOS, Ctrl-Alt-Del performs a similar function. 3. A combination of keys to access text style attributes and search and replace functions in older word processing programs developed before graphical user interfaces became common. hot line A private, dedicated phone connection, sometimes indicated by the color of the phone. On a land line, when you pick up the line, it either connects automatically or does so quickly through the

touch of a button or speed dialing. On a wireless service, the system may be configured so the phone can connect only with a specific number. Hot lines are used as emergency phones in buildings, on roadways, as dedicated lines to brokerage firms, or by important personnel in government or military positions. hot line service Phone service that expedites an automatic connection through a dedicated private phone. See hot line. hot links In computer software applications, virtual links that form a connection between information in one document (such as text or images) and another, even if their native formats differ. For example, in a desktop-published document, there may be a hot link to text in a word processor and another to an image in a graphics program. Depending upon the system and the software, changing text in the word processor or in the graphics program may immediately effect a change in the corresponding desktop published document, or may effect a change when the page is refreshed or when update links is selected from a menu. As systems become more capable (multitasking, faster CPUs, more memory), hot links are more prevalent and updates happen more automatically. See drag and drop. hot list In computing, a list of frequently used applications programs, directories, or Internet newsgroups, Web sites, or archives. A hot list is usually displayed as a text list or pull-down menu from which the user can quickly select the desired destination. See bookmark. hot spot, hotspot 1. A location on a touch sensitive device that alerts the software to respond in some fashion to user input. 2. A screen location that responds when a cursor is moved into the region, or if the cursor is positioned and a mouse or key clicked to activate the hot spot. 3. A bottleneck or area of congestion in a network, component, or software routine. 4. An area of a circuit in which some component is generating more heat than would normally be expected and that may signify a potential problem. 5. A region of a document or image that includes an embedded link so some further action happens if the region is selected or activated. Hyperpage applications use hot spots for various links; graphics programs sometimes use hot spots to activate palettes or specialized drawing menus. hot standby A backup or background system or program that is operating, but idle and available to take over if failure of the regular system occurs. Hot Standby Router Protocol HSRP. A protocol that provides resiliency, fault-tolerance, and transparent network topology support for network routers. Standby routers inherit the lead position if the lead router in a group fails. hot swap The process of connecting or disconnecting an electric circuit, component, or peripheral while the system is powered up. Hot swapping is done to minimize disruption to users of a system. It is highly inadvisable in most circumstances. Some systems are designed to handle hot swaps (some types of video components or redundant hard drive systems), but be sure you know what you are doing before

attempting it. See FireWire, hot cut. hot type Cast metal type used in traditional printing presses. hotel/motel console A private branch system specifically designed for businesses that manage rooms. It provides additional information on the status of the rooms or status of calls to or from those rooms. Used in convention centers, hotels, motels, private boarding homes, etc. HotJava An adjunct to Java, the widespread, objectoriented, cross-platform programming language from Sun Microsystems that continues to grow in popularity for use on the Web. HotJava is a Java-enabled Web browser with support for JDK and SSL that is installed on the local computer system and enables Web sites with Java applications to run from a desktop system. Java support enhances a browser’s capabilities. See Applets, Java. hotline See hot line. Hotline Virtual Private Line Service A commercial Nynex subscriber service that uses public lines specially programmed and configured to operate as though they were private dedicated lines, with the connection activated when picking up the handset. See hot line. House, Royal E. An American inventor who developed one of the first practical direct paper tape printing telegraphic receivers, patented in 1846. House continued to improve upon the original design and patented the improved version in 1852. See House telegraph. House telegraph The House telegraph (U.S. #4,464) was a relatively complex printing telegraph. Two people were required to operate it, as one had to turn a crank to run the mechanism while the other operated the telegraph. It had a wooden base with the circuitry mounted on the top and a piano-keyboard-like series of keys underneath a hinged flap. The message was printed on a strip of paper similar to the stock ticker machines that evolved out of printing telegraphs. The House telegraph is said to have been capable of transmitting up to 40 words per minute and was in common use in the U.S. in the latter half of the 1800s. The House telegraph formed part of the inspiration for the subsequent Phelps Combination Printer telegraph, designed by George Phelps to improve upon the House and Hughes telegraph systems. See House, Royal E.; Hughes telegraph; Phelps Combination Printer; telegraph, printing. housing A protective enclosure commonly used to insulate, protect, or manage wires or electrical connections. Many housings are shaped like boxes, with one side open to provide access. Splice enclosures are a particular type of housing used to connect fiber optic cables between the head end and the node. howl An irritating, unwanted wailing or screeching sound from acoustic or electric feedback that may occur, for example, when a speaker and microphone from the same transmission are placed too close together. Noise and echo canceling equipment can prevent or reduce howling.

howler, howler tone In telephone communications, a unit that creates a loud sound to signal that a phone has been left off-hook. For example, on some public exchanges, a recording will play first if a phone is left off-hook, “If you’d like to make a call, please hang up and try again ...,” followed by a series of raucous beeps that can be heard up to about 15 feet from the phone. HP See Hewlett-Packard. HP 9830 Historically, one of the earliest desktop computers, coming out a few months after the Kenbak-1 and at almost the same time as the Intel SIM4, in 1972. The HP 9830 was the first desktop computer to really look like modern desktops, with a typewriter-style keyboard, numeric keypad, function keys, and status lights. It can’t really be considered a personal computer, as it listed at just under $6,000 (more than the price of a car, in those days) and was primarily marketed to institutions and the scientific community, but it was compact and fullfeatured relative to programmable calculators. See Altair, Kenbak-1, Sim4. HPA See high power amplifier. HRPT high resolution picture transmission. A specialized image communication for very high resolution images such as those transmitted by imaging satellites. HSCI High-Speed Communications Interface. A single-port interface from Cisco Systems that provides full duplex synchronous serial communications. HSCS high speed circuit switched. HSD home satellite dish. HSDA high speed data access. HSDU See High Speed Data Unit. HSRP See Hot Standby Router Protocol. HST See High Speed Technology. HSV hue, saturation, value. In color imaging, HSV is a color model that allows settings to be adjusted along these three properties. Hue is the color, saturation is the amount or richness of the color, and value is the lightness or darkness. HSV systems for adjusting palettes on computer desktops, applications, and graphics programs are common. HTL See high-threshold logic. HTTP See Hypertext Transfer Protocol. HTTPS See Secure Hypertext Transfer Protocol. hub Focal point, center of attachment or activity. hub, network 1. A connecting point on a network to centralize wiring and connection management. A hub may be passive or active and is often used in systems with star topologies. 2. A connection box on video or audio systems that permits centralization of cables and easy reconfiguration of devices. Often used in connection with switchers and, in many cases, the switcher itself may double as a hub. See bridge, router, switcher. hub site The location of a hub, which may vary from a small box on a desk or rack to an entire closet or room, depending upon the size of the system. The hub site allows easy cabling and administrative

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access to a variety of connections. Hubs are often located at main wiring or logical junctions and may connect to external systems. hue A color of the visible spectrum. Hue does not include white, black, or shades of gray, which are the presence of all colors (white) or absence of color (black) in various intensities (grays). Most people are familiar with hues as the colors of the rainbow: red, orange, yellow, green, blue, indigo, violet. In software, hue may also be called tone or tint. See intensity, saturation. Huffman encoding Huffman is a fast, variablelength, tree-oriented encoding scheme developed in the early 1950s by David Huffman. It optimizes on the basis of more frequently occurring characters in order to achieve compression in fewer bits. Since it produces a coding table that can be reused for additional image encodings, it is efficient for certain types of multi-image applications, though not especially efficient for very short messages (due to header overhead). Data corruption on a small scale can significantly affect the content of a message when decoded, so Huffman is best used with robust transmissions protocols with built-in error-checking. JPEG image compression is based, in part, on Huffman encoding. Modified Huffman (MH) is widely used in facsimile transmissions. Hughes, David E. (1831-1900) An English-born American music teacher who developed one of the first printing telegraphs, in essence the telegram and later teletype machines. The telegraph, with improvements by George Phelps, formed the basis of the American Telegraph Company, in competition with Western Union. In 1858, Hughes returned to Europe to demonstrate and promote the system and remained there as a resident. Hughes also invented the carbon microphone, in 1877, an important contribution to telephony. See House, Royal; Hughes telegraph; Morse, Samuel F.B.; Phelps, George; telegram. Hughes, David R. A West Point graduate and retired U.S. Army Colonel, Hughes has been acknowledged as a pioneer in internetworking and educational applications in distance learning. He is credited with teaching the first online college credit courses (1983). He further designed and supported the Big Sky Telegraph network and the Montana state METNET. Hughes Network Systems A company (actually a group of companies under the Hughes umbrella) which has been involved in satellite communications since the early launches and has developed a number of associated innovative technologies. One such product is DirecPC, which allows a satellite feed to connect with a personal computer for data communications. See Applications Technology Network Program, DirecPC. Hughes telegraph The Hughes telegraph began as an idea for transcribing music and ended up as a printing telegraph that used a tone to synchronize the mechanism between the transmitting and receiving printers. It was developed by David E. Hughes at about the same time the House printing telegraph was being marketed commercially and was patented in 1856 (U.S. #14,917).

Power to the Hughes telegraph was provided by a weight-driven clock system, similar to a grandfather clock, thus making it possible for a single operator to use the system, as opposed to two operators for the competing House telegraph. The essential designs of the House and Hughes systems was the same, a wood cabinet equipped with a piano-style alphabetic keyboard and the various mechanisms mounted on top of the cabinet. They differed mainly in detail and in the way they were powered. The mechanism was not perfect and needed some refinement to be commercially successful, but there was a demand for telegraph machines at the time, and the rights were purchased by a newly forming company called the American Telegraph Company. ATC turned to George Phelps to improve the system, a move that made the Hughes telegraph moderately successful in North America and highly successful in Europe after Hughes traveled there to demonstrate the system, beginning in 1858. The Hughes printing telegraph enjoyed a long working life of more than a century in some European locations. In North America, the House and Hughes telegraphs led to improved designs that were highly successful and comprised early teletype machines. See House telegraph; Hughes, David E.; Phelps Combination Printer. Hull, Albert Wallace (1880-1966) An American physicist who made important contributions to X-ray crystallography and who developed a number of types of electron tubes, including the magnetron, a tube capable of generating microwave frequencies. Hull published a description of magnetron technology in 1921 in the AIEE Journal, V.40. The magnetron became important in the development of radar and satellite communications systems. See magnetron. Human Computer Interface standards HCI. A series of protocol platform standards from the IETF, including but not limited to Common Desktop Environment (CDE), Complex Text Layout (CTL), Motif, etc. Hunnings, Henry (1843-1886) A British clergyman and inventor who developed a carbon granule-based hearing aid in 1878, which replaced the electric hearing aid developed by Alexander Graham Bell in 1876. Hunnings also applied the carbon granule technology to improve upon microphones invented by Thomas Edison. Hunnings’ improvements led to sturdy devices with better sensitivity. Similar carbon granule technology was also developed by Francis Blake, Jr., to improve telephone transmissions, and both Blake and Hunnings telephones were prevalent at the time. hunt, hunting A process through which a call is routed by seeking the best path or first available path or device. hunt group In telephone systems, a series of lines set up so calls can be assigned to the next available line in a group if the first accessed line is busy. There are different ways to organize hunt groups, from a straight sequential hunt to random hunts. Hush-a-Phone decision A landmark communica-

tions case in 1956 which challenged the AT&T monopoly of phone line access. The company marketing Hush-a-Phone Company and Harry C. Tuttle wanted to attach a mechanical device to a phone set in order to screen out background noise. AT&T argued against it, supported by the Federal Communications Commission (FCC), but the decision was later overturned in the court of appeals, the main arguments including the mechanical rather than electrical nature of the device and the fact that it in no way harmed the phone equipment. A Hush-aPhone is on exhibit at the Museum of Independent Telephony in Abilene, Kansas. See Carterfone decision. HUT Hopkins Ultraviolet Telescope. See ultraviolet. HW hardware. HW-16 A three-band radio transmitter and receiver housed together in one case, by Heathkit. The transmitter was crystal-controlled and the device was electron-tube based, with the exception of one transistor component. It was popular with novice amateur radio operators in the late 1960s and early 1970s. The unit could be upgraded as the radio operator learned more and received an operator’s license. Sockets on the front panel enabled crystals to be inserted. The HW-16 was most effective over the 40- and 80-meter bands and can still be used over those frequencies. Hybrid Fiber Coax HFC. A transmission system combining fiber optic cable with coaxial cable that can handle simultaneous analog and digital signals. It is less expensive than a full fiber or switched digital video installation but still provides greater bandwidth than traditional technologies built entirely on copper wire or coaxial. Network technologies such as ATM, SONET, and frame relay can be transmitted over HFC. Discrete wavelet multitone (DWMT) is being proposed as a suitable modulation scheme for existing HFC installations. See discrete wavelet multitone, Hybrid Fiber Coax architecture, SONET. Hybrid Fiber Coax architecture A hybrid fiber coax technology for carrying video or telephone services, or a combination of both. For video, the bandwidth is typically divided into channels which can further be subdivided into phone lines. It is primarily a downstream technology, which serves broadcast TV very well, but it may not be as flexible for interactive TV and phone services. The downstream nature is not inherent in the cable, but rather in the transmission and amplification technology. Typically optical fiber runs from the central office to a node servicing an area neighborhood. From that point, the signal can be converted to be carried via coaxial cables to individual subscribers. At the subscriber point, a device splits the video and telephone signals so they can be directed to the appropriate lines or devices within the premises. This hybrid system balances some of the speed and bandwidth of a full fiber-based system, with some of the economic advantages of coaxial servicing individual neighborhoods. One disadvantage is that there is not an unlimited amount of bandwidth available for phone lines, and phone service must be planned and adjusted as needed. HFC technologies

can put cable companies in a position to compete with telephone providers, which may create a shift in future market share. See Hybrid Fiber Coax. hydraw See octopus. hydroelectric Electrical power derived from the energy provided by rapidly moving water or channeled water under pressure. Large dam projects are usually linked to a desire for hydroelectric power for residential, urban, and industrial purposes. hydrolysis A process of chemical decomposition that occurs in the presence of moisture. Hydrolysis is of concern in maintaining insulating materials in underwater cable installations. hydrometer An instrument that measures, by displacement, the specific gravities of liquids. Used, for example, to measure the electrolytes in batteries. hygroscope An instrument for measuring the amount of moisture in a material. Handheld paper hygroscopes are commonly used in the printing industry to monitor paper moisture balance and the relative humidity of the air in order to adjust printing materials and processes for quality control. See densitometer. hygroscopic 1. A material with a tendency to absorb and retain moisture. 2. A material that is able to absorb and retain moisture. Hyper III The first fully radio remote-controlled research vehicle of the U.S. aeronautical/space program, flown once in December 1969. Leading up to the Hyper III were a number of small lifting body models built by Dale Reed and droptested from a radio-controlled mothership.

NASA engineer Dale Reed holding the M2-F1 model in front of the full-scale version of the craft. Reed had created a number of shapes of lifting bodies droptested in the late 1960s, leading up to the testing of the Hyper III in 1969. [NASA/Dryden image detail, March 1967.]

The Hyper III was based upon studies of hypersonic, cross-range reentry vehicles. With some modifications, it became a tubular 32-foot dacron, aluminum,

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and fiberglass craft that utilized two model airplane receivers for controlling hydraulics and telemetry. It could transmit 12 channels of telemetry signals and informational data to the ground station.

Top: Researchers at the NASA (Dryden) Flight Research Center (FRC) display radio-controlled aerial vehicles, with the Hyper III at the top. Shown left to right are Eldredge, Reed, and Newman (Bob McDonald is not shown). Other models include M2F2 research craft. Bottom: The Hyper III was a pioneer test vehicle constructed for about $6,500 (about a year’s wages at the time). [NASA/Dryden image details, 1968 and 1969.]

The Hyper III established the feasibility of remotelypiloted vehicles for a range of uses and fostered a continued interest in this area. While interest didn’t stop, the bulkiness of the electronics and programming limitations kept these types of vehicle largely experimental until twenty years later. Then, with the size and price of electronics steadily dropping, interest in remotely-piloted craft and even autonomous craft picked up significantly in many areas of space research and military reconnaissance. This was especially true in the late 1990s, when the widening gap in price between building and operating fullscale planes and remote aircraft became a strong incentive for pursuing remote-controlled vehicle applications.

hyperfiction A type of computerized fictional narrative incorporating a multiple-option story line that can be interactively selected by the reader. Hypertext links to words and images within the narrative allow the user to follow different text threads, such as alternate endings, or to find out more about a particular character or the story environment. In other words, different readers have a different experience of reading the story, since they may read different parts of it or read parts of it in a different order from another reader with different preferences. In hyperfiction, the story essentially exists as a database, with the different scenarios referenced so they can be selectively accessed. When the database is interactively read, it perceptually unfolds for the reader as a story. See hypertext, hyperlink. hyperlink, hypertext link A logical link between meaningful data organized within a random access database or markup language. Hyperlinks can be hierarchical or flat. They can be one-directional or bidirectional. Although hypertext links are most familiar to users in the form of virtual cards in a computer card catalog or as browser-accessible links on the World Wide Web, a hyperlink in its broadest sense also applies to interconnected visual image links, where the user clicks on an icon or a part of a picture rather than on a word or block of text. Hyperlinks on the Web have opened up global Internet interactions and cross references to immense, shared information storehouses. There are a number of popular games that are navigated through text or visual links. See browser, hypertext transfer protocol, World Wide Web. hypertext A means of accessing information through referential links. This idea has been around for a long time and has had various implementations, with Bush developing a microfilm system and suggesting associative indexing in the 1940s. In the 1960s, D. Engelbart developed the On Line System (NLS) for storing research papers and other information in a hypertext-like manner. A number of other hypertext systems have been developed by various researchers, but the implementation of the concept on computer networks did not become commonly understood and recognized until the distribution of HyperText on the Macintosh computer in the late 1980s. The most significant implementation of hypertext, which serves as a simple front-end to the Internet in the form of Web pages, is the Hypertext Markup Language. Hypertext tags can be imbedded in Web pages to allow them to connect to any other public page on the Internet. See Hypertext Markup Language. Hypertext Markup Language HTML. A simple markup language for creating platform-independent hypertext documents for display and distribution over a computer network. HTML is a generic semantics implementation of Standard Generalized Markup Language (SGML – ISO 8879:1986). HTML has a simple tag-based syntax that can be readily learned, for basic page display, by individuals without much prior programming skills. It can be readily configured to link to graphics and documents in other locations on the Web. Thus, HTML

has become widely used on the Web to represent hypermedia, documentation with inline graphics, database query results, news, stock reports, course outlines, storefronts, and discussion lists. The formal definition of HTML syntax is described in the HTML Document Type Definition (DTD). HTML was designed by Tim Berners-Lee at CERN and has been in use since 1990 by the World Wide Web global information initiative. The Document Type Definition (DTD) was written by Dan Connolly in 1992. In 1993 a number of contributors provided enhancements, and the incorporation of NCSA Mosaic software allowed the inclusion of inline graphics. Dave Raggett derived forms material from the HTML+ specification.

HTML is a simple tag-based markup language that enables pages with graphics and text to be described and displayed on the World Wide Web with an HTMLcompatible Web browser. The language enables links to be established to other sites and Internet archives and, when enhanced with other languages, such as Sun’s Java, can even provide animations, streaming video, and other multimedia resources. Note that the interpretation of the HTML tags will vary from browser to browser. Line breaks, paragraph spacings, etc. are generally not specifically described in the markup tags. This facilitates interoperability over a variety of computer platforms with different display and processing capabilities.

In 1994, the HTML Specification was rewritten by Dan Connolly and Karen Olson and edited by the HTML Working Group, with updates by Eric Schieler, Mike Knezovich, and Eric Sink from

Spyglass, Inc. Finally, the entire draft was restructured by Roy Fielding. The development and use of Web browsers began to spread. Since then, the number of users of the Web, interacting through HTML, has climbed to more than 40 million, and many millions have authored personal, institutional, and commercial Web pages using HTML. HTML has undergone a number of updates and revisions since its initial introduction. HTML pages are often enhanced with applets created with Sun’s Java programming language and may also be enhanced with ActiveX objects. See browser, hypertext, RFC 2070 (Internationalization). Hypertext Transfer Protocol HTTP. An application-level, generic, stateless, object-oriented network protocol intended for quick-access, distributed, collaborative, hypermedia systems. HTTP uses typed data representation, allowing system-independent data transfer. HTTP use is widespread, as it has been an intrinsic part of the World Wide Web initiative since 1990 and has been widely incorporated into Web servers and clients. It also provides a generic means of communication between user agents and proxies/gateways, and Internet protocols for email, search engines, and file servers. HTTP communications on the Internet are typically over TCP/IP connections, with a default port of TCP 80. A message is the basic unit of HTTP communication, which uses a request/response paradigm for serving information. Once a connection is established between the client and the server, the client sends a request, and the server responds with control and error information and, if the request is successful, the requested content. The syntax of the HTTP URL is as follows: http://:<port>/<path>?<searchpart> There are other transfer protocols as well, including File Transfer Protocol (FTP), for the transmission of files over the Web. When used with a Web browser, it has a similar syntax to an HTTP URL, except that the prefix ftp: is used rather than http:. See File Transfer Protocol, MIME, Secure HTTP. hysteresis 1. The diminution or retardation of effects upon a body from a force, when the force acting upon the body changes. For example, in a body that is magnetized by a changing magnetizing force (e.g., an electromagnet with a varying current), hysteresis is the amount by which the magnetic values of the body lag (due to friction or viscosity, etc.) behind those of the magnetizing force. 2. The difference in response of a system to a varying force or signal. 3. The difference in the ability of a system or device to respond and change according to a sudden force upon it. To give a simplified example, stomping on a car accelerator or brake does not result in an instantaneous change to a new speed. Hysteresis is the delay effect between the stomping action and the response of the vehicle to the action. Sports car drivers experience less hysteresis than motorhome drivers.

H

hysteresis curve A diagrammatic representation of a magnetizing force and its related magnetic flux. In a hysteresis curve for magnetic materials that are subjected to a magnetic influence, then separated from the influence, then magnetized and separated again, it can be seen that materials retain some of their original magnetism after removal of the magnetic influence. This property can be shown to vary among substances by means of a hysteresis curve diagram. Thus, materials with a narrow curve are suitable for the cores of electromagnets in industrial applications; those with wide curves can retain their magnetic properties and are used accordingly. hysteresis device A device or circuit intended to mediate a situation in which power levels, or other important operating aspects, are fluctuating outside of normal parameters. An example of such a device would be an emergency system that switches to reserve generators or battery power when voltages drop or which draw off extra power if voltages spike. In this case, a delay mechanism (a hysteresis device) may be deliberately introduced in order to prevent constant fluctuation or fluttering, so that the system switches to a reserve system only after a sustained or significant change in power levels occurs. Without

the hysteresis device, the system might otherwise be constantly switching back and forth between main and reserve systems, a situation that would be impractical and perhaps even dangerous. Hysteresis devices/circuits are also important in mobile communications based upon cell transmissions. In these systems, a person using a mobile phone, for example, may be traveling along a path that passes several transceiving stations. As the user moves from one transceiving region to another, the signal will change. Buildings and bridges will also affect the strength of the signal reaching the mobile unit. Mobile systems are designed to assess the incoming signals and select the best one, a situation that may change from moment to moment, especially in a moving vehicle. Whenever there is a switch from one transceiver to another, there is a slight interruption during which the system adjusts its settings. If the user is in an locality where there are several signals of similar strength, the unit could try to constantly switch from one to another, causing interruptions and inefficient use of the resources. A hysteresis circuit helps to ensure that excessive adjustments are not made. Hz See hertz.

I 1. symb. current. 2. A symbol commonly used to designate the “on” position on a rocker switch, with O commonly used for “off.” 3. abbrev. intensity. The I is usually indicated on or near an analog dial on a computer monitor or TV screen, to allow the user to increase or decrease the amount of illumination of the display.

The I and O symbols on the rocker switch on the back of this external hard drive cabinet indicate power on and power off.

I interface, Inter-Service Provider interface An interface between two Cellular Digital Packet Data (CDPD) networks deployed over AMPS. See A interface, E interface. I & R abbrev. installation and repair. I Series Recommendations A set of ITU-T recommendations that provides guidelines for ISDN. These are available as publications from the ITU-T for purchase and a few may be downloadable without charge from the Net. Some of the related general categories and specific I category recommendations that give a sense of the breadth and scope of the topics are listed here. Since ITU-T specifications and recommendations are widely followed by vendors in the telecommunications industry, those wanting to maximize interoperability with other systems need to be aware of the information disseminated by the ITU-T. See also similar listings under Q, V, and X Series Recommendations that describe other aspects of telecommunications. See ITU-T I Series Recommendations chart following. I signal One stream in a split signal in certain modulation systems. The transmission may be split into two streams: one is the in-phase or I signal; the other is the quadrature-phase or Q signal. In various data

I

transmission schemes, it is common to split a signal and to alter the characteristics of one or both of the data streams so that they can be transmitted together without interfering with one another or creating excessive crosstalk. The signals may then be recombined or synchronized at the receiving end. Streams may also be split according to their different transmissions needs, as in speech, which can be sent on voice grade lines, and graphics, which require better and wider transmissions media. When prototyping hardware transmission devices (e.g., GPS receivers), it is sometimes expedient to model the behavior of the transmission in a computer simulation before building the hardware. Thus I/Q signals and other signal schemes are simulated according to their known mathematical properties. See quadrature amplitude modulation. I-beam A common name for a video screen cursor that resembles the capital letter I, that is, a vertical line with horizontal serifs, that may also include a small horizontal tick mark in the lower middle to indicate the baseline of the characters below which the descenders will be positioned. This type of cursor is a common computer interface convention used in painting, word processing, and desktop publishing applications to aid in positioning and alignment of text. I-frame intra-coded frame. In MPEG animations, a picture that has been encoded into a video frame without reference to past or later frames, using predicted motion compensation algorithms. See B-frame, I-picture. I-picture intra-coded picture. In MPEG animations, a picture that is to be encoded into a video frame without reference to past or later frames to prevent reference image errors. Once it is encoded, it is considered to be an I-frame. See MPEG encoder. I-TV See interactive television. I-way slang. An expression for the growing global telecommunications network, derived from a shortening of the phrase “Information Super Highway.” I/O input/output. Generally used in the context of computers as meaning input from users, applications, or processes and output to devices, applications, or processes. See input, input device, output, output device.

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ITU-T I Series Recommendations I.140

1993

I.141

1988

I.150

1995

I.200

1988

I.211 I.221

1993 1993

I.470

1988

I.500

1993

I.501 I.511

1993 1988

I.515

1993

I.520

1993

I.525

1996

I.530

1993

I.555

1993

Recom.Date Description I.112 I.113

1993 1997

I.114

1993

I.230

1988

I.240 I.250

1988 1988

I.371.1 1997

I.311 I.313 I.324 I.220

1996 1997 1991 1988

I.241.8 1995 I.210

1993

I.310

1993

I.319

1992

I.330

1988

I.334

1988

I.410

1988

I.510

1993

I.601

1988

I.610

1995

I.620

1996

I.120

1993

I.121 I.122

1993 1993

I.130

1988

Vocabulary of terms for ISDNs Vocabulary of terms for broadband aspects of ISDN Vocabulary of terms for universal personal telecommunication Definition of bearer service categories Definition of teleservices Definition of supplementary services Traffic control and congestion control in B-ISDN: conformance definitions for ABT and ABR B-ISDN general network aspects B-ISDN network requirements ISDN network architecture Common dynamic description of basic telecommunication services Teleaction stage one service description Principles of telecommunication services supported by an ISDN and the means to describe them ISDN – network functional principles Principles of intelligent network architecture (also Q.1201) ISDN numbering and addressing principles Principles relating ISDN numbers/ subaddresses to the OSI reference model network layer addresses General aspects and principles relating to recommendations on ISDN user-network interfaces Definitions and general principles for ISDN interworking General maintenance principles of ISDN subscriber access and subscriber installation B-ISDN operation and maintenance principles and functions Frame Relay operation and maintenance principles and functions Integrated services digital networks (ISDNs) Broadband aspects of ISDN Framework for frame mode bearer services Method for the characterization of telecommunication services supported by an ISDN and network capabilities of an ISDN

I.570 I.571 I.580

1995

I.581

1997

Attribute technique for the characterization of telecommunication services supported by an ISDN and network capabilities of an ISDN ISDN network charging capabilities attributes B-ISDN asynchronous transfer mode functional characteristics Guidance to the I.200-series of recommendations B-ISDN service aspects Common specific characteristics of services Relationship of terminal functions to ISDN General structure of the ISDN interworking recommendations Service interworking ISDN-to-ISDN layer 1 internetwork interface Parameter exchange for ISDN interworking General arrangements for network interworking between ISDNs Interworking between networks operating at bit rates less than 64 kbps with 64 kbps-based ISDN and B-ISDN Network interworking between an ISDN and a public switched telephone network (PSTN) Frame Relaying bearer service interworking Public/private ISDN interworking Connection of VSAT-based private networks to the public ISDN General arrangements for interworking between B-ISDN and 64 kbps-based ISDN General arrangements for B-ISDN interworking

ISDN BRI and PRI I.420 I.430

1988 1995

I.421 I.431

1988 1993

Basic user-network interface Basic user-network interface – layer 1 specification Primary rate user-network interface Primary rate user-network interface – layer 1 specification

Protocols I.241.8 1995 I.320 I.321

1993 1993

Teleaction stage one service description ISDN protocol reference model B-ISDN protocol reference model and its application

ISDN – various I.325 1993 Reference configurations for ISDN connection types I.327 1993 B-ISDN functional architecture I.328 1992 Intelligent Network – Service plane architecture (also Q.1202) I.329 1992 Intelligent Network – Global functional plane architecture (also Q.1203) I.331 1997 International public telecommunication numbering plan I.333 1993 Terminal selection in ISDN I.340 1988 ISDN connection types I.350 1993 General aspects of quality of service and network performance in digital networks, including ISDNs I.351 1997 Relationships among ISDN performance recommendations I.352 1993 Network performance objectives for connection processing delays in an ISDN I.353 1996 Reference events for defining ISDN and B-ISDN performance parameters I.354 1993 Network performance objectives for packet mode communication in an ISDN I.355 1995 ISDN 64 kbps connection type availability performance I.357 1996 B-ISDN semi-permanent connection availability I.364 1995 Support of the broadband connectionless data bearer service by the B-ISDN I.370 1991 Congestion management for ISDN Frame Relaying bearer service I.371 1996 Traffic control and congestion control in B-ISDN I.372 1993 Frame Relaying bearer service network-to-network interface requirements I.373 1993 Network capabilities to support Universal Personal Telecommunication (UPT) I.374 1993 Framework recommendation on “Network capabilities to support multimedia services” I.376 1995 ISDN network capabilities for the support of the teleaction service I.411 1993 ISDN user-network interfaces – references configurations I.412 1988 ISDN user-network interfaces – interface structures and access capabilities I.413 1993 B-ISDN user-network interface I.414 1997 Overview of recommendations on layer 1 for ISDN and B-ISDN customer accesses

I.432.1 1996 B-ISDN user-network interface – physical layer specification: general characteristics I.432.2 1996 B-ISDN user-network interface – physical layer specification: 155 520 kbps and 622 080 kbps operation I.432.3 1996 B-ISDN User-Network Interface – physical layer specification: 1544 kbps and 2048 kbps operation I.432.4 1996 B-ISDN User-Network Interface – physical layer specification: 51 840 kbps operation I.432.5 1997 B-ISDN user-network interface – physical layer specification: 25 600 kbps operation

Multiplexing I.460 I.464

1988 Multiplexing, rate adaption, and support of existing interfaces 1991 Multiplexing, rate adaption, and support of existing interfaces for restricted 64 kbit/s transfer capability

ATM-related I.326 I.356 I.361 I.363 I.363.1 I.363.3 I.363.5 I.365.1 I.365.2

I.365.3

I.365.4

I.731

B-ISDN – Physical Layer Specification

I.732

I.432 1993 B-ISDN user-network interface – physical layer specification

I.751

1995 Functional architecture of transport networks based on ATM 1996 B-ISDN ATM layer cell transfer performance 1995 B-ISDN ATM layer specification 1993 B-ISDN ATM adaptation layer (AAL) specification 1996 B-ISDN ATM adaptation: type 1 AAL 1996 B-ISDN ATM adaptation layer specification: type 3/4 AAL 1996 B-ISDN ATM adaptation layer specification: type 5 AAL 1993 Frame Relaying service specific convergence sublayer (FR-SSCS) 1995 B-ISDN ATM adaptation layer sublayers: service-specific coordination function to provide the connection-oriented network service 1995 B-ISDN ATM adaptation layer sublayers: service-specific coordination function to provide the connection-oriented transport service 1996 B-ISDN ATM adaptation layer sublayers: service-specific convergence sublayer for HDLC applications 1996 Types and general characteristics of ATM equipment 1996 Functional characteristics of ATM equipment 1996 Asynchronous transfer mode management of network element view

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I/O bound input/output bound. A processor subjected to a processing load in excess of what it was designed to handle, or which causes processes and response time to be uncomfortably slow for the user, is said to be I/O bound. There are number of ways to reduce the incidence of I/O congestion: more efficient algorithms; co-processing chips for computing intensive operations such as graphics, sound, or device management to ease the load on the central processing unit (CPU); faster CPUs; reconfiguration or reorganization of peripheral devices; distributed processing over a network, etc. I/O device input/output device. A piece of computer hardware physically interfaced with a system, and electrically and logically configured to engage in two-way communication with the operating system and relevant applications. Many computing devices are primarily input or output devices. Joysticks and mice are primarily input devices; speakers and printers are primarily output devices. (Few devices are strictly one or the other, since signal processing, device status, and handshaking signals often are returned by the device to the system to improve the efficiency of their use.) Most monitors are output devices, but touchscreen monitors are used for both input and output. Keyboards are typically input devices, except for those that have small LED displays to send configuration, status, or numeric keypad calculator information to the user. See input device, output device. I/P input. i.LINK See FireWire. IA 1. See implementation agreement. 2. See intelligent agent. IAB See Internet Architecture Board. IAC 1. See Industry Advisory Council. 2. See Information Access Company. 3. See Information Analysis Center. 4. See Institute for Advanced Commerce. 5. See interactive asynchronous communications. 6. See interapplication communications. 7. See Internet Access Coalition. IAD See Integrated Access Device. IAHC See Internet International Ad Hoc Committee. IAM 1. incoming address message. 2. See initial address message. 3. intermediate access memory. IANA See Internet Assigned Numbers Authority. IAP See Internet Access Provider. IAPP See Inter-Access Point Protocol. IARL See International Amateur Radio League. IARU See International Amateur Radio Union. IBC See Integrated Broadband Communications. IBM See International Business Machines. IBM clone See IBM-compatible. IBM smaller scale computing systems A series of desktop computers has been marketed by IBM for business, educational, and home markets since the 1970s. The first models were compact but expensive, costing nearly as much as a house, and accessible only to corporations or institutions with larger budgets. However, with the success of the MITS Altair

personal computer, in 1975, and the introduction of low-cost desktop computers by other companies, it became clear that the market for computers was changing and IBM’s ballpark price and promotional campaigns had to be adjusted to compete with startup companies developing new systems. The first small-scale computer system intended by IBM to significantly exploit the new competitive market was the IBM 5110, announced in 1978. This lower cost successor to the IBM 5100 was unsuccessful in capturing popular attention, however, as it was overshadowed by the Tandy/Radio Shack TRS-80 and Apple computers and, to some extent, the Commodore PET. Thus, in the early 1980s, IBM was scrambling to capture business and home markets, as demonstrated by their release of the IBM Personal Computer and the IBM PCjr. By the mid-1980s, they had successfully recaptured a large portion of the business market, however; the home market was still showing a preference for Apple, Atari, and Commodore-Amiga computers, while the educational market was largely based on Apple computers. In the graphics industry, professionals were overwhelmingly selecting Apple Macintoshes over IBM computers due to the better graphics hardware and software available for desktop publishing and prepress. At the time, IBM computers were difficult to network and tended to be equipped with low-resolution monitors and text-based operating systems. It was not until about 1994 that IBM PCs made significant inroads in the publishing service bureau markets and, even then, companies adding IBM computers tended to hang on to Macintosh computers for large-scale printing jobs such as posters, billboards, etc., where reliable output and good printer drivers were important. Ironically, the reason IBM and IBMlicensed third party computers became better suited to the needs of the graphics sector was because of the market force for better games machines. Computer games require substantial computing resources, including more memory, faster processors, and better graphics and sound. With the exception of better sound, these are the same capabilities needed by the graphics industry, which they finally got in a roundabout way. Over time, in business markets and, eventually, home markets, IBM computers prevailed. Part of the reason for the success of IBM-based computers in the mid-1980s was IBM’s decision to license the technology to third-party manufacturers. Thus, IBM “clones” and IBM “compatibles” became prevalent in the mid-1980s, but IBM computers were preferred until about 1987, when it became clear to consumers that the quality of some of the clones was superior to IBM systems and, in many cases, less expensive. Once again, IBM had to adjust their marketing and manufacturing to compete with a market that was rapidly changing and evolving. By the late 1980s, desktop computers were beginning to supersede mainframes for many types of computing applications in spite of the insistence of diehard mainframe reps that mainframes were here

to stay. Since the mainstay of IBM up to this time had been their medium- and large-scale computers, it was important for the company to note and adjust to the increasingly important role played by microcomputers. By the mid-1990s, $1000 desktop computers were more powerful than many of the mainand miniframes sold to institutions a decade earlier for tens of thousands or millions of dollars. This remarkable trend for less expensive computers to have more and more powerful capabilities continues to this day. In chronological order, here is a brief sampling of early IBM desktop computing systems that were important (or unsuccessful) in the history of personal computers: IBM Portable Computer, IBM 5100 A larger desktop-sized computer introduced to businesses and educational institutions in September 1975. The Portable Computer came in a number of configurations, with varying amounts of memory up to 64K (a lot of memory in those days) at a cost ranging from just under $9000 to almost $20,000 (nearly the price of a house). The system was mainly of interest to engineers, financial analysts, and other professionals who could profit from faster, more advanced calculations. IBM Computing System, IBM 5110 A smallscale “affordable” computer that was transitional between high-priced desktops and mainframes, and later systems known as personal computers or microcomputers. Announced in January 1978, the 5110 was aimed at a wide portion of the business market, the market successfully penetrated by Tandy/Radio Shack Computers and the later line of IBM Personal Computers. It was available in configurations of up to 64K of memory. The 5110 never received widespread attention and market penetration, in spite of IBM’s reputation as a business computer supplier, leaving the door open for Tandy and entrepreneurial companies such as Apple, Atari, and Commodore-Amiga to capture portions of the personal computing market. This was a pivotal time for IBM in computing history because losing the desktop computer market to other companies would have a significant impact on the company’s future. Surprisingly, IBM went to a couple of young entrepreneurs to supply subsequent versions of their operating system and programming language. See Gates, William; IBM Personal Computer. IBM Personal Computer, IBM 5150 The first relatively low-cost personal computer introduced by IBM to realize significant sales to general consumers. The IBM PC was launched in 1981 to compete mainly with Tandy Radio Shack computers making big inroads in both hobbyist and business markets. Due to its better reputation for service and its licensing agreements with third parties, IBM eventually succeeded in taking the majority business market away from Tandy. Tandy did some things right: they opened a chain of computer centers to support the machines and to provide customer service. Unfortunately, their

employees were often inadequately trained in the new computing technologies (most dedicated hobbyists knew more about the TRS-80s than the customer service reps) and sometimes the employees were downright rude. Thus, consumers, especially business owners, drifted back to IBM, which had a decades-long history of dependable service policies. IBM’s success was also Microsoft’s success, as the fledgling company had been contracted to supply IBM with an operating system and BASIC language program. See Gates, William; IBM-compatible; MS-DOS. IBM PCjr An Intel 8088-based microcomputer, introduced in the early 1980s. The PCjr was intended as a low-cost home alternative to the IBM Personal Computer XT by IBM. The list price was $1300 and the computer didn’t gain the same acceptance in homes as the XT line gained in business. Home consumers tended to prefer lower cost computers or those with better graphics and sound than were available on the PCjr, choosing instead various Apple, Atari, and Radio Shack Color Computer models. IBM Personal Computer XT Extended Technology. An Intel 8088-based microcomputer, introduced in 1983. The processing speeds of the various models of XTs ranged from 4.77 to 10 MHz (turbo XTs), with 16-bit data buses. A clock/calendar chip was not standard. Microsoft BASIC was included in ROM, and the computer could use cassettes for program reads and writes. DOS 2.1 was optional, but was needed in order to read and write floppy disk drives. As it was being configured and marketed in 1984, a typical 32-pound XT was listed at about $4000 without monitor and about $5000 with color monitor, graphics adapter card, and DOS 2.1. Although very limited in its graphics and sound capabilities, the XT computer was aimed at and accepted by the business market. Tandy/Radio Shack had lost its dominant installed base or almost 80% of the market, a position it never regained. IBM Personal Computer AT Advanced Technology. An Intel 80286-based 16-bit microcomputer, introduced in the fall of 1984 by IBM as an updated alternative to the IBM XT. The processing speed of the AT was 6 MHz, with 256 kilobytes of memory. It came configured with a 1.2MByte floppy drive, but the 20-MByte hard disk, graphics adapter, and monitor were optional. A clock/calendar chip was built in. The base AT system was listed at $4000, but the price with an extra 512 kilobytes of RAM, a hard disk, color graphics card, and monochrome monitor brought the total up to $6700. The hefty price tag was part of the reason why competing vendors were able to get a foothold in the industry. The cost of an AT was about the cost of a new car. At the same time as the AT computer was released with PC DOS 3.0, IBM announced two additional products: a multitasking, windowing operating system called Topview, which could run existing

I

MS-DOS 1.0 and 2.0 programs; and PC Network, a broadband local area network (LAN), to accompany its Personal Computer line of products. See IBM-compatible. IBM Token-Ring See Token-Ring. IBM-compatible A de facto marketing term used by various companies to promote a desktop computer incorporating licensed Intel-based International Business Machines (IBM) technology to the extent that most, or virtually all software compatible with IBM personal computers would run on the thirdparty IBM-compatible machines. When IBM originally began licensing their technology to third-party manufacturers, vendors and users made a distinction between IBM-compatibles and IBM clones to distinguish between machines that were mostly compatible, and those which were virtually compatible or “identical” in their ability to use various vendors’ hardware and software. Since the late 1980s, the distinction between compatibles and clones has disappeared, since few machines now are not completely compatible, and compatible has now taken on the connotation that used to be reserved for clone. International Business Machines may not be happy with the IBM name being associated with products from other vendors, and likely would prefer that they be called IBM-licensed rather than IBM-compatible, but the term took hold and continues to be widely used. IBN Institut Belge de Normalisation. A Belgian standards body of the Minister of Economic Affairs, located in Brussels. It is also involved in certification and accreditation activities. IBN is associated with the Comité Européen de Normalisation (CEN) and ISO. http://www.ibn.be/ IBS 1. See intelligent battery system. 2. See Intelsat Business Service. IC 1. See integrated circuit. 2. See intercom. 3. interexchange carrier. See Inter Exchange Carrier. 4. intermediate cross-connect. iCalendar, iCal An Internet calendaring and scheduling core object specification submitted as a Standards Track document by Dawson and Stenerson in 1998. The iCalendar spec is intended to provide a foundation for developing and deploying interoperable calendaring and scheduling services over the Internet. Since a number of different proprietary products from commercial vendors were beginning to be extended for use over the Net, a need was seen for defining a common format for the exchange of calendar and schedule information. Group or personal information managers may exchange information through the MIME content type defined in the specification. As a result of interest in this most basic and common type of application for Internet use, the Internet Engineering Task Force (IETF) initiated a calendaring and scheduling working group (CALSCH). Other protocols with a direct relationship to iCalendar interoperability have been defined, most of them arising from discussions of the CALSCH. CALSCH not only described and submitted

specification drafts, but also administered interoperability testing. The work of CALSCH has also come to the attention of working groups developing separate but somewhat related protocols and formats, including the IPTEL working group. Calendar Access Protocol CAL. A draft CALSCH calendar access/management protocol described in 2001 by Mansour, Royer, and Babics. CAL describes the messages to be handled and a realtime binding for messages. Calendar User Agents (CUAs) facilitate request/response access to iCalendar-based databases, called Calendar Stores (CSs). The specification describes how to create, modify, delete, and query iCalendar components. CAP Realtime iTIP-Based Scheduling Profile CRISP. A draft profile submitted by J. Stracke in 2000. CRISP is a subset of CAP that does not support non-iTIP operations. The two are not mutually exclusive and may be implemented together to provide various options for access, efficiency, security, etc. iCalendar Message-Based Interoperability Protocol iMIP. A Standards Track protocol specification described by Dawson, Mansour, and Silverberg in 1998. The specification details a message binding from the iCalendar TransportIndependent Interoperability Protocol (iTIP) to Internet email-based transports for calendaring and scheduling data. Content information as a MIME entity is referenced as a “text/calendar” content type. Security may be achieved through MIME Security Multiparts. See RFC 822, RFC 2045, RFC 2447. iCalendar Realtime Interoperability Protocol iRIP. A draft CALSCH realtime interoperability protocol described by Courtemanche, Mansour, and O’Leary in 1999. iRIP binds to iTIP to extend its messaging capabilities to those that are session-based (as opposed to iTIP alone, which is email-based). iCalendar Transport-Independent Interoperability Protocol iTIP. A Standards Track protocol specification described by Silverberg et al., in 1998. The specification details how calendaring and scheduling systems use iCalendar objects for enabling interoperability among applications data sets. It is defined independently of the particular transport used to transmit the schedule information in order to support a variety of methods of communication. The spec outlines a model for the exchange of both static and dynamic event objects. The protocol provides group scheduling semantics applicable to common calendar systems. iTIP relates to application protocol format. See RFC 2446. The iCalendar spec is based on an earlier vCalendar specification and has been further described in UML by Michael Arick as to its components, properties, and parameters related to the properties. In 1999, Mahoney and Taler submitted a draft of the Implementors’ Guide to Internet Calendaring to aid in

understanding the iCalendar effort and the relationships of the different protocols to facilitate the creation of conformant applications. Progress towards a final embodiment dragged somewhat and the specification gained in complexity over time. Market-sensitive vendors began to be wary not only of the complexity but also of the time it was taking for the effort to solidify. CALSCH members eventually acknowledged that it might be best to simplify the project and denote some areas of iCalendar implementation as optional rather than mandatory, a move that sparked some renewed interest. See RFC 2445. iCAL A Web-based commercial software calendar/ scheduling utility available in personal and professional editions. Demo versions may be downloaded free from the Web. Ical An X-based calendar/scheduling program developed by Sanjay Ghemawat. Version 2.0 was released in 1995. C++ Source code may be downloaded from the Web and through FTP. ICAL See Internet Community at Large (natural history collections project). ICALEP International Conference on Accelerator

and Large Experimental Physics. ICANN See Internet Corporation for Assigned Names and Numbers. iCAP A quantitative, patent-pending software-driven process for transcribing a person’s education, skills, and experience into a multilevel numerical expression of “intellectual capital,” developed by ICSC. This is intended to provide a means for employees and employers to assess the needs of a position and the potential candidates through a system of standardized iCAP codes archived in an iCAP Catalog. Development and maintenance of the iCAP Catalog is the responsibility of the International Intellectual Capital Codes Association (IICCA). ICSC is expected to promote the ICAP system to employees, employment agencies, corporations, and anyone else seeking to match a job with potential candidates. (With computer networks spreading and society speeding up, the objectification of human traits may become prevalent, with the data accessible via the Internet – perhaps through licensing or subscription services – and thus the basic ideas warrant additional comment.) This type of project is administratively extensive and

IBM Personal Computer XT System Specifications Category

Item

Notes

Processor:

Intel 8088

4.77 MHz with socket for 8087 math coprocessor

Memory:

40 kilobytes ROM

256 kbyte RAM up to a maximum of 640 kilobytes

Storage:

10 Mbyte fixed hard disk

one 360-kbyte double-sided 5 1/4" floppy (additional floppy drives were $425)

Expansion:

5 empty expansion slots

3 slots used by floppy drive, hard disk, and serial adapter

Display:

monochrome/color

monitor optional monochrome ($275) color ($680), color required additional graphics adapter ($250)

Software:

Microsoft BASIC

optional DOS 2.1 ($65)

IBM Personal Computer AT System Specifications Category

Item

Notes

Processor:

Intel 80286

6 MHz with socket for 8087 math coprocessor

Memory:

40 kilobytes ROM

256 kbyte RAM up to a maximum of 3 Mbytes

Storage:

one 1.2-Mbyte 5 1/4" floppy 5 1/4" 360-kbyte floppy drive optional 20-Mbyte hard drive optional

Expansion:

5 empty expansion slots

3 slots used by floppy drive, hard disk, and serial adapter

Display:

monochrome/color

monitor and graphics adapter optional

Software:

IBM PC BASIC

PC DOS 3.0, available options included DOS 3.1 and XENIX

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ongoing and touches on issues of privacy and reduction of people into numbers. Vendors need to take into consideration these issues. In this example, skills must be quantified and confirmed (since job applicants may misrepresent themselves under pressure of seeking work) and updated regularly, as applicants gain job experience, life experience, and education. The income from the sale of data sets or searches would have to be sufficient to support the maintenance and verification of the database or there would be a temptation to cut corners on accuracy and privacy. It is important to recognize the difference between accumulated life skills and the subset of specific job skills. Job seekers often find that mentioning only skills directly relevant to a particular position increases the chance of being hired. Those with multiple skill areas may not fit the system unless multiple job profiles are permitted, a difficult adjustment in the absence of details related to a specific employment position. If a market develops for this type of database, the vendor with a flexible system who provides quality assurances may have the competitive advantage, especially if individuals represented in the database could use the Internet to check the information or to update it, assuming safeguards against skills misrepresentation are put in place. ICAPI 1. International Call Control API. 2. See Interface Control Application Programming Interface. ICB Individual Case Basis. Client requests that are individually handled because they are not satisfied by standard products or services. ICCB See Internet Configuration Control Board. ICCC See Internet Channel Commerce Connectivity Protocol. ICCF 1. See Interexchange Carrier Compatibility Forum. 2. International Civic Communication Forum. A nongovernmental organization (NGGO) in the Ukraine, somewhat analogous to a nonprofit organization, that is assisting in providing guidelines for the establishment of further NGOs as democratic institutions. 3. See International Correspondence Chess Federation. ICEA See Insulated Cable Engineers Association, Inc. ICELAN 2000 A commercial software automation control system developed by IEC. It is a graphical network management and control product to provide support and control over LONWorks nodes and applications. Based on Peak Components, this Windows-based software enables LONWorks users to install, maintain, schedule, and configure LONWorks networks. See LONWorks. ICI See Interexchange Carrier Interface. ICIA See Information and Communications Industry Association, Ltd. ICM See Integrated Call Management. ICMP See Internet Control Message Protocol. ICO Global Communications See New ICO. iCOMP Intel Comparative Microprocessor Performance index. A simplified means of evaluating and

expressing relative microprocessor power, introduced by Intel in 1992. Intel, as a major vendor of microprocessing chips, sought a straightforward way to convey processor information to purchasers. The iCOMP is an index rather than a benchmark in a technical sense, as it narrowly describes instruction execution speed (not clock speed). Benchmarks involve sophisticated and careful evaluation of many performance factors, whereas an index is a basic indicator, in this case, a compilation based on four industry-standard benchmarks, without taking into consideration other aspects of the system architecture, including video display, device addressing, etc. iCOMP is expressed on a comparative scale, which uses the instruction speed of the 25 MHz 486SX processor as a baseline, assigning it a value of 100, with subsequent processors rated relative to this. icon 1. Pictorial representation, symbolic image, emblem. 2. In telecommunications documents and applications, a symbolic image, usually small and abbreviated, representing an object, program, state, or task. Visually similar iconic representations are sometimes used to show different aspects or states of the same thing, such as a ghosted icon to show something is in use or an iconized version of an application symbol to show something is loaded and available. Icons are used extensively in documentation and graphical user interfaces (GUIs) to represent concepts or contents. Some are specific to an application or platform, but some are common enough to be recognized across a variety of systems, e.g., folder icons to represent directories. ICONET A satellite communications network being established by ICO Global Communications. See New ICO. ICONTEC Instituto Colombiano de Normas Técnicas. A Columbian technical standards body. ICTA 1. Idaho Cable Telecommunications Association. 2. Indiana Cable Telecommunications Association. 3. See Independent Cable & Telecommunications Association. 4. See International Center for Technology Assessment. 5. International Christian Technologists’ Association. 6. See International Commission on Technology and Accessibility. 7. International Conference on Technology and Aging. ID 1. identification, identifier. 2. See input device. 3. See integrated dispatch. 4. intermediate device. IDA 1. See integrated data access. 2. integrated digital access. Digital systems intended to facilitate access to networks and/or application or information sources. The phrase is usually used with reference to systems where a number of features have been integrated into one easily used unit, such as a portable scheduler with a built-in wireless modem. 3. intelligent drive array. See RAID. IDAI See Accessible Information on Development Activities. IDCMA Independent Data Communications Manufacturers Association. An independent trade organization representing the interests of independent communications manufacturers. The IDCMA has spoken out on some of the FCC-related rulings regarding

new technologies that may or may not be considered as customer premises equipment. IDE See integrated development environment. IDE devices and controllers Integrated Drive Electronics. A control mechanism and format for computer hard disk drive devices developed in 1986 by Compaq and Western Digital. IDE provides data transfer rates of about 1 to 3 Mbytes per second, depending upon other system factors, including the data bus. On common Intel-based microcomputers, the IDE uses an interrupt interface to the operating system. IDE has been highly competitive with the SCSI standard, another very common drive format. To get the production costs down, and because many Intelbased computers in the early 1980s did not come standard with controllers for extra peripherals, the IDE controller mechanism was incorporated into the drive. Each controller can handle two drives, a “master” and a “slave” (compared with seven, including controller, for SCSI). IDE is more limited than SCSI (fewer devices can be chained, smaller addressable space, IRQs necessary, not compatible with RAID systems, etc.), but it is also less expensive and has become widely established. In order to overcome some of its limitations, a number of enhanced IDE formats now exist. Most workstations and Motorola-based desktop computers (Suns, SGIs, Amigas, most Apple Macintoshes, NeXTs, and others) include SCSI controllers on the basic machine, making it unnecessary to purchase a separate drive controller to add SCSI peripheral devices to the computer. Some of the newer Macintosh and PowerMac computers support both SCSI and IDE. Most Intel-based desktop computers come with IDE controllers on the basic machine and SCSI controllers can be purchased as options. See hard disk drive, SCSI. IDEA See International Data Encryption Algorithm. iDEN integrated Digital Enhanced Network. Digital phone technology developed and marketed by Motorola for workgroups. The phones may be used like two-way radios over a cellular network, thus overcoming the distance limitations of conventional portable two-way radios while also offering other services such as phone, messaging, and data transmissions. Fax and Internet access capabilities are also provided on data-ready iDEN units. The system is based on the concept of multiple workgroups communicating within a private virtual network that is part of a larger common infrastructure. See Enhanced Specialized Mobile Radio. IDEN integrated digital electronic network. identifier ID 1. In database management, a keyword used to locate information, or a category of information. 2. In programming, a variable name, extension, prefix, suffix, or other device to provide a means to easily recognize an element, or distinguish it from others. IDev See input device. IDF intermediate distribution frame. See distribution frame.

IDL See Interface Design Language. IDLC See Integrated Digital Loop Carrier. idle In a state of readiness, but not currently activated. Idle is often used as a power-saving measure, and may be a state in which only minimal power is used by the system until full power is needed, as in laptops that power-down the monitor and hard drives when they are not in active use. idle channel code A repeated signal that identifies a channel that is available, but not currently in active use. See idle. idle channel noise Noise in a communications channel that can be heard or occurs when no transmissions are active. For example, low level hums can often be heard in phone lines when no one is talking, but are not noticed when talking continues. idle line cutoff In computer networks, it is not uncommon for Internet Services Providers (ISPs) or network administrators to set the system to log off any clients (machines or applications) that are inactive for longer than a specified period of time (e.g., 15 minutes). This frees up abandoned terminals or modem lines that are no longer in use. idle signal 1. In networking, a channel which is open and ready, and which may be sending an idle signal, but through which no active or significant transmissions are occurring. 2. Any signal in a circuit intended to signify that no significant transmission is currently in progress. An administrative tool to allow potential users, operators, or operating software to detect available lines and put them into use, or to compile and record usage statistics for further evaluation and tuning of a system. See idle channel code. IDML See International Development Markup Language. IDML Initiative A collaborative initiative to improve global information exchange using XML in an international context through use of a standardized International Development Markup Language (IDML). http://www.idmlinitiative.org/ IDN See Integrated Digital Network. IDSCP See Initial Defense Communications Satellite Program. IDTV See Improved Definition Television. IDU See Interface Data Unit. IEC 1. See Inter Exchange Carrier. 2. See International Electrotechnical Commission. 3. See International Engineering Consortium. IEEE Institute of Electrical and Electronic Engineers, Inc. The world’s largest electrical, electronics, and computer engineering/computer science technical professional society, founded in 1963 from a merger of the American Institute of Electrical Engineers (AIEE) and the Institute of Radio Engineers (IRE). IEEE is a respected and influential organization that serves about a quarter of a million professionals and students in almost 200 countries. IEEE’s activities are broad-reaching, including standardssetting, publications, conferences, historical preservation and study, and much more. See American Institute of Electrical Engineers, IEEE Standards Association, Institute of Radio Engineers, Organizationally

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Unique Identifier. http://www.ieee.org/ IEEE Canada Institute of Electrical and Electronic Engineers of Canada. The Canadian arm of the wellknown IEEE, organized across the country into groups based on geographic regions. http://www.ieee.ca/ IEEE History Center The historical archive of the IEEE, including about 300 artifacts and a number of oral histories. The IEEE includes among its early members some of the pioneer inventors in the telecommunications field, including Thomas Edison and Nikola Tesla. It works in cooperation with the IEEE library in which IEEE publications are stored. See IEEE IEEE Standards Association IEEE-SA. An international organization serving individual and corporate members with a portfolio of standards programs. IEEE-SA focuses on full consensus standards processes as well as innovative policies for standards development. It is affiliated with the IEEE and is empowered to formulate and promote international engineering standards to further globally beneficial applications of technology. Membership in IEEE-SA is not necessarily a requirement to participate in a standards working group. See IEEE. IEEE 802.11 Standard for wireless local area networks (LANs) adopted in June 1997. IEN See Internet Experimental Note. IES, IESNA See Illuminating Engineering Society of North America. IETF See Internet Engineering Task Force. IF intermediate frequency. IFax device An Internet-interfaced device capable of sending and/or receiving Internet facsimiles through existing Internet mail mechanisms as defined in RFC 822 and RFC 1123. In general, IFax formats must be MIME compliant. IFax devices can also be used as gateways between the Internet and G3Fax (traditional) phone-based facsimile machines, with the IFax configured to handle the connection and dialup and any authentication necessary to prevent undue cost or unauthorized use. An IFax device can serve as a mail transfer agent (MTA) for one or more G3Fax devices. In general, Simple Mail Transfer Protocol (SMTP) should be used for such applications, although dedicated servers may use POP or IMAP. The IFax specification was developed by the IETF Fax Working Group and described as a Standards Track comment in 1998. See facsimile formats, G3Fax, TIFF-FX, RFC 2305. IFCM See independent flow control message. IFD See image file directory. IFIP See International Federation for Information Processing. IFRB See International Frequency Registration Board. IFWP See International Forum on the White Paper. IGC intelligent graphics controller. IGMP See Internet Group Multicast Protocol. ignition Lighting, kindling, applying a spark so as

to inflame or provide sufficient heat or current to set off a chain of events. IGP See Interior Gateway Protocol. IGRP See Interior Gateway Routing Protocol. IGT Ispettorato Generale delle Telcomunicazioni. General Inspectorate of Telecommunications in Italy. IGY International Geophysical Year. IIA 1. See Information Industry Association. 2. See Irish Internet Association. IICA See International Intellectual Capital Codes Association. IIIA 1. See Integrated Internet Information Architecture. 2. See International Internet Industrial Association. 3. See Internet Information Infrastructure Architecture. IIR Interactive Information Response. IIOP Internet Inter-ORB Protocol. A wire-level communications protocol. See CORBA, Object Request Broker. IISP 1. See Information Infrastructure Standards Panel. 2. Interim Interswitch Signaling Protocol. A basic call routing scheme which does not automatically handle link failures; routing tables established by the network administrator are used instead. IITC Information Infrastructure Task Force. IJCAI International Joint Conferences on Artificial Intelligence. An international biennial forum (in odd-numbered years) held since 1969. http://ijcai.org/ ILEC See Incumbent Local Exchange Carrier. ILLIAC I A historic large-scale computer introduced in 1952 by the University of Illinois. It consisted of vacuum-tube technology and performed 11,000 arithmetical operations per second. See ENIAC, MANIAC. ILLIAC II The successor to the ILLIAC I, the ILLIAC II was introduced in 1963. It was based upon transistor and diode technology and could perform up to 500,000 operations per second. ILLIAC III The ILLIAC III was introduced in 1966. It was designed to process nonarithmetical data, and so was a departure from ILLIAC II, a special purpose machine. ILLIAC IV Based on the new semiconductor technology, the ILLIAC IV was introduced in the early 1970s. It was logically designed after the Westinghouse Electric Corporation’s SOLOMON computers developed in the early 1960s. The ILLIAC IV consisted of a battery of 64 processors which could execute from 100 million to 200 million instructions per second. It was significant not only for its speed, but also for the ability of its multiple processors to perform simultaneous computations. The services of the ILLIAC IV were made available to other institutions through high-speed phone line timesharing. Illuminating Engineering Society of North America IES, IESNA. A leading technical authority on illumination. For almost a century, the IESNA has been providing expertise on lighting practices through programs, publications, and services. Members include engineers, educators, scientists,

manufacturers, and utility services personnel. http://www.iesna.org/ ILMI See Interim Link Management Interface. IM intermodulation distortion. A type of audio distortion that occurs when multiple tones interfere with one another in a way that is not harmonically related to the original tones. IMA Interactive Multimedia Association of Malaysia. Information about this standards-setting organization is available on the Web. http://www1.jaring.my/cornerstone/ima/about.htm IMAC See Isochronous Media Access Control. image antenna A hypothetical antenna, used for mathematical modeling, defined as a mirror-image of an above-ground antenna, located below the ground symmetric to the surface, at the same distance as the actual antenna is above the surface. image file directory IFD. A data file structure providing location information for image data in the form of image information and data pointers. In a TIFF raster image file, for example, the IFD is an ordered sequence of tagged fields that begins on a word boundary somewhere after the header data. As more than one raster image may be in a TIFF file (as in a multi-page document or document with different versions of the same image), there can be more than one IFD. Multiple IFDs can be organized as tree structures or as linked lists. See TIFF. imagesetter A professional-level graphics and type imaging machine, an imagesetter is similar to a high quality computer printer. Imagesetters are used in service bureaus, and traditional and digital printing houses, to create the image or the color separations used to control the ink distribution on the press. Typical resolution on these industrial quality machines is 1200 dpi to 2700 dpi (compared to 300 to 800 for most consumer machines) and they print on paper or film, or both. While the distinction between consumer printers and imagesetters is blurring, with consumer printers now able to print up to 1200 dpi, there are still technical differences between commercial and consumer machines which are important to design, desktop publishing, and printing professionals. Imagesetters do more than just print at higher resolutions; they also include more sophisticated and precise algorithms for halftone screens, may include higher quality fonts, may be able to print on special papers and even directly on aluminum, asbestosbased, or other more robust printing plate media. In addition, the distribution of the imaging materials on the printing medium is typically more precise and even. Further, a professional quality imagesetter has better alignment for subsequent printouts. When printing color separations, especially for fouror five-color process printing, the consistency of the printing from one separation to the next is extremely important to the outcome of the final color printout, especially at resolutions of 175 lines or higher used in calendars, posters, and art prints. In modern digital presses, the trend is to eliminate the separate imagesetter and incorporate the technology

into the press itself. In the past, a computer file or traditionally photographed image was taken to a paper or metal plate through an imagesetter and, from there, the physical plate was attached to the press in order to create the printing job. Now it is possible to put a file on a floppy disk or cartridge and have the digital image sent directly to the press without the intermediary steps. It is even possible for a four-, five-, or six-color print job to be printed in one press run, rather than sending each color through the press in a separate pass, and aligning the plates each time. This new technology is revolutionizing the printing industry and eliminating a lot of intermediary steps and jobs in the process. IMAP See Internet Messaging Access Protocol. IMASS Intelligent Multiple Access Spectrum Sharing. IMAX “I” – eye + maximum. An advanced cinematic system with large film reels to accommodate oversized frames that provide startling detail when displayed on large IMAX projection screens. The system was introduced in 1960 by Canadian inventor W. C. Shaw. IMC See Interagency Management Council. IMHO Abbreviation for “in my humble opinion” commonly used in memos and online correspondence, where facial and tonal expressions are not available to soften the sense of words that may seem harsher than they are intended in print. See emoticons, IMO, IMNSHO. Immediate Ringing A telephone or private branch system option in which there is no delay between the time of the reception of a call and the ringing of the telephone itself. Favored by those who want to provide quick responses to calls, such as emergency and crisis lines and certain businesses. Immunity from Suit A legal agreement in which a license holder agrees not to sue the provider of a product or service. Microsoft and certain other large vendors are alleged to be asking for immunity from suit from some of their clients. In the author’s opinion, purchasers should avoid signing any licenses that sanction neglect or mismanufacture on the part of the provider and should never sign anything that conflicts with constitutional rights or is coercive. Read license agreements carefully, especially the small print, and question and renegotiate anything that gives cause for concern. IMNSHO An abbreviation for “in my not so humble opinion” used in memos and online correspondence to emphasize a point somewhat satirically. See emoticons, IMHO. IMO Abbreviation for “in my opinion,” which is used in memos and online correspondence, where facial and tonal expressions are not available to soften the sense of words that may seem harsher in print than intended. See emoticons, IMHO. impact printer Any printer which uses physical movement of a platen, pin, daisywheel, or other printing mechanism to transfer ink or toner to the printing medium. Common impact printers include dot matrix printers, daisywheel printers, and computerized typewriters. Impact printers tend to be noisy, and

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many offices have purchased sound hoods to fit over their printers to reduce noise levels. They also are usually limited to printing in one color at a time. Graphics and fonts are limited on impact printers. Daisywheel printers cannot print graphics beyond what might be possible with special daisy heads and a different head is needed to print each typestyle, making it impractical to mix a lot of fonts in a single document. Newer 24-pin dot matrix printers can print a variety of fonts and limited graphics, but usually a lot of effort is needed on the part of the user to exploit these capabilities. Impact printers were very prevalent in the 1970s and early 1980s, but since then many competing technologies have been developed which are quieter, faster, and more flexible, including laser, inkjet, thermal wax, and dye sublimation printers. Impact printers are still the most practical solution for documents which require carbon copies, typically invoices, work orders, and other business-related forms. Most impact printers can create up to about four to six copies before the impression is too faint to be useful. See dot matrix printer. impact tool See punchdown tool. IMPATT impact avalanche and transit time. IMPDU See Initial MAC Protocol Data Unit. impedance (symb. – Z) The total opposition, measured in ohms, offered by a circuit to the flow of alternating current (AC) at a given frequency. The ratio, in ohms, of the potential difference across a circuit to the current moving through that circuit. Design and insulating materials can substantially affect the level of impedance in a data cable, with low impedance cables generally costing more, but providing less noise and interference, and sometimes longer transmission distances. See admittance. impedance bridge A device for measuring in ohms the impedance (combined resistance and reactance) of a portion of a circuit. impedance compensator An electrical line which affects another circuit in such a way that the combination provides a desired consistent level across a specified frequency range. A compensator is used to minimize fluctuations and distortion. impedance triangle A diagrammatic model for describing an impedance relationship. Imagine a right triangle with the sides respectively representing resistance and reactance, which change proportional to one another, and the hypotenuse representing impedance as related to the amount of the resistance and reactance combined. implementation agreement IA. A generally agreedupon means of describing a technology so that it can be put into production and/or commercial use. In order to support interoperability with global networks, many trade organization have adopted IAs as a means to standardize interfaces, protocols, and other network-related architectures and equipment in order to be able to produce commercially viable products. These IAs often become de facto standards or are integrated into the standards-development process of major standards-ratifying organizations. See Frame Relay Implementation Agreements.

import 1. Bring in from another source, region, or country. 3. Bring in from a non-native file format, protocol, or transmissions source. import, file In software applications, to import is to bring in data from another program, file, or transmissions source, usually in a non-native file format. This is usually done through an applications filter or through drag-and-drop capabilities. In drag-and-drop imports, the program will either maintain links to the original imported file or convert the format to one consistent with the program into which it is imported. import filter Many word processing, desktop publishing, and graphics programs have import filters, plugins, or modules which allow a number of file formats to be brought into an application and then saved in the native format of the application, or exported in the original format or a new one. This provides better compatibility between programs developed by different vendors. See export; import, file. import script 1. A script which controls the assembly of a document by selectively importing information as specified. Often used in spreadsheets and databases. 2. A very handy feature of database software in which you can set up a form letter, and then have the script selectively build dozens or hundreds of personalized letters in a few minutes by automatically drawing in names, addresses, and variables from a database to merge with the form letter. Bulk mail companies often use import scripts to personalize letters, contest offerings, and envelopes. 3. In programming, an import script can set up documents or source code by selectively merging modules such as header files, modular routines, Unix “man” pages, etc. imposition An important stage in printing layout during which the position and order of the elements or pages are planned in order to determine where on the printing sheet they will be located. For example, if you are printing an eight-page 5.5 x 8.5 in. booklet that is going to be saddle-stapled, you will probably be using 8.5 x 11 in. sheets of paper folded in half. Thus, the first sheet of paper will be printed with pages one and eight on one side, and pages two and seven on the other side. Setting up the masters so that the pages work out correctly is called imposition. Fortunately, many desktop publishing products now do imposition automatically, assembling the pages in the right order for booklets, or books with specific signatures in blocks of 16 or 32 pages. In some types of printing, the positioning of elements is called stripping or stripping in. See signature. Improved Definition Television IDTV. A picture broadcast and display system that provides better picture quality than conventional NTSC standards by incorporating field store techniques in the receiving circuitry. For example, the signal can be de-interlaced prior to display to reduce flicker. The originating signal is not changed. Improved Mobile Telephone Service IMTS. Early mobile phone services were set up on systems based on large antenna transceivers with limited coverage and public operator-assisted broadcast services. The system had little flexibility or privacy, but it served

as a forerunner for IMTS, in which the subscriber could place the calls directly; this in turn developed into current cellular systems where a larger number of smaller, automated transceiver systems allowed broader geographic coverage. IMPS See Infinite Monkey Protocol Suite. impulse 1. A nonrepetitive pulse so short as to be mathematically insignificant. 2. A very short nonrepetitive pulse which may not seem significant by itself, but which may impede transmission of the affected line or signal. Data transmissions are more sensitive to impulse interference than voice communications. 3. The uncontrolled desire to run out and get the latest techie toy, even though you don’t really need it. Cell phones, faster computers, and scanners often fall into this category. IMSAI 8080 An early 8080A-based microcomputer that used the MITS-developed Altair bus (S-100 bus); it was, in a sense, the first microcomputer clone. The 8080A was an enhanced version of the 8008 used on the first Altair. The IMSAI was introduced in 1975 by IMSAI Manufacturing with ads that compared it competitively against the Altair. It featured 4 kilobytes of RAM, 22 expansion slots, and, like the Altair, a front panel with LEDs and switches. IMSAI licensed Microsoft BASIC, the same program which Microsoft had first developed to run on the Altair, to the surprise of MITS, which had incorrectly assumed it had bought exclusive rights to the Altair BASIC language. See Altair. IMSI See International Mobile Subscriber Identity. IMTC The International Multimedia Teleconferencing Consortium. Their Web site includes information. http://www.imtc.org/ IMTS See Improved Mobile Telephone Service. IMUX See Inverse Multiplexer. IMW See Intelligent Music Workstation. in-band A transmissions scheme in which control and data signals are sent together over the same set of wires, or over the same frequencies, sometimes more or less simultaneously and sometimes interspersed with one another. in-band signaling A type of signaling which is incorporated together with the data being transmitted. This is found, for example, in systems which encode signaling codes along with voice transmissions on the same wires (commonly copper twisted pair). Inband signaling has advantages and disadvantages. It doesn’t require a separate set of wires to send control signals and thus is less expensive, but it does require more sophisticated handling of data and signals and has a higher potential for slowdown, errors, interference, or fraud. In-band phone systems are at greater risk for security breaches and unauthorized use of services, because users can send in-band signals over the voice line and control certain telephone functions with illegal control devices such as blue boxes. Newer out-of-band phone systems, based for example on Signaling System 7 (SS7), make unauthorized use through control signals on the transmissions line impossible, and these types of networks are increas-

ing in prevalence as older equipment is replaced by newer networks. See ISDN, Signaling System 7. in-line device A hardware device, commonly a peripheral which can be interposed between two other devices without interfering with the operation of the other devices, or intended to interface between two other devices to perform its function (and may or may not change the functioning of the other devices). Daisy-chainable devices are a type of in-line device, though not all in-line devices can be daisy-chained. See daisy chain. INA See Information Network Architecture. INC international carrier. incandescent lamp A common type of illuminating bulb developed by Thomas Edison, originally consisting of a carbonized filament in a glass globe from which the air had been removed. However, the carbon tended to blacken the inside of the bulb and other solutions were sought, with tungsten coming into general use because of its high melting point. Experimentation with the internal environment of the bulb also resulted in the discovery that various gases could alter the glow or extend bulb life. INCC Internal Network Control Center incidence angle The angle between the trajectory of an emission or ray of light and the perpendicular to a surface in the path of the emission. incipient failure A failure from degradation of a process or equipment in its early stages. inclination 1. The angle of a surface or vector in relation to an associated horizontal. 2. A deviation of a surface or vector from horizontal or vertical. incoherent scattering 1. A behavior of light in some circumstances whereby the phase of the light is random and unpredictable, as in LEDs. 2. A disordered scattering of transmission waves, such as radio, when they encounter a surface and are deflected. incoming address message IAM. See initial address message. increment 1. n. A small change in value. 2. v. To add to an existing quantity, as in a software programming loop. Incrementing an integer counter in a procedure is a very common way to keep track of quantities, operations, timing, and events. Although technically a negative value can be incremented, in programming this is usually called decremented. incremental sensitivity A measure of the least amount of change that can be detected by a specific instrument or process. incremental service delivery ISD. The delivery of a service in stages, as the user develops a need for more or different services. Many industries are “bootstrapped” this way to allow users to become accustomed to a technology at a low cost or at a beginner’s expertise level while providing a means to “move up” when there is a need for next-level or enhanced services. Incumbent Local Exchange Carrier, Independent Local Exchange Carrier ILEC. Sometimes called dominant carriers, ILECs comprise the RBOCs, independent phone companies, GTE, and others. See Competitive Local Exchange Carrier.

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Incumbent Local Exchange Carrier duties The Federal Communications Commission (FCC) stipulates a number of duties, in addition to the Local Exchange Carrier duties, in the Telecommunications Act of 1996 as shown in the FCC-Defined Duties of Incumbent Local Exchange Carriers chart. Independent Cable & Telecommunications Association ICTA. A national, Washington, D.C.-based independent trade organization supporting private and alternate cable and telecommunications systems providers. ICTA members provide video programming and other services to residents of multiple dwelling units, primarily through shared tenant services (STSs), although a trend toward geographic clusters has been recently seen. Customers served by these services include apartment, condominium, and co-op dwellers, as well as motels, college campuses, and prisons. independent flow control message IFCM. In Switch-to-Switch Protocol (SSP), the IFCM is transmitted as a 16-byte information message header of type 0x21 separate from the control message header. index An organizational tool that provides a key to other types of information, or a larger body of information, stored elsewhere. Indexing is an extremely important aspect of database design, search, and retrieval. It provides a hook or jumping off point, a brief means of indicating the subsequent location of a hierarchy or list. An index in its broadest sense can point to records, further indexes, keywords, locations, sequences, arrays, and much more. An index can comprise numbers, symbols, or lexical mnemonics, depending upon the context of the application. Some indexes are seen by the user and set manually; others are transparent to the user and set by the software. Databases, mass storage directory structures, and file hierarchies are typically indexed in one way or another for quick storage and retrieval. An index is intended as a shortlist of what is contained in the database. It is a means of describing in brief what related information is held where in order to enhance the speed with which the related information can be found. The efficiency of an indexing system depends upon the the type of index used, the quantity of information being indexed, the overall structure of the database, and the types of information sought and retrieved from the system. If a system involves a small amount of data and a complex indexing system, then it is not likely to be efficient. If, on the other hand, a large amount of data can be relatively objectively categorized, based on objective information or good guesses as to what types of information will be sought, then an indexed structure is one way to store and utilize the information. See database. index counter A very common form of feedback that allows a user or technician to monitor usage, or elapsed time or distance. Index counters and their electronic counterparts are found on tape drives, VCRs, microwaves, cars (odometers), photocopiers, and almost any appliance in which the location of information or tracking of usage for billing purposes is desired. Counters that give a rough estimate of the

number of users who have visited a Web site, or at least the number of accesses to a particular page. index of refraction The ratio of the speeds of radiating waves or particles in two different materials, as when light passes through a vacuum, air, a mirror, a gem, or a liquid. Index of refraction is of interest to scientists and engineers, of course, but it is also important to computer artists, as it is one of the mathematical values entered into ray tracing programs to influence the surface appearance of rendered forms. indicator light A light which signals a transmission, a fault condition, readiness, or other state that requires attention. Indicator lights are common on appliances, modems, surge suppressors, hard drives, etc. indirect addressing A common method in computer programming for creating a cross reference to additional related data. Since much of computer data storage cannot be determined in advance, indirect addressing makes it possible to use small segments of memory, or noncontiguous memory, hard drive space, etc. by creating pointers, directories, and other links to the main body of information. indirect light Light that is not self-emitted, but rather is reflected from another source. For example, the moon does not generate light on its own, but reflects light from the sun. INDIX See International Network for Development Information Exchange. Indo-European Telegraph Company The company that successfully installed a wire communications circuit all the way from London to Calcutta, in 1884. The feat was largely inspired by the successful laying of the transatlantic telegraph cable two decades earlier. indoor antenna A compact antenna intended to be used in areas where there are strong broadcast signals and not a lot of space (or where a large antenna would disrupt the aesthetics of a work or living area). Since broadcast waves are impeded by obstacles and larger antennas tend to pull signals better than smaller ones (there are exceptions based on the frequency range and design of the antenna), indoor antennas are somewhat limited by size and location, yet may improve reception enough to be worthwhile. Television-top rabbit ears and UHF fan dipole antennas are two examples of compact antennas that can improve indoor reception. See antenna, UHF antenna, VHF antenna. induced Produced by the influence of an electric current or a magnetic field, usually by proximity. inductance (symb. – L) The property of a material (generally in a circuit) to tend to resist change in the flow of electromagnetic current, resulting in changing lines of force. This tendency occurs where there is a flow of alternating current (AC) moving through a conductive material. The term is used specifically with reference to alternating current, as direct current (DC) does not exhibit the same alternate changes. Higher inductance values are generally associated with higher impedance values. Inductance is typically expressed in henries (H) or microhenries (µH).

FCC-Defined Duties of Incumbent Local Exchange Carriers (LECs) As defined in the Telecommunications Act of 1996:

“In addition to the duties contained in subsection (b), each incumbent local exchange carrier has the following duties: ‘(1)

DUTY TO NEGOTIATE- The duty to negotiate in good faith in accordance with section 252 the particular terms and conditions of agreements to fulfill the duties described in paragraphs (1) through (5) of subsection (b) and this subsection. The requesting telecommunications carrier also has the duty to negotiate in good faith the terms and conditions of such agreements.

‘(2)

INTERCONNECTION- The duty to provide, for the facilities and equipment of any requesting telecommunications carrier, interconnection with the local exchange carrier’s network— ‘(A) for the transmission and routing of telephone exchange service and exchange access; ‘(B) at any technically feasible point within the carrier’s network; ‘(C) that is at least equal in quality to that provided by the local exchange carrier to itself or to any subsidiary, affiliate, or any other party to which the carrier provides interconnection; and ‘(D) on rates, terms, and conditions that are just, reasonable, and nondiscriminatory, in accordance with the terms and conditions of the agreement and the requirements of this section and section 252.

‘(3)

UNBUNDLED ACCESS- The duty to provide, to any requesting telecommunications carrier for the provision of a telecommunications service, nondiscriminatory access to network elements on an unbundled basis at any technically feasible point on rates, terms, and conditions that are just, reasonable, and nondiscriminatory in accordance with the terms and conditions of the agreement and the requirements of this section and section 252. An incumbent local exchange carrier shall provide such unbundled network elements in a manner that allows requesting carriers to combine such elements in order to provide such telecommunications service.

‘(4)

RESALE- The duty— ‘(A) to offer for resale at wholesale rates any telecommunications service that the carrier provides at retail to subscribers who are not telecommunications carriers; and ‘(B) not to prohibit, and not to impose unreasonable or discriminatory conditions or limitations on, the resale of such telecommunications service, except that a State commission may, consistent with regulations prescribed by the Commission under this section, prohibit a reseller that obtains at wholesale rates a telecommunications service that is available at retail only to a category of subscribers from offering such service to a different category of subscribers.

‘(5)

NOTICE OF CHANGES- The duty to provide reasonable public notice of changes in the information necessary for the transmission and routing of services using that local exchange carrier’s facilities or networks, as well as of any other changes that would affect the interoperability of those facilities and networks.

‘(6)

COLLOCATION- The duty to provide, on rates, terms, and conditions that are just, reasonable, and nondiscriminatory, for physical collocation of equipment necessary for interconnection or access to unbundled network elements at the premises of the local exchange carrier, except that the carrier may provide for virtual collocation if the local exchange carrier demonstrates to the State commission that physical collocation is not practical for technical reasons or because of space limitations.”

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A basic inductor can be created by winding a conducting wire, such as copper, into a coil. An understanding of the properties of inductance was a very important step in the development of induction coils. These could be devised to generate high-voltage charges, and thus a source of electricity. Phone lines have been optimized over the decades for the cost-effective delivery of basic voice communications and were not designed for the specific electrical needs of data communications. Electrical surges, EMI interference, balun noise, and other problems can interfere with data delivery and slow down transfer speeds or even cause the line to be dropped. Thus, high-inductance noise filters are marketed to dialup modem users to process the electrical signals and improve data transmissions. Heat-resistant, low-inductance power cables are increasingly available for telecommunications applications. These may be constructed in various ways, but PVC-insulated stranded, annealed, tinned copper wires are common. See induction, induction coil, resistance. inductance analyzer A device for testing inductors and coils in telecommunications devices, switching power supplies, filter circuits, and similar products. Inductance analyzers typically test in a wide range of programmable frequencies and may include additional impedance, capacitance, and DC resistance testing capabilities. Automatic calibration and internal memory for storing and recalling settings and test setups may also be included (calibration kits may also be sold separately). Newer models may support several impedance settings in order to compare test results with those from older test sets and may include a serial or other standard interface for downloading settings to a computer system for storage and analysis. The understanding of inductance and the use of test equipment for troubleshooting is an important part of courses for telecommunications technicians and generally involves about 30 hours of class instruction. See crosstalk, induction. inductance bridge A diagnostic circuit configuration instrument that enables comparison of an unknown with a known inductance, similar to the concept used in a Wheatstone bridge. See Wheatstone bridge. induction, electromagnetic An electric charge or magnetic field in a material resulting from the influence of a proximate electric current or magnetic field. In a circuit, induction may be deliberately created or may result from undesired influences from nearby circuits or electromagnetic components. In computer circuits, especially those tightly integrated on a single chip, induction can be an important hindrance or limitation that must be taken into consideration in the chip’s design and fabrication. Since it is difficult to build hundreds (or thousands) of prototype chips in order to test or measure the induction properties of a particular design, computer modeling programs have been developed to simulate the induction characteristics of prototype

circuits. Sequence’s Columbus-RF, for example, is a patent-pending technology for modeling resistance, capacitance, and inductance of chip circuitry. On a larger scale, in structured cable systems, data cables that are very near to voice cables may generate undesired noise in the voice lines, partly through induction. See crosstalk, far end crosstalk, inductance, induction coil, near end crosstalk. induction, logical A reasoning process in which general principles or overall concepts are derived by discerning patterns or relationships among individual or particular observations. The modeling of induction through heuristic problem-solving algorithms is of interest in robotics, artificial intelligence, and intelligent discovery and search procedures in advanced database systems. Inductive reasoning has applications for data mining on the Internet and might specifically be applied to discerning patterns in user inquiries that could be used to anticipate future queries or general needs. It can also be used to try to anticipate the needs of handicapped telecommunications product users based on overall observations of their patterns of use. induction coil A historic electrical device that played an important role in early electronics inventions. It was a significant provider of high voltage current for many decades, and led to the creation of transformers for converting between alternating and direct current. It also led to various induction-based frequency converters. Today, induction coils are still used to offset capacitance in long communications wirelines. A basic induction coil was created in 1836 and described the next year in The Annals of Electricity by Nicholas J. Callan. It consisted of a horseshoe-shaped bar of iron, wound with many feet of thick copper wire, and hundreds of feet of thin iron wire. By interrupting the primary circuit with a contact breaker, Callan could induce a charge sufficient to power an arc light. A year after Callan published his findings, an American, Charles Grafton Page, created an induction coil. See loading coil. induction field In a transmitting antenna, a region associated with the antenna in which changing electromagnetic lines of force are active as current flows through the device. In long wireline installations, a field that is deliberately generated in order to offset capacitance. See induction coil, loading coil. induction frequency converter A mechanicallypowered induction device connected to a source of fixed frequency current that utilizes secondary circuits to deliver a frequency proportionate in speed to the magnetic field. In its most general sense, frequency conversion has become a very important part of communications technology. The conversion of frequencies allows signals to be carried over a variety of media with different transmission characteristics, and further enables signals to be shifted so that incoming and outgoing signals are less likely to interfere with one another. inductive connection, inductive pickup An electromagnetic connection between two devices or objects without direct electrical contact. The commu-

nication between the devices occurs from an electromagnetic influence through proximity to the changing electromagnetic lines of force. Some types of diagnostic tools use inductance to monitor or observe circuits without physically contacting the line. A number of surveillance devices also use this method for bugging a line, in order to avoid detection. Regulations to protect privacy prohibit the unauthorized monitoring of communications through inductive surveillance devices. Fiber optic transmissions are immune to inductive pickup as the transmission of signals through light does not have the same characteristics as electricity of extending beyond the medium through which it is traveling. See wiretap. inductive coupling The transfer of energy between two circuits that are close together, but not directly electrically connected. Thus, the interaction of the electromagnetic lines of force associated with the interaction of the circuits causes the transfer. The transfer may also occur due to self-inductance of each of the circuits (direct coupling). The transfer of energy may be desirable or undesirable. Unshielded or minimally shielded conducting wires that are too close together may create unwanted noise and interference through inductance. inductive post A conducting bolt, screw, or post associated with a waveguide that provides inductive susceptance to allow tuning of the waveguide. It is usually mounted across the waveguide, parallel to the E field. See E field, waveguide. inductive tuning In electronic devices such as radio tuners, a means of adjusting the tuning by moving a core in and out of a coil within which it is contained. The core is not in direct contact with the coil, but reacts to the changes in the electromagnetic field associated with the coil by inductance. inductor A passive component that provides power or power-related electromagnetic energy or energy control, traditionally called a coil. An inductor is able to “store” energy and to resist electromagnetic changes associated with the flow of current. Inductors come in a wide variety of types and are used in many aspects of telecommunications circuitry. Variations in the core material, the shape of the coil, and the number of windings will influence an inductor’s properties. Tables listing tolerance codes have been standardized for inductors. For example, a tolerance code of K signifies ±10% tolerance. Inductors are categorized in a number of ways: by their specific function (e.g., suppression), by their types of cores, or by their general size (e.g., miniature inductors for microelectronics). Inductor types include suppression, VHF, ring core, air core, laminated core, and many more. Suppression conductors are typically ferrite wound with enamelled or tinned copper wire all sealed with resin and/or a plastic sheath. The ferrite substance is chosen for having good magnetic properties, commonly manganese or nickel and zinc. Air core conductors have the winding built over a nonconductive core, commonly ceramic. See inductance, induction.

inductor, axial This inductor style is built with a central core and concentric leads on either end of the core. The core may be constructed from a variety of conductive materials. Axial conductors are used in power and radio frequency (RF) applications. inductor, air core An inductor with a core with no magnetic properties (e.g., ceramic) that is used as the base or support for the conductive winding. Air cores are used in situations where low loss and low inductance are desired, as in high-frequency applications. Industrial, Scientific, and Medical ISM. A set of segments of electromagnetic frequencies which do not require licensing by the Federal Communications Commission (FCC), excluding telecommunications applications. Typical ISM applications include particle acceleration, vibration generation, heating, ultrasound equipment, microwave ovens, humidifiers, etc. Class A ISM refers to industrial environments and Class B ISM is intended for domestic environments. In Canada, ISM is addressed by ICES 001. ISM equipment operators are required by the FCC to “take appropriate measures to correct” interference to radio services unless those services are operating in the ISM frequency band. The conduction and fieldstrength limits for interference are dependent upon the equipment generating the radio frequencies and the specific frequency bands being used. Commonlyused frequencies are in the 902- to 928-MHz and 2.4- to 2.4835-GHz ranges, but there are others. An important growth area in ISM unlicensed frequencies is spread spectrum and frequency-hopping technology for local area wireless networks (LAWNs) for data communications. By the late 1990s, vendors had developed scalable high-speed ISM-frequency wireless networks that they felt would comply with all the FCC ISM regulations. With important approvals by the FCC beginning about 1999, the systems began to be put into commercial production. There is also a high degree of correspondence between ISM and designated amateur radio bands, which sometimes causes problems for ham radio operators, especially given the recent increase in wireless consumer communications devices. These issues are being evaluated and debated by the ARRL and the FCC as the demand for radio frequency resources increases. Industry Advisory Council IAC. A national trade organization representing information technology (IT) professionals who provide products and services to government agencies in the U.S. The IAC also serves as a liaison between the IT industry and the Federation of Government Information Processing Councils (FGIPC). http://www.iaconline.org/ Industry Canada A Canadian federal agency responsible for the protection of intellectual property and the allocation of licenses for use of radio frequencies. Formerly the Department of Communications. See Canadian Radio Television and Telecommunications Commission. Industry Canada Emergency Telecommunications Branch A service department of Industry

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Canada that provides support for crisis situations. It administrates and liaises with a wide variety of communications and disaster departments and external organizations, including emergency broadcasting, priority access, emergency response coordination, and more. Several emergency and planning committees and working groups further the aims of the ETB. Working groups include the United Nations Working Group on Emergency Telecommunications (WGET), the Long-Distance Emergency Telecommunications Working Group, and the Wireless E-911 Working Group. http://spectrum.ic.gc.ca/urgent/ Industry Circuit Topography Act ICTA. A Canadian Act intended to protect integrated circuit topographies. See Semiconductor Chip Protection Act. Industry Standard Architecture ISA. Formerly, a very common input/output bus architecture on International Business Machines and licensed third party computers developed originally on the IBM XT models, and carried through to later models. Originally it was an 8-bit architecture, but was upgraded to 16-bit. The expansion slots inside a computer have to follow a standard format so various manufacturers can create compatible peripheral cards. ISA was one of the common types of slots found in personal computers until the mid-1990s when it was superseded by Peripheral Component Interconnect (PCI), Video Electronic Standard Association (VESA), Extended Industry Standard Architecture (EISA) and others. See Extended Industry Standard Architecture, Peripheral Component Interconnect. INGECEP See Integrated Next Generation Electronic Commerce Environment Project. INETPhone A data telephone service connected and handled through the Internet, thus substituting the Internet for the long-distance segment of a phone call in a way that is transparent to the users. See RFC 1789. Infinite Monkey Protocol Suite IMPS. A protocol suite to support an infinite number of monkeys sitting at an infinite number of typewriters in order to determine when they have produced either the entire works of Shakespeare or a good TV show. IMPS includes communications and control protocols for monkeys and organizations that interact with them. The protocol specifies how monkey transcripts may be collected, transferred, and reviewed for historical accuracy or innovation and provides a basic communications framework for normal monkey maintenance. If you haven’t figured it out already, this protocol suite was submitted and released as RFC 2795 with a date of 1 April 2000. It has been a tradition in RFC history that April 1 RFCs be of a more creative character than the usual RFC documents. Infobahn colloq. The Information (Super) Highway, based on the German word bahn. The Information Superhighway is also colloquially called the I-way. See Information Super Highway. Information Access Company IAC. A commercial electronic vendor of information purchased by the Thomson Corporation from Ziff Communications for almost half a billion dollars. The company is of

interest because it is one of the firms being watched by intellectual property rights advocates and writers to assess the accountability of firms that distribute electronic information. A concern is that the rights of writers be supported and companies track and compensate the contributors fairly. Information Analysis Center IAC. An interagency intelligence center located in the U.S. Embassy in Mexico City to assist the U.S. Ambassador to Mexico to collect and process intelligence for use by U.S. and cooperating Mexican law enforcement personnel. The information is collected and stored in electronic databases. Information and Communications Industry Association, Ltd. ICIA. A U.K. trade association supporting information and service providers and operators, and hardware and software developers, especially those involved in electronic publishing and data distribution. Founded in 1978, ICIA evolved from the Videotex Industries Association. http://www.icia.org Information and Software Industry Association ISIA. A trade association promoting the recognition, profitability, and standards of the information and software industry in Hong Kong, founded in July 1999. ISIA promotes awareness and use of information technologies, and represents and safeguards the interests of its members. It further promotes cooperation between Hong Kong and mainland China. http://www.isia.org.hk/ information content provider This is defined in the Telecommunications Act of 1996, and published by the Federal Communications Commission (FCC), as “... any person or entity that is responsible, in whole or in part, for the creation or development of information provided through the Internet or any other interactive computer service.” Information Industry Association IIA. A U.S. trade association established to support businesses that develop and deliver innovative information products and services to a global marketplace, founded in 1968. The IIA represented its members in government matters, as well, providing input to the Federal Communications Commission (FCC) and the Federal Trade Commission (FTC). In 1999, IIA merged with the Software Publishers Association to form the Software & Information Industry Association. See Software & Information Industry Association. Information Industry Association, Australian AIIA. A trade organization representing and promoting the information industry in support of the Australian economy. AIIA represents its members in government policy, promotes the value and applications of Australian information technologies, and provides educational and networking support to its members. http://www.aiia.com.au/ Information Infrastructure Standards Panel IISP. A national voluntary standards support panel established to facilitate the development of standards important to the Global Information Infrastructure (GII) and the U.S. National Information Infrastructure (NII). IISP promotes cross-sector efforts to identify,

highlight, and resolve major standards issues, a mission that was approved in November 1997. http://www.ansi.org/public/iisp Information Network Architecture INA. In the mid-1980s, Bell Communications Research began building its Intelligent Network (IN) to provide a broader range of telephone services and support for data transmission over traditional phone lines. From this grew Advanced Intelligent Networks (AIN), and then Information Network Architecture (INA) with its improved broadband support. There is some discussion as to whether INA will succeed or coexist with AIN, as AIN will meet the needs of many users for some time, considering the lag that exists between the time a new technology is introduced and when it is generally adopted by consumers. Information Security Exploratory Committee ISEC. A committee tasked with the study and support of private sector information security. The ISEC was hosted by the Information Technology Industry Council. information service This is defined in the Telecommunications Act of 1996 and published by the Federal Communications Commission (FCC), as meaning “... the offering of a capability for generating, acquiring, storing, transforming, processing, retrieving, utilizing, or making available information via telecommunications, and includes electronic publishing, but does not include any use of any such capability for the management, control, or operation of a telecommunications system or the management of a telecommunications service.” See Federal Communications Commission, Telecommunications Act of 1996. Information Service Industry Association of China CISA. A trade organization representing the Chinese information industry. CISA aids its members in creating and maximizing their competitive business strategies. CISA promotes the application of information technology (IT) in business, government, education, and individual market settings. http://www.cisanet.org.tw/ Information Services Association, Japan JISA. A nonprofit trade organization representing Japan’s information technology (IT) services industry. Founded in 1984, JISA evolved from two organizations, the Japan Software Industry Association and the Japan Information Processing Center Association. JISA cooperates with the World Information Technology and Services Alliance (WITSA) and the Asian-Oceanian Computing Industry Organization (ASOCIO). http://www.jisa.or.jp/ Information Superhighway A catchphrase promoted by U.S. government representatives, particularly Al Gore of the Clinton administration, and the press, for the domestic and global communications infrastructure. See National Information Infrastructure. Information Systems Auditability and Control Association ISACA. A global not-for-profit trade association of more than 17,000 information system

(IS) professionals providing education, training, and certification support. http://www.isaca.org/ Information System Security Association ISSA. A not-for-profit international trade organization supporting the interests of information security (IS) professionals. ISSA supports communication among members, educational activities, and information security publications. ISSA is a founding contributor to the International Information Systems Security Certification Consortium (ISC2), offering comprehensive certification for information security professionals. http://www.issa.org/ Information Technology Association of America ITAA. A trade association representing the U.S. information technology (IT) industry. The ITAA responds to developments in governmental and international IT policy, promotes the interests of its members, and participates with other organizations in developing Internet policies. http://www.itaa.org/ Information Technology Association of Canada ITAC. A trade organization supporting Canadian information technology providers, ITAC identifies and focuses on issues affecting the IT industry and advocates initiatives promoting its growth and development. http://www.itac.ca/ Information Technology Industry Council ITI, ITIC. Formerly CBEMA, the Computer and Business Equipment Manufacturers Association, ITIC is a trade organization representing leading U.S. providers of information technology (IT) products and services. It includes well-known vendors such as 3Com, Amazon.com, Apple, Computer, Inc., Cisco Systems, Inc., Hewlett-Packard Company, IBM Corporation, and many more well-known firms. ITIC produces an industry Data Book with statistical information on computers and telecommunications equipment and services. See Information Security Exploratory Committee. http://www.itic.org/ Information Technology Research Center ITRC. There are many research centers operating under this name (or slight variations of the name), so only examples are listed here, but since most of them are directly concerned with advancements in telecommunications technologies, this selection gives an overview of some of the Information Technology (IT) centers accessible on the Web, along with their goals, and their geographic distribution. The Information Technology Research Center chart focuses on governmental and educational research centers. There are also many IT research centers supporting commercial vendors. information theory The pioneer studies in queuing theory were developed and described by A.K. Erlang, a Danish engineer, in the early 1900s. Information theory, an evolutionary cousin to queuing theory, is a field of inquiry and mathematical modeling that was largely developed and disseminated by Claude E. Shannon while he was working at Bell Laboratories in 1948. Shannon took a theoretical, mathematical look at information, in terms of not only its content and structure, but also its source and purpose. Thus,

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Information Technology Research Centers – Brief Selection Title

Abbrev.

Information Technology Research Center

Description

ITRC

An interdisciplinary research unit at the University of Arkansas devoted to advancing the state of research and practice in the development and use of information technology (IT). http://itrc.uark.edu/ Information Technology Research Center

ITRC

A nonprofit organization dedicated to the development, evaluation, and application of advanced technologies to enhance scientific research and education in information technology (IT). The Center is international in scope, operating out of Missoula, Montana. An example of an ITRC project is the TRIO ThinkQuest Project, U.S. Department of Educationfunded project for sponsoring an online educational Web site development contest. http://www.itresearchcenter.org/ Information Technology Research Center

ITRC

A funded project in which the Innovative Computing Laboratory at the University of Tennessee Knoxville campus will be transformed into an IT research center with a broader scope, under the direction of Dr. J. Dongarra. Advanced Information Technology Development Research Center A Japanese center to support research to improve road traffic systems, traffic information provision systems, and home information systems, as well as research on the application of geographic information systems (GIS) and other information technologies to design and construction. Center for Information Technology Research in the Interest of Society CITRIS A California Institute for Science and Innovation, endorsed in December 2000. CITRIS is located at the University of California, Berkeley and is dedicated to promoting scientific advances in information technology fields critical to the California economy. German National Research Center for Information Technology GMD A cutting-edge national and international research facility devoted to applications-oriented research in the information and media industries with a view to developing new products. http://www.gmd.de/ Information Technology Research Centre ITRC An Ontario-based Canadian information technology (IT) research center. Research Center for Communications and Information Technology ReCCIT A Thai institute of King Mongkut’s Institute of Technology Ladkrabang (KMITL), ReCCIT supports a number of cooperating labs in telecommunications, information technology, signal processing, and signal transmissions. Research projects are wide-ranging, including mobile and satellite communications, information science, multimedia, virtual modeling, circuit design, signal processing, and more. http:// www.kmitl.ac.th/~reccit/ Research Center Information Technology RCIT Since 1990, RCIT has been developing large-scale, dynamic information systems for public institutions and companies in Europe. RCIT is also the European Telework Development (ETC) national coordinator.

signals and their frequencies, bandwidths, physical components, and electromagnetic characteristics were set in the broader framework of the information and its human source. This became the basis of a broader view of communications and provided groundwork for more specific measures and descriptors of content and capacity that have real world usefulness. Information theory has aided in developing more objective system evaluation tools, compression techniques, and practical applications such as voiceover IP systems. See erlang, queuing theory. infrared Electromagnetic radiation with longer wavelengths which, in terms of frequencies, fall between the red part of the visible spectrum and radio waves. Although it cannot be seen by humans, infrared radiation is of commercial importance in remote sensing systems, remote control devices, video game consoles, and fiber optic transmissions. It is also being exploited for local area wireless networks (LAWNs). Infrared serial data link standards are being adapted by a number of manufacturers. Infrared technology can be used to detect differences in heat and, consequently, movement of bodies emitting heat. Infrared detectors are used in many industries including electronics, construction (structural fault detection, heating, and insulation testing), and medical imaging. Infrared film is used in specialized photographic applications. See Infrared Serial Data Link, snooperscope, ultraviolet. Infrared Communication Systems Study Committee ICSC. A research committee of the Association of Radio Industries and Businesses (ARIB), organized to study and promote awareness and use of infrared communications systems. Centered in Tokyo, Japan. Infrared Data Association IrDA. An organization established in 1993 to support and promote software and hardware standards for cordless/wireless infrared communications links. IrDA is headquartered in California. Infrared can be used with remote controls to control various consumer electronics devices and can also be used for data transmission between devices such as laptops, desktop computers, and peripherals. See Infrared Data Association Protocol. Infrared Data Association Protocol IrDA Protocol.

A multilayered networking structure from IrDA for defining hardware and software needs for infrared network communications. The IrDA protocol stack covers physical transfer of information, guidelines for link access, and link management. The layers are briefly described in the IrDA Network Protocol Layers chart. Infrared Link Access Protocol IrLAP. A serial link access protocol from IrDA which provides three types of connectionless services and six types of connection-oriented services with four types of service primitives. IrLAP provides discovery, address conflict, and unit data services over connectionless services and connect, sniffing, data, status, reset, and disconnect services or connection-oriented services. IrLAP is primary-secondary or primary-multiple station oriented. The IrLAP layer is intended to facilitate interconnection of computers and peripherals over a directed half-duplex medium provided through the physical layer. IrLAP stations can be operated in Normal Response Mode (NRM) or Normal Disconnect Mode (NDM), which correspond to connection state and contention state. IrLAP data and control are frame-oriented, with a frame including an address, a control field for determining frame content, and an optional information field. infrastructure The structural underpinning or base which supports the other layers associated with a system. ingress 1. Entrance, point of entry, way in, opening, doorway. 2. In Frame Relay networks, frames that are entering toward the Frame Relay from an access device. The opposite of egress. initial address message IAM. In Signaling System 7 (SS7) networks, a signaling message sent in the forward direction that initiates seizure of a circuit, and provides address and routing information for the connection of the requested call. See Signaling System 7. Initial Defense Communications Satellite Program IDCSP. A project of the U.S. military, IDCSP first launched three satellites in 1967. They included X-band transponders in the 26-MHz bandwidth, and supported experimental terminals for evaluating

IrDA Network Protocol Layers Layer/Proto.

Notes

IrLMP

A mandatory link management protocol which manages resources and services and higher-level protocols which are made available to other devices. IrLMP sets up and maintains multiple connections.

IrLAP layer

Link establishment, maintenance, and termination. Similar to the half-duplex link control (HDLC) protocol.

physical layer

Provides point-to-point connections and communications between devices with cordless/wireless serial infrared half-duplex links.

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images, voices, digital data, and teletype channels using a variety of modulation schemes. The IDCSP was designed to shut down after five years of useful life. Initial MAC Protocol Data Unit IMPDU. In packet-switched networking, the IMPDU encodes Media Access Control (MAC) Service Data Unit information. A number of MAC Protocol Data Units (PDUs) are derived from the segmentation of the IMPDU. See Media Access Control, Protocol Data Unit. initial program load IPL. The bootstrapping of a system in that the operating system is loaded up first to make it possible to bring the other hardware and software systems online (monitors, disk drives, interface applications, etc.). Some systems provide a means to “soft boot” a machine (reloading the initialization software and OS without turning the power off and on again). Many systems will now allow the user to set the device from which the computer will boot, especially if the computer has several possible boot devices such as hard drives, CD-ROM drives, and floppy diskette drives. At the present time, most systems have minimal startup programs stored in ROM chips and then default to boot the rest of the initialization of the OS from hard drives. They will typically seek operating system software on other devices if it is not found on the default drive and may be set to boot from a CD-ROM or diskette first (rather than the hard drive) if a disc/diskette is present. In a more specific sense, this same bootstrapping process occurs with many computer subsystems. For example, there may be components or peripherals associated with a computer system that store initial parameters in ROM chips or on other storage devices that make it possible to bring the rest of the device’s capabilities online. Initial Public Offering IPO. A Securities Commission government-regulated mechanism for a company to offer a variety of types of shares (usually common and preferred stock) to the general public. There are a number of categories of public offerings, both state and federal, with levels of restrictions and guidelines depending upon the amount of investment sought. Telecommunications and biotech are two of the hot areas of recent years, and some high-profile stock offerings have been carried out in the technology industry, one of the most visible being Netscape Communications, developers of Web browsers/servers and other applications. The investment for a company to go public can be considerable. Being listed on one of the large trading boards can cost millions of dollars. As a result, a number of Internet trading startups have been developing as an option for companies to make the availability and value of their shares known to the public. There are many companies that offer public shares that are not listed on the big boards; many are described on “pink sheets,” an information vehicle known to brokers, but not widely known to the public. This is because of very strict regulations against

advertising stocks. It is permissible to provide information to investors who request it, but not to publicly promote company shares. These regulations are somewhat less stringent at the local level, with small offerings of a $million or half $million state-regulated Direct Public Offerings (DPO) providing some means for offering investor relations information to the public. DPOs were not widely known or attempted prior to the development of the Internet, because small companies making small stock offerings simply did not have the resources to provide investor information to potential investors and brokers in sufficient quantity to attract investment. Now that the Securities Commission has opened a few doors to stimulate investment in small companies, extremely important to the national economy, trading boards on the Internet are getting a lot of interest from investors and brokers, and DPOs are feasible for raising capital for seed and startup companies. inkjet printing An inexpensive color printing process in which inks from a series of ink “wells” are fired through a tiny opening called a nozzle. The firing is accomplished through heating the ink chambers to a high temperature so a vapor bubble is formed, which rapidly ejects the ink through the end of the nozzle onto the printing medium, where it cools and adheres. See dye sublimation printing, thermal wax printing.

Inmarsat Service Categories Service

Notes

Inmarsat-A

Analog voice, data, and facsimile services

Inmarsat-B

Digital voice, data, and facsimile services

Inmarsat-C

Store-and-forward data, aeronautical voice, and facsimile services; marine access to email and telex networks, two-way messaging through 5-kg terminals

Inmarsat-M

Briefcase phone

Inmarsat-Aero Airline passenger communications supporting voice, facsimile services, with X.25 data services planned

Inmarsat International Maritime Satellite Organization. Originally an international cooperative agency established in 1979, Inmarsat was then slated for privatization for 1 January 1999. It launched in 1992 and has provided global mobile satellite communications services (voice, data, facsimile), especially maritime services, since 1993. Inmarsat now serves over 80 member countries. Inmarsat has a system of four geostationary satellites

orbiting at 35,786 km using frequency division multiple access (FDMA). It provides transportation communications and Internet connect services. Five more are scheduled to be launched by the end of the century. Twelve medium Earth orbit (MEO) satellites are also planned. Customers purchase services from a variety of packages depending upon whether they need phone, facsimile, Internet, emergency services, telemedicine, etc. The ICONET satellite system is a spin-off of Inmarsat communications services, originally known as Project 21. See Inmarsat Service Categories chart. See ICO Global Communications. http://www.inmarsat.org/ INN 1. See InterNet News. 2. InterNode Network. INP See Interim Number Portability. InPerson A consumer-priced SGI-based videoconferencing system supporting video, audio, whiteboarding, and file transfers over analog phone lines and Ethernet networks. Video encoding is accomplished through HDCC compression developed inhouse at Silicon Graphics with several audio compression formats. input Information, in the form of a communication or signal, provided to a person, system, or circuit. Computer software input mechanisms include graphical user interfaces, shell windows, buttons, icons, dialog boxes, etc. Computer hardware input mechanisms include keyboards, mice, trackballs, touchscreens, joysticks, video cameras, and microphones. The input device on a telephone is relatively simple: a small speakerphone or diaphragm (microphone) in the telephone handset.

The joystick on the left and the mouse on the right are two common types of input devices for computer games, virtual reality, and day-to-day computing for business, education, and pleasure. Other types of devices include data gloves, pen styluses, microphones, touchscreens, video cameras, and tactile pads.

input device IDev (ID is sometimes used but may be confused with identification). An interface device for receiving and transmitting information from an input source (frequently human) to a processing system or remote location, usually a computing machine or electromechanical device. The input sensor and the transmissions unit are often housed together (e.g., telephone). There are a great variety of input devices including keyboards, mice, joysticks, light pens,

touch screens, microphones (especially with speech recognition systems), infrared sensors, video cams, etc. The invention of the mouse, one of the most common computer input devices, is attributed to Doug Engelbart in the 1960s. Many of the input devices in common use today were pioneered by Ivan Sutherland in the early 1960s. See individual input devices. inquiry The systematic pursuit of information through queries and observation. A more general term than query, an inquiry may include a series of queries and observations leading hopefully to acquisition of the desired information. The process and modeling of inquiry is of great interest to designers of computer software, especially in natural language processing, artificial intelligence, and database search and retrieval. See query. inside link See horizontal link. INSPEC The world’s largest English-language bibliographic database in physics, computing, and electronics. INSPEC evolved from Science Abstrcts, which was first published in January 1898. The database regularly catalogs the contents of over 4000 journals, in addition to conference proceedings and other relevant literature. It currently holds more than 6 million records. See Institution of Electrical Engineers. installed base An industry phrase that describes the quantity of products or systems in use extant, or the number of current users of a particular service. The installed base may not indicate the number of products sold. For example, due to software piracy, the number of copies of a software application which have been sold may be 20,000, whereas the installed base may be 220,000. In the other direction, there may be 1 million disposable widgets sold, but an installed base of only 300,000 if some are discarded, lost, broken, etc. Formulas for establishing installed base statistics are industry specific and somewhat subjective, but still provide useful information for marketing, production, and repair managers. instant on A consumer electronics term that refers to devices and appliances which power on or come online quickly, usually at the touch of a button, and are immediately ready to use without inspection, training, or configuration. Some VCRs have an instant on record mode where popping in the tape makes the component power up automatically, allowing the user to quickly press record. Many video game consoles are instant on, ready to play as soon as the power is turned on. A few vendors have tried to sell computers with preloaded software with the instant on concept, but this is more difficult to achieve. Set-top boxes for Internet access are a middle ground between a full computer system and an instant on system, as are dedicated word processing systems. Turnkey software and hardware products are sometimes designed with an instant on orientation. For example, the Video Toaster by NewTek could boot up directly into the video switcher software, and bypass the operating system startup messages and CLI

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screen so effectively that many purchasers didn’t realize they were using an Amiga computer that launched directly into applications mode. Similarly, library electronic catalog access programs typically boot directly into the catalog user interface, and the user may not be able to tell which operating system is behind the software. Institute for Advanced Commerce IAC. An IBM forum for studying fundamental aspects and trends in business. Through academic partnerships and conferences, the Institute tracks business and market characteristics with the goal of creating long-term corporate solutions. An important focus of advanced commerce is the application of computer and communications technologies, collectively known as ecommerce. Institute for Telecommunication Sciences ITS. The applied research division of the U.S. National Telecommunications and Information Administration (NTIA). The ITS develops, tests, evaluates, and promotes advanced communications networks and domestic standards through its Boulder, Colorado, facility. Institute of Radio Engineers IRE. The IRE was a historic professional organization formed as a result of the merger of the Society of Wireless Telegraph Engineers (SWTE) and The Wireless Institute in 1912, in order to establish and promote an international orientation for the consolidated organization. It served as a standards body, in cooperation with the U.S. Federal government, and a professional support group for its members and the radio community at large. See American Institute of Electrical Engineers, IEEE. Institute of Electrical and Electronic Engineers, Inc. See IEEE. Institution of Electrical Engineers IEE. A U.K.based professional engineering society founded in 1871 that now has almost 140,000 members worldwide. The IEE supports and promotes advancements in electrical, electronic, and manufacturing sciences and engineering and provides publications, historical archives, research databases, exhibitions, and educational activities for its membership and, in some cases, for the general public. IEE produces the INSPEC engineering science database. See INSPEC. http://www.iee.org./ Instrumentation, Systems, and Automation Society ISA. A standards-setting, international, nonprofit, professional society supporting instrumentation and systems engineers in more than 100 countries. ISA provides a number of publications and awards relating to the fields of instrumentation and automation, as well as certification resources. http://www.isa.org/ Insulated Cable Engineers Association, Inc. ICEA. A not-for-profit professional trade association dedicated to developing cable standards for the various control, power, and telecommunications industries, founded in 1925. ICEA generates documents of interest to cable designers, manufacturers, and vendors. http://www.icea.net/ insulated wire Conductive wire that has been coated, sealed, rubberized, clad, sheathed, or otherwise

covered or processed to protect it from electrical leakage and external electromagnetic interference or corrosion. It may also be internally insulated if the wire is bundled with other wires or fabricated in layers that could interfere with one another if not separated with nonconductive materials. insulation A material or particulate environment composed of atoms that do not readily give up their electrons. This inertial property can be exploited to create industrial materials resistant to the flow of current and exchange of heat between environments with disparate temperatures. Examples of common insulating materials include rubber, glass, and porcelain, but other substances can be insulators because insulation is somewhat contextual. The Earth’s atmosphere is an insulator, shielding the planet from ultraviolet radiation, for example. When a storm occurs and electrical charges accumulate around clouds, they may overcome the air’s insulating properties and manifest as lightning. Historically, insulation was crucial to the successful installation of underwater telegraph cables, beginning in the 1800s. Gutta-percha, a rubberlike substance with excellent industrial properties for the time, made it possible to lay cables in corrosive salt environments, where attempts with other materials had failed. Insulation also made it possible to install underground telegraph and telephone wires and wires that could be used in harsh wilderness environments. In the 1930s, AT&T introduced a wire with improved insulation for telephone transmissions. There are many primary and secondary ways in which insulation is used in telecommunications, including • shielding conductive materials from heat or electrical interference, • providing protection from external physical damage (erosion, corrosion, abrasion, tampering), • providing protection and spacing among or between proximate or layered electromagnetic influences, • providing a surface upon which marks or colors can be imprinted to aid in installation and maintenance, and • providing protection to humans handling current-carrying wires. There are some differences between insulating wires and fiber optic bundles. Wired telecommunications typically carry one signal per wire and wire is somewhat resistant to breakage if it is bent (a 180°+ bend can often be straightened out again without breaking a wire). While several wires may be bundled together (e.g., transatlantic telegraph cables were a collection of bundled wires), wire assemblages typically don’t have the high number of strands found in fiber optic cables, and tiny fiber optic strands can break or easily become separated from the assemblage at junction points. Wires and optical fibers are also subject to different forms of environmental damage, resulting in different choices for the types and thicknesses of materials used to protect them.

A small gouge or scratch may not significantly alter the overall current-carrying characteristics of a wire but can significantly impair a tiny fiber from transmitting a consistent optical signal. Insulation has to be designed to accommodate these differences and stripping tools must be suitable for removing optical fiber insulating sleeves. Further, installers must be aware of electrical shock hazards when working around current-carrying wires, which is not a problem with optical fibers. Industrial insulation is used for purposes other than covering wires. It may also be used to regulate the air temperature in facilities where material temperatures or operating temperatures are important, as in supercomputing applications or fabrication plants, where the room or chamber environments are important. Insulation is further used in atomic research facilities, as in supercooled environments, for studying specialized computing functions (e.g., quantum computing). See dielectric. insulator See insulation.

Insulators on utility poles are a common sight. They were once constructed of glass (the early ones handmade), but now ceramic insulators are generally used and old glass insulators are collectibles.

Insulators were developed in many shapes and sizes, in a rainbow of gem-like hues. They provide a legacy of poetically descriptive category names such as slashtops, bat ears, eggs, beehives, and teapots. Well-known glass insulator manufacturers, like Hemingray, shut down by the mid-1960s. Historic glass and ceramic insulators are found occasionally in secondhand stores and antique auctions, and older or more interesting ones are favored by collectors and sometimes sell for hundreds of dollars. Insulator styles are extensive and beyond the scope of this reference, but a few historic insulator types and makes are listed in the Sampling of Insulator Types chart.

Sampling of Insulator Types Type

Notes

Barclay

Patented by John C. Barclay.

Beaver Falls

A lesser known glass insulator fabricator.

beehive

An early insulator patented by Samuel Oakman in 1884.

bird feeder

Battery rest insulator.

bridle wire

An early AT&T insulator.

Brookfield

A line of various insulators from the Brookfield Glass Company.

double petticoat Named for the double-tiered skirting. Hemingray

insulator, utility pole Historically, the fact that glass would make a good insulator was suggested by E. Cornell, who assisted Samuel Morse in installing the historic 1843 Washington, D.C.-to-Baltimore telegraph line. He originally proposed glass plates and later described a more knob-like design, a larger version of which eventually became standard and widely used on utility poles until the 1970s. Utility pole glass insulators are thick, threaded, mugor thermos-sized objects, in clear glass or a variety of colors, most often blue or green. A number of hand-blown insulators were created in the late 1880s. The oldest commercial mass-produced ones, originating some time in the early 1850s, lacked threads but were colored. Molding processes for creating insulators were patented in the 1870s. The Oakman beehive insulator was favored by Western Union for telegraph poles. Western Union used many thousands of Brookfield and Hemingray insulators over the years. The move to standardize insulators occurred around 1910; clear insulators were not produced until the 1930s. Ceramic insulators were introduced around 1908 by Locke Insulator, in order to undercut the cost of glass insulators.

A line of various insulators from Hemingray.

National corkscrew Less common type with a characteristic shape. Storrer

Patented by Storrer in 1906, shipped by Brookfield 1909.

INTEGRAL International Gamma Ray Astrophysics Laboratory. A medium-size scientific mission selected in June 1993 by the European Space Agency (ESA) for the Horizon 2000 program. The ESA-led orbiting observatory mission is being carried out with contributions by NASA and the Russian Federation. INTEGRAL is involved in imaging and spectroscopy of celestial gamma-ray sources. Observations will be telecommunicated to ground-stations and made available to the global scientific community. Integrated Access Device IAD. A data communications device that provides data and voice services, usually to small- and medium-sized businesses. IADs have generally been used to provide circuit-switched services, but as of January 2001, IADs supporting migration to packet-switched IP services were being offered commercially by Cisco Systems, Inc.

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Integrated Broadband Communications IBC. A European Community-wide system of communications capable of supporting a wide range of service providers that was emerging in the mid-1980s and whose development was formally supported in a decision of the European Community (EC) in December 1978. It was felt by the European Council that telecommunications systems would benefit the EC’s international competitiveness in general and the telecommunications sector in particular. It was also stated that a system that united rather than regionalized communications would be preferable and that common specifications were necessary but not sufficient to bring this about. The Single European Act was expressed to provide a good political and legal base for developing a European-wide scientific and technological strategy and industrial competitiveness in telecommunications. One of the important contributors to the development of the IBC is the Research and Development in Advanced Communications in Europe (RACE) program. RACE was involved in overall IBC development and more specifically, the development of the Mobile Broadband System (MBS) being integrated with the IBC. In 1995, at the end of its specified term, RACE evolved into Advanced Communications Technologies and Services (ACTS) to represent the third phase of IBC implementation. See Mobile Broadband System, Research in Advanced Communications in Europe. Now that many of the initial steps in establishing IBC have been taken, it is expected that more Europeans will stay at home to work, study, and socialize over computer networks, etc., thus increasing the importance of and demands on IBC. It is also expected that individuals with limited mobility can benefit from IBC and that educational, government, and health care services will be an important aspect of IBC. integrated circuit IC. A single electronic component that incorporates what would normally require many traditional electrical circuits. This enables complex, sophisticated capabilities to be bundled into tiny packages and also often increases the speed of interactions and processing. A computer central processing (CPU) chip is one particular type of integrated circuit; a combination of circuits and chips included on a single card, like a peripheral card, is also an extension of the concept of an IC. Very large scale integration (VLSI) technology is the combination and interaction of many circuits in a combined package. In Canada, the Integrated Circuit Topography Act (1990) exists to protect registered integrated circuit designs as a form of intellectual property. Various U.S. and foreign copyright and patent laws also protect and publicly disseminate information on unique ICs. The concept for making resistors, capacitors, and other common hardware on circuit boards out of silicon was new in the 1950s. Engineers from the old school evolving out of decades of experience with vacuum tubes and discrete components didn’t immediately conceive the idea of using the new semiconductor

technology for modeling all (or many) aspects of a circuit design. The earliest ICs included only a single transistor. Now, astonishingly, more than a 100 million transistors can be packed into an IC. Credit for the introduction of ICs, in 1959, has long been attributed to Robert N. Noyce, a Dane who was working at Fairchild Semiconductor and who helped form the Intel Corporation in America. Noyce was awarded a U.S. patent in 1961. However, it appears Jack St. Clair Kilby, a Texan, is the original “Father of the IC.” Kilby apparently introduced the concept in September 1958, and Texas Instruments Incorporated (TI) applied for a patent on Kilby’s concept a few months later. It has been reported that Kilby’s patent was still being assessed as the Noyce patent was granted. In recent years, Kilby’s contribution has been acknowledged and lauded and Texas Instruments has named a research center in his honor. Historians generally consider the two inventors to have independently developed their ideas at about the same time. In engineering circles, the abbreviation IC is often used as a pun to refer to both integrated circuit and “I see.” See semiconductor, very large scale integration. See Kilby, Jack; Noyce, Robert.

In 1958, Jack Kilby constructed a historic integrated circuit (IC) using germanium as the semiconductor, at about the same time that R. Noyce was working on the IC concept at Fairchild Semiconductor. Kilby’s circuit was primitive by today’s standards, mounted on a transparent synthetic base with four wire leads protruding from one side, but the invention was one of the most important in electronics history, following the milestone inventions of the triode in the early 1900s and the transistor in the 1940s.

integrated data access IDA. A phrase usually applied to database access through shared resources or automated lookup tools that facilitate informationfinding. A number of Web-accessible government archives are said to be IDAs. IDA also applies to a number of commercial database products that have various database discovery, search, and retrieval functions built into the product so that it can be readily deployed by an institution to set up information delivery services without a lot of time spent on in-house programming. Integrated Digital Loop Carrier IDLC. A system designed to integrate Digital Loop Carrier (DLC)

systems with existing digital switches as in a SONET network system. A basic installation consists of intelligent remote digital terminals (RDTs) and digital switch elements known as integrated digital terminals (IDTs), interconnected by a digital line. See Digital Loop Carrier. Integrated Digital Network IDN. A digital network in which both the switching and the transmission are digital. Traditionally, communications switching has been analog, even if the data transmission was digital, necessitating modulation and conversion that limited transmission integrity and speeds. Gradually digital switches began to replace analog and digital phone; data services for general consumers began to become widely available in the late 1990s. A computer with a modem is an example of a hybrid digital/analog transmission system. A computer generates digital data that is sent to the modem for conversion to analog signals for transmission through traditional copper phone lines. At the destination, it is remodulated back to digital data and interpreted by a computer. While the transmission was in effect, the phone line would be tied up to preclude voice transmissions. With the evolution and installation of digital circuitry throughout the phone system, a gradual transition to digital services such as ISDN and ATM is enabling enhanced communications services for business and residential customers as endto-end digital transmissions systems are gradually supplanting analog or hybrid systems. It is now possible to transmit data and digital voice services over the same subscriber line. Terminal devices rather than traditional modems are used to interconnect subscriber premises to digital services over public networks through both copper and fiber optic media. See ISDN, Signaling System 7. Integrated Dispatch ID. In general, computer-enhanced dispatch administration and/or messaging services integrated with traditional radio dispatch communications. This is of particular interest to emergency services call centers, where accountability and response times are important, and also to companies that have sophisticated dispatch tracking needs. See Enhanced Specialized Mobile Radio. integrated injection logic IIL. A form of bipolar logic, reduced power circuit intended to provide greater efficiency over TTL chips. Integrate IS-IS A proprietary routing protocol using one set of routing updates, developed by Digital Equipment Incorporated (DEC). DEC’s version is based on the Open Systems Interconnection (OSI) routing protocol called IS-IS. The DEC implementation provides support for a number of other open and proprietary protocols by encapsulating them into Internet Protocol (IP). Integrated Internet Information Architecture IIIA. An effort by Weider, Mitra, and Sollins, et al, to develop protocol specifications and enhancements for some of the widely used Internet information systems. Based on the concepts that one solution will not fit all users and that users need a way to transition to other systems as their needs mature or change,

the developers have focused on creating objectoriented informational and functional models for an Internet information architecture. integrated messaging, unified messaging A term to describe the combination and consolidation of messaging services such as voice, video, facsimile, email, etc. through a networked computer system. With a computer phone set, a scanner, and a printer attached to a microcomputer, it is possible to have all the capabilities of these various technologies integrated into one system. In fact, setting up the system this way provides more capabilities than these services have individually, since the computer software can be configured to monitor the calls, store accounting information, transfer data among the various systems, and use files directly, as in directly faxing a document from the word processor, without printing it and sending it through a dedicated facsimile machine. When a facsimile is received, it can be processed to turn it into text and images, or document and PostScript-format files can be sent directly, without any scanning or translation. By attaching an Internet phone set to the computer, the computer can check the time at the desired destination, dial the call automatically from a database of names, connect the call, signal an alert when it is connected, keep track of the duration of the connection, alert you while making the call if you are attending to other business, and log the call, if desired, for future reference or statistical or business tracking. By using an integrated voice, file, email service, you can speak into the headset or a microphone and record a mail message, send it the same as normal email, which means the recipient can access it whenever he or she is online, and listen to it played on the destination computer as a sound file. This message can easily be combined with text files with binary files as attachments. The NeXTStep operating system has had this flexible type of voice/email/file capability built into its email system since the late 1980s, and Smalltalk object-oriented systems had it even sooner, so it is by no means a new concept. Unfortunately, it is not yet implemented on many commonly used platforms. integrated model A network traffic routing solution supporting an exchange of routing information between ATM routing and higher level routing. This provides timely external routing information within the ATM routing and provides transit of external routing information through the ATM routing between external routing domains. Integrated Next Generation Electronic Commerce Environment Project INGECEP. A trio of experimental projects to test online business/financial environments. INGECEP was proposed by the Telecom Services Association of Japan (TELESEA) to the APEC Telecommunications Working Group as an international interconnection of electronic commerce test-beds. In Japan project funding is provided by the Ministry of Posts and Telecommunications. INGECEP is promoted by the member companies

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of the Cyber Business Association (CBA) as follows: • a debit-based commerce system introduced as a pilot project in 1995. It is associated with multimedia information (online malls, educational institutions, government sites, museums, etc.) provided by regional SMEs in cooperation with the Telecom Services Association of Japan (TELESA) on the backbone network using TCP/IP over ATM. • a secure electronic credit-based commerce system utilizing Japanese cryptologic technology, HTTP, and MOSS carried out at the Japan Electronic Messaging Association (JEMA) • an electronic money system launched to promote content-based business. The first INGECEP trials between Japan and Singapore were conducted in July 1998. Increased interest after this trial necessitated guidelines for interconnecting multiple cross-border economies. This is an important electronic commerce globalization effort. It defines, specifies, and tests cross-border remote technologies in the context of consumer trust, privacy, and language differences while also taking into consideration consumer protection, currency differences, import/export regulations, and

money transfer transactions. After initial testing, a new approach labeled the Electronic Market system was employed to increase the scope of the project around the Asia-Pacific Region, including South Korea, Malaysia, and the United States. Integrated Services Digital Network See ISDN, Signaling System 7. integrated service A type of service more recently being designed and deployed on the Internet in addition to best effort services traditionally provided. Integrated services support special traffic handling based upon bandwidth, network latency, and other requirements not usually handled with best effort services. Examples include guaranteed service and controlled load service. Intel Corporation One of the best known of the chip manufacturers serving the desktop computer market, rivalled mainly by Motorola. Intel’s chips are widely installed in microcomputers worldwide. Intel evolved out of an earlier company founded by Gordon Moore and Robert Noyce, who had worked together at the Schockley lab in Palo Alto. They founded a division of Fairchild Camera to exploit semiconductor technology, called Fairchild Semiconductor. They later cofounded Intel Corporation. which continues today as one of the world’s leading chip design and manufacture firms.

Overview of Some Common Intel Desktop Computer Central Processing Units Processor

4004

Data Int. Bus 4/8

Data Ext. Bus 4

Address Clock Bus Speed 12

1 MHz

4040

Year Introd.

Notes

1971

Separate program and data memory; 46 instructions Enhanced 4004 with 14 additional instructions, and more space for programming and stack Similar to 4040 Seven 8-bit registers, some of which could be combined into 16-bit register pairs; 256 I/O ports An update to the 8080 Based upon the 8080 and 8085; 8-bit 64K I/O

1972

8008 8080

8 8

8 8

14 16

2 MHz 2 MHz

1972 1974

8085 8086

8

8

20

5 MHz

1976 1978

80286 80386DX 80386SX 80486DX

16 32 32 32

16 32 16 32

24 32 24 32

8 MHz 16 MHz 16 MHz 25 MHz

1982 1985 1988 1989

80486SX Pentium Pentium Pro Pentium II Pentium III Pentium IV

32 32

32 64 64 64

32 32 32 32

20 MHz 1991 66 MHz 1993 133-200 MHz 1995 233-333 MHz 1997 500 MHz 1999 1400 MHz 2000

On-board cache, pipelines, integrated floating point unit Separate caches; superscalar CISC-RISC MMX MMX 2

The Intel 4-bit 108 kilohertz 4004 microprocessor became an important historical impetus in the design of desktop computers, with its successor, the 8008, becoming the world’s first commercially significant programmable central processing unit (CPU). The 4004 was developed by Marcian (Ted) Hoff, introduced in November 1971. Three other chips accompanied the 4004, offered as the MCS-4 chip family. The Scelbi computer, first promoted in 1974, and the Altair, which came out as a kit a few months later, incorporated the successor to the MCS-4 family, the MCS-8, based around the 200-kHz 8008 (the 8008 was an enhanced version of the 4040) 8-bit microprocessor. The 4004 was incorporated into many automated systems, including light controls, appliances, calculators, musical instruments, etc. Gary Kildall developed a programming language for the early Intel processors called PL/M. The 8080 was incorporated into the Altair 8800, as it was in some of the S-100 bus (Altair bus) computers that became competitive with the historic Altair. Since then, the most significant evolution in Intel desktop computer chips is the Pentium series, introduced in the early 1990s. The Intel Overview table is not comprehensive, but it provides an encapsulated look at some of the highlights in Intel chip development for microcomputer CPUs since the mid-1970s. See Hoff, Marcian; integrated circuit; International Business Machines; Kildall, Gary; Moore, Gordon; Motorola; Noyce, Robert. Intel Video Interactive IVI. Intel purchased the Digital Video Interactive (DVI) chipset technology and developed it into Indeo 2 and Indeo 3, now known as IVI. IVI has a number of interesting features, including transparency (e.g., for background overlays), scaling, and the use of an interframe codec for compression, based on relatively new wavelet compression, encoding the images into frequency bands so the image data can be represented at different resolution levels. Data can be password-embedded for protection. Key frames can be incorporated as reference points for random access. Brightness and contrast settings can be adjusted to adapt to the characteristics of the playback system. intelligent agent A software application preconfigured or trained to handle tasks dynamically, or that has been trained to recognize certain characteristics of the input, which might be a person’s voice, handwriting, or other specialized type of input that may vary from user to user. An intelligent email agent may be configured to screen out “spam,” unsolicited commercial messages, to sort messages into folders according to sender or priority, or to forward messages to another address if the user is traveling or reading mail at another location. The difference between a custom agent and an intelligent agent is that the custom agent is explicitly configured by the user, whereas the intelligent agent configures itself on the basis of monitoring the user’s

habits and interaction history. The agent then establishes actions and parameters based on intelligent analysis of the user’s actions and preferences. In other words, a custom agent would require that the user explicitly instruct the email client to put all messages with “make money fast” in the subject line into a spam bucket, a file that contains unsolicited email. An intelligent agent would notice that 15 messages in a row with “make money fast” in the subject line were moved to the other file area, and would subsequently do the transfer automatically on behalf of the user, perhaps prompting the first time it makes this decision in order to confirm that it is carrying out user preferences. See artificial intelligence, expert system. intelligent answering A telephony industry marketing phrase for telephony-computer applications that pop up an information box on a computer screen based on the number that has been called or answered. The pop-up box provides information about the caller/callee contained within publicly available databases or in-house client lists or contact databases. Intelligent I/O An open standard designed to provide a device-independent device driver architecture. Applied to redundant array of inexpensive disks (RAID) systems, Intelligent I/O can provide faster hard drive access. intelligent load balancing In computer telephony integration (CTI) applications, a mechanism for balancing call volume in centers that handle many calls or that forward to calls to subsidiary call centers. Load balancing is based on statistical models for evaluating queues, call durations, call priorities, and the number of agents available to handle the calls. The intent, of course, is to streamline the service so that calls are handled quickly and efficiently, and distributed well over the types and numbers of agents available. Intelligent Music Workstation IMW. A five-year long project which resulted in the 1994 release of a musical software/hardware environment in which commercial products can be integrated as modules. Developed at the Laboratory for Musical Informatics of the Department of Information Sciences of the University of Milan, Italy, funded by the Italian National Research Council. Intelligent Network IN. See Advanced Intelligent Network. Intelligent Networks Call Model INCM. Gaddis et al., described a Call Model for multipoint communications in switched networks in the early 1990s. The model provided dynamic multipoint, multiconnection communication channels (calls) for network clients. Protocols were defined for clients to create, manage, and manipulate telecommunications calls. The Model provided basic interconnection services for local and wide area networks. At about the same time, Hill and Ishizaki described a Call Model for distributed multimedia communications intended to encompass a number of types of media rather than being restricted to a specific type of data communication (e.g., videoconferencing).

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In current practice, the INCM is a significant telecommunications Call Model central to advanced intelligent networks (AINs) that are typically implemented over SS7 networks. In general, this Call Model is a representation of service switching point (SSP) call-processing functions for establishing, maintaining, and taking down a call. The Call Model incorporates Points in Call (PICs), Trigger Detection Points (TDPs), and the triggers themselves. INCM is also sometimes called the Basic Call Model. See Universal Call Model. intelligent routing 1. In data networks, an automated, dynamic, self-configuring routing system that takes most of the workload of configuration and maintenance from the human operator and handles it through software algorithms. These days, most routers and switchers are designed to handle routing intelligently and the distinction between routing and intelligent routing may gradually disappear. 2. In telephony call servicing, a marketing phrase to describe the automatic routing of a call to an appropriate operator or sales rep. based on information and criteria contained in a list or more complex database. As an example, if a call comes in from ABC Copy Machines, from which a company leases equipment, a scenario can be set up to route ABC Copy Machines’ calls to the equipment department or the print room, depending upon who usually talks to that vendor. Similarly a new caller, with a number that is not yet recognized by the system, might be routed to the information desk or to a new client sales rep. intelligent transportation systems ITS. Transportation systems that incorporate new computer technologies, such as Global Positioning System (GPS), to improve efficiency. See Intelligent Vehicle Highway Systems. intelligent vehicle highway systems IVHS. Advanced navigational systems which incorporate computer technologies such as Global Positioning System (GPS) and navigational databases. IVHS vehicles include sensors and compasses to interface with the computer control mechanisms and incorporate dead reckoning, maps, and GPS data to control direction and sometimes velocity. IVH systems can be configured for optimum efficiency and safety and could apply extremely well to specially designed mass transit pods or automated commuter systems. Even regular traffic could benefit from IVH systems. See guidance system. intelligent workstation IW. A computer system with advanced features or knowledge bases suitable for business or scientific applications beyond that which a home user might need, for example, but which combines these enhanced features with accessible interface design so that the user need not be a computer expert to take advantage of their features. Intelligent Workstation Architecture IWA. A framework for a computing system with advanced functions or applications such as expert knowledge bases, decision-making algorithms, intelligent search and retrieval functions, and other features that offer advanced computing wrapped up within an interactive, streamlined user interface design. Knowledge

bases for complex data sets (scientific, medical, financial, etc.) that can be accessed and used by computer users with normal computer operating skills, but without computer technical-expert skills are good candidates for development within an IWA framework. intelligibility In communications, the degree to which a message can be understood by sound and context. While articulation refers to the specific ability to make out a communication, intelligibility is the ability to make out sentences and phrases based not only on articulation, but also on context and inference. Thus, a poorly articulated transmission might still be decipherable in context, especially when enough information is given to figure out the nature of the communication. Intelligibility does not require perfect articulation or good fidelity. If a listener hears “Rog...ov....out” at the end of a CB radio conversation with a lot of noise on the line, it is still intelligible as “Roger, over and out” to an experienced radio operator. See articulation, fidelity. International Federation for Information Processing IFIP. An international, nongovernmental, nonprofit organization comprised of organizations in the field of information processing. IFIP was established in 1960 under UNESCO as a result of discussions at the World Computer Congress, Paris, 1959. IFIP supports and promotes the research and development of information technologies for the benefit of all people. It hosts a number of Technical Committees to help fulfil these aims. http://www.ifip.or.at/ INTELSAT International Telecommunications Satellites. The largest commercial not-for-profit satellite communications services provider, founded in 1964. INTELSAT is a cooperative of more than 140 member nations and has 20 communications satellites in geostationary orbit, with further launches planned. INTELSAT operates as a wholesaler, with subscribers, many of them major broadcasting and telephone companies, paying for services according to their type and duration. INTELSAT lays claim to having launched the world’s first commercial communications satellite in 1965 (Early Bird) and the first global communications system in 1969. In 1980, they launched INTELSAT V, the first to use dual-polarization transmissions equipment. INTELSAT VI was a subsequent series of five satellites built by Hughes Aircraft Company. In 1995, INTELSAT began providing global Internet access services through its satellite system. See Early Bird. http://www.intelsat.int/ Intelsat Business Service IBS. A commercial telecommunications service based on the INTELSAT satellite communications capabilities. IBS provides almost 10,000 communications channels for a wide variety of services, including voice, facsimile, data, video conferencing, and telex. Inter Exchange Carrier IEC, IXC. A telephony service provider permitted to provide long-distance services between Local Access and Transport Areas (LATAs), but not within a LATA region. It is also often written as Interexchange Carrier. The category

is important as IECs are bound by a number of regulations to support their provision of services while still safeguarding competitive opportunities for other telecommunications providers who do not fit the definition for IECs. See Local Exchange Carrier. inter- Prefix for between, usually between external and internal systems.

Top: An artist’s concept of INTELSAT VI in orbit. Bottom: The actual INTELSAT VI satellite just following capture by mission STS-49 Space Shuttle crew members in May 1992. The 40-foot tall satellite weighing 4.5 tons was retrieved on the third attempt. [NASA/ Johnson Space Center images.]

Inter-Access Point Protocol IAPP. A specification developed by Lucent Technologies, Aironet Wireless Communications, and Digital Ocean, IAPP is a

means for different vendors to communicate with one another through roaming wireless mobile communications. IAPP describes a backbone-based handover process for mobile stations when implemented in conjunction with the IEEE 802.11 standard. interactive 1. Reciprocal communication, that is, with a back-and-forth, or query-and-answer character. 2. Software which responds to the individual’s input, usually in realtime or near realtime, as in multimedia applications. Video games are highly interactive, whereas archive searches over the Internet may be extremely slow (sophisticated searches can take days). Depending upon the circumstances, programs with slow interactivity may be better processed as batch files. Contrast with batch processing. interactive asynchronous communications IAC. A means of interactively communicating over an asynchronous network connection that allows control of and communication with devices such as a computer modem over a serial connection. Typically the transmission line (e.g., serial line) will be initialized to set up communications parameters before carrying out interactive communications. IAC is useful in situations where the status and operating parameters of a device are broadcast back to the user. Interactive Media Alliance, The TIMA. A nonprofit professional organization supporting various levels of technical and artistic expertise. TIMA fosters the exchange of ideas and knowledge regarding interactive media and promotes the advancement of the technology. TIMA is affiliated with the Technology Association of Georgia. http://www.tima.org/ interactive television Interactive TV, I-TV, ITV. TV broadcasting configured to provide a two-way dialog between the user and the broadcaster, enabled by computerization and two-way transmission circuits. Interactive TV has been implemented in a number of ways since the late 1970s, from educational programming to interactive music concerts and on-demand video, but the potential of this technology has only been hinted at so far. One of the earliest interactive TV networks was the QUBE system from Warner Communications, which was first tested in Columbus, Ohio. Time Warner developed subsequent versions of this technology. Depending upon how it is implemented, interactive TV has been of more interest to educators than traditional passive-interactive TV for distance and selfdirected education. See QUBE. Interactive Television Association See Association for Interactive Media. interactive video services IVS. Interactive video, in its broadest sense, is public or private image and sound broadcasting through public or private networks that is available upon request by the user. Due to the convergence of broadcast and computer technologies, it is now feasible to provide partial- and full-service interactive video services through a number of transmissions media: twisted copper pair, coaxial cable, fiber optic cable, and wireless. However, with the exception of fiber optic cable, the use of

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existing technologies, which were designed for other services, means that none of them are ideally configured for IVS, and vendors are hurrying to find ways to deploy services ahead of their competitors. Thus, a variety of technologies are emerging, in spite of the fact that the marketability of these services is not yet fully proven. Interactive video services potentially include games, movies, and specialized channeling, such as stock quotations and industry-specific news. Some of these have been tried with varying success in different industries and regions, and some companies are devising ways to offer them over the Internet. interactive voice response IVR. Systems that respond to voice commands or voice characteristics and may also prompt the user for further information or clarification. Phone systems that can recognize and respond to simple spoken commands are becoming more common, and software programs can interpret spoken commands and prompt users through synthesized speech. Interagency Management Council for Federal Communications IMC. A representative body for telecommunications executives at key U.S. Federal agencies, including the Department of Commerce, the Department of Defense, the Department of Education, the Department of Justice, NASA, the U.S. Postal Service, and others. It was established to provide a forum for participation in the planning and administration of the General Services Administration’s long-distance telecommunications services provided through the FTS2000 program. Since then, it has become a focal point for the development and administration of Federal technology programs. interapplication communications IAC. A transparent means of intercommunication between computer software applications (e.g., between a word processor and drawing program). A similar concept was dubbed Compound Data Architecture (CDA) by Digital Equipment Corporation (DEC). The concept is now frequently implemented in layered architectures on multitasking systems, but in the early 1990s, surprisingly, it was not prevalent on desktop systems. Once a user has experienced the ease of moving around data and images among different types of applications or among applications from different vendors, it’s hard to go back. Intercarrier Interface ICI. One of the two interface ports of XA-SMDS systems which is used to specify how the carrier switch sends and receives data from an Interexchange Carrier’s (IXC’s) SMDS network. The other interface is the Subscriber Network Interface (SNI). See Exchange Access SMDS. Intercast An Intel term for technology that allows a consumer to interface the TV set with a computer hooked up to the Internet, to receive “push technology” Webcasts or Netcasts, that is, digital broadcasts of information and entertainment transmitted over the Web rather than through television broadcast airwaves or television cable services. The digital information from the Web is displayed in the blanking spaces of the TV signals, so the TV can still receive

normal TV broadcasts in addition to displaying Intercasts. See Webcast. Intercept Service A service in which a call to a changed or disconnected number is routed to a recording or, if a recording is not available, to an Intercept operator. In the case of the latter, the caller will be verbally asked for the destination number and the operator will attempt to complete the call. Interchange A commercial Internet connection service from Ziff-Davis, similar to some of the other large Internet Service provisions, but with a slightly more technological slant. Interchange Carrier IC. A common telecommunications carrier that provides inter- or intra-LATA services through local public exchanges according to definitions and regulatory guidelines established by the Federal Communications Commission (FCC) and the Telecommunications Act. See Inter Exchange Carrier. Interchange Format See Rich Text Format. intercom abbrev. intercommunication, intercommunicator. A set of at least two devices, minimally a transmitter (with a microphone) and receiver (with a speaker) or two transceivers, over which remote communication can take place in at least one direction. Most intercoms are audio only, but audio/ visual intercoms are becoming more prevalent as the technology becomes more readily available. Intercoms can generally be categorized as wired or wireless. Wired intercoms sometimes use existing wiring (e.g., doorbell wires in the walls of houses). Wireless intercoms use broadcast frequencies sent through the air or sometimes through building wiring using the AC sockets as an interface to the wiring for better transmission. Many wired and wireless intercom speakers are wall mounted, like the PA systems in schools or hospitals, and the transmitter may be attached to a handheld microphone or operated through a telephone handset. Baby monitors are a type of wireless mobile intercom, in which one unit is placed near the baby and the other is placed near the parents or babysitter or attached to their clothing so they can move around. Intercoms are often incorporated into phone systems, so that the handset or speakerphone is the transmitter and the receiver is a speakerphone on another console (or on several consoles in broadcast mode). Wireless intercoms interlink by broadcasting radio waves. Since broadcast power and frequencies are strictly regulated by the FCC, intercoms must conform to regulatory guidelines to ensure that they don’t interfere with other broadcasts (your neighbor’s favorite radio show, for example) or with other appliances. Thus, intercoms must be set within specific frequency ranges and must use low-power output. Most home and office wireless intercoms operate in the 900-MHz or 2.4-GHz frequency ranges up to about 100 feet. The distinction between wireless intercoms and wireless radios is not a hard and fast one; there is overlap

in capabilities between sophisticated intercoms and simple radio systems. However, the main difference is in ease of use. Intercoms and basic two-way shortdistance radios tend to be unlicensed push-button devices, whereas wireless radios tend to be licensed devices, some requiring a higher level of expertise to operate. In this sense, a computer videoconferencing system can be called an intercom system. Once the software application is installed and launched, the user need only sit in front of a microphone and small camera in order to communicate with the person at the other end of the connection. No sophisticated skills are needed and even the push-button aspect of the communication has been eliminated. Since videoconferencing systems aren’t subject to the same distance restrictions as low-power wireless devices, it’s possible that small flat-screen monitors with built-in speakers will eventually replace traditional intercoms. Parents will be able to readily see what their kids are doing in daycare or at school. Friends can keep in touch without making long-distance calls. Business associates can discuss important projects or interact in meetings from home or a remote office (or from the road with a wireless modem). When high-speed communications become available to a majority of users, Internet intercoms may well become one of the most prevalent telecommunications technologies. See public address system, videoconferencing. Interdepartment Radio Advisory Council IRAC. An assemblage of committees, subcommittees, and working groups providing expertise and notification to the International Telecommunication Union (ITU) regarding the allocation and management of radio frequency spectra. IRAC develops procedures, processes requests, and assists in assigning frequencies to U.S. Government radio stations. IRAC includes the Frequency Assignment Subcommittee (FAS), the Spectrum Planning Subcommittee (SPS), the Technical Subcommittee (TSC), the Radio Conference Subcommittee (RCS), and the International Notification Group. Interexchange Carrier Compatibility Forum ICCF. An organization that developed an expansion plan for telephony Carrier Identification Codes (CICs) when they became scarce in the late 1980s. The ICCF also served as a liaison in standardization efforts for fiber interconnectivity in the mid-1980s. interface n. A hardware connection, or logical connection or translation point between two or more devices or transmissions media. Interfaces are an intrinsic part of interconnected computers, peripherals, and networks. Almost every aspect of data and electrical connections in the telecommunications industry uses a different format or version of a format, and the interface is the point at which all these different hardware and software junctions come together. Common electronic interfaces include docking bays, cradles, cable connectors, peripheral card connectors, card slots, and chip sockets. interface, human-machine n. The point of contact or translation between humans and machines.

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A hardware interface is a device or system that translates human movement, speech, or sensory output into impulses (usually electromagnetic or mechanical, though chemical interfaces also exist) that the machine or computer device can interpret and compute into data and instructions or, conversely, that translates machine signals into sensory output or information meaningful to humans. Human-machine interfaces come in many varieties, including digital, analog, mechanical, chemical, or a mixture of these. Examples of hardware input interfaces include microphones, keyboards, joysticks, temperature sensors, serial connectors, video cams, data gloves, and pressure pads. Hardware output interfaces include monitors, speakers, pulsing lights, thermostat controllers, infrared device controllers, and more. • A software interface is a system of algorithmically-coded procedures and functions intended to meaningfully communicate information and options to humans and/or to interpret human communication and sensory input into signals that can be translated into machine instructions. Common software interface conventions include the use of textual queries and responses, graphical pointers, folders, menus, and other culturally meaningful icons that indicate the state of the device, availability of services, current point in a process, etc. Human-machine interfaces evolve through a system of trial-and-error combined with the sometimes idiosyncratic preferences of the people who design the applications or market the devices to the general public. At the present time, software interfaces are often developed intuitively by computer programmers with little or no input from users even though they are intended to satisfy the needs of a broad spectrum of people, rather than the more individual needs and preferences of the programmer, in order to produce products with commercial viability. Unfortunately, interfaces become entrenched even if they are no longer appropriate or practical. Early versions of a technology are often designed to overcome pioneering design limitations. As the limitations are overcome, the increasingly inefficient interface may be retained because users have become accustomed to it or because it is expensive to change production lines. The QWERTY typewriter keyboard layout is a good example. It was designed for historic manual typewriters and laid out with the letters organized so they would slow down the typist to help prevent jamming that occurred with old-style mechanical keys. When electric typewriters and computer keyboards were developed without the jamming problems, the QWERTY layout was retained even though the original reason for the layout became irrelevant. The concept of the interface is an important one as it influences how comfortably and efficiently humans can utilize a technology. Ease of use and interface design are essential to the success and proliferation

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of many telecommunications products. Interface design also reveals priorities; sometimes humans are expected to adapt to the limitations of a technology rather than the technology being designed to serve the needs of humans. Interface Control Application Programming Interface ICAPI. A telecommunications call control library that facilitates network interface access for T1 robbed-bit signaling systems or T1/E1 CAS. It fits between the operating device drivers and the application. There are similar call libraries for ISDN and ANAPI. An ICAPI protocol uses bit transitions and in-band signaling to establish calls and transmit call information. Events and channel states may be logged. Interface Data Unit IDU. In ATM networking, interface control information transferred to and from the upper layer in one interaction across the layer. A service data unit (SDU) may be passed across ATM Adaptation Layer 5 (AAL5) as an IDU corresponding to one protocol data unit (DPDU) in a one-toone correspondence or, depending upon the type of service (e.g., message or streaming mode), the SDU may also be passed across AAL5 in more than one IDU. Interface Device In Frame Relay networks, the Interface Device provides a link between an end device and the network through encapsulation. See encapsulation, Frame Relay Capable Interface Device. interference Extraneous, unwanted signals that hinder transmission or perception of the desired signal. Types of interference include noise, static, pops, crackles, echo, babble, chatter, crosstalk, cosmic noise, and background noise. See individual entries in this dictionary for details. interference guard band See guard band. interferometer Because of its wavelike properties, a beam of coherent light can be split and realigned in such a way that factors that interfere with one of the beams can be detected when compared to an unimpeded reference beam or, more simply, the split beams can be compared to detect subtle changes to one or more of the beams. Thus, a device that detects and displays interference between two or more light wave trains and, optionally, compares wavelengths against reference displacements is called an interferometer. Because light technologies can be very precise compared to mechanical devices they can be used for very fine detection and calibration. The interference pattern information derived from an interferometer is useful in measurement or calibration, for example, to determine angular positions in satellite tracking. There are a variety of types of interferometers, ranging in complexity from simple models that can be built by students to more sophisticated models that incorporate integrated circuit (IC) concepts. Interferometers have been proposed as instruments to determine electrical states in silicon-based integrated circuits (ICs) and as diagnostic instruments for optical computer networks. One interesting application is the light-in-flight speckle interferometer presented

by Swedish engineers as a means to evaluate 3D shapes by using ultrashort laser light pulses. On a software level, algorithms for phase-stepping interferometry have been developed by Chinese scientists. Interferometers are important in many aspects of astronomy. Not only are telescopes based on interferometric principles, but Fizeau interferometers (FIs) are included as payloads on space missions, selected for their accuracy and capability of sensing over a wide field. The Global Astrometric Interferometer for Astrophysics (GAIA) mission, for example, includes three stacked, mechanically connected FIs designed to observe about 50 million stars. Historic interferometers were based upon noncoherent, mixed-wavelength light, while interferometers developed since the invention of lasers typically use coherent, nearly monochromatic light. Here is a short list of some common, representative interferometers used in remote sensing, and component fabrication and testing applications relevant to telecommunications: Fabry-Perot interferometer FPI. A high-resolution interferometer utilizing multiple reflections from two proximate reflective surfaces. A FabryPerot interferometer with Michelson-type mechanical motion was designed by the National Bureau of Standards (NBS) in the early 1900s to make the first precision measurements of wavelengths published by the NBS. In cooperation with the University of Pittsburgh, MIT uses this type of interferometer with a cooled gallium-arsenide photocathode photomultiplier as a detector, with a computer as a controller, for night sky observations. There are FPIs installed in the Antarctic, Norway, and many other locations to remotely sense upper atmosphere wind and temperature conditions. Doppler concepts are incorporated into the sensor readings for meteorological observations. Fabry-Perot filters have also been suggested by Wickham et al., for use as sub-band tuning mechanisms (in conjunction with Bragg reflection gratings) for optically channelizing radio frequency (RF) signals for spectral analysis of the very high frequencies now used for communications signals. Bragg reflection gratings and FP filters have further been described by Bao et al., as a mechanism for determining wavelengths of transmitted or reflected light through a calibrated wavelength reference, thus creating a reference system. Fizeau interferometer FI. A basic type of image plane interferometer that is useful for noncontact testing of surface characteristics and for telescope design. The Fizeau interferometer produces a direct image from the source and does not incorporate the same degree of beam diversion characteristics as the other interferometers mentioned here. The FI is used in many astrophysical applications. More recent digital phase-shifting FIs have been developed by CSIRO for in-house precision metrology of optical components. Mach-Zehnder interferometer MZI. A historic

interferometer descended from the TwymanGreen interferometer. With improvements, the MZI is still in common use as a calibration and diagnostic instrument. It is most often used in aerodynamics, thermal transfer, and plasma physics, but is also being studied in fiber optics research. The MZI is favored for many educational applications, as a basic model can be built by students in a rectangular or parallelogram configuration. Depending upon the alignment of the reflecting surfaces, interference fringes may or may not be produced and, by controlling the length of the optical path, phase shifts can be introduced in a controlled manner. The extent of the shift provides a means to monitor relative changes in the optical path, thus providing useful measurement information. The beam phasing characteristics of an MZI can also be modeled in computer software. The MZI is both simple and sophisticated, depending upon how it is implemented. It is not only a good student project, but also has been proposed for use as an atomic interferometer. MZIs are useful in the fabrication and testing of components and various sensors used in telecommunications. They have also been incorporated into integrated circuits for converting optical wavelengths and have been developed into directional coupler switches. Michelson interferometer MI. A basic interferometer developed by A.A. Michelson to conduct the Michelson-Morley experiment in the 1880s. The scientists used the interferometer to determine whether a theoretical medium called the aether existed and could be detected. Michelson received a Nobel Prize in 1907 for his discoveries in optical science. In a Michelson interferometer, a monochromatic point light beam is split in two by a partially reflective material, such that one beam continues in the original direction, and the other is reflected (usually 90°) off the original course. The beams are recombined with the resulting interference patterns displayed on a screen. These are derived from the wavelike characteristics of light and can be analyzed to determine vibrational or thermal effects, which are useful in fabrication and diagnostics. The image in a Michelson interferometer is not viewed directly as in a Fizeau interferometer but, in viewing instruments such as telescopes, can be reconstructed. By calibrating the MI with a known reference, the wavelengths of other unknown materials (e.g., gases around astronomical bodies) can be studied through known interference characteristics. MIs are also used to develop standards in atomic lengths. Twyman-Green interferometer TGI. A basic type of interferometer is used as an optical fabrication and diagnostic tool, developed by Frank Twyman and Arthur Green in the early 1900s. The modern TGI is based on a monochromatic point light source at the focal point of a lens. By reveal-

ing patterns of optical interference resulting from unequal light paths, the TGI can be used to assess optical surface characteristics such as the flatness of a surface, performance of a component (e.g., a prism), or deviation from a reference shape. See beam splitter, coherent light. Interim Local Management Interface ILMI. A means of providing an ATM device with status and configuration information about virtual connections, and the registered ATM prefixes, addresses, services, and capabilities available at its ATM Interfaces through the Simple Network Management Protocol (SNMP) and an ATM Interface Management Information Base (MIB). ILMI is an open protocol that was developed as an interim solution by the ATM Forum in the mid-1990s to enable the exchange of UNI management information through direct encapsulation over ATM adaptation layer 5 (AAL5). However, the interim designation was dropped. ILMI is not universally implemented and meta-signaling may be used to serve this purpose on some systems. Interim Number Portability INP. The use of various telephone subscriber services, such as call forwarding, call routing, and call addressing, to allow a call to be redirected to another location, usually on a temporary basis. interior In ATM networking, interior denotes that an item such as a link, address, or node is inside a PNNI routing domain. Interior Gateway Protocol IGP. A family of network routing protocols for exchanging information with other routers and switches on the same system. When changes occur in the organization of the network, these changes are communicated to the routers, so the routing table databases may be revised accordingly. Interior Gateway Routing Protocol IGRP. A Cisco Systems proprietary multipath routing protocol developed in the mid-1980s for routing within autonomous systems. Since then, the protocol has been further developed and many users have replaced Routing Information Protocol (RIP) with IGRP to run on large, heterogenous networks, like the Internet. IGRP was intended to run in a variety of network environments and enhanced IGRP has been developed to support TCP/IP, IPX, and AppleTalk. IGRP-enabled routers send some or all of their routing tables to neighboring routers at regular intervals, a process that also enables distances among nodes to be calculated as the information propagates out through the network. interlace A system used in frame-based video image display to display images in two-frame passes, with one pass imaging the odd lines and the next the even lines (or vice-versa), in an alternating pattern. Thus, in NTSC, for example, an interlaced screen is imaged in two fields of 262.5 lines (to make up the full 525 scan lines), each field taking 1/60 of a second. Some flicker can be seen on an interlaced display, so noninterlaced monitors, including multisync monitors, have become prevalent on computer systems. Generally, the faster the refresh, the more stable

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the image. See cathode-ray tube, field, frame, interleave, multisync, scan, scanning rate. interleave v.t. 1. To arrange in alternating layers, rows/columns, or time slices. 2. In concurrent programming, a logical means to execute sequences in order to analyze the correctness of concurrent programs. 3. In networking, to transmit pulses through a single path through time-division from more than one source. 4. In graphics file storage and display, a means of arranging the image data so that all odd lines of the image and all even lines of the image are stored or displayed as a group. 5. In magnetic and magneto-optical data storage, a means and pattern of storing information on a disk so that the physical characteristics of the read/write sequence are accommodated without the drive head needing to “backtrack” to find the next section of data. 6. In multimedia applications, a means of slicing up the recording space so that different media (sound, graphics, etc.) are laid down in strips or sections on the tape or disc. 7. A data transmission error-correcting technique in which code symbols are arranged in an interleaved pattern before transmission and reassembled upon receipt. interleaved video A video display in which a frame is constructed and displayed by alternately scanning all even lines and then all odd lines. This system of display is commonly seen on televisions screens and on some NTSC-compatible computer screens. A certain amount of flicker is usually noticeable on interleaved displays. See interlace. intermediate frequency IF. In heterodyne receivers, the beat frequency created as a result of the difference between a locally generated signal and the incoming radio signal. See beat frequency. Intermediate Signaling Network Identification In Signaling System 7 (SS7), a capability that allows an application process in the originating network to specify intermediate signaling networks for noncircuit-associated signaling messages, and/or to notify an application process in the destination network about intermediate signaling networks. intermittent errors Fault conditions that happen occasionally, sometimes without apparent pattern, or occur from specific causes that happen seldom or irregularly. Difficult to anticipate and diagnose, intermittent problems are often not alleviated until a program has been run hundreds of times or a computer or phone network has negotiated thousands of calls. internal modem A computer modem installed inside a larger system that is utilizing the modem. Internal modems are usually powered by the system in which they are housed and usually take the form of small PC boards or very small PCMCIA cards. Sometimes referred to tongue-in-cheek as “infernal modems,” internal modems can be finicky to install in systems with several peripherals that require IRQs. Internal modems are convenient in that they are out of sight and mind, and don’t take up extra space – a real plus on laptop computers. They have disadvantages as well, as they are often machine- or platformspecific and often can’t be reinstalled in a new computer of a different type, as can most external

modems. External modems are easier to swap among systems, can be shared by a number of users through a switcher, and usually have status lights that are handy diagnostic tools. Since most internal modems install in a slot that faces the back of the system, they often don’t provide status lights. In general, people prefer internal modems on small mobile devices and external modems on desktop systems or systems with shared resources. International Ad Hoc Committee IAHC. See Internet International Ad Hoc Committee. International Alphabet No. 2 An older alphabetic coding system of using equal-duration pulses of negative and positive volts (called marks and spaces) in groups of five, to represent character signals. The beginning and end of each character was signaled by a start signal and a stop signal. The use of five elements in two possible polarities results in 25 or 32 character encodings. Even for a basic alphabet, this was somewhat limited, and schemes for doubling the number by allowing a code to represent one of two characters were devised. This is not unlike what happened later with computer character codes. International Alphabets evolved into ASCII and became widely implemented on computers, but there were only 128 characters, insufficient for foreign languages, graphics, or mathematical symbols. Many developers added 128 codes for a total of 256 characters and called it “extended ASCII.” Technically, the extra codes weren’t standard ASCII and were not consistent across platforms. In the early 1980s, extended character sets were implemented on many personal computer systems as separate banks, thus ASCII and so-called extended ASCII characters couldn’t be mixed. In the mid-1980s, the Macintosh and Amiga operating systems introduced individual addressing of characters along with graphical character display. These innovations greatly facilitated the development of foreign character sets, including Cyrillic and Asian languages. See Appendix K for an ASCII chart. See ASCII, Unicode. International Amateur Radio Union IARU. A regulatory agency and proponent of world amateur radio activity established in France in 1925. Amateur radio organizations throughout the world interact with a high degree of cooperation and communications. The IARU is essentially to global amateur radio communications what the American Relay Radio League (ARRL) is to American amateur radio. The IARU is organized into three regional organizations that parallel administrative divisions of the International Telecommunication Union (ITU). See American Relay Radio League. http://www.iaru.org/ International Atomic Time, Temps Atomique International TIA. An atomic time scale based on the coordinated efforts of more than 200 atomic clocks from more than 50 centers from around the world, which are maintained in France by the Bureau International des Pods et Mesures. Unlike the Coordinated Universal Time (UTC), which is adjusted occasionally in leap seconds to maintain some coordination with the Earth’s axis rotation, TIA is not

adjusted, but remains consistent with atomic time scales. Otherwise, TIA and UTC are very similar. See atomic clock, Coordinated Universal Time. International Business Machines IBM. In the late 1800s, Herman Hollerith, an American engineer, evolved the concept of punched cards as a storage medium and applied it to the development of a tabulating machine, an early computer that could be used to store and process information in categories. This resulted in Hollerith cards, Hollerith code, and a machine which could tabulate the vast amount of census data gathered at regular intervals in the United States. The tabulating machine dramatically improved the efficiency of storing and analyzing census data, and Hollerith formed a company called the Tabulating Machine Company. This later merged with several other companies to form the ComputerTabulating-Recording Company, which sold a wide range of industrial products. Thomas J. Watson, Sr. left NCR to join the company as general manager in 1914, and remained with the company for over four decades, eventually passing on the position to his son, Thomas J. Watson, Jr. On Valentine’s Day, in 1924, the name of the company changed to International Business Machines Corporation. IBM became an enormously influential company in the business and computing market, and funded or partially funded the research and development of several historic room-sized computing machines. IBM’s research laboratory has contributed a great legacy of original and fundamental scientific discoveries of interest both inside and outside the computing industry. IBM inventions are awarded more than 1000 patents per year; in other words, IBM develops as many unique inventions in a single year as the best individual inventors of the 1800s developed in their entire lifetimes. In 1975, IBM released its first microcomputer, the IBM 5100; it was not a commercial success, and it was not until 5 years later that the first of the long IBM PC line was introduced to the public. This time sales were good, particularly in the business market, and IBM and IBM-licensed personal computer technology became the most common platform for desktop computing. See Hollerith, Herman; IBM Personal Computer, Jacquard loom. International Center for Technology Assessment ICTA. A nonprofit, bipartisan organization dedicated to helping government officials and the public in understanding technology and how it affects human society and the environment. ICTA explores and communicates the social, economic, ethical, political, and environmental impacts related to the manufacture, distribution, and application of technologies. ICTA also uses legal petitions, comments, and litigation to fight against harmful deployment of technology. http://www.icta.org/ International Commission on Technology and Accessibility ICTA. A commission to explore developments in technology that may assist people with disabilities and to promote and disseminate their understanding and use. ICTA was founded in the 1960s in Sweden in conjunction with Rehabilitation

International (RI) and the Swedish Handicapped Institute. In 1969 ICTA and RI developed and adopted the International Symbol of Access (ISA). http://www.ictaglobal.org/ International Correspondence Chess Federation ICCF. This is one of the more interesting historic bodies using telecommunications to enhance gaming communications. The ICCF has evolved from the Internationaler Fernschachbund, founded in 1928, which was succeeded by the International Correspondence Chess Association, in 1945, to become the ICCF in 1951. Correspondence chess hasn’t only been conducted through postal mail services. ICCF members and chess players in general have always been technology conscious and have enjoyed their matches through the use of homing pigeons, telegrams, trains, planes, computer modems, and highspeed connections to the Internet. International Data Encryption Algorithm IDEA. A European-designed, 128-bit, single-key encryption algorithm used for data security. It has been incorporated into Pretty Good Privacy (PGP) partly because it doesn’t have the same U.S. export restrictions as other encryption algorithms. Use of IDEA is license-free for noncommercial use. See encryption, Pretty Good Privacy. International Development Markup Language IDML. An Internet protocol and associated set of standards to facilitate development in a global context. In 1998, the Development Markup Language (DML) was seen as a means to support the markup of information on computer networks that describe developmental activities and mandatory data elements described by relevant standards. It was intended to be consistent with other metadata schemes and capable of multilingual markup. In February 1999, DML was renamed IDML. The IDML Working Group was formed to develop recommendations and a process for electing an IDML Advisory Group. It is recommended that XML be used for Site Description files even though other formats may be used. Extended IDML is a superset of the Core Activity Schema with additional audit trail and informational items. IDML was established as a pilot standards-track candidate in early 2001. See Extensible Markup Language, IDML Initiative. International Electrotechnical Commission IEC. An international standards-development and recommending body, founded in 1906 as a result of a 1904 resolution at the Electrical Congress. The IEC publishes standards for electrical, electronic, magnetic, and related technologies and promotes cooperation among member countries. IEC standards form the core of the World Trade Organization’s Agreement on Technical Barriers to Trade (TBT). Hundreds of technical committees and working groups carry out the mission of the IEC. Technical committee papers are submitted to a full-member National Committee members’ vote in preparation for approval as international standards. http://www.iec.ch/ International Engineering Consortium IEC. A nonprofit professional organization supporting engineering research and education sponsored by

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universities and engineering societies, founded in 1944. The focus of the organization has broadened from a national to international purview and from electronics to information engineering. IEC sponsors courses, conferences, virtual exhibits, and a number of publications. http://www.iec.org/ International Federation for Information Processing IFIP. A nonprofit, nongovernmental, information processing research organization. IFIP was established in 1960 under the auspices of UNESCO after the first World Computer Congress of 1959. A number of technical committees provide expertise on technological matters. http://www.ifip.or.at/ International Forum on the White Paper IFWP. An international series of workshops intended to bring together professionals and experts in law to respond to White Paper recommendations for assigned numbers on the Internet, founded in June 1998. The process of open discussion and the goal of selfregulation were key aspects of these proceedings. The Internet community believed that it was possible for those in the industry to produce a viable system for assigning Internet addresses without government takeover of the process and used the Internet itself as an important venue for meetings, opinions, and sometimes heated debates over how addresses would be allocated and assigned. As a result of initial discussions, a California nonprofit public benefit corporation called the Internet Corporation for Assigned Names and Numbers (ICANN) was tendered as a draft recommendation as a means to coordinate the administration of Internet domain names and Internet Protocol (IP) addresses. The draft proposal, jointly presented by Network Solutions, Inc. and the Internet Assigned Numbers Authority (IANA), was discussed in September 1998, by IFWP with regard to how it fell within a model of common principles and structure specified by the U.S. Department of Commerce Statement of Policy on the Management of Internet Names and Addresses. Three proposals were presented to the Deptartment of Commerce in October 1998, by different groups, and testimony was presented on transferring the Domain Name System to the private sector. ICANN’s bylaws and its first public meeting were held in November 1998. See Internet Assigned Numbers Authority, Internet Corporation for Assigned Names and Numbers, InterNIC. International Frequency Regulation Board IFRB. An agency established by the International Telegraph Union in 1868 to manage the broadcast frequency spectrum. In 1912, the IFRB’s Table of Frequency Allocations became mandatory. The frequency allocation table specified frequency bands for specific uses in order to minimize interference among stations. See Federal Communications Commission, International Telegraph Union. International Information Systems Security Certification Consortium ISC2. A nonprofit corporation established in 1989 to develop certification programs for security professionals working in the informa-

tions services field. http://www.isc2.org/ International Intellectual Capital Codes Association IICCA. A not-for-profit association tasked with defining a comprehensive lexicon of skills of interest to industries and users for employment/employee matching through the iCAP Catalog and the Intellectual Capital Inventory (iCAP) system. IICCA is responsible for the development, maintenance, and uniformity of the iCAP Catalog. See iCAP. International Internet Association A fee-based Internet service that provides access to more than 20,000 databases from around the world. International Internet Industrial Association IIIA. A professional association of Internet Service Providers (ISPs), Web developers, software developers and others directly influencing or being influenced by the development of the Internet. The IIIA is concerned with issues such as the addition of a larger available base of international Top Level Domains (TLDs). http://www.iiia.org/, http://www.iatld.org/ International Mobile Subscriber Identity IMSI. An ITU-T identification number assigned by a wireless carrier to a mobile station to uniquely identify the station locally and internationally. International Network for Development Information Exchange INDIX. A coalition for organizations involved in development in information exchange. INDIX developed the CEFDA standards for data exchange and participated in the development of the International Development Markup Language (IDML). See IDML Initiative. http://www.indix.org/ International Organization for Standardization (International Standards Organization) ISO. An important international standards-setting body which has produced many of the specifications and documents used by telecommunications professionals. ISO is familiar to many through its ISO-9000 series of quality assurance specifications. ISO-9000 standards can be summarized as “Say what you do, then do what you say, and get it certified, if necessary.” http://www.iso.ch/ International Radio Consultative Committee CCIR. A standards and regulatory-recommending body founded in 1927, descending from the International Radiotelegraph Conference in 1906, in connection with the International Telegraph Union. This organization was formed in response to public broadcasts over radio waves in the early 1920s. See International Telecommunication Union (ITU-R). International Radiotelegraphic Convention One of the early international gatherings, resulting from the growth of telegraphy, resulted in a multinational consent agreement regarding Protocol and Service Regulations that was documented in November 1906. The convention was to be entered into force in July 1908 by Great Britain, Germany, Austria, Hungary, Denmark, and a number of other European nations, Japan, Argentine Republic, Brazil, Chili, Uruguay, Russia, Turkey, Persia (now Iran), the U.S., and Mexico. The convention defined various types of telegraphic establishments common at the time, including coast

and ship stations, and delineated operating parameters to ensure cooperation in the use of telegraphic transmissions and designated frequencies, responses to distress signals, telegraphic charges, and other telegraphic matters of international importance. See Radio Communication Laws of the United States. International Society for Measurement and Control ISMC. Formerly the Instrumentation Society of America (ISA), ISMC is a nonprofit professional organization supporting manufacturers and engineers involved in the theory, design, manufacture, and use of measurement and control instruments and computer systems. See Instrumentation, Systems, and Automation Society. http:/www.isa.org/, http://www.isaca.com/ International Special Committee on Radio Interference CISPR. An international committee with members from a broad spectrum of the radio communications/engineering industry who work to promote international agreement on aspects of radio interference to facilitate international trade. CISPR is composed of a number of international organizations plus each National Committee of the International Electrotechnical Commission (IEC). Through conferences and subcommittees, CISPR promotes and produces information guidelines, statistical methods, and standards related to the protection of radio reception from interference from consumer goods and industrial equipment, electrical supply systems, and broadcasting equipment. CISPR establishes limits and requirements for immunity to interference and takes into consideration safety regulations as they affect interference suppression of electrical equipment. Of particular interest to telecommunications are CISPR publications on electromagnetic compatibility (EMC) and emission standards. http://www.iec.ch/ International Speech Communication Association ISCA. A nonprofit organization promoting international speech communication, science, and technology originally founded in 1988 as the European Speech Communication Association, ISCA was established in 1999. It is now an independent, self-supporting organization. ISCA’s interests include research in synthetic speech development and processing. http://www.isca-speech.org/ International Switching Center ISC. A gateway exchange whose function is to switch telecommunications traffic between national and international countries. International Telecommunication Regulations ITR. A set of international regulations intended to supplement the International Telecommunication Convention while also recognizing the individual rights of nations to regulate their telecommunications sectors. The ITR framework seeks to promote the efficiency, harmony, and evolution of global telecommunications through established general principles for international telecommunication transport media and services offered to the public. Draft proposals of the ITR were presented at the world Administrative Telegraph and Telephone Conference in Melbourne, Australia, in 1988 per a resolution of the

Plenipotentiary Conference of the International Telecommunication Union (ITU). International Telecommunication Union ITU. A significant, influential, global United Nations standards agency descended from the International Telegraph Union. The ITU, headquartered in Geneva, Switzerland, provides extensive publications, promotes communication, sponsors international meetings and conferences, disseminates news, and develops standards and regulations. The ITU oversees a number of subgroups, called sectors (see chart). The ITU is involved in a number of important communications venues for discussion and the dissemination of findings. Examples include • The publication of the ITU Operational Bulletin every 2 weeks to report on the administrative and operational information exchanged among administrators, service providers, and recognized operating agencies (ROAs); country codes and other statistical indicators are published in conjunction with the bulletin as annexes. • The organization of the World Radiocommunication Conference (WRC) to administer international agreements in wireless telecommunications technologies. • The organization of the World Telecommunications Standardization Assembly to determine needs and priorities related to standards development and dissemination. • The convening of a Plenipotentiary Conference every 4 years (1998, 2002, etc.), an important meeting ground for member states where decisions on direction and policy are made and previous actions reviewed and debated. The 1998 conference was characterized by calls for greater involvement of the private sector in ITU activities. When the council is not convened, administration and oversight of the ITU is handled by the ITU Council. See Telecommunication Standardization Bureau. For a brief description of ITU-T history, see International Telegraph Union. For series lists and individual recommendations, see Appendix C and alphabetized lists under letter designations. http://www.itu.int/ International Telegraph Union ITU. An old and influential organizing and standards-recommending body formed in 1865 when the telecommunications industry was beginning to boom. The ITU was created in response to the need for cooperation and formal agreements related to the installation and use of multinational telegraph systems. Twenty participating countries signed the first International Telegraph Convention. After the invention of the telephone, the Telegraph Union drew up recommendations for legislation governing international telephony. Radio communications began to develop, so the Telegraph Union convened a preliminary radio conference in 1903 leading to the Radio Regulations and founding of the International Radio Consultative Committee (CCIR). In 1934, the name was broadened to International Telecommunication Union. It became an agency of

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the United Nations in October 1947, and the headquarters were transferred from Berne to Geneva in 1948.

ITU-T Subgroups (Sectors) Abbrev. ITU-R

Sector Notes Radiocommunication Sector Descended from the international Radio Consultative Committee (CCIR), this is the arm of the ITU responsible for researching technical and related regulatory issues. It regulates groundand space-based radio frequency telecommunications.

ITU-T

Telecom. Standardization Sector Founded in March 1993, ITU-T replaces the International Telegraph and Telephone Consultative Committee (CCITT). The ITU-T endeavors to ensure efficient and on-time production of high quality standards covering all fields of telecommunications with the exception of radio, which is handled by ITU-R. The work of the ITU-T is handled by numerous study groups and is documented in tens of thousands of papers. Presently more than 2500 standards recommendations are in force that form a framework for global communications.

ITU-D

Telecom. Development Sector Facilitates global telecommunication development by providing organizing and coordinating expertise and assistance. The ITU-D works through conferences, study groups, the Telecommunication Development Advisory Group, and the Telecommunication Development Bureau (BDT).

The Union later became known as the CCITT, as there were a number of CCIs set up for different areas of communication in the 1920s; the CCIT and the CCIF were amalgamated in 1956. In 1992, an important conference took place in which the organization was evaluated with the aim of updating it to align with the complex, changing environment of current and future technologies. The organization has recently been renamed International Telecommunication Union (ITU) because the fundamental objectives of the original organization remain essentially the same today as they were over 100 years ago, and the convergence of the many media and communications technologies through digital transmission has united many formerly

separate areas. (Source: ITU-T Web site history.) In Canada, communication with the ITU is accomplished through the Canadian National Organization for the ITU (CNO/ITU-T) and the Steering Committee on Telecommunications of the CSA (CSA/ SCOT). See International Telecommunication Union; Morse, Samuel B.F. International Traffic in Arms Regulations ITAR. Rules issued by the U.S. State Department, under the authority of the Arms Export Control Act, to control the export/import of defense-related articles and services, including information security systems such as cryptographic systems and TEMPEST suppression technology. International World Wide Web Conference Committee See World Wide Web Conference Committee. internet When spelled with a lowercase “i,” generically refers to an interconnection of two or more data networks. While individual networks may be connected in any number of ways, it is common to interconnect them through the Open Systems Interconnect (OSI) model as it ensures a good level of compatibility with existing technologies and supports interoperability among a variety of types of systems. See Internet. Internet A global communications community of more than 60,000 cooperating networks, evolving in the early 1980s out of ARPANET, now known as the Internet or colloquially as the Net. The Internet consists of a distributed network of tens of millions of computers linked together through small and large communications services providers. By early 1995, the Internet had more than 4 million hosts and the term was officially defined by the Federal Networking Council. The Net is defined in the Telecommunications Act of 1996 and published by the Federal Communications Commission (FCC) as “... the international computer network of both Federal and non-Federal interoperable packet switched data networks.” The evolution of the Net has been influenced by a broad base of technical and lay interests and an equally wide range of commercial and public interests. The vocal promoters of the Net as a universal access communications medium to serve the public good have been joined by commercial interests seeking a way to use the Net to further private and public business interests. In the early days, the Net had a high proportion of users in technical and scientific fields and focused on cooperative communication and research. Since the mid-1990s, an overwhelming influx of commercial vendors has changed the character of the Net, but there has also been a large growth in cooperative nonprofit and community organizations. In 1993, the United Nations and the U.S. White House came online, thus changing the ways to access and think about politics. Global doors have opened up to people doing genealogical studies and people are rediscovering friends they haven’t seen

since elementary school. The phone network is undergoing substantial changes due to competition from long-distance email and chat resources that are available on the Internet without long-distance phone costs. The impact of the Internet on communications venues and global culture is highly significant, and will likely exceed the changes brought about by the industrial revolution. The information glut and impact on personal privacy will be far-reaching as well. Speculations about the emergence of the Net as a form of digital intelligence may not be farfetched, and, with the cooperative communication possible among scientists and interested lay persons, research will move forward at an unprecedented rate. See ARPANET, Telecommunications Act of 1996, RFC 1958. Internet 2 A consortium of more than 100 academic and nonacademic organizations working to develop a vision and implementation plan for the next generation of the Internet on a content and integration level. For information on the technical successor to the current Internet protocols and physical structures, see IPv6. http://www.internet2.edu/ Internet Access Coalition IAC. A lobbying organization that supports universal Internet access and monitors and comments on industry trends in Internet services provision, long-distance access, and other logistical matters that affect the ability of the public to access and utilize Internet services. The IAC sometimes works in cooperation with other organizations such as the Information Technology Association of America (ITAA). Internet Access Provider IAP. A vendor who provides a connection to the Internet in the form of Frame Relay, ISDN, a dialup modem, or other physical or virtual connection, and who may or may not provide additional services, such as email, shell accounts, web hosting, etc. Providers with full services available, rather than just an access port to the Internet, are generally called Internet Services Providers (ISPs). See Internet Services Provider. Internet Activities Board IAB. Established in 1983 to replace the Internet Configuration Control Board, the IAB subsequently came under the umbrella of the Internet Architecture Board. See Internet Architecture Board. Internet Architecture Board IAB. Formerly the Internet Activities Board (and before that, the Internet Configuration Control Board), the IAB is a coordinating and policy-setting board for the Internet Engineering Task Force (IETF) and the Internet Research Task Force (IRTF). All three bodies were combined under the aegis of the Internet Society (ISOC) in the early 1990s and the IAB is now the technical advisor to the Internet Society. See RFC 1358 for a charter of the IAB, and RFC 1160 for a description of its organization and role. See Internet Engineering Task Force (IETF), Request for Comments. http://www.isi.edu/iab/ Internet Assigned Numbers Authority IANA. An organization which, since the early 1980s, has exercised authority over DNS operations, Internet

Protocol (IP) number assignment, Root Name Servers, Request for Comments (RFC) documents, and protocol port number assignments. IANA is the central coordinator for the assignment of unique numbers for Internet protocols and serves as a clearinghouse for this purpose. IANA also provides registration through a central repository for MIME types, that is, data object types identified by a short ASCII string which can be used to provide rich content types in conjunction with electronic mail. Jon Postel has almost single-handedly spearheaded this effort, an enormous contribution by an Internet pioneer involved since the days of the ARPANET. IANA is chartered by the Internet Society (ISOC) and located at the Information Sciences Institute (ISI) of the University of Southern California. See domain name, naming authority, name resolution. http://www.iana.org/ Internet Channel Commerce Connectivity Protocol ICCC. A channel-based connectivity protocol designed to facilitate electronic commerce, initiated by 3Com. ICCC is intended as a scalable, securable, channel-based electronic commerce infrastructure, based upon Extensible Markup Language (XML). Access to ICCC is through popular Internet browsers so that WWW-related Internet commerce applications can be built upon ICCC. The concept is of an application-layer protocol that passes over the wire, to promote interoperability, with transactions accomplished through the widely established HTTP. “Shopping cart” programs on the Web illustrate the general idea of what ICCC is intended to accomplish through a standardized protocol model using existing standardized formats and a server-to-server transfer (rather than through the browser). See Open Buying on the Internet, Open Financial Exchange, Open Trading Protocol. Internet Community at Large ICAL. A project funded by the National Science Foundation Division of Environmental Biology’s Research Collections in Systematics & Ecology Program through the Museum of Paleontology at Berkeley to facilitate development of improved and new modes of communication among museums, donors, and research scientists, utilizing the World Wide Web. The main purpose of the Web project is to help reduce the number of orphaned or underutilized natural history collections. Additional support for ICAL-Entomology was provided by the National Science Foundation through the Bishop Museum. Internet Configuration Control Board ICCB. A regulatory board established by the U.S. DARPA in the late 1970s to facilitate the creation of gateways between hosts and the network. The ICCB was replaced by the Internet Activities Board in 1983. See ARPANET, DARPANET. Internet Control Message Protocol ICMP. A significant protocol in that it is an IETF-required standard on the Internet for reporting and error messages in Internet Protocol (IP) datagram routing. While not a reliability guarantee, ICMP can provide feedback regarding problems in datagram processing and

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delivery. ICMP messages are contained in the basic IP header. Examples include information on whether the destination is reachable, echo or redirect situations exist, time has been exceeded, or a problem exists with a parameter. Currently the Net is run over IPv4, and migration to IPv6 is planned. ICMP for IPv6 is based on the same definition with some changes and is known as ICMPv6. See Classes and Format of ICMPv6 Messages chart. See IP, RFC 792, RFC 1788. Internet Control Message Protocol for IPv6 ICMPv6. ICMPv6 is a required and integral part of IPv6 that must be fully implemented at every node. It is used for diagnostics and error reporting. ICMPv6 messages are preceded by an IPv6 header and zero or more extension headers, identified by a Next Header value of 58 in the header immediately preceding. ICMPv6 messages are organized into two classes, as shown in the Classes and Format of ICMPv6 Messages chart. See RFC 792. Internet Corporation for Assigned Names and Numbers ICANN. A not-for-profit organization established as a result of studies and recommendations reported in the White Paper issued by the National Telecommunications and Information Administration (NTIA) of the U.S. Department of Commerce in June 1998. This was a significant step in privatizing management of the Internet domain name system. Amid discussions with other organizations such as the World Intellectual Property Organization (WIPO), ICANN developed policy and procedural guidelines for management of the Internet domain name system worldwide. One of the significant

outcomes was the April 1999 announcement of a testbed for a Shared Registry System to be administered by five companies rather than one, with Network Solutions, Inc. to continue to maintain the registry database in order to ensure a centralized repository for unique domain names. See White Paper. http://www.icann.org/ Internet Engineering Steering Group IESG. The executive governing body of the Internet Engineering Task Force (IETF) and technical overseer for the Internet standards process, including final approval. The IESG is a member of the Internet Society (ISOC) and works within ISOC rules and procedures. See Internet Architecture Board. http://www.ietf.org/iesg.html Internet Engineering Task Force IETF. The IETF is governed by the Internet Engineering Steering Group (IESG). It is a large, international open community of network researchers and designers dedicated to the positive evolution of Internet architecture and operations. The IETF is the primary Internet protocol development and standardization body. The IETF has worked long and hard on IP Version 6 with the intention that it supersede IPv4. In 1997, the IETF made some significant changes to support more dynamic addressing schemes. Several draft standards for IPv6 were submitted in December 1998 followed by many proposed standards in 1998 and 1999. These are moving slowly through the standardization and implementation process. In the meantime, some adjustments have been made to lengthen the life of Version 4, which has address space limitations, so that

Classes and Format of ICMPv6 Messages Type of Message

Identification of Type

Message Type Number

Error message

Zero in the high-order bit of the message “Type” field

0 to 127

Informational message

128 to 255

ICMPv6 messages have the following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Message Body + | | Type

The type of message. Its value determines the format of the remaining data.

Code

Depends upon the message type. Used to create an additional level of message granularity.

Checksum

Used to detect data corruption in the ICMPv6 message and parts of the IPv6 header.

it can continue to be a viable networking solution until vendors begin to implement and support IPv6 into the new century. See Internet Architecture Board, Request for Comments. http://www.ietf.org/home.html Internet Experimental Note IEN. A document system containing information on Internet specifications and implementations. The IEN is administered by the Network Information Center (NIC). Internet Fax The terminology and goals for the development of Internet Fax systems and guidelines for the Internet Fax working group were submitted as an Informational RFC by L. Masinter in March 1999. Internet Fax is described as a document transmission mechanism between various devices and roles which may be differently configured. Several general categories of roles were defined as network scanner, network printer, fax onramp gateway, and fax offramp gateway. The common modes for Internet Fax were described as store and forward, session, and realtime. Based upon this, it was hoped that some order and consistency to developing facsimile services to be delivered over the Internet would arise. To support the concept of deploying facsimile services over the Internet, Klyne and McIntyre submitted a Standards Track RFC in March 1999 describing content feature schema for Internet Fax as a profile of a media feature registration mechanism for performing capability identification between extended Internet Fax systems. This was updated in Augst 2000. See RFC 2542, RFC 2879 which obsoletes RFC 2531. Internet Free Expression Alliance IFEA. An organization promoting a liberal computer communications environment in order to facilitate and safeguard the Internet as a free, open, and diverse forum for the exchange of discussions and data. http://www.ifea.net Internet Group Multicast Protocol IGMP. An IETF-recommended session-layer protocol for network transmissions to multiple sites. IGMP is a dynamic protocol that provides a means for end systems to request inclusion in a multicast group or video/data stream conference (group broadcast). A host can request membership into one or more groups at the same time. It can transmit datagrams to a group without necessarily having requested membership to that group. See RFC 1112, RFC 2236. Internet Information Infrastructure Architecture IIIA. A framework and support system for information about Internet resources. Uniform resource names, characteristics, and locators are functional categorizations within this architecture, intended to facilitate the location of the desired information resources. See RFC 1737. Internet International Ad Hoc Committee IAHC. The IAHC was a coalition of members of the Internet community cooperating to develop recommendations for the expansion of the Internet Domain Name System (DNS). It published a number of guidelines between 1996 and May 1997, made its Final Report in February 1997, and was dissolved in May 1997. http://www.iahc.org/

Internet Message Protocol IMP. This is one of the historic Internet protocols, submitted by J. Postel in March 1979. It describes a means for transmitting messages between message processing modules over interconnected networks. Message processing modules are processes in host computers located in different networks that comprise a framework for internetwork message delivery. IMP was developed in the context of ARPA work in interconnecting networks and was tendered by Postel as a more general internal mechanism underlying a variety of user-interface programs, thus providing a messaging system suitable for heterogenous distributed networks like the Internet that was to evolve out of the ARPANET. IMP was intended to support an environment in which processes run in hosts interconnected by gateways, with each network having many different hosts. The gateways are assumed to have minimal knowledge of which hosts are within their associated networks. IMP is implemented within a Message Processing Module (MPM). MPMs exchange messages by establishing full duplex communications and sending messages in a recognizable fixed format. The user creates a message with the chosen User Interface Program (UIP) with commands or an editor and then sends the message through a data structure shared with the MPM. The MPM discovers the unprocessed data, examines it, and determines the outgoing link in the route to an internal or external destination. The MPM communicates through a reliable procedure using a transport level protocol such as TCP. Internet Messaging Access Protocol IMAP. An electronic mail protocol descended from Interactive Mail Access Protocol and used for electronic mail servers. It provides a means to access electronic mail and news messages archived on a mail server as a dedicated or shared resource. Thus, an email client can access and read the mail messages on the remote server as though they were on a local storage medium. It is useful in situations where the reader is more concerned about reading the messages than downloading them to the local machine, especially if the messages are located at more than one site or on more than one account. IMAP is somewhat competitive with Post Office Protocol (POP), but both are useful depending upon the situation. POP is more appropriate for providing access to messages that will be regularly downloaded to a local machine and then deleted from the mail server archive. See MIME, Post Office Protocol, RFC 1730, RFC 2060. Internet Network Information Center See InterNIC. InterNet News INN. An NNTP/UUCP USENET newsreading system developed by Rich Salz for Unix systems with socket interfaces. This fast news program was first released in 1992. Later, in 1995, David Barr released a number of unofficial updates. Thereafter, maintenance of INN was taken over by the Internet Software Consortium (ISC). See C News, USENET. Internet Official Protocol Standards The title of a Request for Comments (RFC) document released

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from time to time to inform the Internet community of the state of standardization of protocols used in the Internet that are determined by the Internet Architecture Board (IAB). The memo itself is an Internet Standard and makes somewhat obsolete previous versions of the document. The document describes the standardization process, the Request for Comments documents, terms, and other important concepts and procedures related to standards used to create, maintain, update, use, and understand the Internet. Updates to the documents are released about once a year and are usually issued with round numbers (RFC 2900, RFC 2800, RFC 2700, etc.) to facilitate memorization and location. Due to the high volume of RFCs and standards that have been developed related to the Internet, the list includes only official protocol standards RFCs and does not constitute a complete index. The list is now determined by the Internet Engineering Task Force (IETF). Internet Open Trading Protocol IOTP. An interoperable framework for electronic commerce over the Internet optimized for transactions between nonacquainted parties. IOTP is independent of the payment system and can encapsulate and support secure channel card payment, GeldKarte, Mondex, and others. IOTP V. 1.0 was described in an Informational RFC submitted by D. Burdett in April 2000, and was supported by a description of digital signatures for IOTP presented by Davidson and Kawatsura. In April 2001, W. Hans et al. submitted an Internet Draft for a Payment Application Programming Interface (API) for IOTP. It proposed a common interface for communication between the IOTP application core and the payment modules, increasing interoperability among these modules and providing a “plugin” mechanism for application cores. In May 2001, D. Eastlake of Motorola submitted an Internet Draft to update RFC 2801 to document and correct errors detected since the submission of the original specification. See RFC 2801, RFC 2802, RFC 2803. Internet Phone A commercial software/hardware system from VocalTec Ltd. that allows a computer user to place a telephone voice call through the Internet very much the same way that a call is placed through traditional telephone systems. The primary difference is that the voice conversation is converted to digital data and channeled through the user’s Internet Services Provider (ISP) to the network, rather than through traditional telephone switching offices. The applications software works in conjunction with GOLD, the Global Online Directory that stores information about Internet Phone users who can be contacted online, just as the names of traditional phone subscribers can be accessed through a phone directory. See Global Online Directory. Internet Policy Registration Authority IPRA. A top-level digital security certification authority (CA) in the Internet certification hierarchy. IPRA is X.509compliant. Internet Printing Protocol IPP. An application level protocol to facilitate remote printing over distributed

networks based upon Internet technologies. The IPP model and semantics were described in an Experimental RFC by deBry and others in April 1999. It is a simplified model, including abstract objects, attributes, and operations that are independent of transport and encoding methods. Essentially the model is based upon a printer and a job object, with a job optionally representing multiple documents. Users can query printer capabilities, submit jobs, get status information on jobs, and cancel jobs. Security and internationalization aspects are also described in the specification. The documents related to IPP include • Design Goals for an Internet Printing Protocol • Rationale for the Structure and Model and Protocol for the Internet Printing Protocol • Internet Printing Protocol/1.0: Model and Semantics • Internet Printing Protocol/1.0: Encoding and Transport • Mapping between LPD and IPP Protocols • Internet Printing Protocol/1.0: Implementor’s [sic] Guide The IPP implementor’s guide was submitted as an Informational RFC by Hastings and Manros in July 1999 to aid implementors in understanding and applying the information in the suite of documents related to IPP semantics, encoding, etc. The guide aids implementors in designing client and/or IPP object implementations and provides an order in which requests can be processed, in addition to error checking. See RFC 2567, RFC 2568, RFC 2566, RFC 2565, RFC 2569, RFC2639. Internet Protocol IP. A very significant protocol in that it is an IETF-required standard on the Internet along with the Internet Control Message Protocol (ICMP). There are other related IETF protocols, which are recommended or elective. IP is very widely used in TCP/IP implementations. Internet Protocol provides addressing, segmentation and reassembly, and transport functions in conjunction with a number of associated protocols. Logical IP addresses are used to identify hosts by means of network and node addresses. A number of categories of networks are supported as IP Classes. RFC 768 describes Internet Protocol. RFC 1602 is recommended for its description of the Internet standards process, and RFC 2200 is a useful standards track document for Internet Official Protocol Standards that further describes the standardization process. See IPv6 for more informaton and charts. See IP Class, IPv6, RFC 950, RFC 919, RFC 922, RFC 2200. Internet Protocol Consortium IPC. The IPC administers the InterOperability Lab at the University of New Hampshire for testing protocols of importance to intercommunication on the Internet. There are three testing services and 17 consortiums currently supporting this effort. Of current interest is a test lab for testing IPv6 implementations, the version of Internet Protocol being phased in to coexist with and probably eventually supersede IPv4.

Internet Protocol (IP) Mobility Support A set of media-independent protocol enhancements submitted as a Standards Track RFC by C. Perkins, in October 1996, and updated/extended as a PPP IPCP option by Solomon and Glass in February 1998. IP Mobility Support enables transparent routing of IP datagrams to mobile nodes on the Internet. A mobile node is identified by a home address, regardless of where it happens to be connected to the Internet at any particular time. While away from the original home address, the mobile node is considered to be associated with a “care of” address in much the same way as individuals who are traveling may use a care of address for postal mail delivery. The mobile node makes its care of address known by registering it with a home agent which, in turn, sends datagrams destined for the mobile node through a tunneling process. At the end of the tunnel, the datagrams are delivered to the mobile node. See RFC 2002, RFC 2290. Internet Protocol Suite IPS. A standardized set of protocols based on a layered model that enables Internet systems to intercommunicate. Minimally, a host must implement at least one protocol from each layer, including the application, transport, Internet, and link layers. These layers form the basic architecture for managing the hardware and software functions that enable communication over the Internet using Internet Protocol (IP). In general, layered models are organized to illustrate more abstract applications-related concepts at the top and more basic hardware-related functionality and transport media at the bottom. NASA has been conducting research to improve the efficiency of the IPS for satellite-based networks through its Satellite Networks and Architectures Branch. Since radio communications with satellites involve relatively long delays, special problems are involved in implementing IP. See IPv6. See RFC 1122, RFC 1349, RFC 1958, RFC 2502, RFC 2600. Internet Relay Chat IRC. A worldwide “realtime” 24-hour text-based communications chat link on the Internet developed in the late 1980s by Jarkko Oikarinen. IRC was inspired in concept by MUT and in format by BITNET Relay Chat. Development began in August 1988, with the first server established in Finland as tolsun.oulu.fi. IRC II was released in 1989 by Michael Sandrof. A number of other developers released versions or variations. By 1989, IRC had more than 50,000 users. In 1993, Request for Comments (RFC) 1459 was published to provide a consistent reference and basis for the IRC and clients intended to conform to IRC guidelines. It was followed in 1994 by the Client-to-Client Protocol (CTCP) to support IRC client communications. Many IRC servers and computer systems are configured to provide a means to communicate remotely with IRC. Generally it is best to connect to one geographically close to the ISP, but some servers are busier than others and it is sometimes a good idea to select a low-use server that is farther away. IRC is typically accessed through port 6667.

IRC is an important meeting ground for people around the world. The form of an IRC chat is somewhat like a group conversation on a teletype machine, except that the output to the screen is much faster than the transmission and output to a printing teletype. Many celebrities, in and out of the telecommunications industry, have been known to participate in IRC conversations and to draw large crowds of participants around the world. To join a chat (a communications channel dedicated to a specified topic), you must have access to a provider that provides a port to IRC, a basic understanding of how to sign onto a chat, and a willingness to learn a few simple commands. A command set must be learned to access IRC with a text-based client (there may not be a point-andclick graphical client available for every operating system). From the text line, a conversation on IRC is joined by typing #join gardening (or a topic of interest other than gardening). It’s a good idea to visit the help channel by typing #join irchelp to get a feel for the way things work. There are thousands of IRC channels, so most common topics already exist; if you are seeking an uncommon topic, it will be automatically created when the command #join myweirdtopic is typed. The channel automatically disappears shortly after the last person leaves, except in the case of registered channels, but comes back (is recreated) as soon as it is re-entered. Most IRC channels are public forums, but private keyword-protected IRC channels can be created at any time. Courtesy is very important on IRC. If a participant is rude, crude, inflammatory, or off-topic, he or she will be summarily kicked off the channel by an operator. If there is no operator present, usually everyone else will leave. Observe courtesy and Netiquette on IRC, and don’t talk unless it’s something worth saying. The operators or “ops” are hardworking volunteers who strive to make the IRC an open and fair forum for all. IRC is a great resource. Companies can have meetings, users’ group members can get together for international chats, friends can hang out, nonprofit organizations can keep in touch with members, professionals can seek technical advice, and much more. The Sample IRC Session chart shows an example of entering and exiting a text-based IRC server. The IRC software is freely distributable through a GNU General Public License from the Free Software Foundation. Many Internet Services Providers provide IRC access. Communications are predominantly in English, but other languages are sometimes used. See Internet Relay Chat operator, RFC 1459, RFC 2810, RFC 2811, RFC 2812, RFC 2813. Internet Relay Chat operator An individual designated with certain responsibilities and powers for a channel on Internet Relay Chat (IRC), a public communications forum on the Internet. In an active chat channel, some of the participants are designated with “@” symbols next to their online nicknames. These operators or “ops” have jurisdiction over their channels and may set the guidelines for interaction and remove those who do not follow the guidelines.

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Because they establish and maintain law and order on IRC, many people call them IRC cops. In general IRC ops are hard-working volunteers who make reasonable decisions and have kept IRC a viable communications medium in spite of the many people reluctant to follow guidelines of good taste and common sense. See Internet Relay Chat. Internet Relay Chat (Server) Protocol IRC Server Protocol. A protocol for describing how Internet Relay Chat (IRC) servers may connect together to form a network. The IRC protocol was first implemented in the late 1980s and grew to support a worldwide network of servers and clients in just a few years. IRC Protocol is text-based and enables a simple socket program to connect as a client. Over the years, various developers have created operating systemsspecific text and graphical clients to interact in IRC chat sessions using IRC Protocol. In general, IRC Protocol has been implemented over TCP/IP, though there is no restriction as to this.

Each IRC server has a unique name up to 63 characters and maintains a global state database that gives a picture of the IRC network so that each server is known by other servers. A hostmask can be used to group servers according to name in order to exclude hosts outside of the list. Servers hold netwide unique identifying nicknames (up to 9 characters), usernames, and connecting host informaton for each client currently connected to the IRC system. Internet Relay Chat Protocol was submitted as an Experimental RFC in May 1993 by Oikarinen and Reed and has been updated by numerous RFCs since that time. See Internet Relay Chat, RFC 1459, RFC 2810, RFC 2811, RFC 2812, RFC 2813. Internet Research Steering Group IRSG. The IRSG manages the Internet Research Task Force (IRTF) in conjunction with the IRTF Chair. Membership in IRSG is primarily those in chairing positions in the various research groups. The IRTF Chair is appointed by the Internet Architecture Board.

Internet Relay Chat Commands Summary A simple set of commands allows a user to navigate IRC, just as a simple set of commands allows a user to do various file lookup and maintenance functions on a local computer. The IRC commands provide user and status information, as well as chat channel-related functions, as shown in this chart. The chart on the following page includes further descriptions of some of the functions of commonly used commands. In interactive mode, commands must be preceded by a slash (/) to be recognized, otherwise they are interpreted as text and broadcast to all the other participants of the same chat channel. Commands can be referenced at any time by typing “/help” with an option for the actual command name. /help *choices: ! assign bye comment deop dquery exec help info kick list mload news notify ping redirect say signoff time userhost which window

: away cd connect describe echo exit history input kill load mode newuser on query rehash send sleeps timer users while xecho

abort basics channel ctcp die encrypt expressions hook intro lastlog lusers motd nick oper quit restart sendline quit topic version who xtype

admin beep clear date digraph etiquette flush if invite leave me msg note parsekey quote rules server stats trace wait whois

alias bind commands dcc dmsg eval foreach ignore join links menus names notice part rbind save set summon type wallops whowas

Internet Relay Chat Command Examples General User Commands /basics

Very basic introductory information about IRC; a good thing to read the first time you use the system. Also try out /help newuser.

/bye

Drops the user out of IRC; /quit, /exit, and /signoff do the same.

/clear

Clears the current window; reduces clutter.

/date

Displays the current date and time for the local server or a specified server. The /time command performs the same function as the /date command.

/join

Changes the location to the specified IRC channel. For example, /join #buglovers puts the user in the channel with other insectophiles.

/help

Self-explanatory and the command to type if you’re really stuck.

/info

Provides information about the origins of IRC, its creators, maintainers, slaves, and other perpetrators.

/list

Provides a very long list of thousands of channels, and information about the topics and number of participants, so use this command with caution. The * (wildcard) character may be used to specify the characteristics of the listing, as can a number of useful arguments: -public shows only public channels; -private shows only private channels; -topic shows only channels with a specified topic.

/msg

Sends a single private message to the specified person. Use /query if longer private conversations are desired.

/menus

A simple scripting feature for creating custom user menus for an IRC session. This is great for creating mnemonic commands or shortcuts.

/newuser

Information about IRC commands and IRC etiquette.

/nick

Sets the user’s nickname. If the nickname is taken, another must be selected, or the default used.

/news

Information about changes, updates, new commands, and other IRCrelated functions. It’s a good idea to check this once in a while.

/query

Initiates a private conversation with a specified user. Anything you type now is seen only by that user. The query command with no arguments cancels query mode.

/set

Sets various status, logging, and message parameters.

/who

Lists users on IRC; with a * (wildcard), it shows the local channel. A number of arguments can restrict the listing, e.g., -operators lists only operators.

/whois

Provides more detailed information about the user specified, and his/her “actual identity.”

Priority Operator Commands /kick

Removes a person from the current IRC channel. Used only when the user contravenes IRC etiquette.

/kill

Removes a person from IRC. Rarely used, and only with great discretion after the person has blatantly or seriously imposed on others, committed fraud, or disrupted services.

/stats

Provides IRC server usage statistical information, such as the number of lines, amount of information carried, authorized users, server uptime, etc.

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Internet Research Task Force IRTF. An organization engaged in discussion and Internetworking research to further the evolution of the Internet, especially with respect to technologies, architecture, protocols, and applications. The IRTF works in consultation with the Internet Research Steering Group (IRSG) and with the Internet Engineering Task Force (IETF) and the Internet Architecture Board (IAB). See RFC 2014. http://www.irtf.org/ Internet Resource Access IRA. On OEM product distributed by CREN in cooperation with IBM, announced in August 1994. This system was intended to facilitate Internet access for global academic and research communications by institutions that had largely been connected by BITNET networks up until this time. IBM provided hardware and software as a foundation for the CREN system. IRA provided

connectivity between RSCS on IBM systems and Internet TCP/IP on open systems. See BITNET, Corporation for Research and Educational Networking. Internet Safety Policy ISP. A policy required to be in place in federally funded institutions that provide Internet access to vulnerable individuals, especially children. See Children’s Internet Protection Act. Internet Secretariat An organization providing administrative assistance to a variety of Internet governing bodies. Internet Security Association and Key Management Protocol ISAKMP. An application-level network protocol submitted as a Standards Track RFC by Maughan et al., in November 1998. ISAKMP utilizes security concepts for establishing Security Associations (SAs) and cryptographic keys within the Internet environment. It defines procedures and

Sample Internet Relay Chat (IRC) Session Login, Join Chat Channel, and Logout web1: /s1/abiogen 2% irc -d * Connecting to port 6667 of server irc.ais.net * Looking up your hostname... * Checking Ident * Found your hostname * Got Ident response * ... * Welcome to the Internet Relay Network abiogen * If you have not already done so, please read the new user information with /HELP NEWUSER * Your host is irc.ais.net, running version 2.8/hybrid-5.2p1 * This server was created Tue Jun 2 1998 at 21: 50:37 CDT * umodes available oiwszcrkfydn, channel modes available biklmnopstv * ... * There are 4488 users and 31563 invisible on 60 servers * There are 192 operators online * 15805 channels have been formed * This server has 3924 clients and 8 servers connected * Current local users: 3924 Max: 5207 * Current global users: 36051 Max: 42661 * ... /join #babylon5 * IRCuser has left channel #earth * IRCuser ([email protected]) has joined channel #babylon5 * Topic for #babylon5: Time is fluid ... like a river with currents, eddies, backwash. * #babylon5 MrBawb 899336524 * Users on #babylon5: LadyHawk- @Ivanova @Colen @BobaFet Bro_Theo @MrBawb CaraD @Dr_Mick @‘Dr_Evil‘ Llorio @JoeyLemur @Delenn @Nu-ghauD @Spencer @OrenWolf @Wingnut @_Kosh_ @KorMath ETHryAway GleeB @EightBall @necKro NuFrosty @necKro_II @Pinball @Ramikin @Zathras @Draal @Kosh @TheOne @LeeThomps @BabCom @Brett IronWing @necK_idle @Sheridan @BB18 @ThemBones @T3GAH_ @Daniel‘za Darb @CHeL @BluKnight @Merlyn @ZargDunce * #babylon5 899133476 Welcome to #babylon5, IRCuser. -BabCom- Hi IRCuser! I’m BabCom, the #babylon5 bot. -BabCom- I do not recognize you. If you plan to become a regular on #babylon5, -BabCom- ‘/msg BabCom hello’ and I’ll add you to the userlist! .... -BabCom- /exit

packet formats for peer authentication, SA creation and management, key generation, and threat mitigation for establishing and maintaining secure communications. ISAKMP is distinct from key exchange protocols, as there may be various key exchange protocols with different security properties. A common framework facilitates intercommunication through SA attribute formats for negotiations, modifications, and deletions at all layers of the network stack. ISAKMP has been assigned UDP port 500. Cisco Systems provides a no-charge ISKMP software distribution based upon the IETF ISAKMP to support Internet Key Management through this protocol. See RFC 2408. Internet Services Provider ISP. A commercial vendor providing access to the Internet and some or all of its services. These services may include email, newsgroup access, World Wide Web access, Internet Relay Chat (IRC), telnet to other sites, Unix shell accounts, and more. Some providers have flat-rate fees for unlimited access, while others provide unlimited access during off-peak hours, and limited or pay access during times of heavy use. Others charge by connect time. Many distinguish between commercial and personal users, with separate fee scales for each, usually with more mailboxes and longer connect times for business users. The ISP’s link to the Internet may be through a variety of connections, usually 56 kbps or higher, up to T1 or even T3 lines. However, when dialing up through a regular modem on a phone line, you will not be able to receive and transmit information faster than the slowest point in the link (e.g., the modem speed). There are several large, well-known providers, as well as thousands of small, local service providers. The level of service of many small providers equals or exceeds those of the large companies, so shop around. See Internet Access Provider, National Service Provider. Internet Society ISOC. A significant nonprofit international professional organization dedicated to furthering global cooperation and coordination of the evolution of the Internet and its associated technologies. ISOC was founded in January 1992. It grew out of standards development activities of the IETF and Internet Activities Board (IAB) in the early 1990s and counts among its members many of the early Internet pioneers. Fund-raising to continue to support the standards process was one of the important initial mandates of the Society. The ISOC oversees and/or works with a number of other agencies, including the Internet Architecture Board (IAB) and the Internet Engineering Steering Group (IESG). It supports and promotes Internet-related public policy, education, standards, and participation in the Society. See RFC 1310, RFC 1602. http://www.isoc.org/ Internet Software Consortium ISC. A group dedicated to developing production-level high-quality reference implementations of Internet technologies suitable for use by large-scale network providers and operators. Subgoals include compliance to key standards, straightforward implementation, and high

interoperability. The ISC was formed with financial assistance from UUNET Communications Services and later from the Internet Multicasting Service and various sponsors. http://www.isc.org Internet Standards process The orderly evolution of the Internet is of concern to many networking professionals, so the Internet community at large has developed various procedures to facilitate this process. For a technology to become an official or required Internet standard, it must go through a formal discussion, evaluation, and testing process. A protocol must pass through several defined levels of maturity, including Proposed Standard, Draft Standard, and (Internet) Standard and is documented in Requests for Comments (RFCs) notifications to the Internet Community. The Internet Engineering Task Force (IETF) must recommend advancement at each stage for the protocol to pass to the next level, and specified waiting periods are imposed. Intellectual property rights (e.g., patents) must be identified and noted in Standards Track documents. When a protocol has successfully gone through the successive levels of the Standards process, it is assigned an STD number. The process is somewhat recursive in that it is described within itself in RFC 1602. If a standard becomes outdated, the IESG may elect to retire it and appropriate notifications will be posted. For a standard to be revised, it must go through the full standards process again. The old standard will usually be superseded and retired to Historic status. However, if the new standard is sufficiently different or more mature than the previous standard such that both implementations have current implementation value, the two may coexist. Non-standards-track specifications are labeled as Experimental, Informational, or Historic. The Best Current Practice (BCP) subseries is a structure similar to the Internet Standards process within which proposals from community leaders can be fielded within the Internet community to stimulate and enable the development of guidelines for consensual policies and operations. See Internet Engineering Task Force, RFC 1311, RFC 1602, RFC 2026. Internet Transparency In essence, Internet Transparency is a philosophy and design goal that supports the capability of the Internet to send anything anywhere. It holds that packets should be able to carry any type of data to any desired destination without the user worrying about format, routing, interoperability or other underlying aspects of an interconnected homogenous network. In actual implementation, there have been fits and starts and the occasional backslide in holding to this philosophy, but there appears to be a general desire to continue to work toward this goal and to extend the capabilities and overcome the technical limitations that stand in the way of a fully transparent Internet system. In February 2000, B. Carpenter submitted an Informational RFC discussing this issue that was used as input to an Internet Architecture Board (IAB) workshop held in July 1999. The RFC documents

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some of the sources of loss of transparency and, in particular, issues such as firewalls, IP address allocation, intranet models, etc. See RFC 2775. Internetwork Packet Exchange Protocol IPX. A network layer protocol that provides addressing, routing, and packet-switching functions for Open Systems Interconnection (OSI) model systems. IPX works on a best-efforts basis to deliver packets without a guarantee of successful delivery or verification of such (these are handled by other protocols). Internetworking Alliance See World Internet Alliance. Internetworking Over NBMA ION. A working group jointly chartered with the Internet and Routing Area of IETF, ION is a merger of the IPATM and ROLC groups. It focuses on issues of internetworking network layer protocols over NBMA subnetwork technologies, including encapsulation, multicasting, address resolution, optimization, and others. See ATM, Frame Relay, SMDS, X.25, ISSLL, ITU, RFC 1932. InterNIC Internet Network Information Center. This is a service mark of the U.S. Department of Commerce; the name was associated for a number of years with an authorized central registry for domain names and IP number addresses on the Internet, hosted by Network Solutions, Inc. Network Solutions/VeriSign was established as an exclusive provider of domain name registry services for Top Level Domains (TLDs) in 1991. InterNIC was established in 1993 in cooperation with the National Science Foundation (NSF) to continue domain name registration. To be part of the Internet, you need a unique identifier for the network and the individual host from which information is being sent. The domain name is associated with an IP number to create a unique address on the Internet. (More than one domain name can be assigned to an IP number, depending upon the administrative policies and services offered by individual ISPs.) In order to manage this administrative task, InterNIC kept track of registrations and domain name-IP number correspondences in a central database archive. There has been a yearly fee since the mid-1990s for

the registration and maintenance of domain names and the monopolistic nature of InterNIC has come under continued dispute, with various stalled proposals for providing additional domain name extensions and competitive opportunities for other name registries. In 1998, VeriSign GRS was separated from Network Solutions, Inc. at the time Network Solutions Registry was handling domain name registrar services. By the late 1990s, many proposals for additional domain name extensions had been tendered and other registrars were being approved for granting domain names. A central database still needed to be maintained to ensure uniqueness and an orderly process for registrations, which were now in the tens and hundreds of thousands per month (and rapidly increasing). The demand for names was largely due to the increase of users on the Internet and the commercialization of the Net, which resulted in a domain name becoming an important branding and location tool for vendors and other organizations. With competition for the provision of domain name registration services, the price dropped from $200 in the mid1990s to $50 in the late-1990s to $15 (and sometimes less if the domain was bundled with other services) in 2000. By 1999, some commercial firms were reported to be applying for as many as 1000 domain names per month (usually for individual products in their product lines) and speculators had registered tens of thousands of common words and good potential names in the hopes of reselling them later at a profit. A clamor arose over demand for domain names, with new registrants claiming that all the good names were taken. The technical difficulties in simply extending the total number of IP numbers to meet demand are discussed elsewhere in this reference. The Network Solutions Registry was created and registry services agreements extended until 2003. The commonly known established name extensions include .com, .edu, .gov, .net, .info, .int, .usa, and .org (along with assigned extensions for individual countries). Other extensions were subsequently added in 2001, including .biz to satisfy commercial demand

Internet Standards Process – Levels of Maturity Standard Abbr.

Description

Proposed

PS

Entry-level for standards-track specifications as accepted by the IESG. To become a PS, a specification must be technically complete, generally well understood, received by the Internet community, and have design and reliability issues resolved.

Draft

DS

A PS may be promoted to DS after at least two independent and interoperable implementations from different code bases have been developed and sufficient successful operational experience has been obtained. DS status indicates confidence that the specification is mature and will be useful.

Approved

IS

A DS may be promoted to IS and assigned an STD series number if significant implementation and operational maturity are achieved and the IS promises to be of significant benefit to the Internet community.

and .info for information-based services, with plans to implement .pro, .aero, .museum, and possibly others in the future. VeriSign TRS now provides services for the .com, .net, and .org domains and the InterNIC name is specifically associated with the Department of Commerce Web site. See domain, domain name, domain name server, IP address, and the Appendix for a list of country code domain extensions. http://interNIC.net/ interprocess communication environment IPCE. The concept of interprocess communication (IPC) became important when people began interconnecting computers and developing protocols to allow them to share data communications. With the spread of timeshare networks in the late 1960s and 1970s, the various hardware and software mechanisms to facilitate IPC began to develop. They expanded when remote “smart” terminals and peerto-peer networks were invented. Computer bulletin board systems (BBSs) and local area networks (LANs) in the 1980s and the Internet in the 1990s are important extensions of the general concepts of IPC. They have increasingly enabled users to utilize resources on remote systems and even to share files and programming environments as though they were local resources, thus extending IPC from something transient and part-time in its earlier implementations into a system in which many of the computers and processes are in 24-hour communication with one another. This doesn’t just speed up the sharing of information and resources; it also creates a higher order of environment, somewhat like a cooperative or symbiotic digital organism. Given the advantages of access to greater resources through a larger, more sophisticated interprocess communications system, it is likely that this trend will continue. With highspeed optical connections, the distinction between processing speeds and bus speeds (that provide intercommunication among systems) becomes less critical and individual machines in advanced IPCEs may begin to lose their distinction as individual systems and be seen more as specialized aspects of a larger computing environment. interrogate 1. In lower level software, to query the availability or state of a device or process. 2. In higher level software applications, to query a data or information resource in a systematic manner. For example, an intelligent agent may query a number of search engines on behalf of a user to find suitable avenues for further inquiry, thus automating and streamlining the process for the user. 3. In human terms, to systematically query the availability of specific data or information or to systematically query answers to general or particular questions, as in a database or other information archive. interrupt A hardware system computing resource that causes a suspension of a process, usually to perform another temporary function. On some desktop systems, interrupts were implemented as a means of handling device requests to the CPU and were thus assigned IRQ numbers. This method has a number

of significant limitations in that interrupts are often limited and must be carefully assigned to conserve resources and prevent conflicts, and no two devices can use the same interrupt simultaneously. On an IRQ-driven system with several peripherals, it was sometimes necessary to disable one device (e.g., an internal modem) in order to operate another device (e.g., a sound card). This means of managing system resources was not common to all computers, but a significant number of Intel-based consumer machines sold in the 1980s and early 1990s had this form of interrupt-handling. To overcome the problem of interrupt-handling, a number of vendors developed a system called Plug and Play, which allowed dynamic allocation of interrupts and power-on swapping of devices or device controller cards, provided that they support the Plug and Play format. (Don’t just assume a component is Plug and Play; verify it.) While this doesn’t fully change the underlying concept, it is at least a solution that aids consumers in getting the best use of their machines. See IRQ and accompanying Interrupt Request Numbers chart. See Plug and Play. INTERSPUTNIK The Russian word for satellite is sputnik. The INTERSPUTNIK International Organization of Space Communications system of satellites delivers a variety of programming and data services, including the Voice of America (VOA), which has formed business relationships with a number of independent Russian radio stations, and Direct Net Telecommunications, which provides international digital voice and data services. See INTELSAT. Interstate Commerce Act of 1887 An act established to regulate the growing interstate railroad business, with the intent of ensuring fair and equitable dealings between transportation carriers and the public. Later, the jurisdiction of the Interstate Commerce Commission was broadened to include regulation of communications services, including telephone, telegraph, and cable. Telecommunications services were later split off into separate communications acts as they grew in prevalence and importance and the Interstate Commerce Commission is now mainly tasked with regulating railroad lines, express companies, and similar transportation carriers. intersymbol interference ISI. ISI is a form of temporal distortion found in many aspects of telecommunications transmissions where two or more symbols are being transmitted in the same channel and overlapping of waveforms can occur or in systems where distortion is associated with the transmission of sequentially adjacent symbols. It is particularly prevalent where a lot of information is packed into a tight physical space or a tight time frame. Thus, it tends to occur in wire and optical networks where high speeds, distance, and attenuation are factors, in high-density recording data, and in high-speed wireless communications (e.g., digitized voice communications). Rolloff and distortion at transmission band edges can increase ISI. In optical fiber transmissions, spreading of the optical beams over distance can result in increased dispersion and ISI.

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Various statistical models for detecting this type of interference have been proposed and research on mitigating this type of interference was beginning to be more comprehensively documented in the mid1990s. Precoding (often in conjunction with Trellis coding) can sometimes help reduce ISI. Sometimes ISI is deliberately introduced into a transmission to shape the signal and may be systematically removed at the receiving end to mitigate other types of transmission problems. intra- A prefix for inside, within. An intranetwork is a network within a company, home, or other confined locality. In many business contexts, it implies an Internet-compatible internal network, with many of the same functions, such as a Web server, IRC server, email server, etc. intracellular electrode A device created in 1949 by Ling and Gerard. It consisted of a tiny glass capillary tube with conducting salt, no more than a few tenths of a micron in size. When used in a microprobe, it was possible to measure electrical currents in individual biological neurons. See neural networks. intranet An internal network, as in a company or institutional local area network (LAN). The term was coined in part to distringuish internal networks from inter-business networks (extranets). Actually, the first meaning ascribed to intranets was inter-business networks, but even the person who coined the term gradually abandoned it in favor of the de facto LAN connotation. See extranet. intrapreneur A person within an organization, usually a large one, who manages, takes risks, proposes and promotes ideas, leads, and generally behaves as an entrepreneur within and on behalf of the organization. See entrepreneur. intruder An entity attempting to gain access or gaining access to a restricted system or system resource without proper authorization. See hacker. intrusion detection The process of determining whether an intruder is attempting to gain access or has gained access to a system or resource without proper authorization. This can apply to physical environments, where various motion detectors and other technologies may detect the presence of an object or person that should not be present, as well as virtual environments, where an unauthorized process or anomalous process or unusual pattern of activities may indicate unauthorized activities. System monitors, intrusion detection algorithms, usage patterns, incorrect password limits, and electronic alarms are all mechanisms used in network intrusion detection. inverse multiplexer A multiplexer is a device which takes a circuit, broadcast signal, or given amount of data bandwidth and breaks it up into smaller segments. An inverse multiplexer does the opposite: it takes a number of smaller segments and puts them together to create a larger entity. An inverse multiplexer is often used in conjunction with computers for high bandwidth applications to coordinate the signals, as in videoconferencing systems that require more than one data line to operate.

As an example, imagine an ISDN data network set up for videoconferencing. Videoconferencing requires fast transmission of high-bandwidth resources: video and sound. Some videoconferencing systems are designed to run over two or three separate ISDN lines. In this case, the inverse multiplexer takes the data from the three sources, coordinates the timing, and sends this information to the computer system, which then displays the images and plays the sound together. inverter 1. A device or circuit which reverses the polarity of a signal (from positive to negative, or vice versa). 2. A device which changes AC to DC or vice versa. AC to DC inverters (often called converters) are very commonly used in digital electronics that draw AC power from a socket. 3. A device or operation that inverts a signal. If the incoming signal is high, the inverted, outgoing signal is low, and vice versa. It is sometimes called a NOT circuit. Inward Operator Personnel who can assist other operators (e.g., TSPS operators) in making call connections. Normally an Inward Operator does not communicate directly with callers, though phone phreakers have been known to do so. InWATS Inward Wide Area Telephone Services. A subscriber service to receive incoming calls and be billed for them, rather than having the caller billed, somewhat like an automated collect call. This service is provided by a variety of local and interexchange carriers. See OutWATS, WATS. IOC See ISDN Ordering Code. IOF Inter-Office Facility. IOL InterOperability Lab. Research, development, and vendor verification of interoperability of wireless communications products at the University of New Hampshire. ION See Internetworking Over NBMA. ionization 1. The process of dissociating atoms or molecules into ions and/or electrons. 2. The process of rendering a gas to be conducting by causing some of the electrons to detach from its molecules. 3. The process of rendering a solution to be conducting by electrochemical means, assuming the solution is one that contains a compound that can be made conducting. ionization current A current which results when an applied electric field influences the movement of electrical charges within an ionized medium. ionoscope A camera tube that incorporates an electron beam and a photoemitting screen where each cell in the screen’s mosaic produces a charge. This charge, or electric current, is proportional to the variations of the light intensity in the image captured. The ionoscope produced the television image which was then transmitted to the kinescope for viewing in the days of live broadcasts. Sometimes known by the general use and older trademarked term iconoscope. See kinescope. ionosphere 1. A series of layers of ionized gases enveloping the Earth, the most dense regions of which extend from about 60 to 500 km (this varies with temperature and time of day). 2. The portion of the Earth’s outer atmosphere which possesses

sufficient ions and electrons to affect the propagation of radio waves. In this region, the sun’s ultraviolet rays ionize gases to produce free electrons; without these ionized particles, transmitted radio waves would continue out into space without bouncing back. The deflected path of a radio transmission is effected by the direction of the waves and the density of the ion layers it encounters. See ionosphere sublayers, radio waves. ionosphere, celestial A region around a celestial body comparable in ionic properties with the Earth’s ionosphere. ionospheric sublayers/subregions The Earth’s ionosphere has generally been classified into a number of named regions, each of which has properties that make it somewhat distinct from others. These regions are largely hypothetical models, as they may change with the time of day or other factors and don’t really form distinct layers as might be implied by the following chart. Nevertheless, the distinctions are useful as a basis for study and for determining good times for propagating radio frequencies through the ionosphere, even though further refinement and changes are likely in understanding of the regions. See Ionospheric Subregions chart. ionospheric wave Sky wave. A radio wave moving into earth’s upper atmosphere. When sky waves are reflected back, at about 2 to 30 MHz frequency ranges, they are known as short waves. See ionosphere, ground wave, radio, short wave, skip distance. IP See Internet Protocol. IP address, Internet Protocol address On a packet network like the Internet, a number in each packet is used to identify individual senders and receivers. Under Internet Protocol version 4 (IPv4), this is a 32-bit number, theoretically able to accommodate several billion possible addresses, although the actual total is lower due to allocation of subtypes within the system.

To be associated with the Internet, a unique network address number must be assigned. Once a network address has been assigned to a server, additional computers physically attached to that server (as a subnet) can be individually assigned numbers by the local system administrator (certain number patterns are suggested by convention for subnets). The IPv4 address is a two-part address identifying the network and the individual devices on that network. It is written as four decimal numbers separated by periods with each number representing a byte of the 4-byte Internet Protocol (IP) address. The decimal numbers are in the range of 0 to 255 (all zeroes or all ones are reserved for administrative use). Periods are used to decimal references to different parts of the network as follows: 255.255.255.255 The left part of the address represents the network. Depending upon the value in the first byte, the network address may be 1, 2, or 3 bytes long (see IP Class for further detail). A mask enables the rest of the address to be interpreted to remove a subnetwork number, if applicable, to determine the host number. There are static IPs and dynamic IPs: those more or less permanently assigned and those assigned on an as-needed basis, respectively. Many Internet Service Providers assign temporary dynamic IP numbers to their subscribers to extend limited IP resources to the greatest number of people. As the Internet has grown, it has become increasingly important to manage and reuse IP number resources. The IP address is located through an email or domain name lookup. IP addresses can correspond to more than one DNS, although a DNS does not have to have an IP address. The IP system is divided into classes, assigned roughly according to the size of the network. See IP Class, Domain Name System, Internet Protocol, InterNIC. IP Broadcast over ATM An IP multicast service in

Ionospheric Subregions Name

Approx. location

D region

Notes A daytime phenomenon and hence not characterized in the same way as some of the regions which exist also at night. Daytime ionospheric activity in this region can impair radio wave propagation.

E region

100 to 120 km

The region which is most distinct in its characteristics and most apt to be classified as a layer.

F1 and F2 regions

150 to 300 km

F2 is always present and commonly used for radio wave propagation, and has a higher electron density than F1, which is only active in the daytime. The F2 region varies in height, and may sometimes go as high as 400 km in the hottest part of the day.

G region

outer fringes of F

Suggested as a distinct layer by some, but its existence as a definable separate layer is debated.

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development by the IP over ATM Working Group for supporting Internet Protocol (IP) broadcast transmissions as a special case of multicast over asynchronous transfer mode networks. See RFC 2022, RFC 2226. See the Appendix for details and diagrams on ATM. IP Class A network categorization system that facilitates the identification of networks connected to the Internet as each network requires a unique address ID in order to be recognized on the Net by other systems. The system was originally organized into three general classes, with some special cases. Classes A, B, and C were designated for unicast addresses; later, Class D was designated for multiclass addresses, and Class E was set aside for future use. Certain bits and Internet Protocol (IP) address ranges were assigned to these classes and there were many discussions as to how to assign and administer public and private network classes and addresses. An IPv4 address is a 32-bit number within which the IP Class address is identified. The unprecedented demand for IP numbers for linking computers to the Internet resulted in the original scheme being quickly oversubscribed. Thus, the original class scheme has been modified since its inception and IPv6 has been designed to accommodate a larger number of Internet addresses. The specific comments that follow pertain to IPv4, with additional newly developed classes described in general terms. In general, an IP Class address (IPv4) is organized

as four 8-bit decimal numbers (octets) separated by periods: Class.Class Bit.Network ID.Host ID e.g., 2 5 5 . 2 5 5 . 2 5 5 . 2 5 5 (general format) e.g., 192 . 168. 0. 42 (local network ID) The amount of data designated for the Network ID and the Host ID varies, depending upon the value in the leftmost byte and may be 1, 2, or 3 bytes. Zeroes are used to designate unknown addresses with all zeroes (0.0.0.0) representing the default route. Loopbacks are designated with 127 (e.g., 127.0.0.1) and broadcast packets are designated with 255 (in other words, each system on the local network will receive the message if 255 is used). The class definitions have been expanded and adjusted according to changing needs on the Internet, although the first three classes retain the general format from larger to smaller networks. See Internet Protocol Classes chart. See address resolution, IP address. IP echo host service A network service protocol for sending packet IP datagrams after exchanging IP source and destination addresses. See RFC 2075. IP forwarding The process of receiving an Internet Protocol (IP) data packet, determining how it will be handled, and forwarding it internally or externally. For external forwarding, the interface for sending the packet is also determined and, if necessary, the media

Internet Protocol (IP) Classes Class

Range

H/O bits

Notes

Class A

0 to 127

0

A network service category similar to a private line for constant bit-rate (CBR) services such as voice communications. Class A networks have a 1-byte network number and a 3-byte host number with 7 bits allocated to the network ID and 24 bits reserved for the host ID. Thus, Class A can support up to 128 networks, each with 16 million hosts.

Class B

128 to 191

10

Class B networks have a 2-byte network number and a 2-byte host number with 14 bits allocated to the network ID and 16 bits reserved for the host ID. Thus, Class B can support up to 16,383 networks, each with 65,535 hosts.

Class C

192 to 233

110

A network service category for connection-oriented data (COD) that is suitable for bursty applications but capable of functioning at higher data rates than some other services. Through multiplexing, Class C services can be used for administering shared services. Class C networks have a 1-byte network number and a 3-byte host number with 21 bits allocated to the network ID and 8 bits for the host ID. Thus, Class C can support up to 2,097,151 networks, each with 256 hosts.

Class D

224 to 239

1110

A network service category for special and multicast networks. Address assignments range from 224.0.0.0 to 255.255.255.0

Class E

240 to 255

1111

A network service category for experimental networks.

layer encapsulation is modified or replaced for compatibility. IP Multicast over ATM MLIS Internet Protocol multicasting over Multicast Logical IP Subnetwork (MLIS) using ATM multicast routers. A model developed to work over the Mbone, an emerging multicasting internetwork. Designed for compatibility with multicast routing protocols such as RFC 1112 and RFC 1075. By the late 1990s, IP multicasting was becoming an important mechanism for the delivery of broadcast data over the Internet and thus multicast technologies must be both flexible and robust to handle the demand of thousands or millions of users “tuning” in to the same Internet broadcast “station.” See enhanced TV. IP over ATM Internet Protocol over ATM. Implementing ATM involves the coordinated work of many computer professionals and market suppliers of networking products and services. As ATM is a broadly defined format intended to handle a variety of media over a variety of types of systems, there is no one simple explanation for how IP over ATM is accomplished. A number of subnet types need to be supported, including SVC and PVC-based LANs and WANs. There are also a number of relevant peer models, and end-to-end data transmission models, including Classical IP, TUNIC and others. See asynchronous transfer mode for general information. See the appendix for diagrams and information about layers. See Internet Protocol, RFC 1577, RFC 1755, RFC 1932. IP over ATM Working Group Now merged with the ROLC Working Group to form Internetworking Over NBMA (ION). See Internetworking Over NBMA. IP Payload Compression Protocol IPComp. A lossless Internet Protocol (IP) compression scheme for reducing the size of IP datagrams, submitted as a Standards Track RFC by Schacham et al. in September 2001. The protocol increases overall performance for hosts with sufficient computational power communicating over slow/congested links. Compression is applied before any fragmentation, encryption, or authentication processes. In addition, in IPv6, outbound datagrams must be compressed before the addition of a Hop-by-Hop Options header or a Routing Header, since this information must be examined en route. In IPComp, datagrams are individually compressed/decompressed, since they may arrive out of order (or not at all). Inbound processing must support both compressed and noncompressed IP datagrams and decompression is carried out only after security processing has been handled. In IPv4, compression is applied starting at the first octet following the IP header, continuing to the last datagram octet. The IP header and options are not compressed. In IPv6, IPComp is an end-to-end-type payload and must not be applied to routing and fragmentation headers. In IPv6 compression is applied starting at the first IP Header Option field that does not carry information needed by nodes along the delivery path. The compressed payload size must be in whole octets.

A number of applications of IPComp have been described, including IPComp using LZS (RFC 2395), IPComp using ITU-T V.44 packet method (RFC 3051) and IPComp using DEFLATE (RFC 2394). See RFC 3173 which obsoletes RFC 2393. IP Security IPsec. A security architecture developed in the mid-1990s to resolve some of the issues of conducting secure transactions on the Internet, particularly business-to-business and electronic commerce transactions. The architecture encompasses protocols, associations, and algorithms for security, authentication, and encryption. IPsec works at the IP network layer (contrast with Secure Sockets Layer) to provide packet encryption from a choice of encryption algorithms ranging from public-key encryption to secure tunneling. Originally, IPSec worked with an MD5 hashing algorithm, but this was found to be vulnerable to “collision” attacks, and reinforcement for MD5 and algorithm independence was added in later drafts. IPsec protocols are developed through an IETF working group. They may be optionally implemented into IPv4 but are mandatory for IPv6. IP switching Technology intended to improve transmission speeds and provide consistent bandwidth for Internet Protocol (IP) switching. In conjunction with a network, IP switching seeks to bring transmission speeds up to the capability of the underlying physical transport medium. It does so by reducing delay in IP routing processing and by making the data transfer mechanism more circuit- than packetswitched. IP Telephony WG iptel group. A working group of the IETF focused on research and development related to the propagation and routing of information for Voice-over-IP (VoIP) protocols. The iptel group defined the Telephony Routing over IP (TRIP) protocol. See Telephony Routing over IP. IPATM See Internetworking over NBMA. IPCE See interprocess communication environment. IPComp See IP Payload Compression Protocol. IPL See initial program load. IPng IP Next Generation. See IPv6. IPngWG IPng Working Group. A chartered Internet Engineering Task Force (IETF) group developing the next generation Internet Protocol known as IPv6. Members of the Working Group come from various telecommunications industries, including suppliers of data network hardware, network software, and the telephone industry. IPO See Initial Public Offering. IPRA See Internet Policy Registration Authority. IPS See Internet Protocol Suite. IPSec See IP Security. IPSec Working Group A division of the Internet Engineering Task Force (IETF) working on standards specifications for the IP Security protocol (IPSec). Ipsilon Flow Management Protocol In ATM packet networking, a protocol for instructing an adjacent node to attach a layer label to a specified Internet

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Protocol (IP) packetflow to route it through an IP switch. The label facilitates more efficient handling of the flow by providing access to information about the flow without consulting each individual IP datagram. This enables the flow to be switched rather than routed. IFMP comprises the Adjacency Protocol and the Redirection Protocol. IFMP messages are encapsulated within an Internet Protocol version 4 (IPv4) packet. The IP header signals the IFMP message in its protocol field. It is used in conjunction with the General Switch Management Protocol. See flow, General Switch Management Protocol. Ipsilon IP switch A commercial switch from Ipsilon, which identifies a stream of Internet Protocol (IP)

datagrams for the IP source and destination addresses, and determines if they form part of a longer series. The Ipsilon Flow Management Protocol (IFMP) and General Switch Management Protocol (GSMP) are used in conjunction with specialized hardware to map flow to an underlying network, switching direct IP datagram flows across virtual circuits (VCs). This scheme is most suitable for smaller networks. See IP switching. IPTel working group The IP Telephony working group, within the IETF Transport Area, formed in the late 1990s. IPTel focuses on issues related to propagation of routing information for Voice-over-IP (VoIP) protocols. It is responsible for a syntactic framework for call processing and gateway attribute

Internet Protocol Version 6 (IPv6) Format 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Version| Traffic Class | Flow Label | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Payload Length | Next Header | Hop Limit | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Source Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Destination Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Version

4-bit Internet Protocol (IP) version number = 6

Traffic Class

8-bit traffic class field

Flow Label

20-bit flow label

Payload Length

16-bit unsigned integer. Length of the IPv6 payload, i.e., the rest of the packet following this IPv6 header, in octets. Any extension headers present are considered part of the payload, i.e., included in the length count. If this field is zero, it indicates that the payload length is carried in a Jumbo Payload hop-by-hop option.

Next Header

8-bit selector. Identifies the type of header immediately following the IPv6 header; uses the same values as the IPv4 Protocol field

Hop Limit

8-bit unsigned integer. Decremented by 1 by each node that forwards the packet. The packet is discarded if Hop Limit is decremented to zero.

Source Address

128-bit address of the originator of the packet

Destination Address

128-bit address of the intended recipient of the packet (possibly not the end recipient, if a routing header is present)

distribution protocols. The group has defined the Telephony Routing over IP (TRIP) protocol to handle calls that need to be routed between domains. See iCalendar, Telephony Routing over IP. IPv4 Internet Protocol, Version 4. Developed in the early 1980s, IPv4 was the Internet Protocol for the 1990s, expected to be superseded sometime in the next decade by IPv6. IPv4 features 32-bit addressing, which is suitable for local area networks and widely used there, but no longer sufficient to support the exploding demands on the Internet. See IPv6, RFC 791. IPv6 Internet Protocol, Version 6. The Internet is a large, complex cooperative network supporting dozens of operating systems and types of computer platforms, tied together with many different circuits, cables, switches, and routers. As can be expected in a system this diverse, a flexible, farsighted vision of its future is needed to ensure not only that the technology does not become entrenched and obsolete compared to new technologies that are released, but also that it continues to retain the flexibility to provide universal access, much as is guaranteed by law for North American telephone systems. As such, its evolution is of interest and concern to many, and designers and technical engineers have labored long hours to propose future deployments and to develop transition mechanisms to allow the Internet to remain a living upgradable technology. IPv6 is a significant set of network specifications first recommended by the IPng Area Directors of the Internet Engineering Task Force (IETF) in 1994 and developed into a proposed standard later the same year. The core protocols became an IETF Proposed Standard in 1995. IPv6 is sometimes called IP Next Generation (IPng). IPv6 was blended from a number of submitted proposals and designed as an evolutionary successor to IPv4, with expanded 128-bit addressing, autoconfiguration, and security features, greater support for

extensions and options, traffic flow labeling capability, and simplified header formats. See 6bone, CATNIP, ICMP, Internet Engineering Task Force, IPv4, X-Bone, TUBA, Simple Internet Transition, SIPP, RFC 1752, RFC 1883, RFC 1885. IPv6 addresses 128-bit identifiers for interfaces, and sets of interfaces, with each interface belonging to a single node. In most cases, a single interface may be assigned multiple IPv6 addresses from the following types: Anycast, Multicast, or Unicast. IPv6 extension headers Separate headers are provided in IPv6 for encoding optional Internet-layer information. This information may be placed between the header and the upper-layer header in a packet. These extension headers are identified by distinct Next Header values. In most cases (except for Hop-by-Hop headers), these extension headers are not examined or processed along the delivery path until the packet reaches the node identified in the Destination Address (DA) field of the header. Thus, extensions are processed in the order in which they appear in a packet. Extension headers are integer multiples of 8 octets, with multioctet fields aligned on natural boundaries. Extension headers in original drafts of IPv6 include Hop-by-Hop, Type 0 Routing, Fragment, Destination, Authentication, and Encapsulating Security payload. If more than one is used in the same packet, a sequence must be followed, both in listing and processing the extension headers. Details can be seen in the extension headers chart. See IPv6 Extension Headers chart. See RFC 1826, RFC 1827. IPv6 flow A sequence of packets uniquely identified by a source address combined with a nonzero flow label. The packets are sent between a specified source and destination in which the source specifies special handling by the intervening routers. This may be accomplished by resource reservation protocol (RSVP) or by information in the flow packets that may be specified by extension headers. There may be multiple

IPv6 Extension Headers Extension header

Notes

Hop-by-Hop Option

Unlike other headers, requires examination at each node.

Jumbo Payload Option

Used for packets with payloads longer than 65,535 octets. May not be used in conjunction with a fragment header.

Routing Header (Type 0)

Lists one or more intermediate nodes through which the transmission must pass. Similar to the IPv4 Loose Source and Record Route.

Fragment Header

Used by a source to send a packet larger than would fit on the path MTU, as fragmentation in IPv6 is performed only by source nodes.

Destination Options

A header used to carry optional information which is only examined at the packet’s destination node.

No Next Header

A value (59) in any IPv6 header or extension header which indicates that nothing follows the header.

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flows at one time, in addition to traffic not associated with a flow, and there is no requirement for packets to belong to flows. IPv6 flow label A 20-bit field in the IPv6 header. Packets not belonging to a flow have a label of zero, otherwise the label is a combination of the source address and a nonzero label, assigned by the flow’s source node. Flow labels are chosen uniformly and pseudo-randomly within the range of 1 to FFFFFF hexadecimal, so routers can use them as hashkeys. IPv6 from IPv4 developments Some of the changes proposed for improving and updating IPv4 incorporated into the draft documents for IPv6 include: • increased address sizes (from 32 to 128 bits) and addressable nodes • simplified autoconfiguration of addresses • increased scalability of multicast routing • new addressing provided through anycast addressing • simplification of header formats • improved support for extensions and relaxed limits on length of options • flow labeling of packets to provide special handling capabilities • removal of enforcement of packet lifetime maximums • increased support for security, authentication, data integrity, and confidentiality IPv6 header format The header format of IPv6, described in the draft RFC document, is shown in the chart below. IPv6 over Ethernet networks IPv6 packets are transmitted over Ethernet in the standard Ethernet frames. The IPv6 header is located in the data field, followed immediately by the payload and any padding octets necessary to meet the minimum required frame size. The default MTU size for IPv6 packets is 1500 octets, a size which may be reduced by a Router Advertisement or by manual configuration of nodes. IPv6 over Token-Ring networks Frame sizes of IEEE 802.5 networks have variable maximums, depending upon the data signaling rate and the number of nodes on the network ring. Consequently, implementation over Token-Ring must incorporate manual configuration or router advertisements to determine MTU sizes. In a transparent bridging environment, a default MTU of 1500 octets is recommended in the absence of other information to provide compatibility with common 802.5 defaults and Ethernet LANs. In a source route bridging environment, the MTU for the path to a neighbor can be found through a Media Access Control (MAC) level path discovery to access the largest frame (LF) subfield in the routing information field. IPv6 packets are transmitted in LLC/SNAP frames in the data field, along with the payload. IPv6 security The IPv6 Draft specifies that certain security and authentication protocols and header formats be used in conjunction with IPv6. These are

detailed separately as IP Authentication Header (RFC 1826), IP Encapsulating Security Payload (RFC 1827), and the Security Architecture for the Internet Protocol (RFC 1825). IPv6 transition IPv6 is a very significant development effort intended to supplant IPv4, the circulatory system of the Internet. Commercial implementation of IPv6 began in the late 1990s. Manufacturers and software developers are, in a sense, overhauling the Net in order to support the updated standard. As part of the transition process, the 6bone testbed project has been set up to provide testing of IPv6 and various transition mechanisms. This provides a virtual version of IPv6 that can run on existing IPv4 physical structures. Various mechanisms for providing IPv4/IPv6 interoperability are being developed, including the Simple Internet Transition (SIT) set of protocols. SIT provides a mechanism for upgrade intended not to obsolete IPv4, but rather to gradually phase in IPv6, protecting the connectivity and financial investment of the many IPv4 users. IPX See Internetwork Packet Exchange. IR See infrared. IRAC 1. infrared array camera. 2. See Interdepartment Radio Advisory Council. 3. internal review and audit compliance. IRC 1. integrated receiver decoder. A type of satellite receiving device which can be integrated with a multiplexer. This device is used in digital TV broadcasting, especially with MPEG-2 encoded information. 2. See International Record Carrier. 3. See Internet Relay Chat. IrDA See Infrared Data Association. IRE See Institute of Radio Engineers. IREQ interrupt request. On interrupt-driven systems such as widely distributed Intel-based desktop microcomputers, the insertion and use of a PCMCIA card causes an interrupt request signal to be generated to notify the operating system to suspend the current operation and temporarily process the request from the hardware devices attached via the PCMCIA interface. See interrupt, IRQ. Iridium A series of low Earth orbit (LEO) communications satellites sponsored by Motorola. Iridium satellites began operations in the late 1990s. They incorporate FDMA/TDMA techniques and provide truly global voice, data, facsimile, and GPS services. The name is based upon the original estimate that 77 satellites would be needed to blanket the Earth, matching the element Iridium in the periodic table. The number of satellites needed for global coverage has been reduced to 66 (which were operational by 2002), but the name has remained. IRIS A Macintosh-based videoconferencing system from SAT which provides video capabilities over ISDN lines with JPEG-encoded graphics. See Cameo Personal Video System, Connect 918, CU-SeeMe, MacMICA. Irish Internet Association IIA. A professional association supporting, educating, and representing those doing business via the Internet from Ireland, founded in 1997. http://www.iia.ie/

IrLAP See InfraRed Link Access Protocol. IRQ interrupt request. A system of implementing computer processor interrupts that is not common to all computer architectures, but which is characteristic of a large number of Intel-based microcomputers. Many desktop computers can readily accommodate several peripheral devices by just plugging them in and installing a software device driver. However, since Intel interrupt-driven machines are prevalent and some of the most frequent hardware configuration problems encountered by users on these systems are related to IRQ assignments, this section provides extra detail to assist users in configuring their systems. If a system locks up, freezes, or fails to recognize a new device, or a device which was working before a new device is installed, it may be due to an IRQ conflict. When using an application program and an interrupt occurs, a signal is sent by the computer operating system to the processor which tells it to pay attention to the signaling process and temporarily suspend the current process. The IRQ is a number assigned to a specific hardware interrupt. The types of devices for which the system requires hardware interrupts

include hard drives, CD-ROM drives, mice, joysticks, keyboards, scanners, modems, floppy diskette controllers, sound cards, and others. IRQs are limited in number and some are reserved for specific tasks. A peripheral device often comes with a controller card that fits into an expansion slot inside the computer. Sometimes there are small dip switches or jumpers on the controller card or on the device itself (or both), which are set at the factory to a preferred, default, or mandatory IRQ number. On systems that use a manual IRQ system for hardware devices, it is necessary to assign the interrupts to a corresponding device and a good idea to keep a list of the assignments. On older ISA bus systems, almost the whole process had to be done by hand by the user. With later EISA and Micro Channel buses, there is software assistance for detecting and managing IRQ assignments and sometimes it is possible to set the IRQs through software, rather than changing dip switches or jumpers. In earlier systems, interrupts could not be used by more than one device at a time, some were reserved, and only eight were available in total. To complicate

Interrupt Request (IRQ) Numbers and Functions IRQ # INT

Notes

0

08h

Reserved for system timer.

1

09h

Reserved for keyboard.

2

0Ah

Reserved for linking (chaining, cascading) upper eight interrupts through interrupt #9.

3

0Bh

Serial port COM2 and sometimes COM4.

4

0Ch

Serial port COM1 and sometimes COM3.

5

0Dh

Originally assigned to a hard disk controller on 8-bit systems, later 16-bit versions reserved this for a second parallel port (usually designated LPT2). May be available for use by a soundboard, parallel printer, or network interface card (NIC).

6

0Eh

Reserved for floppy diskette controller.

7

0Fh

Reserved for first parallel printer, usually designated LPT1, by some software applications programs (e.g., word processors), but not reserved by the operating system, and thus may be available.

8

70h

Reserved for realtime CMOS clock.

9

71h

Reserved. Used for connection between lower eight and upper eight interrupts. Chained to interrupt #2. In some systems, used for graphics controller.

10

72h

Available. Often used for video display cards.

11

73h

Available. May be used for a third IDE device.

12

74h

Available, although it may be used by a bus mouse (e.g., PS/2 mouse).

13

75h

Reserved for math coprocessor-related functions.

14

76h

Reserved for non-SCSI controllers. Typically used for IDE drives (typical IDE devices include CD-ROM drives, cartridge drives, and hard drives).

15

77h

Available. Sometimes used for SCSI controllers, or a second IDE controller.

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matters, some devices had to be associated with a specific interrupt, reducing the number of possible interrupt combinations on a system with several devices. The IRQ may need to be changed in two places: on the computer system and on the controller card or device. To accommodate more devices, more recent machines added a second interrupt controller, increasing the total number of interrupts to 16 (though again, not all were available, as some were reserved or used for linking). In general, lower IRQ numbers are higher priority than higher IRQ numbers when two are signaled at the same time, except that IRQs 3 to 8 come after IRQ 15 in priority. Some peripheral controllers come factory set to a specific interrupt and cannot be changed. Two such cards with the same IRQ requirement cannot be used in the computer at the same time. There are situations where users actually must physically swap out cards to switch between devices. It is wise to ask about IRQ settings when considering the purchase of “bargain-priced” peripherals. The Interrupt Request Numbers chart on page 405 shows various interrupts, including notes about those which are specialized or reserved for certain types of devices, and those which may be available, provided they are not already assigned to another device or already dynamically allocated by a Plug and Play device. INT refers to the software interrupt association with a command. Two signal lines are used for interrupts; the second is used for parity errors. Since the interrupt system created administration and configuration problems for users on machines with several devices, some vendors developed the Plug and Play system, which works in conjunction with Windows 95 to ease the burden of setting and tracking interrupts manually. While this doesn’t change the architecture of the system and while not all vendors have followed Plug and Play standards, it nevertheless assists users in managing their systems. See Interrupt Request Numbers and Functions chart. See interrupt, Plug and Play. IRR See Internet Routing Registry. IRSG See Internet Research Steering Group. IRTF See Internet Research Task Force. IS-54, IS-136 See North American Digital Cellular. ISA 1. See industry standard architecture. 2. See Instrumentation, Systems, and Automation Society. 3. Instrumentation Society of America. See International Society for Measurement & Control. 4. Interactive Services Association. ISACA See Information Systems Auditability and Control Association. ISC 1. international switching center. 2. See Internet Software Consortium. ISC2 International Information Systems Security Certification Consortium. See International Information System Security Association. ISCA See International Speech Communication Association.

ISD 1. See incremental service delivery. 2. Internet Standards document. ISDN Integrated Services Digital Network. ISDN represents one of the important technologies developed in recent decades to further the transition of communications networks from analog to digital. ISDN is a set of standards for digital data transmission designed to work over existing copper wires and newer cabling media. It began to spread in the late 1980s, but has not yet received widespread consumer support. ISDN is a telephone network system defined by the ITU-T (formerly CCITT), which essentially uses the wires and switches of a traditional phone system, but through which service has been upgraded so that it can include end-to-end digital transmission to subscribers. Some systems include packets and frames, as well (see packet switching and Frame Relay). Nearly all voice switching offices in the U.S. have been converted to digital, but the link to subscribers remains predominantly analog, so it has taken some time to work out the logistics of supporting competing switching methods. ISDN provides voice and data services over bearer channels (B channels) and signaling or X.25 packet networking over delta channels (D channels). B channels can also be aggregated (brought together) as H channels. ISDN provides an option for those who want faster data transfer than is offered on traditional analog phone lines, but can’t afford the higher cost of Frame Relay or T1 services. ISDN transmission is many times faster (up to about 128 Kbps) than transmission over standard phone services with a 28,800 bps modem. Since the ISDN line doesn’t have to modulate the signal from digital to analog before transmission and then demodulate it back to digital, but rather passes the digital signal through, it’s faster. It is also possible to use an ISDN line as though it were up to three lines, sending several different types of transmissions (facsimile, voice call, etc.) at the same time. A terminal adaptor (TA) is a device commonly used to adapt ISDN B and D channels to common terminal standards such as RS-232 or V.35. A terminal adaptor takes the place of a modem and is provided in much the same way – as a separate component or as an interface card that plugs into a slot. A network termination (NT1) device is also commonly used in ISDN installations, usually paid for by the subscriber and located at the subscriber’s premises. Not all cities or countries offer ISDN, but its availability is increasing. Many subscriber surcharge services, such as Caller ID, are available through an ISDN line. ISDN is available in most urban areas with a choice of two levels of service as shown in the ISDN Basic Service Types chart. ISDN ANSI standards There are many important American National Standards (ANSI) of Committee T1 related to ISDN available from ANSI. They are summarized by ANSI in the form of abstracts on the

Web. ANSI also distributes related ETSI standards documents. Here is a sampling of those available for download for a fee. See the ISDN ANSI Standards chart; it provides a good overview of the issues involved in ISDN/B-ISDN implementation. ISDN associations There are a number of professional trade associations associated with ISDN technology. Some of the more prominent national and international associations are listed here. There are also many regional (e.g., state) ISDN groups. Canadian ISDN Resource Centre CanISDN. Resources and information for residence installations of ISDN. CanISDN includes a Web-accessible database of available ISDN services. http://www.canisdn.net/ European ISDN User Forum EIUF. A user association promoting the effective use of a wellcoordinated ETSI-standardized ISDN format throughout Europe. The group has held biannual conferences since 1990 in various locations. National ISDN Council NIC. An industry trade association promoting the deployment of ISDN services formed in the early 1990s. With ISDN firmly established as a technology, the group changed its name to the Council for Access Technologies. The ISDN Council work is still archived for reference on the Web site. http://www.nationalisdncouncil.com/index.html National ISDN Registry of Customer Equipment and Ordering Codes A central registry to assist service providers in setting up ISDN lines so that their switching equipment is compatible with customers’ equipment. This uses the ISDN Ordering Codes (IOC) system, one of the National ISDN initiatives promoted by a number of ISDN associations. Using an IOC listed in an equipment instruction manual provides a service provider with the information needed to configure a newly installed ISDN line. North American ISDN Users’ Forum NIUF. Founded in 1988, the NIUF is coordinated by the National Institute of Standards and Technology (NIST). Management was established three years later through a Cooperative Research and Development Agreement (CRADA) with industry. NIUF promotes ISDN applications development, implementation, acceptance, and furtherance, and provides services and opportunities for users and implementors to communicate their needs and goals to one another. http://www.niuf.nist.gov/ Vendors’ ISDN Association VIA. A trade organization supporting the interests of vendors offering ISDN and ISDN-related equipment and services. http://www.via-isdn.org/ See ISDN. ISDN bonding protocol A protocol which facilitates the use of two ISDN bearer channels (B channels) to transmit a single data stream. The bonding protocol provides dialing, synchronization, and aggregation

services for setting up a second call. Both synchronous and asynchronous bonding are supported by various standard and proprietary protocols. ISDN Caller Line Identification CLI. A feature in which the call address of the caller is sent to the receiving device through the delta channel (D channel). This provides a means for the host router to authenticate the call and to apply any parameters which might be relevant to that particular call. ISDN interfaces When ISDN services are established, a number of links and connections are set up to provide a path for digital transmissions between the telephone switching office and the customer equipment. Each interface link in the path has been designated and commonly used equipment given names to aid in installation and clarity in intercommunicating between the customer and the installer. The ISDN interfaces diagrams (following the ISDN ANSI Standards chart) provide two common scenarios. Note that these diagrams have been simplified and that geographical and equipment variations occur. There are some differences between ISDN deployment in Europe and North America, and local geographic differences are not indicated in the diagrams. ISDN Ordering Code IOC. A system intended to facilitate the installation of ISDN services by providing the service provider with information about the customer’s equipment needed for setup and configuration and smooth operation through a standardized code associated with the model of the ISDN equipment. This code is listed by a participating ISDN equipment vendor in the user manual that comes with the equipment. Prior to the implementation of this system, it could take hours to set up a new ISDN service. IOC is a National ISDN initiative promoted by local exchange carriers (LECs), the National ISDN Council, the North American ISDN Users Forum, and Telcordia. Telcordia administers the registry and assigns an equipment supplier with an IOC upon registration. See ISDN associations/National ISDN Registry of Customer Equipment and Ordering Codes. ISDN ring signal Unlike analog lines, in which an in-band ring voltage signal is used to ring the subscriber phone to indicate an incoming call, ISDN uses an out-of-band signal, that is, a digital packet on a separate channel, in order to leave established connections undisturbed. ISEC See Information Security Exploratory Committee. ISI 1. Information Sciences Institute. Funded by DARPA, ISI carries out research, development, and technology transfer on RSVP. 2. See intersymbol interference. ISL 1. Inter-Switch Link. A Cisco Systems proprietary protocol that maintains virtual LAN information as network data traffic moves between switches and routers. 2. ISDN Signaling Link. ISM 1. See Industrial, Scientific, and Medical. 2. interstellar medium.

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ISDN ANSI Standards Num./Year Revis.

Title

T1.113-1995 T1.236-2000 T1.604-1990 (R2000) T1.603-1990 (R2000)

Signaling System No.7, ISDN User Part Signaling System 7 (SS7) – ISDN User Part Compatibility Testing Minimal Set of Bearer Services for the ISDN Basic Rate Interface Minimal Set of Bearer Services for the ISDN Primary Rate Interface

TR No. 7 TR No. 15 TR No. 47

3 DSO Transport of ISDN Basic Access on a DS1 Facility Private ISDN Networking Digital Subscriber Signaling System Number 1 (DSS1) – Codepoints for Integrated Services Digital Network (ISDN) Supplementary Services Digital Subscriber Signaling System Number 1 (DSS1) Codepoints for Integrated Service Digital Network (ISDN) Supplementary Services (Supersedes TR No. 47)

TR No. 62

T1.219-1991 (R1998) T1.217-1991 (R1998) T1.239-1994 T1.218-1999 T1.216-1998 T1.602-1996 (R2000) T1.241-1994 T1.625-1993 (R1999) T1.620-1991 (R1997) T1.619-1992 (R1999) T1.616-1992 (R1999) T1.613-1991 (R1997) T1.612-1992 (R1998) T1.611-1991 (R1997) T1.610-1998 T1.609-1999 T1.607-1998 T1.605-1991 (R1999) T1.601-1999 T1.650-1995 (R2000) T1.642-1995 (R2000)

ISDN Management – Overview and Principles ISDN Management – Primary Rate Physical Layer ISDN Management – User-Network Interfaces Protocol Profile ISDN Management – Data Link and Network Layers ISDN Management – Basic Rate Physical Layer ISDN Data-Link Layer Signaling Specification for Application at the UserNetwork Interface ISDN Service-Profile Verification and Service-Profile Management ISDN Interface Management Services ISDN Calling Line Identification Presentation and Restriction Supplementary Services ISDN Circuit Mode Bearer Service Category Description MultiLevel Precedence and Pre-Emption MLPP Service, ISDN Supplementary Service Description ISDN Call Hold Supplementary Services Digital Subscriber Signaling System No.1 DSS1 ISDN Call Waiting ISDN Terminal Adaptation Using Statistical Multiplexing Sigaling System Number 7 Supplementary Services for non-ISDN Subscribers DSS1 Generic Procedures for the Control of ISDN Supplementary Services Interworking between the ISDN UserNetwork Interface Protocol and the Signaling System No. 7 ISDN User Part ISDN Layer 3 Signaling Specifications for Circuit Switched Bearer Service for Digital Subscriber Signaling System No. 1 DSS1 ISDN Basic Access Interface for S and T Reference Points and Layer 1 Specification ISDN Basic Access Interface for Use on Metallic Loops for Application at the Network Side of NT, Layer 1 Specification ISDN Usage of the Cause Information Element in Digital Subscriber Signaling System Number 1 (DSS1) ISDN Supplementary Service Call Deflection

Num./Year Revis.

Title

T1.403.01-1999

Network and Customer Installation Interfaces – (ISDN) Primary Rate Layer 1 Electrical Interfaces Specification (includes revision of T1.408-1990 and partial revision of T1.403-1995) OAM&P – Extension to Generic Network Model for Interfaces between Operations Systems and Network Elements to Support Configuration Management – Analog and Narrowband ISDN Customer Service Provisioning ISDN Supplementary Service Normal Call Transfer ISDN Explicit Call Transfer Supplementary Service ISDN Call Park Supplementary Service ISDN Conference Calling Supplementary Service

T1.250-1996

T1.632-1993 (R1999) T1.643-1998 T1.653-1996 (R2000) T1.647-1995 (R2000)

B-ISDN (Broadband-ISDN) T1.657-1996 (R2000) T1.658-1996 (R2000)

T1.663-1996 (R2000) T1.644-1995 (R2000) T1.635-1999 T1.629-1999 T1.662-1996 (R2000) T1.656-1996 (R2000) T1.665-1997 T1.664-1997 T1.654-1996 T1.646-1995 T1.640-1996 T1.652-1996(R2001) T1.645-1995

T1.638-1999 T1.637-1999 T1.636-1999 T1.630-1999 T1.627-1993 (R1999) T1.511-1997 T1.624-1993

B-ISDN Interworking between Signaling System No. 7 B-ISDN User Part BISUP and Digital Subscriber Signaling System No. 2 (DSS2) Extensions to the Signaling System No. 7 – B-ISDN User Part, Additional Traffic Parameters for Sustainable Cell Rate SCR and Quality of Service (QOS) B-ISDN Network Call Correlation Identifier B-ISDN Meta-Signaling Protocol B-ISDN ATM Adaptation Layer Type 5 Common Part – Functions and Specification B-ISDN ATM Adaptation Layer 3/4 Common – Part Functions and Specification B-ISDN ATM End System Address for Calling and Called Party B-ISDN Interworking between Signaling System No. 7 B-ISDN User Part BISUP and ISDN User Part (ISUP) B-ISDN Overview of B-ISDN NNI Signaling Capability Set 2, Step 1 B-ISDN Point-to-Multipoint Call/Connection Control B-ISDN Operations and Maintenance Principles and Functions B-ISDN Physical Layer Specification for User-Network Interfaces Including DS1/ATM (Supersedes T1.624-1993) B-ISDN Network Node Interfaces and Inter Network Interfaces Rates and Formats Specifications B-ISDN Signaling ATM Adaptation Layer – Layer Management for the SAAL at the NNI B-ISDN Signaling ATM Adaptation Layer – Service-Specific Coordination Function for Support of Signaling at the Network Node Interface (SSCF at the NNI) B-ISDN ATM Adaptation Layer – Service-Specific Coordination Function for Support of Signaling at the User-to-Network Interface (SSCF at the UNI) B-ISDN ATM Adaptation Layer – Service-Specific Connection Oriented Protocol (SSCOP) B-ISDN Signaling ATM Adaptation Layer (SAAL) – Overview Description B-ISDN ATM Adaptation Layer for Constant Bit Rate Services Functionality and Specification B-ISDN ATM Layer Functionality and Specification B-ISDN ATM Layer Cell Transfer Performance B-ISDN User-Network Interfaces Rates and Formats Specifications (Superseded by T1.646-1995)

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ISDN Interfaces – Two Examples

R INTERFACE

S INTERFACE

NT1 T INTERFACE

TELEPHONE SWITCHING OFFICE

V INTERFACE

line exchange switch

U INTERFACE

ISDN Interface Configuration More Common in North America

NT2

TE-1

TE-1

Terminal Adapter

Network Termination

TE-2

network exchange switch

CUSTOMER PREMISES

TE-1

network exchange switch

NT1 Network Termination

R INTERFACE

U INTERFACE

TELEPHONE SWITCHING OFFICE

V INTERFACE

line exchange switch

S/T INTERFACE

ISDN Interface Configuration More Common in Europe and Japan

Terminal Adapter

TE-1

TE-1

TE-2 CUSTOMER PREMISES

TE-1

The above diagrams are simplified illustrations of ISDN connections as they are commonly configured in North America and in Europe and Japan. The V interface refers to the link between the public telephone network and the local line switch connecting to the customer’s ISDN service. The U interface is the link between the telephone switching office’s line exchange switch and the Network Termination (NT) device at the customer’s premises. In North America, where the customer typically owns the NT device, the NT converts the S interface into a T interface. This is the point at which North American and European and Japanese systems differ. In Europe and Japan, the NT device is typically owned by the telephone provider and includes NT2 functionality. It is capable of connecting multiple devices through the S/T interface. The S interface or the S/T interface refers to the link between the NT device and either a Terminal Adapter (TA) or devices that have a TA built in (that are directly ISDN-compatible). The NT device in either configuration can connect to devices that have a TA built in. Some of the newer facsimile machines and telecommunications devices may be directly ISDN-compatible and peripheral cards are available for computers that serve as TAs. Or, the TA can provide an interface to devices that are not directly ISDNcompatible, such as non-ISDN facsimile machines, telephones, computer modems, etc. In cases where a TA is used, the R interface refers to the link between the TA and the Terminal Equipment (TE-1). In cases where a TA is not used, the NT device connects directly to the TE-1. In the European configuration, the Network Termination device (NT1) converts the 2-wire U interface link to a 4-wire S/T interface link and can handle multiple devices. The S interface and the T interface are electrically compatible and, in general, ISDN lines go through an NT1/2 or NT2 interface. Due to incompatibilities between the two ISDN systems, some manufacturers are supplying equipment that supports both U interface and S/T interface connections. (Diagrams copyright 2001 Classic Concepts; used with permission.)

ISMC See International Society for Measurement and Control. ISNI See Intermediate Signaling Network Identification. ISO See International Organization for Standardization. (In North America, it is sometimes called the International Standards Organization.) ISO 9000 series A series of quality standards developed in the 1980s for documenting a company’s processes and procedures. The ISO 9000 guidelines further track the implementation of what has been documented. Audit, certification, registration, and accreditation programs exist for ISO 9000 and are mandatory in some industries, particularly for manufacturers and parts suppliers. The full family of ISO standards, including ISO 9001, ISO 9002, and ISO 9003 encompasses more than 20 standards and guidelines, documented with examples in the ISO brochure “Selection and Use of ISO 9000” (ISBN 92-67-10267-2). The chemical, electrical, and medical industries were some of the first to adapt ISO 9000 guidelines. http://www.iso.ch/ ISO 9660 A prevalent CD-ROM logical file format standard introduced by the High Sierra Group in 1986. It was subsequently adopted by both ISO and ECMA. It is published as ECMA-119, “Volume and File Structure of CD-ROM for Information Interchange.” This compact disc standard aims at portability and future evolution and is widely supported for multiplatform CD-ROM applications. See Yellow Book standard, CD-ROM. ISO 14000 series A family of standards and guidelines relating to management and the environment. ISO 14000 documents what an organization does to minimize harm to the environment through its activities. Adaptation of ISO 14000 standards can potentially reduce waste management costs, lower distribution costs, and improve a company’s corporate image. See ISO 9000 series. ISO/OSI Reference Model A hierarchical model of communications systems that is the basis for a number of implementations of services and protocols intended to be open for communication with other systems of various kinds. In other words, it is a model for implementing heterogenous computer networks so that they may readily intercommunicate with one another through a common networking model. The model was developed in the late 1970s by the International Organization for Standardization (ISO). The ISO Basic Reference Model for Open Systems Interconnection defines communications types, layers, and the interfaces among them. Among these layers, the model prescribes how the various levels and entities should interact with one another. It does so independently of the specific programming languages, operating systems, or application interfaces selected to run in conjunction with the framework provided by the model. Adoption of the ISO/OSI Model has not been as widespread as the adoption of Internet models and protocols and a comparison between the two reveals some of the reasons. Documentation for the ISO/OSI

was not as freely available as comments and standards related to the Internet. The model is more complex and systematic (as compared to the somewhat organic evolution of the Internet) and thus has been wrung through a longer, more arduous process of administrative hurdles. Nevertheless, the ISO/OSI is well-known and many vendor systems intended for international markets implemented some or many of its architectural features. The basic model has been adapted in many aspects of computer networking and forms the basis of the European Community (now the EU) multination network integration effort. See International Organization for Standardization, Open Systems Interconnect. ISOC See Internet Society. isochronous 1. Uniform signals with embedded timing information, or which depend on an external timing mechanism. 2. In communications, a system in which the transmitter and the receiver use data clocks with the same nominal rate, although not truly synchronous. 3. In data transmission, a process using a specified number of unit intervals between any two significant instants. See asynchronous, constant bit rate, synchronous. Isochronous Media Access Control IMAC. In Fiber Distributed Data Interconnect (FDDI) networks, a specification for network bridging and access control in an isochronous environment. The IMAC interacts with one or more circuit-switched multiplexers carrying a variety of media that require a constant bit rate and continued connection. Together with the HMUX, the IMAC comprises the HRC element that is FDDI-II. See Media Access Control. isogonic 1. Exhibiting relative growth or relative scaling, such that individual size relations remain the same. 2. In magnetism, an imaginary line connecting points on the earth with the same magnetic declination (deviation from geographic north). See agonic, magnetic equator. isotropic 1. Exhibiting consistency in values or characteristics along axes in all directions, often from a central point or point of origin. This concept is used to describe certain physical objects, wave transmissions, and various scientific models. 2. In telecommunications, waves that radiate in all directions at the same time so the leading edge of an unimpeded wave emitted from a single point would form a spherical shape. isotropic antenna An antenna which radiates in all directions at the same time. Since physical conditions will impede the transmission of waves in some directions, Earth antennas are not isotropic. The phrase is useful for distinguishing this type of antenna from those which direct or concentrate a beam and, also, as a theoretical model. An isotropic antenna is a useful reference point for describing signal variations such as antenna gain. ISP 1. See Internet Safety Policy. 2. See Internet Services Provider. 3. Information Services Platform. 4. ISDN Signal Processor. ISPBX Integrated Services Private Branch Exchange.

I

ISSA Information System Security Association. ITAA See Information Technology Association of America. ITAC See Information Technology Association of Canada. ITAR See International Traffic in Arms Regulations. ITI, ITIC See Information Technology Industry Council. ITM See Information Technology Management. ITR See International Telecommunication Regulations. ITRC 1. See Information Technology Research Center. 2. See Information Technology Research Centre. ITS 1. See Institute for Telecommunication Sciences. 2. See Intelligent Transportation Systems. ITU, ITU-T See International Telegraph Union, International Telecommunications Union. ITU-T Recommendations A significant and extensive series of standards and publications to guide industry implementors and vendors in manufacturing and deploying telecommunications technologies. The Recommendations are used worldwide and form the core for many standards efforts by other professional associations; they were originally published as CCITT Books (some of which are still in effect). With the changeover from CCITT to ITU-T, the continuing effort has been disseminated through booklets since 1990. Some Recommendations have been translated into Arabic, Chinese, and Russian at the discretion of a collaboration of member countries. For those interested in acquiring recommendations,

there is a publication lag between the approval date for a new Recommendation, and the date at which the information is disseminated in print or CD format. In some cases, software and/or test charts accompany a Recommendation to aid service operators, manufacturers, and others to test relevant devices or networks. For an understanding of the range and scope of these important telecommunications development guidelines, see the lists of entries under individual series names, e.g., V Series Recommendations. In brief, the Recommendations in force fall into the general categories and are described in further detail under dictionary entries for each series. An overall summary is listed in the Appendix in the ITU-T Series Recommendations Overview chart. See International Telecommunication Union. ITV interactive TV. See interactive television. IU interface unit. See interface device. IVDS Interactive Video Data Services. A service described by the Wireless Telecommunications Bureau (WTC) of the Federal Communications Commission (FCC) as a means of promoting innovative services and products for telecommunications. IVHS See Intelligent Vehicle Highway Systems. IVI See Intel Video Interactive. IVR See interactive voice response. IVS 1. interactive voice service. See interactive voice response. 2. See interactive video service. IW 1. interworking. 2. intraworking. IWA See Intelligent Workstation Architecture. IWS See intelligent workstation. IXC interexchange carrier. See long-distance carrier.

J .jpeg, .jpg File extension conventions commonly used on JPEG-format files. See JPEG, JPEG file format. J symb. joule. See joule. J box See junction box. J Series Recommendations A series of ITU-T recommendations providing guidelines for the transmission of television, sound program, and other multimedia signals. These guidelines are available as publications from the ITU-T for purchase from the Net. Since ITU-T specifications and recommendations are widely followed by vendors in the telecommunications industry, those wanting to maximize interoperability with other systems should be aware of the information disseminated by the ITU-T. A full

list of general categories is listed in Appendix C and specific series topics are listed under individual entries in this dictionary, e.g., G Series Recommendations. See J Series Recommendations chart. J- keys A historic series of telegraph keys labeled J-1, J-2, J-3, etc., up to J-51 (as far as we know) that were used by the U.S. Army Signal Corps and the U.S. Navy. The J-36 and J-38 are popular with collectors as they can be found in garage sales and flea markets. Many are still in use by amateur radio operators. L. Nutting has authored a guide to J-keys entitled J-series Telegraph Keys of the U.S. Army Signal Corps. There isn’t room to list all the models, but the J-Series Telegraph Keys chart includes a small selection.

J-Series Telegraph Keys – Examples Key J-2 J-3 J-4

J-7A J-30 J-36

J-41 J-38

Description A basic brass and black telegraph key with an oval frame mounted on a rectangular base. A simple squarish folding key mounted in a rectangular wood base. These have a homemade look to them. A long, narrow quiet key with an enclosed section and rubber bumpers to dampen the sound of the key. It may have been used in classroom exercises where noise had to be minimized or may have been used for light signals training. A simple, compact, streamlined, heavy-duty telegraph key that looks like it was intended to be rugged (for field work?). It is one of the earlier keys, available around the early 1920s. These keys were apparently mounted on Bakelite, a new synthetic at the time, incorporated into many types of electronic products for several decades. A popular J-series key manufactured during World War II under several labels, including the Lightning Bug name. The Vibroplex J-36 was distributed from the mid-1930s to the mid1940s. A J-36 was also distributed by the Lionel Corporation, a company well-known for toy trains. Bunnell made many telegraph keys, including a version of the J-36 called the Bunnell Speed Key, Model 5-27. Brooklyn Metal Stamping Co. had a version as well. A key similar to the J-36, but with extra contacts for attaching a field set. A version of the J-series keys used for training radio telegraph operators during World War II and up to the time of the Korean War. As with the J-36, there was more than one manufacturer building these keys. Signal Electronics, Lionel Corporation, and Speed-X vended J-38 keys, which are generally manufactured in brass and black, and mounted on black rectangular bases. Unlike the J-36 keys, which often had metal labels, the J-38 keys were usually stamped simply with J-38 in white on the base.

J

ITU-T J Series Recommendations

J.73

General Principles, Terms, and Definitions J.1

Terms, definitions and acronyms applicable to the transmission of television and sound-program signals and of related data signals J.2 Guidelines on the use of some ITU-T Recommendations in the J series J.12 Types of sound-program circuits established over the international telephone network J.13 Definitions for international soundprogram circuits J.51 General principles and user requirements for the digital transmission of high quality sound programs J.64 Definitions of parameters for simplified automatic measurement of television insertion test signals J.85 Digital television transmission over long distances – general principles J.110 Basic principles for a worldwide common family of systems for the provision of interactive television services

J.74 J.75

J.77

J.80

J.81

J.88 J.92

J.141

Transmission J.142 J.52

J.53

J.54

J.55

J.56

J.57 J.61

J.68

Digital transmission of high-quality sound-program signals using one, two or three 64-Kbps channels per mono signal (and up to six per stereo signal) Sampling frequency to be used for the digital transmission of high-quality sound-program signals Transmission of analog high-quality sound-program signals on mixed analogand-digital circuits using 384-Kbps channels Digital transmission of high-quality sound-program signals on distribution circuits using 480 Kbps (496 Kbps) per audio channel Transmission of high-quality soundprogram analog signals over mixed analog/digital circuits at 320 Kbps Transmission of digital studio quality sound signals over H1 channels Transmission performance of television circuits designed for use in international connections Hypothetical reference chain for television transmissions over very long distances

J.144

J.145

Use of a 12-MHz system for the simultaneous transmission of telephony and television Methods for measuring the transmission characteristics of translating equipment Interconnection of systems for television transmission on coaxial pairs and on radio-relay links Characteristics of the television signals transmitted over 18- and 60-MHz systems Transmission of component-coded digital television signals for contribution-quality applications at bit rates near 140 Mbit/s Transmission of component-coded digital television signals for contribution-quality applications at the third hierarchical level of ITU-T Recommendation G.702 Transmission of enhanced definition television signals over digital links Recommended operating guidelines for point-to-point transmission of television programs Performance indicators for data services delivered over digital cable television systems Methods for the measurement of parameters in the transmission of digital cable television signals Objective perceptual video quality measurement techniques for digital cable television in the presence of a full reference Measurement and control of the quality of service for sound transmission over contribution and distribution networks

Human Factors, Interfaces J.117 Home digital network interface specification J.140 Subjective picture quality assessment for digital cable television systems J.143 User requirements for objective perceptual video quality measurements in digital cable television Distribution, Service Delivery J.83

J.84

Digital multiprogram systems for television, sound and data services for cable distribution Distribution of digital multiprogram signals for television, sound and data services through SMATV networks

J.86

J.87

J.90

J.93

J.113 J.119 J.120 J.150

J.151 J.161

J.162

J.163

J.164

J.167

J.182

J.184 J.166 J.168 J.169

Mixed analog and digital transmission of analog composite television signals over long distances Use of hybrid cable television links for the secondary distribution of television into the user’s premises Electronic program guides for delivery by digital cable television and similar methods Requirements for conditional access in the secondary distribution of digital television on cable television systems Digital video broadcasting interaction channel through the PSTN/ISDN RF remodulator interface for digital television Distribution of sound and television programs over the IP network Operational functionalities for the delivery of digital multiprogram television, sound, and data services through multichannel, multipoint distribution systems (MMDS) RF remodulator interface for digital television Audio codec requirements for the provision of bidirectional audio service over cable television networks using cable modems Network call signaling protocol for the delivery of time-critical services over cable television networks using cable modems Dynamic quality of service for the provision of real time services over cable television networks using cable modems Event message requirements for the support of realtime services over cable television networks using cable modems Media terminal adapter (MTA) device provisioning requirements for the delivery of real time services over cable television networks using cable modems Parameter sets for analog interface specifications for the interconnection of set-top-boxes and presentation devices in the home Digital broadband delivery system: outof-band transport IPCablecom Management Information Base (MIB) framework IPCablecom Media Terminal Adapter (MTA) MIB Requirement IPCablecom Network Call Signaling (NCS) MIB Requirements

J.180 User requirements for statistical multiplexing of several programs on a transmission channel J.181 Digital program insertion cueing message for cable television systems Testing, Measurement, Performance, Interference J.11 J.14 J.15 J.16 J.17 J.18 J.19

J.21

J.22 J.23

J.24

J.25

J.26 J.27 J.31

J.32

J.33

J.34

Hypothetical reference circuits for sound-program transmissions Relative levels and impedances on an international sound-program connection Lining-up and monitoring an international sound-program connection Measurement of weighted noise in sound-program circuits Pre-emphasis used on sound-program circuits Crosstalk in sound-program circuits set up on carrier systems A conventional test signal simulating sound-program signals for measuring interference in other channels Performance characteristics of 15-kHztype sound-program circuits – Circuits for high quality monophonic and stereophonic transmissions Performance characteristics of 10-kHztype sound-program circuits Performance characteristics of 7-kHztype (narrow bandwidth) sound-program circuits Modulation of signals carried by soundprogram circuits by interfering signals from power supply sources Estimation of transmission performance of sound-program circuits shorter or longer than the hypothetical reference circuit Test signals to be used on international sound-program connections Signals for the alignment of international sound-program connections Characteristics of equipment and lines used for setting up 15-kHz type soundprogram circuits Characteristics of equipment and lines used for setting up 10-kHz type soundprogram circuits Characteristics of equipment and lines used for setting up 6.4-kHz type soundprogram circuits Characteristics of equipment used for setting up 7-kHz type sound-program circuits

J

ITU-T J Series Recommendations, cont. Testing, Measurement, Performance, Interference, contd. J.41

Characteristics of equipment for the coding of analog high quality sound program signals for transmission on 384Kbps channels J.42 Characteristics of equipment for the coding of analog medium quality soundprogram signals for transmission on 384Kbps channels J.43 Characteristics of equipment for the coding of analog high quality sound program signals for transmission on 320Kbps channels J.44 Characteristics of equipment for the coding of analog medium quality soundprogram signals for transmission on 320Kbps channels J.66 Transmission of one sound program associated with analog television signal by means of time division multiplex in the line synchronizing pulse J.62 Single value of the signal-to-noise ratio for all television systems J.63 Insertion of test signals in the fieldblanking interval of monochrome and color television signals J.65 Standard test signal for conventional loading of a television channel J.67 Test signals and measurement techniques for transmission circuits carrying MAC/packet signals J.94 Service information for digital broadcasting in cable television systems J.101 Measurement methods and test procedures for teletext signals Privacy, Security J.91

Technical methods for ensuring privacy in long-distance international television transmission J.95 Copy protection of intellectual property for content delivered on cable television systems J.100 Tolerances for transmission time differences between the vision and sound components of a television signal Interactive Systems J.111 Network independent protocols for interactive systems J.112 Transmission systems for interactive cable television services

J.114 Interaction channel using digital enhanced cordless telecommunications J.115 Interaction channel using the global system for mobile communications J.116 Interaction channel for local multipoint distribution systems J.118 Access systems for interactive services on SMATV/MATV networks J.200 Application environment for digital interactive television services MPEG J.82

Transport of MPEG-2 constant bit rate television signals in B-ISDN J.89 Transport mechanism for componentcoded digital television signals using MPEG-2 4:2:2 P@ML including all service elements for contribution and primary distribution J.96 Technical method for ensuring privacy in long-distance international MPEG-2 television transmission conforming to ITU-T J.89 J.131 Transport of MPEG-2 signals in PDH networks J.132 Transport of MPEG-2 signals in SDH networks J.183 Time division multiplexing of multiple MPEG-2 transport streams over cable television systems Supplements J.Sup1 Example of linking options between annexes of ITU-T Recommendation J.112 and annexes of ITU-T Recommendation J.83 J.Sup2 Guidelines for the implementation of Annex A of Recommendation J.112, “Transmission systems for interactive cable television services” – example of Digital Video Broadcasting (DVB) interaction channel for cable television distribution J.Sup3 Guidelines for the implementation of Recommendation J.111 “Network independent protocols” – example of Digital Video Broadcasting (DVB) systems for interactive services J.Sup4 Terminology for new services in television and sound-program transmission J.Sup5 Guidelines on the use of some ITU-T Recommendations in the J series J.Sup12 Intelligibility of crosstalk between telephone and sound-program circuits

J-carrier A telecommunications system used in Japan, based on the T-carrier system previously standardized in North America. J-carrier is functionally similar to T-1, but some of the specifics differ (e.g., framing and line coding) so that the two are not directly compatible. It is a digitally multiplexed communications carrier system. See trunk carrier for a chart of transmission rates and number of voice channels. See E-carrier, T-carrier. J-hook connector, J-hook A piece of J-shaped metal or tough plastic (like an unbarbed fish hook) used as an attachment device, often on the end of a cable or elastic fastener. A J-hook is open-ended and thus is mainly intended for quick attachments and detachments where the orientation of the attached objects doesn’t cause them to disconnect from the force of gravity. It is also useful for temporary attachments. When J-hook attachments are used for underwater tools and sensors, a float may be attached to the top to anchor the hook and mark its location. J-hook connectors may be used to support long lengths of cable to prevent them from contacting the ground or bottom of a conduit while still enabling the cable to be easily moved, replaced, or pulled through the hooks. A J-hook tree is a series of J-hooks on one supporting rod or stem. The hooks may be staggered or adjacent and may be on one side or several sides. This facilitates the stringing of several wires along a “virtual” or open conduit. In these types of applications, the J-hook may be coated with an insulating material or, if the J-hook connector is made of conductive materials, shielded wires may be used. See J-pole antenna. Contrast with snap-hook. J-Phone Communications Co. Ltd. One of the largest mobile telephone operations in Japan, with a majority share held by the Vodafone Group in the U.K., J-Phone is the mobile telephony branch of Japan Telecom. J-Phone utilizes Packet Personal Digital Cellular (PPDC) technology, similar to the General Packet Radio Service (GPRS) used for GSM in Europe. Third-generation (3G) network equipment is supplied to J-Phone by Nokia, a prominent mobile equipment supplier. J-pole antenna A type of simple, long single-mast antenna named for its vertical waveguide and shorter horizontal-to-vertical connecting J-like stub. It is an end-fed 1/2-wavelength antenna with the J portion of the antenna being a 1/4-wavelength voltage transformer. The J-pole antenna may be used with short-range, low-power frequency-modulation (FM) transmitters and is of interest to amateur packet radio enthusiasts. It is practical for a range of frequencies and can be built by home hobbyists or purchased commercially. It is commonly constructed from copper pipe. There are a number of Web-based J-pole design pages that allow you to type in a desired operating frequency to calculate the dimensions for the J-pole antenna parts. J-SAC Journal on Selected Areas in Communications, published by the IEEE. Each issue is devoted

to a specific technical topic. Guest editors review articles for inclusion, with topics selected by the J-SAC Editorial Board. Topics range across many communications topics including ultra wideband radio, wireless communications, security, and more. J-scope A type of circular radar screen which shows only the range of objects being detected. J-Sky A mobile Internet access service offered by J-Phone Communications. J/LOCK A commercial Java-based cryptography library distributed by STI. It provides cryptography algorithms and interfaces for creating security systems and secured knowledge management systems. J/LOCK is based upon the Java Cryptography Architecture (JCA). It implements public key algorithms, message digest algorithms, and symmetric key algorithms and supports basic and commonly used security protocol data units and PKI profiles. J2ME Java 2 Platform, Micro Edition. The Sun Microsystems Java programming language platform edition for consumer and embedded device space. J2ME has two configurations, the Connected Device Configuration (CDC) using the classic Java virtual machine, and the Connected Limited Device Configuration (CLDC), using the K Virtual Machine for severely constrained memory environments. See Java. jabber Continuous (erratic or incessant) transmission of inappropriate, corrupted, or meaningless data (garbage), usually beyond the normal protocol interval. A network device broadcasting its availability redundantly is said to be jabbering. Jabber may have limited diagnostic uses, but is mostly fault-related, from a variety of causes such as software bugs, excessive packet lengths, signal degradation, incompatible systems, hardware defects, or weather-related hardware aberrations or failures. Consequences range from bad data to system lockups. jabber control, jabber lockup A protective mechanism to inhibit faulty data transmission caused by an overrun of data packets. See jabber. Jablochkoff, Paul (1847-1894). A Russian telegraph engineer who directed telegraph communications between Moscow and Kursk until 1875. En route to America, he stopped in France, where he joined the laboratory of Louis Bréguet (1804-1883), an electric clock and telegraph supplier to the French railways and navy. While working in the Parisian lab, Jablochkof invented the Jablochkoff Candle arc lamp. His invention was awarded a U.S. patent in 1877 (#252,646). The English patent was taken by Robert Applegarth who developed a business from the candle. See Jablochkoff Candle. Jablochkoff Candle The first widely distributed arc lamp, utilizing upright, parallel carbons separated by a narrow layer of plaster. The Candle was developed in 1876 by a Russian telegraph engineer, Paul Jablochkoff, and put into preliminary use in 1877. Compared to previous arc lamps, the Candle had a simpler design, making it amenable to fabrication and inexpensive distribution. The main disadvantage

J

of the design was that the carbons had to be replaced if the lamp was switched off. Arc lamps for consumer and commercial lighting were gradually replaced by filament lamps between World War I and the 1940s. In the current semiconductor industry, arc lamps are used in optical etching of circuits. See arc lamp; Jablochkoff, Paul. JACAL A symbolic mathematics system written by Aubrey Jaffer. JACAL runs in Scheme or Common LISP. jack A contact junction between circuits consisting of a male or female receptacle at one end and usually a line at the other end. The jack portion typically has a protrusion and is colloquially known as the male end. Jacks come in a great variety of shapes and sizes. RJ-, RCA, and BNC jacks are commonly used in telephone, video, and networking installations. jack in To attach oneself to an electronic system. To log on, or interact with a system through worn devices, such as data gloves, body suits, or implanted electronic components, especially those connected to the human nervous system. Often used colloquially to refer to interaction with virtual environments, where there is the illusion of “being” in the virtual space as opposed to maintaining a separation from it. See avatar, virtual reality. jack panel A board or panel configured with several jacks or with plugs for inserting several jacks, for organizing or centralizing a number of related circuit connections. See cordboard, switchboard. jacket A sheath that covers a cable to provide protection and sometimes outer insulation, as well as organization and identification. The jacket may bundle a group of related wires or fibers, and can enhance identification through colors, patterns, or materials, e.g., red and green are commonly used to identify tip and ring in phone wires. jacking In underground wiring installations, a dig/ install/haul process carried out together for efficiency. Jacking is the process of pushing a casing through a hole large enough to accommodate the casing as the hole is dug just ahead of the installation of the casing, and the loosened soil is mucked back through the pipe. The trench created in the process is called a jacking pit. Jacquard, Joseph-Marie (1752-1834) An innovative French industrialist who devised a way of automating the storage and retrieval of loom patterns by punching the patterns into cards. This innovation met with strong objections from workers fearful of losing their livelihoods, which is what eventually happened. See Babbage, Charles; Jacquard loom; punch cards. Jacquard loom A type of automated loom that worked with pattern-encoded punch cards. This loom was devised by Joseph-Marie Jacquard in France in the late 1700s and early 1800s. The holes punched in the cards indicated whether or not a thread was to be woven into the pattern. By associating each card with a color, it was possible to quickly weave complex patterns, and the cards could be modified one by one and recombined, or stored and used in later

projects. This caused a revolution in the textile industry. While the idea of encoding information with holes or slots had been used prior to the Jacquard loom, e.g., in music boxes, this large-scale industrial application was significant. It also served as a model for the storage of data and programs in large-scale computers a century and a half later. See punch cards. JAD joint application design. JAE See Java Application Environment. jag 1. distortion caused by errors between the transmitter and the recording device, as in a facsimile. 2. distortion or staircasing (aka jaggies) which is an artifact of displaying an image in a resolution too low for the amount of information conveyed. See jaggies. jaggies colloq. In image processing, a descriptive term for aberrations that often occur when the resolution of an image is too complex for the resolution of the device on which it is displayed or printed. The result is a “staircased,” “aliased,” or jagged appearance, especially along edges where there is a sharp contrast or transition from one color or tone to another. Not much can be done with jaggies in monochrome images, but in gray scale or color images, jagged transitions can be smoothed with a technique called antialiasing. This involves selecting intermediate tones between the contrasting elements to visually create the illusion of a transition. Since human perception tends to want to blend such elements, it appears as a smoother line or shape. The technique of antialiasing is often used in the display of images on computer monitors because the resolution is relatively low on this medium, usually about 75 dpi, as contrasted with print, which is usually 300 to 2400 dpi. See antialias. jam An accidental or deliberate fault condition which hinders or stops the subsequent flow of objects (e.g., printer paper jam) or data (radio, network, or radar signal jam). On a data network, a jam may occur if more than one device senses idle time or a window, and each device tries to send a packet at the same time, thus causing collisions. A collision may occur unintentionally or be deliberately generated to test the collision-detection response in the network. When testing this on an IEEE 802.3 network, if a station is transmitting and detects a collision event, it should stop the transmission of data and transmit a 32-bit jam signal to indicate the collision. JaM The name for one of the predecessors to the PostScript page definition language. JaM was the combined effort of John Warnock and Martin Newell at Xerox PARC in 1978, descended from work on the Design System Language originating at Evans and Sutherland in the 1970s. John Warnock credits John Gaffney with many of the essential ideas. JaM came to be used for various printing, graphics arts, and VLSI design applications. See PostScript. JAM Jini Technology Access Module. See Jini. jam signal A mechanism used in a data network to prevent redundant collisions. When a jam signal is

received by more than one device trying to send at the same time, the devices typically wait for a random period and then try again, reducing the probability that they will simultaneously attempt to resend the data and cause further collisions. See babble signal, frequency hopping, jam. jamming The blocking or obstructing of signals by physical or electronic interference. Jamming is done for reasons of political control or protests, vandalism, competitive obstruction, and national and personal security. Most types of jamming are restricted or prohibited. JAMSAT Japanese affiliate of AMSAT. See AMSAT. JAN Joint Army-Navy. The JAN specification is the forerunner of military specifications which have been superseded by the MIL designation. See MILNET. JANET Joint Academic Network. A U.K. network established in 1984 which links universities and other academic and research facilities. JANET is funded by the Joint Information Systems Committee (JISC) and developed and managed by UKERNA (formerly by JNT Joint Network Team). The broadband aspect of JANET, capable of transporting video and audio simultaneously with the JANET data, is called SuperJANET (coined in 1989). See JNT. Japan Amateur Radio League, Inc. JARL. Established in 1926 by a group of 37 radio communication enthusiasts dedicated to promoting the develop-

ment and use of radio wave technology, JARL’s first private license was granted a year later. Since then, the organization has grown and became involved in international activities. In 1985, a reciprocal operating agreement was signed between Japan and the United States. In 1986, JARL began launching a series of amateur radio satellites. JARL has the largest number of amateur radio stations of any country in the world. See JAS-1b, JAS-2. http://www.jarl.or.jp/ Japan Approvals Institute for Telecommunications Equipment JATE. A Japanese regulatory agency, established in 1984, which is roughly equivalent to the Federal Communications Commission (FCC) in the United States. JATE is authorized by the Minister of Posts and Telecommunications, under the provisions of the 1985 Telecommunications Business Law. JATE grants technical conditions compliance approval and technical requirements compliance approval for public network telecommunicationsrelated equipment. Once approval has been granted, the approval mark must be affixed to the approved equipment. For non-Japanese manufacturers seeking JATE approval for their products, engaging a good technical translator may expedite the process. Japan Electronic Industry Development Association JEIDA. A trade association promoting Japanese economic prosperity through the development of the electronics industry. http://www.jeida.or.jp/

Sampling of Java Applications Programming Interfaces Java DPI

Description

Java Media API

Java media applications programming interface.

Java Security API

The Java applications programming interface (API) for building authentication through digital signatures and other low- and high-level security features into Java programs. Support is provided for key and certificate management, and access control data. This provides a means for Java applets to be “signed” to ensure authenticity.

Java Speech API

JSAPI. The Java object-oriented open API for speech. Specifications for the development of speech recognition and synthesis applications. JSAPI supports speech dictation systems, employing very large vocabularies and grammarbased speech interactive dialog systems (command-and-control). The API provides three basic types of support: resource management, a set of classes and interfaces for a speech recognition system, and a set of classes and interfaces for speech synthesis. Related functions, speech coding and compression, are handled by the Java Media Framework and Codec support.

Java Telephony API

JTAPI. The Java telephone API designed to provide portability of telephony applications across applications and across different hardware platforms. JTAPI is a sanctioned specification extension to Java that is used in conjunction with toolkits (such as Lucent’s Passageways and Sun’s JavaTel), to serve as a guide for the creation of applications. JTAPI was jointly developed by Sun Microsystems, IBM, Intel Corporation, Lucent Technologies, Novell Corporation, and Nortel Corporation.

J

Japan Institute of Office Automation JIOA. An organization accredited by the Japanese Minister of International Trade and Industry to build and promote an information society in Japan, while fostering interactive understanding between providers and users of information technologies. Founded in July 1981. http://www.jioa.or.jp/ Japan Electronic Messaging Association JEMA. The Japanese arm of The Open Group EMA Forum promoting electronic messaging since 1992. JEMA emphasizes overseas cooperation and promotes security research and global interconnections. JEMA is a member of the Asia-Oceania Electronic Messaging Association. http://www.ema.org/ http://www.fmmc.or.jp/associations/jema/ Japan Personal Computer Software Association JPSA. A nonprofit trade association of software developers, publishers, distributors, dealers, and system integrators. JPSA carries out educational and market survey activities on behalf of its membership. http://www.jpsa.or.jp/ Japan Solderless Terminal JST. A line of commercial electronic cables developed by JST Mfg. Co., Ltd., since 1957, in Japan. JST products are used in many mobile devices, computing, photocopying, and robotics devices. The company makes many types of connectors, but is especially known for small 2to 9-pin terminal cables, jumper, PC card, and crimpstyle connectors. Japan Telecom Co. Ltd. The third largest telecommunications carrier in Japan, with over 10 million users. Japan is known for its lead in the wireless market; its wireless subsidiary is J-Phone Corporation, a holding company majority-owned by Japan Telecom and J-Phone in the late 1990s. Other nations have a stake in Japan Telecom, including British Telecommunications P.L.C. See KDDI Corp., Nippon Telegraph and Telephone Corp. See J-Phone Communications Co. Ltd. Japan, Communications Industry Association of CIAJ. A trade association committed to promoting healthy business activities and developmental efforts among telecommunications equipment manufacturers with the goal of improving the standards of living and quality of life in Japan and overseas. http://www.ciaj.or.jp/ Japan Computer Security Association JCSA. A trade association dedicated to increasing computer security awareness in Japan and assisting computer system developers, administrators, and users in developing secure computer programs, systems, and data. http://www.jcsa.or.jp/ Japan, Electronic Industries Association of EIAJ. A nonprofit trade association devoted to supporting and promoting the electronic industries of Japan. EIAJ was founded in 1948 and now has more than 500 members drawn from the consumer and industrial electronics sectors. EIAJ is involved in collaborative development projects, statistical forecasting, industry awareness, and professional development activities. http://www.jeita.or.jp/ JAR See Java Archive.

Jargon File, The The precursor to The Hacker’s Dictionary, the original Jargon File was an electronic dictionary started by Raphael Finkel in 1975 at Stanford University, and has since gone through many revisions with contributions from Mark Crispin, Guy L. Steele Jr., and the ARPANET communities. This well-known dictionary includes jargon, slang, and technospeak from the artificial intelligence (AI) and general computer communities, and is well-known to programmers worldwide. Don Woods later became the Jargon File contact, and in the early 1980s, Richard Stallman made contributions. The early 1980s also saw the first paper publications of The File and the transition to The Hacker’s Dictionary. See Hacker’s Dictionary, The. JARL See Japan Amateur Radio League, Inc. JAS-1b Japan’s second amateur radio satellite, launched in 1990, 4 years after its first satellite was put into orbit. Six years later, in 1996, this was followed by JAS-2. See JAS-2. JAS-2 Japan’s third amateur radio satellite, launched in 1996 using an H-II launch vehicle. JASON Foundation A nonprofit educational organization founded to administer the JASON Project. The JASON Foundation was established to excite and encourage students to explore science and technology, and to provide professional resources and support to teachers. See JASON Project. JASON Project An effort of the JASON Foundation established in 1989 by R. D. Ballard following the discovery of the wreck of the sunken ocean-liner, the RMS Titanic. The enormous interest in the Titanic, especially by thousands of school children, inspired the founders to dedicate themselves to developing interactive telecommunications technologies for participation in global explorations. http://www.jasonproject.org/ JATE See Japan Approvals Institute for Telecommunications Equipment. Java An object-oriented, platform-independent, threaded programming language that came into being largely because its two earliest contributors were not satisfied with C and C++, and wanted a way to develop programs with less effort and code. Thus, Bill Joy proposed an object environment based on C++ to Sun Microsystems engineers, and James Gosling, author of EMACS, developed a language called Oak. Communications between Patrick Naughton of Sun, Mike Sheridan, James Gosling, and Bill Joy resulted in the Green Project and collaborative work began. Eventually, in 1995, Java was introduced by Sun Microsystems. Java requires significantly less code than C for many types of applications, is generally easier to learn, works well in conjunction with the Web, and has a good chance of becoming a widespread language of choice for software development. On the Web it is frequently used to supplement HTML as a means to interact with and convey information to Web users. HTML is a markup language, a type of language where a user can learn a few commands and install a basic Web page without

too much technical knowledge. However, Web users with more sophisticated needs or the desire to interact with users in a more fluid and interactive manner than is possible with HTML generally select Perl and/or Java for implementing calculations, specialized interfaces, and more complex programming structures than are possible with HTML. At first, Web users were slow to adopt Java. Those who were familiar with C and other powerful, fast development languages were uncomfortable with Java’s limits and slow running times. However, Java has continued to evolve, the Web has continued to evolve (and now is accessed on faster systems and Internet links), and developers have begun to realize that there is an enormous middle ground of applications that don’t have to run as fast as C to be useful and that can be implemented far faster and more readily with Java. Examples include basic menu selections, games based on strategy rather than speed, interactive database interfaces, more sophisticated interactive forms than are possible with HTML, statistical charts and graphs, and much more. Java support from Sun includes the Java Development Kit (JDK), available for various Sun platforms, Windows NT, and Windows 95 Intel. Independent ports exist for other operating systems, including Linux, NeXTStep, and Amiga. Macintosh support is provided by Apple Computer’s Macintosh Runtime for Java (MRJ), and Windows 3.1 support is provided by IBM. Two applications environments are particularly relevant to personal communications devices. • The PersonalJava application environment is designed to facilitate development of software for private network or Web-connected consumer devices that may be executing applets. This requires that a core set of software libraries be installed on the PersonalJava-enabled device. The PersonalJava AE comprises the Java Virtual Machine (JVM) and an optimized version of the Java class library. This environment is useful in situations where generalized applications or those that can’t easily be predicted in advance will be used. The tradeoff is that the libraries require a certain amount of space. • The EmbeddedJava application environment is designed to facilitate development of software for dedicated-function embedded devices which may be stand-alone or embedded. Only the class libraries needed to support a prespecified set of tasks are installed onto the EmbeddedJava-enabled device. This is useful in very specific dedicated applications where the purpose of the device is well-defined and not likely to change in the near future. Space is saved and the resource “footprint” of the device is smaller (which often lowers the cost). The tradeoff is that future needs may not always be anticipated or met without changing the core set of library routines. Java can be used in conjunction with the HotJava Web browser to allow Java programs to run on a desktop computer.

Java information and specifications are available through the Javasoft Web site. See J2ME, Java APIs, Java applet, Java Archive, JDBC, JOLT Project, JStamp. http://www.javasoft.com/ There is a good Java Frequently Asked Questions (FAQ) listing by Elliotte Rusty Harold on the Web. http://sunsite.unc.edu/javafaq/javafaq.html Java APIs A number of important applications programming interfaces associated with Sun Microsystems’ Java provide specifications and procedures for applications development. Java applet An important component of Java objectoriented programming, an applet is a Java class used to extend Java. Applets can intercommunicate within the same virtual machine environment. Applets are run within the circumscribed context of a Web browser, applet viewer, or other application that supports applets. This provides a measure of extensibility along with a certain amount of security, since the applet can normally only read and write files on the host machine through the application through which it is running. See Java. Java Application Environment JAE. See Java. Java Archive JAR. A powerful, Java open standard, platform-independent, compression file format for images and sound that brings together a set of files into one. In this way, Java applets and their associated components can be bundled and downloaded as a single file; however, it can also be used as a general-purpose compression/archiving tool, similar to ZIP. JAR files are very small, even smaller than PKZIP files, in many cases. JAR has some support for data security. Individual portions of a JAR can be digitally signed and authenticated. JAR archives can be created with the JAR utility included with JDK, which functions in a manner similar to many common archive utilities. See PKZIP, RAR. Java Community Process JCP. An open, internationally inclusive means of developing and revising Sun Microsystems’ Java technology specifications and related support resource. More than 300 companies and individual participants are involved in this effort. Almost 100 Java technology specifications are being developed through the JCP, which was initiated in 1995. See Java. Java Electronic Commerce Framework JECF. A securable, extensible framework for conducting electronic commerce, developed by Sun Microsystems. The initial component of JECF is JavaWallet, a client-side application distributed as part of the Java Commerce toolkit as a core component of the Java environment. Java Commerce APIs are used to implement basic services within the Java Commerce Client that can be used to develop online shopping malls and banking applications. See Java, JavaWallet. Java name space A means of controlling how names in a software program are resolved to Java runtime classes. In general, the system applies to classes, packages, and class members. Classes can be moved

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or removed from specified name spaces, which can be useful for security implementations. Classes themselves are part of a package. By handling things this way, rather than with global variables, name space conflicts are avoided in environments such as the Internet where the loading of dynamic, modular applications is prevalent. A naming scheme was proposed, based on Internet domain naming conventions, to provide unique package naming that included the name of the organization developing or providing the package. Thus, a unique package name might be: com.companyname.jdbc.coolapp or, as some developers have chosen: companyname.javascript.coolObject The names java and sun are reserved by Sun Microsystems. There was some support for this concept and also some controversy. In general, developers have been following the guidelines for Java name space, but in some instances, the Java community has expressed a preference that core applications be placed within name space conventions with shorter, more generic names rather than the longer, company-linked names. See Java, Java telephony API. Java Native Interface JNI. A Java native programming interface that ensures portability of Java applications across different platforms supporting Java. It is available with the standard Sun Microsystems Java Development Kit (JDK). Since there always seem to be a few platform-specific functions that people like to use, the JNI is intended to take advantage of functionality on a specific platform that is not within the Java Virtual Machine (JVM) environment. It enables native code (e.g., C++) to be integrated into Java applications. See Java, Java Virtual Machine. Java telephony API JTAPI. Applications development tools based on the Sun Microsystems Java programming language that enable portable Java applications to set up, manage, redirect, and otherwise administer telephone calls handled through digital data networks. JTAPI was developed by IBM, Intel, Lucent, Nortel, Novell, and Sun Microsystems. JTAPI implementations provide the interface between Java telephony applications and hardware or software telephony services. JTAPI provides a means to access telephony Call Control, Physical Device Control, Media Services, and Administrative Services. JTAPI is an extensible, scalable specification appropriate for communications in first-party call control in consumer devices to third-party call control in distributed call centers. JTAPI development was begun in the mid-1990s by a consortium of computer and telecommunications companies who desired a portable, object-oriented means to integrate computers and telephony call control. JTAPI version 1.0 was released in October 1997 and version 1.3 was endorsed by the Enterprise Computer Telephony Forum in July 1999.

JTAPI is a java extension package comprising the classes, interfaces, and principles of operation in the javax.* name space (e.g., javax.swing). JTAPI makes it possible to create applications that interact with and control telephone services. This is of interest to many developers, consumers, and business users of telephone services. The more obvious applications include call management, logging, dialing, and tracking software. Automated voicemail, facsimiles, and document distribution programs are also of interest. But there are also likely to be new and novel Internet telephony and personal digital assistant programs developed and designed to interface computer and telephone technologies in ways not previously possible. Since JTAPI does not encompass every signaling protocol and since there is no way to anticipate every possible JTAPI application, some of the more innovative applications will require interfaces to extend and supplement the JTAPI specification. JTAPI can run on top of existing telephony standards, including TAPI, TSAPI, Callpath (IBM), and SunXTL. JavaTel is Sun Microsystems’ JTAPI runtime environment for the Sun platform. See Java, JavaTel, javax name space, Telephony Application Programming Interface. Java Virtual Machine JVM. Software routines for interpreting Java bytecodes into machine code. This interpretation/conversion process makes it possible to run Java applications on many different platforms. Each computer hardware architecture has a different way of interpreting programming instructions, based on the central processing unit and its support systems. If you have a software program running indirectly within a virtual environment instead of directly on the host platform, a way to convert the program instructions to those expected by the host processor is needed. The JVM enables Java portability across many different systems. See Java. Java XML, JXML An area of development and a mailing list devoted to Java and XML, particularly Java Class and Bean metadata expressed as CML documents, conversion of metadata to bytecodes, reversible conversion of Java Object Streams to XML documents, and other related issues. JavaBeans A Sun Microsystems Java language object-oriented, platform-independent security model included in JDK. See Java. JavaScript A cross-platform, scripted, open standard programming language familiar to most through the implementation incorporated into Netscape Web browsers. It is only superficially similar to Java, being slower and having a simpler syntax and limited functionality. JavaServer Pages JSP. An industry collaboration project lead by Sun Microsystems to enable Web developers to develop and maintain dynamic Web pages for integration with existing business systems. JSP enables the development of platform-independent Web-based applications. It separates the user interface from the content generation so that changes

in layout don’t change the underlying content. JSP uses XML-style tags and scripts written in Java. Formatting tags (HTML or XML) are passed back to the response page. JSP is an extension of the Java Servlet technology, platform-independent Java server-side modules that fit into a Web server framework to extend the capabilities of the server with minimal overhead. JSP specifications are freely available to the development community so that Web servers and applications servers can be JSP-enabled. See Java. JavaTel A platform-independent, scalable telephony applications toolkit based on the Java Telephony API, introduced by Sun Microsystems in 1997. JavaTel was designed to support computer telephony integration (CTI) by enabling the development of Javabased call center, voice response, Internet phone, and management applications. Thus, Java-based computer telephony applications can run on any Javaenabled device, rather than being constrained to CTI applications that run on SunXTL, Sun’s proprietary implementation. JavaTel operates with the Solaris operating system and will run on top of Sun’s earlier CTI implementation, the SunXTL system. See CallPath, Java Telephony API. JBIG Joint Bi-Level Image Experts Group. A group formed after the JPEG group to concentrate on the task of lossless compression of bilevel, one-bit, monochrome images such as those commonly generated by printers, fax machines, etc. It is officially the ISO/IEC JTC1 SC29 Working Group 1 and is responsible for both JPEG and JBIG standards. The JBIG format incorporates discrete levels of detail by successively doubling resolution. The image is divided into strips for processing, each with a horizontal bar and a specified height, with each strip coded and transmitted separately. The order and characteristics of individual strips can be specified by the user. The image can then be progressively decoded, one strip at a time, as received. Once an image has been segmented according to strips and specified parameters, the resulting bilevel bitmaps are compressed with a Q-coder. Two contexts are defined by JBIG, the base layer, which is the lowest resolution, and the remaining differential layers. These provide contexts for optimization of the compression. The JBIG format works well with the many common bilevel images that include text and line art. It is an accepted standard as ITU-T T.82. The JIBG2 standard, which represents work since the original JBIG specification, has been released as an International Standard (IS 14492). See JBIG, color; JPEG; MPEG. JavaWallet A family of products developed in the Java programming language for enabling secured electronic commerce transactions. JavaWallet incorporates the Java Commerce Client, Commerce JavaBeans components, the Gateway Security Model, and Java Commerce Messages, which may be used independently of one another and may be bundled with other applications. JavaWallet may be used in Java-enabled browsers, as well. See Java. JBIG Alliance Another name for the JPEG and

JPEG committees officially known as the ISO/IEC JTC1 SC29 Working Group 1, sometimes abbreviated as ISO SC29/WG1. See JBIG. JBIG, color; COLOR-JBIG A project to develop a JBIG-based, lossless, decompression system for document image processing for a variety of types of documents including bitonal, grayscale, and color. This is an interesting direction, since the original JBIG concept was to create, in a sense, a lossless, monochrome version of the JPEG file format. However, it is clear that a lossless color format has many applications (including commercial graphics, medical images, business documents, etc.). What remains to be seen is how a new format can improve upon the sophisticated and well-supported Tag Image File Format (TIFF) file format, which already supports lossless compression of monochrome, grayscale, and color images. Since JBIG is an ISO standard, a color version of JBIG is of interest to the European community. Presumably the developers feel that there are capabilities and aspects of JBIG not already supported by TIFF. See JBIG, Tag Image File Format. JBOD See just a bunch of disks. JCL See Job Control Language. JDBC Java database connectivity. This is a product from Sun Microsystems that facilitates the linking of Java programs to tabular databases. It provides connectivity to a number of standard database formats, including SQL, common spreadsheet formats, and flat files. See Java. JDC 1. Japan Digital Cellular. See Personal Digital Cellular. 2. Java Developer Connection. The Sun Microsystems support forum and interactive message board for registered Java developers. (Nonregistered developers can read message, but not post to the message board.). 3. Journal of Design Communication. JECF See Java Electronic Commerce Framework. JECS See Job-by-Email Control System. JEDEC Joint Electron Device Engineering Council. JEDEC was originally formed as the Joint Electron Tube Engineering Council (JETEC) in 1944. JEDEC is a standards-developing body of more than 300 member companies representing the electronics industry as part of the Electronic Industries Alliance (EIA). http://www.eia.org/ JEDI See Joint Electronic Document Interchange. JEDIC Japan Electronic Data Interchange Council, Japan EDI Council. An interdisciplinary council of member organizations, including electronics organizations, manufacturers, software developers, and trade associations. It was formed in recognition of the importance of electronic data interchange (EDI) to Japan’s consumer and industrial infrastructure and to encourage a common awareness and purpose similar to that fostered by the open EDI environments in Europe and North America. The JEDIC fosters educational, internationalization, and standardization efforts. http://www.ecom.jp/jedic/ JEEVES See Ask Jeeves.

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JEEVES DNS Resolver A significant pioneer network domain name resolver (DNS) developed by Paul Mockapetris which was the precursor to the widely used Berkeley Internet Name Domain (BIND). See Berkeley Internet Name Domain; CHIVES DNS Resolver; Mockapetris, Paul. JEIDA See Japan Electronic Industry Development Association. JEMA See Japan Electronic Messaging Association. JEPI See Joint Electronics Payment Initiative. JET See Just-Enough-Time. JFIF A minimalist implementation of the JPEG family of image compression methods. This is often the implementation incorporated into Web browsers. See Joint Photographics Experts Group. JHTML 1. An open source cross-platform HTML editor written in Java by Riyad Kalla. 2. A Mac-based plugin application for the Jedit text editor that enables it to generate HTML code. 3. See JavaServer Pages. jiffy A unit of time equal to 1/60 of a second (North America), or 1/50 of a second elsewhere. Since the proliferation of computers, other definitions of a jiffy have been used, such as 1/100 second or a clock tick in the CPU. The term is most widely used in the film and video editing industries for editing timing purposes. See SMPTE Time Code. Jini A Sun Microsystems network technology for providing a simple modular infrastructure for delivering platform-independent network services and for facilitating spontaneous interactions among programs using these services. Jini architecture, released in the late 1990s, typically consists of servers and clients registered with a lookup service. Upon registration, a client can specify the needed servers. Some interesting applications have been developed with Jini technology, which can be adapted to applications that are computationally intensive and require the resources of a network of computers. For example, researchers in the Computer Graphics and Scientific Visualization Group in Italy used Jini to evaluate a novel distributed computing environment for scientific visualization (e.g., the modeling of fluid motion over wing structures). In July 2001, GroupServe announced a Developer Web Site with expanded services for Jini technology, augmenting those offered by Sun. These include Jinibased email, database, and transaction interfaces. The services are accessed by proxies downloaded by the Jini Access Module (JAM). They can run locally or remotely, or as shared resources. See Java, Jini Community. Jini Community JiniCom. A community of Jini network services human and technical resources, JiniCom aids members in Jini development and hosts numerous community projects. It distributes the Jini Technology Core Platform Compatibility Kit (TCK) for testing Jini services for compliance to the Jini specification. To date, Jini standards distributed through the Community include the following, and more are in the draft standard stage (e.g., Internet

Protocol interconnect standards): Technology Core Platform Specification – Specifications for discovery and join protocols and formats, entry methods and templates, distributed leasing and events, transactions, and lookup services. Helper Utilities and Services – Specifications for a set of standard helper utilities and services which extend the Jini Technology Core Platform. They encapsulate desirable behaviors in the form of reusable components to simplify the server/client development process. JavaSpaces Service Specification – A distributed persistence and object exchange mechanism for code written in Java. See Java, Jini. http://www.jini.org/ JIOA See Japan Institute of Office Automation. JIPS JANET Internet Protocol (IP) Service. See JANET. JIRO A development architecture for resource management distributed by Sun Microsystems as an extension to the Java platform. It provides an open, dynamic, extensible, scalable, network-centric management framework that can be integrated as a platform-independent system. It allows complex distributed environments, such as storage area networks (SANs), to be interconnected and managed. It does this through a standard management domain, including management services for logging, lookup, scheduling, events, security, and transactions through a standardized interface. The system locates and communicates with the services as FederatedBeans components (a cooperative concept based on the JavaBeans idea). See Java, Just-Enough-Time. JIT See Just-In-Time. JITT Just-In-Time-Training. A laptop-based intelligent feedback training project for astronauts and flight operators. The program was established in the mid-1990s by the NASA/Johnson Space Center. jitter 1. Random or periodic signal amplitude or phase instability or degradation of relatively short duration. Jitter arises from various causes, including poor connections, overly long cables, incompatibilities between software and hardware, or weather. See wander. 2. Random or periodic temporal variations of short duration in a data stream. This is essentially a timing problem with relation to a clock source. With increased demand for wideband data services such as full broadcast video, reference clocks and related transmission signals become important aspects of data communications but can also provide one more source of signal interference. When expressed diagrammatically, jitter can be visualized as small timing differences between a reference clock representing the ideal signal and the jittered signal. At first glance, the two timing diagrams may look the same, but closer inspection reveals small deviations from the ideal clock backwards or forwards in time. On an oscilloscope, the jitter signal will be just slightly out of phase with the image and position of

an ideal, expected signal. Networks may be tuned to tolerate a certain amount of low-level jitter, but persistent or high amplitude jitter should be investigated or corrected. See jitter, network; wander. 3. Unstable or erratic display on a television or computer monitor where the image deviates slightly but noticeably from the expected pattern in small jerky or wavy motions. jitter tolerance Since jitter is a persistent possibility in high-performance network systems, especially those running through a number of interface devices from different vendors, many systems will specify a certain tolerance for jitter and will correct for jitter within certain parameters, when possible. The terms of the jitter tolerance depend upon the type of system, but may be specified in lost bits, timing disparities, or other characteristics. Since jitter can be transferred to an adjacent connecting device and thus can increase from one component to the next, the sum total of the jitter effects must also be below that which the system can tolerate. jitter, network In networks, jitter refers to a number of problems arising from demultiplexing, incorrect physical connectors or regenerators, and latency times between consecutive transmission packets. When data are serially transmitted, as is common in data networks, timing is a means to synchronize the data stream so the receiver can interpret, convert, or otherwise process the incoming information to make sense of the data and recover them for use on the local system or for conversion or forwarding to another system. The success or failure of this timing synchronization is partly dependent upon knowing the jitter characteristics of the transmission from previous experience or by dynamically analyzing the jitter in the incoming data stream and extracting useful information. This may be direct information such as the reference level and frequency of the signal or may be calculated to derive other information such as waveform characteristics and clock periods. In SONET and other high-speed networks, timing is quite important and lack of synchronization can cause fluctuations in the data packets with respect to the reference clock cycle. This type of phase variation can be filtered with adjustment mechanisms. Jitter specifications for SONET network interfaces are described in ANSI T1.105.03-1994, and for computer networks in general in ANSI T1.102-1993. See jitter. JitterTrack of Time Interval Error JTIE. A testing and diagnostic tool for measuring clock characteristics against a reference value with respect to short duration signal phase instabilities (jitter). The reference duration is over a specified time interval from the initiation of the time interval and is evaluated for phase characteristics and anomalies. In networks, the TIE is typically measured in nanoseconds. See jitter, network. JNT See Joint Network Team. job In computer operations, a process submitted for later execution. The term was borrowed from factory terminology in the days when computers were

large, slow, and very expensive to operate and maintain. Thus, demands for computing time exceeded resources, and it could take days or weeks for a job (a computer program) to be processed, executed, and returned to the person who submitted the job (usually on punch cards or paper tape). In those days, jobs were commonly processed in queues, sometimes according to various priorities, and eventually returned to the user. Since paper media were frequently used to store the results, the finished jobs, along with the original program, were often sorted into cubbyholes in the same manner as postal mail. Computing has changed. Systems are now fast and numerous and employ multitasking architectures. The term job is now mostly associated with background tasks and low-priority processes, or batch files that run in the background while the user continues to use the machine for other applications. Specialized applications and intensive scientific applications are still processed as jobs in the sense that they are submitted to an organizing authority (e.g., a server) and may take a long time to process, so the term is not outdated, but is much less frequently used. Job Control Language JCL. A programming language for providing user instructions to a computer operating system, usually in the format of an interpreted scripting language. Although the phrase is now used generically, it was originally developed as a control language by IBM for the control of programs on older IBM batch-based computing systems. Job-by-Email Control System JECS. A software application to facilitate communication between a remote computer (server) and a home or office computer. In other words, it enables a task to be emailed from one location to another, processed, and emailed back, rather than having it run realtime over a longdistance link. This is similar to batch processing in the days of timeshare systems, except on a larger scale over the Internet. It is an important concept and many jobs may be handled this way over large distributed networks in the future. Jobs, Steven P. (1955- ) An early entrant to the microcomputer industry, Steven Jobs began as an employee of Atari at the age of 17, hired to do video games development. Through the Home Brew Computer Club, he met Stephen Wozniak, an electronic hardware enthusiast, who was working as an engineer for Hewlett-Packard. Wozniak was designing telephone access devices and homebrew computer projects, and Jobs became interested in the business potential of these designs. By 1976 Jobs had left Atari, and he and Wozniak together created a new company called Apple Computer. They were planning to sell a microcomputer in kit form, a project probably inspired by the Altair, a humble little history-making microcomputer first released as a kit in 1974. Both Jobs and Wozniak had a strong orientation and commitment to educational markets. Jobs and Wozniak were joined by A. C. (Mike) Markkula, an Intel marketing manager, who provided a business plan and several rounds of investment

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money to help jumpstart the fledgling entrepreneurs. The Apple computer shipped at approximately the same time as Radio Shack’s Model I computer. Normally this would have shut out the young company, since Radio Shack was a large, established corporation with thousands of distribution centers; however, the Apple computer had three things the Model I didn’t have: color, expandability, and a small-townto-big-company dynamic duo to promote it. Not only did the technical features appeal to a significant number of computer hobbyists, but educators recognized the educational value of color programming for children. It also helped that Radio Shack was targeting businesses, with spreadsheets and word processors, while Apple was marketing aggressively to schools. Despite his youth, Jobs displayed a futurist orientation, charismatic personality, and marketing flair. Since then these traits have continued to keep him in the headlines for more than 20 years. Apple gained a foothold in the industry, and John Sculley was recruited to head the corporation. Under Sculley’s leadership, Apple became a billion dollar company and, as it grew, the two Steves receded into the background due to company growing pains, personal interests, and differences of opinion with the corporation, although not before becoming millionaires while in their twenties. Jobs left Apple Computer and founded NeXT, Inc. in 1985. This company designed some of the best computing hardware and software available in the 1980s. The elegantly simple hardware, robust operating system, stunning graphical user interface, straightforward built-in networking capabilities, Unix underpinnings, and various software utilities were as good as or better than many systems being sold a decade later. The NeXT hardware and operating system was aesthetic, well-conceived, and reliable; business owners, frustrated with the limitations of current business computers, watched with a keen eye when the NeXT computer was released in 1987. Unfortunately, by not cultivating the early interest from the business community and targeting education almost exclusively, Jobs may have made one of his biggest mistakes. In retrospect, he appears to have deliberately shunned the temporary window on a large potential market, as the business community subsequently became solidly entrenched in other operating systems based on Intel architectures. The NeXT did well in institutions of higher education, but didn’t penetrate other markets to any significant degree, with the result that NeXT was not highly financially successful. The NeXT corporation was acquired by Apple Computer in 1996-1997. Interest in the NeXT in 1997 was due at least in part to its very good graphical user interface and integration with Internet services, which were now becoming important to consumers. By the mid-1990s, 8 years after its introduction, the consumer learning curve had improved and users began to appreciate the NeXT design and concept. Jobs’ brash assertion in the 1980s that the NeXT was the computer for the ‘90s turned out to be more truth than bluster. During this period, Jobs was involved in other

projects besides NeXT development. A year before the NeXT was released, in 1986, he purchased the computer division of Lucasfilm, Ltd., and incorporated it as an independent company called Pixar, cofounded with Edwin E. Catmull as vice president and CTO. Jobs has long been chairman and CEO of Pixar, a creative software, multimedia, motion picture company which made history with the Academy Awardwinning “Toy Story,” a computer-generated fulllength motion picture distributed in 1995 by Walt Disney Pictures. After a few years of quiet creative work, Steve Jobs’ name again splashed across headlines in 1997 when Apple bought NeXT. Jobs was back as an executive at Apple, acting in an interim capacity, and speculation about whether he would again head Apple kept reporters on their toes. The management change and publicity created a flurry of activity at Apple, and stocks reacted accordingly. Jobs’ return to the limelight showed that public interest in his activities hadn’t declined after more than two decades. The revival of Apple Computer, at a time when analysts were predicting its demise, is in no small part due to Jobs’ presence and creative inspiration. In the early days of Apple Computer, Jobs was described as an impatient, insulting, tyrannical, and callous manager. One would expect that the maturing Jobs has tempered these characteristics while endeavoring to retain his unique vision and high standards, qualities that drove his early successes. Steven Jobs has a philosophical bent, as can be seen from his keynote speeches and interviews with major computing magazines, and it seems clear that his commitment to education and to harnessing the creative potential of computers for improving human lives is sincere. It is likely that he will never be far from the creative computing activities that will occur in the future, and will probably, in fact, be the inspirational force for many innovations yet to come. See Apple computer; Wozniak, Stephen. JOFX Java Open Financial Exchange. A Java-based toolkit from Xenosys Corporation for developing Open Financial Exchange (OFX) applications and applets. JOFX is part of the LiveBusiness Foundation Classes for Java (LBFC), a set of Java frameworks, libraries, etc. for e-commerce. See Open Financial Exchange. JOHNNIAC A historic large-scale computer built by Willis Ware, the JOHNNIAC was unveiled in 1954 by the Rand Corporation. Significantly, the first operator of the JOHNNIAC was Keith Uncapher, who became the first chair of the IEEE Computer Group, now the renowned IEEE Computer Society. See ILLIAC, MANIAC. Johnson noise In electronics, the agitation of electrons in conductors through heat creates noise in the circuit. In communications circuits, the amount of noise is related to the receiver bandwidth and source temperature. Johnson noise is sometimes also called thermal noise and is characteristically emitted by all objects with temperatures above absolute zero. An understanding of Johnson noise is important to the design and production of antennas and to noise processing and

filtering techniques in communications. The phenomenon was discovered and described by J.B. Johnson, a Bell Laboratories researcher. joining In computing, the process of combining data files or streams. In the context of packet communications, it is usually called reassembly since the packets are intentionally disassembled when they are sent. The term also refers to joining a conference, chat, or network community. Joining is one of the most important and ubiquitous functions used in data transmissions. It is very common for data to be chopped up into pieces as it is routed, especially if there is a limit to file sizes in the sending or receiving systems. Join utilities are also used in connection with large files stored across more than one floppy or more than one hard drive partition, or computer. What is split apart usually needs to be rejoined when the data are accessed or moved later on. In packet communications, individual packets from a larger data file are not necessarily transmitted through the same route in a distributed network. The concept of splitting the packets and sending them through many routes arose in the days when the U.S. military was looking for a means to safeguard data transmissions in the event of an offensive strike. It was proposed that if the data were traveling through different routes, it was less likely that the entire content would be lost. In subsequent computing applications, this was found to be a good model for many aspects of communications, including email, file transfer protocols, and much more, so joining the separate pieces of the communication at the destination became an important function of a system. In file management, individual parts of a file are often stored where there is sufficient room and are not necessarily contiguous. Pointers are used as a virtual joining mechanism to tell the file retrieval algorithms where to look for the next “chunk” of data. Thus, the joining of a block of data that has been stored in separate sections often happens when an application is run and the program requires the entire contents of a graphics or text file. In telephony and online communications, joining refers to entering a live communications venue such as a conference call, an Internet Relay Chat (IRC) talk session, or other community communication. Specific steps or commands for joining usually must be adhered to, especially in public discussions where standardized commands make it easier for people to join or leave. Joining is an important function in computer workgroups. When users on several different computers are sharing or updating the same database, for example, it is important for the applications and operating system to keep track of who is joined into the workgroup application so that searching, retrieval, updating, and other common functions are handled so that one user doesn’t wipe out the corrections or additions of another user. In client/server applications, certain protocols and procedures can be put in place for a client to join a network system or specific process. This is a resource

management tool to allocate resources on a more efficient or as-needed basis to conserve computing resources. Thus, many Internet Service Providers (ISPs) that provide 24-hour connections to the Internet, for example, may actually time out a user when a system is idle in order to allocate that user’s Internet Protocol (IP) number to another user. When activity is detected from the first user, the system must again join the network and a new IP number will be dynamically allocated to allow the user to rejoin the Internet. This process is typically transparent to the user. joint 1. Connection between two or more conductors. This may be a chemical bond, solder joint, or wires touching, clamped, or wound together. 2. A joining part, or space, between two sections, nodes, or articulations. 3. A junction where two or more structural members are combined. Joint Bi-Level Image Experts Group See JBIG. joint cache A shorter-term storage cache shared by a larger base of users or networks. Some significant joint cache proposals have been based on newly developed models for distributed network systems. Based on the premise that the Internet is a system as a whole accessed by joint users, a joint cache on the Internet is a mechanism for handling Internet traffic caching based on virtual rather than machine-specific or local-network-specific models. As an example, a dynamic joint cache system was described by Dolgikh and Sikhov at the TERENA Networking Conference 2001, based on Zipf-like distribution. The model was based on research at the Samara Region Network for Science and Education. The authors proposed and tested an analytical model of a cache system that can be used to determine the scope, frequency of requests, and maximum efficiency levels for the most requested document in a cache system. While a simple example, this is an important basic concept that can be generalized to many Internet resources, including popular, hightraffic Web pages. This and similar efforts to conceive top-down structures based on the Internet as a whole, rather than bottom-up services based on individual networks or computers, are an important trend in the Internet development community, where the sum of the parts is seen as a larger resource that should be accessible to the greater Internet community. If the trend continues, computing applications that were impossible on smaller systems may emerge as possibilities on a global distributed network. joint circuit Shared communication link. Joint Electronic Document Interchange, UCLJEDI JEDI. A project to survey, identify, and test a number of formats for electronic document interchange with an eye to standardizing the research community and facilitating the process therein. The project was initiated as the result of a call for proposals announced by UKERNA in 1994. The participants are studying popular interchange formats for word processing in academic and commercial environments. The project aims to identify format conversion methods and the relationships between de facto and internationally recognized standards.

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Joint Electronics Payment Initiative JEPI. An idea initiated by CommerceNet and W3C in 1995, JEPI was aimed at developing and demonstrating payment-selection, negotiation, and purchasing electronic commerce scenarios in order to build a commerce mechanism practical for use in real world applications and which could be published as an open standard. The initial inspiration for the technology came from Eastlake’s Universal Payment Preamble and the W3C’s PEP technology for HTTP transmissions payments. The Open Software Foundation and the Financial Service Technology Consortium were also involved in the early stages. The project was organized into four main groups including Browser Technology, Server Technology, Payments Systems, and Merchant Systems. Companies joining the effort were expected to commit to implementing the negotiation protocol in a product for testing. By August 1996, the project had progressed to where Internet Draft documents were distributed in RFC format, in view of an eventual release of an IETF specification of the Universal Payment Preamble (UPP) and the development of an HTTP Extension Protocol (PEP) in the HTTP Working Group. By August 2001, the W3C working group was specifying and recommending the syntax and processing parameters for XML signatures. The project is ongoing. See e-commerce. Joint Intelligence Virtual Network JIVN. A U.S. Government network for providing round-the-clock TS-SCI multimedia communications, including secured videoconferencing. This is one of the multimedia services supported on the Joint Worldwide Intelligence Communications System. Joint Network Team JNT. An organization established in March 1979 in the U.K. by recommendations of the Computer Board and Science Research Council (SRC) to study the networking requirements of the academic community and make proposals. The role was transferred to UKERNA April 1, 1994. Joint Photographic Experts Group JPEG (pron. jay-peg). The Joint Photographic Experts Group was founded in 1986 to develop a standard for the compression of still, continuous-tone images. Soon after its formation, its goals were adopted jointly by the International Organization for Standardization (ISO) and the International Telegraph and Telephone Consultative Committee (CCITT), now the ITU-T. Research proposals for such an image compression scheme were solicited internationally, with a deadline of March 1987. By January 1988, the evaluators had narrowed down the suggestions and selected an Adaptive Discrete Cosine Transform method, culminating in a new standard described in ISO 109181 Recommendation T.8. Following the publication of the draft standard, work began on improving compression ratios further, and providing scalability. See JPEG file format. joint pole, joint utility pole A shared telephone pole resource established in the early telegraphy and telephone days. When there were many small switch-

boards, rather than one large telephone provider, wires were everywhere, along with many poles to support them. It was not uncommon for individual wires to be running to each business and even to each neighboring business. Utility companies and subscribers and those with private lines quickly realized that the sharing of a telegraph/telephone pole had advantages, including cost, ease of maintenance, and aesthetics. Thus joint poles were designated for carrying transmission lines belonging to more than one entity. However, coordination of shared resources became an issue, so joint pole agreements and joint pole committees were established throughout the country in the early 1900s to manage joint poles. As electrical power superseded candles and oil lamps, electrical wires were also slung along telegraph poles, which came to be known as utility poles. Utility poles are still with us and the demand for places to string communications lines has increased dramatically since the mid-1990s. Cable TV and fiber optic Internet access cables now share space with the telephone and electrical lines on utility poles. Deregulation has also complicated the administration of poles as to who is responsible for their installation, maintenance, and use. Joint pole committees are still important, perhaps more than ever. New communications companies, seeking to establish services at reasonable costs, have a vested interest in joint pole agreements and have shown interest in being involved in joint pole committees in their distribution areas. Some relatively standard configurations for joint poles have developed over the years. In general, the poles are strung in a hierarchical arrangement from top to bottom, based upon the the electrical characteristics of the lines strung and the frequency with which they may need to be changed or serviced. Since ground wires aid in deflecting energy discharges from lightning and rarely need to be serviced, they are placed at the top. Moving down the pole, various primary and secondary transmission wires are connected. The more recent cable TV or fiber optics bundles running between poles are usually fat, well-shielded cables attached near the bottom, often running in bundles held together with short straps. On poles with several types of transmission lines, certain distances are maintained between different types of wires to reduce electromagnetic interference. With fiber optic cables, which use light rather than electricity to transmit information, electrical interference isn’t a problem except at points where the fibers are connected through electrical amplifiers or where the signal is converted to run on wires. However, optical fibers are dependent upon carefully designed splices and joints and, when bundled, don’t have the same bend tolerances as small wires, so these factors need to be taken into consideration for fiber more than for wire. The design of insulators and connecting mechanisms on joint poles is also dependent upon the types of cables and power distribution levels carried on the pole. See joint trench, Joint User Service. See the joint pole illustrations and more detailed explanation on the following pages.

Joint Procurement Consortium JPC. A Bell consortium composed of a number of regional Bell holding companies including Ameritech, BellSouth, Pacific Bell, and SBC Communications, which reviews telecommunications product offerings and makes recommendations. In 1996, the JPC signed contracts with Alcatel for ADSL equipment for use over twisted copper pair networks as an alternative to fiber. Joint Technical Committee JTC. The JTC is now called JTC 1. It is an International Standards Organisation/International Electrotechnical Commission (ISO/IEC) information technology standards body concerned with the specification, design, promotion, and development of systems used for the capture, representation, and processing of information. http://www.jtc1.org/ joint trench A means of aggregating cable installations so more than one department or company can share space within a single conduit or other wiring distribution system to save money and to limit the number of individual conduits installed in public areas. For utility services, guidelines and regulations require that other companies using a joint conduit must be contacted before any street upheaval or digging is undertaken. This is important in order to limit the disruption that inevitably occurs when major line changes or installations are made under or near public streets. See joint pole. Joint User Service A tariffed, Federal Communications Commission (FCC) system for buying or otherwise sharing telecommunications services by mutual agreement. Local public utility service regulations have restrictions on how certain services may be shared and may require that all associated users be identified. See joint pole, joint trench. Joint Worldwide Intelligence Communications System JWICS. A U.S.-secured global multimedia intelligence communications system. The system replaces the Defense Data Network’s (DDN’s) DSNET3 as the Sensitive Compartmented Information (SCI) portion of the Defense Information System Network (DISN) and is intended to facilitate the rapid exchange of audio/visual data. Data includes videoconferencing, graphics and scanned document files, Defense Intelligence Network (DIN) broadcasts, etc. JWICS was initially set up on a switched T1 backbone with T1 and, in some cases, slower connections, with a plan to transition to faster T3. Much of the communication is relayed via satellites. The system is designed to be installed at all major command sites in addition to the availability of portable versions such as the Mobile Integrated Communications System, which uses a self-contained JWICS system packaged into a set of transit cases. The lead contractor for the system is the Defense Intelligence Agency (DIA). The goal of a secure system is not easily realized. In 1999 there were concerns about monitoring individual user activity on INTELINK as accessed through JWICS. It was realized that there were circumstances where unaudited use could be carried out

if local access control (LAC) was not carefully implemented and contained. Until the configuration problems could be solved, it was recommended that government contractor access be limited to authorized individuals accessing the system through sites where U.S. Government or military personnel were available to oversee. See Joint Intelligence Virtual Network. JOLT Project Java Open Language Toolkit Project. A collaborative effort to produce a freely-distributable “clean-room” clone of Sun Microsystems’ Java sufficiently compatible to pass Sun’s Java validation suite. The participants instituted a plan to develop a development-quality Java compiler, an embeddable Java interpreter with a full class library, and documentation for all the JOLT components. The initial implementation was targeted for Linux/i386. It was also planned to embed JOLT into a freely distributable, full-featured Web browser. See Java. Jones plug A multicontact polarized receptacle connector. Josephson effect A quantum effect, which is not easy to explain, but as an example, imagine a nonsuperconducting material, such as a semiconductor or nonconductor, sandwiched between layers of superconducting material, so that the supercurrent tunnels through the nonsuperconductor and can variously be affected by magnetic fields. See Josephson junction. Josephson junction A fast data technology sometimes used in place of silicon that provides a means to do very fast circuit switching. Josephson junctions can be connected together in series, provided their oscillating properties are matched. This is difficult, but has been achieved in devices called Josephson arrays. Josephson junctions have practical applications in many areas, but are of particular interest to researchers and engineers working with precision voltage metering, microwave electronics, and hightemperature superconductors. Named after British researcher Brian Josephson. See Josephson effect. Josephson, Brian (1940- ) A Welsh-born British physicist who received a Nobel Prize for physics in 1973 for his discovery of the Josephson effect. See Josephson effect, Josephson junction. Joshi effect 1. In electronics, when alternating current is passed through a gas dielectric condenser and the gas is continuously irradiated with certain wavelengths of light, the associated fall or rise in the current is called the Joshi effect. 2. Similar to a theoretical model called the Prisoner’s Dilemma (known to game theorists), Joshi is named for a Reed student from India who proposed a model for behavior on the stock market that is particularly relevant in light of direct trading activities as they occur over the Internet (as opposed to traditional trading that was more often filtered through brokers). As in the Prisoner’s Dilemma, people may well be better off not trading at all (not confessing), but given the social and economic dynamics, it’s hard to resist. Joshi has proposed that with so many involved, the market becomes more fragmented and volatile with the result that it may become more difficult to achieve any gains.

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Joint Utility Pole Examples

A terminal (end) utility pole. Wires are aerially strung to only one side of the pole and a guy supports the other side. The lines on end poles may be terminated or may feed into a vertical conduit for connection to nearby underground wiring facilities.

Joint Utility Poles These two photographs illustrate somewhat different utility poles located several blocks apart. The one on the left is a terminating pole, connecting conducting wires on only one side of the pole with conduits for channeling lines to the ground. The pole on the right is a more common mid-block pole that primarily supports the lines and passes them along to the next pole (and to local utility subscribers) without ending the connections or directing them earthward. Both poles include a variety of wires, cables, insulators, and transforming devices. In spite of their geographic and functional differences, these two poles clearly have many common structural characteristics, arising from various joint utility pole regulations and agreements. Most of the structural aspects have been worked out over the decades based upon electrical characteristics and safety and maintenance needs. Recently, the role of joint utility poles has become more complex. Not only has the demand for phone services increased, but additional types of

A mid-block utility pole in which wires are supported and passed on to the next pole in the path and to the nearby buildings of local utility subscribers. Not all poles have transformers, but three are shown here, in cylindrical metal housings.

media, including copper-based high-speed data lines and fiber optic cables, have been added to the joint pole hierarchy, often severely stretching the space and weight limitations of joint poles, especially in densely populated urban areas. The problems of interference have increased as well. High-speed copper data lines, for example, have special needs that are different from voice lines. The loading coils added as induction structures to reduce attenuation (loss of signal) on voice lines may help facilitate voice transmissions over longer distances but they can also increase interference in high-speed data lines. Utility Pole General Characteristics Most utility poles are made of wood, usually cedar or fir, although some regions have poles made of metal or cement. Wood and metal poles are generally between 20 and 30 feet in height. Depending upon the type of pole and the terrain, the setting depth is usually about 4 or 5 feet into the ground. The accessible ground surface around the curb is termed the grade.

Joint Utility Pole Regions (Spaces) and Common Components

POWER SUPPLY/ CONVERSION SPACE

higher voltage (primary) power conductor insulator (usually ceramic) crossarm – structural support for multiple power lines secondary power conductor (to supply nearby residences and businesses) stepdown transformer – steps down the voltage from the higher voltage conductors to secondary conductors leading to residences and businesses

COMMUNICATIONS SPACE

NEUTRAL SPACE

cable TV (CATV) bundle – there may be two CATV cables, one for the cable trunk line and one for the feeder (attached lower on the pole with connecting drops between the two)

There are often various cylindrical or boxshaped metal cabinets attached to a pole. These have a variety of functions. They may contain battery or other auxilliary power supplies (usually located higher up on the poles), may include tools or components, or may be cabinets associated with CATV installations (usually located lower on the pole than the CATV cable). Mounting brackets must be designed and attached so they are strong enough to withstand the effects of wind, or the minor collision of a vehicle with the pole. In general, in urban areas, the pole should be about 5 feet behind the face of a curb and about 6 feet from the shoulder of the road, with differences related to local speed limits and odd intersection situations that may require other solutions. In general, utility poles are not permitted to be placed in traffic islands. Highways generally require greater offsets than city streets. Hierarchical Organization of Components While there are variations, in general, higher voltage conductors are located higher up on the pole, for safety and to minimize their effects on data-carrying lines. In most cases, conducting wires are required to be at least 12 feet from the

CATV loops, line extenders telephone wire bundle various amplifiers, power inverters, and line extenders may be located on conducting wires within arm’s reach of the utility pole vertical wire casing/conduit utility closet (typically holds power supply/backup battery for CATV) grounding rods and wires

accessible ground (grade). In some cases, where alleys or driveways are involved, the requirement may be as high as 18 feet. A static grounded wire may be at the top of the pole, to draw lightning away from the conducting wires below. The power lines carrying high voltage between power supply substations are located near the tops of the poles and there may be one or more. Secondary power lines for carrying lower voltages to local subscribers are lower than the primary power supply conductors but higher than the communications media. Stepdown transformers between the primary and secondary power lines provide voltage conversion functions. A multigrounded neutral (MGN), generally located below the primary power supply, is an uninsulated conductor for carrying unbalanced residual current. Various grounding wires and rods run down the side of the pole, as needed. There may also be terminating equipment on end poles, or conduits for connecting an end pole with underground wiring. A grounding rod at the base of the pole may be used to ground the MGN.

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JOSS Johnniac Open Shop System. A computer programming language developed by C. L. Baker at RAND in the mid 1960s. It is a simple calculator language intended to be used concurrently by a number of users at remote consoles interconnected through a timesharing system. AID (Algebraic Interpretive Dialogue) is a version of JOSS II designed for the historic Digital PDP-10. JOTP Java Open Trading Protocol toolkit under development for client/server implementations of the Internet Open Trading Protocol (IOTP). JOTP clients are implemented as protocol commerce beans for the Java Wallet. JOTP servers are based upon the Enterprise JavaBean and Servlet component models. Interoperability is through XML-based Open Trading Protocol transaction transport mechanisms. joule (symb. – J) An absolute meter-kilogram-second (MKS) unit of work or energy equal to 107 ergs. An SI unit of energy equal to 1 kg m2 s-2. Named after James Joule. Joule, James (1818-1889) An English physicist who studied the dynamics and efficiency of various types of engines. Joule demonstrated that when mechanical work is used in generating heat, the ratio of work to heat is a constant quantity. A joule, the absolute unit of work or energy, is named after him. Joy, William (Bill) One of the codevelopers of Sun Microsystems’ Java, attributed with the original idea for the programming language which eventually became Java. In the early 1990s, Joy met with the members of the Stealth Project to develop a language which could create short, powerful programs. See Gosling, James; Java. joystick A hardware input device that receives and transmits signals containing directional information to a computing device. Commonly used for manipulation of computer software onscreen pointers and selectors. In its most common form, a joystick resembles an aircraft steering control, and may or may not include buttons. It is commonly used for video gaming applications. See mouse, potentiometer, trackball. JPEG (pron. jay-peg) See JBIG Alliance, Joint Photographic Experts Group. JPEG file format The JPEG image compression format was designed to be used with a wide variety of continuous tone images, without restrictions as to colors, resolution, content, etc. Depending on the software used to generate the file, the format provides the user with trade-off options between compression levels and the quality (lossiness) of the image, and is symmetric, with compression and decompression requiring about the same amount of time and processing power. Common file extension conventions to identify JPEG files are .jpeg and .jpg. JPEG is not perfect for every type of image. Continuous tone images with many colors generally look good when rendered and compressed with JPEG, in spite of the substantial loss of information and reduction in file size. Crisply rendered images with few colors, sharp boundaries, and thin lines tend to take on a fuzzy or speckled appearance when compressed

into JPEG format, and should probably be processed with a different compression format more suitable for that type of image.

The image on the left is a representation of a JPEG file which is only 25K in size. On the right, the same image, stored as a TIFF file, is 150K, a substantial difference considering that they don’t look very different at this size. For Web pages and other basic representations, the JPEG image is a good choice. However, when the images are compared in detail, the differences can be seen, as the detail enlargements show below. For enlargements or high-resolution printing, lossless TIFF files give better results.

The enlargement on the left shows the fuzzy edges and speckles in the solid tone areas introduced by the lossy JPEG compression process. The TIFF file on the right has cleaner, more consistent areas of color. While the differences may not seem important at this size, they become very evident when blown up to poster or billboard size. [Illustrations by the author, copyright 1995 Classic Concepts; used with permission.]

JPEG does not support transparency. If transparency is required, another format such as Portable Network Graphics (PNG) or Compuserve Graphics Interchange Format (GIF) should be used. JPEG is not usually the best format for the storage and rendering of images to be printed on a traditional press, as it is a “lossy” format; that is, it does not retain all the information from the original. The resolutions of printed images on paper are much higher than those of renderings on a computer screen (1800 dpi vs. 75 dpi). An image that looks good on the

computer may look fuzzy and inadequate on paper. The TIFF format is generally a better choice for images to be printed, as the format retains a great deal of information about the image, while still providing reasonably good compression ratios with common compression schemes. JPEG is actually a family of compression formats and many implementations of it are quite minimal. For example, JFIF is a bare bones version of JPEG commonly found on the Web, and SPIFF has been formally defined to be upwardly compatible with JFIF. Variations on the JPEG format can often be identified by looking at the first few bytes in the file header. Work is ongoing on the newer JPEG2000 standard. See JBIG, MPEG, TIFF. JPS joint product specification. JRG GII Joint Rapporteur Group global information infrastructure. A group of rapporteurs and experts from various ITU study groups brought together to further discuss and coordinate global standards-setting tasks. JST See Japan Solderless Terminal. JStamp A commercial battery-operated one-inch by two-inch circuit containing a realtime, native Java technology module developed by Systronix. The matchbox-sized module includes a 32-bit CPU, flash RAM and SRAM, and can handle realtime hardware interrupts. It’s based on the aJile Systems Inc. chip design. The low-power-consumption module can operate up to 40 hours, depending upon the implementation. It is suitable for devices such as Personal Digital Assistants running Java applications, including graphics animations. This level of miniaturization is likely to spawn a whole host of carry-around applications that haven’t existed in the desktop world due to lack of portability and high relative cost. JTAG Joint Test Action Group. An international body, founded in 1985, JTAG seeks to develop electronics-related test methodologies and related standards. These standards are then recommended to various appropriate standards bodies, such as the IEEE. JTAPI See Java Telephony API. JTC See Joint Technical Committee. JTIE See JitterTrack of Time Interval Error. Judge Harold Greene See Greene, Harold. Jughead Named in association with other Internet tools, including Veronica, Jughead provides a means for Gopher administrators to access and retrieve menu information from the various gopher servers on the Net. They stretched a little to put an acronym to this one, but ended up with “Jonzy’s Universal Gopher Hierarchy Excavation and Display.” See Archie, Veronica, gopher, Gopher. jukebox 1. A hardware appliance or peripheral that holds and can selectively or randomly access multiple data storage items, generally of the same type, such as audio CDs, tapes or records; computer diskettes; tapes; or cartridges. For audio applications, 20 to 100 items may be accessible, and access may be very quick, whereas for archival purposes, especially with high-capacity storage tapes, there may be

5 to 20 tapes, and access may be slow. 2. A software tool for selecting and playing digitized audio or multimedia files in the manner of a traditional phonograph jukebox from the 1950s. In fact, many software jukeboxes have user interface designs that mimic old-time jukeboxes. The jukebox analogy is now being extended to multimedia resources on the Web. Users can store their original audio or multimedia files on a Web site and users can access the jukebox through a Web-page interface as a shared resource. jukebox management High capacity jukebox storage on a network may be accessed by a variety of users with different priority access levels. Thus, a rack of selectable hard drives, CDs, or DVDs can be housed in a location where it can be more easily secured and serviced and users can remotely select the device or storage medium of their choice. Since this can be a tricky process if some resources are more popular than others or if a lot of people are using the service, Jukebox management software has been designed to detect, sort, prioritize, and deliver user data requests. Security and priority levels may vary from industry to industry and installation to installation, so some customization may be needed to enjoy efficient jukebox management. Julian calendar A solar-based calendar in widespread use (some traditions use a lunar calendar) in the western world that arose historically from calendar reform instituted by Julius Caesar, after his conquest of Egypt. The Julian calendar is based on a 365-day year divided into 12 somewhat equal months with leap years used to reconcile the difference between the calendar divisions and actual celestial events (like adjusting a clock that runs slightly fast or slow in relation to clocks based on accepted time references). After some initial experimentation with leap years, they were standardized to occur every 4 years. The actual solar year is slightly shorter than the Julian solar year, which is 365.25 days with the 4-year leap year convention. In the short run, this discrepancy doesn’t bother most people but for theologists, farmers, and scientists (especially astronomers), the discrepancy can be important, especially since it adds up: after a century, the calendar is almost a day out of synch with the actual solar year. By the time the Italian Renaissance came about, when intellectual curiosity was high and systematic observations were being strongly established, the calendar was reformed, with input from a number of astronomers and theologians. In 1582, Pope Gregory XIII issued a papal bull establishing the Gregorian calendar, setting October 5, 1582, in the old calendar to October 15, 1582, in the new calendar, to synchronize the administrative calendar with the solar calendar. The day for using the leap year adjustment was changed as well, from February 25 to February 29. In essence, however, it is the same basic type of calendar as the Julian calendar. The Gregorian calendar coexisted with the Julian calendar for centuries, being first adopted by the Catholic communities. Gradually, however, nations switched over to the Gregorian

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calendar, though many of them not until the 1900s. Historians often have difficulty pinpointing historical dates related to the advancement of science in Europe because of the coexistence of the two calendar systems. In many cases, even when a historical record is dated, it might not be definitely known which system the person who recorded the date was using. jumbo group In general, an aggregation of associated devices, transmission media, lines, or channels. In analog voice phone systems, a hierarchy for multiplexing that has been established as a series of standardized increments. See voice group for chart. jump hunting In telephony, a means of searching for an available trunk or extension in nonconsecutive order by dialing the first number of the trunk to indicate which trunk to search. Also called nonconsecutive hunting. jump scrolling A means of incrementing information on a bounded screen, such as text on a text-based computer terminal. Jump scrolling involves rewriting the screen with a full line of text moved to the next position (and everything else being updated relative to that) rather than incrementing the display pixel by pixel. Jump scrolling was very common in the 1980s. The perceptual impression is similar to watching a line printer (a true line printer, that is, not one that prints one character at a time across the line, but one that impresses the entire line at one time) as it will print a line all at once and then scroll the page up the full distance of the line to impress the next line, causing the eyes to want to jump to follow the line just read. Jump scrolling was common on computers in the 1980s because text was generated in a different manner from graphics. Newer graphics-based text displays, as implemented on the Amiga computer in 1985, provided a way to model characters as text while still manipulating them as graphics, a much more flexible system. Since smooth scrolling was more natural and comfortable to view, jump scrolling had almost disappeared by the mid-1990s except for small limited-resource handheld devices (e.g., palm devices with text-based LCD displays). jumper 1. A temporary or customized connection used to bypass or reroute a circuit, frequently in the form of a wire, often a short one; common on printed circuit boards. Jumpers are used to test circuits, correct errors, or make last minute changes in circuit board manufacture. They may also be used to set operating attributes on configurable peripherals such as hard drives (e.g., SCSI settings). Sometimes wire jumpers are equipped with alligator clip heads to facilitate quick connections. 2. A small, paired electrical protruberance on a printed circuit board, intended for configuring a circuit with settings that are infrequent. This type of jumper is common on hard drives, where there may be a row of seven or eight jumpers. The connections are “jumped” with very small Ushaped electrical tabs with plastic casings to set SCSI ID numbers or other configuration parameters. If the circuit is jumped, the tab is placed over both prongs in the circuit to complete the electrical connection.

If not, the tab is removed or placed to one side on a single prong, so as to leave the circuit unconnected. junction box, J box A wire encasement box, made of metal or other moisture- or fire-retardant materials, commonly found in homes and businesses. Junction boxes are unassuming, usually hidden, and yet crucial to most wire and fiber transmission technologies. Every time a transmission link is interrupted, split, joined, amplified, or otherwise affected at a wiring junction, there is the possibility of damage, short circuits, noise, or loss of signal. The main functions of the junction box are • to protect the wiring from moisture, heat, or other conditions that may damage the wires or short the circuit, • to provide a means to connect sections of transmission lines so they can be combined to create a longer total line, • to protect humans and animals from accidental electrical shock from contact with the wires, and • to provide a means to readily access, connect, or change the wiring or effect repairs at a particular point in a circuit. The junction box is commonly placed at the junction or demarcation point between internal and external wiring. It may also be placed at a point in a line where other lines are split off from a main line or where sections of line are connected, or where the signal on a line needs to be amplified. In building wiring, the J box often also incorporates fuses or breaker switches to protect against overload and fire hazards. The simplest J boxes are those that house the wiring for a switch or other wire connection point in a wall or ceiling. In fiber optics applications, the terminal and connecting boxes for the optical fiber splicing and connection points are also called J boxes. Since fiber optic media are more difficult to handle and to connect than most electrical wires, J boxes for fiber optics must be built to accommodate the differences between electrical current and laser light transmissions. They may have specialized termination components and usually lock the fibers in place more rigidly and precisely than wires in an electrical J box to accommodate fiber transmission and physical properties such as orientation and preferential bend radius. Blown fiber techniques were developed in part to reduce the number of junction boxes in a fiber optic transmission line. In oceanic transmission cables, special techniques for installing and maintaining cables are necessary and the junction boxes must be built to withstand the rigors of salt and cold temperatures. They must also be designed so that connections may be changed in an underwater environment without creating short circuits. Grounding and termination are accomplished differently from land-based installations. Many of the present undersea junction installation and maintenance boats have their origins in the laying of the first transatlantic cable in the 1800s and the minelaying naval ships of World War I. Since marine junc-

tion boxes can’t be hidden within walls, they must be designed so that they don’t catch in fishing nets or interfere with nearby boating and diving activities. In radio and computer electronics, J boxes are often constructed by hobbyists to add electronic switches or components to their existing systems. The box houses the wiring connections and may include switches, buttons, status lights and connection terminals for data and power. J boxes are distinguished from interface devices mainly in that they do not provide complex data conversion or modulation functions, but focus on simple wiring circuits as an extension to the main circuit. As in many aspects of electronics, the distinction is not always clear; there is overlap between interface devices and the more advanced J boxes (sometimes called smart J boxes). Advanced electronic J boxes have been designed for industrial installations to automatically evaluate the characteristics of an electrical line and log the information or report possible problems to an operator. These are essentially a J box and associated electronic devices housed in one unit, using the J box nomenclature for familiarity in marketing the products. junctor A connective circuit extending between frames of a switching unit, terminating in a switching device on each frame, as in an internal network trunk. JUNET Japan Unix Network. A noncommercial Japanese network dedicated to promoting communication among researchers in and outside Japan. Junior Wireless Club Limited A pioneer amateur radio organization, formed in 1909. In April 1910, one of the young members, W.E.D. Stokes, Jr., made history when he represented the club before a U.S. Senate Commerce Subcommittee. As president of the club, he opposed a proposed bill to license wireless operators. Stokes also argued for a specified wavelength for amateur use to be allocated to amateur radio communications. In October 1911, the group changed its name to the Radio Club of America. See Radio Club of America. Juniper Networks A software/hardware firm backed by prominent telecommunications firms 3Com, Lucent Technologies, and Northern Telecom. It has developed routing software in competition with Cisco Systems products and a number of channelized, longhaul, and multilink hardware interface products. See Junos routing code. JUNOS routing code A router operating system (OS) announced by Juniper Networks, Inc. in 1998 that enables high-speed network forwarding across complex paths. It is competitive with the Cisco Internetwork Operating System (IOS) dominant on Internet-deployed routers. In 2001, an upgrade was released to support the use of multiprotocol label switching (MPLS) on virtual private networks (VPNs) over Internet Protocol (IP) networks. just a bunch of disks JBOD. A disk data management system in which various organizational aspects of hard disk storage may span more than one disk.

For example, some operating systems allow a user to transparently create large partitions (or file structures) that span more than one drive (as opposed to breaking up a drive into smaller segments) or even to create a file structure across more than one partition, thus making flexible use of the total virtual storage space available on a system. As an example, imagine you have three 1 GByte drives and want to save a big animation file (e.g., a movie) that takes up 2.5 GBytes of drive space. Most consumer desktop systems aren’t configured to do this; they will indicate that there isn’t enough space, even if total disk space is 3 GBytes. In a JBOD system, the file management algorithms can manage the virtual space specified and split the file and file pointers appropriately over the various disk segment boundaries. The name is likely derived from RAID (redundant array of inexpensive disks) and has some aspects in common, in that the system is used with multiple disks, but it’s not the same (in fact, it could be implemented across a RAID system). RAID is intended to provide redundancy on a system through mirroring or striping of data, whereas JBOD is intended to provide more flexible management of data across several disks. See redundant array of inexpensive disks. Just-Enough-Time JET. A network transmission protocol proposed by Qiao and Yoo in 1999 for use with optical burst switching (OBS). It embodies the use of a delayed connection reservation (DR) and the capability of integrating delayed reservation with fiber optic delay line-based buffered burst multiplexers (BBMs). JET is considered by its developers to be more efficient for use with OBS than TAG-based OBS protocols. In a given transmission path with a known number of hops, JET and OBS protocols can support multipath routing. Deflection routing can also be supported with the control packet selecting an alternate outbound link and setting the switch for the following data burst. JET does not mandate buffer use nor buffer size relative to the number of bursts or bits that can be stored or delayed simultaneously. Each burst will be buffered at the source during an offset interval and need not be buffered at intermediate nodes, if no blocking is encountered by the control packet. If a control packet is blocked, DR and BBM can be used to increase the effectiveness through buffer allocation and management. See optical burst switching. Just-In-Time JIT. A term taken from the inventory and distribution field to describe computer processing systems that handle data translation or other tasks at runtime. For example, Just-in-Time compilers compile code on-the-fly instead of running a code interpeter (e.g., SmallTalk) in situations where this approach may be faster. See Java Virtual Machine. justify v. 1. A typesetting term for describing the process of evening out the bounds of a vertical column (usually of text paragraphs, as in newspaper columns). Typically, text is left-justified (aligned on the left), which research indicates is the most readable

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form, or double-justified (aligned both left and right), which works best with proportional fonts and highresolution printers. Specialized applications (accounting columns, advertising copy, page numbers) are sometimes right-justified. 2. To give a convincing argument to the boss to buy you a cool new handheld telecommunications gadget for work or to send you to an interesting technology-related conference like SIGGRAPH. JvNCnet John von Neumann Center network. A midlevel, northeastern U.S. regional network owned and operated by Global Enterprise Services, Inc. JvNCnet was the first T-1 research network and supported the networking needs of the U.S. National Science Foundation (NSF).

In 1989, the National Science Foundation announced a 3-year award to JvNC to establish Phase II, with input from academic and industrial institutions and representatives from the National Science Foundation and others. Phase II connected a number of prominent networks and organizations to JvNCnet, including Bell Laboratories, Rutgers University, Princeton University, Siemens Research, and JANET. GES provides users with the hardware and telephone line necessary to connect to JvNCnet access points with a variety of transmission speed options. JWICS See Joint Worldwide Intelligence Communications System. JXML See Java XML.

K k abbrev. kilo-. See kilo-. K 1. abbrev. Kelvin. 2. Symbol for 1024 (commonly used with quantities of data elements such as bits). Thus, 210 or 2K = 2048 bits. Also a prefix as in Kbps (kilobits/sec). 3. symb. 1000 when used to indicate monetary quantities. For example, $50K typically indicates a salary of $50,000/year. K language A programming language distributed by Kx Systems. Like Sun’s Java, it is an interpreted, portable language and the two can be used in conjunction with one another. K was specifically designed for financial programming, optimized for the efficient handling of very large amounts of complex data. Thus, it has a small code footprint for these applications and is appropriate for large relational databases and data analysis. When Java is used with K to provide graphical user interfaces and Web functionality and portability, it is possible to develop powerful e-commerce applications for the Internet. K plan, K-plan See keysheet. K Series Recommendations A series of ITU-T recommendations providing guidelines for preventing interference in telecommunications systems (there are also interference-related topics in various other Series Recommendation documents). These guidelines are available as publications from the ITU-T for purchase. Since ITU-T specifications and recommendations are widely followed by vendors in the telecommunications industry, those wanting to maximize interoperability with other systems need to be aware of the information disseminated by the ITUT. A full list of general categories is listed in the Appendix and specific series topics are listed under individual entries in this dictionary, e.g., J Series Recommendations. See K Series Recommendations chart. K-band A designated portion of the electromagnetic spectrum ranging from 10.9 to 36 GHz. The K-band range is commonly used for small antenna satellite transmissions. See band allocations, Ka-band, Kuband. K-carrier A four-wire broadband cable carrier system utilizing frequencies to about 60 kHz.

K-style handset The designation for the shape of newer telephone handsets which resemble older desk phone G style handsets, except that they have a more squared-off design on the ear- and mouthpieces. They are heavier and more substantial than some of the newer cordless or cell phone handsets, which tend to be flat and small. See G style handset. K56flex modem A 56k data telecommunications modem technology developed by Rockwell Semiconductor Systems and Lucent Technologies to enable higher data throughput rates over standard analog telephone lines (POTS). The modem was competitive with U.S. Robotics’ x2 technologies in the absence of an established 56k standard. Higher data rates were achievable by looking at the structure of the phone lines and the prevalent patterns of modem usage. These modems were designed to do less conversion as analog phone lines were actually part of a predominantly digital system. In addition, the K56flex modems were optimized for downstream transmissions, with upstream being delivered at speeds up to 33.6 Kbps. K56flex modems are backwardly compatible with the ITU V.34 standard to enable fallback when the server doesn’t support K56flex. When the V.90 standard was approved by the International Telecommunication Union (ITU), Rockwell and Lucent announced that new modems would also be compatible with the ITU V.90 standard (formerly called V.Fast). Some K56flex modems could be upgraded to support V.90. See V.Fast, V Series Recommendations. kA abbrev. kiloampere, 1000 amperes. Ka-band The designated portion of the electromagnetic spectrum in the high microwave/millimeter range, approximately 18 to 22 GHz. The Ka-band is used primarily by small antenna satellite transmissions, and is intended to support future applications, for example, mobile voice. A 500-MHz allocation within this spectrum is earmarked for nongeostationary fixed satellite orbit services, and there are spectrums for local multipoint distribution services (LMDS), mobile satellite services, and geostationary satellite services. See band allocations for chart.

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K Series Recommendations Recom.

Description

Recom.

K.1

Connection to earth of an audiofrequency telephone line in cable

K.17

K.2

Protection of repeater powerfeeding systems against interference from neighbouring electricity lines

Tests on power-fed repeaters using solid-state devices in order to check the arrangements for protection from external interference

K.18

Calculation of voltage induced into telecommunication lines from radio station broadcasts and methods of reducing interference

K.19

Joint use of trenches and tunnels for telecommunication and power cables

K.20

Resistibility of telecommunication equipment installed in a telecommunications center to overvoltages and overcurrents

K.21

Resistibility of telecommunication equipment installed in customer's premises to overvoltages and overcurrents

K.22

Overvoltage resistibility of equipment connected to an ISDN T/S bus

K.23

Types of induced noise and description of noise voltage parameters for ISDN basic user networks

K.24

Method for measuring radiofrequency induced noise on telecommunications pairs

K.25

Protection of optical fibre cables

K.26

Protection of telecommunication lines against harmful effects from electric power and electrified railway lines

K.3

Interference caused by audiofrequency signals injected into a power distribution network

K.4

Disturbance to signaling

K.5

Joint use of poles for electricity distribution and for telecommunications

K.6

Precautions at crossings

K.7

Protection against acoustic shock

K.8

Separation in the soil between telecommunication cables and earthing system of power facilities

K.9

Protection of telecommunication staff and plant against a large earth potential due to a neighbouring electric traction line

K.10

Low frequency interference due to unbalance about earth of telecommunication equipment

K.11

Principles of protection against overvoltages and overcurrents

K.12

Characteristics of gas discharge tubes for the protection of telecommunications installations

Description

K.13

Induced voltages in cables with plastic-insulated conductors

K.14

Provision of a metallic screen in plastic-sheathed cables

K.27

K.15

Protection of remote-feeding systems and line repeaters against lightning and interference from neighbouring electricity lines

Bonding configurations and earthing inside a telecommunication building

K.28

Simplified calculation method for estimating the effect of magnetic induction from power lines on remote-fed repeaters in coaxial pair telecommunication systems

Characteristics of semi-conductor arrester assemblies for the protection of telecommunications installations

K.29

Coordinated protection schemes for telecommunication cables below ground

K.16

Recom.

Description

Recom.

Description

K.30

Positive temperature coefficient (PTc) thermistors

K.43

Immunity requirements for telecommunication equipment

K.31

Bonding configurations and earthing of telecommunication installations inside a subscriber’s building

K.44

Resistibility of telecommunication equipment to overvoltages and overcurrents

K.45

K.32

Immunity requirements and test methods for electrostatic discharge to telecommunication equipment – generic EMC recommendation

Resistibility of access network equipment to overvoltages and overcurrents

K.46

Protection of telecommunication lines using metallic symmetric conductors against lightninginduced surges

K.47

Protection of telecommunication lines using metallic conductors against direct lightning discharges

K.33

Limits for people safety related to coupling into telecommunication system from AC electric power and AC electrified railway installations in fault conditions

K.34

Classification of electromagnetic environmental conditions for telecommunication equipment – basic EMC recommendation

K.48

EMC requirements for each telecommunication network equipment – product family recommendation

K.35

Bonding configurations and earthing at remote electronic sites

K.49

K.36

Selection of protective devices

K.37

Low and high frequency EMC mitigation techniques for telecommunication installations and systems - basic EMC Recommendation

Test condition and performance criteria for voice terminal subject to disturbance from digital mobile phone

K.50

Safe limits of operating voltages and currents for telecommunication systems powered over the network

K.38

Radiated emission test procedure for physically large systems

K.51

Safety criteria for telecommunication equipment

K.39

Risk assessment of damages to telecommunication sites due to lightning discharges

K.52

Guidance on complying with limits for human exposure to electromagnetic fields

K.40

Protection against LEMP in telecommunication centers

K.53

K.41

Resistibility of internal interfaces of telecommunication centers to surge overvoltages

Values of induced voltages on telecommunication installations to establish telecommunications, AC power, and railway operators responsibilities

K.42

Preparation of emission and immunity requirements for telecommunication equipment – general principles

K.54

Conducted immunity test method and level at fundamental power frequencies

K

KAQ9 Gopher server A Web-accessible Gopher server developed by Chris McNeil, with enhancements by McNeil and Peter Crawshaw. The Web version supports email, FTP, Gopher, NTP, Finger, and SLIP servers plus security through IP filtering. The name is based on the underpinnings of Phil Karn’s KA9Q NET/NOS. KA9Q NOS TCP/IP Phil Karn’s popular commercial TCP/IP software implementation for packet radio communications. The name of the software comes from his amateur radio callsign. It is available in Borland C++ and a 32-bit protected-mode version for DJGPP. It is popular for its compatibility with lower memory and CPU systems (not everyone wants to throw away perfectly good older computing systems). Amateur radio enthusiasts publish a number of amateur radio TCP/IP server gateways on the Web, which connect initially through telnet. Some of these are password-protected, and some can be accessed by anonymous login, somewhat similar to anonymous login sessions on FTP sites. KADS See Knowledge Analysis and Design System. Kahle, Brewster Project leader for the Wide Area Information Server (WAIS) at Thinking Machines Corporation in Massachusetts (1989), and involved with the company since its founding in 1983. WAIS, Inc. was sold to AOL in 1995. Kahle designed the CPU of the Connection Machine Model 2 in the 1980s. He founded the Internet Archive and cofounded the Alexa Web information company in April 1996, and is active in promoting scholarly repositories of Internet history and documents that might otherwise have a short shelf life. See Wide Area Information Server. Kahn, Bob In 1974, Bob Kahn coauthored A Protocol for Packet Network Internetworking, which describes Transmission Control Protocol (TCP). In 1977, Kahn co-demonstrated a gateway system that could interconnect packet radio with the ARPANET. See Cerf, Vince; packet radio. Kaleida Labs, Inc. A California multimedia development company established as a joint venture between IBM and Apple Corporation (including Taligent). Best known, although not well known, for its ScriptX cross-platform hypermedia product. The venture was discontinued in 1995 and the resources rolled into the founding companies. Kangaroo Network A commercial hardware/software product from Spartacus/Fibronics designed to enable IBM mainframes to intercommunicate with other networks using TCP/IP. Kangaroo Working Group A working group on telecommunications and the information society that works with the European Internet Foundation looking into issues associated with creating a level playing field in terms of Internet use and access in Europe, ensuring a balance between private industry and government. The Kangaroo Group has been actively involved in conferences since the mid-1980s and has actively debated Internet regulations and barriers to the use of cyberspace.

kanji A symbolic, ideographic language system used to represent Chinese characters used in Japanese. It’s a challenge to represent the many thousands of Asian characters on computers designed to be programmed and operated in the English language. The Japanese have a number of other ideographic and character symbols in addition to kanji. Kapor, Mitchell (Mitch) (1950- ) The instigator of several historic high profile computer-related organizations, Mitch Kapor founded Lotus Development Corporation in 1982, and was the designer of the well-known Lotus 1-2-3 spreadsheet software. In 1990, he cofounded the Electronic Frontier Foundation (EFF), a nonprofit civil liberties organization. Kapor has chaired the Massachusetts Commission on Computer Technology and Law and served on the board of the Computer Science and Technology arm of the National Research Council, and the National Information Infrastructure Advisory Council. Karnaugh map A two-dimensional truth lookup table organized to facilitate combination and reduction of Boolean expressions. See Boolean expression. Karn’s algorithm A mathematical formula used for improving network round-trip time estimations. In layered network architectures, application of the algorithm helps the transport layer protocols distinguish among round-trip time samples. It is used in Transmission Control Protocol (TCP) implementations to separate various types of return transmissions and to establish whether or not to ignore retransmitted signals. It is also applied to backoff timers in Point-to-Point (PPP) tunneling networks. See ATM, Point-to-Point Tunneling Protocol. Kay, Alan A precocious child and avid reader, Kay was inspired by the work of Seymour Papert at MIT in the 1960s. Kay was committed to the idea that computers should be easy, fun, and accessible, and began developing what was to become the Smalltalk object-oriented programming language. He became a group leader at Xerox PARC in the early 1970s, a period when tremendous innovation in microcomputer technology and user interfaces was stimulated at the lab. Kbps kilobits per second; 1000 bits per second. It is sometimes written Kbits/s. KBps kilobytes per second, 1000 bytes per second. It is sometimes written Kbytes/s KBS See knowledge base system. KDC See key distribution center. KDD 1. Knowledge Discovery in Databases. A branch of artificial intelligence applied to database query, search, and retrieval. 2. Kokusai Denshin Denwa Company, Ltd. A Japanese supplier of international telecom services, equipment, and facilities. KDDI Corp. Japan’s second-largest communications carrier, descended from Kokusai Denshin Denwa Kabushiki Kaisha (KDD), which was founded in 1953. In April 2001, KDDI announced Java support for its mobile phone services through its CLDC- and MIDP-conforming application interface called KDDI-P.

KDD R&D Laboratories, Inc. is the research and development division. It was founded when KDD was detached from the Nippon Telegraph and Telephone Public Corporation and moved into a new research facility for conducting research in international communications in 1960. It became independent of KDD in 1998 and was remerged, along with other firms, in 2000 to become KDDI’s R&D division. The R&D lab has developed TDMA technology for satellite communications, submarine fiber optic cables, G3 facsimile coding technologies, magneto-optical discs, and data compression and transmission technologies. KDD Fiber Labs, Inc., a KDDI Group Corporation, develops fiber optics technologies, including WDM optical amplification and various types of light sources. KDKA KDKA originated as amateur call sign 8XK, operating from the garage of Frank Conrad. It is a historically significant Westinghouse Electric radio broadcasting station in Pittsburgh, Pennsylvania that used radio waves to report returns of the HardingCox Presidential race to the American public, on November 2, 1920. This was about 14 years after the earliest experimental broadcasts and a week after receiving its own official broadcasting license. By the following year, KDKA was making regular public broadcasts and radio broadcasting was booming, with more than 500 broadcasting stations sprouting up around the country. KDKA was still broadcasting under the same call sign more than 80 years later. See CFCF; Herrold, Doc; radio history. KEA See Key Exchange Algorithm. Kearney System KS. A parts numbering scheme developed for Western Electric telecommunications equipment, named after the town in New Jersey where the plant was located. The KS system has generally been superseded with vendor-specific and industry standard codes, although Kearney numbers are still found on some pieces of equipment. keepalive interval The period of time between keepalive messages. The amount of time depends upon the type of network and the type of activity taking place. For example, for a computer process, the interval might be measured in nanoseconds, whereas for a user activity, it might be measured in minutes. See keepalive message, keepalive signal. keepalive message Messaging between network devices that indicates that a virtual circuit between the two is still active (alive). See keepalive interval, keepalive signal. keepalive signal A network signal transmitted during times of idleness to keep the circuit from initiating a time-out sequence and terminating the connection due to lack of activity. See keepalive interval, keepalive message. Kelvin balance, ampere balance A historical instrument for measuring the absolute value of an electrical current, named after its inventor, William Thompson (Lord Kelvin). It is essentially a galvanometer that measures the force produced by the magnetic field associated with the passage of current through a conductive medium.

In one of its historical fabrications, the instrument resembled a small reel-to-reel tape recorder, with two low, flat spools coiled with wires connected to one another in series positioned a few inches apart. A pivoting beam balance enabled a set of rings to move freely between the coils. A finely incremented rulerlike gauge stretched the length of the instrument, in front of the coils, from the outer edge of one to the other. The whole thing was generally encased within a protective brass and glass enclosure. The instrument was sold with a set of weights. The current to be measured passed through the wire coils to create an attractive force referenced against a known weight. Two ampere balances were designated as legal standard instruments in 1894. Kelvin effect When an electric current passes through a single homogeneous but unequally heated conductor, heat is absorbed or released. This effect is named after William Thompson (Lord Kelvin). Kelvin scale A temperature scale proposed by William Thompson (Lord Kelvin), based on the efficiency of a reversible machine. Zero is designated as the temperature of the sink of the machine working efficiently, that is, complete conversion of heat into work, a situation possible only at absolute zero on a gas temperature scale. Zero degrees Kelvin can be expressed as -273.15 degrees Celsius (C) or -459.67 degrees Fahrenheit (F).

William Thompson, more familiar as Lord Kelvin, studied electromagnetism. The Kelvin temperature scale, Kelvin receiver, and Kelvin effect are named after him.

Kelvin, Lord William Thomson (1824-1907). A Scottish physicist and mathematician who made significant contributions to the field of thermodynamics, and applied his theories to the dynamics and age of the earth and the universe. He utilized the field concept to explain electromagnetism and its propagation. The concept of an all-pervasive “ether” was still prevalent at the time, so he explained a number of his observations within this context. He also developed the siphon recorder, a number of types of voltmeters, and an ampere balance, and was involved

K

in laying the transatlantic telegraph cable. The Kelvin scale and Kelvin effect are named after him. Kenbak-1 A discrete logic microcomputer designed by John V. Blankenbaker, introduced in 1971 as the Kenbak-1 Digital Computer. It featured 256 bytes of memory, three programming registers, and five addressing modes. The controlling switches were on the front panel of the machine. It was advertised in the September 1971 issue of Scientific American, 3 years prior to the introduction of the Altair, for only $750. One of the earliest microcomputers, the Kenbak-1 was apparently ahead of its time. Unfortunately, only 40 machines sold over the next 2 years, and the California-based Kenbak Corporation missed a significant business window by a narrow margin. One year after the company closed, the Altair computer kit caught the attention of hobbyist readers of Popular Electronics magazine and sold over 10,000 units. The Kenbak-1 was not the only commercially unsuccessful computer that preceded the Altair; the Simon was a remarkable forerunner, described in 1949 by Edmund Berkeley, and the Sphere and Micral computers were early entrants to the industry following the Kenbak-1. They also failed to sell in significant numbers. See Altair, Arkay CT-650, Heathkit EC-1, Intel MCS-4, Micral, Simon, Sphere System.

The Kenbak-1 computer was promoted as an educational and hobbyist computer in 1971, 3 years before the introduction of the Altair. Given its design and price range, it’s reasonable to speculate that it had the potential to sell as well as the Altair, which was available assembled or as a kit. Perhaps, in 1971, consumers weren’t yet ready for the idea of a computer so small it could fit on a desktop.

Kendall effect Distortion in a facsimile record, caused by faulty modulation of the sideband to carrier ratio of the signal. Kennelly, Arther E. (1861-1939) A British-born American mathematician and engineer who studied mathematical aspects of electrical circuitry. He also studied the properties of the Earth’s atmosphere and its effects on radio waves and suggested that an ionized layer above the Earth could reflect radio waves, an idea soon after independently published by Oliver Heaviside. Kennelly-Heaviside layer In 1902, A. Kennelly and O. Heaviside proposed, independently of one another, that an ionized layer surrounding the Earth could serve as a reflecting medium that would hold radiation within it. This led to the discovery of a number

of regions surrounding Earth and utilization of the characteristics of some of these layers in long-distance wave transmission. It also led, in the 1920s, to confirming experiments in which radio signals were bounced off this reflecting layer. See Heaviside, Oliver; ionosphere; Kennelly, Arther. Kerberos Name for the three-headed dog of Greek mythology who guarded the gates of Hades. Kerberos authentication An authentication system developed through the MIT Project Athena effort. Kerberos is a client/server security mechanism based upon symmetric key cryptography. Each user of the Kerberos system is assigned a nonsecret unique ID and selects a secret password. The secret password is provided to the Kerberos system and is not intended to be divulged by either party. The user then uses the password to request access from the system. The identity of the user is verified by generating a random number and presenting a problem that can likely be solved only by the authentic user, thus providing access to a message on the system. The symmetric nature of the system is in the use of the same encryption and decryption key. For security purposes, long, randomly selected strings work best with this system of cryptography; otherwise it may be vulnerable to password-guessing attacks. Kermit Project A nonprofit, self-supporting project at Columbia University for the support of the Kermit Protocol and the development of Kermit-related technologies. The project also includes information on documentation, licensing, and technical support for users of the Columbia implementation of Kermit. See Kermit Protocol. http://www.columbia.edu/kermit/ Kermit Protocol A packet-oriented, platform-independent file transfer protocol developed at Columbia University in 1981. Hundreds of Kermit implementations support the 7-bit and 8-bit transfer of text and binary files. They are commonly used over asynchronous, serially connected local area networks (LANs) and phone lines. Kermit is flexible and configurable. Kermit is not the speediest protocol, as each packet is checked and acknowledged as it is transferred, but it is reliable, widespread, and well-supported, especially in academic institutions; when all other protocols fail, it’s often the one which will get the file transfer done. There are numerous terminal emulators based on Kermit, with VT52 and VT100 versions being common. Telnet, an important protocol for remotely connecting to a network host, has also been implemented with Kermit. Kermit is a workhorse, but its use in its original form has declined. Most local area networks and the Internet now use other network connection and file transfer mechanisms such as ATM, Ethernet, and FTP, but traditional Kermit is still useful for phone links and small networks interconnected with basic serial connections. Updated versions of Kermit are significant, however, and may greatly extend its useful life. Internet Kermit Service is a file transfer service described by da

Cruz and Altman at Columbia University based on a combination of the widely used Telnet Protocol and Kermit Protocol. It supports both anonymous and authenticated access. Kermit over Telnet enables the traversal of firewalls and a number of security options. By providing some advantages over File Transfer Protocol (FTP), this Kermit configuration is a practical option for distributed networks, including the Internet. The registered IANA port for Kermit connections is 1649. Kermit is an open protocol, so it is freely distributable and can be used as the basis for software applications development, but Columbia’s implementation of the Kermit protocol is copyrighted. See FTP, Kermit Project, XModem, YModem, ZModem. See RFC 2839, RFC 2840. kernel 1. Line within a conductor along which the current-resulting magnetic intensity is zero. 2. Low level of an operating system at which processes and resources (such as memory and drivers) are created, allocated, and managed. Functions and operations at the kernel level form a bridge between hardware and software resources and are mostly or completely transparent to the user. kerning In typography, a term to describe the spacing between individual letters. Kerning is applied to tighten or loosen the look and feel of a line of type, or to visually correct letter combinations that appear perceptually or aesthetically to have too much white space between them. For example, if you put the letters T v together, they may seem too far apart because of the overhanging top of the T and the angle of the v. With kerning you can tuck the v under the top bar of the T and it looks better (Tv). Negative letter spacing applied to the entire line of text is called white space reduction.

T v Tv The letter pair on the left is unkerned and there is an unaesthetic gap between the T and the v. The pair on the right has been negatively kerned to tuck the v under the top bar of the T to create a stronger relationship between the two shapes.

Kerr cell A device used to modulate light in conjunction with polarizers. The cell contains electrodes to direct the necessary electric field for inducing the Kerr electro-optical effect and the material being influenced by the combination of the field and a beam of polarized light. Photodetectors may be used in conjunction with the Kerr cell to determine if or when the effect occurs. Kerr cells have been used in the fabrication of high-speed optical shutters. Kerr electro-optical effect A phenomenon discovered by John Kerr in 1875. It is an electro-optical effect in which certain substances become double refracting (birefringent) in the presence of strong

electric fields or in which certain specific substances become double refracting in smaller electric fields. In other words, a single incident ray of light is refracted as two, with the two rays oscillating in mutually perpendicular planes. Isotropic liquids or gas, for example, show the Kerr effect and become optically anisotropic when subjected to a consistent electric field perpendicular to a beam of light. To account for the effect, it is theorized that the application of the electro-optical energy causes a reorientation of a material’s molecular structure. Since the effect is not universal across materials and levels of electromagnetic influence, it is often studied with certain parameters held within controlled limits, such as the constancy of the electric field and the wavelengths of light. Since the Kerr effect can be induced through controlled conditions and occurs quickly, various researchers have suggested that it may have practical applications in troubleshooting optical transmissions or in increasing bandwidth in optical communications systems. See Kerr cell, Pockels effect. Kerr magneto-optical effect The change in a light beam from plane polarized to elliptically polarized when it is reflected from the reflective surface of an electromagnet. The degree of rotation is directly proportional to the degree of magnetization of the reflective material. The transmissive aspects of this effect were first observed and described by Michael Faraday in the 1840s and researched further by John Kerr three decades later as to its reflective properties. Because of their relationship, the Faraday and Kerr effects are often described together. This magneto-optical effect is useful for studying magnetic effects in superlattices and giant magnetoresistive (GMR) effects. GMR technology was discovered in the late 1980s and has since developed into a new, highly sensitive sensor design for disk drives. The effect can also be put into practical use for measuring current in power lines using a polarized laser to measure the degree of rotation. See Faraday effect, giant magneto-resistance. Kerr, John (1824-1907) A Scottish-born physicist best known for discovering and describing the Kerr electro-optical effect. Kerr carried out research under the direction of William Thompson (Lord Kelvin). See Kerr electro-optical effect. keV Abbreviation for kiloelectronvolt. Kevlar The DuPont tradename for a strong, synthetic multipurpose material that is, ounce-per-ounce, about five times as strong as steel. In the 1960s, a new liquid crystal polymer fiber was invented by Stephanie Kwolek; Kevlar is the commercial embodiment of this fiber. Kwolek also invented Nomex, a fiber used in electrical insulation. Kevlar is used in applications where strong, light, flexible materials are needed, such as bulletproof vests and protective sheathings for sensitive or electrically active materials. Kevlar tape and Kevlar strength members are used in fiber optic cables. A water-resistant sheath is often fitted over the Kevlar or Kevlar-impregnated inner layers for further

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protection from the elements (typically PVC or polyethylene). Kevlar is sometimes mixed with building materials to increase strength and resilience in the event of industrial vibrations or earthquakes. Carbon steel cutters are generally used to cut the Kevlar components in fiber optic cables. key n. 1. A small, physical security device, often made of metal, inserted into a matching lock receptacle to lock/unlock or activate/inactivate an object or structure. The shape of the key is commonly the aspect that allows a lock to be opened or closed, but more recent data-compatible keys may have magnetic stripes rather than indentations to activate a lock. 2. In an image, the overall tone or value of the image, often used to adjust camera settings to balance the amount of light or to screen out certain colors or light intensities (e.g., chroma key). 3. A switch for opening or closing a circuit. 4. In a database, an organizational means to locate desired information without searching the entire content of the database. 5. On keyboards, keypads, phone pads, etc., a small, roughly cubic, raised, movable, input attachment intended to be depressed, usually by a finger, to make a selection. 6. The modern equivalent of the switch on an old phone. key, telegraph The signaling device which allows the input of code, usually Morse code, and transmits it to the communications channel. The key superseded the portfule of earlier systems. See telegraph history. key encryption A personal or public identifier intended to establish the owner or recipient of a secure encoded message. Key-related negotiations may be symmetric or asymmetric and may be based upon public keys, private keys, or a combination of both. Key encryption may be based upon a long-term escrow system or upon short-term session-based communications. A public key cryptographic scheme consists of a public key provided openly to anyone who wishes to send an encrypted message, and a private key used by the recipient to de-encrypt the received message. Here is a summary of some of the concepts associated with key encryption: key agreement An encryption key establishment mechanism that is common to asymmetric cryptographic exchanges but may also be used in symmetric exchanges. In key agreement, a pair of entities, wishing to engage in a secured communication without prior arrangement, make use of public data (e.g., a public key) to negotiate a common key value unique to their communication (i.e., not known or used by other entities). When a Diffie-Hellman technique is used, key agreement is arranged without the need to transfer the key. See Diffie-Hellman. key center A trusted, centralized distribution point (e.g., separate server machine) capable of administering the use of key-encrypting “master” keys to encrypt and distribute session keys for secured communications.

key confirmation The process of ensuring that participants in a key-secured communication are legitimate by determining whether they do indeed possess a shared symmetric key. key distribution center KDC. In symmetric digital cryptography, a key center that provides encryption/decryption keys to two or more entities that wish to engage in a secured communication through an agreed-upon key distribution protocol. These keys are often session-related. key escrow A security system component in which part or all of a cryptographic key is entrusted to a third party to hold “in escrow.” The key “bank” or authority is responsible for storing and releasing the keys to a party involved in a communication, provided that party submits proper authorization. The authorized recipient can then use the key to decrypt a message. There has been considerable debate over the use of escrow authorities. On the one hand, some individuals feel no one should have any part of a communication other than the sending and receiving parties. On the other hand, some believe it is necessary to have a third party that can be served a warrant to hand over information critical to the maintenance of national security and the carrying out of law enforcement activities. It is also critical, for the system to work, for the authority to be highly reliable, accountable, and secure. See key generation, key recovery. key establishment The processes of key generation, storage, and distribution that together enable a secured key-related communication association to be established. key exchange The transmission or recording of a software key with another party, or swapping among two or more parties. See encryption, PGP, key generation. key generation The process of creating a software key for security uses. Once this has been done, it is expedient to keep track of information related to keys (location, password, etc.) so that key generation does not have to be done again. Portable devices for generating a key are sometimes used in conjunction with keyless security locks on building premises. See key, encryption. key length The number of symbols, usually expressed in bits or bytes, used in representing an encryption key. In general, the longer the key length, the greater the possible number of ways in which the data may be scrambled to ensure that it cannot be easily decrypted by an unauthorized party. key lifetime/lifespan The time span or expiry date associated with an established cryptographic key. The expiry period or lifespan may be determined in advance by an issuing authority, especially in session-related key assignments, or may be dynamically determined. The key lifetime is also determined in part by users. If a user loses or forgets or misplaces a key, its effective lifetime has

ended even if the capability to use it still exists. Some key cryptography systems will explicitly include a parameter that determines the lifespan of a key (e.g., until the session is terminated). The capability to terminate a key is important in situations where key assignments must be reused in a dynamic resource-conscious system (e.g., session-related keys) or where the key users may cease to have authority (e.g., terminated employees). key management protocol A protocol developed to facilitate establishment of a key-administered transmission between entities wishing to secure the communication through key encryption. key recovery The process of determining the value of a cryptographic key that has been used to perform an encryption operation. Key recovery is a hotly debated political topic since law enforcement agencies have desired and at times secured the legal and technological capability to recover keys for decrypting secured communications. A key “escrow” system that included portions of keys (to facilitate key recovery) was at one time intended to be associated with software products exported out of the U.S. Key recovery by governmental agencies was repeatedly proposed and defeated during the 1990s. Key encapsulation is a means of storing information about a cryptographic key by encrypting it with another key so that only authorized recovery agents may decrypt and retrieve the stored key. See key escrow. key space The universe or space from which cryptographic key values may be taken. It is the total number of distinct transformations which may be supported by a cryptographic scheme, in other words, the realm of possible variations possible. key update The updating or derivation of a new key from an existing key. Also called rekey. See certification, Clipper Chip, cryptography, encryption, Pretty Good Privacy. Key Exchange/Encryption Algorithm KEA. An asymmetric key encryption algorithm similar to the Diffie-Hellman algorithm, that utilizes 1024-bit keys. KEA was originally developed by the National Security Agency (NSA) as a classified security mechanism whose status was changed in June 1998. See Clipper Chip, Diffie-Hellman, key encryption, SKIPJACK. Key Contact A service of British Telecom that comprises an 11th phone number (nonmobile) in addition to the key numbers kept by a business subscriber in BT’s Friends & Family Key Numbers service. See key numbers. key illumination The lighting of a key on a keypad or keyboard to signal its status or facilitate its location. The keys may be illuminated to indicate that they are active (or pending), as in a multiline phone system, or to enable them to be seen in low-light conditions (e.g., a burglar alarm keypad). Steady illumination or various flashing speeds and patterns may be used to indicate the line or device status.

key map A table that translates keyboard input values from one configuration to another, commonly used in computer software to accommodate the alphabets of a number of languages. This is useful for translation, alternate typing keyboard setups (e.g., Dvorak), graphics, and music applications. key numbers Telecommunications number ‘addresses’ of particular interest, such as the phone numbers of frequently-called family and close friends or business associates. British Telecom (BT) has a key numbers service that can be managed on the Web. The Web portal enables customers to set up and manage the Friends & Family Key Numbers list associated with their phone accounts. This service is without charge for residential and business customers for up to ten numbers and may include up to two mobile numbers. It is likely that this type of Web access to telecommunications services will increase, just as online banking is increasing, due to its 24-hour availability and update convenience; the user doesn’t have to wait to call service representatives during business hours. key performance indicator KPI. A statistic intended to indicate effectiveness in specified key aspects which are typically industry-specific. In the telecommunications industry KPIs may comprise the frequency or duration of calls, revenue per call, purchase trends, etc. KPIs are used to plan budgets, inventory, and investment, financing, and growth strategies. Key Performance Indicator KPI. A commercial database to track mobile operators’ key performance indicators such as minutes of use, churn, average revenue per user, and acquisition costs. The system was first released by EMC, a U.K. firm, in April 2000, and is incorporated into EMC World Cellular Information Services. The system computes average statistics for each KPI for regions and reporting periods. key pulsing KP. A system for sending multifrequency signals from a pushbutton key telephone through a phone circuit to establish a connection. It is sometimes called key sending. In older, manually operated toll stations, pulsing was sometimes used by operators instead of dialing. Dial-operated pulse phones are on the decline, with touchtone phones replacing them. key service unit, key system unit KSU. The internal electronics and logic that enable the selection of lines and other options in a key telephone system. This may be a small cabinet installed in a closet or some other area where the lines are not cluttering up the environment or causing an obstruction. See key telephone system. key station Master station from which broadcasts originate. key telephone system, key system KTS. A multiline telephone system in which individual phones have multiple keys or buttons that the user presses to select the line over which she or he wishes to communicate. In larger multiline key systems, there may

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be a main console through which the calls are channeled. This is not the same as a private branch system, in which a separate switching system is associated with the phones. In the key system, which is used in many small offices, the switching and selection of lines is done manually by the user. Some larger offices with private branch exchanges will use a hybrid system which also incorporates one or more key systems, sometimes in individual departments. New key systems commonly feature programmable function keys and LED status displays. See key service unit, private branch exchange. keyboard Hardware peripheral for detecting and transmitting user input to a computer system through individually labeled keys. Descended from typewriter keyboards and typically arranged according to the historic “QWERTY” layout which, ironically, was designed to slow down typing in order to prevent key jamming on old manual typewriters. This is unfortunate, because other layouts, such as Dvorak, may be easier to learn and result in faster typing. A variety of keyboards are available for each type of computer system, some with better ergonomics than those which typically come with the system. See keypad; keyboard, touch-sensitive. keyboard buffer Recent input is typically stored in temporary memory in order to prevent loss or corruption in the event that the system was not yet ready to respond at the time that the keys were pressed. keyboard overlay 1. A printed “skin” or cover, usually of soft molded plastic, which fits over the keyboard and provides additional key designations or modifies existing ones for software programs which require special symbols or keyboard reconfiguration. Useful for custom applications, although they tend to reduce the speed and comfort of typing. 2. A cover to prevent particles and spills from getting under keys and interfering with their operation. keyboard, touch-sensitive A hardware peripheral for detecting and transmitting user input to a computer system through a flat, touch-sensitive surface. The back side is generally a conductive medium which completes a circuit with very minimal pressure (the touch of a finger). Ideal for general public applications (e.g., kiosks) with simple input demands, where there is a need to prevent clogging with debris, mechanical wear, vandalism, or theft of keys. See keyboard. keyboarding Striking keys on a computer or other digital keyboard. This is distinct from typing in that typing is generally intended to immediately translate the keystroke into an image on a printing surface. Keyboarding, on the other hand, enables the keystroke to be stored and manipulated for a variety of purposes, including word processing, chatting, signaling, or printing at a later time. It is possible to “type” on a computer keyboard with a software program designed to immediately send the key to a printing device, but this is rarely used due to the greater convenience of editing the keyboard strokes before printing (or sending them electronically without printing).

keying A means of modulating a signal. This can be done in a number of ways, by varying the amplitude, frequency, or phase of a signal. See amplitude shift keying, frequency shift keying, Gaussian minimum shift keying, quadrature phase shift keying, phase shift keying. keypad A key-based interface device for various calculators, dedicated word processors, security systems, and computing devices. The keypad is usually a small compact group of functionally related keys, often consisting of numbers, designed in rows and columns to facilitate finger access. A larger grouping, as is found on computers or typewriters, is usually called a keyboard. On a calculator, the keypad is generally configured as three or four columns by five or six rows, depending upon how many extra function keys (memory, clear, print, etc.) are integrated into the key pad layout. Many security entry devices and alarm systems are managed through a keypad with nine or twelve keys for entering numeric codes or alphanumeric passwords. The system may be wired or wireless and may trigger other mechanisms (e.g., a security camera) if used or if suspicious codes are entered. See keyboard, numeric keypad. keysheet An administrative plan for phone extensions that tracks and illustrates the connections and features assigned to that phone. Keysheets are practical in institutional environments with many extensions, particularly if the extension phones have different capabilities and dialing privileges. A keysheet is even more important for keeping track if the phones are also individually programmable or if they are relocated on a regular basis. Software exists for developing keysheet connection plans, diagrams, and overlays. Electronic forms are now also commonly used for individual members of departments to list the phones, faxes, and modems for inclusion in a keysheet database. keystoning A visual aberration which occurs when an image is projected on a surface off-plane, that is, on a surface which is at an angle to the plane of the surface of the projecting lens. Thus, if a rectangular image from a film or slide projector, for example, were projected on a movable screen which was crooked, the image would be wide on one side and narrow on the other. See barrel distortion. keystroke Input to a keyboard consisting of a single, or combined key (e.g., Ctrl-C) press. Typing speeds are generally measured in words per minute, but some data entry tasks are measured in keystrokes per minute. kHz abbrev. kilohertz, 1000 hertz. See hertz. kiddie cam A video camera installed to monitor the activities of children. These are common in household nurseries and increasingly common in daycare facilities. Some of these cams have been interfaced with the Internet to enable parents and caregivers to remotely monitor the activities of children. For the safety and privacy of children being monitored by Web-based kiddie cams, some kiddie cam services require a password to login to the remote viewing site.

Unfortunately, the kiddie cam moniker is also used by some sites to promote pornographic images of girls and boys who have been covertly photographed or who are too young to understand how their image is being used. This type of exploitation is generally illegal, but the sites promoting child pornography manage to stay online long enough for the images to be downloaded and shared among thousands or millions of Internet users. KIF See Knowledge Interchange Format. Kilby, Jack St. Clair (1923- ) An American inventor and Texas Instruments Incorporated (TI) employee who contributed to designing the first integrated circuit chip, shortly after joining TI. The development catapulted the miniaturization and speed of electronics into a new level of evolution. Kilby’s first IC was introduced in September 1958, shortly before Fairchild engineers developed historic ICs that were, for some time, considered to be the first (the patent was awarded to Noyce even as Kilby’s application was still being assessed). Texas Instruments has named the Kilby Center, a silicon manufacturing research facility, in his honor. Kilby is also responsible for providing miniaturized electronics that supported the portable calculator market and off-Earth electronic devices that needed to be small and sparing on power consumption. In October 2000, Kilby’s contributions were acknowledged with a Nobel Prize in physics jointly with two other scientists. See integrated circuit; Noyce, Robert; transistor. Kildall, Gary (1942-1994) American educator and pioneer software developer. Kildall developed CP/M (Control Program/Monitor) over a number of years, beginning in 1973, with contributions from his students, when he was a professor of computer science at a California naval school. Kildall developed CP/ M into a very popular, widely used, text-oriented, 8bit operating system in the late 1970s. Kildall later founded InterGalactic Digital Research, which became Digital Research (DR), to market his software products. Digital Research developed GEM, an early graphical user operating system which predated functional versions of Windows. DR also created DR-DOS, which was competitive with MS-DOS, and claimed by many to be of superior quality. Kildall is also known for developing PL/M prior to CP/M, the first programming language for the historic Intel 4004 chip, and for co-authoring a floppy controller interface in 1973 with John Torode. In the ensuing years, Gary Kildall lost one political battle after another with the rapidly expanding Microsoft, and Digital Research never flourished as one might expect for a company so often in the forefront of technology. Digital Research had a history of creating good products, but was overshadowed by its larger, more aggressive competitor. At one point DR won a lawsuit against Microsoft, but it may have been a case of too little too; at that point Microsoft had so much momentum, it was unlikely Kildall and DR could regain their market share. Kildall is acknowledged as the original developer of many significant technologies for the microcomputer indus-

try, but unfortunate circumstances surrounding a fall cut short his life when he was 52. See CP/M; Gates, William. kill 1. Remove or delete, as a word, line, or file. 2. Abruptly or prematurely terminate a process or broadcast. kill file 1. An email or newsgroup filter that sends messages from particular people, or on particular topics, to the “bit bucket,” that is, they are shuffled off to a file that never gets read, or is deleted unread. 2. A list of users banned or otherwise controlled from access to remote terminals or online chat services. See kill command. kill command A software control command available to operators on various chat systems to disconnect a disruptive member from the site. Common reasons for killing a user include racial, cultural, or religious slurs, violation of chat rules, illegal activities, or excessive profanity. On Internet Relay Chat (IRC) there is a general set of guidelines and a code of etiquette to guide channel operators in the appropriate use of the IRC /kill command. kill message 1. A textual message transmitted by an operator to a user in a computer-based “chat room” who is in the process of being removed from the chat area. This is an option on most systems for operators to inform the user as to why he or she is being removed. See kill command. 2. A software command sent to stop a process. This may be on a single-user system, a network, or a specialized system such as a transaction system based on digital data cards. A kill message can halt a process that has hung or gotten out of control, without taking down the operating system; it can stop suspect activities (e.g., possible hacking) on a network with remote terminals, or it can stop the use of a suspected stolen or lost ATM card. 3. An introductory message played over a telephone connection when the user has called a local or long-distance pay-per-call service. It may include consumer protection information or specifics about restrictions or potential call costs. Calls that may exceed charges of a specified amount may be required to include a kill message in the first few seconds of the call to allow the caller to hang up before charges accrue. In spite of mandatory preambles and kill messages, there were complaints to and by the Federal Trade Commission (FTC) in the mid-1990s that telephone service vendors were abusing so-called toll-free 1-800 numbers in a variety of ways, including forwarding 1-800 calls to 1-900 numbers or otherwise manipulating the system to rack up charges on the callers’ phone bills. KILL message 1. A software message that causes a client/server connection to be closed by the related server for a variety of reasons, depending upon the system. For example, in Internet Relay Chat, it may be automatically invoked when duplicate nickname entries are detected; both entries are removed with the expectation that only a single nickname will reappear. This maintains global uniqueness. The KILL message may be available to operators but ideally should be handled by servers. See RFC 1459.

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Kill the Spams KTS. A software product programmed in Visual BASIC Script that filters out unsolicited emails while maintaining some resistance to computer viruses (which are often sent through email). KTS analyzes and scores the information in the headers of email messages and handles them according to a score specified by the user. Thus, it works on algorithmic methods rather than being based upon a brute force list of emailers. kilo- (abbrev. – k or K) Prefix for one thousand (1000), or 103. 10 kilograms = 10,000 grams when used for weights and measures. When used in the context of computer data, more commonly it is capitalized, as in Kbps (kilobits per second), and represents 1024. See k, K. kilocharacter One thousand characters. See kilosegment. kilosegment One thousand segments, with each segment consisting of up to 64 characters. It is used as a billing measure in some systems, such as X.25. kilovolt-ampere kVA. A unit of apparent power. This is a general measure of power consumption for nonresistive devices such as certain types of lighting and computer components. kilowatt kW. An SI unit of power required to do work at the rate of 1000 joules per second. See joule, kilowatt-hour, watt. kilowatt-hour kW-hr. A unit of the energy used to perform work as measured over a 1-hour unit of time. One thousand watt-hours, or 3.6 million joules. This has practical applications as a description of the efficiency of different types of fuel, which can be expressed and compared in terms of kilowatt-hours. kinescope 1. A cathode-ray tube (CRT) in which electrical signals, as from a television receiver, are displayed to a screen. 2. An early term for a motion picture, and probably the inspiration for the term cinemascope. In Britain, the term cinematograph was used to indicate a motion picture or motion picture camera. kinetograph A device patented in 1889 by Thomas Edison for photographing motion picture sequences. See kinetoscope. kinetoscope A device patented in 1893 by Thomas Edison for viewing a sequence of pictures, based on the work of earlier experimenters going back as far as 1883. The loop of film images was illuminated from behind and viewed through a rapidly rotating shutter, thus creating a small motion picture film. See kinetograph. King, Jan The young engineer who coordinated a number of significant amateur radio telecommunications satellite projects, starting with AustralisOSCAR 5 and continuing with the AMSAT satellites. King has written articles and technical reports on some of these activities, many of them for the QST journal. See AMSAT, OSCAR. Kingsbury Commitment An important event on December 13, 1913 in which the U.S. Attorney General, James McReynolds, informed AT&T of violations of the Sherman Antitrust Act of 1890. AT&T voluntarily gave up controlling interest in the Western

Union Telegraph Company, and agreed to stop buying up the independent telephone companies without first obtaining approval from the Interstate Commerce Commission (ICC). AT&T further agreed to provide independent phone companies with access to the long-distance network. The Kingsbury Commitment derives its name from Nathan C. Kingsbury, the AT&T vice president who was appointed by Theodore Vail to correspond with the Attorney General. It is sometimes colloquially called the Kingsbury compromise. See Modified Final Judgment. Kirchhoff, Gustav Robert (1824-1887) A German physicist who conducted pioneer work in spectroscopy and followed up on Ohm’s work by providing further information and a more advanced theory of the flow of electricity through conductors. See Kirchhoff’s laws. Kirchhoff’s laws Laws for the flow of current first described in 1848 by G.R. Kirchhoff: 1. The current flowing to a given point (node) in a circuit is equal to the current flowing away from that point. 2. In any closed path in a circuit, the algebraic sum of the voltage drops equals the algebraic sum of the electromotive forces in that path. KIS See Knowbot Information Service. KISS Keep It Simple Stupid. A tongue-in-cheek, but all-too-relevant design and management philosophy. Google is an excellent search engine on the Internet whose success is, in part, due to the relative absence of bells and whistles. The early Apple Macintosh computers held to this philosophy as well, developing a one-button mouse when many others were using two- or three-, and maintaining standards for the operating system that enabled new users to quickly figure out how to use it. KISS method A system-independent architecture related to information systems modeling, which is described in terms of object-oriented concepts by its author, Gerald Kristen. KISS concepts are presented in a series of stages, and the model and presentation are sufficiently different from other works in the field of object-oriented (OO) programming that it has not excited a lot of interest in the OO programmers’ community. Kittyhawk A line of very small-sized (less than 2 x 3 in.) 20- and 40-MByte, 44-pin IDE hard drives distributed by Hewlett Packard for use in palmtop text and PDA computers. KLAS-TV An early commercial adopter of all-digital advanced television (ATV) technology. KLASTV is a Las Vegas CBC affiliated owned by Landmark Communications, Inc., a privately held media company. Advanced television technologies were researched in the early 1990s by the Advisory Committee on Advanced Television Service (ACATS), with digital technologies coming in late in the process, but then becoming the central focus of ACATS evaluations. The ACATS Final Report was presented in 1995, paving the way for broadcast stations in

North America to begin to implement higher quality, standardized digital television services. KLASTV was the first broadcaster in the Los Vegas region to offer end-to-end digital technology and transmissions, in April 2000. Prior to offering digital subscriber services, KLAS-TV delivered digital programming 2 years in a row to the National Association of Broadcasters (NAB) annual trade show at a Las Vegas convention center, establishing themselves as one of the pioneer commercial providers of all-digital broadcast programming. System components for KLAS-TV equipment were developed and provided by Harris Broadcast Communications, who also provided the radio frequency Test Bed used in the ACATS evaluation of prototype digital broadcast systems. See Advisory Committee on Advanced Television Service, Harris Broadcast Communications. Kleinrock, Leonard In 1976, authored Queueing Systems Volume II – Computer Applications, a publication which helped the spread and acceptance of packet-switching technology. Kleist, Ewald Christian von See von Kleist, Ewald Christian. kludge, kluge Patchwork, improvised, or makeshift hardware or software, which can result from 1. time or material constraints, 2. sloppy workmanship, lack of foresight, 3. communication problems between decision-makers and implementors, or 4. staff changes or design changes during a protracted project. Kludge usually has a negative connotation, especially with software that tends to be sluggish from lack of structure and optimization, while well-conceived, but time-constrained projects are more often called “quick-and-dirty.” Even well-begun projects can become kludgy after awhile, in which case engineers will generally advise, “Time for a ground-up rewrite!” Klystron, klystron From the Greek “klyzo.” A highvacuum electron tube that uses electric fields to cause the “bunching” of electrons into a well-focused beam. The beam’s kinetic energy is converted and amplified into ultra-high frequency radio waves (microwaves). Klystron was established as a trademark and as such is spelled with a capital letter, though the term is now also used generically to describe the historic line of Klystron tubes. Klystrons were used widely as oscillators and applied to radar transmitters until they were superseded for some applications by cavity magnetrons. Current commercial Klystrons that developed from the historic tubes are long-life, reliable, remanufacturable components. The Klystron evolved from pioneer versions of the magnetron which were developed in the 1920s. Russell H. Varian and Sigurd F. Varian respectively designed and constructed the first Klystron prototype at Stanford, beginning in 1937, in collaboration with William Hansen. The July 1937 notes of Russell Varian describe the “Rumbatron Oscillator or Amplifier” and input from William Hansen regarding a “spherical rumbatron with one core reaching to the center.” The rumbatron moniker was based on

Hansen’s previous work on cavity resonators. The Varians combined this with principles of velocity modulation to create the Klystron, which was publicly announced in 1939. While Hansen went on to develop linear accelerators, the Varian brothers and other scientists, including their friend and associate, Edward L. Ginzton, applied the new technology to the development of radar systems during World War II and cofounded Varian Associates in 1948.

K

Top: The Klystron and its inventors at Stanford in 1939. Clockwise from the left are Sigurd Varian, David Webster, William Hansen, John Woodyard (a graduate student), and Russell Varian. Bottom: Russel and Sigurd Varian in 1951 with a high-powered Klystron component. Russell Varian also holds a small Klystron of the type used for radar, navigation, and communications applications. [Copyright 1939 and 1951 Stanford News Service archives; used with permission.]

The radio waves in historic Klystron tubes are drawn from a high-voltage electron beam in such a way that much of the energy is dissipated, resulting in low efficiency levels compared with succeeding technologies. However, klystron technology was never fully superseded, especially in broadcast applications, and some scientists felt the efficiency could be improved. The Lewis/Varian version of the klystron technology, developed in the mid-1980s,

recovers the wasted energy by recycling the electron beam, effectively doubling the usable portion of the radio frequency and, consequently, reducing power consumption in UHF television transmitters. Commercial production of the new technology began in 1990 on the product now known as the CPI MDC klystron. Commercial broadcasting klystrons come in a variety of configurations supporting frequency bands such as the C-band at different channel capacities (usually 6, 12, or 24). There may be separate tubes for image and audio amplification. Cooling with water is typical in klystron applications where the tube becomes hot. See bunching; Ginzton, Edward; cavity magnetron; magnetron; Varian, Sigurd and Russell; Varian Associates. KM See knowledge management. KMID key material identifier. A term associated with Message Security Protocol. KMS See Knowledge Management System. KNET See Kangaroo Network. knife switch In old telegraph keys, a type of switch which could short the contacts of the key in a series so the idle line was in a steady mark condition, with current flowing through. This was also called a break switch. Opening the knife switch interrupted the current in all the sounder electromagnets on the line so that operators were made aware that someone was about to send a message. knockout A raised or indented region of a receptacle which can be punched out or otherwise removed to provide access for wires, jacks, or other fittings. Common in general purpose electrical junction boxes. Knowbot Information Service KIS. A uniform client/server means of interacting with, and displaying, information from a variety of remote directory services typically found on Unix systems, such as Finger, Whois, and others. A query to KIS uses white pages services to these types of systems and displays the results of the search in a consistent format. See Knowbots. Knowbots In a Knowbot Information Service, programs which carry out the search and retrieval of information from distributed databases as requested by the user. The Knowbots may carry the information or may pass it among one another. See Knowbot Information Service. knowledge analysis and design system KADS. A structured approach to developing knowledge-based systems. knowledge base system, knowledge-based system, expert system A computerized system of storing the accumulated knowledge of humans in a system which accesses and manipulates the information using artificial intelligence programming strategies and rules to accomplish information delivery and problem-solving at a sophisticated level. knowledge engineering Acquisition of knowledge from a human expert or experts and its incorporation into an expert system. Knowledge Interchange Format KIF. Computer

language for the manipulation of knowledge data and interchange of knowledge among disparate programs. Intended not as a user interface, but as an internal representation for knowledge within programs or related sets of programs. knowledge management KM. The process of assessing, prioritizing, and effectively utilizing and distributing knowledge, that is, information that can be translated into profitable (in its broadest sense, not just monetary) action. In the past, the amount of knowledge that could be acquired about any particular topic or issue was limited by access and resources to obtain that knowledge. Now access and knowledge-gathering have improved by orders of magnitude through modern technologies that link people to people and people to information resources in an unprecedented way. This shifts the emphasis from acquiring information to more effectively searching, gathering, and using information. Thus, issues of knowledge management and its subset data mining have become important priorities. Knowledge Management Benchmarking Association KMBA. A trade organization of KM professionals, KMBA conducts benchmarking studies to identify various means of improving knowledge management activities. http://www.kmba.org/ Knowledge Management System KMS. A commercial product from Knowledge Systems, Inc., originally based on research and development of the hypertext management software called ZOG from Carnegie-Mellon University. Knowledge Query and Manipulation Language KQML. A high level language that is part of the DARPA Knowledge Sharing Effort. It is a language and messaging protocol for exchanging information and knowledge as part of the larger project to create technology to facilitate development of large-scale, shareable databases. KQML can be used to support interoperability among intelligent agents in distribution applications. See Reticular Agent Definition Language. knowledge worker An individual who provides, gathers, organizes, or dispenses useful, relevant knowledge for a particular purpose or for the attainment of a generally understood or stated goal that generally can be translated into action. This moniker has emerged due to two major forces: the continuing automation of industrial sectors (replacing people with machines/robots) and the continuing “knowledge explosion” resulting from the spread of communications technologies. The term is attributed to Peter Drucker in the 1950s and was revisited and more narrowly defined by Robert Reich in the 1990s. Information gathering has always been important to businesses and other institutions, but now there is a need for a level of expertise in filtering and prioritizing raw information through and into targeted knowledge of significant value (likely to result in profit or the attainment of educational or humanitarian goals). A knowledge worker is someone with the research or analytical skills to help attain these goals. In terms of computer software, knowledge workers are often skilled at using computer search, statistical,

or database systems and interpreting or distributing the knowledge gained, or may work in close conjunction with specialists and programmers when designing expert systems (e.g., medical diagnostic assistant software). See data mining, knowledge management. Knowlton, Kenneth C. (1931- ) An American pioneer in computer graphics and researcher at Bell Laboratories, Knowlton studied and experimented with many aspects of computer imagery, computer art, motion automation, and fast data storage, often in collaboration with L.D. Harmon. In 1959, Knowlton co-authored a report for the U.S. Patent Office entitled A Notation System for Transliterating Technical and Scientific Texts for Use in Data Processing Systems. As his explorations turned to computer imagery, Knowlton grasped a concept often overlooked by artists using traditional “paint” tools in a computer environment: the computer can be used to generate types of art and images that cannot (or should not) be executed by human hands. In the course of his research, he and his collaborators produced a rich variety of mosaics, plots, grayscale images, and even computer-based films. Remember that these pioneers had to invent and write their own software systems for accomplishing their goals. In the 1960s, no commercial desktop paint and animation programs were available off-the-shelf (they weren’t common until 1986). Many goals were attained by typing in raw numbers in low-level languages. To aid him in automating the animation process, Knowlton developed a motion language for creating short films. Together with filmmaker Stanley VanDerBeek, he developed a series of abstract animated films called Poem Fields. The tools invented to enable artistic visions to be derived from computer technology are applicable to many areas of scientific research and manufacturing including digitization, pattern recognition, artificial intelligence, robotics, and more. In 1979, Knowlton coauthored articles on visual perception and the use of sign language as a form of telephone communication, with Vivien Tartter. Over the decades, Knowlton’s interests in image processing and image generation remained strong and he has been awarded a couple of dozen patents for his work. As examples, in 1990, Knowlton and Wang Laboratories applied for a U.S. patent for what is essentially an ebook, an electronic book viewed through a video display (#5283864 ‘94). Following this, in 1994, Knowlton and Wang applied for a patent for a document processing system including an optical scanner (#5517586 ‘96). See Harmon, Leon; Shroeder, Manfred. Knuth, Donald (1938- ) Knuth’s texts on data structures and algorithms are heavily used, and widely considered by programmers to be the “bible” of important basic programming structure information. Fundamental search and distribution trees and much more are in the Knuth texts. It would be difficult to develop sophisticated database software without them. Knuth is also known for authoring the powerful document system called TeX (pron. tek), which

is one of the few that can handle complex mathematics-related text formatting. Koala Telecommunications Project An open educational project enabling school children to telecommunicate with Earthwatch researchers studying koalas on Kangaroo Island in South Australia. KOLD-TV A pioneering digital broadcast station, KOLD 13 began using a networked digital video server in daily broadcasts in 1995. In October 1998, the Federal Communications Commission granted a number of commercial digital television station licenses, including Station KNSV-TV, Phoenix, and KPHO-TV, Phoenix. Konexx Modem Koupler A battery-powered commercial modem/modem adapter combination from Unlimited Systems. Konexx allows a modem to be hooked into various types of phone lines and cellular phone systems while traveling. Kotel’nikov, Vladimir Aleksandrovich (1908- ) A Russian contributor to fundamental research in communication theory, and theory and practical research in astrophysics. He is especially well known for the use of radio waves to locate and measure distances to planetary bodies and for contributions to early satellite communications. He is also remembered for publishing “On the carrying capacity of ‘ether’ and wire in electrical communication” (1933) that describes a theory of sampling and the representation of a continuous signal from discrete samples. His theories were later supported by the work of Claude Shannon. Kotel’nikov served as V.P. of the USSR Academy of Sciences and chaired the Scientific Council on radio astronomy. While at the Institute of Radioengineering and Electronics, he initiated research in the submillimeter wave band. See pulse code modulation; sampling theorem; Shannon, Claude. KPI See Key Performance Indicator. KQML See Knowledge Query and Manipulation Language. Krum, Charles and Howard An American father and son team who worked together in the early 1900s to develop and patent a variety of telegraph transmitters and printing machines. One of their early successes was a printer created by interfacing a modified typewriter with a telegraph line, developed at the end of 1908. With a mechanical apparatus ready to use, it became necessary to develop some way to synchronize the pulses and the printing. For this, Howard Crumb applied for a start-stop patent in 1910. krypton laser A type of gas laser which is primarily krypton that can be used to produce intense red light, or when used with certain optic enhancements, several colors. This is similar to an argon laser, except that it produces a little less light; sometimes argon and krypton are combined. Krypton lasers are typically water-cooled. Kurz, Karl Information on this German experimenter is scarce, but we know he collaborated with Heinrich Barkhausen in discovering BarkhausenKurz oscillations. See Barkhausen-Kurz tube.

K

KS See Kearney System. KSR Keyboard Send/Receive. Descended from teletype terminology, a combination transmitter and receiver which can transmit only from the keyboard, as it does not incorporate storage devices such as punch cards, tapes, floppy disks, or magnetic memory. KTH Kungliga Tekniska Hogskolan. The Royal Institute of Technology in Stockholm, Sweden. KTI Key Telephone Interface. KTS 1. See key telephone system. 2. See Kill the Spams. Ku-band A range of microwave broadcast frequencies from approximately 11 to 14.5 GHz which is further subdivided into fixed satellite service (FSS) and broadcasting satellite service (BSS). Ku-band is used primarily for data transmission, private networks, and news feeds. Satellites transmitting Kuband signals tend to be powerful enough for the receiving dish to be small and convenient. Uplinks are in the 14- to 14.5-GHz range and downlinks in the 11.7- to 12.2-GHz range. In November 2000, The Federal Communications

Commission (FCC) extended permission to providers of nongeostationary satellite services to operate in certain segments of the Ku-band and issued rules and policies to govern their operations. It was felt that this would stimulate new competitive services such as high-speed Internet access, telephony services, and media broadcasts. It was further hoped that satellite transmission availability would increase services to rural areas. The FCC determined that Multichannel Video Distribution and Data Services (MVDDSs) could operate in the 12.2- to 12.7-GHz frequencies without interfering with incumbent Broadcast Satellite Services (BSS). See band allocations for a chart. See broadcasting satellite service, direct broadcast satellite, fixed satellite service. KV Bell Telephone jargon for key telephones (K = key, V = voice). The term was derived from the Universal Service Ordering Code (USOC) commonly used until the time of the AT&T divestiture in the mid-1980s. KVW Bell Telephone jargon for wall-mounted key telephones. See KV. KWH See kilowatt-hour.

L L symb. inductance. See inductance. L CXR A backbone communications system based on L carrier coaxial technology developed in the 1930s in the U.S., known generically by the public through warning signs as the Transcontinental Cable system. The system was intended for key government communications and civil defense, interconnected through facilities with underground repeaters, and maintained by Bell telecommunications workers. The system was designed to transmit both telephone and television signals. In the postwar years, the system was upgraded about every 10 years. The L-1 system of the 1940s gave way to an L-3 system by the 1950s and 1960s. (L-2 was used for a special installation between Washington, D.C. and Baltimore.) Later, through the use of repeaters every couple of miles, 20-tube L-4 cable centers were established approximately every 150 miles. By the 1970s, L-5 circuits had been established. The capacity of the system improved from a few MHz in the 1940s to 57 MHz in the 1970s with voice capacities increasing from a few hundred voice channels to more than 100,000. Following the Cold War, the repeater stations, which resembled stone garden sheds over concrete vaults every few miles along the cable route, were sold off. The old physical infrastructure was gradually replaced with fiber optic cables (with 20 times the capacity of the L-5 system) and satellite links. See L carrier. L carrier An older, analog, frequency division multiplex (FDM), long haul phone system that was common before digital services became prevalent (metropolitan areas using FDM more commonly used N carriers). U.S. Department of Defense L carrier communication systems in the post-World War II period stretched in two main east-west links from Washington, D.C., west to California and south to the tip of Florida, with many smaller trunk tributaries. See L CXR.

L multiplex LMX. Analog multiplexing circuits in L carrier coaxial transmissions media. L Series Recommendations A series of ITU-T recommendations providing guidelines for construction, installation, and protection of cables and other elements of outside plant telecommunications. These guidelines are available as publications from the ITU-T for purchase. Since ITU-T specifications and recommendations are widely followed by vendors in the telecommunications industry, those wanting to maximize interoperability with other systems need to be aware of the information disseminated by the ITU-T. A full list of general categories is listed in Appendix C and specific series topics are listed under individual entries in this dictionary, e.g., K Series Recommendations. See L Series Recommendations chart. L system See L CXR. L1 cache See level 1 cache. L2 cache See level 2 cache. L2F 1. See Layer 2 Forwarding Protocol. 2. Legacy to the Future. L2TP See Layer 2 Tunneling Protocol. L2TPext See Layer 2 Tunneling Protocol extensions. L8R An abbreviation for “later” commonly used in online public forums, email, and discussion list messages. It is particularly prevalent in live chat areas on the Internet as a substitute for “goodbye.” L-band A portion of the electromagnetic spectrum ranging from 500 to 1500 MHz. Within this range, the frequencies between 950 and 1450 MHz are set aside for mobile communications. Global Positioning Systems (GPSs) use the L-band frequencies, as do some of the planet probe systems. See band allocations for chart. LA 1. See listed address 2. local area. LAAS See Local Area Augmentation System.

L

ITU-T L Series Recommendations Recom. Description L.1

L.2 L.3 L.4 L.5 L.6 L.7 L.8 L.9 L.10 L.11

L.12 L.13

L.14

L.15

L.16

L.17

L.18 L.19 L.20 L.21 L.22

Construction, installation and protection of telecommunication cables in public networks Impregnation of wooden poles Armouring of cables Aluminium cable sheaths Cable sheaths made of metals other than lead or aluminium Methods of keeping cables under gas pressure Application of joint cathodic protection Corrosion caused by alternating current Methods of terminating metallic cable conductors Optical fiber cables for duct, tunnel, aerial, and buried application Joint use of tunnels by pipelines and telecommunication cables, and the standardization of underground duct plans Optical fiber joints Sheath joints and organizers of optical fiber cables in the outside plant Measurement method to determine the tensile performance of optical fiber cables under load Optical local distribution networks – factors to be considered for their construction Conductive plastic material (CPM) as protective covering for metal cable sheaths Implementation of connecting customers into the public switched telephone network (PSTN) via optical fibers Sheath closures for terrestrial copper telecommunication cables Outside plant copper networks for ISDN services Creation of a fire security code for telecommunication facilities Fire detection and alarm systems, detector and sounder devices Fire protection

Recom. Description L.23

L.24 L.25 L.26 L.27

L.28 L.29

L.30 L.31 L.32 L.33

L.34 L.35 L.36 L.37 L.38

L.39 L.40

L.41 L.44 L.45

L.46

L.47

Fire extinction – classification and location of fire extinguishing installations and equipment on premises Classification of outside plant waste Optical fiber cable network maintenance Optical fiber cables for aerial application Method for estimating the concentration of hydrogen in optical fiber cables External additional protection for marinized terrestrial cables As-laid report and maintenance/repair log for marinized terrestrial cable installation Markers on marinized terrestrial cables Optical fiber attenuators Protection devices for through-cable penetrations of fire-sector partitions Periodic control of fire extinction devices in telecommunication buildings Installation of Optical Fibre Ground Wire (OPGW) cable Installation of optical fiber cables in the access network Single mode fiber optic connectors Fiber optic (non-wavelength selective) branching devices Use of trenchless techniques for the construction of underground infrastructures for telecommunication cable installation Investigation of the soil before using trenchless techniques Optical fiber outside plant maintenance support, monitoring and testing system Maintenance wavelength on fibers carrying signals Electric power supply for equipment installed as outside plant Minimizing the effect on the environment from the outside plant in telecommunication networks Protection of telecommunication cables and plant from biological attack Access facilities using hybrid fiber/ copper networks

label 1. A symbol, or group of symbols, often mnemonic, that identifies or describes an item, routine, record, file, application, or process. 2. In programming, a reference point, usually for a procedure, function, or subroutine. The label may have a specific meaning to the interpreter or compiler that processes the code instructions or it may be a convenience for the programmer for organizing code and simply be ignored when the code is processed, depending upon the environment. 3. In networks, a convenient name for a device to facilitate access. For example, a printer on a network known to the system as LZPTX5103, may be assigned a label such as Building 3 Laser, to make it easier for people to recognize. 4. In ATM and Frame Relay networks, a short, fixed-length identifier that facilitates packet/ frame forwarding. See label switching. label swapping In label switching networks, a router will commonly assign a new label to the received transmission in preparation for forwarding it to the next “hop” or leg in its journey toward the destination. See label switching. label switching In ATM networks, a switching mechanism intended to take advantage of the flexibility and scalability of Internet Protocol (IP) routing. Label switching combines some of the aspects of Layer 2 switching with Layer 3 routing, so the distinction between switching and routing is not as clear as in other transmission schemes. A labelswitching router can forward IP datagrams based upon a label associated with the packet and will usually assign a new label for the subsequent routing “hop” in the connection. See Multiprotocol Label Switching, optical-label switching, tag switching. labeling algorithm 1. A means of calculating the shortest path in network routing. 2. A means of inserting copy protection labels into data, such as compressed video data, so the information can be tagged, or otherwise identified, and can only be written or read under prescribed circumstances. This type of system is being developed to enable vendors to provide digital services to home consumers without fear that the products will be widely pirated and redistributed. It is being experimentally applied to the design of copy-protectable mass storage devices. Laboratory for Computer Science LCS. An interdepartmental facility at the Massachusetts Institute of Technology (MIT) engaged in computer science research and engineering. LCS was founded in 1963 with support from the U.S. Defense Department as a result of the launching of the Sputnik satellite. Members of the LCS have been involved in many important historical computer network developments including the ARPANET, Ethernet, Internet, and World Wide Web. They have also been involved in research and development of encryption technologies, electronic mail, and computer accounting software. Many prominent companies have been founded by LCS participants, included 3Com, Lotus Development, and RSA Data Security. LCS works cooperatively with relevant departments and with the MIT Artificial Intelligence Laboratory. LAC Loop Assignment Center.

LACE See Low-power Atmospheric Compensation Experiment. lacing cord A strong cord, sometimes coated or waxed, used to bundle wires strung along the same path. ladar laser Doppler radar. See Doppler, laser, radar. LADS local area data service. LADT See Local Area Data Transport. lag To delay, linger, slacken, slow, be retarded, or tarry. Lag occurs in computer applications when the speed of the system is unable to match the speed of the interaction of the user. Lag is characteristic of dialup modem communications, where the speed of the data transmission doesn’t match the speed of the computer processor. Lag occurs on data networks when congestion occurs; that is, the number of packets may exceed the ability of the system to handle and transport them. See cell rate, hysteresis, leaky bucket. LAGEOS I The Laser Geodynamics Satellite, developed and launched by the Marshall Space Flight Center in May 1976. LAGEOS was one of the earlier remote-sensing satellites used for Earth sciences research.

Satellites come in all shapes and sizes. The LAGEOS resembles a high school dance mirror-ball studded with gems and coated with a golden spray. The 2-foot diameter satellite was placed into orbit to sense and measure movements in the Earth’s surface while orbiting from pole to pole. [NASA image.]

Lakeside Programming Group A collaboration of programming friends, which included Bill Gates, Paul Allen, and Ric Weiland. The group created a payroll program in COBOL for a company in Portland, Oregon. They were informally named after the Lakeside private school attended by its members. At the same time, the group was engaged in a programming contract to build scheduling software for a school. Eventually Gates and Allen formed Traf-O-Data in the early 1970s, to create a traffic analysis program.

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The partnership that led to the formation of the Microsoft Corporation. See Gates, William; Allen, Paul; Microsoft Corporation. LAI See Location Area Identity. LAM 1. line adapter module. 2. See Lobe Attachment Module. LAMA See Local Automatic Message Accounting. lambda The 11th letter of the Greek alphabet, used as a symbol in a number of mathematical and logical contexts. Lambda symbolizes the null class, von Mangoldt’s function, and wavelength. Lambda-Connect Project A Lawrence Livermore ultracomputing development project funded by the Laboratory Directed Research and Development Program. In recent years, the performance gap between processing units and the links between the processors has been widening. This interesting project in parallel multiprocessing seeks to narrow the gap by overcoming the bottlenecks in transmitting data among processors via traditional electronic connections. The LL team believes it can replace electron flow with photon flow (light pulses of different wavelengths). Speed improvements of up to 32 times are considered feasible. The use of optical interconnects also makes it practical to pack microprocessors in higher densities which, presumably, also improves data transport speeds and processing times. Ultracomputing projects are of particular interest to strategic and scientific computing applications and may be used by the U.S. Department of Energy (DoE) Accelerated Strategic Computing Initiative for nuclear technologies simulations and testing and to the Department of Defense (DoD) for strategic planning and intelligence gathering and processing. See lambda switching, optical burst switching. lambda switching Also called wavelength switching, this is a technique used in high-speed optical networks to switch individual optical wavelengths into different paths to route data through the network. It is more akin to circuit switching than packet switching and can be implemented as end-to-end connections. Fiber optic networks typically use lambdas (wavelengths) in the near infrared spectrum, translating into frequencies of around 100 terahertz (THz). In conjunction with multiplexing, which enables many separate wavelengths to be transmitted along a single fiber, lambda switching can be used to create virtual circuits. Qwest and other carriers announced began to deploy lambda switching in their communications networks around 2000 and 2001. See dense wavelength division multiplexing, Gilder’s law, lambda, optical cross connect. lambdasphere The environment within optical transmissions paths that channels many wavelengths. George Gilder is a speaker and well-known proponent of optically switched networks and is credited with coining the term lambdasphere. See Gilder’s law, lambda switching. lambert (symb. – L) A centimeter-gram-second (CGS) system unit of luminance, equal to the bright-

ness of an ideal diffusing surface that radiates or reflects light at 1 lumen per square centimeter. lame A colloquial term often used in programming or electronics to derisively describe an uninspired or poor device, program, or solution to a problem. The term is based on the concept of limping along on one leg and thus not embodying positive qualities such as speed, efficiency, or grace. A person who frequently comes up with weak or lame comments or solutions may be dubbed a “lamer.” Unfortunately, many computer manuals are pretty lame, written by persons with insufficient teaching skills or knowledge of the software to undertake this important task. See lame delegation. lame delegation On the Internet, a situation in which one or more authoritative domain name servers (DNS) that convert Internet Protocol (IP) addresses into registered names are not responding correctly for the specified domain (which may have been called by a system higher in the hierarchy). Lame delegation occurs for a number of reasons: • Secondary servers, which are expected to function as authoritative servers, may not respond correctly. If a secondary server is unspecified, or not working correctly, the situation is lame in the sense that the second “leg” isn’t working properly. Since secondary name servers are not mandated, only recommended, this is not an uncommon occurrence; most people associate this meaning with the term. • The name server may respond incorrectly from a cache rather than directly or may be configured incorrectly. • There may be a lack of communication. If users change domain names, manage their own IP numbers, or switch Web hosts without coordinating with the name serving authority and the ISP, all sorts of lame delegation errors can occur. Lame delegations can result in email delays, lookup slowdowns, and even a Web site “disappearing” from the Internet (not being accessible). If the primary and secondary servers are on the same physical machine and that machine goes down, there is no backup name server and a lame delegation would be in effect until the system came back online. See domain name server, lame. laminate n. A structure composed of layers, often tightly sandwiched or bonded together. Laminated materials are often used in electronics, from early voltaic piles, which sandwiched moistened materials between layers of metal plates, to magnetic cores and semiconductors, in which layers of various materials are combined according to their electromagnetic properties. An individual layer in a laminated structure is called a ply. See semiconductor, voltaic pile. lamp An illumination apparatus that converts energy into light (usually visible light). In its basic form, a lamp consists of a light-producing source and a holder such as a wick in an oil-holding vessel, bulb

in a handheld, battery-operated container (flashlight), fluorescent bulb in a fluorescent receptacle, lightemitting diode in an electronic device, or filamented vacuum bulb in a desk or floor stand. Lamps were used in some of the earliest communications technologies. By blocking the light from a lamp to signify dark or light, a binary communications code could be devised to send signals over distances. A shutter made the process easier. Shuttered lamps were used for many decades to send signals overland and among ships at sea. Lamps are also used as sources for photographic lighting, especially as “flash bulbs” to provide supplemental illumination in low-light conditions. Not all lamps emit light in the visible frequency ranges. Infrared or ultraviolet light cannot be directly seen by humans, but the subjects illuminated may be seen with special equipment that translates the reflected light into visible frequencies or other forms of energy. See Edison, Thomas A. LAMP See Large Advanced Mirror Program. lampblack A sooty, dark carbon dust deposited by a smoking flame, as on the inside of a glass lamp globe. While its presence in lamps is usually undesirable, lampblack has commercial applications in the fabrication of some types of resistors. LAN See local area network. LAN adapter A hardware peripheral device or card that connects a computer to a local area network (LAN). Not all computers require LAN adapters; some come equipped with network cards and ports ready to attach to various connectors, commonly 10Base-T or 10Base-2. However, some require an intermediary device between the network card and the network cable in the form of a LAN adapter. LAN aware Applications, systems, and devices that can recognize and appropriately respond to an interfaced connection to a local area network (LAN). This involves being able to communicate with other devices on the net as security permits, locking and unlocking files as needed, using queuing mechanisms appropriately, etc. Some operating systems are designed to be LAN aware. Others run with LAN software installed on top of the operating system. LAN Channel Station LCS. 1. In frame-based networking, a channel protocol for LAN/mainframe intercommunications. In IBM mainframe-related LCS, host applications define a consecutive pair of subchannels for channel reads/writes through TCP/IP. LCS enables a local area network (LAN) MAC frame to be transported and provides a command interface for activating/deactivating and querying LAN interfaces. 2. A Bus-Tech commercial control unit emulation (also known as 8232) that provides a pass-through for exchanging data between a local area network/wide area network (LAN/WAN) and a mainframe through TCP/IP. LAN Emulation See asynchronous transfer mode, LANE. LAN Manager An early, commercial OS/2-based multiuser network operating system intended to run over TCP/IP or NetBEUI protocols. Microsoft and

3Com’s LAN Manager came in two versions: for MS-DOS, Microsoft Windows, and IBM’s OS/2, and for Unix/UNIX connections. LAN Protocols A catchall phrase for a wide variety of protocols developed for local area computer networks, such as AppleTalk, Ethernet, TCP/IP, IPX, and others. LAN segment In Frame Relay, a LAN linked to another LAN using the same protocol through a bridge. See bridge, hop, router. LAN Server A commercial multiuser network operating system from IBM, based on OS/2 and NetBIOS. LAN Server supports a variety of client computer operating systems, including OS/2, Microsoft DOS and Windows, and Apple Macintosh. It has been superseded by the OS/2 server version. LAN switch A local area network (LAN) switch, in its simplest sense, is a stand-alone box with connections, which simply directs traffic along one or more pathways. However, with improved technology, LAN switches are incorporating more and more intelligent processing capabilities, and some are almost indistinguishable from routers. Some are available as modular peripheral cards that fit into multiswitch card chassis. LAN switches can help reduce or more efficiently handle congestion and can improve response time on networks. They have the capability to redirect the World Wide Web queries of users to local caches, and reduce Internet queries and can help balance network traffic among servers. LANCE Local Area Network Controller for Ethernet. Land attack, land.c A malicious software program that became prevalent on the Internet in 1997, the Land attack was similar to an earlier SYN attack program. Land was programmed to attack systems using Internet Protocol (IP) communications by interfering with the stack. Certain routers were also vulnerable. A broad segment of operating systems from Apple, Cisco, Microsoft, and Sun and several BSD systems were found to be vulnerable. Some machines crashed while others hung or experienced slowdowns, depending upon how robust the operating system was and whether it could still function while one aspect of it was caught in an endless loop through spoofing that tricked the system into calling itself. A more Microsoft-aggressive version called latierra.c was later released on hacker sites. Vendors posted patches to reduce or remove the vulnerability and updated subsequent releases of software to reflect these changes. See Denial of Service attack, Trojan horse, virus. land/groove recording, land and groove recording A high-density recording technology for magneto-optical media. DVD disc surfaces are divided into annular zones, keeping the length of a sector and the recording density mostly constant through the disc. The zones are divided into two types of tracks: land tracks and groove tracks. These tracks, in turn, are divided into sectors. The hierarchical division into smaller units is similar to the storage and access

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formats used on hard disks, with adaptations to fit the nature of optical disks. Data are recorded on the land (the higher surface) and the groove (the indented surface), while address information is encoded in the pits. Permanent data that are readable but not writable by the user are kept separate from the user recording fields. See wobbled groove, wobbled land groove. LANDA Local Area Network Dealers’ Association. This is now called NetPros by LANDA. The organization promotes and supports excellence among Canadian resellers, consultants, and systems integrators in the information technology (IT) industries. http://www.netpros.ca/ landline, land-line, land line Communications circuits, especially telegraph and telephone, which travel through terrestrial wires and stations. Many mobile units interface with landlines, so that even if a call originates as a wireless call, it may be completed as a landline call to extend distance and free up wireless channels. Landsat A series of satellites first launched through federal funding in the mid-1960s for remote sensing of the Earth from space. The Landsat Earth sensing system launches were initiated in 1966 as a response to the announcement of plans for launching civilian Earth Resources Observations Satellites (EROS). As a result, NASA began to plan a satellite launch in order to secure information on Earth resources and provide for national security provisions in space. This led to the launch of the Earth Resources Technology Satellite (ERTS-1) in 1972, with similar satellites launched in 1975 and 1978. The program was renamed Landsat in 1975. Landsats 4 and 5 were launched in the early 1980s, and jurisdiction was transferred to the U.S. National Oceanographic and Atmospheric Administration (NOAA). In 1986, during the Reagan administration, jurisdiction was changed to a commercial company, EOSAT, and the primary users became large institutions that could afford expensive satellite data. Complete archiving of data was not always undertaken. EOSAT designed and built Landsat 6, which failed on launch. In 1992, legislation was passed to return future Landsat missions to the public, and Landsat became part of NASA’s Mission to Planet Earth program in 1994. Planning began for the Landsat 7 project. Landsat satellites are in near-polar orbits, designed to be sun synchronous; that is, the satellites cross the equator at the same local sun time in each orbit. Thus, lighting conditions are kept uniform. The satellites are equipped with telemetry and remote sensing equipment, including cameras and multispectral scanners. Data collected from early Landsat projects were stored in X-format, that is, band-interleaved by pixel pair (BIP-2). This format was superseded by EDIPS (EROS Digital Image Processing System) with a resolution of 3596 pixels x 2983 scanlines, in bandsequential (BSQ) or band-interleaved-by-line (BIL) formats.

The Landsat digital images are an extremely valuable resource for scientific inquiry, environmental education, mapping, and long-term research and resources planning. landscape An associative word that refers to the direction of roughly rectangular objects, usually printouts, photographs, or monitors, which are oriented so the short side is vertical and the long side is horizontal. Some monitors can swivel to either landscape or portrait mode at the convenience of the user. The term is widely used in the photography and printing industries to describe the orientation of text or images on a page. It is important to correctly specify the orientation of a page before sending documents from a computer to a printer. Often an icon will be available as a clickable button for choosing the setting. Most software will default to portrait orientation. Contrast with portrait. 1234567890123456789 1234567890123456789 1234567890123456789 1234567890123456789 1234567890123456789 1234567890123456789 1234567890123456789 1234567890123456789 1234567890123456789 1234567890123456789 1234567890123456789 1234567890123456789

Landscape orientation

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Portrait orientation

LANE LAN Emulation. Local area network (LAN) emulation services and protocols running over asynchronous transfer mode networks. See asynchronous transfer mode and the appendix for greater detail. language In computer programming, a means of representing instructions, procedures, functions, and data through symbols and syntax which can be interpreted into machine instructions to control the computer. Common high level programming, scripting, and page description languages include Perl, Java, C, C++, PostScript, LISP, Pascal, BASIC, Cobol, and FORTRAN. A common markup language used on the Web is HTML. There are also job control languages, description languages, graphics languages, and low-level assembly and machine languages. Language of Temporal Ordering Specification LOTOS. A language for the formal process and algebraic specification of computer network protocols for concurrent and distributed networks, described as ISO 8807-1990. LOTOS has been used internationally to specify many systems, especially by university groups. LOTOS is applicable to the specification of Open Systems Interconnect (OSI) model systems, for example. LANNET 1. large artificial neuron network. 2. A subsidiary company of Madge Networks, N.V., and leading supplier of next-generation Ethernet and ATM switching technologies for local area networks (LANs). LANNET was acquired by Lucent Technologies in 1998. LANtastic A commercial peer-to-peer NetBIOSbased network operating system from Artisoft. It

supports a variety of client computer operating systems, including Microsoft DOS and Windows, IBM’s OS/2, Apple’s Macintosh, and various Unix clients. lap A device used for grinding piezoelectric crystals. Since the resonance frequencies of crystals are due in part to their size and shape, the lap provides a means to fine-tune the crystal. See detector, quartz, Y cut. LAP 1. link access procedure. 2. See Link Access Protocol. laplaciometer An early analog calculator designed for complex mathematical work by J. Atanasoff and some of his graduate students in the 1930s. The laplaciometer was used to analyze the geometry of surfaces. These developments led to the design and creation of the Atanasoff-Berry Computer (ABC). See Atanasoff-Berry Computer. Laplink A popular, practical commercial hardware/ software networking utility introduced in 1986 for transferring files between computers, especially between laptop computers and office workstations. It is very common for mobile computer users to want to transfer the information from their laptops to their desk computers, and sometimes to transfer in the other direction as well (e.g., sales leads). Laptops typically have smaller hard drives and higher security risks than desktop computers, making it advisable to regularly move the data off the laptop. Transfers can be achieved in a number of ways, through a serial port, over a parallel connection, or through phone lines. In 1995 LapLink Host was added to the product line to provide technical support to remote workers. Laplink was developed by Traveling Software, Inc., a Washington State company devoted to supporting the needs of mobile users, founded in 1982 by Mark Eppley. lapping A technique for wrapping electrical tape, foil, or other ribbons around a central core so that the next edge overlaps the previous one, in order to create close contact and a good seal. laptop computer A low-weight, battery-powered, or combination battery/AC-powered portable computer. Laptops are generally considered to be computers that can fit easily on a lap, airline tray, train table, or other support surface in common moving conveyances. Laptops range in weight from about 3 to 7 pounds. Some people distinguish notebook computers as mid-range between laptops and palmtops, at about 2 to 4 pounds. Larger portable computers are called “luggables” or transportables, and the smallest ones are called palmtops and programmable calculators. They weigh from a few ounces up to about 2 or 3 pounds. The range of a laptop battery is usually 2 to 6 hours, and may be extended by using powersaver functions or turning off the monitor. Car lighter adapters may be used for powering a laptop or recharging the battery. Laptops have a variety of types of monitors, designed to be flat, light, and of low power consumption. Various LED, passive matrix, active matrix, and gas

plasma monitors are used on laptops. The active matrix screens are brighter and easier to see in dim or bright lighting conditions than screens that depend upon optimal ambient lighting. Many laptops are equipped with PCMCIA Type I or Type II card slots so the user can add lower power, compact peripherals such as extra memory cards, fax/modems, network ports, etc. LArc 1. A data archiving program descended from LZSS, developed by Lempel, Ziv, Storer, and Szymanski and further optimized and extended in the late 1980s by Okumura and Miki. Kazuhiko Miki reworked Okumura’s version of LZSS with Pascal and Assembler to create the archiving tool called LArc, whose file handling was quick and compact. Huffman coding was later incorporated into the software by Yoshizaki to create an even faster and popular version called LHarc. See LHarc. 2. See Livermore Automatic Research Calculator. Large Advanced Mirror Program LAMP. A research project involving the design and construction of a 4-meter-diameter segmented mirror with characteristics appropriate for deployment in space, completed in 1989. The segmented design enables large mirrors to be assembled. LAMP is the largest mirror designed for use in space, exceeding the Hubble astronomical mirror. See Large Optics Demonstration Experiment. Large Optics Demonstration Experiment LODE. A project to research the control of large, high-power laser beams, completed in 1987. Since then, LODE data have been used in the development of spacebased laser technologies and investigated for defense applications such as missile defense. See Large Advanced Mirror Program. large scale integration LSI. A term describing the evolution in electronics from systems with many separate large-sized components to systems with a smaller number of integrated small-sized components. Since the distances between various parts of the logic and physical circuits are greatly reduced in LSI, the processing speeds are also much faster. LSI made possible smaller, more powerful electronic components such as calculators, computers, automated appliances, digital watches, clocks, timers, and much more. See very large scale integration. large-core fiber A fiber cable with a core diameter that is broad in relation to most cables. A core of about 200 µm or greater can be considered large-core though the designation is somewhat dependent upon what is manufactured or commonly used at any particular time. For comparison, multimode fiber generally has a core diameter of about 56 µm. laser acronym light amplification by stimulated emission of radiation. A device that stimulates photons to produce coherent, nonionizing radiation in the visible spectrum and infrared wavelength regions. While lenses and mirrors are commonly used to direct laser beams, the essential components of a laser are a lasing medium, a resonant optical cavity, and a pumping system (optical, mechanical, or electronic).

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Lasers were invented in 1958 by Arthur Schawlow, a Bell Laboratories scientist, and C.H. Townes, a consultant to Bell. Numerous other scientists made important contributions to the further development of lasers. Unlike light from many other sources, such as incandescent bulbs, a laser beam remains very narrow and straight over long distances. Many people have seen lasers in the form of business presentation pointers or rangefinders on guns to facilitate aiming. The pointer light usually appears as a small, round, red dot. Lasers make great cat toys, too. Gems such as ruby and garnet (yttrium aluminum garnet) are commonly used in the production of lasers and many familiar laser implements project a red beam. Gallium arsenide is also used. Red lasers used in magneto-optical storage device read heads currently have wavelengths of about 650 nm, but blue lasers may become commercially available and will make it possible to record at higher areal densities. Blue lasers (ca. 410 nm) have a spot incident level almost 40% smaller than red lasers which would enable higher disc capacities and faster transfer rates. Lasers are used for thousands of commercial, industrial, and medical applications. They function as high precision surgical cutting tools in medicine, as imaging components in millions of consumer printers, and as signaling tools in a variety of networking tasks, especially through fiber optic cables. A very interesting new type of room-temperature quantum cascade laser technology originated in 1994. QC lasers offer greater control over frequency selection, and have many potential applications in remote sensing and industrial environments. Laser light is a minimum loss communications tool; in very pure straight fiber optic cable, the loss over distances is low, and the transmission cannot be surveilled in the same way that electrical wires can be monitored through emissions that extend beyond the cable. Laser light communications are not affected by electromagnetic interference (EMI) in the same way as many other means of transmitting information (there may be some possibility of EMI in long lines electromagnetically amplified at the splices, but optically amplified lines are being developed that may eliminate this problem). One should never aim a laser pointer at a person or animal, as there is a possibility of harm, especially if the laser shines on a cornea or retina. There may be permanent photochemical or thermal damage from such contact. See argon laser, cladding, fiber optics, overcoat-incident recording, quantum cascade laser, YAG, yttrium. laser cutting A laser can be used as a high precision cutting tool for surgical procedures and industrial/ commercial applications. Rubber stamps, wood blocks, and stencils cut with lasers have very fine, crisp, clean edges. laser diode A type of semiconductor light-emitting diode (LED) that emits coherent light in response to the application of voltage. See light-emitting diode.

laser fax A combination device that incorporates the printing features of a laser printer with the scanning and transceiver capabilities of a facsimile machine. This is a handy tool for small offices where separate high-capacity devices are not needed and space is at a premium. Ideally, a laser fax machine should be networkable so users can send and receive faxes without printing each one, and then select to print only the ones to be distributed and filed as hard copies. This saves paper and lineups at the fax machine. laser printer A printer that uses a computer-directed laser beam to render images. Laser printers typically use a specially treated drum that is influenced by the light of the laser. An impression is made on the drum by aiming very fine, high precision laser light beams at the coating, so the electrical charge is selectively altered. An electrostatic process then attracts the toner to the imaged areas (areas altered by the beam), and heat is used to fuse the toner onto the printing medium, usually paper or card stock. Laser printers generally print in resolutions ranging from 300 to 1200 dpi, although some can print at higher resolutions with special papers or plates capable of holding a very fine image. Some include Adobe PostScript page description interpreters. Speed of printing and PostScript capabilities are generally enhanced with extra memory. Laser printing is considered a dry printing process, as opposed to offset printing on a press that uses wet inks. It is not advisable to use recharged toner cartridges in laser printers. In most consumer laser printers, the toner cartridge also includes part of the drum mechanism, which has a limited term of use. Even if the recharge toner is of good quality, it is still possible for the aging drum to stress the printer, perhaps even damaging it. The money saved on toner cartridges may be offset by the potential loss due to damage or reduced lifespan of the printer. See dot matrix printer, dye sublimation, inkjet printer, thermal wax printer. laser range finder LRF. A device for determining distance through the use of a beam of coherent light and associated sensing systems to calculate the range. Gun sights, binoculars, camera autofocusing systems, and a number of security and surveillance systems use laser range finders. Depending upon the device, the range may be indicated symbolically with graphics or numbers. For example, the distance to an object may be displayed on the viewing screen in yards or meters, superimposed over the scene being viewed. Some laser frequencies can be harmful to the eyes; while many consumer devices use Laser Class 1 frequencies that are not considered dangerous, it is wise to be cautious. laser show A laser show is an entertainment display of differently colored laser lights crossing through the air, sometimes in a darkened room and sometimes falling on a display screen or domed theater surface. Some of the vector-based computer arcade games from the 1980s that successively drew colored lines around the screen give a general idea of a laser light show, except that it’s three-dimensional and bigger.

LAT See Local Area Transport. LATA See Local Access and Transport Area. latency Delay or period of dormancy. The speed of acquisition or perception of a thought, object, or communication in relation to the desired speed of acquisition or perception. Latency can result from the intrinsic properties of the communications medium or the communication itself. It can arise from the effects of the time it takes for information to transmit, or from the physical or logical pathways associated with the transmission. It can also result from crowding, congestion, misalignment, mistuning, unanticipated effects or traffic, and a large number of other possible factors. Response time is related to latency, with reduced latency usually desirable in this context. Every aspect of communications has to concern itself with latency. In networking, there has been a lot of research and quantification of latency in order to design, evaluate, and tune computer architectures to carry out desired tasks. Here, latency is usually expressed in small units called milliseconds (e.g., latency in ISDN systems is ca. 10 msec). With slower communications pathways, such as slow modems over phone lines, latency may instead be expressed in seconds. There are many ways to reduce latency: better algorithms, wider bandwidth, better transmissions media, more efficient hardware, different topologies, and new technologies. Latency is sometimes intended in a dynamic system where connections change and the topology cannot always be anticipated. A queuing system is a means of using latency to good effect, as in email systems, which will hold messages until the intended recipients or routers along the communications path are available to receive them. Latency may also be used as a signaling system; in other words, delays are taken into consideration and used to convey information. See realtime. Latimer, Lewis Howard (1848-1928) A skilled American drafter and inventor, Latimer worked in some of the most prestigious labs in America. In 1865, Latimer received a Union Navy honorable discharge and became an office boy for a patent soliciting firm. Eager to do more, the ambitious young man self-studied mechanical drawing and convinced his employers to evaluate his drawings. For his efforts, he earned a promotion to drafting work and a dramatic increase in salary. He was later an assistant to Alexander Graham Bell and prepared drawings and descriptions for Bell’s telephone patent. He subsequently received several patents of his own, beginning in 1874. Latimer joined the American Electric Light Company and became a pioneer in the development of the light bulb. He received a patent for an improved electric lamp in 1881, and one for a process for manufacturing carbon filaments which he co-developed with Joseph V. Nichols in 1882. The filament patent was commercially successful, with carbon filaments replacing the short-lived bamboo paper filaments common at the time. In 1884, he

became a member of Thomas A. Edison’s research team. In 1890, he authored Incandescent Electric Lighting: A Practical Description of the Edison System, which became an engineering handbook. He was appointed as an expert witness on the Board of Patent Control of the company that evolved into General Electric (GE) and, in 1918, became a member of the Edison Pioneers.

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The son of a former slave, Latimer had great drafting skills and an inventive mind that earned him professional positions in some of the pre-eminent technology labs of the time. [Image ca. 1882, courtesy of the National Historical Society.]

LATNET A Latvian network service, concentrated mainly in Riga, where most of the scientific community is located. LATNET provides services to the RTD community and some businesses. It is operated by the Department of Computer Science at the University of Latvia in cooperation with the Riga Technical University. LATNET utilizes leased lines and radio links, operating with TCP/IP. lattice model A flow control-related network access security model based upon the lattice format that arises from the ordering of finite security levels within a system. This is usually one of the first models discussed in courses related to security models because lattice-based access control is important for confidentiality and, to some extent, integrity. Latticebased access control models were described by Sandhu in the early 1990s arising out of research in the 1970s (e.g., Denning, 1976). Sandhu’s contributions were based upon work supported by a National Science Foundation grant and a National Security Agency (NSA) contract. launch 1. To start, to set into operation. 2. To start, activate, or begin a computing process, operating system, or application. Programs are launched in a variety of ways, such as double-clicking on icons or

typing the name of the program on a command line. Programs may also be launched automatically from preprogrammed script files, or transparently from within other programs. launch, product In management, to begin a new program, project, or marketing plan, sometimes with a lot of fanfare in order to attract the attention of potential customers and the media. New software packages are often launched at industry trade shows. Law Enforcement Access Field LEAF. In computer security, a section of classified data created in association with a Clipper chip or Capstone, and sent along with the encrypted message. The LEAF includes the session and unit keys concatenated with the sender’s serial number and an authentication string. See Clipper chip. LAWN See local area wireless network and wireless local area network. laws of electric charges Stated simply: bodies with unlike charges will attract one another; bodies with like charges will repel one another; bodies with no charges will neither attract nor repel one another. layer architecture Layer architectures are common in computer networks. Asynchronous transfer mode (ATM) is the most broadly implemented layer network architecture. Defining a number of virtual and physical layers allows communications paths to be organized and administered so that many different developers and manufacturers can create processes and devices independently of one another, yet still apply them to the same system once standards and protocols for the various layers are established. Layers also provide a means to optimize the characteristics of the layer to

the type of processes that occur within that layer. The layer architecture is usually described and diagrammed horizontally, from bottom (physical or lowlevel layers) to top (virtual or user interface and applications layers) with variations depending upon the specific organization of the architecture. Layers typically communicate with adjacent layers directly above or below, or may pass through an intervening layer. The Common Layer Hierarchy chart shows a brief overview of some of the common types of layers. Layer Two Forwarding Protocol L2F. A Cisco Systems Layer 2 application tunneling protocol in the TCP/IP suite introduced in 1996 and submitted to the IETF for consideration as a standard. The advantage of L2F was that it enabled virtual dialup connections with multiple protocols and unregistered IP addresses. L2F uses UDP port 1701. In 1997, Compuserve adapted L2F for establishing securable private networking services for dialup customers. In 1998, Valencia, Littlewood, and Kolar described the protocol as a Historic Request for Comments (RFC). See Layer Two Tunneling Protocol, RFC 2341. Layer Two Tunneling Protocol L2TP. A securable network protocol that extends the Point-to-Point Protocol (PPP) model to enable it to tunnel over Internet Protocol (IP) which, in turn, enables virtual private networks (VPNs) to operate over public packetswitched networks such as the Internet. L2TP can project a PPP network connection to a location other than the point at which the transmission was physically received, enabling multilink operation across distinct physical Network Access Servers (NASs).

Common Layer Hierarchy in Layered Computer Networks Layer

Notes

application layer

A high-level layer at which the user interacts with the network applications programs and utilities. Various types of text or graphical user interfaces may be implemented at this layer. The application may also include remote access mechanisms and information messaging and transfer services.

presentation layer

Data security and data representation during transfer.

session layer

A traffic directing layer that sets up a communication between applications, adjusts synchronization, if needed, and clears the communication when done.

transport layer

A generalized, network-independent means of interlayer communication between the high application-oriented layers and the lower level layers, supporting different types of connections.

network layer

Low-level network connection, routing, and flow-control functions.

link layer

Low-level connectionless or connection-oriented data transfer.

physical layer

Low-level electrical connections and interfaces between the computing platforms and the network cables and connections, and the link layer data transmissions.

L2TP incorporates characteristics of Point-to-Point Tunneling Protocol (PPTP) and Cisco Systems’ Layer Two Forwarding Protocol (L2F) to provide an extensible control environment for the dynamic setup, maintenance, and teardown of multiple Layer 2 tunnels established between logical endpoints in a transmission path. See RFC 2661. Layer Two Tunneling Protocol extensions L2TPext. Extensions to the Layer 2 Tunneling Protocol including links, multicast, etc. The IETF has a working group responsible for the orderly development of extensions to L2TP, in addition to separating out the components of RFC 2661 for greater modularity. The IETF has submitted L2TP over Frame Relay and L2TP Security to the IESG as Proposed Standards. See Layer 2 Tunneling Protocol. LB See leaky bucket. LBA See Logical Block Address. LBS See load-balancing system. LC 1. lead channel. 2. local channel. 3. local company. LCD 1. linear collider detector. 2. See liquid crystal display. LCI International An American telecommunications system providing international voice and data services through owned and leased fiber optic networks. LCI is known as the first long-distance provider to bill both business and residential calls in 1-second increments, a service known under the Exact Billing service mark. LCP See Link Control Protocol. LCS 1. See Lan Channel Station. 2. See Laboratory for Computer Science. LCU Lightweight Computer Unit. LCV See line code violation. LDAP See Lightweight Directory Access Protocol. LDIP See Long Distance Internet Provider. LDMC See Loop Data Maintenance Center. LDMS See Local Multipoint Distribution Service. LDU 1. local distribution utility. 2. See load distribution unit. LE light-emitting. leader 1. The first segment, or part of a transmission or transmissions medium. 2. The first few centimeters on a magnetic tape (audio, video, etc.); the leader attaches and feeds the tape onto the spool. It is not intended for recording, and may be made of nonmagnetic material. 3. A packet, cell, segment, or other leading part of a data transmission, which contains information about data following, without including the data. It is a space or a signal to indicate impending information, rather than being a component of the information itself. See header. leadership priority In an ATM network, an organizational function of a logical node assigning it priority which, in turn, enables it to be designated as the peer group leader (PGL). LEAF See Law Enforcement Access Field. leaf node A type of connecting point in a network, located at the end of a branch, so that only one

connection is between the leaf node and the rest of the network. leakage In electrical circuits, particularly those which are not well shielded, leakage of the electromagnetic radiation outside the boundaries of the physical medium can occur. This may interfere with other transmissions and devices. The Federal Communications Commission (FCC) provides guidelines and regulations for shielding various radio and computer devices in order to minimize interference from leakage. leaking memory See memory leak. leaky bucket LB. A conformance checking cell flow concept in ATM networking related to congestion, an implementation of the Generic Cell Rate Algorithm (GCRA). Think of the bucket as a point in the network where cells may accumulate, depending upon varying rates of inflow and outflow. If cells are entering and leaving in equilibrium, that is, maintaining a sustainable cell rate (SCR), then the bucket will never be filled. If, however, inflow exceeds outflow, as the network experiences congestion, then the bucket may become full. There are various strategies for dealing with a full bucket, although prevention is advised. If, when the bucket becomes full, there are no further incoming cells, then it can be emptied in “bucket depth/SCR rate” amount of time. Bucket depth, the tolerance to cell bursting, can be set in relation to cell flow and retransmission timing. If, however, the incoming cells continue to accumulate, the bucket will overflow and must be handled in some manner, with cell discard as one of the options. There is more than one way to implement a leaky bucket. Cisco Systems, Inc. suggests a means of employing dual leaky buckets, so a preconfigured queue depth threshold is set according to an agreed class of service (CoS) and quality of service (QoS). The first bucket can be configured to provide a service algorithm based on peak cell rate (PCR) and cell delay variation tolerance (CDVT) service parameters. The second bucket is based on sustainable cell rate (SCR) and maximum burst size (MBS). Nonconformant cells can be configured as cell discard, tag, or no change for each bucket. Dual discard thresholds can be supported to provide a delay mechanism for congestion cell discard rates. See cell rate. leased line A line whose use is rented over a period of time from the entity that owns and manages the physical connection. Long-distance companies, specialized services, and businesses with direct private lines often lease lines from the local primary telephone carrier rather than installing their own. Least Cost Routing LCR. A phone service that automatically seeks and selects the line through which to send a call with the least cost. See Automatic Route Selection. LEC 1. See Local Exchange Carrier. 2. LAN Emulation Client. A LAN software client that keeps address translation and connection information for communication through an ATM network. See LANE, LECS. 3. Loop Electronic Coordinator.

L

least significant bit LSB. The LSB is the lowest order bit in a binary value. This is an important concept in computer data storage and programming that applies to the order in which data are organized, stored, or transmitted. As an example, in the binary value 110 (as it is normally written with the larger values to the left), the zero (0) on the right, representing the number of ones, is the least significant bit (LSB) and the one (1) on the left, representing the number of fours (4) is the most significant bit . One of the reasons data are not directly transportable among different systems is that some file formats or operating systems are standardized on LSB priorities and some are standardized on MSB priorities. In other words, some systems code/decode a binary value from smaller to larger (little endian) and some from larger to smaller (big endian). least significant byte LSB. The least significant or lower-order value in a multibyte word. More often than not, a byte represents eight bits. See least significant bit. Leclanché, Georges (1839-1882) A French engineer who invented a type of electrolytic battery cell later refined and used for signal bells and telegraph services. Leclanché received an education in England and then returned to France to continue his studies. In Belgium he was encouraged in his endeavors by Mourlon and established a small laboratory. After developing his dry cell, he opened a factory to produce batteries and electrical devices. Shortly before the death of his father, Leclanché returned to France and, with his own health in decline, made a tour of Europe, Egypt, and other countries to collect Italian furniture. The Leclanché S.A. company of Switzerland, established in 1909, was a pioneer producer of portable lighting, paper capacitors, rechargeable batteries, and other battery-related products. It was associated with other companies in the late 1990s to become the Leclanché Group. See Gassner, Jr., Carl; Leclanché cell. Leclanché cell A historic primary electrolytic cell developed by Georges Leclanché in the mid-1860s. This was an important time in battery history as technology was making the transition from wet to dry cells and from cumbersome hard-to-move batteries to those that were encased and thus more practical and portable. In its original form, the Leclanché battery was encased in a porous pot with a positive manganese dioxide and carbon electrode on the top and a zinc negative electrode on the bottom. The pot and zinc rod were immersed in a solution of [electrolytic] ammonium chloride. The electrolyte penetrated the porous container to reach the cathode. Moulin and Leclanché made commercial improvements to the battery and established a factory to create and distribute the invention. Later, Georges Leclanché’s son, Max-Georges, made some changes to the commercial battery, replacing the porous container. The battery was used in many aspects of the emerging telecommunications industry and as a power source

for bells and automotive lights. The TIS Standard for dry cells and batteries (TIS 96-2528 – 1985) refers to Leclanché-type cells. LECS LAN Emulation Configuration Server. A LAN software server that maintains configuration information that enables network administrators to control which physical LANs are combined to form VLANs. See LEC. LED See light-emitting diode. left-hand circular polarization LHCP. A polarization orientation associated with antennas, for example, satellite antennas. Left-hand refers to a counterclockwise direction. The left or right sense of the polarization is dependant upon various factors, including the transmitter type and transmission frequency. Some systems can be switched from rightto left-hand and may benefit from this flexibility. Left or right orientations are also relevant to other types of polarization besides circular polarization, as in left- or right-hand slant polarization. left-hand rule, Ampère’s rule A handy memory aid, once widely used to determine an axis of rotation or direction of magnetic flow in a current. It originally came from Ampère’s description of a person swimming in the same direction as the current (in a wire). When the swimmer looks left, it’s the same direction that the north-seeking end of a compass will point if it is in the vicinity of the current-carrying wire. Since then, it was decided it was easier to use the left hand and actually look at the thumb and fingers, rather than imagining a swimmer. Extend the thumb and fingers of the left hand so that the fingers are held together and point straight in one direction, with the thumb at a right angle to the fingers, in an “L” shape. Now curl the fingers around a conductive wire, so that the thumb points in the direction of the current. The direction of the curled fingers is said to indicate the direction of the magnetic field associated with the current. Some of the confusion associated with left- and righthand rules stems from the fact that pioneer physicists did not originally know in which direction current was flowing in a circuit between negative and positive terminals. In fact, it was not always important to know, as long as the terms of reference were kept consistent in one direction or the other. Sometimes a distinction is made between current in a motor and current in a generator. By this reasoning, using the left hand, the fingers will show the direction of the current for a conductor in the armature of a motor. Using the same hand relationship for the right hand will show the direction for a conductor in the armature of a generator. Since the universe appears to be right-handed in its general orientation, some physicists will assert that it makes sense to use the right-hand rule. See right-hand rule. leg 1. A portion of a trip, broadcast, or transmission. 2. The transmission segment in a network between two physically distinct entities (such as a workstation, switch, router, node, etc.), between addressable entities, or a combination of the two. legacy That which is inherited, or which remains from a predecessor.

legacy equipment/software Existing equipment, software, or operating procedures that are becoming dated but are still actively used are called legacy systems. For economic reasons, most legacy systems are maintained and enhanced, rather than scrapped in favor of new systems. Even when it’s not economically practical, legacies are sometimes retained because managers are reluctant to let go of the emotional investment tied up in existing systems and procedures. A more practical reason for retaining legacy systems is that staff training costs time and money, and staff members may be reluctant to switch to a new system. Most computer operating systems are legacy systems, incorporating downward compatibility in order to work with older equipment. Legacy to the Future L2F. A framework for providing an integrated modeling system of legacy and new code components to support simulations in the Los Alamos National Laboratory (LANL). L2F is implemented using JAVA and CORBA to facilitate communication among objects written in different languages. The system includes a setup server and an associated database, application servers, clients and optional security services. L2F has been cleared for open source distribution. Lempel-Ziv LZ. A pair of coding compression formats described in IEEE articles “Compression of Individual Sequences via Variable-Rate Coding,” in 1977 (LZ77), and “A Universal Algorithm for Sequential Data Compression,” in 1978 (LZ78). They are named after their developers Abraham Lempel and Jakob Ziv. LZ77 was presented by Ziv and Lempel as a dictionary-based scheme for lossless data (text) compression. LZ78 sends pairs of pointer and character data. These two important schemes are so universal and powerful that a significant number of data compressors have been based on Lempel-Ziv concepts. LZ77 became the basis for LArc, LZARI, LHarc, and others. Lempel-Ziv schemes have been widely adapted and used in network and modem technologies, but the early versions were not developed for the demands of multimedia networks with widely ranging data characteristics (which scarcely existed at the time). Another limitation of the original Lempel-Ziv techniques was in performing efficient searches for previous matching strings. Enhancements and variations are addressing some of these limitations and adaptations to special circumstances. In 1994, Jung and Burleson proposed a parallel algorithm, architecture, and implementation for Lempel-Ziv compression exhibiting a scalable, regular structure suitable for VLSI array implementation. This has practical applications for data compression in portable digital data communications and wireless local area networks (LANs) where effective compression/decompression schemes can significantly improve throughput and reduce connection time costs. See Ardire-Stratigakis-Hayduk, differential Ziv-Lempel, LArc, LHarc. Lempel-Ziv-Stac LZS. A data compression system developed by Stac Electronics, Inc., largely based

upon the LZSS algorithm. See Lempel-Ziv-StorerSzymanski. Lempel-Ziv-Storer-Szymanski LZSS. A sliding dictionary compression scheme descended from LZ77 by Lempel and Ziv. LZSS was developed in the early 1980s by James Storer and Thomas Szymanski. Storer filed for a patent for data compression/decompression in 1987 (U.S. #4,876,541). LZSS differs from its predecessor mainly by using bit flags to identify the subsequent data as a literal or an offset, which can result in more compact data compression and faster decompression. A number of developers developed variations and optimized versions of LZSS, one of which evolved into LArc. See LArc. Lempel-Ziv-Welch LZW. A dynamic dictionary, lossless data file compression scheme based on the Lempel-Ziv method, first described by Terry A. Welch in 1984 following the publication of the Lempel-Ziv format in the late 1970s. The developer community generated a substantial amount of debate over use of LZW, since it was distributed as an open standard for many years before the community at large was informed that LZW was being patented. Many programmers incorporated LZW into their software, thinking it was in the public domain. LZW has been incorporated into ARC and PKZIP. PKZIP is a particularly widespread archiving utility. A patent for the technology is held by IBM (U.S. #4,814,746), with a similar one held and enforced by Unisys Corporation (U.S. #4,558,302). Some claim these two patents cover virtually the same technology, or that the Unisys patent is a subset of the IBM technology. A similar patent has also been held since 1989 by British Telecom. The enforcement of the patent rights caused ripples of unease in the programming community, as several modem file protocols use LZW. Many graphics interchange formats incorporate LZW compression, including TIFF, which is widely used in desktop publishing programs, and the Compuserve 8-bit GIF format popular on the Web. In telephone technology, LZW is used in Northern Telecom’s Distributed Processing Peripheral (DPP) for the transmission of compressed data. At one point, Unisys issued a statement exempting freeware authors from paying license fees on the use of LZW in their programs in order to quiet the concerns of software developers who were distributing software without commercial gain. Later, Unisys asserted that all software developers would be subject to a minimum royalty ($.10) in order to protect the patent, with exceptions only for charitable institutions. See Ardire-Stratigakis-Hayduk, Lempel-Ziv, LZC. LEO See low Earth orbit. LES LAN Emulation Server. A local area network (LAN) software server which provides Media Access Control (MAC) address-to-ATM address resolution services for LAN Emulation (LANE). See LECS, LEC. less than A concept often represented symbolically (e.g., ). While its most obvious use is comparing numeric values, it is also sometimes used for text parsing comparisons, with the comparison based on total ASCII value, or the length of the text word or some other predetermined comparison function. letterboxing A video display technique that preserves the aspect ratio of a wide screen cinematic production even when it is displayed on a different system such as a TV screen. Wide screen movies are often modified to fit a TV screen ratio, but then information on either side of the image is lost. In letterboxing, it may appear as if some of the image is gone, because there are larger black areas at the top and bottom of the image, but in fact, it is the letterboxed version that shows the entire image and retains the fidelity of the original picture. The difference can be quite dramatic. For example, in a number of scenes in the beautiful film Baraka, the nonletterboxed version shows only two people rather than the original three. See aspect ratio. letters shift A simple mechanical device on a typewriter or teletypewriter, which puts the machine into the mode for printing letters of the alphabet, or for shifting between upper- and lowercase letters on those devices which include both. level 1 cache A small, fast static RAM buffer. On an Intel Pentium central processing unit (CPU) chip, a 16-kilobyte cache memory is incorporated into the chip. level 2 cache An external, fast, static RAM buffer. On an Intel Pentium central processing unit (CPU) chip, a cache memory is incorporated into the processor in addition to the level 1 cache included with the CPU. On some of the Pentium chips, the level 2 cache is layered into the CPU (for faster access), and in some, it is a separate section, with a bus allowing it to communicate with the CPU. Level 2 caches may vary in size from 256 kilobytes to 1 MByte. Leyden jar, Leiden jar A device that concentrates and stores electrical energy, thus serving as an electrical condenser; an early capacitor. The Leyden jar was devised by E.G. von Kleist, a German experimenter, in 1745. It consisted of a nail in a bottle connected to a terminal of an electrical device, with the jar held in von Kleist’s hand; he received an unpleasant shock from his experiment. A year later, Cunaeus and Peiter van Musschenbroek created a condenser consisting of a jar mostly coated inside and out with metal foil, with the inner coating in contact with a conducting rod that passed through the stopper (insulator). The foil would typically cover about two-thirds or a little more of the surface of the jar, and the rod would be inserted through a stopper of cork or rubber. Sometimes a chain was attached to the bottom end of the metal rod. The jar was named after the town of Leyden (Leiden) in The Netherlands. It was subsequently discovered that a Leyden jar charge could be sent through wires over distance. Benjamin Franklin conducted numerous experiments with Leyden jars in his attic laboratory, and they remained

prevalent for another 150 years.

conducting rod insulating stopper

insulating container wire or chain from rod to bottom metal surface thin metal coating inside and out

The Leyden jar was an important historic storage tank for electrical experimentation, acting as an electrical condenser/capacitor. [American Radio Museum collection.]

LF See line feed. LFACS See Loop Facility Assignment and Control System. LFAP See Light-weight Flow Admission Protocol. LGC Line Group Controller. LGRS Local Government Radio Service. LHA A lossless compression scheme developed by Yoshizaki. In terms of compression performance for text files, LHA was an improvement over the original LZ77 by Lempel and Ziv, through static Huffman coding, but not as efficient as the popular GZIP. It is also known as LZH due to shared .lzh/.lha file extensions. LHarc also uses .lzh file extensions, so there may be some confusion, but they are from the same family of compression utilities and somewhat downwardly compatible. LHA has been widely used in Japan and is a popular utility on the Amiga computer. See LHArc, LZHUF. LHarc A fast, efficient dictionary-style compression/ archiving utility descended from LZSS. LZSS was developed into LArc by Okumura and Miki in the late 1980s. Okumura then created LZARI, which incorporated adaptive arithmetic compression, from LZSS. Yoshizaki subsequently modified LZARI with adaptive Huffman coding instead of adaptive arithmetic coding to create LZHUF, which was then rewritten in assembler with an updated interface to create LHarc, which was fast and popular. LHarc is a full archiving utility, allowing multiple

files to be stored, listed, added to, or removed from a single archive. LHarc was especially popular on the Amiga, edging out earlier favorites due to its speed and versatility; there are versions for IBM-licensed PCs, Macs, Ataris, and Unix machines as well. See Lempel-Ziv, RAR. LHCP See left-hand circular polarization. LIC See light-guide interconnect cable. Licklider, J.C.R. “Lick” (1915-1990) A computing pioneer who was instrumental in supporting a number of important early developments, including timesharing and the ARPANET. He is best remembered for his inspiration and enthusiasm, and his ability to get the funding and other resources necessary for various computer pioneers to build the stuff of dreams. LIDB See Line Identification/Information Database. life cycle A period of time describing a product or service cycle, such as the design and development process or the entire lifespan from product development through successful sales, to final loss of demand for the product. See shelf life. life cycle testing The testing cycle of a product from initial testing to product failure. In industrial test environments, products are often exposed to extreme conditions of use or environment in order to determine a baseline life cycle expectancy to estimate what length or type of normal use can be expected from the product. See mean time before failure. LIFO last in, first out. A descriptive term for the order in which data are processed in a queue. For example, picture a stack of dinner plates in a plate well in a buffet; when the stack is refilled by the restaurant staff, the last plate on the stack (the one on top) is the first one removed by the next customer. Data can be handled in the same way. See FIFO, FILO, GIGO, LILO. ligature In typography, when setting text, there are instances when two letters placed together will “collide,” that is, slightly overlap in a way that is unaesthetic, or will leave a gap, thus detracting from the visual appeal of the composition. In these cases, the typographer may use a ligature, a combination of two (or more) letters in which the physical elements of the letters are joined to provide a more appealing or more legible rendition of the combination. light Radiant energy visible to the human eye having wavelengths in the approximate range of 390 to 750 nm, that is, the transition to ultraviolet at one end of the spectrum and infrared at the other end. The phrase white light is used to describe light with a mixture of frequencies. The speed of unimpeded light is 3.00 x 10-8 meters per second, symbolized as c in mathematical calculations. It was discovered that light could be broken up into its component wavelengths with prisms, and this aided researchers in understanding the nature of light and the colors associated with particular frequency ranges. The visible spectrum is specific to human perception; other mammals and insects have broader, shifted, or more specific perception of color ranges. A flower that to humans appears yellow may have

other colors in the ultraviolet or infrared spectrum that are perceived by pollinating insects. Most dogs and cats are insensitive to colors as humans perceive them (Siamese cats reportedly can perceive color).

On the left, the dot on the “i” collides with the ascender on the “f.” Combined as a ligature on the right, the “f” and the “i” have been incorporated into one letter, with more aesthetic contours. Ligatures are typically found in high-quality, hand-crafted character sets used in desktop publishing.

Light is the primary means by which sighted individuals sense forms, beings, and their orientation and movement in three-dimensional space. The interaction of the light waves hitting various objects, bouncing back through eyes and processed by brains, constitutes the complex phenomenon called sight. Some creatures can see beyond the range of humanly visible light. Dolphins use sonar (sound waves) to detect objects which may not be visible to humans, and thus can “see” inside some objects in a way not possible for humans without mechanical aids. See fiber optic, infrared, lamp, laser, spectrum, ultraviolet. light guide Light-conducting material such as an optical fiber. The material provides a conduit or channel by which the light can be directed. The idea is similar to the concept of wave guide. light pen A hardware human interface device that translates hand and finger movements into electrical impulses and transmits them to a computing device. These signals are then interpreted into processes by the operating system and applications software. The light pen resembles a ball point pen with a light detector on the end where the ink would normally come out of a ballpoint pen, and a “tail” on the other end, connected to a computer or handheld console. It may or may not include one or more small buttons. On raster displays, the pen detects light on the screen in order for the application to determine the position of the pen. See joystick, mouse, trackball. light piping Bringing light into an area through fiber optic cables. Laser light will travel along a filament the size of a hair, and filaments can be bundled to provide more light. This is very handy for illuminating hard-to-reach places like small pipes or inside the human body for medical research or procedures. light-emitting diode LED. An inexpensive semiconductor pn junction structure used in many electronic displays, particularly small ones. The LED lights up when a current is provided. LEDs are common in digital clocks, calculators, microwave readouts, electronic instrument displays, and much more. The LED typically resembles a small illuminated knob with a semiconductor within the knob (which is actually a lens), and leads coming out from the semiconductor/knob arrangement into the device circuitry.

L

LEDs are now also used to provide the light rays for certain types of fiber optic transmissions, especially in multimode cables (more precise and more expensive laser lights are used for single mode fiber). light-guide interconnect cable LIC. Also called light-guide cable interconnect (LCI). A light-guide is a conduit for directing and containing a light-based transmission and an interconnect cable is one which specifically interconnects various equipment and devices. LICS are used in fiber optics transmission networks and typically have connection ends that can be more readily connected and disconnected for the purposes of installing and reconfiguration network physical topologies. See loose cable. Light-weight Flow Admission Protocol LFAP. A protocol from Cabletron which allows an external Flow Admission Service (FAS) to manage flow admission at the network switch, allowing flexible FAS to be used by a vendor or user without unduly burdening the switch. See RFC 2124. LightSAR light synthetic aperture radar. See synthetic aperture radar. lightwave communications Optical communications systems using high frequencies. This term helps distinguish optical communications from very short wave microwave communications. Fiber optic cables are used as the physical medium for transmission. This is distinct from lightwave transmissions, which involve transmission through air or space rather than through a cable as the physical medium. When homodyne or heterodyne detection schemes are used, they are called coherent optical communications systems. lightwave transmission Optical communications systems based on transmitting a beam through air or space, without using a cable as a physical medium. This is a wide bandwidth, line-of-sight, short distance technology which is relatively inexpensive. It is suitable for building-to-building installations where it is impractical to string wires. This system is subject to loss and is somewhat dependent on weather, and thus specialized in its practical applications. Lightweight Directory Access Protocol LDAP. A front-end client/server standard intended to provide a lightweight complement to Directory Access Protocol (DAP), LDAP is based somewhat on ITU-T X.500 and can access X.500 directories. It is a distributed, hierarchical protocol for accessing network entities and repositories and is more scalable for some implementations than, for example, Network Information Services (NIS). LDAP was developed in the early 1990s at the University of Michigan and submitted as a joint Standards Track RFC with the ISODE Consortium and Performance Systems International. In LDAP, the protocol elements bypass some of the session/presentation overhead by going directly over Transmission Control Protocol (TCP) or the relevant transport protocol. Many of the protocol data elements are simply encoded as strings. A lightweight best error rate (BER) encoding is used for protocol elements. Extensions to the format such as authenti-

cation and server discovery are being discussed and developed. See RFC 1777. LightWeight Encoding Rules LWER. LWER comprise one of three major encoding schemes used in open architecture development, developed in the early 1990s. LWER provide a means for creating encodings optimized for encoding and decoding CPU cycles and apply better to wide bandwidth communications between similar architectures than to slower mixed-system networks. See Basic Encoding Rules, Packed Encoding Rules. like new A subjective term describing a product that has been opened and stored or used, but is physically unmarred and functionally in good working order. The phrase is not intended to imply that the product will last as long as a brand new product in normal use, hence the phrase like new instead of new. See certified, refurbished, used. LIM Link Interface Module. LINC Laboratory Instruments Computer. One of the earliest small computers, developed at the Massachusetts Institute of Technology (MIT) in 1963, the LINC was the inspiration for Digital Equipment Corporation’s (DEC’s) PDP-8. line code violation LCV. In E1/T1 networks, an indicator of bipolar violations (BPVs) or excessive zero (EXZ) errors. A line err second (LES) is a second time duration in which one or more LCVs are detected. A severely err second (SES) is one in which serious defects are detected such as 2048 LCVs or more for nonCRC signals. line err second LES. See line code violation. line of bearing LOB. In radio direction-finding systems, the direction and general position of a target or positional goal. A radio direction-finder is a device for tracking down the source of a radio frequency signal. Flashing lights or beeps are sometimes used on portable systems to indicate the direction or proximity of a target (e.g., wildlife with a radio collar). In mounted systems, a monitor may indicate a line of bearing relative to a selected reference point. Most direction-finding devices will have a certain margin of error, expressed in degrees, that can be used to calculate the region of error of a bearing over distance. Lines of bearing are sometimes graphically plotted by hand on a chart or map. A line of bearing is sometimes a calculated position based on a series of readings within a general range. In direction-finding, intersecting lines of bearing may indicate the position of a transmitter at or near the intersecting point. Consumer systems for determining lines of bearing are more sophisticated compared to the old handheld beeping antennas prevalent for many years. It is now possible to use a Global Positioning System device with an automatically adjusting antenna to carry out direction-finding and transmitter tracking functions. line speed The maximum or actual speed of data transmission through a wire or cable. There are dramatic variances in line speeds depending upon the type of cable, the distance or character of the path, and the interface or modulation devices used to convert or send/receive the data.

Line speed for digital data transmissions is commonly expressed in terms of the number of bits or characters transmitted per unit of time (usually seconds). For comparison, a typical 64K ISDN connection to a page on the World Wide Web might download an average-sized image at 7500 cps. Many factors can reduce the line speed from its theoretical maximum, but ISDN and cable modem throughputs are significantly slower than 10M Ethernet, for example, which could download the same data at speeds of up to about 480,000 cps. line trunk controller LTC. A telecommunications trunk controller that provides a means to use equipment contained within a central office. The LTC is capable of giving interfaces to outside ports; it is one of a number of peripheral modules that can provide trunk interfaces to a digital multiplex system (DMS). It may interface with multiple lines which, in turn, may be linked to a network by multiple speech links. line utilization monitor LUM. A diagnostic and administrative utility providing statistical logs or displays of transmission line use. line switching unit LSU. A generic phrase for a variety of devices that range from simple passive switchers to complex active voice or data transmission line switchers. A line switching unit can be used on a single computer or local area network (LAN) to switch between multiple peripheral devices such as printers and scanners or, in a more sophisticated architecture, between a disabled system and a standby system. In telephony, line switching units are typically floor-size cabinets with multiple lines and electronic switching circuits to manage those lines and their connections. LSUs may be manual or automatic. Automatic units are more likely to be used in remote locations or for backup or emergency systems triggered by alarms or fault conditions. linear modulation A modulation scheme developed at Bristol University in 1991. The technology began to be used in the U.S. in the mid-1990s. The advantage of linear modulation is that it enables voice and data transmissions to be carried over narrow channels (e.g., 5 kHz), thus making it possible to increase capacity up to five times that of traditionally wider frequency-modulated (FM) channels. A pilot tone is inserted into the audio baseband, essentially splitting the band, enabling linear modulation to be achieved without distorting the signal. The development of new modulation schemes that can support higher capacities and bit-rate densities has become particularly important in recent years. The demand for mobile services is growing, while the pool of available frequencies remains essentially the same. To complicate the picture further, the Federal Communications Commission (FCC) has issued a requirement that spectral efficiency for mobile devices be improved by the year 2005. Linear modulation is seen as one of the key technologies that may aid developers in meeting this requirement. See tone in band. linear predictive coding LPC. A system for digitally encoding speech at low bit rates while retaining good clarity and recognition without extensive computing

overhead. In LPC, speech signals are analyzed as to various common aspects, including resonance, intensity, pitch, etc. Formants (resonances or boosted frequencies) are filtered and stored in addition to the remaining signal, which is termed the residue. Portions of the speech are sampled at the rate of about 40 frames per second, resulting in manageable file sizes for storage and intelligible speech when the encoded data is reconstructed. In the encoding/decoding process, estimates are used and errors between a predicted signal (based on previous samples) and an actual signal are minimized for the series of sequential samples. LPC methods result in lower information bit rates than adaptive predictive coding (APC) methods. Since speech and music share many common aspects, LPC has been useful for computer music encoding for storing and extracting time-varying formant information. LPC concepts have also been applied to the compression of imagery in that predictive techniques have been used to provide linear approximations of vector information which, in turn, can be used for lossless or lossy compression algorithms for geospatial imagery. See sampling. linear programming Algorithmic symbols, procedures, and strategies in which a problem or statement can be expressed in a standard form within certain variable, sign, and coefficient constraints to find a solution to a problem. Both the program constraints and the problem itself are linear. While a limited form, many types of problems can be solved or expressed with this type of programming environment. Variables within a linear programming problem can be seen as corresponding to decision factors in the problem to be solved. Linear programming is useful for solving or generating optional optimization solutions for production lines, transmission paths, or investment or management scenarios. linear search & track processor LSTP. A system for processing radar search and track signal data. The Naval Research Laboratory Collaboration has been porting LSTP functionality to parallel computing platforms. linear tape-open LTO. A tape storage technology developed jointly by Hewlett-Packard, IBM, and Seagate. LTO is an open format that incorporates linear multichannel, bidirectional tape formats with data processing enhancements such as error checking, data compression, etc. In spite of the many storage options available for data management that rely on optical or hard disk formats, there are still advantages to the use of tape, including high capacity and low cost. Hundreds of GBytes can be stored on a single tape cartridge in compressed format. The LTO technology has been optimized into two open tape versions specified as fast access or high capacity. This decision was based on the observation that some storage needs are read-intensive (requiring speed of access) and some are write-intensive (requiring high capacity). The formats are respectively called Accelis and Ultrium. Licenses for third-party developers were made available as of April 1998.

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Commercial implementations vary, but transfer rates of 30 Mbps are available. IBM offers low voltage differential (LVD) and high voltage differential (HVD) versions for SCSI and Fibre Channel (FC). Quantum’s Super DLTtape technology is somewhat competitive with LTO. See Super DLTtape. line, communications In its most general sense, any path or transmissions link between two or more communicators, including any subscriber line, switches, routers, cables, etc. which might comprise the main transmissions pathway. The term line usually implies a physical connection, or series of physical connections including wire or fiber optic cable. Hybrid systems including wired and wireless connections are sometimes also called lines. Complete wireless connections are usually referred to in terms of airways rather than lines. line, electric A circuit connection physical conductor consisting of shielded or unshielded wire or cable. line, graphic In computer graphics displays, and paint and drawing programs, a visual representation of a narrow, connected path. Line tools are very common drawing tools that can be used to draw straight disconnected lines, straight connected lines, and curved lines using various freehand drawing or curve algorithms (spline curves are common in vector drawing programs). line conditioning Improvements and enhancements to a communications line to reduce interference and improve the quality of the signal. Some phone companies offer higher quality line service as an option, which may be important to those doing a lot of data communications over a phone line. line feed In the context of computers, a line feed refers to a movement of a cursor or printer carriage to the subsequent line. In western languages, the subsequent line is down from the previous line. (There are languages that read from bottom to top but, unfortunately, they are not well supported by the software on most computer systems.) Line feed does not normally imply a return of the carriage to the start position at the margin (or the beginning of the line on a computer display), although even here some systems make an exception. The return of the carriage is known as a carriage return. On some systems, a carriage return or enter key includes a line feed, and on some it does not. From a programming point of view, it’s better to differentiate the line feed and carriage return as separate actions so they can be used separately and together in various combinations as needed. In ASCII, character 10 is designated as the line feed. line finder An evolutionary improvement in step-bystep telephone switching systems that eliminated the need for a separate switch selection for each subscriber line. When the caller picked up the phone, a dial tone was needed before dialing could begin. To accomplish this, a relay would be used to find an available line-finder switch, hunting for the caller’s terminal would be initiated, and the caller would be given a dial tone when the line was connected with the switching system.

Line Identification/Information Database LID. A national system of telecommunications information databases first deployed in the early 1990s. It is designed so that subscriber and carrier information can be readily accessed and cross-referenced. This information is used for information-querying, validation, and alternate billing administration. See Local Number Portability. line impedance stabilization network LISN. A diagnostic instrument for measuring emissions, a LISN stabilizes the line impedance so that tests can be repeated against a reference at more than point. This enables the device being tested to be isolated from an external power source, for example. There are a variety of types of LISNs with low-pass or high-pass filters, depending upon their purpose. LISNs have connectors for attaching the device being tested and may also have a connection for additional diagnostic equipment or displays, such as a spectrum analyzer or electromagnetic interference (EMI) meter. They are designed to test within specific frequency ranges (e.g., 10 kHz to 30 MHz). LISNs are commonly used to see if devices are generating signals (radio frequency interference) that may affect their operation or nearby devices. They are also used to determine whether the emissions are above certain maximum levels established as industry standards (e.g., ANSI) or in conformance with levels established by regulating bodies such as the Federal Communications Commission (FCC). Electromagnetic disturbance characteristics and standards are encompassed within CISPR 11 to CISPR 28. CISPR 16, in particular, specifies radio interference measuring apparatus and measurement methods pertinent to LISNs. Multiline ISNS are also known as V-Networks. See International Special Committee on Radio Interference. line insulation test LIT. In telephony, a diagnostic test performed from the central office to determine line resistance and line voltages. line noise Electrical noise in a communications line which interferes with voice communications, or which causes spurious characters to show up in a data transmission. In older modems used over phone lines, line noise sometimes resulted in strange characters being displayed in the telecommunications software terminal window. Severe line noise can interrupt a data file transfer, or even cause the connection to be disconnected. With newer phone line services and newer, error-correcting modems, this problem is diminishing. line of sight Many means of communications require an unobstructed straight line of travel for the information to reach the intended destination or to be seen by the appropriate people. Semaphore systems require that the signal arms or flags be visible. Beamed light requires that no impediments block the way or bounce the beam in a direction away from the recipient. Line of sight thus refers to a straight, clear, direct, and otherwise unobstructed travel path. line powered Any device that receives its power from the main system or transmissions medium to

which it is attached. For example, most basic phones without extra features do not require a power supply or battery because they are powered by the current in the phone line. Some laptop peripheral devices, to minimize size and weight, derive their power from the laptop itself. See talk battery. line printer A printing device that prints one line of characters, or a full line at a time. This phrase is used rather generically to mean most impact printers that print a line of characters at a time, though, technically, these are actually character printers. True line printers compose and “stamp” an entire line of text (they’re quite fast and often very noisy), and then compose and impress the next line, composing in the printer memory buffer while the current line is being printed. Line printers tend to be used in institutional and industrial environments where speed is more important than cost or level of quiet. line status indicator On a telephone, modem, or other appliance that can connect to more than one line at a time or perform a variety of functions on one or more lines, there may be a character display or various lights to inform the user of the status of the line. On multiline telephones, a light usually shows which lines are in use so that the user can avoid barging in on a call inadvertently. On a modem, line status indicators may flash to show whether data are sent or received, and may indicate whether or not a carrier is present. On network ports, status indicators may indicate loss of frame (LOF) or loss of signal (LOS). line switching See circuit switching. Line Terminating Equipment LTE. In SONET networks, an element that originates and/or terminates a line signal. It can originate, access, or modify the line overhead, or terminate it, if needed. See SONET, Synchronous Transport Signal. line tool In image processing programs, a tool that enables straight or curved, joined or separate lines to be drawn. Most paint programs permit the type of line, its thickness, and sometimes its style to be varied according to a number of parameters. line weight In typography, image processing programs, and vector drawing programs, line weight is a setting to control the thickness of a line, sometimes in very precise units such as points. In fonts, the line weight can be varied to produce various types of medium, bold, and extra bold effects. linear transponder A device commonly used in communications satellites and radio relay stations, which takes a small segment of frequencies, amplifies the signal strength across the range of frequencies, and retransmits them at a slightly different frequency range (by shifting or multiplying), so that the whole segment is adjusted up or down. This is often done to prevent the transmitted signals from interfering with the received signals. See store and forward repeaters. lineman, line worker In the early days of the telegraph, when cable was being strung across continents, linemen were assigned to dig holes, cut down trees for poles, set the poles, climb them, and attach

the wires, gradually working their way through wilderness, native encampments, and mountain ranges, until the coasts and settlements were interconnected. Once the lines were installed, they would test them, often with portable telegraph keys, and maintain the lines through inclement weather over hostile terrain. The work was hazardous, no insurance or benefits were available, and linemen injured by electrocution, falls, and other hazards were dependent on the goodwill of their employers for assistance. Maintaining the increasing number of wires and poles involved the dedication of many 24-hour crews and, until the mid-1960s in North America, much of the work was done by climbing the poles with belts and cleated boots (lineman’s climbers), securing in at the point that needed repair, and doing the work manually with simple tools. Since that time, power tools, sophisticated testing equipment, and cranes with buckets (cherry pickers) for the line workers have increased in use to the point that it is uncommon to see a worker scale a pole in urban centers. The line workers now are also responsible for digging, diagnosing, and installing underground transmissions lines, in addition to managing lines on utility poles. lineman’s climbers, line climbers A variety of pole climbing equipment used over the last century to allow installation and repair workers to scale utility poles in various types of weather. These range from climbing irons or spurs strapped on the legs, to cleats on the boots, used in conjunction with a heavy hip belt (sometimes called a “scare strap”) that helped the line worker stay secured and oriented to the pole at a comfortable angle. In urban areas, line climbers have mostly been superseded by mechanized cranes, sometimes called “cherry pickers,” although climbers are still needed in some circumstances, especially in areas of rough terrain. See lineman. lines of force, lines of magnetic induction The sphere of magnetic influence of a magnet. For example, in a basic bar magnet, the lines of force can be conceptualized as radiating outward from the poles with no break between the north and south poles. Although diagrams of magnetic lines of force show them as discrete lines in one plane, the actual region of influence is three-dimensional. The lines themselves are a descriptive way of conveying the properties of the forces that cause them to crowd each other sideways. Areas where these lines converge, as at the poles, indicate areas of stronger magnetic force. The direction of the lines can be defined as the direction along the north pole if forces other than the magnetic force were hypothetically neutral. Lines of force can be observed indirectly by sprinkling iron particles over a bar magnet and tapping the surface until they form patterns around the magnet. The lines are not fixed in one position; they will change if you sprinkle the filings again, but come about through their interaction, as each piece behaves as a tiny magnet, alternately attracting and repelling near neighbors. Collectively these lines are classed as flux. See flux, magnetic field.

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Iron filings sprinkled around a magnet on a lightcolored surface or piece of glass will reveal particular types of patterns like those shown in this diagram, depending upon the shape of the magnet. These patterns will change each time the filings are sprinkled, since they are formed not because there are lines emanating from the magnet, but because the magnetic forces associated with the magnet cause the particles to interact with the magnet and one another in specific ways.

Lines of force are related to the shape and orientation of the objects with which they are associated, and the current flowing through those objects, in the case of electromagnets. Above are some examples of lines of force associated with different structures.

lines per minute LPM. A description of the speed of a recording device such as a line printer, inkjet printer, or teletype-style machine. These devices are sometimes also described in terms of printing speeds of characters per second (cps). The printing speed is not an absolute measure. A printer cannot transcribe the information any faster than it receives it. However, since the bottleneck is more often the printer than the transmission speed, many printers have memory buffers to store incoming information until the printer catches up. link n. 1. In its broadest sense, a communications circuit or channel. 2. A specific leg in a circuit, as between two nodes, two networks, or two users. In ATM, it is more specifically defined as a logical link, that is, an entity with a specific topological relationship and transport capacity between two specified nodes in different subnetworks. See Ethernet, Frame Relay, asynchronous transfer mode, tunneling. 3. A communications medium over which nodes can

communicate at the link layer. 4. A logical link between software entities, files, or processes, as between an icon and an executable program, or between an alias and a file directory. See alias. link v. 1. To form a logical relationship between software entities, or software and hardware devices. 2. To interconnect hardware devices and/or cables. 3. In software development, while building executable files, to link the compiling source code into appropriate system resources, headers, or other system software specified. link access protocol LAP. A generic category of protocols for establishing (setting up) data transmission connections across a wide variety of devices. As the name implies, LAP operates at a lower level called the link level, which is Level 2 in many common networking architectures. LAP is one of several protocols functioning at the link level to establish, control, and take down network links. In frame-based networks, balanced LAPs are more commonly used now than the earlier basic LAPs. However, there are many different implementations of LAPs for device connections including computers, modems, infrared remotes, etc. from different manufacturers. Link Access Protocol Manager LAP Manager. A set of software utilities providing a standard interface between high-level protocols and link-access protocols for AppleTalk Link Access Protocol. LAP Manager enables a user to select among AppleTalk connection files to specify a network to be used for the node’s AppleTalk connection. When a connection is selected, the LAP Manager routes the communications through the selected link-access protocol and its associated hardware, thus acting as a switching mechanism. See Link Access Protocol, Link Control Protocol. link aggregation token See aggregation token. link attribute In ATM networks, a parameter used to assess a network link state, to determine whether it is a viable choice for carrying a given connection. link connection In ATM networks, a connection which can be used to transmit information without the addition of any overhead. link constraint In ATM networks, a restriction applied to the use of a specific link. In other words, restrictions as to whether it may be used as the path for a connection. Link Control Protocol LCP. In order to support a variety of environments, Point-to-Point Protocol (PPP) provides a Link Control Protocol (LCP). When network link access has been initiated, the LCP agrees upon encapsulation format options, handles varying limits on packet sizes, detects common misconfiguration errors, and terminates a link. The main phases for establishing, configuring, maintaining, and terminating a link are shown in the Link Control Procedures chart. The Link Control Protocol packet is encapsulated within the information field of a Point-to-Point Protocol data link layer frame. In brief, the packet is configured as shown in the Link Control Protocol Packet Format diagram. See Compression Control

Protocol, link access protocol, Point-to-Point Protocol, SNA Control Protocol, RFC 1171, RFC 1661. Link Control Protocol codes LCP codes. These link-establishment packets are used to establish and configure network links. Link Control Packets are assigned as follows: Code

Control code assignment

Code 1 Code 2 Code 3 Code 4 Code 5 Code 6 Code 7 Code 8 Code 9 Code 10 Code 11

Configure-Request Configure-ACK Configure-NAK Configure-Reject Terminate-Request Terminate-ACK Code-Reject Protocol-Reject Echo-Request Echo-Reply Discard-Request

See Link Control Protocol, Point-to-Point Protocol. link encryption An internetwork security mechanism which, unlike an authentication header (AH), affords some protection from traffic analysis. link MTU A unit describing the maximum packet

size which can be conveyed in one piece over a communications link. Linux A popular, well-supported, widely implemented, freely distributable, open source Unix-like operating system developed in the early 1990s by Linus B. Torvalds in Helsinki, Finland (he has since moved to California). Torvald has been honored for his contributions to information and telecommunications technology. Linux is mostly POSIX compliant, and features true 32- or 64-bit multitasking, virtual memory, TCP/IP drivers, shared libraries, protected mode execution, and more. Linux supports the X Windows system, conforming to the X/Open standard. It also supports the common Internet protocols, including POP, IRC, NFS, Telnet, WAIS, Kerberos, and many more, as a client or a server. Popular Unix shells work with Linux. Some excellent applications have been ported to Linux, with more being developed all the time. Linux has been ported to many platforms, including PowerPC, Amiga, Macintosh, Intel-based machines, Atari, and others. There are a number of commercially available versions of Linux, including Stac and Red Hat and it is a very popular choice for local area network (LAN) and Internet servers. It is reliable, powerful, and is being adopted by many large-scale research and development firms. The Linux Journal is a good trade magazine for Linux developers and users.

Link Control Protocol Packet Format 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 bits +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Code | Identifier | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data ... +-+-+-+-+

Link Control Procedures Phase

Events

Notes

Phase 1

Establishment and configuration

Configuration packets are exchanged, a Configure-ACK packet sent and received, and the Open state entered.

Phase 2

Link quality determination

An optional phase in which the link is tested for quality.

Phase 3

Network layer protocol configuration

Upon completing optional link quality determination, network layer protocols can be configured and maintained or taken down.

Phase 4

Link termination

The link may be terminated at any time, usually at a user’s request, but possibly also because of a physical event.

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Linux International An international organization of developers, vendors, and users of the Linux Operating System and its associated programs. http://www.li.org/ Linux Terminal Server Project LTSP. An opensource project under the GNU Public License to create administration tools to facilitate the setup of Linux network diskless workstations. The motivation for the project was to provide a flexible, reliable, low-maintenance, cost-effective network setup for remote computing workstations. liquid crystal display LCD. A low power display technology comprising a number of layers, one of which is made of liquid crystal, sandwiched together. The long crystalline molecules in the liquid crystal layer are used to deflect and polarize light. When exposed to an electric field, the crystals orient themselves in the same direction, no polarization occurs, and the light is absorbed; the display remains dark. Liquid crystal displays were originally developed by RCA’s David Sarnoff Research Center and Westinghouse in 1963 and 1964. The first calculator to use LCD technology was introduced by Sharp in 1973. Simple LCDs include a set of alphanumeric characters and sometimes some symbols. More sophisticated LCDs incorporate raster display technologies, especially when used with computers. LCD panels are popular in phones, calculators, and other lowpower, mobile devices such as laptops. External light is needed for the user to see the display unless backlighting is added. An active matrix LCD includes a transistor at each display point to increase the speed at which the crystals can change state and add color. Tektronix further developed “plasma addressing,” which incorporates some of the properties of gas plasma into liquid crystal displays. liquid detector See electrolytic detector. LIS 1. Link Interface Shelf. 2. Logical IP Subnetwork. LISA Laser Interferometer Space Antenna. LISN 1. See line impedance stabilization network. 2. See Low-Incidence Support Network. LISP List Processing. A high level programming language introduced in 1958 by John McCarthy. It is used in many artificial intelligence applications, and as a macro scripting language in applications like AutoCAD from Autodesk Inc. and EMACS. Golden Common LISP is one of the more common implementations of LISP. LISP code is syntactically different from languages such as C, and has been retroactively called an acronym for Lots of Insignificant Silly Parentheses by subsequent generations of programming students due to its nested statements. LISTSERV A significant discussion list software product introduced in 1986 that became prevalent on BITNET, Internet, and local area networks. As of spring 2001, L-Soft International, Inc.’s LISTSERV program was being used to manage over 170,000 local and public lists. LISTSERV is available in commercial and free LISTSERV Lite versions. See discussion list, Majordomo.

list box A list box is a graphical interface device presented to the user for selection from a number of options. The most common type of list box is a directory list. Every time a file is loaded or saved in a different location, or under a different name, a list box is presented to the user. List boxes are so important and so commonly used that it is worth mentioning some that are particularly well-conceived, in order to pass on good ideas to software designers. Beginning in 1986, Bruce Dawson, author of CygnusEd, began developing some of the best directory list boxes available on any system. ASDG Incorporated, developers of Art Department Professional, continued to develop these concepts. The list boxes are sizable and modal (background tasks can be carried out while the boxes are open) and are ideal for long directory listings. The file types displayed can be specified by a pattern, with a wildcard capability included. This is very handy for shortening the list and narrowing a search. The load and save lists are separate, so there is less chance of accidentally overwriting a file of the same name, and the user doesn’t have to constantly switch back and forth between separate load and save directories (as often happens when doing file conversions). Best of all, the pointer location for the list defaults to the file most recently selected, so the user doesn’t have to scroll down every time to locate the same or subsequent file, which is often the one desired. The NeXTStep/OpenStep standardized directory list box is quite different from those independently implemented in Amiga applications. It is also well-conceived, which shows that very different ideas can be equally effective. NeXTStep/OpenStep list boxes show the hierarchical structure of the directories and files in vertical panels in a sizable window. With this design, it is very easy to see the whole structure at a glance and very easy to click to the desired file or directory. In addition, when saving files, it is possible to create a new directory simply by typing in a path. If the directory specified is not found, a dialog box asks if the user wants to create a new directory. If the answer is yes, the system makes a new directory and saves the specified file in that directory in one step. Current versions don’t supply pattern-matching or separate load/save lists as in the previously mentioned Amiga applications, but there’s no reason why the best features of each system can’t be incorporated into future operating systems and software applications and, indeed, some of the NeXTStep concepts are now in part of the more recent Macintosh operating systems. list server A computer file distribution system used for email, newsgroups, discussion lists, and other types of files received from one or many sources, and distributed to one or many subscribers to the service. Using servers to manage the traffic in a centralized

manner can cut down on administrative overhead and provide a means to implement security and selective filtering as needed. listed address LA. A location identifier, such as an email address on the Internet. The concept of the listed address has become important to Internet Services Providers (ISPs) in their management of “spam” (unsolicited bulk email messages). Checking to see if the source of spam is a listed address is one of the ways in which mail can be filtered or selectively processed. LIT See line insulation test. lithium-tantalate A synthetic crystal first grown in the Bell Laboratories, lithium-tantalate was the first really practical alternative to natural or synthetic quartz for the development of a number of communications-related components such as filters. This substance has practical applications for high bandwidth transmissions. See quartz crystal, quartz crystal filter. little-endian Stored or transmitted data in which the least significant bit or byte precedes the most significant bit or byte. Many file incompatibilities between computer systems, in which the file formats are otherwise almost identical, are due to platform conventions which store the data in big-endian or little-endian form. Livermore Automatic Research Calculator/Computer LArc. A supercomputer developed for the Lawrence Livermore National Laboratory (LLNL) in the mid-1950s by the Sperry-Rand Corporation. The LArc had multiple noninterleaved core memory boxes and data, instruction, and DMA access slots; the random access memory (RAM) was mechanical in nature. LLC See Logical Link Control. LLC encapsulation LLC encapsulation is a means to “envelope” a set of packets so that several protocols can be carried over the same virtual circuit (VC). Type 1 and Type 2 are defined for connectionless and connection services. See Logical Link Control. LLC/SNAP LLC/SubNetwork Attachment Point. An encapsulation protocol used in Logical Link Control. In an ATM environment, this is the default packet format for Internet Protocol (IP) datagrams. See TULIP, TUNIC, RFC 1483. LM long-distance marketer. LMI Local Management Interface. See Frame Relay extensions. LMOS Loop Maintenance Operations System. LMS 1. See Local Measured Service. 2. Local Message Switch. 3. Location and Monitoring Service. LMSS Land Mobile Satellite Service. LMST See lightweight multiband satellite communications terminal. LMU Line Monitor Unit. LNA See low noise amplifier. LNP See Local Number Portability. LNW Research Corporation A California company that sold microcomputers assembled and in kit form

in the early 1980s. The LNW-80 was a TRS-80-compatible computer arguably better than both the Apple II and the TRS-80 in that it supported a faster CPU, more memory, and higher resolution color graphics. Unfortunately, the LNW computers didn’t catch the attention of the public and never had the impact of the better-known brands. load coil See loading coil. load distribution unit LDU. A device for distributing electrical loads which may include fault detection circuits, alarms and control systems connected with the load. A load distribution unit can be used for disconnecting system loads to prevent damage to backup systems (e.g., batteries) during prolonged AC power outages or from low voltage exposure. Load Number The Canadian counterpart to the U.S. Ringer Equivalence Number (REN) system. As there may be more than one phone device attached to a single line (modem, fax, answering machine, etc.), a system was established to determine and indicate the ringer load, that is, the electrical load on the phone line associated with a particular piece of equipment. In this way, the Load Numbers can be summed to show the total load, and make sure the line was not overloaded. In the REN system, most lines can handle a load of up to 5.0. In Canada, the concept is the same, but the scale uses larger units; in other words, a standard phone might have a load of about 10 to 20 points, with the total load for a single line being about 100 points. Many electronic devices will show the Load Number somewhere on the main circuit board. load-balancing system LBS. A system for dynamically balancing the execution of jobs to be processed, usually accomplished through software or a combination of software and firmware (as in routers). LBSs are particularly useful in environments where tasks are farmed out to various systems, as on a distributed computer network. A load-balancing system is also used for dynamically balancing the transmission of traffic through a communications pathway, as in telephone circuits. In general, load-balancing systems are used where prior knowledge of what resources may be available at any given time cannot be easily anticipated. LBSs are intended to facilitate and automate task or traffic delegation as transparently and seamlessly as possible. Load balancing is becoming increasingly important as global voice and data networks serve greater numbers of users. Load balancing is distinct from load sharing in that balancing involves the efficient, welldistributed use of resources as opposed to the general availability of a resource to multiple users or processes. Internet Service Providers (ISPs) use load balancers with Internet servers to efficiently manage response times and site access availability. Load balancers can be quite sophisticated, not only distributing user requests across multiple servers, but also rerouting requests if changes occur in the available servers. Depending upon their sophistication, LBSs may

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automatically adjust to server changes without powering down the system and may support security features associated with the service. In CORBA-based architectures, load balancing enables distribution of client processes among servers on a number of levels to balance network, operating system, and middleware-related processing loads. Othman, O’Ryan, and Schmidt have suggested a number of load balancing architectures to support CORBA systems. McArdle et al. have described two types of load-balancing strategies for CORBA-based Service Control Points (SCPs), including a novel antbased algorithm and a distribution method based on mathematical minimization of expected communication flows. SGI has a Network Load Balancing software product that collects Ethernet devices under a single IP address and balances the input and output loads across the Ethernets. Thus, the IP address of the loadbalancing device is advertised (usually through its domain name) and individual IP addresses of the associated devices are not. The variety of approaches to load balancing is reflected in products from Foundry Networks’ ServerIron line, which include Server Load Balancing (SLB), Global Server Load Balancing (GSLB), and Firewall Load Balancing (FLB). The Network Load Balancing component in Windows 2000 scales by distributing IP traffic across multiple cluster hosts. Effective load balancing can lead to higher quality of service for busy multiuser systems or services, such as popular Web sites. Quick response times can make the difference between keeping or losing a potential customer. Fast network transfer speeds are not sufficient in themselves to solve all the aspects of quick access and adding more servers may not be economically feasible. Efficient delegation of tasks and traffic direction through good LBSs is one way to maximize the effectiveness of an existing system. Load balancing is as much art as science. The system must anticipate and adapt to a changing environment and the analysis of the effectiveness of loadbalancing algorithms is, in itself, a challenge. State aggregation and decomposition are two means of assessing dynamic load balancing. In 1997, H. Lin proposed a combination of these methods and introduced the concept of a correlation window for analyzing dynamic LBS policies. The Parallel Programming Laboratory at the University of Illinois conducts research in load balancing, particularly in object migration and seed load balancing, concepts of interest in parallel computing systems. There are a variety of commercial LBSs for telephone trunks and Internet use along with several Internet-related open-source software such as Queue, Supersparrow (for wide area networks), and ANTS load-balancing systems are distributed under the terms of the GNU Public License. See ant, Supersparrow. loading coil A small electromagnetic induction device which helps prevent attenuation of the signal on a wireline. Loading coils were developed in the early

1900s to improve long-distance transmissions in telephone lines and are still commonly used. By calculating the optimum size and spacing the loading coils carefully along a wireline, it was possible to extend a circuit by several times. With the advent of data communications, loading coils have become a mixed blessing. While they improve transmissions in voice grade lines, they tend to add noise and distortion in the higher frequencies used in data transmissions. LOB See line of bearing. Lobe Attachment Module LAM. In a Token-Ring network, an expansion device to extend the number of users that can be accommodated on a single segment of a Token-Ring network. Multiple LAMs (up to a specified number) can be connected to a Controlled Access Unit (CAU). It may also be used with a Multistation Access Unit (MSAU). See Controlled Access Unit, Multistation Access Unit, Token-Ring network. LOC 1. line of communication. 2. See Loss of Cell. Local Access and Transport Area LATA. The terms of the 1984 AT&T divestiture resulted in the creation of numerous geographically local telecommunications service areas, of which there are now more than 200 in the U.S. LATAs are determined, to some extent, by population densities. Originally, local Exchange Carriers were not permitted to connect calls across LATA boundaries, as that was the privilege of Inter Exchange Carriers (IXCs). Since that time, the rules have been modified to some extent. See Inter Exchange Carrier, Modified Final Judgment. Local Area Augmentation System LAAS. A VHFbased Global Positioning System (GPS) augmentation system which functions along with the Wide Area Augmentation System (WAAS) to provide high-accuracy satellite-based navigation services for aviation, LAAS provides navigation and landing data where WAAS cannot be used. LAAS meets Category II/III aviation requirements in specific locations. Further details are available through the Federal Aviation Administration (FAA). See Wide Area Augmentation System. http://gps.faa.gov/ local area network LAN. A computer network within a specified geographical space, such as a building or region, or within an institutional entity such as a classroom or department. The network is a means by which the computers are linked to one another and can access a variety of shared resources, typically files, application programs, and peripheral devices such as printers, fax machines, modems, and scanners. Connections between the computers are through wires or wireless signals. LANs are typically connected directly by telephone wire or coaxial cables, and thus are somewhat constrained in physical size and number of users, due to lower transmission speeds, network topology, signal reduction (see attenuation), and fixed-bandwidth limitations, than wide area networks (WANs). There are a number of common ways in which LANs are connected, with various commercial, shareware, and freeware products to handle the software tasks

associated with networking. One of the most popular server products is Apache, which is robust, freely distributable, and very widely installed. Commercial products include IBM Token-Ring, Microsoft NT, and Novell Netware. As technology advances and becomes less expensive, direct cabling will probably decrease and wireless solutions become more common, thus reducing the distinction between LANs and WANs. See Token-Ring, virtual LAN. local area data transport LADT. Data transmission services offered over existing local phone lines. In general, it is a low-speed, low-cost option practical for many casual users of data services. In some cases, the system has been enhanced to provide simultaneous voice and data (e.g., ISDN services). The growing availability of U.S. ISDN (USDN) services is increasing the likelihood that local ISDN-based LADTs may eventually provide transport among LADTs. The abbreviation also refers more specifically to AT&T’s commercial LADT offerings, which include protocol conversion. See ISDN. Local Area Signaling Services LASS. Commercial adjunct processor-based services used to create initial orders. A Bulk Calling Line Identification (BCLID) service provides private branch exchanges (PBXs) with information on calls from outside the PBX group. Local Area Transport LAT. A proprietary communications protocol for terminal-to-host transmissions, developed as VAX systems by Digital Equipment Corporation (DEC). local area wireless network LAWN. A local home, business, community organization, campus, or other phone or data network which uses wireless technology to provide the links. The communication is often carried out over radio frequencies (RF) in the frequency modulated (FM) or infrared range. Techniques common to LAWN include spread spectrum, originally developed for government operations, and narrowband. See Industrial Scientific Medical, spread spectrum. Local Automatic Message Accounting LAMA. An automatic message accounting (AMA) system used in local telephone switching centers in conjunction with number identification information to collect billing data. It also automates the routing of longdistance calls through more than one local office. local battery Equipment which draws power from a local source, rather than drawing current from the line to which it is attached. Most phones draw current from the phone line sufficient to operate the phone, but if they have extra features (LCD display, speakerphone, etc.), they may require additional power which comes from a battery or local wall socket. Laptop computers use local battery peripherals, such as PCMCIA modems, rather than those which require separate power, e.g., desktop modems, to maximize convenience and portability. Local Bus Computer processors require a way to communicate with the many devices that make a computer useful: storage, printers, modems, input

devices, scanners, etc. The local data bus is usually an internal interface that links the motherboard and various controller cards and other interface connectors that comonly communicate with external devices. Many different standards are defined for bus transmissions, and the bus speed does not always match the CPU speed, creating a processor bottleneck for some types of processes and activities. A Local Bus is one of the newer, faster buses beginning to supersede other common buses, including EISA, VESA, and PCI. local call A telephone service phrase referring to calls placed through the local exchange, billed on the subscriber’s predetermined regular service plan. These are generally geographically close. There are three common types of billing systems for local calls: 1. unlimited calls for a flat rate monthly fee, 2. flat rate up to a certain number of calls, then a per-call charge beyond that, or 3. a per-charge call which may or may not be scaled according to the total number of calls for the month. The first option is widespread in Canada and the U.S., while many places in Europe use the third option. For contrast, see long-distance. local differential GPS LDGPS. An implementation of the Global Positioning Service (GPS) designed to improve local accuracy of the data. A single GPS receiver is placed at a known location where it can receive GPS signals. It becomes a reference station which forms a scalar correction for GPS satellites within current view; broadcasting the correction information is provided to local users. Since there is degradation over distance, a series of “cells” would be needed to apply this system over a large geographical area. See differential GPS, wide area differential GPS. Local Exchange Carrier LEC. A designation for a local telephone company, now more commonly distinguished as an Incumbent Local Exchange Carrier (LEC) or a Competitive Local Exchange Carrier (CLEC). This is defined in the Telecommunications Act of 1996, and published by the Federal Communications Commission (FCC), as meaning: “... any person that is engaged in the provision of telephone exchange service or exchange access. Such term does not include a person insofar as such person is engaged in the provision of a commercial mobile service under section 332(c), except to the extent that the Commission finds that such service should be included in the definition of such term.” See Federal Communications Commission, Telecommunications Act of 1996, United States Telephone Association. Local Exchange Carrier duties The Federal Communications Commission (FCC) stipulates a number of duties in the Telecommunications Act of 1996 as shown in the Telecommunications Act chart. local heap See heap memory. local loop In telephone installations, a physical link

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through a wire pair connection between the subscriber, which may be an individual, a business, or a private branch system, and the switching office. The local loop once included the connection right to the subscriber’s phone, but now the demarcation point is usually a patch panel or exterior connections box (although to-the-phone is still available for a fee). Local Management Interface LMI. In Frame Relay networks, an extended specification for information exchange between devices. See Frame Relay Extensions for more detail. Local Measured Service LMS. A telephone billing system in which subscribers pay according to the number of calls made or received (or both), rather than according to a flat monthly rate. Measured service is sometimes provided at a flat rate up to a specified number of calls, and then a per-call fee above that number (many banks set up checking charges this way as well). Generally, LMS is interesting to those who make very limited use of the phone or who have a line primarily for incoming calls. In some countries, all service is measured and even calls that are unanswered or that result in a busy signal may be billed in some areas. local multipoint distribution service LMDS. A proposed terrestrial wireless communication service designed to send video over small cells. This would be competitive with urban cable TV services. The Federal Communications Commission (FCC) released a Notice of Proposed Rule Making on the LMDS proposal in December 1992. This led to various FCC proposals to segment the transmissions band, with the effect that the primary spectrum would be limited to the 27.5 to 29.5 GHz range. Long-term advocates of satellite communications

were concerned that this approach would limit future evolution and growth of satellite communications deployment. Local Number Portability LNP. A telecommunications service to enable local telephone numbers to be retained even if a subscriber’s carrier is changed. LNP was implemented in the mid-1990s and made it easier for phone services to compete. The management of LNP services is, in part, dependent upon the maintenance of regional databases containing the numbers and the vendors servicing those numbers. See Local Number Portability Administrator, Location Routing Number. Local Number Portability Administrator A managing authority tasked with administering the Local Number Portability database for tracking and updating local numbers and the telecommunications carriers servicing those numbers. NeuStar, Inc. (formerly Lockheed-Martin Information Management Service) is currently the administrator for the Local Number Portability Administration Center (NPAC). See Local Number Portability. local service ordering guidelines LSOG. Requirements published by individual communications carriers to instruct customers on how to pre-order or order local connection products and services. LSOGs typically identify Order and Billing Forum (OBF) industry guidelines and carrier-specific requirements. After presenting the guidelines, the carrier will usually offer a variety of forms to the customer to sign up for services. Gone are the days when you could simply ask a phone company to install a phone. Now you must read guidelines and fill out forms to identify various choices of equipment leasing or buying, various

Telecommunications Act – Stipulated Local Exchange Carrier Duties “Each local exchange carrier has the following duties: ‘(1) RESALE The duty not to prohibit, and not to impose unreasonable or discriminatory conditions or limitations on, the resale of its telecommunications services. ‘(2) NUMBER PORTABILITY The duty to provide, to the extent technically feasible, number portability in accordance with requirements prescribed by the Commission. ‘(3) DIALING PARITY The duty to provide dialing parity to competing providers of telephone exchange service and telephone toll service, and the duty to permit all such providers to have nondiscriminatory access to telephone numbers, operator services, directory assistance, and directory listing, with no unreasonable dialing delays. ‘(4) ACCESS TO RIGHTS-OF-WAY The duty to afford access to the poles, ducts, conduits, and rights-of-way of such carrier to competing providers of telecommunications services on rates, terms, and conditions that are consistent with section 224. ‘(5) RECIPROCAL COMPENSATION The duty to establish reciprocal compensation arrangements for the transport and termination of telecommunications.”

carriers for different services, optional “value” or “feature” packages, optimum proportion of data services, phone services, number of extensions, extra lines, etc. Many carriers now publish the forms online. This is a great convenience except that many of them offer the forms only in Microsoft Word (a proprietary commercial product) instead of using a format such as PDF, for which the vendor (Adobe) offers freely downloadable readers. Hopefully more vendors will use file formas with free readers in the future for distributing Web forms to potential customers. local service request LSR. The process by which a telecommunications customer requests local service. For example, a Competitive Local Exchange Carrier (CLEC) would carry out LSR procedures to order loops from Bell Telephone. Many carriers now provide the request forms on the Internet for download. They can then be mailed or, in some cases, emailed or otherwise submitted electronically. When a local service request is combined with other requests in order to set up an enhanced loop service, the procedure and forms are collectively known as an access service request (ASR). An administrative LSR may be required to identify a CLEC. Local Services Provider LSP. A telecommunications provider that specializes in local services (e.g., local telephone services) rather than regional or national services (e.g., long-distance calling). local signal transfer point LSTP. In mobile personal communications services, one or more local message routing translation and screening points. A local signal transfer point is associated with a LATA geographical area connecting to multiple service switching points (SSPs). One or more LSTPs may be connected to a regional signal transfer point. Mobile switching centers (MSCs) are connected to the signaling network (e.g., SS7) through a local signal transfer point. LOCAL TV Act of 2000 An act which created a $1.25 billion Federal loan guaranteed fund to assist residents in rural areas to receive urban and local TV broadcast signals through satellite transmissions. Thus, both profit and nonprofit organizations could access resources for offering local broadcast signals, with the government guaranteeing a portion of the loan. An amendment cleared the way for electric cooperatives and telephone systems to participate in the loan guarantee program. LOCAL TV is an acronym for Launching Our Communities’ Access to Local Television. The Act was drafted in part because the 1999 Satellite Home Viewer Improvement Act (SHVIA) did not include legislation to help rural Americans receive local broadcasting. See Rural Local Broadcast Signals Act, Satellite Home Viewer Improvement Act. LocalTalk A proprietary local area network AppleTalk-compatible protocol developed by Apple Computer and used on Macintosh computers and peripherals. LocalTalk is not a fast protocol, but all Macs come networkable right out of the box, with a simple serial cable, and something can be said for ease of use and convenience, particularly in school and work

environments. See AppleTalk. Location Area Identity LAI. A subscriber identity allocated and assigned on a location basis as part of the Temporary Mobile Subscriber Identity (TMSI) used in a Global System for Mobile Communications (GSM). Location Routing Number LRN. A 10-digit number to uniquely identify a switch in a telephone circuit. In the 1990s, LRNs facilitated the implementation of competitive services such as Local Number Portability (LNP). Various regulatory agencies supported this AT&T/Lucent system and it became an industry standard that was subsequently adopted by the Federal Communications Commission (FCC), in 1997. See Local Number Portability. LODE See Large Optics Demonstration Experiment. lodestone, loadstone A natural magnetic material called magnetite, an oxide of iron. All magnetite can be readily magnetized. This material was used to create early compasses and was called magnes lapis, magnetic stone, or magic stone. It is called lodestone when it comes out of the ground already exhibiting magnetic properties. Lodestone is probably the same stone mentioned by Plato in Timaeus as “... the Heraclean stone,” since the Heraclean stone was paired in the same sentence with the attractive properties of amber. See amber, magnet. Lodge, Oliver Joseph (1851-1940) An English physicist who demonstrated that radio waves could carry a signal over distance, in 1894. Lodge is also known for his experiments with tuning in radio waves, ideas further developed by succeeding scientists. Lodge-Muirhead detector A simple, early type of self-restoring radio-frequency detector built by hobbyists and commercial manufacturers in the early 1900s. It employs a small steel revolving wheel, with the outer edge sharpened to a very fine edge, supported between slots on frame posts on either side of a rod passing through the center of the wheel. A small motor supplies the power to quickly turn the wheel. A hard rubber cylinder with a slot cut in the top sits directly under the wheel. Mercury is poured into the slot and makes contact with a binding post threaded in from the outside of the rubber. A thumbscrew is installed in the rubber to raise or lower the mercury level. When the wheel revolves, it makes contact with the mercury and the signal is translated through the mercury, by means of brushes, to the binding post which connects to the rest of the circuit, including a receiver. The battery power to the motor is controlled by means of a potentiometer. See detector. LOF 1. See Loss of Frame. 2. lowest operating frequency. LOFAR See Low Frequency Array. log in, log on v. To gain access to a console, computer, or network terminal through software, usually by typing certain keystrokes, or selecting a button. Secure systems may require a name, or a name and password. If an authorized name or password is not correctly given, the system may, after a certain number

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of failed attempts lock out any subsequent attempts, and, as in banking or government systems, may even notify the system operator of an attempted break-in. Most systems let you keep trying, however. A succession of logins may be necessary in order to gain access to subsections of the system after the first login. The most effectively whimsical failed login message this author has seen is on NeXTStep, where an incorrect login results in the login window shaking rapidly back and forth for a few moments (as if shaking its head to say no). The verb form of log in is two words, as in “I plan to log in now.” Otherwise it’s one word, as in “My login attempt failed.” log off, log out v. To exit a console, computer, or network terminal session, usually by typing: logout, logoff, done, exit, or quit; or by clicking the appropriate button (or simply by hanging up the modem, though this is an untidy way to exit). Some logout routines will display a log summary of the session showing the length of the session, and sometimes even the type of activities. It’s important to effectively log out of secure systems, or the next person sitting down at the console may have access to unauthorized files or programs. The verb form of log off is two words, as in “I plan to log off now.” Otherwise it’s one word, as in “My logoff is done, you may have the terminal ...” log-periodic antenna A periodic antenna is one in which the input impedance varies as the frequency varies. Log-periodic antennas employ a variety of arrangements of active dipoles interconnected to provide broadband, high-gain capabilities. They are commonly used for very high frequency (VHF) signals. logic bomb A software program designed to penetrate a system, present a message (sometimes through graphics or sound), or damage memory or stored data, when some particular logical operation happens. A time bomb is a type of logic bomb which can, for example, wipe all the data off a hard drive when the bomb detects that it is April 1. Logic bombs are not always malicious, but they are seldom appreciated. They generally fall into the category of practical jokes, which are usually funnier to the perpetrator than to the intended object of the joke. See virus. logical block In storage devices, such as hard drives and magneto-optical devices, the smallest addressable unit. Each block is associated with a unique number, usually starting with 0, and incrementing for each succeeding block. This allows the system to locate data, read and write to the device, partition the drive, etc. in an organized manner. Logical Block Address LBA. A means for saving and retrieving information by accessing block addresses on a storage medium, rather than by using cylinder-head-sector addressing schemes. The blocks on the storage medium are addressed sequentially, usually starting with zero. SCSI peripherals use this addressing method. Some IDE drives are now be-

ginning to use this method, but it may be necessary to request LBA mode explicitly. logical drive A drive configured separately from the physical configuration of the drives. For example, a computer may have three drives, each with several partitions, but logically, the system may organize them into four logical drives with various partitions from different drives in such a way that the user “sees” four drives rather than three, of sizes set by software. Conversely, a system may have three drives, each with a couple of partitions, which are aggregated into one drive. Thus, the storage space appears to the user as one large drive. Not all operating systems can organize drives in this way. Some of the lower-end personal computers have limitations in the configuration of logical drives. logical link A link between nodes or devices based upon an abstract rather than a physical topology. Thus, virtual LANs, logically direct connections, and other types of paths can be set up in association with the physical connections. Logical Link Control LLC. The upper sublayer of the layer 2 Open Systems Interconnection (OSI) protocol. LLC provides data link level transmissions control. It is the default multiplexing layer for Internet Protocol (IP) over AAL5. It was developed by the IEEE 802.2 committee to provide a common access control standard for networking which is independent of packet transmission methods. It includes addressing and error checking capacities. Logical Storage Unit LSU. A buffer unit which connects to PBX systems to store call information. Also known as a buffer box or poll-safe. logical topology In a network, the connections and relationships between computers and various devices may not map in a one-to-one relationship with the physical topology. Thus, logical topologies, organized and managed in software, may be administered and diagramed separately or as an overlay to the physical connections. In large networks, logical topologies often require tracking and display programs to configure and troubleshoot the logical connections. From a user’s point of view, many aspects of a logical topology can make computing more efficient and enjoyable. As a simple example, there are workstation networks which allow hard drives to be mapped in such a way that they appear as one giant drive to the user, even though the data may physically be spread over a number of partitions and drives. Thus, the user doesn’t have to worry about whether there is enough space, which drive to use, or on which drive or partition that old file was stored. The operating system takes care of all the housekeeping involved in managing the system. On a larger scale, the same can be said of whole systems. The user may be using an application program located on a machine in another room, another building, or another state, but it can be logically mapped in so that it appears to be running on the local machine. Commercial software programs with graphical user interfaces exist to help manage logical topologies and, in some cases, various management utilities come with the operating system.

logical unit number LUN. The LUN is an identification system used with SCSI devices which allows the computer and controller to distinguish and communicate with up to seven devices including the controller for each SCSI chain. Each device must have a unique ID so that the controller can administer more than one device when they are chained together. logiciel Software, in French. login script, logon script A login script is a file that includes commands or variable settings pertaining to the login and initial setup. The two most common functions of a login script are: 1. to set up the system to the specifications of a particular terminal, and 2. to set up the preferences for a particular user or set of users. In the first case, the login may include information about the characteristics of the terminal, such as hardware-specific keyboard mapping, graphics card settings, etc., as well as environmental variables, patches, and other initialization parameters. In the second case, the settings may include the user screen size and color preferences, preferred fonts, frequently used applications, permissions, and other characteristics of the user environment. See batch file, JCL, Perl. LOLA The Language of Temporal Ordering Specification (LOTOS) Laboratory. See Language of Temporal Ordering Specification. LON local operating network. See LONWORKS. Long Distance Internet Provider LDIP. Cooperative services offered by companies that operate under restrictions set by the Modified Final Judgment (MFJ) who wish to provide Internet services. long haul communication A call which extends beyond the local exchange area. long key A key held down for longer than a prescribed period which signals an event separate from a short press of the same key. For example, a long key on a computer keyboard might cause the character associated with the key to repeat, or to initiate a key-related process. long tone In telephony, a long key is one which signals for longer than other keys, in order to communicate through various automated phone menu systems. That is why many phone system menus instruct you to press the pound key (#) after typing in a number, so that a long key signal will be transmitted. long-distance call, toll call A telephone service referring to any call outside the local service area. Long-distance calls are frequently completed and charged through a carrier other than the local service, and include extra digits in order to identify the desired destination. Long-distance calls are usually billed in a cooperative arrangement through the local carrier, although some services may be billed separately. Sometimes called a trunk call, though this phrase is less common. The first recognized long-distance call is said to have been a one-way message from Alexander Graham Bell’s father in Brantford, Ontario, Canada, to Bell in Paris, Ontario, in 1876. The first two-way longdistance call was between Bell and Watson in Cambridgeport and Boston, respectively.

The first transcontinental phone line went into service in 1915, connecting San Francisco and New York City, with Edison and Watson conducting the first conversation over this line. About a decade later, long-distance radiotelephone service was established across the Atlantic Ocean. Some of the important inventions which made longdistance communications possible were Pupin’s loading coils, de Forest’s triode, Armstrong’s regenerator circuit, and microwave antennas introduced in the early 1950s. Contrast with local call. long-distance carrier IXC. Local long-distance providers which are competitive with incumbent local exchange carriers. longitudinal redundancy check LRC. A data transmission error checking technique incorporating a block check on a group of data. An accumulated Block Check Character (BCC) is compared to the sending BCC; if they match, the block is considered to have been transmitted without errors. See cyclic redundancy check. LONMark Certification A program to ensure interoperability among functional LONWORKS devices, developed by the LONMark Interoperability Association. See LONWORKS. LONMark Interoperability Association A trade organization of companies supporting and promoting the LONWorks control automation system, established in 1994. The association aids in the integration of multivendor systems for building, home, transportation, and industrial environments. Permission to display the LONMark logo is awarded by the association to firms that successfully complete the LONMark Certification conformance tests. http://www.lonmark.org/ LONTalk A communications protocol associated with LONWORKS automation products that enables intelligent control to be associated with motors, fans, switches, sensors, valves, and other industrial, transportation, and residential/business automation applications. The protocol is designed to be able to support more than 500 transactions per second and priority levels may be assigned. It follows the Open Systems Interconnection (OSI) reference model and is currently the only product of its kind to implement all seven layers of the model. LONTalk is favored in part because of its reliability. Unlike some automation systems with one-way communications only or two-way communications without acknowledgments, LONTalk supports end-toend acknowledgments and automatic retries. Thirdparty developers of LONTalk have further developed “heartbeat” techniques to enable individual nodes to “check in” with a main or management controller to let the controller know all systems are functional. Alarm conditions can be triggered if nodes do not respond as expected. LONTalk is powerful. Each node supports Network Management Services (NMS) such that they can respond to LONTalk commands from any node supporting NMS functions. Hierarchical addressing

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through domain, subnet, and node addresses can be used to interact with the network at any level. LONTalk can be implemented over a variety of types of media, including twisted pair, power line (similar to X-10), radio links, and coaxial or fiber optics cables. The LONTalk protocol can be implemented into microprocessors under the EIA-709.1 control networking standard by companies such as Echelon Corporation. See LONWORKS, Neuron Chip. LONWORKS An internationally installed, open network automation and control system for industrial and residential markets developed and trademarked by Echelon Corporation. LON stands for local operating network. The LONWORKS system uses intelligent control nodes intercommunicating with a common protocol called LONTalk. Each node includes embedded protocol and control functions and a physical interface for coupling the node controller to the communications medium. Nodes may be a variety of drives, relays, and sensing devices and may be used for automation, production lines, security, and more. Local control nodes are the basic network devices for operational control and actuation. Supervisory nodes collect and log data from the local control nodes or coordinate their behavior. Routers provide connectivity and flow between LONWORKS network channels. The LONWORKS protocol can be embedded into processors, from 8-bit microcontrollers to 32-bit microprocessors. The Neuron Chip is a low-cost, commercially available processor with LONTalk support built in. In 1999, LONWORKS was approved as an open industry standard by the American National Standards Institute (ANSI/EIA 709.1-A-1999 Control Network Protocol Specification). The protocol is also approved by IEEE and other professional societies. Intelligent Technologies (IEC) is a significant thirdparty developer of LONWORKS-compatible products. See CEBus, ICELAN 2000, LONTalk, Neuron Chip, X-10. Look Ahead See Query on Release. Loomis, Mahlon (1826-1886) An American dentist and researcher who was intrigued by the fact that early telegraphs could be run with only one wire, with earth providing the conductor for the return circuit. He reasoned that if earth could act as one conductor, then perhaps air could act as another, especially since Benjamin Franklin’s experiments had alerted scientists to the electricity in the air. In 1865 or 1866 Loomis devised an experiment in which he raised kites with equal lengths of fine copper wire and demonstrated that a signal could be transmitted from one to the other without direct physical contact. He received a U.S. patent for his improved wireless telegraphic system in 1872. loop 1. A complete transmissions circuit, or electrical circuit. 2. In telephone systems, a loop comprises the wire transmission path that extends from the central office to the residential or business subscriber and back.

loop, communications hardware A circuit, conduit, or line which comprises a continuous path with starting and ending points meeting at the same geographical point. The start and end points may or may not be joined. A loop may or may not include nodes. Communications through the loop may be unidirectional or bidirectional. A loop need not be roughly circular, although it sometimes is; often a loop consists of two adjacent lines, one which sends, the other which receives. Some loops send and receive on the same line (especially if it’s a wider bandwidth medium such as fiber), so the loop aspect is based more on the nature of the transmission than the configuration of the cable. See local loop, Fiber Distributed Data Interface, Token-Ring. loop, programming In software, a programming loop is a series of instructions which will repeat until some event or condition occurs to cause the software to drop out of the loop, or to branch to a specified destination. An endless loop is one which, theoretically, goes on forever. In actual practice, an endless loop often indicates a fault condition and is usually externally terminated. See nesting, recursion. loop antenna A type of radio direction-finding antenna with one or more complete continuous loops of wire, the ends of which connect to complete the circuit. Loop Data Maintenance Center LDMC. See Loop Facility Assignment and Control System. Loop Facility Assignment and Control System LFACS. A database inventory of records and assignments associated with outside telecommunications loop facilities, including connection points, terminals, cables, etc. loop start In telephony, it is necessary to take control of a line before it can be used. There are two common ways to do this, with a ground start or a loop start. The loop start is the type commonly found in residential and other single line phone lines. When you pick up a phone, the plunger is released (offhook) and the circuit sends a supervisory signal by bridging the two wires in the phone connection (traditionally called tip and ring) with direct current (DC). This is done so that the subscriber will get a dial tone and a circuit through which to connect the call. The central telephone switching office sends a signal to the phone the caller is trying to reach and rings the number until it goes off-hook when it is picked up by the callee. When the loop is detected, the ringing signal is no longer set. See ground start. loop test, loopback test A procedure by which a circuit is connected in a loop in order to test for faults or differences in signal strength or data integrity after passing through the loop. This is commonly used in installation of new circuits or troubleshooting existing circuits. For example, when installing a modem, looping the circuit through the computer system before connecting it to the public phone system can help predetermine whether the basic circuits, software, etc. are correctly installed before adding the additional factors associated with the phone circuit.

loop testing system LTS. In telephony, a subscriber line diagnostic system for physical level testing of copper wire circuits. loop-through wiring A telephone wiring configuration commonly found in residences and other circuits where economy tends to be a higher priority than high reliability or redundancy. The wire runs from the junction point where the telephone company’s wire reaches the house, then travels from room to room in electrical parallel while being physically wired in series. Like lights in older, serially wired Christmas light strings, a break in the circuit will interrupt power to all subsequent phones in the circuit. The alternative is home-run wiring (a form of star topology) in which separate wires run from the phone company junction point to each device on the circuit so that a break in a circuit affects only the device on that circuit. Loop-through wiring is certainly adequate for a circuit with only one or two communications devices, but if the premises have a variety of fax, modem, and telephone devices, homerun wiring is preferable. loose cable In the fiber optics network industry, jargon for general purpose outdoor cables (as compared to indoor interconnect cables, for example). Loose cables are used for aerial, underground, and outdoor conduit installations and sometimes for indoor use. Loose cables come in a variety of different types with varying fiber counts and degrees of shielding. loopback test See loop test. loran long range navigation. A system of distance navigation in which several radio transmitters (usually land-based) are used to send out pulsed signals from different directions in order to determine the geographic location of the craft using the loran system. Useful for air- and watercraft under some circumstances, but limited by the availability and distance of loran stations. See Global Positioning System. LORG 1. Marketing jargon for large organization. 2. localized orbital/local origin. Methods that can be applied, for example, to shielding/chemical shift calculations. Lorimer switch One of the first commercially promoted automatic telephone switches, patented by the Lorimer brothers in 1900 and put into service in 1905. While it had many improvements on its predecessor, the Callender switch, it probably owes some of the impetus for its development to this earlier invention. It was installed in a number of switching systems in Europe, but was never fully reliable. However, the technology was modular and could be extended, an important influence on future telephone switching systems. See panel switch, rotary switch, Strowger switch. Lorimer telephone An early telephone design powered by a central battery system and dialed with a series of levers representing units, not unlike an old calculating machine or cash register. Setting levers configured a telephone number. Lorimer, George William A Canadian employee of inventor Romaine Callender, George William

worked as a telephone operator at the Callender Telephone Exchange Company. He and his brother, James Hoyt Lorimer, later accompanied Callender to New York where Callender was seeking financing to establish a new company after filing a series of patents on telephone switching technology that he was not able to implement in Brantford, Ontario.

L

A Lorimer desk phone showing levers set by the caller to signal the number to be called. This was the beginning of dial telephones that eventually supplanted manual switchboard operators for local calls and, eventually, long distance calls (many decades later).

In New York, the group succeeded in creating an automatic switching system, after which they returned to Brantford. Callender traveled to England to found the Callender Rapid Telephone Company, and the Lorimer brothers founded the Canadian Machine Telephone in Peterborough in 1897. After the death of his brother, James, Egbert Lorimer joined George in marketing their technology. See Lorimer switch; Callender, Romaine; Lorimer, James Hoyt. Lorimer, James Hoyt The brother of George William Lorimer, James originally studied law, but became involved in telephone switching systems research with his brother and George’s employer, Romaine Callender. Together the Lorimers founded the Canadian Machine Telephone company in 1897. James had a strong mechanical aptitude, and the brothers continued to improve on the Callender switching technology until it was patentable in 1900.

James Hoyt met an untimely death after which no significant technological innovation occurred in the partnership, although the products continued to be marketed. See Callender, Romain; Lorimer, George William. LOS 1. launch on schedule. 2. line of sight. 3. See loss of signal and Loss of Signal. loss 1. A decrease in power of a transmission signal as it travels toward its destination, usually expressed in decibels (dB). Many factors contribute to loss, such as distance, type of signal, weather, signal modifications through switches and routers, equipment characteristics, etc. Loss through a circuit is cumulative. See amplifier, interference, noise. 2. In a network, a quantitative measure of a reduction in system resources or services arising from undesired factors such as faulty equipment or configuration, vandalism, or incorrect usage. Loss of Cell LOC. In ATM networking, a performance monitoring function of the PHY (physical) layer in which a maintenance signal is transmitted in the overhead indicating that the receiving end has lost cell delineation. Loss of Frame LOF. In ATM networking, a performance measure indicating whether frame delineation has been lost. The LOF is transmitted through the physical (PHY) overhead. On some systems, a LOF condition will be signaled on a port with a light-emitting diode (LED), or as a “yellow alarm.” loss of signal LOS. In a general sense, the sudden, undesired, or unexpected loss of a transmission or other signal such as a beep, alarm, light signal, code, speech, or data signal. LOS results from many causes: interference, a break in the circuit, a change in the surrounding environment (pressure, sun spots, moisture, loss of light, etc.). Loss of Signal LOS. In ATM networking, a performance measure indicating that the receiver is not getting the expected signal, or that there is simply no signal because nothing is currently connected. The LOF is transmitted through the physical (PHY) overhead. On some systems, a LOS condition will be signaled on a port with a light-emitting diode (LED). lossless compression A type of data compression technique which does not lose information contained in the image in the compression stage. Some compression algorithms average, sample, or remove image information in order to achieve a high degree of compression, e.g., JPEG. Others retain all the information, e.g., TIFF. See compression. Contrast with lossy compression. lossy compression A type of data compression technique which selectively or randomly loses information contained in the image in the compression stage. These algorithms average, sample, or remove image information in order to achieve a high degree of compression, e.g., JPEG. New wavelet mathematics is providing some very interesting compression options which provide a high degree of compression with a surprising degree of fidelity to the original image when decompressed and displayed. Other techniques retain all the information, e.g., TIFF. See compression,

discrete cosine transform, fractal transform, wavelet. Contrast with lossless compression. LOTOS See Language of Temporal Ordering Specification. loudspeaker A device designed to amplify sound, especially voice or music. It may be mechanical or electrical. A mechanical loudspeaker may be as simple as a bowl or horn-shaped object that directs sound. An electrical loudspeaker is familiar to most people as the “PA system” (public address system) installed in most public schools. See amplifier, audio, intercom, sound. Lovelace, Ada Augusta (1815-1851 or 1852) Countess Ada Lovelace (nee Byron) was the daughter of the famed English poet Lord Byron. Ada Lovelace worked with the computer pioneer Charles Babbage, and is regarded as the first computer programmer for her description of how an analytical machine might compute Bernoulli numbers. She proposed the possibility of using computers to compose music or produce graphics. A computer language (ADA) was developed by the U.S. Department of Defense and named after her. See ADA; Babbage, Charles.

Ada Lovelace had an active interest in the sciences and the arts and speculated on the future capbilities of “thinking machines.”

LOW launch on warning. low Earth orbit LEO. An orbiting region around the Earth into which certain types of communications satellites are launched. There are advantages and disadvantages to a low orbit. The main advantage is that it generally requires less power to transmit and receive at lower altitudes; the main disadvantage is that it requires a larger number of satellites to provide full global coverage. Other factors include lower radiation levels and lower launching costs. The lifespans of low-orbit satellites tend to be around 5 to 8 years. Most low-orbit satellites travel at about 500 to 2000 km outside Earth. A region called the Van Allen radiation belt at the outer regions of low Earth orbit is

generally avoided between the LEO and medium Earth orbits (MEOs). LEO satellites are primarily used for cell phone and data communications. Communications designed for lower orbits require a larger number of satellites than those for higher orbits. This necessitates greater coordination to handle the larger number of systems and to deal with the shorter periods during which each satellite is within range. In contrast, high Earth orbit (HEO) systems can blanket the Earth with only three or four satellites. The trade-off is that higher-placed satellite transmitters require more power to beam the greater distances. See Ellipso, Global Positioning Service, Globalstar, high Earth orbit, Iridium, medium Earth orbit, Orbcomm, Teledesic. Low Frequency Array LOFAR. An electronic array functioning as an electromagnetic imaging interferometer in the approximately 10- to 150-MHz frequency range. The goals of the LOFAR astronomical project include the study of solar and planetary radio emissions and imaging of the high-redshift emissions. It is hoped the LOFAR research may reveal new classes of physical phenomena in the process of investigating new regions of the electromagnetic spectrum. The work is being carried out by members of the LOFAR Consortium, which includes the U.S. Naval Research Laboratory, MIT, and the Netherlands Foundation for Research in Astronomy. low level formatting In storage devices such as hard drives and cartridge drives, formatting is the process of arranging the magnetic media on the storage surface to conform to a recognized pattern so the operating system can further organize data on the drive (the next step is usually to high-level format [initialize] and partition the drive). Each operating system has its own file formats, the protocols that allow it to create directories, organize files and file pointers, and read and write information from and to the drive. Some operating systems are designed to recognize the file formats of other systems as well. For example, on Macintosh and NeXT systems, if a DOS/ Windows disk is inserted in the drive, the Mac or NeXT OS will recognize the foreign drive and read and write data files to the drive (and perform minor conversions as necessary) in the format of the diskette, rather than the native operating system format. This provides the user with a lot of flexibility in terms of data transfer and conversion. This does not mean that executable files from other systems can be run on any platform, but rather that files can be moved about as needed. Most drives now come low-level formatted from the factory, but if you have serious data loss on a drive, sometimes as a last resort, you may need to reformat the drive to make it usable again. low level language A computer control or programming language at the machine or assembly level at which individual registers, accumulators, and other aspects of the physical architecture can be directly or nearly directly controlled. Low level languages are rarely used these days except for writing simulators for various types of processors.

It is much more common now to use high-level programming languages to create source code, and then engage an intermediary program, called a compiler, to translate the high-level language into machine instructions. A certain amount of bit-twiddling can be accomplished in some of the medium- or high-level languages, but is needed only in limited circumstances. Contrast with high-level language. low noise amplifier LNA. A component which amplifies and sometimes converts telecommunications signals, typically from satellite transmissions. In a satellite receiving station, the LNA takes signals from the feed horn, amplifies them, and then converts them or sends them to a separate low noise converter (LNC); from there they are transmitted to the receiver, usually inside a building. See feed horn, low noise converter, parabolic antenna, satellite antennas.

feed horn

L

optional lever for controlling polarity

A low noise amplifier (LNA) probe is commonly included in the feed horn mechanism of a parabolic antenna and may have a lever to adjust for horizontally- or vertically-polarzed transmission signals.

low noise amplifier probe LNA probe. A component that works in conjunction with a low noise amplifier to control the signal polarity, which can be set to either horizontal or vertical, in order to accommodate more channels on a single system. The LNA probe is typically built into the feed horn mechanism on parabolic antennas. low noise block converter LNB. A component which converts amplified signals, usually to a lower frequency to send to a receiver. In telecommunications, it is commonly used with satellites and may be incorporated into the low noise amplifier (LNA). LNBs have a broader range than LNCs, as they are able to convert a range of frequencies (provided they have the same polarization) rather than just a single frequency, as in LNCs. See low noise amplifier, low noise converter, parabolic antenna, satellite antennas. low noise converter LNC. A component which converts amplified signals, usually to a lower frequency to send to a receiver. In telecommunications, it is commonly used with satellites and may be incorporated into the low noise amplifier (LNA). LNCs work with specific frequencies. See low noise amplifier,

low noise block converter, parabolic antenna, satellite antennas. low pass filter A filter that passes transmissions below a specified cutoff frequency, with little or no loss or distortion, but effectively filters out higher frequencies. See high pass filter. Low-Incidence Support Network LISN. A support network in California for providing access and information to individuals and families affected by low-incidence disabilities, including visual and audio impairments, severe orthopedic impairments, and combinations of these. The Website provides an information portal for these services through the California Department of Education. Low-power Atmospheric Compensation Experiment LACE. An experiment begun in the mid-1980s in which a spaceborne target with a single sensor was used to assess compensation schemes associated with laser beams traveling through the atmosphere from the ground. This information was needed to support laser defense system research and development. LACE was built by the U.S. Naval Research Laboratory (NRL). LACE was originally a fairly simple sensor system carried on a shuttle. In 1986, LACE became a full satellite instead of a set of sensors on a host satellite. By 1987, the sensor arrays carried a total of 210 sensors capable of characterizing ground-based laser beams. In 1990, the LACE satellite was launched and successfully demonstrated that techniques for compensating for atmospheric distortion of laser beams originating from the ground were tenable. low-power television LPTV. Television broadcast technology with limited power commonly used to serve a local region such as a rural community. Broadcast technologies are closely regulated by the Federal Communications Commission (FCC) and various spectra and licenses are granted to broadcast stations dependent upon operator qualifications, content, viewing audience, and the power and frequency of the communications. LPTV serves a large number of educational and social niche markets and small communities that may not be of interest to larger broadcasting agencies. See Communications Policy Project, Community Broadcasters Association, Federal Communications Commission. lower sideband suppressed carrier LSSC. A modulated carrier wave which has had part of the signal stripped away in order to save bandwidth. This lower sideband is rebuilt mathematically at the receiving end to recover the original signal information. See sideband. LP 1. linear programming. 2. low power. 3. low pressure. LPC See linear predictive coding. LPRF 1. low-power radio frequency. 2. low pulserepetition frequency. LPTV See low-power television. LRC See longitudinal redundancy check. LRF See laser range finder. LRN See Location Routing Number.

LRS line repeater station. LSB 1. See least significant bit. 2. lower sideband. See sideband. LSDU Link layer Service Data Unit. LSI A term in the semiconductor industry describing capabilities aggregated onto a single chip. See large scale integration. LSMA Large-Scale Multicast Applications. LSN 1. See Large Scale Networking group. 2. local signal number. LSOG See local service ordering guidelines. LSP See Local Services Provider. LSR See local service request. LSS loop switching system. See switching. LSSC See lower sideband suppressed carrier. LSSGR LATA Switching System General Requirements. LSTP 1. See local signal transfer point. 2. linear search & track processor. LSU 1. See line switching unit. 2. See Logical Storage Unit. LTB Last Trunk Busy. LTC See line trunk controller. LTE See Line Terminating Equipment. LTO See linear tape-open. LTS See loop testing system. LTSP See Linux Terminal Server Project. Lucent Technologies A company created subsequent to the AT&T/Bell divestiture. Lucent was created from the Bell Laboratories research staff, and a number of the electronics, network, and business communications groups, including Systems for Network Operators, Business Communications Systems, Microelectronics, and Consumer Products. See Barton, Enos. Lucent Technologies Canada Inc. A wholly owned subsidiary of Lucent Technologies, based in Ontario, Lucent Technologies Canada Inc. formed as a result of the restructuring of AT&T after the divestiture. Lucent began in Canada as part of AT&T Canada Inc. in 1984. LUF lowest usable frequency. lug 1. A projecting attachment point, especially for electrical circuits. See terminal. 2. An attachment added to the end of a wire which provides an eye, or forked end, which allows the wire to be more easily attached to a bolt under a binding screw. LUM See line utilization monitor. lumen A unit of light (luminous) flux equal to the light produced by one candle intensity on a unit area of a flat surface of uniform distance from the light source. luminance The luminous (light-emitting) flux reflected or transmitted from a source such as a TV screen or computer monitor. Sometimes called brightness. luminosity A ratio of light flux to its corresponding radiant flux at a specific wavelength, expressed in lumens per watt.

luminous flux The visible energy (light) produced per unit of time. See lumens.

Lugs are designed with eyes or forked ends to facilitate attachment to electrical terminals.

LUN See logical unit number. Luneberg lens A type of focusing lens used in antennas to increase gain for ultra-high frequency (UHF) transmissions. lurker A tongue-in-cheek Internet term for a computer user who reads the chat channels, newsgroups, and other public discussion areas without contributing to the discussion or revealing his or her presence online. Lurkers run the gamut from those who are new or simply busy and don’t have the expertise or time to contribute, to those who deliberately choose not to reveal their identities to hide or to protect their privacy (e.g., celebrities). Occasionally there is resentment of lurkers, as some forums have a community take-and-give philosophy, and those who take without giving are perceived as taking unfair advantage of the other participants. However, a high proportion of lurkers may be good; if everyone on the Internet felt compelled to express an opinion on every subject, the discussion groups would become useless through excess volume. Come to think of it, some already have. See handle, newsgroup, pseudonym. lux A combining word from luminance and flux. A basic metric unit for expressing illumination (equal to about 10 foot candles). The illumination on a onesquare-meter area on which the flux of one lumen is uniformly distributed. luxmeter A type of light-measuring instrument that records intensities. Light meters are commonly incorporated into cameras to help to determine aperture and speed settings. LTS lightwave transmission system. Transmission through a light-guiding medium such as fiber optics. LVD low voltage disconnect. See load distribution unit. LWER See LightWeight Encoding Rules. Lynch, Daniel C. (ca. 1940- ) Lynch organized the first TCP/IP Implementor’s Workshop in 1986, which later developed into Interop in 1988, a large gathering of Internet, network, and other telecommunications professionals. Lynch is also known for his role in the ARPANET transition from NCP to Internet Protocol (IP). He is a cofounder of

CyberCash, Inc. and has been a member of the Board of Directors since 1994. LZ77 See Lempel-Ziv. LZ78 See Lempel-Ziv. LZARI Lempel-Ziv arithmetic. A lossless compression and archiving utility developed by Okumura in 1988, based originally on LZSS, but which incorporated adaptive and static algebraic compression to encode characters and position fields, respectively. Thus, it is a statistical compressor, rather than a dictionary compressor as was its predecessor. LZARI was not the fastest archiver, but it had good compression performance. LZARI was later adapted into LHarc by Yoshizaki. See Lempel-Ziv, LHarc. LZB Lempel-Ziv Bell. A lossless variable-lengthcode compression scheme developed in 1987 by Bell, based upon LZ77 concepts. In terms of compression performance for text files, LZB is a little better than LZH and its predecessors, but not as efficient as the popular GZIP. LZB has fairly small memory requirements for decompression making it suitable for devices with limited memory resources. LZB 80 Linienzugbeeinflussung 80. A signaling system developed by the German Federal Railways. LZB systems are sold internationally for high-speed train systems control and safety. LZC A dictionary-based lossless compression scheme developed in 1985 by Thomas et al., based upon LZW, which is patented. LZC incorporates a variable-size pointer scheme. It dynamically monitors progress and can flush and rebuild the dictionary to suit the circumstances. As examples, Unix compress and MacCompress use the LZC algorithm. LZC is also used in some schemes to increase disk space availability by dynamically compressing stored files. (Don’t confuse this with the waveletrelated LZC developed by Thaubman and Zakhor.) See Lempel-Ziv-Welch. LZC layered zero coding. A rate-scalable encoding scheme described by D. Thaubman and A. Zakhor in 1994. LZC takes advantage of a strong correlation among subband coefficients, resulting in good image compression performance. LZC and its descendants have been used in a number of applications related to scalable image compression and have been incorporated into embedded wavelet-based video coders. (Don’t confuse this with the dictionarybased LZC developed by Thomas et al.) See wavelet. LZFG Lempel-Ziv-Fiala-Green. A fast, lossless compression scheme developed in 1989 by Fiala and Green (U.S. Patent #4906991), based upon LempelZiv LZ77 and LZ78 concepts. LZFG is a sliding window scheme with data stored in a modified trie (Patricia tree) data structure. The position of the text in the trie is output. LZFG has some speed benefits over LZJ. LZH See LHA. LZJ Lempel-Ziv-Jakobsson. A dictionary-based lossless compression scheme developed in 1985 by Jakobsson. It is based upon LZW containing pointers only, with the pointers able to point to anywhere

L

in the previous character data to indicate a substring. See LZFG. LZHUF Lempel-Ziv Huffman. The algorithm incorporated into the LHarc data archiving utility by Yoshizaki that replaces LZARI’s adaptive arithmetic coding with adaptive Huffman coding to improve the speed of LZARI (LZARI already had good data compression). With additional work, LZHUF evolved into LHarc. See LHarc, LZARI. LZMW A lossless compression scheme developed in 1984 by Miller and Wegman. While LZMW improved upon its predecessor LZ77 (Lempel and Ziv), there was so much interest in adapting LZ77 that LZMW was short-lived, superseded by LZH, LZB, and the efficient and popular GZIP.

LZP Lempel-Ziv prediction. A lossless dictionary and hash-based compression scheme developed in 1995 by Charles Bloom. Bloom designed the scheme to be fast, scalable, and retargetable. It is descended from LZ77 and shares some characteristics with LZNW and PPMCB. It is distributed for noncommercial use under a Public License. See Lempel-Ziv. LZR A lossless compression utility developed in 1981 by Roden et al. that does not have the window limitations of the earlier LZ77 scheme. Interestingly, an LZR scheme has been suggested for the compression of repetitive DNA sequences. See Lempel-Ziv. LZS See Lempel-Ziv-Stac. LZSS See Lempel-Ziv-Storer-Szymanski. LZW See Lempel-Ziv-Welsh.

m 1. abbrev. meter. See meter. 2. abbrev. milli-. See milli-. M 1. abbrev. mega-. See mega. 2. symb. mixed polarization (ITU). M bit, Mark bit, More bit In X.25 network data transmissions, a signal bit used to indicate that additional packets in a sequence are to be expected. A bit set to 1 or “true” indicates further packets will be coming, whereas 0 or “false” signals that packets were (intentionally) not sent. This helps the receiving system to distinguish between packets not sent and lost packets. In Realtime Transport Protocol (RTP), the M bit can signal the transport of at least one complete media frame or the remaining fragment in a frame. For frames fragmented across multiple RTP packets, the M bit can signal frame boundaries. See D bit, Q bit. M hop A type of pattern that results when communications transmissions are bounced from an Earth station to an airborne receiver, back to an Earth station or intermediary hub, up to an airborne receiver and back down to the final receiving station, thus

Basic hop

M

resembling the letter “M.” This is a common configuration in hub topology satellite communications. Newer satellites are being designed for intersatellite communication, so the signal goes from an Earth station to a satellite, to another satellite and then down to Earth again, thus forming a shape like three sides of a rectangle rather than the letter M, as shown in the Basic hop/M hop diagram. M port In a Fiber Distributed Data Interface (FDDI) network topology, this is an extra port on a concentrator used to attach other nodes in a branching tree topology. M ports can be on both single attachment and dual attachment concentrators. The M port is an addition to the basic attachment to the FDDI network. On a dual attachment station, a redundant link can be created by connecting the A and B ports on different concentrators on the M ports. On a single attachment concentrator, the M port may be connected to the S port. M ports are never connected to one another. The other end of the M port may be attached to a patch panel through a data grade cable.

M hop

The left diagram illustrates a basic hop to a satellite and another back to an Earth receiving station. The one on the right shows how the hops can be repeated to pass through an intermediate station or hub, and then to the final receiver. There may be a number of reasons for sending to an intermediate hub, including amplification, filtering of the broadcast channels, and redistribution to subscribers through Earth stations at more than one location.

M

ITU-T M Series Recommendations Scope, Philosophy, General Principles M.10

Scope and application of recommendations for maintenance of telecom. networks and services M.15 Maintenance considerations for new systems M.20 Maintenance philosophy for telecom. networks M.21 Maintenance philosophy for telecom. services M.32 Principles for using alarm info for maintenance of international transmission systems and equipment M.560 International telephone circuits – principles, definitions, and relative transmission levels M.1130 General definitions and general principles of operation/maintenance proced. to be used in satellite mobile systems M.1140 Maritime mobile telecom. services via satellite M.1301 General description and operational proced. for international SDH leased circuits M.1535 Principles for maintenance info to be exchanged at customer contact point (MICC) M.1537 Definition of maintenance info to be exchanged at customer contact point (MICC) M.3100 Generic network info model M.3600 Principles for management of ISDNs Numbering M.320 M.330 M.340 M.350 M.380 M.390 M.400 M.410

Numbering of channels in group Numbering of groups within supergroup Numbering of supergroups within mastergroup Numbering of mastergroups within supermastergroup Numbering in coaxial systems Numbering in systems on symmetric pair cable Numbering in radio-relay links or open-wire line systems Numbering of digital blocks in transmission systems

M.3604 Application of maintenance principles to ISDN primary rate access M.3605 Application of maintenance principles to static multiplexed ISDN basic rate access M.3610 Principles for applying TMN concept to the management of B-ISDN M.3611 Test management of B-ISDN ATM layer using the TMN M.3620 Principles for the use of ISDN test calls, systems, and responders M.3621 Integrated management of ISDN customer access M.3640 Management of the D-channel – data link layer and network layer M.3641 Management info model for management of data link and network layer of ISDN D-channel M.3650 Network performance measurements of ISDN calls M.3660 ISDN interface management services Monitoring, Maintenance, Performance, Service, Testing, Misc., etc. M.34 M.35 M.50 M.60 M.70 M.75 M.80 M.85 M.90 M.100 M.110 M.120 M.125 M.160 M.450 M.460 M.470 M.475

ISDN

M.495

M.3600 Principles for management of ISDNs M.3602 Application of maintenance principles to ISDN subscriber installations M.3603 Application of maintenance principles to ISDN basic rate access

M.496 M.500

Performance monitoring on international transmission systems and equipment Principles concerning line-up and maintenance limits Use of telecom. terms for maintenance Maintenance terminology and definitions Guiding principles on general maintenance organiz. for telephone-type international circuits Technical service Control stations Fault report points Sub-control stations Service circuits Circuit testing Access points for maintenance Digital loopback mechanisms Stability of transmission Bringing new international transmission system into service Bringing international group, supergroup, etc. links into service Setting up and lining up analog channels for international telecom. services Setting up and lining up mixed analog/ digital channels for international telecom. services Transmission restoration and transmission route diversity: terminology and general principles Functional organiz. for automatic transmission restoration Routine maintenance measurements to be made on regulated line sections

M.510 M.520 M.525 M.530 M.535 M.540 M.556 M.562 M.565 M.570 M.580 M.585 M.590 M.600 M.605 M.610 M.620 M.630 M.650 M.660 M.665 M.670 M.675 M.710 M.715 M.716 M.717 M.718 M.719 M.720

Readjustment to nominal value of a regulated line section (on symmetric pair line, coaxial line or radio-relay link) Routine maintenance on international group, supergroup, etc. links Automatic maintenance procedures for international group, supergroup, etc. links Readjustment to the nominal value of an international group, supergroup, etc. link Special maintenance procedures for multiple destination, unidirectional (MU) group and supergroup links Routine maintenance of carrier and pilot generating equipment Setting up and initial testing of digital channels on international digital path or block Types of circuit and circuit section Access points for international telephone circuits Constitution of circuit; preliminary exchange of info Setting up and lining up international circuit for public telephony Bringing international digital circuit into service Setting up and lining up circuit fitted with a compandor Organization of routine maintenance measurements on circuits Routine maintenance schedule for international public telephony circuits Periodicity of maintenance measurements on circuits Methods for carrying out routine measurements on circuits Maintenance of circuits using control chart methods Routine line measurements to be made on line repeaters of audio-frequency sections or circuits Periodical in-station tests of echo suppressors complying with Recommendations G.161 and G.164 Testing of echo cancellers Maintenance of circuit fitted with compandor Lining up and maintaining international demand assignment circuits (SPADE) General maintenance organiz. for international automatic and semi-automatic telephone service Fault report point (circuit) Fault report point (network) Testing point (transmission) Testing point (line signaling) Testing point (switching and interregister signaling) Network analysis point

M.721 M.722 M.723 M.724 M.725 M.726 M.729 M.730 M.731 M.732 M.733 M.734 M.760 M.762 M.800 M.810

M.820 M.830 M.850 M.880 M.900 M.910 M.1010 M.1012 M.1013 M.1014 M.1015 M.1016 M.1020 M.1025

System availability info point Network management point Circuit control station Circuit sub-control station Restoration control point Maintenance organization for wholly digital international automatic and semiautomatic telephone service Maintenance organization for international public switched telephone circuits for data transmission Maintenance methods Subjective testing Signaling and switching routine maintenance tests and measurements Transmission routine maintenance measurements on automatic and semi-automatic telephone circuits Exchange of info on incoming test facilities at international switching centers Transfer link for common channel Signaling System 6 Maintenance of common channel Signaling System 6 Use of circuits for voice-frequency telegraphy Setting up and lining up international voice-frequency telegraph link for public telegraph circuits (50-, 100-, and 200baud modulation rates) Periodicity of routine tests on international voice-frequency telegraph links Routine measurements to be made on international voice-frequency telegraph links International time division multiplex (TDM) telegraph systems International phototelegraph transmission Use of leased group and supergroup links for wide-spectrum signal transmission (data, facsimile, etc.) Setting up and lining up international leased group link for wide-spectrum signal transmission Constitution and nomenclature of international leased circuits Circuit control station for leased and special circuits Sub-control station for leased and special circuits Transmission maintenance point (international line) (TMP-IL) Types of transmission on leased circuits Assessment of service availability performance of international leased circuits Character. of special quality international leased circuits with special bandwidth conditioning Characteristics of special quality international leased circuits with basic bandwidth conditioning

M

ITU-T M Series Recommendations, cont. Monitoring, Maintenance, Performance, Service, Testing, Misc., etc., cont. M.1030 Character. of ordinary quality international leased circuits forming part of private switched telephone networks M.1040 Character. of ordinary quality international leased circuits M.1045 Preliminary exchange of info for provision of international leased circuits and international data transmission systems M.1050 Lining up international point-to-point leased circuit with analog presentation to the user M.1055 Lining up international multiterminal leased circuit M.1060 Maintenance of international leased circuits M.1150 Maintenance aspects of maritime/land mobile telecom. store-and-forward services (packet mode) via satellite M.1160 Maintenance aspects of aeronautical mobile telecom. service via satellite M.1170 Maintenance aspects of mobile digital telecom. service via satellite M.1230 Method to improve management of operations and maintenance processes in International Telephone Network M.1235 Use of automatically generated test calls for assessment of network performance M.1300 Maintenance of international data transmission systems operating in range 2.4 Kbps to 140 Mbps M.1320 Numbering of channels in data transmission systems M.1340 Performance objectives, allocat. and limits for international PDH leased circuits and supporting data transmission links and systems M.1350 Setting up, lining up and characteristics of international data transmission systems operating in range 2.4 to 14.4 Kbps M.1355 Maintenance of international data transmission systems operating in range 2.4 to 14.4 Kbps M.1370 Bringing-into-service of international data transmission systems M.1375 Maintenance of international data transmission systems M.1380 Bringing-into-service of international leased circuits that are supported by international data transmission systems M.1385 Maintenance of international leased circuits that are supported by international data transmission systems M.1400 Designation for inter-operator networks M.1510 Exchange of contact point info for the maintenance of international services and the international network M.1520 Standardized info exchange between administrations

M.1530 Network maintenance info M.1532 Network maintenance service performance agreement (MSPA) M.1539 Management of grade of network maintenance services at maintenance service customer contact point (MSCC) M.1540 Exchange of info for planned outages of transmission systems M.1550 Escalation proced. M.1560 Escalation proced. for international leased circuits M.2100 Performance limits for bringing-intoservice and maintenance of international PDH paths, sections and transmission systems M.2101 Performance limits and objectives for bringing-into-service and maintenance of international SDH paths and multiplex sections M.2101.1 Performance limits for bringing-intoservice and maintenance of international SDH paths and multiplex sections M.2102 Maintenance thresholds and procedures for recovery mechanisms (protection and restoration) of international SDH VC trails (paths) and multiplex sections M.2110 Bringing-into-service of internat. PDH paths, sections and transmission systems, SDH paths, and multiplex sections M.2120 PDH path, section and transmission system and SDH path and multiplex section fault detection and localization procedures M.2130 Operational procedures for the maintenance of transport network M.2140 Transport network event correlation M.2201 Performance objectives, allocations and limits for bringing-into-service and maintenance of international ATM virtual path and virtual channel connections M.3208.1 Leased circuit services M.3208.2 Connection management of pre-provisioned service link connections to form leased circuit service M.3208.3 Virtual private network M.4010 Inter-Administration agreements on common channel Signaling System 6 M.4030 Transmission characteristics for setting up and lining up transfer link for common channel Signaling System 6 (analog version) M.4100 Maintenance of common channel Signaling System 7 M.4110 Inter-Administration agreements on common channel Signaling System 7 Telecom. Management Network (TMN) M.3000 Overview of TMN Recommendations M.3010 Principles for Telecom. Management Network (TMN) M.3013 Considerations for Telecom. Management Network (TMN)

M.3016 M.3020

TMN security overview TMN Interface Specification Methodology M.3101 Managed object conformance statements for generic network info model M.3108.1 TMN management services for dedicated and reconfigurable circuits network: info model for management of leased circuit and reconfigurable services M.3108.2 TMN management services for dedicated and reconfigurable circuits network: Info model for connection management of preprovisioned service link connections to form reconfigurable leased service M.3108.3 TMN management services for dedicated and reconfigurable circuits network: Info model for management of virtual private network service M.3120 CORBA generic network and NE level info model M.3180 Catalog of TMN management info M.Imp3100 M.3100 TMN Implementors’ Guide – defects and resolutions (M.3100 Series) M.3200 TMN management services and telecom. managed areas: overview M.3207.1 TMN management service: maintenance aspects of B-ISDN management M.3210.1 TMN management services for IMT-2000 security management M.3211.1 TMN management service: Fault and performance management of ISDN access M.3300 TMN F interface requirements M.3320 Management requirements framework for TMN X-Interface M.3400 TMN Management Functions Supplements M.Sup1.1 Prefixes used in decimal system M.Sup1.2 Transmission measure. conversion tables M.Sup1.3 Normal (or Laplace-Gauss) distribution M.Sup1.4 Methods of quality control M.Sup1.5 Mathematical processing of measure. results of variations of overall loss of telephone circuits M.Sup1.6 Statistical theory require. M.Sup2.1 General observations concerning measuring instruments and measuring techniques M.Sup2.10 Method for measuring frequency shift introduced by carrier channel M.Sup2.11 Rapid verification test for echo control devices M.Sup2.12 Automatic data acquisition and effective processing proced. for group and supergroup pilot levels

M.Sup2.13 Loop method for maintenance of 4-wire telephone-type leased circuits M.Sup2.14 Automatic measuring device for carrier systems with large number of channels M.Sup2.15 Detection of circuit faults M.Sup2.16 Receiving relative levels at renters’ premises for international leased circuits used for data transmission M.Sup2.17 Results of investigation of service availability performance of international leased circuits made in 1982 M.Sup2.2 Measurements of loss M.Sup2.3 Level measurements M.Sup2.4 Measure. of crosstalk M.Sup2.5 Measuring errors and differences due to impedance inaccuracies of instruments and apparatus. Use of decoupled measuring points M.Sup2.6 Errors in indications given by levelmeasuring instruments due to interfering signals M.Sup2.7 Measure. of group delay and groupdelay distortion M.Sup2.8 Measure. of sudden phase changes on circuits M.Sup2.9 Vibration testing M.Sup4.10Transient analog circuit impairments and effect on data transmission M.Sup4.1 Stability of overall loss and psophometric noise: results of routine maintenance measurements made on international network during first half of 1978 M.Sup4.2 Results and analysis of 10th series of tests of short breaks in transmission M.Sup4.3 Character. of leased international telephone-type circuits M.Sup4.5 Instructions for making future measurements of transmisison quality of complete connections for recording results of measurements M.Sup4.8 Results and analysis of tests of impulsive noise M.Sup4.9 Weighting of measurements relating to stability of circuits in international network according to size of circuit groups M.Sup4.7 Instructions for making future measurements of transmission quality of international circuits and international centres and for recording results of measurements M.Sup5.1 Requirements for transmission of television signals over long distances M.Sup5.2 Setting-up and testing of international videoconference studios M.Sup6.1 Effect on maintenance of introduction of new components and modern equipment design M.Sup6.2 New operation and maintenance organization in Milan Italcable intercontinental telecommunications center

M

M Series Recommendations A series of ITU-T recommendations providing guidelines for TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits. These guidelines are available as publications from the ITU-T for purchase. Since ITU-T specifications and recommendations are widely followed by vendors in the telecommunications industry, those wanting to maximize interoperability with other systems need to be aware of the information disseminated by the ITU-T. A full list of general categories is listed in Appendix C and specific series topics are listed under individual entries in this dictionary, e.g., L Series Recommendations. See M Series Recommendations chart. M-ary A designation useful in assessing relative capacities in multilevel modulation schemes. M is used as the symbol for arithmetic equivalencies to represent the number of bits per symbol. Thus, in Mary signaling, a symbol represents n bits, with M signal states, with M = 2n. In turn, the number of symbols per second determines the baud rate. This can further be extrapolated to calculate capacity in relation to bandwidth. M-quad, mini-quad A compact version of a quad antenna used for single or multiband radio communications. See quad antenna for a fuller explanation. M-patch bay According to the Federal Technology Service (FTS), a patching system for monitoring and patching (interconnecting) digital data circuits at signaling rates from 1 to 3 Mbps. Ma Bell colloq. A term to familiarly describe the Bell telephone system, and later AT&T. The Bell system was so ubiquitous and so well recognized that many came to refer exclusively to the corporation as Ma Bell. MAA See MAC Access Arbitration. MAC 1. See mandatory access control. 2. Media Access Control. In a layered network architecture, the lower half of the data-link layer that governs access to the available IEEE and ANSI LAN media. See Media Access Control for a fuller explanation. 3. See Message Authentication Code. 4. See multiplexed analog component. MAC Access Arbitration MAA. In a layered network operating as a broadband fiber network (e.g., cable modem services), the Media Access Control (MAC) Access Arbitration is a sublayer which, along with associated sublayers, facilitates multiplexing and Quality of Service (QoS). See Media Access Control. MAC address Media/Medium Access Control address. A network location identifier. See Media Access Control. Mac OS 7.6 A widespread version of the Macintosh operating system still used by millions of endusers and supported by many developers well into the year 2000, even though OS 8.6 and its successors had been available for a few years and would eventually supersede it. One of the reasons for the longevity of 7.6 was its relative stability and its networking capabilities. Another reason was that honest users of

software, with large installed bases of programs, could not easily move to OS 8.x and above without upgrading their many commercial/shareware programs, a move that could cost many hundreds or even thousands of dollars per machine (especially for graphics and desktop publishing software). A final reason for the popularity of OS 7.6 was its ability to run on older Macs, tens of thousands of which were still in active use for word processing, emailing, fax modeming, and home automation applications (good low-resource applications that run well on old computers). Mac OS 8.5 Code-named Allegra, and coexistent with the Rhapsody environment, this was a major Macintosh Operating System release (with upgrades and patches to bring it up to 8.6) that became wellestablished in the late 1990s. This release of the operating system featured a more polished looking interface, better native graphics support, and increased support for Internetworking, as well as enhanced memory and file transfer capabilities. It was still being widely used in 2001 concurrently with Mac OS 9 and Mac OS X. Mac OS 9 A new version of the Macintosh operating system announced in 1999 to supersede the OS 8.x line. With OS 9 came Sherlock 2, a Web-compliant searching tool, multiple-user environments (in the sense that more than one person could use the same Mac and keep preferences, file settings, etc. personalized and protected), voiceprint passwords, Internet file serving capabilities, Internet AppleScript automation tools, and more. In general, this release of the operating system brought the Macintosh operating system into the world of the Internet and made many aspects of the system customizable and more secure. Mac OS 9.1 was announced in 2001 to provide an update to 9.0 and a transition to Mac OS X (which became prevalent by 2002). Mac OS X Macintosh Operating System Ten. Announced in May 1998, this new version of the Macintosh OS was scheduled to ship to developers in early 1999 with an original planned public release in Fall 1999 and an actual release in 2001. The system supports pre-emptive multitasking, advanced virtual memory, and memory protection, optimized for Apple’s G3 PowerPC computers. OS X is built upon Darwin, the open source model core based on FreeBSD and Mach 3.0 technologies. Darwin is processor-independent and supports PowerPC- and Intel-based desktop computers. Thus, Open Source developers can create applications capable of running on a variety of hardware platforms. At the time OS X was released, the installed base of Macintosh platforms was over 25 million. Apple expected most existing Macintosh applications to run on OS X without alteration (though in practice this was not entirely so). Mac OS X.1 improved printing and networking capabilities as well as CD and DVD authoring capabilities. A new, aesthetically appealing user interface called Aqua was introduced with the Mac OS X system. Aqua included a new Finder and NeXT-like Dock to enable the desktop to be customized for quick access

to commonly used applications. Aqua is built upon graphics technologies for the multimedia world, including OpenGL, Quartz, and QuickTime. See QuickTime. macadamize To pave using bituminous binding materials. The process was named after John L. McAdam, who developed road improvement techniques during the American Revolution. The paving of roads significantly enhanced the speed of communications, since most messages at the time travelled only as fast as the people or horses carrying them. MACE Macintosh Audio Compression and Expansion. MACE is built into the Macintosh OS Sound Manager utility. Mach line, Mach surface The division between regions of supersonic and subsonic flow. Mach-Zehnder interferometer See interferometer. machine dependent Software or peripherals designed to work on a specific system or architecture, and not readily usable on other systems (although sometimes modifications can be done). Low-level routines written to take advantage of a particular chip architecture or peripheral card are machine dependent. Most software executables are machine dependent, since they have usually been compiled from a higher level language down into low-level machine code for a specific system. machine language A symbolic computing machine control language that functions at the lowest level possible on a system, in symbols readily understood by the computer, but inscrutable to most people. Machine language involves the most basic movement and processing of data, in terms that are specific to the computer architecture (usually binary). Thus, move and add instructions are used frequently in machine language programs. A move instruction transfers data between registers, and an add instruction performs a math operation (add, multiply, subtract, etc.). Because machine language programs are cryptic, long, difficult to follow, difficult to read, and difficult to debug, assemblers were developed to codify and organize instruction sets so software could be written and debugged more quickly. Assembly language or assembler was a step up from machine language in that it used symbols to encode instructions that would then be translated into machine language. Assembler was easier to code and debug than machine language, but the listings were long and many people had difficulty with the symbology and tedium. Later, higher level languages such as FORTRAN, BASIC, LISP, C, Modula, Perl, Java, etc. were added to make the task of programming easier still, and to adapt programming languages to specific types of tasks. Some higher level languages are compiled into machine language executables that can be run directly thereafter, and others are interpreted into machine language at the time an instruction is processed. Compiled languages typically run many times faster than interpreted languages because the conversion

to machine instructions happens only once, prior to writing the program. This machine language compiled executable is then stored as a file and used as needed. With faster processors, interpreted languages, which also have some advantages, such as direct feedback without compilation waiting times, have remained popular. Machine language coding is rare these days except for specialized coding.

The Macintosh Plus had a cute, portable all-in-one design, featuring a monochrome monitor, two serial ports, SCSI controller, graphical user interface, mouse, and networking capabilities through AppleTalk as standard features.

Macintosh A family of Motorola 68000-based personal computers developed and distributed by Apple Computer, Inc. The first of the Macintosh line was the Lisa computer, introduced in 1983. Its graphical operating system was described as radical by many. There were also vocal detractors who said “graphics interfaces will never be accepted in office environments.” A graphical interface may not seem unusual now, but at the time, computers were almost exclusively text-based, and this new graphical user interface, which was accessed with a mouse, seemed extraordinary. Many business and computing professionals recoiled in suspicion. In retrospect, now that virtually all computers have graphical user interfaces, the harsh criticisms leveled at the Macintosh graphics now appear shortsighted. The Macintosh graphical operating system was inspired by some of the brilliant research and development that was occurring in the 1970s and early 1980s at the Xerox PARC facility in California. The fledgling founders of Apple Computer were given a tour of the facility, and Steve Jobs came away energetically inspired by what he had seen, determined to add a new line of computers different from the Apple II line. Unfortunately, while the Lisa was a good machine and most of its characteristics were later incorporated into the more familiar Macs, the initial price tag was high and it didn’t sell well. The early Macintosh computers familiar to most people started with the Mac in 1984, followed by the Mac Plus and various subsequent Macs (there are now dozens of models). The

M

1984 release of the 128K 32-bit 4.7 MHz “little Mac” was accompanied by a significant product in 1985, the Apple Laserwriter. This new laser printer changed

the way many people thought about computers. Since 10-pin dot matrix printers with extremely limited fonts were prevalent at the time, few had considered

Overview of Apple Macintosh Evolution Model

Year

Speed

Processor

Notes

Lisa (Mac XL)

1983

5 MHz

68000

First PC GUI. Not a big seller.

Macintosh

1984

4.77 MHz

68000

128K consumer machine.

Macintosh Plus

1986

8 MHz

68000

Launched DTP industry.

Macintosh II

1987

16 MHz

68020

First of many successful Mac IIs

Macintosh IIx

1988

16 MHz

68030

68882 math copro.

Macintosh IIcx

1989

16 MHz

68030

68882 math copro.

Macintosh SE/30

1989

16 MHz

68000

68882 math copro.

Macintosh SE

1987

8 MHz

68000

Macintosh IIci

1989

20 MHz

68030

One of the best and most reliable of the Mac II line; 68882 mathco.

Macintosh IIfx

1990

50 MHz

68030

Intended as a fast graphics machine, but it didn’t sell widely.

Macintosh LC

1990

16 MHz

68020

Macintosh Classic

1990

8 MHz

68000

Low-cost nostalgic release.

Macintosh IIsi

1990

20 MHz

68030

Optional 68882 math copro.

Mac. Classic II

1991

16 MHz

68000

Optional 68882 math copro.

Macintosh IIvi

1992

32 MHz

68030

Optional 68882math copro.

Macintosh IIvx

1992

32 MHz

68030

With 68882 mathco.

16 MHz

68030

Macintosh LC II Mac. Color Classic

1993

Macintosh LC III Mac. Centris 610

1993

33MHz

68030

Optional 68882 math copro.

25 MHz

68030

Optional 68882 math copro.

20 MHz

68040

Mac. Centris 650

1993

25 MHz

68040

Mac. Quadra 800

1993

33 MHz

68040

Mac. Centris 660

1993

25 MHz

68040

1 NuBus slot.

Mac. Quadra. 840AV 1993

40 MHz

68040

Tower. DSP. 3 NuBus slots.

PowerMac 6100

1994

60/66 MHz

PowerPC 601

Major evolution from Mac line to PowerMacs.

PowerMac 9500

1995

120 to 200 MHz

PowerPC 604/

PowerMac G3

1997

233 to 333 MHz

604e/dual604e

PCI slots.

PowerPC 750

iMac

1998

233 MHz

PowerPC 750

PowerMac G4

1999

350/400 MHz

MPC 7400

New designer look

iMac DV

2000

400 MHz

PowerPC 750

iMac SE

2001

600 MHz

PowerPC 750cx

iBook

2001

500/600 MHz

PowerPC 750cx 4.9 lb. portable

PowerBook G4

2001

550/667 MHz

PowerPC 7450

5.3 lb. portable

the potential of personal computers as publishing tools. With the Laserwriter and Adobe Systems PostScript fonts, publishers sat up and took notice and the desktop publishing industry was born, with very substantial repercussions to the traditional layout and printing industry that are still reverberating today. New all-digital presses are completely changing the way printed information is produced. The Macintosh line became the preferred system in print publishing service bureaus in the late 1980s, and many of the high-end desktop publishing and graphics programs were available only for the Mac. It was not until the early 1990s that some of these important software programs were ported to Intelbased machines, and service bureaus began to use both platforms. Almost 30 million Macintosh computers had been shipped since 1984, 79% of which were still in use, yet detractors continued to predict the demise of Apple and the Macintosh line (a prediction begun with the first introduction of the Mac line 14 years earlier). The first major change in the Macintosh line was the changeover to PowerMacs in the 1990s. In 1997, to the surprise of many, Steve Jobs took the position of interim CEO and later CEO and injected a sense of excitement into what had become an almost lackluster company. This change came about with the evolution from PowerMacs to G3s late in 1997. With the introduction of the iMacs in a variety of designer colors and styles, the Macintosh attracted a new generation of users. By 2000, Macintosh laptops had become competitive with the introduction of new models, including the iBooks and full-featured Titanium model. In July 2001, the G4 line was introduced, along with updates to the Mac OS X operating software. The portable models are particularly important to telecommunications since they are often integrated with handheld communications devices for business communications and favored for writing and reporting by journalists. While the early Mac hardware was not inherently suited to video, it was popular for audio applications and many musicians adopted the Mac for the composition of electronic music. The Amiga was the preferred platform for video from the mid-1980s to the mid-1990s, until Commodore support for the Amiga dwindled, and then the desktop video market split onto Intel and Macintosh platforms. As the Macintosh hardware evolved, audio/visual capabilities were increasingly incorporated into the basic hardware, with high-quality stereo sound capabilities and some video capabilities built into A/V (audio/visual) models. This was important in maintaining the platform’s viability in a market demanding greater graphics and sound capabilities for games, publishing, and multimedia/Web production. The Macintosh Overview chart doesn’t include a complete list of Macintoshes and their features, as there are now dozens of models, but some of the Macintosh evolution can be seen through the desktop models summarized in the Overview of Apple Macintosh Models chart.

MacMICA A Macintosh-based multipoint videoconferencing program from Group Technologies, which works over AppleTalk networks. See Cameo Personal Video System, Connect 918, CU-SeeMe, IRIS, Visit Video. MacMiNT A text-based, Unix-like operating system ported from the Atari ST to the Macintosh. It can be used with freely distributable Unix utilities such as GCC, GDB, make, tcsh, perl, etc. macro A programming routine or script that “bundles” or combines a number of steps, processes, operations, or other actions. Macros are typically used as time-savers for frequently performed functions. Scriptable macros are usually written in text editors, with simple BASIC-like commands. There are many different macro scripting languages, often developed to automate functions in a particular application such as a database or paint program. Some macros are recordable; in other words, the user turns on a record feature in the software, then performs a number of operations which are to be used frequently in the same sequence, then turns record off and gives the macro a name. The sequence of events is stored and can be invoked later with a name or hot-key sequence. Batch and job control languages can be used to write macros. Perl is a good programming language for writing powerful macros for many types of applications, including Web site automation. macrobend A significant bend in an optical fiber. Optical fibers are quite slender and somewhat flexible, but due to the nature of the transmission of light, they do not have the small-radius 180° (or more) bending capability of many types of wire and care must be taken not to snap or significantly stress the structure of the fibers because this will compromise their transmission capabilities. Macrobends can be found in installations where the fiber must go around corners to reach the locations desired or may occur in fiber splicing trays. The degree of bend possible and considered significant depends upon the radius of the bend and the thickness (core diameter) and composition of the individual fiber(s), on the one hand, and the length of the waves in relation to the diameter of the fiber, on the other. When the radius of curvature of a fiber is large compared to the diameter of the fiber core, macrobend losses may occur. See macrobend loss, microbend. macrobend loss Signal attenuation through absorption in an optical fiber transmission caused by curvature or macrobend in the fiber. The amount of loss is due to many factors, including distance, the diameter and composition of the fiber core, and the wavelength of the optical transmission. Slender fibers are generally more susceptible to bend losses than thicker fibers. Longer wavelengths tend to be more susceptible than shorter wavelengths. As the bend increases, the mathematical/physical relationship between the wavelengths “bounced” along within the fiber core is changed and a critical angle is reached at which the light waves exit the fiber and are lost. Macrobend loss may be reduced by increasing the

M

core diameter of the fiber, but there is a tradeoff with fiber sensitivity, weight, cost, and the capability of the fiber to bend physically. See attenuation, macrobend. macroblock sampling A compromise technique used in video phone systems to provide a recognizable image in spite of slow transmission media. Standard telephone modems are too slow for full-screen, full-motion video images. By using an averaging system to sample the image, the image information can be sent more quickly. The smaller the blocks and the more frequent the sampling, the better the image fidelity, but the slower the processing. An alternative to macroblock sampling is wavelet video compression, which may provide better images through frame-by-frame compression. MAE 1. See Metropolitan Area Ethernet. 2. See Merit Access Exchange. MAE East The largest Metropolitan Area Exchange, located in Washington, D.C. The MAE is a ring system which provides Internet Service Providers (ISPs) with a relay point for exchanging packets with friendly systems through switched and shared Fiber Distributed Data Interface (FDDI) and switched Ethernet communications services. A MAE is, in a sense, a gargantuan wiring closet with thousands of lines of cables, switches, routers, and connections interconnecting many public and private network installations. The MAE system provides access and interconnections, but doesn’t provide ISPs with political connections with the other services on the system. These have to be individually arranged by each ISP. See MAE West. MAE West A Metropolitan Area Exchange established in 1988 in San Jose, California, providing switched and shared Fiber Distributed Data Interface (FDDI) and switched Ethernet communications services. Originally operated by Metropolitan Fiber Systems, MFS merged with Worldcom Communications in the mid-1990s to provide expanded nationwide services. MAE West interconnects with the Ames Internet Exchange (NASA) and well-known networks like CERFnet, BBN Planet, MCI, and others. See MAE East. Magellan The name of a prominent Web-based Internet search system. magic signature A file integrity mechanism built, for example, into PNG graphics files to detect file corruption. The signature is typically incorporated into the file header or the early part of the file image. Different levels of sophistication can be designed into magic signatures, with different byte lengths. See cyclic redundancy check. magic wand colloq. A selection tool commonly implemented in computer painting and drawing programs. The “wand” is usually configured to select a specific color or level of gray and may include tolerances to select nearby values as well. It is useful for selecting objects to be modified or for excluding parts of an image that must be protected from being modified. Magic Wand In navigation and location applica-

tions, an electronic device proposed by Egenhofer and Kuhn for geographical information system applications. The Magic Wand would incorporate a Global Positioning System (GPS) receiver and a gyroscope to provide location and orientation information relative to the position and orientation of the wand. This information could be cross-referenced with a knowledge base including a digital terrain base enabling the user to find out information on a topographic feature being queried (e.g., a specific mountain). With a cell phone connection to the local area network or the Internet, the possibilities become vast, with the capability of user public information servers to fill in further details on the features pointed to with the Wand. Magic WAND Magic Wide Area Network Davis. A project to promote wide area networking in the University of California, Davis, campus community, especially to off-campus locations that serve its staff and students. The project was initiated in 1997. Magic WAND Magic Wireless ATM Network Demonstrator Project. A joint European ACTS project to extend ATM network access transparently to mobile communications users. It is one of the larger ACTS projects. The project endeavors to specify, demonstrate, and promote standards for a wireless access system that retains the benefits of multimedia wired ATM networks. The project was described in the mid-1990s with trials and workshops conducted in 1998. Communication was aimed to be in the 5-GHz frequency range at transmission speeds of about 20 Mbps at ranges up to about 50 ms. Documents describing the project are available for public download. http://www.tik.ee.ethz.ch/~wand/ Magic WAND network A global community support group, initiated in 1996 in Japan by the mother of a disabled child to help others in similar situations through mutual support and communication. The network is also called Community-Based Rehabilitation. Magic Wand Speaking Reader A Texas Instruments (TI) product released in the early 1980s. It incorporated text-to-speech capabilities for bar codereadable electronic books for children. After passing bar code readers over the bar code, the Magic Wand Speaking Reader would string stored allophones (speech units) together to generate a spoken message. magnesium oxide A material suitable for insulating against water and heat when compressed around a conducting wire. When used in conjunction with copper wires, it is known as mineral-insulated copper-sheathed (MICS). magnet 1. A body, person, or situation with attracting properties. It is called charisma when a person has “magnetic” qualities. 2. A body that produces an external magnetic field which can attract magnetic materials such as iron. Natural magnets are known as lodestone. Magnetic properties were described by the Greeks at least as early as 60 B.C. Steel will hold magnetic charges for a long time; iron can be magnetized, but retains the magnetism to a lesser degree

than steel, as do nickel and cobalt. Materials that magnetize readily, but lose the property quickly, are useful as cores for various electrical devices. Magnets are used in many industrial applications, generators, monitors, speakers, compasses, and many more. See electromagnet, gauss, lines of force, lodestone, magnetic field, solenoid. magnetic bubble memory A form of magnetic storage in which the digital data are stored in “bubbles,” small circular regions called magnetic domains on a thin film of magnetic material that is selectively polarized. Since the presence or absence of a bubble can be used as a binary toggle, ones and zeroes are easily represented. Magnetic bubble memory is nonvolatile through permanent magnets; the stored information is retained when the system is powered off. Magnetic bubble memory was used in the early 1980s when other types of storage were expensive and unreliable, but was superseded by random access memory (RAM), floppy diskettes and hard drives by about the mid-1980s. Newer forms of bubble memory use circuits associated with crystals, an evolution of the older magnetic bubble memory that is not destructively read and rewritten. See magnetic core memory, random access memory. magnetic circular dichroism MCD. Dichroism means two colors. Circular dichroism (CD) is a phenomenon occurring when optically active matter absorbs circularly polarized light with a slight difference in left- and right-handed directions. In terms of polarization, it has the character of “ellipticity” (a phenomenon distinct from optical rotation) and occurs in certain asymmetric materials. Dichroic minerals may appear to be different colors depending upon the angle at which they are viewed. A spectropolarimeter can be used to measure CD. Nunes et al. have suggested the use of coherent laser-induced thermal grates for ultraviolet circular dichroism spectroscopy. Magnetic circular dichroism is exploited in various spectrometry and X-ray technologies and is useful in exploring the properties and origins of magnetism. magnetic core memory A type of random access memory developed at MIT in the late 1940s and early 1950s. Jay Forrester was head of the Whirlwind computer project, a system built for realtime control applications that spawned core memory technology when vacuum tube systems were still prevalent. Magnetic core memory consists of an array of ferrite toroids (cores) with wires passing through toroids at each junction in the array, each of which represents a bit of memory. These toroid bits can be stimulated by current of sufficient intensity to alter the magnetic polarity of a specific point in the array, which can thus be made to toggle between two polarized states to represent binary ones and zeroes. The array configuration makes it possible to pinpoint a specific toroid by its X and Y coordinates and modify the polarity by running a portion of the current through a wire in each axis, thus not changing the positions surrounding the selected toroid but running sufficient current through the selected toroid to

change its state. Like magnetic bubble memory, magnetic core memory is nonvolatile; it retains its data if the system is powered off. By the 1970s, core memory was being gradually replaced by semiconductor technologies except for a number of specialized scientific applications. See magnetic bubble memory, random access memory. magnetic detector A device designed to receive electromagnetic waves, pioneered by Rutherford and further developed by G. Marconi. The magnetic detector comprises a small induction coil with primary and secondary coil windings surrounding a glass tube with a soft iron wire, rather than the usual common soft iron core. The wire is connected to itself in a loop that runs outside the glass tube and coil windings and is set to move continuously through the tube. A magnet is installed near the secondary (outer) winding, adjacent to the circulating wire. This fairly sensitive detector was used in conjunction with early telephone receivers, but never came into wide use and had almost disappeared by the early 1900s. See detector for illustrations. magnetic disk A circular device coated on the surface with magnetic particles that can be rearranged to encode information. A number of computer storage devices, including floppy disks, cartridges, and hard drives, use magnetic disks. The disk shape is favored because it allows the disk to be rotated very rapidly under a read/write head. By controlling the position of the read/write head, fast access to any portion of the recording surface can be achieved, called random access. Early magnetic floppy disks were vulnerable to damage because they had an opening for the read/write head where the disk might be inadvertently touched or scratched, and pliable coverings that could be bent, thus damaging the disk. With the commercial introduction of the 3.5-in. floppy diskette around 1983, these sources of trouble have been removed. The chief disadvantage of magnetic disks is that they can be damaged by exposure to magnetic sources (be careful to keep them away from monitors and speakers), which gives them a somewhat limited shelf life. See gamma ferric oxide, superparamagnetic. magnetic equator Similar to, but not coincident with, the Earth’s geographic equator; also called the aclinic line as it is the point at which a dip needle is at zero (90°), between its two vertical positions. See agonic. magnetic field The region of external influence associated with an electromagnetic body in which these forces can be detected or exhibit a measurable influence on magnetic materials or instruments. The intensity of a magnetic field is described in terms of the number of lines of force passing through a specified area, although the field is conceptualized as continuous. The influence of a magnetic field can be seen by holding a magnet near small magnetic objects. A magnetic field can be induced in certain materials by running current through them. See flux, gauss, lines of force.

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Magnetic lines of force, as illustrated here, vary according to the shape and properties of a particular magnet. These lines are not fixed in space; rather they are suggested by the orientation of iron filings and other substances which can be sprinkled over the magnet on a contrasting surface to visually represent the influence of the magnetic field. These lines are conceptualized as extending indefinitely.

magnetic field modulation MFM. A means of modulating a magnetic field very close to the recording surface of an optical disc such that the polarity of the magnetic field can be switched at very high frequency. This produces marks on the recording portion of the disc that are narrow and tall (crescents), enabling higher bit densities per unit area and, as such, the density is no longer limited by the wavelength of the laser reading the data after it has been recorded. The crescent-shaped aperture is formed between a front and rear (double) mask and crosstalk is reduced by this arrangement. High-speed polarity changes enable the disc to be written in a single pass, thus significantly increasing write speeds. In earlier optical disc writing technologies, the magneto-optical coil had to be larger because of its distance from the recording surface. This limited the switching frequency due to magnetic inductance in the coil and hence the recorded marks on the disc could not overlap, limiting areal density. With MFM write mechanisms, the bit density is limited not by the wavelength of the laser, but by the ability of the mechanism to resolve the individual marks in the recorded surface. Heat applied to the read-out layer which magnifies the data in the recorded layer provides higher resolution and supports increased disc capacity. By using a mask in conjunction with the temperature distribution in the recording layer, individual bits can be isolated even if the laser light covers more than one mark. Newer laser technologies (e.g., blue lasers) will likely increase resolution even further. In combination with MFM, higher-resolution lasers will support very high capacity magnetic super resolution (MSR)

discs. See overcoat-incident recording, surface-array recording. magnetic induction The characteristic of certain permeable substances to become magnetized when placed near a magnetic source, without coming in direct contact with that source. Thus, a steel bar does not necessarily have to touch a magnet to be magnetically influenced by that magnet, or to influence other materials in the vicinity of the bar by induction. See lines of force, magnet, magnetic field, magnetic super resolution. magnetic ink character recognition MICR. A system introduced to the American Bankers’ Association in 1956, to recognize printed characters impressed with magnetic oxide ink. The most common use is to identify bank checks, thus automating transactions. It works even if ordinary ink, rubber stamp ink, or other pigments are superimposed on the magnetic particles. magnetic north The northerly direction in the Earth’s magnetic field near, but not corresponding to, the north geographic pole, to which north direction-seeking poles of magnets are attracted. Thus, what is called magnetic north is actually Earth’s south magnetic pole, located in northern Canada, since the north-labelled compass needle will orient itself toward the south pole of the Earth. See declination. magnetic storage A medium designed so magnetic materials within it can be dynamically aligned and realigned to hold encoded data. Floppy diskettes, hard drives, and audio/data tapes are various forms of magnetic storage. Magnetic storage is inexpensive and very convenient in that it can be easily rewritten; however, it is subject to loss over time through superparamagnetic phenomena, and may be damaged by proximity to equipment with magnetic components, such as monitors. See bulk eraser, superparamagnetic. magnetic stripe Typically a narrow strip on a portable medium such as a bank card or ID card, which is encoded with information of use to the cardholder. When inserted into a magnetic stripe reader, such as a cash machine, the information is used by the system as authorization for access and various transactions. magnetic super resolution, magnetic-induced super resolution MSR. A technology for enabling very high storage capacities on magneto-optical media. MSR capacities can be up to ten times the bit density of earlier mechanisms. MSR is based on IRIS Thermal Eclipse Reading (IRISTER) technology, developed by Sony in 1991. Vendors such as Fujitsu introduced commercial versions in the mid-1990s, based on land groove recording techniques. They could hold 2 Gbytes on a single-sided disc and 4 Gbytes on a double-sided disc and be read by existing magneto-optical drives. See magnetic field modulation for a fuller explanation. See GIGAMO, land groove recording. magnetic tape A narrow, very long magnetic sequential data encoding medium used for audio tapes and

computer data backup tapes. In the late 1970s and into the early 1980s, magnetic tape storage was commonly used on microcomputers for storing and retrieving applications programs and data. Due to its slow, sequential nature, tape drives were soon superseded by 8-in. floppy diskette drives, except for backups or specialized applications. magnetite A form of iron ore, readily magnetized, called lodestone when it is already magnetic as it comes out of a mine. See magnet, lodestone. magneto An apparatus in which a magnet is introduced into the proximity of a wound helix or coil of conductive wire (usually copper) to stimulate a momentary electric current which changes direction when the magnet is withdrawn. Similarly, a magnetizable material may be associated with a coil and periodically stimulated by a magnet to produce the same effect. This is a simple magneto-electric machine. An alternator is a common application of a magneto that employs permanent magnets to generate ignition current for engines. The discovery of magneto effects was an important step in telecommunications history. A. Graham Bell described its significance in a letter written in August, 1875: “... the discovery of the Magneto – electric current generated by the vibration of the armature of our electro magnet in front of one of the poles – is the most important point yet reached.... ... I feel sure that the future will discover means of utilizing currents obtained in this way – on actual telegraph lines. I think some steps should be taken immediately towards obtaining a Caveat or Patent for the use of a Magneto-Electric Current.... specially as a means of transmitting simultaneously musical notes differing in intensity as well as pitch. I can see clearly that the magneto-electric current will not only permit of the actual copying of spoken utterance, but of the simultaneous transmission of any number of musical notes (hence messages) without confusion. The more I think of it the more I see that the method of making and breaking contact so many times per second – is only the first stage in the development of the idea. When we can create a pulsatory action of the current which is the exact equivalent of the aerial impulses – we shall certainly obtain exactly similar results. Any number of sounds can travel through the same air without confusion – and any number should pass along the same wire. It should even be possible for a number of spoken messages to traverse the same circuit simultaneously; for – an attentive ear can distinguish one voice from another – although a number are speaking together.” Historically, this letter shows the transitional period in Bell’s thinking about telegraphy and the potential for telephony. Even though he mentions the “copying of spoken utterance,” his main focus was sending a variety of coded tones over telegraph wires (a

harmonic telegraph), not exclusively sending voice over phone lines. Since there were long debates over who invented the telephone and Bell retroactively claimed to have worked out telephone ideas a year before writing this letter, there are still questions as to whether Bell had actually sent voice transmissions over wires when he filed his famous harmonic telegraph “telephone” patent. Bell’s first public demonstration of intelligible speech was not until 1876, with an instrument that worked in part due to the addition of a magneto-induction device. Clearly the magneto was recognized by Bell as an important discovery during this transitional period and was likely a key component in turning the harmonic telegraph into a voice-carrying telephone. Bell’s interest in magnetos was well-founded and shared by a number of inventors, some of whom had built magneto machines in the early 1870s. By the late 1870s, magnetos were being developed into small generators to create electricity for low-power appliances, including phone bells. The magneto enabled a subscriber to ring the operator by turning a crank on the phone to provide the necessary power. Thomas Edison shared Bell’s interest in magnetos, patenting a number of dynamo-related technologies and, in 1880, a magneto signaling apparatus. Currently, magnetos have potential for use in crankpowered light beacons or radio devices for backwoods communications and emergency rescues. If someone were lost in the woods with a magnetobased locator or handheld two-way magneto radio, the lost individual wouldn’t be dependent upon batteries that wore out as long as he could turn a crank to generate additional current to power the device or to refresh rechargeable batteries. See electromagnet; Faraday effect; Gramme, Zénobe; induction; magneto phone; telephone history. magneto-optical MO. Technologies in which light is used to detect or influence the magnetic characteristics of a medium. In the context of communications technologies, magneto-optical refers to magnetic phenomena that can be controlled or read with optical technologies. Thus, a compact disc (CD) can be written by influencing the magnetic field associated with the materials within the disc and can subsequently be read by an optical laser pickup mechanism that senses the magnetic polarization of the encoded information. Many important data technologies are based on magneto-optical phenomena, including removable highcapacity data storage drives such as the popular CD and DVD formats. Magneto-optical discs do not suffer from “bit rot” to the same degree as certain floppy diskette and recordable tape technologies which can experience data corruption over time, or from proximity to magnetic sources (e.g., monitors). Because a magneto-optical disc-reading head is optical, there is no direct physical contact with the recorded/recording medium and thus some of the problems of hard drive wear and tear are eliminated. In general, vendors have sought to increase the numerical aperture (NA) of an optical lens to decrease the diameter of light incident or spot on the optic

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media in order to increase the track density and bit density of data on a disc. In other words, developers have worked hard to pack more information in less space in MO storage technologies. The ISO standard NA is 0.55 but companies like Maxoptix have achieved higher NAs (e.g., 0.8) with lower cost components that are readily available. See compact disc, Faraday effect, Kerr effect. Magneto-Optical Filter Development Group MOF. A collaboration of astrophysical organizations dedicated to achieving high-time cadence synoptic magnetograms of the Sun. The group provides a public data archive of the synoptic data from the Magneto-Optical Filter installed in the Kanzelhöhe Solar Observatory. magneto phone A historic phone mechanism based on magnetic-electric effects for the generation of low power current. While some magneto phones were handheld with a button to disengage the instrument from the phone circuit, the more common ones were wall or desk mounted and employed a crank handle to generate electricity through a magneto to produce an alternating or “ringing” current. This was used to send a signal from the subscriber to a switchboard to ring a bell that summoned the operator. The operator would then crank the switchboard to ring the callee and patch together the connection. The power for the conversation itself was usually supplied by a “talk battery” connected to each of the phones. Many of the old crank-handle magneto single-wire phone lines gave way to two-wire “common battery” systems in which the battery was located at the central switchboard. Yet, surprisingly, there were regions in the U.S. where magneto phones were in use right up until the 1980s! Magneto or battery power is no longer used in public phone systems except in some remote areas, because signal current to ring a bell or to notify the switching office that the phone is “offhook” is now supplied through the phone line itself, and the connection is established automatically by dialing the desired number. See magneto.

Left: An auroral display illustrating a magnetic substorm resulting from the interaction of the solar wind with the Earth’s magnetosphere. Atmospheric gases may cause different colors to be emitted. This image was captured from the Atlantis Orbiter Vehicle 104 in 1992. Right: Astronaut Alan Bean installs a small Lunar Surface Magnetometer on the Moon’s surface during the Apollo 12 mission in 1969. [NASA.]

magnetometer MAG. An instrument for detecting or measuring a magnetic field. A compass is a basic magnetometer. Magnetometers are used as navigation, measuring, and diagnostic instruments. They measure magnetic fields associated with the Earth, with various magnetic substances, and with electrical currents. A Barlington fluxgate magnetometer was installed in the early 1990s in Antarctica to measure magnetic field strength and direction. A magnetometer is one of the many sensors carried aboard the Galileo deepspace mission to the planet Jupiter, launched in 1989. It measures Jupiter’s magnetic field, its strong magnetosphere, and the characteristics and distortion in the fields caused by the interaction between Jupiter’s magnetosphere and nearby bodies (satellites, asteroids, etc.).

Top: The Lunar Portable Magnetometer mounted on the back of the Lunar Roving Vehicle during the Apollo 16 lunar exploration mission. Bottom: The Galileo spacecraft incorporated a large number of sensors, including magnetometers mounted on the long boom shown on the lower left in this artist’s concept. [NASA/JSC images.]

Magnetic effects are fascinating to most people and a number of types of magnetometers can be built with simple materials (e.g., a plastic bottle and bar magnet), making this a good instrument to use as an educational tool. More sophisticated laser magneto-

meters can detect subtle fluctuations in Earth’s magnetic field and can be built by more ambitious hobbyists. Thus, a torsion balance, rare-earth magnets, a pair of coils, a laser source, and reflecting mirror, can be combined to create a sensitive Baker-Diverdi magnetometer. magnetometer, induction IMAG. An instrument for detecting temporal variations in a geomagnetic field. An induction magnetometer may have several sensors with different characteristics incorporated into one housing. IMs can be used for a variety of purposes, including the study of electromagnetic characteristics of the ionosphere which, in turn, is useful in understanding transmission of radio waves. See magnetometer. magnetomotive force Descriptive of the relationship of magnetic flux and reluctance through a magnetic circuit, somewhat analogous to electromotive force in an electrical circuit, although the magnetic circuit has a region of influence that differs from an electrical circuit in air. See magnet, reluctance. magnetosphere A region within the solar wind flow in which there is an interaction between the solar wind and Earth’s magnetic field. Fluctuations and interactions within the magnetosphere, especially as it relates to the ionosphere, are important to understand in terms of their influence on radio waves. The term is attributed to Thomas Gold, in 1959. The first image of the magnetosphere, taken by an ultraviolet camera, was captured during the Apollo 16 mission. Solar flares contribute significant energy to the magnetosphere and can substantially influence and disrupt radio communications. Strong flares may even disrupt power systems! The magnetosphere also has its aesthetic aspects. When energy particles react such that electrons are directed into Earth’s atmosphere, the result is the Northern Lights (Aurora Borealis) and Southern Lights (Aurora Australis) – eerie, waving emanations in the sky best seen at dusk. NASA’s Education Web site offers information on the history and characteristics of the magnetosphere. http://www-istp.gsfc.nasa.gov/Education/ magnetron In its simplest sense, a magnetron is a surface with magnets in or behind it designed to attract and trap charged particles. This basic implementation of a magnetron is useful in industrial environments where it may be used in conjunction with a vacuum chamber to coat surfaces such as metals and alloys in a process called magnetron sputtering. In electron tube applications, a magnetron is a device that uses a magnetic field acting upon a diode vacuum tube to generate microwave frequency power. Magnetron tubes were especially important in the development of practical, long-range radar devices in the 1940s and later improvements on magnetron technology were incorporated into microwave ovens by Percy Spencer (Raytheon) in the mid1940s. Traveling-wave tubes (TWTs) evolved from magnetron tubes in the mid-1940s. Today, descendants of magnetron technology are important in satellite communications.

Germany, Japan, and America all contributed to the development of the magnetron in the 1920s and 1930s. Its origins date back to the work of H. Barkhausen and K. Kurz in Germany, who described the shortest waves that could be produced by vacuum tubes, in 1920. The invention of the magnetron itself is attributed to Albert W. Hull, who described it publicly in the AIEE Journal, in 1921. August Zacek may have made similar discoveries in the early 1920s, as he ordered several special diodes which could have been used to study electron oscillations. In Japan, Kinjiro Okabe proposed a divided anodetype magnetron in 1928 that helped further the practical applications of the magnetron. In 1935, A. Arsenjewa-Heil and O. Heil described the concepts of velocity modulation and spatial bunching. In 1937, William Hansen and the Varian brothers designed and built a prototype Klystron tube, capable of generating microwaves; they announced their invention in 1939. In Japan, Kiyoshi Morita ordered magnetron prototype tube from JRC and there was close coordination between the Naval Research Institute and JRC in the mid-1930s for building magnetron tubes, directed in part by Shigeru Nakajima, resulting in a water-cooled, single-phase, 500-W oscillator, in 1939. These were incorporated into radar systems in World War II. See Barkhausen-Kurz tube, cathode-ray tube, cavity magnetron, Klystron, traveling-wave tube. MAHO See mobile assisted handoff. mail bomb A vandalistic or retaliatory transmission sent through email protocols with the intention of disabling an email address, the system upon which the address resides or, at the very least, to greatly inconvenience or annoy the recipient. Mail bombs take many forms, but the most common is a repeated message that eventually floods the recipient’s email storage space or the storage space on the recipient’s service provider’s system, depending upon how it is partitioned. Mail bombs are often sent to people who post absurd messages on public forums, or to originators of junk email (unsolicited email, especially of a commercial nature) to express the extreme displeasure of the recipients receiving the junk email. A mail bomb may not solve the problem, since recipients sometimes retaliate. See flame wars, spam. mail distributor An agent, script, macro, or filter which takes incoming mail, evaluates the headers or other pertinent information, and distributes the mail accordingly. Thus, a single message might be forwarded to a number of users, different messages may be funneled to a single user, or groups may be set up to receive certain types of messages. The messages may include certain topics, which are keyed and processed, or may include priority or security information, which is handled accordingly. A mail reflector is the simplest type of mail distributor, which passes on mail with a minimum of evaluation and processing of contents (usually only the TO: header). A mail distributor can be a big time saver when it is used to forward email to a mailing list (a large group of recipients) or a discussion list. An address or

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database entry in the mail distributor can be used to expedite distribution to many recipients. This should not be used as a means to distribute junk email, more commonly known on the Internet as “spam,” as there are regulations against this type of use, and users do not appreciate receiving it (many will boycott companies distributing commercial mail in this way). See discussion list. mail filter A software utility or feature of an email client, which automatically evaluates the sender, recipient, subject line, or content of a letter to sort it into designated categories. Mail sent to a specific domain name is often filtered by companies to individual employees’ email accounts; junk email messages are often filtered out, and sometimes deleted unread. Some people filter personal and business mail into separate directories before reading the messages. Mail filters are a great convenience and worth the time it takes initially to set them up. mail gateway Although there are standardized protocols for the distribution of email over networks, not all systems use the same protocols, and not all protocols are implemented in the same way. Thus, when mail passes from one system to another, if there is a mismatch, there needs to be a way to resolve the differences, or to tunnel or encapsulate the messages so they can reach the recipients. A mail gateway is a system in a computer network that handles mail channeling or the resolution of protocols. mail list agent MLA. In SDNS Message Security Protocol (MSP), a mail list agent is one addressed by the message originator that represents a group of recipients. It provides message distribution services to the participants of that group on behalf of the message originator. mail list key MLK. In SDNS Message Security Protocol (MSP), a mail list key is a token held by all the members of a mail list, or by a mail addressable group within the list. mail reader A software program which permits email to be downloaded from a host system and read offline, so as not to incur connect charges or tie up a phone line. Most mail readers are actually mail readers and writers, and can be used to respond to the received messages or to compose new messages. They may also include filters to preorganize the mail before it is read, and a database interface which allows the messages to be organized and stored for later retrieval. Some mail readers have been enhanced for use as online news readers as well, for following discussion threads on USENET and for posting to the various online lists. Posting is the same as sending email, except that the message will be publicly available and may be read by thousands or millions of readers. Pine, developed by the University of Washington, is one of the most popular mail readers. It is freely distributable, allows flexible processing of mail messages and files, and includes news reading and posting capabilities. See email, USENET. mail reflector A mail node set up to pass messages on according to a predefined list. It does only the minimum processing needed to forward the mail to

its intended recipients. For information on more sophisticated processing, see mail distributor. mail server A software system which manages incoming and outgoing electronic mail on a network. Mail servers vary in complexity and features, but most will check the validity of an address; queue, deliver, and store messages (or return them if no valid address is found); forward mail, etc. Due to overwhelming increases in the quantity of junk email on the Internet, some of the newer mail servers will check the validity of the sending address, and reject the mail if the sender does not appear to be legitimate. This may result in the loss of some real email messages: for example, if someone is about to change email addresses and close out an old account, he or she may send email letting you know the new address, then subsequently close the account before the message reaches its destination. The server may reject the legitimate message. However, some consider the trade-off worthwhile, in order to deflect the thousands, or sometimes tens of thousands of junk mail messages that now flood the systems of most ISPs. See email, mail gateway, mail reader. mailbox The part of an email client/server software system that comprises addresses and files which store electronic mail. Web browsers and dedicated mail processing software programs typically enable the management of multiple user mailboxes. Many Internet Service Providers will offer multiple mailboxes to their subscribers (e.g., six mailboxes per personal account). Many business accounts offer unlimited mailboxes. MAILER-DAEMON, mail daemon A mail management program that works in conjunction with mail servers to process mail that cannot reach the destination address. Since the system may try several times to deliver the message before returning a message to the sender, there are two common messages received from MAILER-DAEMON: one is a warning that the message was not delivered and the system will try again later, and one says the message could not be delivered. The MAILER-DAEMON will usually provide information about the intended recipient and sometimes a reason for why the mail was not delivered. A common returned mail response from a MAILER-DAEMON looks like this: Date: Sun, 21 Dec 1997 13:56:41 -0800 (PST) From: Mail Delivery Subsystem <[email protected]> To: [email protected] Subject: Returned mail: User unknown The original message was received at Sun, 21 Dec 1997 13:56:40 -0800 (PST) from BigSender@localhost —— The following addresses had permanent fatal errors —— [email protected] —— Transcript of session follows ——

[returned message repeated here]

mailto A URL designation for the Internet mailing address of an individual or service. In a Web page, a mailto can be used to make it easy for a person with a Web browser to send a message to the person or organization mentioned. The format to set up the hypertext link is: Click to send email to Stan.

In the above example, the name Stan will be highlighted in the Web browser to indicate that it can be clicked. When it is clicked, the browser will launch the user’s email client, usually inserting the destination address automatically ([email protected]), and enables a message to be written and dispatched to Stan without closing down the browser. It’s very convenient but is falling into disuse because of junk email abuse – robot Web crawlers have been designed to quickly seek out mailto addresses on millions of sites, automatically adding them to junk emailing lists. See RFC 822, RFC 1738. main distribution frame MDF. A central wiring connection point in a larger more complex wiring system that includes more than one distribution frame. The main distribution frame is the one which connects the internal wiring with the external wiring. Within the premises, there may be secondary distribution frames in each department or each floor, depending upon the electrical needs and building configuration. See distribution frame. main memory In a computer, there are sometimes a variety of types of memory, and there may be more than one memory bank. On some systems, where all the available memory is addressable by the system without significant restrictions, the concept of main memory is not important, as all memory is main memory. However, some systems make a distinction between system memory and expansion memory, and it may not be possible to address all the memory as one contiguous area. These systems treat the first memory, that which is addressed by default or used as first priority, as main memory. Extra memory for video display and other specialized uses is not considered main memory as it is not used as generalpurpose storage by the system. main station This is a loosely defined phrase because it is highly context-specific. The people within a system often have a tacit understanding of main station facilities and the definition varies widely, depending upon the industry. 1. In telephony, a user telephone set or terminal with a unique call designation used for originating calls and accepting calls on an exchange. If there are extension phones with the same phone number, one is usually designated as the main station. 2. In computing, an “intelligent” workstation (as opposed to a “dumb” terminal, for example) installed with a full set of capabilities or which functions as a primary or secondary server. A main station may also be a terminal with access to resources that may be otherwise restricted within the local facility, such as scanners, printers, modems, etc. 3. In broadcasting, a primary sending or receiving station, as opposed to a specialized or lower-resource

relay station. A main station is more likely to be staffed or to have significant technological or broadcast power capabilities compared to other stations in the system. A main station is not always the largest or best-equipped station in a system; it may also be a clearinghouse or storage unit for a significant number of broadcasts or broadcast recordings, or it may be the highest-power station or one located on the highest prominence in the network. mainframe The terms mainframe, miniframe, and workstation are all relative. The most powerful computers in the world are called supercomputers, and the less powerful computers that are above the consumer or workstation price range are called minis or miniframes. Mainframes fall in between these two categories. In general, mainframes are typically the larger, more expensive, more powerful, faster systems with more storage capacity and the ability to handle many users on a network. Workstations and microcomputers are often used as smart terminals in conjunction with mainframes. Mainframes are used in larger educational institutions, large businesses, and scientific research facilities. Current consumerpriced desktop microcomputers are more powerful than the mainframes available 15 years ago. mains A primary commercial alternating current (AC) power supply. In North American domestic power grids, mains power is typically single-phase power routed through a breaker box to internal wiring. Triple-phase power is also available in some areas, usually carrying higher voltages. Mains electricity is used to power appliances, lights, heating units, industrial facilities, safety devices, etc. Mains AC voltage for North America, South Korea, and parts of South America is 100 to 120V at 60 Hz. In Japan, it is 100V at 50 and 60 Hz. Mains AC voltage in Europe is around 220 to 250V, depending upon the country, with a target goal of 230V at 50 Hz by 2003 for unified Europe. One of the reasons for the many different types of electrical plugs in different countries is to prevent electrical shocks, fires, or damage to components resulting from the varying electrical properties of the mains power. Increasingly, radio frequency (RF) signals are sent over mains wiring within buildings. This enables consumers to transmit audio, visual, and control (e.g., X10 components) signals through the wiring to other locations in the building without running dedicated wires or worrying about low-power wireless signal attenuation through walls and over distances. While this was not a problem in the past, the increasing prevalence of mains use for secondary signaling may become a concern as a source of interference. In some cases, such as industrial applications, the power coming from the mains may not be exactly what is needed. The power may be conditioned to meet specific industrial or electronic needs. For use with sensitive electronic equipment, mains energy is often channeled through surge suppressors and transformers to filter and convert the energy. Many electronic devices require only 4 to 12V, far less than is coming from the mains supply and would be burned out without appropriate conversion.

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Power does not always come out of the National Grid mains line; sometimes it is directed into the Grid. Alternate energy sources such as wind turbines sometimes generate more electricity than is needed and the surplus may be directed to the mains, depending upon power agreements and regulations in the area. maintenance termination unit MTU. An electronic diagnostic device installed at a line termination unit (LTU) of a premises installed with telecommunications equipment, usually by the line provider. The MTU typically performs circuit tests for short circuits or open circuits that may be remotely monitored. This aids network operators in locating the source of a fault and determining whether the problem exists on the customer or connection side of the LTU. Multiple MTUs may be installed along a subscriber line to further pinpoint fault locations. Major Trading Area MTA. A service area designation adopted in the early 1990s by the Federal Communications Commission (FCC) based upon an older Rand McNally classification of U.S. metropolitan regions. MTAs were identified by the FCC to administer and license wireless Personal Communications Services (PCS). There are over 50 MTAs in the U.S., built from contiguous Basic Trading Areas (BTAs) from almost 500 BTAs. Regional designations are somewhat important in administering wireless services, since the frequency ranges must be reused as efficiently as possible to provide service to as many areas and individuals as possible. The FCC provides a Market Area cross reference that enables a user to search by MTA, BTA, or state and county to find corresponding markets. Thus, an MTA can be used to find corresponding BTAs or counties. For example, a search of the New York MTA yields a list of 20 BTAs, from Albany to Watertown, which are further linked to a list of counties within the BTA. http://www.fcc.gov/ Majordomo A widely used software program that automates the management of Internet discussion lists, developed and licensed by Great Circle Associates (GCA). It enables the remote administration of email list subscriptions, electronic mail messages, digests, and archives. Thousands of Majordomo lists are online, many with tens of thousands of subscribers. Lists may be open, private, or moderated. List management is handled through electronic mail (email). Some people call them mailing lists, but it is best to make a distinction between discussion lists, which are for the exchange of information and debate, and mailing lists which are used by marketing agents to email advertising messages. The name is derived from head domestic or butler, the traditional manservant or master who handled visitors and the oversight of a house (domicile). Similarly, Majordomo does your bidding and handles your affairs, leaving you free to concentrate on communications with discussion list guests. Many people have become familiar with Majordomo and similarly designed discussion lists on the Internet. The software enables individuals to join or leave a mailing list by sending an email message that in-

cludes the word subscribe or unsubscribe. Messages sent to the list are then forwarded to each subscriber of the list either individually or, if desired, as a combined digest of recent messages. The list administrator can exercise some control over who joins or may post and selectively remove people from the list who violate the list charter or the bounds of decent behavior. Majordomo source code is written almost entirely in Perl, which makes it possible for Perl programmers to modify the source for their needs within the terms of the Majordomo License Agreement. Majordomo runs on a wide variety of Unix platforms and a Web interface is available as an add-on. Majordomo source code is available for free download within the terms of the licensing agreement. Version 1.94.5 was released in January 2000 and Jason Tibbits is developing Majordomo version 2. See LISTSERV. http://www.majordomo.com/ Make Busy A subscriber service or feature of a phone that causes the line to send a busy signal to an incoming call. This is like taking a line off the hook without remmoving the handset. While this might seem like an odd thing to do, it can actually save people money. If a business has more phone lines than agents ready to take calls (e.g., at lunch time), it may be better to send a busy signal than to let it ring indefinitely or to answer and put the caller on hold for a long time (which people don’t appreciate). If the callers are dialing long distance, it can save them the toll charge, since the call is not answered. Make Busy is also helpful to the receptionists on duty, since it can reduce the number of incoming calls to a manageable level. Depending upon the service, Make Busy can be assigned to one or more lines within a hunt group. See Ring Again. malicious call A telephone call with annoying, abusive, obscene, or threatening intent. In many areas, malicious calls are unlawful, but it may be difficult to prove the malicious content of the call, especially since wiretapping laws generally prevent the caller from being taped without his or her permission. In general, telemarketing calls are not considered malicious unless the caller is promoting illegal products or promoting them in a harassing or intentionally deceptive manner. Upon seeking help with malicious calls, you will generally be advised not to take the phone off the hook, but to answer it repeatedly and to immediately and quietly hang up, no matter how many times it takes. If the malicious caller utters what appear to be genuine threats, it is advisable to inform the phone company, the police, and other members of the household or office. If the malicious call appears to involve fraud, inform the phone company, the police, relevant consumer associations, and other members of the household. Some phone companies have call investigation centers that can assist the police with trapping and tracing persistently malicious calls, especially those of a threatening nature. Malus’s law When a beam of light that has already been once polarized by reflection hits a second surface at the polarizing angle, the intensity of the beam

varies as the square of the cosine of the angle between the two surfaces. MAN See Metropolitan Area Network. Management Information Base MIB. A set of data modules which contain the definition of a related set of managed object types. In SNMP management systems, it contains the logical names of informational resources on the network. In SONET network implementations, objects in the MIB are defined with a restricted subset of Abstract Syntax Notation One (ASN.1) as to their name, syntax, and encoding. Management Information Services MIS. Corporate communications professionals whose job is to facilitate the acquisition, flow, use, storage, and retrieval of information within an establishment. Mance, Henry Christopher (1840-1926) A British engineer who adapted the Indian heliotrope to a heliograph daytime signaling system using mirrors mounted on tripods. The angle of the mirror could convey line-of-sight dot and dash signals up to 100 miles. This system was used for military communications for several decades. Manchester encoding An encoding scheme commonly used for baseband signaling in coaxial cable transmissions, especially 10Base-T network systems. There are variations to the encoding, but a typical differential Manchester employs a voltage transition in the middle of a bit period. A zero is represented with an additional transition at the beginning of a bit period. A one is represented with no transition at the beginning of a bit period. There is a tradeoff between bandwidth and binary coding, as the coding consumes part of the bandwidth. In Manchester encoded transmissions, the amount of useful bandwidth is about twice the encoding signal. The Manchester encoding scheme is simple but useful, and can be used as one type of passband signal. Manchester Mark I An early large-scale computing machine designed and built by Fred Williams, Tom Kilburn, and Max Newman in the late 1940s. It was significant in its ability to store programming information. The earlier prototype for this machine was colloquially known as “Baby.” The Manchester Mark I was composed of more than 1000 vacuum tubes. Input and output were communicated through switches, paper tape, and a teleprinter. mandatory access control MAC. In network security, an access control service that enforces a security policy based upon a comparison of security labels and security clearances. Thus, access to resources can be controlled based upon the sensitivity of the desired information and the formal authorization of entities to access information of that level of sensitivity. An entity with access may not on its own enable other entities to access a resource made available to it. Mandelbrot, Benoit (1924- ) A Polish mathematician who emigrated first to France in 1936, and later to the United States. Mandelbrot extensively researched areas of complex geometry which have come to be known as fractal geometry. At least part

of his thinking coincided with, or developed from, the work of G. Julia, who published important mathematical observations on the iteration of rational functions in the early 1900s. One family of fractal images called the Julia set is named after this predecessor. Mandelbrot’s early publications on fractals include “Les objets fractals, forn, hasard et dimension” (1975) and “The Fractal Geometry of Nature” (1982) which created an enormous stir, especially in North America, and fueled much of the fractal imagery since generated on computers. MANIAC A historic large-scale computer developed in the mid-1950s by the Los Alamos National Laboratory. The construction of its successor, the MANIAC II, inspired professors at Rice to initiate the Rice Computer Project. See Atanasoff-Berry Computer, ENIAC, Rice computer. manipulation detection code MDC. Software algorithms for detecting whether data or processes have been changed or otherwise manipulated in the interim, over a set period of time, or during a dynamic session. Manipulation detection code is intrinsic to many types of workgroup applications in which two or more people may be using, changing, or interacting with the same application or database; the administration of the interactions must be carefully organized so they don’t clobber each other’s processes or data. Manipulation detection code is also an important aspect of monitoring networks for intrusion or malicious tampering. The code may be something as simple as a log that keeps track of logins or file changes or failed password attempts or as sophisticated as specific sequences of data interposed into a system, program, or file that are assessed and possibly manipulated to detect tampering of various kinds or to send messages to the system administrator as needed. MAP See Media Access Project, an important organization representing the public good. Marconi antenna An antenna that requires the ground, or a large object to which it is mounted (such as a vehicle), to aid in resonance conduction. In other words, it is not a stand-alone antenna like a Hertz antenna. Marconi antennas are commonly used in amplitude modulation (AM) broadcasts. See antenna, Hertz antenna. Marconi detector An adaptation of the Branly detector to which G. Marconi added a vibrating source to quickly set the coherer back to zero or nonconducting status. See detector. Marconi, Guglielmo (1874-1937) An Italian who as a youth demonstrated wireless telegraphy to his mother in an attic laboratory in 1894, and experimented with radio waves in 1895. With further support and assistance from his mother, Annie Marconi, the 22-year old Marconi filed for a patent and demonstrated radio communications in London the following year, and received a British patent in 1897. Marconi traveled and lectured extensively, and kept in touch with other inventors in the field of radio communications.

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Guglielmo Marconi was a significant pioneer of radio technologies. [National Archives of Canada Marconi Company collection.]

A copy of a Western Union telegram from Marconi to Alexander Graham Bell, thanking him for his invitation to visit his summer home in Nova Scotia, December 19, 1899. In the end, Marconi declined this particular visit because Bell’s location was not on the ocean, so it sounds as though Marconi was considering transatlantic communications at the time, a feat which he successfully achieved in 1901. [Library of Congress Alexander Graham Bell Family Papers Collection.]

Donald Manson at work at the Marconi Company in England in 1906. [National Archives of Canada Donald Manson collection.]

Marconi’s first communications were over very short distances, but in 1901 he showed that radio signals could be sent across the ocean between Canada and England, a distance of over 3000 km. He continued

for many years to devise improvements in the technology, and to put them to practical application. In 1909 he was awarded a Nobel prize in physics along with K. Braun. Marconi began broadcasting from Marconi house in 1921 under the famous 2L0 callsign. See Braun, Karl Ferdinand; Murgas, Josef; Tesla, Nikola. MARECS A European maritime satellite communications service established in the early 1980s; it is similar to the American MARISAT system. Marine Radio Operator Permit MROP. A radiotelephone permit issued by the Federal Communications Commission (FCC) which is required for the operation of radiotelephone stations aboard certain Great Lakes vessels and for certain aviation and coastal radiotelephone stations. The MROP does not authorize the operation of AM, FM, or television broadcast stations. Issuance of the 5-year, renewable permit requires passing the Written Element 1 exam, which covers basic radio law and operating procedures. See General Radiotelephone operator license, Restricted Radiotelephone Operator Permit. Marine Safety Office MSO. An office of the U.S. Coast Guard, located in Mobile, Alabama. The Coast Guard Inspection Department operates from a location near the main office. The MSO is responsible for protecting life, property, and the environment along the coastlines and navigable waterways of Mississippi, Alabama, and northwest Florida. MARISAT Maritime Satellite. First launched in 1976, MARISAT was designed to provide mobile communications services to the U.S. Navy and other maritime clients. The European MARECS system is similar. Maritime Identification Digits (MID). See Maritime Mobile Service Identity. Maritime Mobile Service Identity MMSI. An administrative identifier allocated and issued by various national maritime safety authorities to marine vessels. The MMSI is a unique, internationally standardized, nine-digit identification number, similar to a radio call sign or telephone number. It may be programmed by the vendor of the equipment or, in some cases, the operator. It is associated with a Digital Selective Calling (DSC) number (a system that enables group or broadcast calling). DSC radios may be linked with Global Positioning System (GPS) receivers. MMSI numbers were developed for compatibility with the public telephone system and the number facilitates the routing of data and voice transmissions. If more than one radio is installed in a vessel, it is to be programmed with the same MMSI. If a vessel carries an Emergency Position-Indicating Radio Beacon (EPIRB), it may also be assigned the same MMSI as other radios on the vessel. MMSI may be used for ship-to-ship and ship-to-shore communications. MMSIs are not exclusive to boats; INMARSAT satellite terminals also use MMSI numbers. Three of the digits of the MMSI, called the Maritime Identification Digits (MIDs), indicate the country of location or registration, while six digits are used to uniquely identify the station. The number may be

used for emergency identification or for more mundane matters such as call tracking and billing. On the international level, the International Telecommunication Union (ITU) maintains a database of the MMSI of every vessel, called the Maritime Mobile Access and Retrieval System (MARS), which is accessible online. Individual nations also maintain databases. In the U.S., MMSIs are recorded by the Federal Communications Commission (FCC) and the Coast Guard. Some nations assign MMSI numbers free of charge (e.g., Industry Canada) and some charge an application fee. In spring 2001, in the U.K., the Radiocommunications Agency introduced new procedures for the issuance of MMSI numbers to facilitate the use of portable VHF Digital Selective Calling (DSC) radio equipment. Thus, vessels that cannot be installed with fixed radios can realize some of the benefits of MMSI and the Global Maritime Distress and Safety System (GMDSS) through portable equipment. Portable equipment is allocated unique MMSI numbers, regardless of the numbers assigned to existing fixed equipment associated with a vessel. Portable MMSI numbers in the U.K. are issued a 2359 prefix exclusive to mobile equipment. Due to the unique nature of portable equipment, national radio licensing authorities will need to be notified if an MMSI-assigned device changes hands. It is likely that other nations will institute similar policies and procedures to accommodate the rising number of portable communications devices. Mark accelerators A series of pioneering accelerators leading to the development of the world-renowned Stanford Linear Accelerator Center (SLAC), developed by William W. Hansen, who had earlier contributed to the invention of the Klystron tube (used in a variety of microwave communications and imaging technologies). The Mark I accelerator produced a 6 MeV electron beam. The Mark II was used for research in nuclear physics and the Mark III for a high-energy physics program. See Hansen, William. Mark I See Harvard Mark I. Mark-8 A pioneer Intel 8008-based personal computer kit. The Mark-8, a scaled-down hobbyist cousin of the PDP-8, was described in a June 1974 issue of Radio Electronics magazine by Jonathan Titus. However, it didn’t achieve widespread commercial success. See Altair, Intel, Kenbak-1, Micral, Scelbi, SIM4, Sphere System. mark-to-space transition, M-S transition In telegraphy, the momentary change when the system reverses polarity, or changes from a closed to an open circuit. At this point, a small amount of delay must be taken into consideration, which can be plotted on a timing wave. The reciprocal is the space-to-mark transition. MARS Multicast Address Resolution Service. In ATM networking, a protocol used in IP multicasting. MAS 1. See Multi-Agent Systems Laboratory. 2. See Multiple Address System.

maser microwave amplification by stimulated emission of radiation. A type of laser technology developed in the late 1950s. See laser. mask A screen, stencil, or other object superimposed between a surface and light, pigments, or other media put on that surface so only the unmasked portions are seen or affected. When used with light, a mask is known as a beam block. mask, data In computer programming, a mask is a set of data, flags, or bits used as a filter or operator to affect only those bits of data that correspond to the mask template, or which are not included in the mask template. masquerade attack An attack on a system by an entity posing as another entity that has authorization to access that system or resource. See spoofing, Trojan Horse, virus. Massachusetts Microprocessor Design Center MMDC. An Intel microprocessor research and design center located in Shrewsbury, Massachusetts. In August 2001, over 200 Compaq microprocessor engineering and design employees joined Intel as part of an agreement for Compaq Computer Corporation to transfer key enterprise processor technology to Intel. Massie Oscillaphone A simple type of loose contact electromagnetic wave detector long favored by amateur experimenters and educators. Two carbon blocks (battery carbon can be used) are set up adjacent to one another, about an inch apart, on a nonconducting base such as wood. The top surfaces of the carbon blocks are chiseled or filed so that they have a fine, thin edge. Holes are drilled through their surfaces, near the base, to provide room to insert a screw through each block, with the screwheads on the outside, to secure wires that connect with two binding posts. The top thin surfaces of the carbon blocks are wiped with a woolen cloth, and a light sewing needle or other similar conductor is laid across the top of the two blocks to create a contact between them. When connected to a circuit including a battery power source, aerial, ground, and telephone receiver, an incoming radio wave will interact with the needlecarbon contact, causing the needle to adhere more closely to the blocks, lowering the resistance. This results in an increased flow of current which is translated into sound in the receiver. Further adjustments to the sensitivity of the needle can be made by placing a small magnet under the needle and adjusting its height. See detector. master group In analog voice phone systems, a hierarchy for multiplexing, organized as a series of standardized increments. See voice group for a chart. Matrix.Net A commercial service disseminating information on Internet hosts and providing Internet Performance Measurement products. Event Advisories on incidents and trends of particular importance to the Internet are provided on the Web site for free. Estimates and data on Internet hosts are based on raw data from the Network Wizards’ global domain surveys.

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MAU 1. See Media Access Unit. 2. See Multistation Access Unit. Mauchly, John W. (1907-1980) An American physicist and engineer who collaborated with J. Eckert to build the historic ENIAC computer. See ENIAC. MAX See Media Access Exchange. Maxim, Hiram Percy Founder of the historic Amateur Radio Relay League (ARRL), along with Clarence Tuska, a young fellow radio amateur, who became friends with Maxim after the older radio enthusiast had decided not to purchase radio equipment constructed by the precocious Tuska.

used to aid radio operators and listeners. Since conditions constantly change, many software-generated maps are updated frequently, sometimes every few seconds or minutes, depending upon the system. Times associated with the maps are usually expressed in Zulu time. maxwell An electromagnetic unit of magnetic flux to the flux-per-square centimeter equal to magnetic induction of one gauss, or one magnetic line of force. It is named after J. Clerk-Maxwell. Maxwell, James Clerk- (1831-1879) A precocious Scottish physicist who, building on the work of Faraday and Bernoulli and adding ideas of his own, contributed many important fundamental theories and equations related to electromagnetism and the nature of particles. He also made mathematical predictions about the composition of Saturn’s rings that held up well over time.

Hiram Maxim, W1AW, listening in on a set of earphones in the days when crystal detectors were common radio devices. Maxim encouraged amateur radio participation. [The Hartford Times, 1914.]

Maximum Transfer Unit MTU. In Internet Protocol (IP) networking, the largest size of IP datagram that may be transmitted through a specific data link connection. The MTU is not a fixed amount, but is a mutually-agreed value that can vary widely up to about 10 kilobytes. In a distributed network with a number of hops, a datagram may pass through nodes with different MTU sizes, necessitating queries and processes for handling the incoming data and its subsequent routing. If the relay or receiving MTU is smaller than the size of a transmitted packet, the packet must be subsected to segments smaller than the MTU and information about the process conveyed to the next link or recipient. maximum usable frequency MUF. In a radio transmission signal path based upon propagating radio waves through Earth’s ionosphere (e.g., through the Great Circle signal path from the eastern U.S. to Japan), the upper frequency level that may be usable. In general, higher frequencies are associated with lower refraction rates in the ionosphere. The MUF varies with terrain, region, and the influence of rays from the Sun. Software programs can monitor and calculate the various factors that influence usable radio frequencies and will generate and display charts that can be

James Clerk-Maxwell is remembered for many of his mathematics and physics contributions related to fundamental laws and electromagnetism.

Maxwell’s equations A set of fundamental mathematical equations, originated by J. Clerk-Maxwell and further developed by Oliver Heaviside and Heinrich Hertz, for expressing radiation and describing conditions at any point under the influence of varying electromagnetic fields. These concepts and equations are integral to many areas of science, and are of particular interest in understanding and developing transmissions media, antennas, and other basic building blocks in telecommunications. See Heaviside, Oliver; Hertz, Heinrich Rudolph; Maxwell, James Clerk-. Maxwell’s rule Every part of an electric circuit is acted upon by a force which tends to move it in a direction such as to enclose the maximum amount of magnetic flux. Maxwell’s theory of light In 1860, J. Clerk-Maxwell demonstrated that the propagation of light could be regarded as an electromagnetic phenomenon, the

wave consisting of an advance of coupled electric and magnetic forces. If an electric field is varied periodically, a periodically varying magnetic field is obtained which, in turn, generates a varying electrical field and thus the disturbance is passed on in the form of a wave. Maxwell’s theory predicted that the speed of light unimpeded was constant. Maxwell’s triangle An ordered representation of color relationships, in the shape of a triangle, developed in the late 1800s by physicist J. Clerk-Maxwell. His premise was that this model would contain all known colors. Red, green, and blue are identified as the three primary colors of light and are located in the three corners of the triangle. The colors progressively blend until, in the center, the combination of all the colors becomes white. A system of color notation was developed by laying a grid over the triangle. See color space, Munsell color model. Mayer, Maria Goeppert (1906-1972) A Polishborn, American physicist who carried out fundamental research in models of the nucleus of atoms. For her independent work, she was awarded a Nobel Prize in physics, along with J. Jensen and E. Wigner. Mbone multicast backbone. See 6bone, backbone, multicast backbone, X-Bone. MBS See Mobile Broadband System. Mbus Message Bus. An open peer-to-peer coordinating infrastructure that provides integration for modular computerized systems design. The Mbus is especially applicable to “lightweight” distributed applications (e.g., limited-resource portable communications devices). It enables cooperation among modules serving a particular purpose while still supporting a variety of interoperable languages and communications standards. The Mbus framework is extensible and securable and can be implemented in a variety of multimedia and communications environments. It is intended to facilitate the design and assembly of complex systems out of simple components by providing a data channel through which application modules can find one another. The Mbus is a local infrastructure providing transport layer functionality and addressing schemes including failure detection, session establishment and teardown, and component configuration. Mbus processes are message-based rather than object-based and are not programming language paradigm-specific. Components can be dynamically added, removed, or exchanged at runtime. Mbus messaging may be unicast (to a specific address), broadcast (to all entities), or multicast (to qualified entities). The Mbus message itself includes a payload consisting of commands and their associated arguments/parameters that are processed by the messaged entities. The entities in the system periodically signal their presence to the Mbus group. Message Bus profiles for local coordination and call control were submitted as Drafts to the IETF in February 2001 by Ott et al. See MBus, Multiparty Multimedia Session Control. http://www.mbus.org/ MBus memory bus. MBus is used somewhat broadly to describe both memory bus systems and messaging

systems specifically related to memory-related processes. As an example, in CoreFrame architecture, MBus denotes the data bus for high-speed access to external memory from the central processing unit (CPU) core or peripheral blocks (as opposed to a communications bus that does not access memory). In this scenario, the Mbus facilitates communication between the Memory Access Controller (MAC) and memory channels and is synchronous to the MAC. Following Mac arbitration and “permission,” the MAC becomes the controlling data bus. Since memory devices vary considerably, the Mbus must adapt and allow the MAC to control the bus as appropriate. In multiple bus architectures, the MBus may be associated with a result bus (RBus) and an address bus (ABus), as suggested by R. Katz for more parallel designs. See bus, data; Mbus. MBUS multiprocessor bus. A multiprocessor interface specification from Sun Microsystems, Inc., introduced in 1991 and discontinued in 1996. Spelling in all caps is recommended to distinguish it from a message bus (Mbus) or memory bus (MBus). In Sun Microsystems SPARC implementations, the MBUS is a synchronous master-slave processormemory bus supporting shared-memory multiprocessing driven at TTL levels. It is a single-transaction, big-endian bus with a bandwidth of 320 MBps. MCC Miscellaneous Common Carrier. See Radio Common Carrier. McCahill, Mark P. Project leader in the development of the Gopher distributed networks query/ search mechanism; Gopher was released by McCahill and Paul Lindner in 1991. It was one of the first accessible, nontechnical software applications that allowed teachers, researchers, and other professionals untrained in computer programming to access the storehouse of information that was accumulating on computer networks. Web browsers are, in a sense, the next generation version of Gopher for the Internet (text-based Gopher servers are still in use), providing point-and-click and graphical capabilities in addition to the basic query/search functions that aid in locating information online. See Gopher, Web browser. McCarthy, John (1927- ) A recognized pioneer in the field of artificial intelligence since 1955, McCarthy was one of the first to promote the basic concepts of computer timesharing in the late 1950s. McCarthy is also known as the originator of the LISP interpreted programming language that is popular in artificial intelligence research. See LISP. McCaw Cellular Communications, Inc. A commercial communications services provider chaired by Craig McCaw, which was sold to AT&T in 1994 and renamed AT&T Wireless Services. McCaw is now collaborating with W. Gates, Motorola, Boeing, and others to develop the Teledesic satellite-based Internet system. See Teledesic. MCF See Multimedia Communications Forum. MCID malicious call identification (e.g., as in ISDN

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Q.81 and Q.731 number identification services). McLennan, John Cunningam A Canadian physicist and educator who explored cosmic rays, gases, and transportation innovations, and was one of the first to propose helium as a substitute for hydrogen in zeppelins and other lighter-than-air ships. McLennan invented a new way to extract helium that dramatically reduced the cost of production and made balloon transport safer and more economical. MCNS See Multimedia Cable Network System. MCNS/DOCSIS See Data Over Cable Service Interface Specification, Multimedia Cable Network System. MCS-4 A significant early (1970s) chipset that inspired pioneer computer designers. See Intel. MD series A series of message-digest (MD) hash algorithms developed by Ronald L. Rivest that can be used, for example, to secure electronic mail communications. The MD algorithms have been incorporated into a number of significant data encryption systems including RSA Security Inc. cryptographic products. Series

Description

MD2 128-bit one-way hash developed in the mid-1990s. MD4 128-bit one-way hash that is faster than the previous MD4. MD4 was incorporated into P. Zimmermann’s Pretty Good Privacy (PGP) 1.0. MD5 128-bit one-way hash, an improved version of MD4. While reasonably secure, it has been suggested by Dobberlin that, if two files with the same MD5 hash were to be created (not an easy task), it might be easier to threaten the software. Leeming has suggested that a greater threat might be in finding two cryptographic keys with the same MD5 checksum, in which case the digital certificate for one could be used to access the other. PGP 2.0 and subsequent versions use this algorithm. See Pretty Good Privacy, RSA Security Inc., RC6, RFC 1319, RFC 1320, RFC 1321. MD-IS See Mobile Data Intermediate System. MDF See main distribution frame. MDS-xxx A line of commercial digital switching products from Raytheon E-Systems. MDT mobile data terminal. MDX multidimensional extensions. In the context of the Microsoft Data Warehousing Framework, a syntax for querying multidimensional objects and data. MDX has a grammar similar to SQL. mean opinion score MOS. A statistical quantification of reported subjective impressions. In other words, it is a value based upon people’s perceived and stated impressions or preferences. MOSs are useful for assessing sensory impressions that are

difficult to measure empirically, such as the quality or effectiveness of a perfume, massage, sound, or image. In audio communications, MOSs are used to determine whether a sound, such as speech, is pleasing, clear, or intelligible. In fact, the ITU-T has defined MOS more narrowly to focus on speech digitization and recreation and provides a rating scale from 1 to 5 for reporting the results. This helps programmers to tweak their Voice over IP (VoIP) software, for example, to balance file sizes and transmission speeds against sound quality. See P Series Recommendations. mean time between failures MTBF. A performance indicator, the limit of the ratio of the operating time in a device to the number of failures as the number of failures approaches infinity. At the factory, test versions of a product are often subjected to extreme use to estimate in advance what its MTBF rating might be under conditions of actual use. MECAB See Multiple Exchange Carrier Access Billing. Media Access Control, Medium Access Control MAC. Functions associated with the lower half of the data-link layer that governs access to the available IEEE and ANSI local area network (LAN) media (or medium, if there is only one). This layer supports multiple downstream and upstream channels. Devices such as network bridges are associated with the MAC layer (or sublayer in OSI). Media Access Control address, MAC address A MAC address is an important routing statistic widely used for managing data network transmissions. Route-related devices typically keep a list or table of MAC addresses which may be static or dynamic. Dynamic MAC address lists may be updated in a variety of ways depending on the stability of the configuration of a network and the size of a network. The MAC address is used by a network bridge to determine whether a packet is to be forwarded. By copying an incoming source address to a MAC address table, the bridge builds up a port-related “picture” of device locations on the network. Since there are usually efficiency trade-offs on large networks, with machines being added and removed and MAC address tables becoming large and unwieldy, certain balancing mechanisms are built into bridge management. By limiting the lifespan of a MAC address, the system can be tuned to best serve the needs of the network. Thus, a dynamic MAC address that has not been used for a long time will be removed until a transmission is again received from that source. Lowuse special purpose addresses (e.g., emergency systems) that must stay active can be assigned a static MAC address that isn’t automatically deleted. Media Access Exchange MAX. A system-level network access unit from Ascend Communications, into which peripheral cards can be inserted. A MAX can support multiple host ports or direct network connections, videoconferencing units, and remote LAN connections. Media Access Project MAP. An important nonprofit, public interest telecommunications law firm that looks out for the First Amendment rights of

individuals before the legal system and the Federal Communications Commission (FCC). Over the years, broadcast agencies have been provided free use of the airwaves and, in return, have a legal responsibility to provide a portion of programming and resources for the public good. They are bound to uphold these obligations but may neglect them without citizen support groups like MAP, who take the time to lobby for the interests of the little guy. In recent years more free bandwidth has been broadly allocated to commercial broadcasters, particularly satellite broadcast frequencies. It is important that citizens safeguard their rights, and that it be impressed upon the government, the FCC, and the broadcasters that these broader free permissions have inherent corresponding responsibilities. http://www.mediaaccess.org/ Media Access Unit MAU. In Token-Ring local area networks (LANs), a wiring concentrator that connects the end stations. The AU provides an interface between the Token-Ring router interface and the end stations. Also known as Access Unit (AU). See Multistation Access Unit. Media Interface Connector MIC. An eight-pin modular RJ-45-8 plug. This resembles a common RJ11 phone jack except that it is wider to accommodate connections for eight wires. This is the connector recommended for audio-visual applications by DAVIC specifications. medium Earth orbit MEO. An orbiting region around the Earth into which certain types of communications satellites are launched, mid-way between low Earth orbits and the high Earth orbits into which geostationary satellites are typically launched. The lifespans of medium-orbit satellites tend to be around 10 to 12 years. Most medium-orbit satellites travel about 10,000 to 15,000 km outside Earth. A region called the Van Allen radiation belt between MEO and low Earth orbits (LEOs) is generally avoided. MEO satellites are primarily used for a variety of broadcast applications. See high Earth orbit, ICO, low Earth orbit, Teledesic. Meet Me A commercial FTS2000 capability initiated by dialing an access number at a prearranged time, or as directed by an attendant, to establish a group conference call. Additional conferees can join a conference in progress with an Add On conference. It may be necessary to make arrangements for a Meet Me call several hours in advance, depending on how the system is administered. See FTS2000. Meet-Point Trunk Telecommunication trunks configured for two-way traffic in jointly provided Switched Access Services (SAS), to interconnect End Offices and Tandems. mega- (abbrev. – M) An SI unit prefix for 1 million, expressed as 106 or 1,000,000. To confuse matters, when used in conjunction with computer-related quantities, it often means 220, expressed as 1,048,576. The most common of these uses is in descriptions of computer storage capacity as megabytes (MBytes), in which 1 MByte is 1,048,576 bits. See kilo-. Megaco Protocol A network media gateway control protocol used between elements of a physically

decomposed multimedia gateway, that is, between a Media Gateway and a Media Gateway Controller. The Protocol was submitted as a Standards Track RFC by Cuervo et al. in November 2000. It provides a general framework suitable for gateways, multipoint control units, or interactive voice response units to interact. The protocol definition has common text with ITU-T Recommendation H.248. A Media Gateway converts media from one type of network to a format compatible with another type of network. The gateway may be able to process and translate audio, video, or T.120 and can handle full duplex media translations, in addition to playing and executing media performances or conferences. Megaco Protocol connection model describes the logical entities/objects within the Media Gateway and can be controlled by the Media Gateway Controller. See RFC 3015. megger An instrument for measuring values of very high resistance used, for example, for insulation resistance testing. See Wheatstone bridge. Melissa See virus. Melpar model An artificial neuron used at the Wright-Patterson Air Force Base in Ohio in the early 1960s to mimic human reasoning (or at least rodent reasoning). The Melpar model, familiarly called Artron by its inventors, was used as the “brains” of a maze-running bionic mouse, physically resembling the input mice used on today’s computers. The bionic mouse brain comprised 10 Artrons, which was sufficient for a trial-and-error method of learning to run the maze. With a clean slate, the mouse took 45 minutes to complete the maze; eight tries later, it took only 35 seconds. See neural network. memory In a computing system, a storage area that is dynamically allocated and used by the operating system and various application programs. Most memory in desktop computers is random access memory (RAM), although some programs will also allocate hard drive storage as “virtual memory.” Memory is one of the most basic elements of a computing system, along with the central processing unit (the CPU often also incorporates memory internally) and the input/output (I/O) bus. Read only memory (ROM) is included in many computers to provide basic nonvolatile operating parameters to a system, particularly on startup. In the earliest microcomputers, a programming language was sometimes included in ROM. Random access memory (RAM) is dynamically allocated by the system and applications programs. RAM is further distinguished as static or dynamic RAM. Most desktop systems include about 8 to 64 Mbytes of RAM, and may be extended up to 64 or 256 Mbytes. RAM typically operates at about 60 to 80 ns, although this may change as newer, faster types of memory are developed. Most types of computer chip memory are volatile, that is, the contents will disappear if the system is not constantly powered and refreshed. However, there are some types of chips that can retain information, such as erasable, programmable, read-only memory (EPROM) chips.

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The price of memory fluctuates dramatically. In 1986, a megabyte of RAM was $600 U.S.; by the early 1990s this had dropped to $25, then increased again to $120. By early 1998, the price was down to $4 per megabyte. Programmers tend to write code that fills available space. This results in applications that require more memory than many consumers have, setting off another round of buying. In 1978, the TRS-80 computer ran with 4 Kbytes of memory, and with 8 Kbytes it could do word processing and spreadsheet applications quite well. By the mid-1980s, the Amiga computer could multitask and run graphics programs concurrently with stereo sound quite comfortably in 4 Mbytes of RAM. Systems in the late 1990s rarely ran efficiently with less than 16 Mbytes, and most vendors recommended 32. Computers now commonly come installed with 256 MBytes or more. memory leak A memory leak is a characteristic of a software program in which memory is not handled correctly by the application or the operating system (or both), and begins to fill up the system. In other words, as the software is used, more and more memory is allocated without being freed up when it is no longer needed. Eventually, there is no more “working room” for the program and it may freeze, or on some systems, even affect the operating system (although it shouldn’t) and cause spurious problems or system crashes. If the operating system does not clean up the leak on behalf of the application, it will probably be necessary to reboot the machine to clear the problem. Mercator projection A map projection that preserves angular relationships, which is particularly important in marine navigation. mercury vapor lamp A lamp in which mercury vapor flows back and forth through a tube when made horizontal to complete the electric circuit and start the lamp. Ionized mercury vapor is then produced by the heat and current, creating light through the length of the tube. The light is very bright, with a greenish glow, and is generally used in industrial applications. See fluorescent lamp. mesh topology A type of circular network backbone topology in which data can travel back along the backbone if a node becomes unavailable due to a disruption, such as line breakage or failure. The mesh nature of the topology stems from the appearance of the connections between a node and other nodes several nodes away. Some vendors and users prefer this over a ring topology as more than one route can lead to a particular location on the network. See topology. Message Handling System MHS. On a network, MHS provides a means to store and forward messages among MHS users or applications. Unlike traditional telephone networks and the early two-way radio communications, most data networks do not need to establish an end-to-end connection before carrying out communications. Thus, the MHS provides a way to handle the messaging traffic under dynamic circumstances. See X.400 under X Series Recommendations.

Message Security Protocol MSP. A Secure Data Network System (SDNS) protocol for providing X.400 message security. With MSP, a message is given connectionless confidentiality and integrity, data origin authentication, and access control; nonrepudiation with proof of origin; nonrepudiation with proof of delivery. MSP is a content protocol, in the application layer, and is implemented within originator and recipient MSP user agents. It is an end-to-end protocol that does not employ an intermediate message transfer system. MSP processing is carried out prior to submitting a message and after accepting delivery of a message. An X.400 message comprises a content and an envelope. With MSP, a new message content type is defined with a security heading encapsulated around the protected content. Three types of X.509 digital certificates are supported by MSP. The user’s distinguished name and public cryptographic material are bound within an X.509 certificate which, in turn, is signed by a certification authority (CA). The CA manages X.509 certificates and Certificate Revocation lists. message switching A means of switching and multiplexing data packets by storing, queuing, and forwarding the message to the recipient. See circuit switching, packet switching. Message Transfer System MTS. A general-purpose, application-independent, store-and-forward communications service within a Message Handling System (MTS). The MTS uses message transfer agents (MTAs) to relay messages. See Message Handling System. message unit In packet networking, SNA, a basic unit of data processed by any layer. meta-signaling A means to manage User Network Interface (UNI) vacant codes (VCs) signaling and associated broadcast channels incorporating a user part and a network part. Meta-signaling establishes point-to-point signaling VC and broadcast signaling VC (general broadcast and selective broadcast). Metcalfe, Robert (1940s- ) An American engineer and journalist, Metcalfe is the acknowledged creator of Ethernet at Xerox PARC in 1973, along with David Boggs. In 1979 he founded the 3Com Corporation, and since 1990 has been involved with a number of publishing organizations. See Boggs, David; Ethernet. METEOSAT Meteorology satellite. meter A metric linear measure of length/distance equal to 3.28 feet or 39.37 inches. Europe, Canada, and many other regions are standardized on metric measures. The U.S. continues to use the British units of length (e.g., yard) except in scientific circles, where metric is used. Metropolitan Area Network MAN. An urban network of high-speed hosts. See MAE East, MAE West, SMDS. Metropolitan Fiber Systems MFS. A Competitive Access Provider (CAP) founded in the late 1980s. In the 1990s it established its own backbone,

providing national network services. It was subsequently acquired by WorldCom. Metropolitan Service Area MSA. An administrative designation used by many organizations providing commercial and public services in urban areas. The U.S. Government uses the designation for managing and analyzing data from the national census. A Metropolitan Service Area is a city with at least 50,000 residents or an urban area with at least 100,000 residents within the counties encompassing these areas. The Federal Communications Commission (FCC) has used this census designation to recognize over 300 MSAs for the purposes of assigning telecommunications licenses such as cellular telephone licenses. See Rural Service Area. Meucci, Antonio An Italian-born Cuban inventor, chemist, stage designer, and engineer, Meucci made many pioneering discoveries in telecommunications concepts and devices, but his findings were not widely communicated to others, and hence not credited as to their impact on subsequent inventions such as telegraphs and telephones, which made telecommunications history. Meucci developed rheostats, electroplating techniques, and experimented with passing electricity through the human body. While studying mild electrical charges, he discovered the “electrophonic” effect, which related nerve responses to specific applications of current through a wire. By the mid1800s he had developed several devices for creating a vibrating electric current from spoken acoustical impulses. By using a copper strip and delicate animal membranes as diaphragms, he created one of the earliest telephone-like mechanisms. He emigrated from Cuba to the U.S. and applied for a caveat for his teletrofono which was granted in December 1871, 4 years before the patent of Alexander Graham Bell and the caveat of Elisha Gray. It is believed that Bell (and Gray) may have had access to papers describing Meucci’s invention and, due to greater resources and celebrity, overshadowed his inventions. See telephone history. MEW Microwave Early Warning system. A phased radar array antenna system used for security warnings and aircraft control. Meyer code A flag signaling code, employing left and right motions to create characters or syllables, and a forward motion to indicate ends or pauses. This code was in use until it was superseded in the First World War by International Morse code and American Morse code. See semaphore. MFJ See Modified Final Judgment. MFS See Metropolitan Fiber Systems. MFSK See multiple frequency shift keying. MH See Modified Huffman. MHEC See Midwestern Higher Education Commission. mho A practical unit of the measure of conductance, so named because it is ohm spelled backwards. See admittance, ohm. MHS See Message Handling System. MIB See Management Information Base.

Michelson interferometer See interferometer. MICR See magnetic ink character recognition. Micral The first fully assembled 8008-based microcomputer, the Micral featured 8-bit processing and 2 Kbytes of memory. It was designed in France by François Gernelle. The Micral sold for just under $2000, and, like its predecessor the Kenbak-1, was not commercially successful in the United States, an important market for microcomputers. It was introduced in May 1973 before the SPHERE, Scelbi-8H, Mark-8, and Altair computers were introduced in the U.S. See Altair, Kenbak-1, Mark-8, MITS, Scelbi8H, Simon, SPHERE. microbend In fiber optic cables, a small inconsistency, nick, or slight bend that might be introduced into the fiber during manufacture or installation or may occur after installation due to wear and tear. Microbends may introduce small changes in the optical transmissions path as the light “bounces” through the fiber, but are not likely to significantly degrade the signal. However, if the fiber is especially slim or the wavelengths especially long, microbend losses may occur. If there are a large number of microbends, the accumulated effect of the disruption over distance, especially in a cable with a small core radius, may be significant. See macrobend, macrobend loss. MicroCal Module A new type of integrated circuit (IC) designed to facilitate self-monitoring in virtually any type of wireless equipment, including base stations, mobile handsets, and subscriber units. The MicroCal Module scans the entire bandwidth, gathering data which is then fed back to a central maintenance center. The module, designed by Micronetics Wireless, was awarded a U.S. patent in 1996. Micronetics is working with a number of companies, including Nortel and Motorola, to integrate the module into wireless infrastructure equipment. Microcom Networking Protocol MNP. A series of proprietary error control and data compression protocols designed for dialup modems, which are often used in conjunction with industry standard ITU-Trecommended error control mechanisms. For example, MNP-4 works with modems that transmit at data rates up to 14,400 bps. MNP-4 is often implemented in conjunction with the V.42 error control protocol standard from the ITU-T. See Microcom Networking Protocols chart. See V.42. microfiche A somewhat standardized archive system using thin transparent sheets of image-carrying plastic commonly used for the archive of printed matter, especially newspapers, books, journals, etc. Since microfiche information is miniaturized to fit as much data on a sheet as possible, it is typically not human-readable without magnification. Microfiche machines are used for backlighting and magnification. Some photocopiers are designed to enlarge and print microfiche information, although the photocopies are often not very clear. Digital storage techniques are replacing microfiches, but like microfiches, those used are often low resolution and do not retain many of the properties of the originals; unfortunately, also like microfiche archives, the originals

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are often destroyed for lack of storage space and funds. Microfiches are common in libraries, post-secondary institutions, and government archives.

Left: Older microphones were bulky and subject to noise. Right: Newer microphones like this Sennheiser shotgun mic are used for many functions, including camcorder sound, music, public speaking, and videoconferencing over computer networks. [Old mic from American Radio Museum collection. Classic Concepts photos; used with permission.]

microphone A device for apprehending sounds and transmitting them electrically or acoustically to a receiver or audience. A very simple microphone can be created by wrapping stiff paper into a funnel shape, attaching it to a string or wire, and stretching it to a receiver – another funnel on the other end. If

the listener puts an ear near the receiving funnel while the speaker talks into the microphone funnel, the sound, while not loud, can be heard across a room. Add electronics to amplify the signal, and you have a basic microphone. Some microphones also include echo acoustics to make the sound of a voice more resonant. Many singers use this type of microphone to enhance their singing on recordings. Microphones are widely used in camcorders, film cameras, tape recorders, and video recorders. Two microphones are needed for true stereo sound. Microphones can be used as peripherals with computers for the creation of music and other sound samples, or for videoconferencing. See sampling, videoconferencing. Microsoft BASIC A BASIC interpreter first released for the Altair computer in 1975. Paul Allen had seen the feature article on building the Altair in the January 1975 issue of Popular Electronics, so he and Gates talked about it in Harvard Square, and conceived the idea of writing a BASIC interpreter for the new kit-based machine. They contacted MITS, made a proposal, and set to work creating a BASIC that could fit into 4K of memory. The entrepreneurs had previous experience in looking at code for interpreters for various languages based on their business activities together through high school, and 8K BASICs were available for the PDP-8. They developed the BASIC in a simulation environment, since it wasn’t practical to write it on the Altair itself. Allen created a simulation environment for 8080 programming code and modified a symbolic debugger to understand the 8080 instructions. Gates laid out a design for the BASIC interpreter modeled on the BASIC he had encountered on a timesharing system at Dartmouth and began coding it, with assistance later from Allen. Monte Davidoff contributed some of the math routines, especially those for floating point operations. On the plane to Albuquerque to demonstrate

Microcom Networking Protocols Name

Notes

MNP-1

Asynchronous mode, half duplex transfer operation.

MNP-2

Simple error correction scheme, asynchronous mode, full duplex operation.

MNP-3

Error correction incorporated, synchronous mode.

MNP-4

Error correction incorporated, increased throughput. Often included with V.42 modems, along with MNP-5 data compression.

MNP-5

Simple data compression scheme. Often included with V.42 modems, along with MNP-4 error control.

MNP-6

Statistical duplexing and Universal Link Negotiation. Full duplex emulation.

MNP-7

Data compression scheme included.

MNP-8

MNP7 for modems which emulate duplex operation.

MNP-9

Data compression scheme included. Incorporates V.32 technology.

MNP-10

Dynamic fall-back and fall-forward adjusts modulation speed with link quality.

the software, Allen created a bootstrap loader so the Altair would be able to read the data into memory, using a teletypewriter as an input mechanism. (Gates later streamlined the bootstrap loader.) On the first run at the demonstration at MITS, the BASIC didn’t work. On the second try it did. This was a substantial achievement, given the short, hands-off development period and environment. This first BASIC was later ported to many machines. Not long after the Altair kicked off the microcomputer industry, Microsoft BASIC Level II was bundled with the TRS-80 Model I in ROM in 1976, replacing Level I BASIC, and included with the Commodore PET. Microsoft also contributed some routines to the Integer BASIC designed by Wozniak for the Apple Computer, resulting in AppleSoft BASIC. Later, in 1984, Microsoft BASIC was incorporated into ROM on the IBM Personal Computer XT. In addition to the computer-specific 8-bit operating systems, BASIC was ported to run on the popular CP/M-80 operating system designed by Gary Kildall. At this point, Microsoft BASIC was still a text-based program. Microsoft BASIC version 2.0, the first graphicsbased BASIC for the Macintosh, was not announced until fall, 1984, a decade after the text version shipped. In 1985, Microsoft provided a windowing version on floppy diskettes for the Amiga 1000. Later Microsoft BASIC evolved further into Microsoft Visual BASIC, which differed chiefly in that graphically entered structures could be used to automatically generate code. See BASIC, Visual BASIC. Microsoft Data Warehousing Framework A Microsoft commercial open, scalable architecture for creating, using, and managing integrated data warehousing applications. Microsoft Data Warehousing Alliance DWA, MDWA. A trade association for those using and supporting Microsoft Data Warehousing Framework information technology (IT) applications and standards. Microsoft Incorporated One of the earliest companies supporting the microcomputer market, Microsoft was founded by Paul Allen and Bill Gates in 1975 following their partnership as Traf-O-Data, which they formed around 1972. Although Gates and Allen had worked on programming projects together during high school in Seattle, they formalized Microsoft in 1975 in order to market a version of interpreted BASIC for the Altair computer. The trade name was registered in 1977. Paul Allen learned of the Altair computer in a Popular Electronics article he saw in Harvard Square. Since the Altair so closely paralleled an earlier microcomputer hardware idea of his, he contacted Gates to let him know “someone else is doing it.” They then talked in the Square about writing BASIC for the new machine. They contacted MITS, the makers of the Altair, and Allen, Gates, and Davidoff created a BASIC based on Gates’ and Allen’s experience with BASIC interpreters at Dartmouth. Six weeks later, Allen flew south and successfully demonstrated BASIC to MITS in New Mexico, setting the ground-

work for their software development company. The entrepreneurs moved their operations first to the Sundowner Motel across the street from MITS, and later to an eighth floor office in Albuquerque, New Mexico. Allen took a position as VP of Software at MITS, while keeping in regular contact with Microsoft and Gates. They hired high school friends to help out. Meanwhile, Gates began enhancing BASIC and porting it to new platforms that were introduced. When Gates briefly went back to Harvard, Ric Weiland and Marc McDonald formed the core at Microsoft. Marc McDonald designed and coded Stand-alone Disk BASIC, in consultation with Bill Gates. In the late 1970s, Microsoft BASIC was adapted to run on a popular text-oriented operating system called CP/M, developed in various versions by Gary Kildall of Digital Research between 1973 and 1976. After three years in New Mexico, Microsoft relocated to Bellevue, Washington, near the co-owners’ family members. At this location it was easier to recruit programmers as well. Microsoft now has a campus in Redmond, Washington, and has grown to be a large, financially successful enterprise. While it has had occasional forays into hardware development, the primary focus of the company has been software, and a substantial portion of the revenues are derived from operating systems and business-related applications. Paul Allen left the company to invest in a number of other ventures, and formed the Paul Allen Group to oversee his various investments. Allegations of unfair business practices were leveled at Microsoft on numerous occasions during the late 1980s and the 1990s, and the company began to be scrutinized by the U.S. Justice Department. These proceedings are ongoing and are still not completely resolved. Bill Gates was the longstanding CEO until January 2000 when he resigned in lieu of Steve Ballmer who took the positions of president and CEO. Gates continued as chairman and chief software architect. See Allen, Paul; Altair; Gates, William; MITS; Traf-O-Data. Microsoft Mobile Explorer MME. A multistandard microbrowser emulation environment optimized for low-resource devices such as mobile telephones capable of displaying HTML-like markup language pages. See browser, PDA microbrowser. microwave A radio wave transmission frequency (1000+ MHz) generally used for radar and radio repeaters. Microwaves also provide the cooking power for microwave or radar range ovens. The generation of microwaves was initially achieved with magnetrons and Barkhausen-Kurz tubes in the early 1920s. Microwaves were sometimes called radiooptical waves in the early days of their development due to their position on the electromagnetic spectrum between light waves and conventional radio waves, and because some of their characteristics, such as propagation, were similar to light waves. Microwave relay systems were in use as early as the 1930s by AT&T. The original magnetrons were developed into cavity magnetrons and traveling-wave

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tubes. Microwave generators and relays are now an important aspect of satellite communications. Microwaves are also finding increasing use in connecting local area wireless networks (LAWNs). While they are not used for the primary information-carrying aspects within the network, they are useful for interconnecting line-of-site separated LAWNs, or LANs, between buildings. Connection requires a license from the Federal Communications Commission (FCC). See magnetron, microwave antennas, short wave, traveling-wave tube. microwave antennas Due to the very short wavelengths used in microwave transmissions, the physical arrangement of microwave antennas is quite different from those for UHF, VHF, and FM broadcasts. Microwave transmissions are directional for both upand downlinks, quite different from the roughly isotropic, omnidirectional character of traditional television and radio broadcast waves. The common multibranched Yagi-Uda style antennas and fan dipole antennas are inexpensive and appropriate for VHF and UHF reception, but directional parabolic antennas are the norm for microwave signals. The diameter of a parabolic dish antenna is a multiple of the length of the microwaves received and typical dishes range in size from about 2 to about 10 feet across, with the curvature of the dish determining the position of the feed horn which focuses the beams.

Parabolic antennas constructed from mesh or solid materials are used for very short (microwave) radio waves. The curvature of the dish and the related placement of transmitting or receiving horns are important to the quality of the signal transmitted or received. [Classic Concepts photos; used with permission.]

The first transcontinental microwave communication system began operations in 1951 through a system of relay stations between San Francisco and New

York City. Within three years, there were more than 400 additional stations scattered across North America. See antenna, parabolic antenna, UHF antenna, VHF antenna. microwave multi-point distribution system MMDS. MMDS is a system for distributing cable TV programming through microwave communications, more commonly known now as wireless cable. MMDS works in the frequency range of 2.50 to 2.686 GHz, and MMDS service providers are increasing in number. The signals are downlinked from the satellite to the local transceiver, and broadcast from there to subscribers within about a 50-mile radius, depending upon terrain. The subscriber receives the signal on a consumer-priced antenna mounted on or near the home, which is linked through a cable to a “black box” connected to (and sometimes sitting atop) the TV receiver. This box decompresses compressed digital signals and unscrambles signals intended to prevent unpaid/unauthorized viewing of the programs. The MMDS system is in the process of changing from analog to digital technology, opening up opportunities for digital multiplexing through highly linear radio frequency (RF) subsystems, thus providing more television channel choices for viewers. microwave radar Radar systems employing microwaves have been extremely important in navigation, tracking, surveillance, guidance, and communications systems. Much of the early research in microwave radar was conducted at the Massachusetts Institute of Technology (MIT) radiation laboratory in the early 1940s. Mid-Span Meet An interconnection point between two co-carriers. The Mid-Span Meet is the point up to which the carriers provide cabling and transmissions. MIDI See Musical Instrument Digital Interface. MIDI time code MTC. A standard developed to identify timing information associated with a stream of Musical Instrument Digital Interface (MIDI) data. See SMPTE time code. MIDP See Mobile Information Device Profile. Midwestern Higher Education Commission MHEC. MHEC was founded as an interstate agency in 1991 to promote resource sharing in higher education. As a subgroup, it includes a Telecommunications Committee that takes a regional approach to improving access, services, and costs of telecommunications services. Milan Declaration on Communication and Human Rights This declaration was put forth in 1998, based in part on a number of global rights documents, including the Universal Declaration of Human Rights, the International Covenant on Civil and Political Rights, the American Convention on Human Rights, the European Convention for the Protection of Human Rights and Fundamental Freedoms, the Beijing Platform of Action, and other important acknowledgments of human rights. The Declaration asserts the intrinsic relationship between freedom of opinion and expression and the

technologies and venues available for their communication. It declares that “The Right to Communicate is a universal human right which serves and underpins all other human rights and which must be preserved and extended in the context of rapidly changing information and communication technologies, ...” It affirms the need for equitable access to all communications media coupled with the mandate to preserve and sustain cultural rights and diversity. It underlines the importance of not reducing all information users to the category of consumers and affirms their role as communications producers and contributors. It calls for international recognition of community broadcasting as a vital contributor to human freedoms. See People’s Communication Charter. The text of the Milan Declaration is available through the World Association of Community Broadcasters (AMARC). http://www.amarc.org/ Mill Street plant This historically significant power plant began providing three-phase alternating current (AC) in 1893. Partly due to the advocacy of T. Edison, most early power plants provided direct current, so the Mill Creek No. 1 hydroelectric plant was a precedent-setting installation, and many other similar AC power suppliers followed its example. milli- (abbrev. – m) An SI unit prefix for 1 thousandth, 10-3 or 0.001. Thus, a milliamp is 1 thousandth of an ampere. MILNET Military Net. The ARPANET was a historic computer network put into operation in 1969. In 1975, ARPANET was transferred to the Defense Communications Agency. Then, in 1983 it was split into MILNET for military usage, and ARPANET, which evolved into the Internet. MILNET is used for nonclassified U.S. military communications. See ARPANET, Internet. Milstar A joint U.S. Army/Navy/Air Force satellite system for providing jam-resistant communications for wartime requirements for high-priority military users. It is a global constellation of 5-ton geostationary satellites orbiting at about 22,250 nautical miles. The first Milstar satellite was launched in February 1994, the second in November 1995. Six launchings are intended to support four satellites that are active at any one time. The satellites have operational lifetimes of about 10 years. Milstar was designed to link ground, marine, and air command authorities. The satellites relay communications from terminal to terminal, anywhere on Earth. By transmitting from satellite to satellite, ground hops are reduced and security heightened. Milstar terminals provide a variety of data services, including voice, data, facsimile, or teletype communications. MIMD See multiple instruction/multiple data. MIME See Multipurpose Internet Mail Extension. MIN See Mobile Identification Number. MIND Magnetic Integrator Neuron Duplicator. An artificial neuron developed in the early 1960s at the Aeronutronic Division of the Ford Motor Company. MIND imitates the functions of a human neuron.

Mindset computer A delightfully innovative, aheadof-its-time 6-MHz Intel 80186 graphics computer with MS-DOS compatibility, released in 1984. The Mindset, developed by Roger Badertscher and Bruce Irvine, former Atari employees, is so hauntingly similar to the early Amiga, with its good graphics, custom coprocessing chips, and MS-DOS compatibility, that the author asked Jay Miner if there was any relationship. His answer was a definite “no”; he said the machines were independently developed and just happened to converge on the same lines of thinking. Unfortunately, for all its capabilities, the Mindset never caught the attention of the buying public. Miner, Jay (~1930-1994) A gifted design engineer responsible for designing the hardware for the Atari 800 computer, the Amiga computer, and the Lynx color handheld game machine. In 1982, Miner joined Hi Toro to develop the Lorraine computer, which was subsequently sold as the Amiga by Commodore Business Machines. A proponent of open-mindedness and creativity, Miner included his dog’s pawprint inside the case of the Amiga 1000. After the Amiga, he created the Atari Lynx, a fast color handheld game machine. Jay Miner was affectionately known as Padré, the Father of the Amiga, to the computing community. Following a serious illness and kidney transplant, Jay Miner devoted his remaining working life to developing medical devices, such as pacemakers, to aid society. Surprisingly, despite the fact that he understood that the creation of the Amiga was a remarkable achievement, Jay Miner didn’t anticipate the revolution in the video industry that was launched by his creation. In a computing industry where hardware architectures go out of date in a few months, the viability of the Amiga hardware for more than a decade, particularly for graphics and sound, is a tribute to its efficient and insightful design. See Amiga computer, Commodore Business Machines.

Jay Miner was the gifted hardware engineer who designed microcomputers, games systems, and heart pacemakers. He is best remembered as “Padré, Father of the Amiga.”

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MiniDisk A very compact audio/data magnetic storage medium designed by Sony for sound and computer data storage, popularly used for playing music in portable MiniDisk audio players. minifloppy A generic term for a number of floppy diskette technologies that store almost ten times as much data as a regular 3.5-in. floppy, but which are designed by some manufacturers to be downwardly compatible with 1.4-Mbyte drives. The price of storage on these high capacity floppies is substantially cheaper, and they may, in time, supersede current floppies. minimal shift keying MSK. A type of modulation technique similar to quadrature phase shift keying (QPSK), except that the rectangular pulse in QPSK is a half-cycle sinusoidal pulse in MSK. See modulation, phase shift keying. minimize button, iconize button Graphical user interfaces on several different operating systems include a small gadget on application or display windows which, when clicked, will shrink the window down to an icon. Thus, the program is available and can quickly be retrieved by double-clicking the minimized icon without shutting down the process and rerunning the program. Ministère des Postes et Télécommuicaciones The telecommunications authority for the Democratic and Popular Republic of Algeria. Online communications are in French. Ministerio de Comunicaciones The telecommunications planning and regulatory authority of the Republic of Columbia in South America. http://www.mincomunicaciones.gov.co/ Ministry of Information Technology and Telecommunications MITT. The Mauritius ministry that handles the formulation and implementation of government policies in telecommunications and information technology. Telecommunications are governed by the Mauritius Telecommunications Act 1998. Online services are designed and published by the National Computer Board. http://ncb.intnet.mu/ mitt.htm Ministry of Posts and Telecommunications MPT. The Japanese radio regulatory administration, MPT oversees radio communications, based upon the Radio Law of 1950. The MPT grants radio station and operator licenses, monitors and inspects stations and radio frequencies, and sets technical standards for radio equipment. http://mpt.go.jp/ Ministry of Telecommunications The telecommunications authority of the Lebanese Republic under the direction of the Minister of Post and Telecommunications. http://www.mpt.gov.lb/ Ministry of Telecommunications and E-Commerce The authority in Bermuda that oversees telecommunications, broadcasting, and frequency administration. http://www.mtec.bm/ Minitel A French Telecom service that provides free terminals for chat and electronic telephone directory videotext services. It is similar to the German Bundespost’s interactive videotext system. See Minitel.

MIP See Multichannel Interface Processor. MIPG See Multiple-Image Portable Graphics. MIPS million instructions per second. A measure of processor speed used in system design and cross-system comparisons. MIPS describes the average number of machine instructions that a central processing unit (CPU) performs per unit of time of 1 second. This is a narrow definition of performance, as many other factors influence overall speed and efficiency. The Digital VAX-11/780 is defined as a baseline at 1 MIP. Most consumer desktop models now deliver about 3 to 10 MIPS. High-end minicomputers and mainframes can range from 10 to 50 MIPS, with supercomputers comprising the top of whatever is state of the art at any particular time. See benchmark. Mir A landmark “permanent” Earth-orbiting space station used for observation, experimentation, and scientific research about living and working in space. U.S. and Russian Mir missions began early in 1995, with the core module launched in February 1986. Mir consisted of a number of connected modules, docking components, solar screens, life support systems, and scientific instruments. The Mir capsule could hold two or three people fairly comfortably, and up to six for short periods of time. Travellers to and from Mir connected through the NASA space shuttle. Amateur radio enthusiasts enjoyed regularly listening to Mir signals, and some have sent transmissions to the orbiting station. Commonly used Mir amateur radio wave transmission frequencies included: Mode

Frequency

uplink

145.200 MHz

downlink

145.800 MHz

Mode 1 Repeater/FM uplink

435.750 MHz

Mode 1 Repeater/FM downlink 437.950 MHz Mode 2 packet uplink

435.775 MHz

Mode 2 packet downlink

437.975 MHz

Mode 3 QSO uplink

435.725 MHz

Mode 3 QSO downlink

437.925 MHz

A great deal was learned about the wonders and challenges of living in space from Mir. Information and photographs related to Mir missions can be seen through the Office of Space Flight Web site. After orbiting the Earth for more than 15 years, the space station entered the Earth’s atmosphere, in a controlled decline, on March 23, 2001. http://www.nasa.gov/osf/mir MIR See multimedia information retrieval. mirror A highly polished surface, usually of silvered glass or metal, which readily reflects light. Mirrors were used for line-of-sight signaling long before electrical telecommunications methods were available. Hikers still regularly carry them for emergency

signaling in the wilderness. Mirrors are also used in many types of computer devices, especially those which incorporate laser beams, such as laser printers. The mirror serves to direct the beam inside the mechanism onto the appropriate areas, such as a printing drum. See heliograph. mirror site A computer file archive site that maintains duplicates of files existing on another system. Some mirror sites reflect not only the files on the other system, but also the entire file and command structure. Mirror sites exist to protect data from loss and also to provide alternate access to popular files, in case the original site is slow to respond or has become inaccessible. FTP sites often have mirror sites, sometimes in other countries. mirroring A means of providing system backup security by replicating data in different locations. The system can go to the mirror location if the original storage of the data becomes corrupted or the system can be restored with information from the mirror. Redundancy is a very common property of computer systems. Some will mirror whole directory structures and files as a matter of course. Some hard drive systems are set up to constantly mirror information over several devices. While mirroring almost inevitably costs a little more in terms of memory or storage space and in processing time, it is usually worthwhile. See mirror site, RAID.

A dramatic image of Mir docking alongside the Space Shuttle with the swirling clouds of Earth below. The Mir Space Station was a historic space operations and research lab that orbited for more than 15 years. Personnel aboard the Mir station came and went via the Space Shuttle. It was possible for civilians to communicate with Mir via amateur radio signals when the station orbited overhead within transmission range. [NASA/Marshall image, 1996.]

MIS See Management Information Services. MITS Micro Instrumentation and Telemetry Systems. The historic creators of the Altair microcomputer, MITS, under the direction of Ed Roberts, originally sold radio transmitters (telemetry devices) for

model planes. These products did quite well and got the company under way, but when the company moved into the area of calculator kits, there was a lot of competition from bigger names like Texas Instruments, and the Altair was in essence an effort to stave off bankruptcy. MITS developed the MITS 816 in 1972, and later the historic kit for the Altair 8800 in 1974. While the Altair is not the first microcomputer, it is to be credited as the first commercially successful microcomputer. In spite of the success of the Altair, the company was sold to Pertec, a manufacturer of peripherals. See Altair, Intel MCS-4, Kenbak-1, Mark-8, Micral, Scelbi. MJ modular jack. Any jack designed to interconnect readily with various standardized receptacles in a circuit system. See RJ. MLA See mail list agent. MLPP multilevel precedence and preemption (e.g., as in ISDN Q.85 and A.735 community of interest services). MLS microwave landing system. MM man-machine. MMC 1. minimum monthly charge. 2. See Mobile Multimedia Communication project. 3. See MultiMediaCard. MMCA See MultiMediaCard Association. MMCF See Multimedia Communications Forum. MMCX See Multimedia Communication Exchange. MMDC 1. See Massachusetts Microprocessor Design Center. 2. See Multi-Media and Digital Communications lab. 3. See Multi-Service, Multi-Carrier, Distributed Communications. 4. See multimedia desktop collaboration. 5. See Multimedia Development Center. 6. See multimodel data compression. 7. See Multiple Module Data Computer. MMDS See microwave multipoint distribution system. MME 1. See Microsoft Mobile Explorer. 2. See Mobile Meteorological Equipment. 4. See Multimedia Message Entity. MMF 1. See Mobile Management Forum. 2. See multimode optical fiber MMI machine-to-machine interface. Since this can easily be confused with the abbreviation for manmachine interface, which was also traditionally MMI, it is preferable to use HMI for human-machine interface. MMIC See Monolithic Microwave Integrated Circuit. MMM See multimedia mail. MMMS See Multimedia Mail Service. MMMSec See Multimedia Mail Security. MMS 1. marketing measurement system. 2. memory management system. 3. meteorological measurement system. 4. module management system. 5. multimedia survey. MMSI 1. Manchester Museum of Science & Industry. 2. See Maritime Mobile Service Identity. MMSP See modular multi-satellite preprocessor. MMSS Maritime Mobile-Satellite Service.

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MMTA See Multimedia Telecommunications Association. MMU 1. Manned Maneuvering Unit. A human maneuvering unit used in untethered space walks originating from the U.S. space shuttle missions. 2. memory management unit. Computer circuitry often built into central processing chips to handle administration of blocks of storage. MMUSIC See Multiparty Multimedia Session Control. MMX Multimedia Extension. Matrix Math Extension. See Pentium MMX. mnemonic A memory-jogging device such as an acronym, abbreviation, rhyme, or pun. For example, “I before E, except after C.” Programmers often use mnemonic variable names to keep track of code, and will implement mnemonic hot-key shortcuts for the benefit of users. MNLP See Mobile Network Location Protocol. MNP See Microcom Networking Protocol. MNRP Mobile Network Registration Protocol. mobile assisted handoff MAHO. A process in which the handoff of a voice channel by a mobile station is assisted by the base station by providing information on the surrounding radio frequency (RF) signal environment. Mobile Broadband System MBS. A wireless cellular network developed as one of the European RACE II Integrated Broadband Communications (IBC) projects. The purpose of the project was to develop third-generation, integrated mobile systems as part of a universal, cost-efficient, voice/data personal communications system. MBS transparently transports Asynchronous Transfer Mode (ATM) cells over the air interface at 60 GHz at data rates up to 34 Mbps (with higher rates possible through multicarrier transmission). Two recommended sub-band frequencies for MBS are 62 to 63 GHz and 65 to 66 GHz. MBS is supported over B-ISDN systems and differs from traditional cellular by its bursty nature and dynamically adjusting data transmission rates. A new channel structure and protocols have been developed in conjunction with the project to exploit the packet characteristics of B-ISDN connections. See Integrated Broadband System, Research into Advanced Communications in Europe. Mobile Data Base Station MDBS. In CDPD mobile communications, a system which provides data packet relay functions between the Mobile End System (M-ES) and the Mobile Data Intermediate System (MD-IS). See Cellular Digital Packet Data. Mobile Data Intermediate System MD-IS. In CDPD mobile communications, a system which provides routing and location management functions, utilizing a Home Domain Directory (HDD) database. The MD-IS communicates with the Mobile End System (M-ES) through the Mobile Data Base Station (MDBS). See Cellular Digital Packet Data. Mobile End System M-ES. In CDPD mobile communications, the system through which the subscriber accesses wireless network services. M-ESs

include modems installed in laptops, palmtops, personal digital assistants (PDAs), etc. See Cellular Digital Packet Data. Mobile Identification Number MIN. Each wireless phone is assigned an identification number by the carrier. The MIN is not attached to the individual, as the phone may change hands or the individual may change locations. Mobile Information Device Profile MIDP. A specification supported by a number of major wireless telecommunications service providers, MIDP is a set of Sun Java APIs that is part of the J2ME application runtime environment for mobile information devices, along with the Connected Limited Device Configuration (CLDC). MIDP was developed through the Java Community Process. It specifies aspects of storage, application life cycle, networking, and user interaction. MIDP for PalmOS is an implementation of CLDC and MIDP optimized for PalmOS handheld platforms. Mobile IP, Mobile Internet Protocol Mobile data networking through the Internet is coming into demand as the number of laptops and the availability of wireless modem services increases. Since the problems of maintaining contact with a network and network security are concerns on mobile systems, a set of extensions to Internet Protocol (IP) is being developed to handle the special needs of mobile users. Mobile IP uses a dual addressing scheme so that the communications node and the mobile unit can be tracked and administered. In simple terms, the location of the mobile system becomes a forwarding address to which packets are retransmitted. Security is incorporated to prevent an unauthorized person from intercepting the transmission. See Foreign Agent. Mobile Management Forum MMF. A forum of the Open Group, announced in May 2000, as a means to pursue the objectives of the Open Group Wireless and Mobile Program. The MMF supports and promotes the deployment of interoperable wireless applications and devices into enterprise environments. http://www.opengroup.org/mobile/ Mobile Maritime Committee MMC. An informal committee of the U.S. Coast Guard that has existed for some time to express and address local maritime issues and problems. In February 2000, a more formal organization was established to promote actions to improve the safety, security, mobility, and environmental protection of the Mobile, Alabama, port. Members consist of port and waterway users and regulatory agencies. See Marine Safety Office. Mobile Meteorological Equipment MME. Through the work of the Ad Hoc Group for Mobile Meteorological Equipment (AHG/MME), the Federal Directory of Mobile Meteorological Equipment and Capabilities was prepared to assist agencies in individual responsibilities and planning activities in response to requirements and emergencies. The Directory catalogs mobile meteorological equipment, software, and capabilities of U.S. Federal departments and agencies to facilitate interagency

cooperation. The Department of Defense (DoD) has been particularly active in the development and deployment of mobile systems. Mobile Multimedia Communication project MMC project. A multidisciplinary research project coordinated within Delft University of Technology in the Netherlands. The MMC project was established to research solutions to wired and wireless Internet-style applications and bandwidth applications as they can be adapted to mobile networks such as cellular systems. The project ran from April 1996 to September 2000. Some of the work in the project has been transferred to the UbiCom (Ubiquitous Communication) program. Mobile Network Location Protocol MNLP. In CDPD mobile communications, the MNLP provides a means to track the Mobile End System (M-ES), that is, the laptop modem, cellular phone, or other device that allows the user to link into the network, and to interlink the Home Mobile Data Intermediate System (MD-IS) and the Serving MD-IS. This works in conjunction with a Mobile Network Registration Protocol (MNRP) to verify the user’s Network Entity Identifier (NEI), a security ID used to monitor and confine service to authorized users. Mobile Network Registration Protocol MNRP. See Mobile Network Location Protocol. mobile phone An audio broadcast system designed to provide mobile communications through hardware interfaces resembling traditional phone handsets. The earliest mobile phone systems were bulky, limited contrivances developed after the turn of the century and first demonstrated in 1919, but they were acknowledged as having an important place in future communications. Historically similar to broadcast TV, a powerful transmitter was located to provide maximum range, up to perhaps 30 miles, for traveling subscribers. To increase the limited range and channel distribution of the single tower design, cellular networks were developed, which increased available bandwidth by providing many lower power transmitters, closely located to one another, over a wide geographic region. There are now a number of types of mobile phones, from short-range FM cordless phones with a range of a few hundred feet, to digital PCS and cellular systems with roaming capabilities that range from hundreds to thousands of miles. See cellular phone. Mobile Solutions Partner Program MSPP. A Microsoft program initiated in August 2000 to promote development of mobile communications solutions based on .Net Mobile Web technology. MSPP supports vendors who are developing for the Microsoft Pocket PC operating system. The program was initiated in part as a competitive response to Palm’s business lead in the mobile communications industry. Mobile Subscriber Unit MSU. A main component of a mobile phone system consisting of a portable or transportable control unit and cellular radio transceiver. Convenience, size, transceiver power, and battery life are traded off in the various systems. Larger, more powerful units may be mounted to car

batteries, and often split the telephone and the handset into separate units. Smaller handhelds frequently have less range and shorter battery life. See cellular phone, mobile phone. Mobile Telephone Switching Office MTSO. A main component of a mobile phone service, which performs wireless relaying, switching, and administration tasks similar to those carried out by a wired telephone switching office, except that it must handle the specific technical needs of users who are moving and roaming (changing from one transceiving area to another) with signal monitoring and processing, handoffs, etc. In addition, the MTSO handles the link between the mobile services and connections to wireline services, as many mobile services are actually hybrid technologies, often taking calls from mobile users and connecting them with a wireline destination, and vice versa. Mobilization Against Terrorism Act MATA. See Anti-Terrorism Act of 2001. Mockapetris, Paul The developer of the JEEVES DNS Resolver, the first implementation of the Domain Name System, now incorporated into the Internet. Mockapetris is responsible for a number of significant Request for Comments documents related to the development of the Internet. His DNS Resolver spawned several subsequent implementations, the most significant being the Berkeley Internet Name Domain (BIND). In June 2001, Mockapetris was announced as Chairman of the Board for Nominum, Inc., a naming and address management solutions provider. See JEEVES DNS Resolver. modal In applications programming, a type of user window, dialog, or other input or information display operation which does not suspend access to other processes. For example, suppose the user has selected a Quit function, and the software displays a dialog box that says, “Do you really want to quit? If so, the program will end without saving.” Options to Quit or to Cancel will be presented. If the dialog allows the user to go back to the application without responding to the Quit/Cancel query, the operation is modal. If the user must reply before continuing with using the software, then it is not. While modal (multitasked) operations are preferred in many situations, in others, a response should be solicited before continuing, especially if it involves the possible loss of data. mode In some older operating systems, a distinction was made between text mode and graphics mode, but most systems now work in graphics mode with text represented graphically. This system is more flexible. modem modulator/demodulator. 1. A device which modulates and demodulates a signal. Digital data are typically modulated to be carried over analog transmission systems, and broadcast waves are modulated to add information to the carrier band. These are then demodulated again at the receiving end. 2. A computer hardware peripheral specifically designed to convert the digital signals generated by the computer into analog systems that can be carried across an analog transmissions medium such as twisted-pair copper wire, and demodulate them back into digital data

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at the receiving end. Many standards exist for the transmission of this type of data, and the sending and receiving modems must be able to negotiate a common format in order for the signals to be meaningfully received. Current modems commonly transmit at rates of 19,200 bps, 38,400 bps, and higher; most include facsimile transmission capabilities, and some include voice mail capabilities as well. They incorporate a number of error control, data compression, and modulation protocols in order to maximize speed of transmission over lines that people once claimed could never transmit data faster than 600 bps. See error control protocol, data compression protocol, modulation protocol, serial port.

Two different computer modems: the Global Village on the left has a built-in 9-pin DIN connector, and operates at 33,600 bps; the SuperModem on the right has a standard 25-pin connection supporting V.34 standards. Each can be connected (daisy-chained) with a regular telephone set.

modem pool A set of modems usually servicing a network through which several users can dial out of the system, or through which a number of users can dial in, as to a BBS or Internet Services Provider (ISP). Most higher educational institutions have modem pools for users to access the system from home or classrooms, or through which they can dial out to community services or extra service providers. Often the modems in a pool will have different characteristics. For example, only a few lines may be high speed lines, due to higher cost, and the remainder may be a variety of slower, less expensive modems. Some modem pools are extremely large. For example, one of the largest commercial Internet providers has over 100,000 modems in its pool. A pool is a flexible way to maximize resources. A dozen modems can service a hundred workstations, provided the users do not need constant access to dialup resources. It is also easier for system administrators to carry out hardware maintenance and to maintain security when the modems are grouped and placed in a secure environment. modem server A networked workstation application which manages the administrative and access tasks associated with a modem pool, or an intelligent modem hub which manages incoming and outgoing data

from more than one user. In large modem pools, a system may be dedicated to assigning user requests for modems, for sending messages to the user (e.g., “All systems are currently busy, please make your request again in 15 minutes.”), for evaluating which modems to allocate first (there may be different modems with different capabilities, such as access speed), and for assigning priorities and connect times, when appropriate. modem standards This is one of the areas where de facto vendor standards and industry standards (e.g., ITU-T V Series Recommendations) have continually leapfrogged one another, and engaged in an uneasy competitive race. The constant consumer demand for faster modems and the vendor desire to be the first to market with the next generation modem, have caused many vendors to develop their own standards ahead of the global cooperative standards process. For this reason, many modems are dual-standard modems, in order to support both the vendor and generally accepted industry standards. Some modems support either vendor or industry standards, which are often not compatible, and it is important to find out their status before purchasing. In many cases, the early versions of modems supporting the faster speeds are the ones most likely to go out of date quickly. In the early days, many vendors followed Bell and Hayes standards, whereas in recent years, vendors have tended to go with the industry standards once the specifications are finalized and made available. The Hayes command set remains, although most vendors implement a superset of the original Hayes commands, which were quite simple and limited. The Microcom Network Protocol standards for error control and data compression are widely supported modem standards. See Microcom Networking Protocol, V Series Recommendations. moderated discussion list A public or private online discussion, usually carried out through email or a Web page gateway, in which the messages are screened and sometimes edited before being posted to everyone on the group. Moderated discussion lists used to be extremely rare. In the 1980s thousands of open lists were kept on topic through voluntary cooperation. Since about the mid-1990s, however, many online discussion lists were ruined by inappropriate use, especially the posting of advertisements for sex sites and get-rich-quick schemes, resulting in some lists being shut down and many others going to moderated status. This is a lot of work for the moderators, who are almost always volunteers, and who have to read everything and decide whether it is appropriate for the list. These unsung heroes deserve a great deal of appreciation for keeping good lists alive, as many have been lost due to abuses of the system. See discussion list, newsgroup. moderator A person who presides over a meeting or discussion. On the Internet are a vast number of public discussion groups and, as the number of participants increases, many of these groups have gone to moderated status. For example, the business groups have become so cluttered with messages

promoting get-rich-quick schemes that the only good business groups remaining are those that are moderated. Moderators, usually called ops, also help to maintain order and appropriateness on open chat lines. Internet moderators are typically hard-working volunteers who take time to read messages and edit or reject those inappropriate to the stated charter of the group. In the early days of the Internet, moderated groups were almost nonexistent. Unfortunately, in the mid-1990s, the need for moderation increased due to repeated abuses of the system. See Net Police, Netiquette, Netizen. Modified Final Judgment, Modification of Final Judgment MFJ. The name given to a historic 7-year antitrust lawsuit between the U.S. Justice Department and AT&T, which resulted in the breakup of AT&T. It is associated with Judge Harold Greene’s decision regarding the 1983 to 1984 (clarification and revision) divestiture of AT&T. Under this judgment, AT&T was permitted to retain ownership of Bell Laboratories and AT&T Technologies (Western Electric), but the Regional Bell Operating Companies (RBOCs) were banned from manufacturing, and Local Access Transport Areas (LATAs) were created rather than retaining the existing local exchange boundaries. Prior to the MFJ, charges were handled through Division of Revenues, but this was changed to an access charge tariff system. See AT&T, Kingsbury Commitment, Local Exchange Carrier, Willis Graham Act of 1921. Modified Huffman MH. Huffman is a variablelength, tree-oriented data encoding scheme that optimizes on the basis of more frequently occurring characters in order to achieve compression in fewer bits. Modified Huffman is widely used in facsimile

transmissions. See Huffman encoding. modular Composed of separately organized entities, loosely or tightly coordinated or connected to create a larger whole. Modular programming is programming in which the larger application is composed of smaller associated elements such as blocks, objects, primitives, self-contained functions, etc. Object-oriented programming is a type of modular programming. A modular office is one in which the individual components of the facilities can be changed around fairly easily; that is, desks, screens, phones, cables, etc. can be rearranged without undue effort. A modular phone system is one in which handsets or phone sets can be unplugged and moved or rearranged within a building or department. Modular software is software in which a number of separate or related utilities, tools, and functions can be used together in a number of ways. For example, there may be a variety of functions that do file conversions, image processing, filtering, special effects, etc. which can be used separately or in conjunction with a variety of programs. Some of the more flexible, standalone “plugins” exhibit these properties of modularity. For example, there may be a watercolor plugin which can be used independently to alter the contents of a graphics file, or may work as a plugin in the context of several programs such as an image processing program, a drawing program, etc. modular multi-satellite preprocessor MMSP. A frame synchronizer designed to provide an interface between a host computer and synchronized mapper telemetry data. The MMSP takes the raw telemetry data, frame aligns and samples it, and transmits the information to the host computer, where it is further processed and the image information extracted from the data.

Radio Frequency Transmission Schemes Format

Abbrev.

ALOHA

Code Division Multiple Access

Notes A free-for-all style of transmission; any source transmits at any time, and continues to transmit if there is an acknowledgment. It is not a highefficiency method, but there are circumstances where it is practical.

CDMA

A hybrid scheme which incorporates time/frequency multiplexing to provide spread spectrum modulation. Thus, central channels can be handled without timing synchronization.

Frequency Division Multiple Access FDMA

A traditional method of channel allocation in which bandwidth is subdivided into frequency bands, with guard bands providing a buffer between channels.

Packet Reservation Multiple Access

A type of enhanced TDMA which incorporates aspects of S-ALOHA. Suitable for mobile transmissions.

PRMA

M

modulate To change gradually from one state to another. To tune or adjust. To vary the amplitude, frequency, or phase, typically to add information to a carrier wave. To change the velocity of electrons in an electron beam, as in a cathode-ray tube. modulation A key element in the transmission of information. By changing or modulating an electrical pulse through a wire or other conducting medium, or an airborne electromagnetic wave, it is possible to convey information. Similarly, by manipulating its intensity and duration, light can be modulated to send information. Some of the simplest forms of modulation include turning a signal on or off, or varying it between high and low states. For computer users, one of the most familiar modulating devices is the dialup modem, which takes a digital signal from the computer and modulates it to be carried over analog phone lines. At the receiving end, a modem then demodulates the signal, turning it back into digital signals that are transferred to the receiving computer. There are many modulation techniques used throughout the telecommunications industry, some very simple, and some so sophisticated only computers can control them. The most common types of modulation are amplitude modulation (AM), frequency modulation (FM), and phase modulation (PM). Sometimes different modulation schemes are combined. Each scheme has its own unique characteristics. Early detractors said frequency modulation was mathematically impossible, but Edwin Armstrong demonstrated, after 10 years of hard research applied to the problem, not only that it could be done, but also that it was a great thing. It has since been used in thousands of applications from radio programming to cordless phones and burglar alarm systems. Another important contribution to modulation was the work of John R. Carson, who demonstrated how a portion of a modulated signal could be transmitted, instead of the whole thing, and the original signal rebuilt at the receiving end, thus reducing bandwidth without loss of information. See amplitude modulation; Armstrong, Edwin; frequency modulation; phase shift keying; quadrature amplitude modulation; single sideband. modulation protocol A data encoding technique used to convert digital data into analog signals. This determines the raw (uncompressed) speed at which the modem can transfer data. Current modems incorporate more than one protocol. See modem. modulation, light A means of conveying information by manipulating a beam of light. The light can be directly influenced, by turning it on or off, or varying its intensity; it can be indirectly influenced by interposing shutters, gels, or other objects between the sender and the receiver. Light modulation is used in fiber optic transmissions, with lasers and lightemitting diodes used as common light sources. moiré 1. In raster-oriented imagery, moiré is a visual artifact that appears as an undesirable, distracting secondary pattern which disturbs the intended

appearance of the image. 2. In traditional printing on a press, especially process color printing, small dots are often interleaved to simulate the appearance of more colors. If the angles and patterns of these dots are not carefully controlled, a moiré pattern, resembling light through silk, may emerge. Better desktop publishing programs provide print settings to set the angle and type of halftone to match the technology on which the job is printed. 3. In video images, mixing high frequencies can create an undesirable, visible, low-frequency moiré. moisture barrier A cover, sheet, bag, or other barrier, usually plastic, intended to retard or prevent moisture from coming in contact with building structures, wires, or electrical components. Moisture barriers are used to prevent rot, condensation, and electrical short circuits. molding raceway A channel system incorporated into wood, plastic, or metal moldings to hold, protect, and direct interior wiring circuits. Molding raceways are of modular construction with a variety of fittings, so individual sections can be interconnected and holes can be punched where needed. Molding raceways are commonly used on baseboards and wainscots, where they blend naturally with the decor. See raceway. monochrome monitor A monitor that displays only one color of illuminated phosphor on a contrasting screen. The color is usually white, green, or amber against a dark background, or black against a light background. When the intensity of a monochrome monitor is varied, all the pixels get brighter or dimmer, with no capability of individually setting the intensities. A grayscale monitor, on the other hand, also uses only one color of illuminated phosphor, but each pixel can be individually controlled for its intensity, allowing 16, 32, or 256 shades of gray to be represented. Grayscale monitors make very good work environments for correspondence and desktop publishing, and some are designed in portrait mode (or can swivel between portrait and landscape mode) to more closely recreate the orientation of a piece of paper. Monolithic Microwave Integrated Circuit MMIC. Analog circuits incorporating a number of integrated functions operating at microwave frequencies. Many types of MMICs can be purchased for $5 or less per chip. MMICs provide support for wireless communications technologies, making it possible to design low-cost, high-bandwidth data transmissions links. MMICs can be used to convert between baseband and modulated microwave signals and, as such, can be used in conjunction with traditional integrated circuits (ICs) handling the baseband signals. MMIC arrays developed by the NASA/Lewis Research Center and the Air Force Rome Laboratory were demonstrated in the mid-1990s in conjunction with NASA Advanced Communications Technology Satellite (ACTS) technology. These proof-of-concept MMIC arrays were in the K/Ka-band frequencies, indicating that high-density MMIC integration at 20 and 30 GHz was feasible.

Once MMICs became commercially available, they began to be of interest for many types of commercial and scientific applications. The Search for Extraterrestrial Intelligence (SETI) League, for example, considers the technology useful for constructing research devices for space communications and the possible interception of communications emanating from other regions of the Universe. The Wireless Systems Innovation lab of NTT has developed uniplanar and multiplanar MMICs more compact and less expensive than earlier technologies that are suitable for radio, wireless area networks (WANs), and satellite transponders. With MMICs incorporated into beam-forming networks, it is envisaged that Earth station satellite terminals can be designed to be as small as cellular telephones. monopole A slender self-supporting tower used for attaching wireless and antennas/aerials. monospaced font, fixed width font A font in which each character in the set is of one fixed width, usually equal to the widest character plus a slight bit of space to the right, so that letters don’t touch when strung together. Monospaced fonts lack the aesthetic properties of proportional fonts because the letter width is not related to the visual width of the individual characters. Thus, the letter i will have the same width as the letter w with some extra space that may look unappealing. Monospaced fonts are used with printers and typewriters that lack the capability of moving the printhead in small, varying increments. Monospaced type also takes more space on the page, allowing fewer characters, because of the extra white space. Contrast with proportional font. proportional iiiiiii wwwwwww fixed width iiiiiii wwwwwww Moonbounce, Earth-Moon-Earth bounce EME. A means of using the Moon as a passive reflector for communications signals. Due to the great distances involved, very large antennas and strong signals are required, but given these in conjunction with the right weather conditions, Moonbounce transmissions have been demonstrated. The first Moonbounced signal was recorded in January 1946 in New Jersey, where army engineers used a recently invented FM transmitter and receiver developed by E. H. Armstrong to send pulses to the Moon, which returned as a slight hum. This was a significant achievement as it not only showed the potential of FM broadcasts, but also demonstrated that radio waves could pass through the ionosphere and beyond. Moore, Gordon E. (1929- ) An American chemist and business executive, Moore cofounded Fairchild Semiconductor, then Intel Corporation, in 1968, along with Robert Noyce, one of the inventors of integrated circuit technology (1959). In 1975, Moore became President and CEO until elected chairman and CEO in 1979. He retained the position of CEO until 1987 and became chairman emeritus in 1997. In May 2001, Moore retired from the board, having reached the age at which he had set mandatory retirement from the corporation.

Moore is a fellow of the IEEE Society and Chairman of the Board of Trustees of the California Institute of Technology. He was awarded the National Medal of Technology in 1990. See Intel Corporation; Moore’s law; Noyce, Robert.

M Gordon E. Moore, cofounder of Intel Corporation not only cofounded and headed up one of the most successful computer chip companies in the world, but is also well remembered for his predictions about semiconductor evolution now encapsulated as “Moore’s law.” [Photo copyright Intel Corporation; used according toIntel Press Room conditions.]

Moore’s law Semiconductor chip technology will roughly double in capacity (and circuit density) about every year or so (later revised to every 2 years). This prediction, charted by Gordon E. Moore at a speech in 1965, turned out to be memorably prescient and has since been the basis for many industry planning decisions and forecasts. See Gilder’s law; Moore, Gordon. Morse code A system of character encoding using dots and dashes, or long and short sounds or lights, that can be readily sent over distance over many types of transmission media due to its simplicity. International Morse code (continental Morse code) and American Morse code (railroad code) have been derived from this. Morse code is flexible in that it can be sent with tones, clicks, dots and dashes, and lights, in a variety of media. In 1862, two Philadelphia inventors patented a signal light system using a shuttered oil lamp for sending Morse code which was intended to be mounted on the masthead of ships. International Morse code developed from AustroGermanic code, a variation on Morse code used in radio transmissions partly because American Morse code, while suitable for telegraph communications, was more difficult to interpret over radio waves. In 1851 it became the code of choice for transatlantic cable communications. Basic skill in Morse code has

been a requirement of receiving amateur radio licenses for many decades. The code was apparently developed by Morse’s collaborator, Alfred Vail, and is named for the inventor of the printing telegraph, Samuel F.B. Morse. See Morse code history. Morse code history The original paper tape printing telegraph designed by Samuel Morse employed a system of numbers which were then correlated with words, according to a lookup reference. The lookup reference developed by Morse was very large and the system itself somewhat slow and cumbersome; it required the maintenance of a reference and the somewhat arbitrary assignment of nonmnemonic code number sequences to every word. A more simple, direct system was needed. Alfred Vail was from a family of fabricators and acted for years as assistant to and collaborator with Samuel Morse. Mechanically adept, he built many of the mechanical components designed by Morse. In the process of creating the mechanisms for the Morse printing telegraph key, Vail changed the orientation of the keying mechanism from horizontal to vertical, thus providing a more comfortable hand position. The change also resulted in a stylus which would lift up from the paper, leaving dots and dashes, rather than zigzag-shaped dips on the tape record that Morse’s original mechanism produced. Vail’s assistant, Baxter, reported to Franklin Pope that Vail set to work simplifying Morse’s unwieldy lookup code system. Vail apparently visited local printers to analyze typesetting cases to determine the frequencies of letter usage. Pope subsequently reported the story in 1888 in The Century: Illustrated Monthly Magazine. The code Vail developed evolved into American Morse code, and International Morse Code became a further streamlined variation. As Morse’s assistant, Vail had agreed to turn over his inventions to the elder inventor. [Thanks to Karen Weiss and B. Neal McEwen for unearthing and reporting Vail’s possible unacknowledged contribution to history.] Morse sounder A type of early telegraph sounding instrument, which used audible clicks to broadcast the incoming message rather than a paper tape printout, which was slow. The sounder incorporated an electromagnet as a pole piece, mounted on a pivoting sounding lever with two stop positions. Releasing the magnet as it was energized produced the clicking sound. The duration of the clicks represented the coded dots and dashes of the Morse code system and were interpreted aurally by the receiving operator. Typically the sounder was connected to the sending instrument with only one wire. The viability of the single wire circuit was observed by Steinheil in 1837 in Germany, and independently the following year by Morse in America. Both discovered that a second wire was not needed to complete the circuit if the two instruments were connected through the ground, using it as the return path for the circuit. This worked even over distance. Morse, Samuel Finly Breese (1791-1872) An American artist and inventor in the 1800s chiefly

known for the code that bears his name. He was a respected artist and one of the founders of the National Academy of the Arts of Design. In the 1820s he became increasingly interested in science and invented electromechanical telegraph devices, some of the first inventions to use electricity for communication. With advice and assistance from J. Henry and L. Gale, Morse was able to construct a basic working design for the telegraph by 1837. Samuel Morse demonstrated his invention to the presidential administration in 1838 and in 1843 won funding support from the U.S. Congress to construct a telegraph line between Baltimore and Washington, D.C. He sent his first public message over this line in May 1844, an event that launched a revolution in communications. Morse became friends with the Vail family, who were talented fabricators and were able to assist him in constructing practical working models of his ideas. Many of Morse’s inventions were built by Alfred Vail, Morse’s assistant and collaborator. See Gale, Leonard D.; International Telegraph Union; telegraph; telegraph history; Vail, Alfred.

When spun rapidly, the images inside this cylinder can be viewed through the slits as an animated show of a juggler. In the above picture, the inside is shown for clarity, but normally the rotating device would be viewed straight on so that the image passing by the slits is seen. This was one of the early means for creating cell animations, that is animating images by the creation of individual frames that differ slightly from one another. [American Radio Museum collection.]

MOS See mean opinion score. Mosaic, NCSA Mosaic NCSA Mosaic is one of the most significant landmark applications in the history of the Internet as it spurred the evolution of pointand-click visual interface that nontechnical computer users, even children, could understand and quickly learn to use. The simplified Internet access and support of images provided by Mosaic and its

successors dramatically fueled the growth of the World Wide Web. The first version of x-mosaic was programmed at The National Center for Supercomputing Applications (NCSA) by Marc Andreessen in 1992 with Mosaic 1.0 released in November 1993. Mosaic was subsequently enhanced and ported to support the X WIndow System, Apple Macintosh, and Microsoft Windows platforms. In 1994, Andreessen and other NCSA personnel left to form Mosaic Communications Corporation based on the Mosaic concept. However, due to trademark ownership by the University of Illinois, the company and the software product were renamed Netscape Communications Corporation and Netscape Navigator, respectively, with the Board of Trustees of the University of Illinois retaining copyright ownership of NCSA Mosaic. The University of Illinois entered into an agreement for Spyglass, Inc. to negotiate commercial NCSA Mosaic licenses in 1994. Other commercial Web browsers were in development in the mid-1990s, including OmniWeb by Lighthouse Design, Ltd., which was released in March 1995. In spite of the commercialization of browsers, the Software Development Group at NCSA continued development on the Mosaic project until Mosaic 3.0 was released in January 1997. See Gopher, Internet Explorer, Netscape Navigator, OmniWeb. motion pictures Any images which convey the appearance of motion, whether in real time or by presentation of a fast sequential series of still pictures, especially videos, film reels, and animated computer images. Traditional motion film pictures consist of

a series of still images on a transparent medium played through a projector, usually from 20 to 30 frames per second, with 24 or 30 being common, as these are the speeds at which human perception merges successive still frames into a cohesive impression of connected motion. The development of motion picture photography owes some of its roots to a bet over a dispute as to whether a running horse lifted all four hoofs off the ground. Thomas Edison was one of the first to experiment with displaying a series of still frames in rapid succession in 1889. The first commercial motion picture, backed by the Canadian Pacific Railway, is attributed to Clifford Sutton in the early 1900s. See animation, celluloid, MPEG. Motorola A significant computer chip designer and manufacturer and electronic appliances manufacturer since the 1960s. It is descended from the Galvin Manufacturing Company from the early 1930s. In 1974 it released the MC6800, the first in a long family of chips still being developed a quarter of a century later. One of the first microcomputers developed with the Motorola family of microprocessors was the Altair 680, released late in the fall of 1975. Since that time whole families of computers have been based on the subsequent MC68000 family of chipsets, including Macintosh, Atari, Amiga, Sun, Apollo, SGI, NeXT, and others. Motorola is also well known for products in the mobile data communications industry. The Motorola CPU Sample chart shows a brief summary of some of Motorola’s best-known desktop computer microprocessors, prior to the collaboration with IBM to produce the PowerPC chips. In 1998, Motorola teamed up with the McCaw/Gates

Sampling of Evolution of Popular Motorola Central Processing Units (CPUs) Processor

Introd.

MC6800

1974

MC68000

1979

MC68010

Proc. Data Bus Addr. Bus Notes 8

16

Used in Altair 680.

32

16

23

16 32-bit registers. Supervisor and user mode. CISC architecture.

32

16

23

Virtual memory.

MC68020

1982

32

16/32

32

256-byte cache. Dynamic bus sizing.

MC68030

1987

32

16/32

32

Paged MMU on processor. 16-byte burst.

MC68040

1990

32

32

32

FPU, cached Harvard buses.

MC68060

1994

32

32

32

Superscalar pipelined. Power-saving.

The PowerPC family was created in collaboration with IBM and Apple Computer. This was a RISCbased line from the PPC 401 to 750 (G3), with speeds ranging from 20 to 500 MHz PowerPC

1994

64

64

32

From 50 to 135 MHz

MPC750 (G3)

1998

64

64

32

300 MHz

MPC7400 (G4) 1999

64

64

32

Double-precision FPU, AltiVec instruction set. External L2 cache interface. 350 to 450 MHz.

M

Teledesic project to provide Celestri technology to the orbiting satellite network. See Altair 680. See Sampling of Evolution of Popular Motorola CPUs chart. Mountain Bell The familiar name for the Mountain States Telephone and Telegraph Company. Mountain States Telephone and Telegraph Company An early telephone company, better known as Mountain Bell, which was formed in 1911 from the merger of the Tri-State and Colorado telephone companies, and the purchase of the Rocky Mountain telephone company. mouse A hardware human interface device that receives hand and finger movements and transmits them to a computing device. They are then interpreted into actions by the operating system and applications software. The mouse is named for its basic shape, which typically consists of a palm-sized, rounded or squarish object, with one or more buttons under the fingers and a “tail,” a cord that electrically connects the mouse with the computer. Mice come in various shapes and sizes: friction mice have a ball on the side that makes contact with a hard surface; optical mice require a grid or special pad. Laptop variations include finger pads and rollerballs, which are not strictly mice, but which employ the same basic movement and input concepts. The invention of the computer mouse is attributed to Doug Engelbart and is variously reported as having been invented around 1959 to 1963. By the late 1960s, Engelbart was testing a three-button mouse in conjunction with a keyset that was used in the other hand. During the early 1980s, when the Apple Lisa was being developed (the first of the Macintosh line), there were discussions at Apple as to whether to use a two- or three-button mouse. The testing and rationale supplied by Larry Tesler indicated a one-button mouse was completely appropriate, and the Macintosh line still works very well with this device 15 years later. The majority of competing desktop computers use two-button mice. mouse blur A visual artifact that makes the pointer look blurred as the mouse is moved too quickly for the refresh rate of the display device to keep up, which is more common on laptop systems that use LCD displays rather than cathode-ray tubes (CRTs). Mouse blur is often accompanied by mouse blanking, in which the fast movement of the cursor causes it to momentarily disappear, and reappear when the refresh catches up to its current position. MP See Multilink Protocol. MP3 A popular abbreviation for MPEG-1 Layer 3 or MPEG-2 Layer 3. See MPEG. MPEG Motion Pictures Experts Group. A series of international standards developed by a joint committee under the aegis of the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) to facilitate the development of digital video and audio formats and decoding schemes. Leonardo Chairiglione and Hiroshi Yasuda originated the MPEG development efforts in 1988. MPEG has received widespread acceptance for the playback of digital animations.

The development of media formats is somewhat dependent upon how the final compressed product will be used. In the case of MPEG series standards, consumer entertainment products (e.g., optical media) were taken into consideration, and thus the perceptual characteristics of the humans who would eventually be viewing or listening to the decoded MPEGs were factored into its development. Video and audio technologies typically require a lot of bandwidth and file space, so a large part of the MPEG effort has concentrated on decompression schemes and fast playback algorithms. The compression itself is left up to the discretion of individual vendors. MPEG is a family of standards numbered from 1 to 4, but the numbers do not necessarily indicate a progression. Some changes and development for specific needs occurred on the road from MPEG-1 to MPEG-4. What the different variants have in common is that they support the compression and playback of digital audio and video data: MPEG-1 is a relatively low-quality video standard initially developed for progressive video. Later adaptations also supported interlaced video but, in general, MPEG-1 has been superseded by other formats for applications that require higher quality video. MPEG-2 is a higher quality format than MPEG1 and supports both progressive and interlaced video and both two-channel and multichannel (surround) sound. It is a popular format that gained fast consumer acceptance and is suitable for a variety of digital videodisc (DVD), high definition television (HDTV), and other video applications. In consumer products, MPEG-2 sound compression technologies are not always used for the audio portion of an MPEG-2 disc; sometimes Dolby Digital is substituted (or included with the others). MPEG-2 supports a variety of bit-rates and picture resolution levels. Multiple audio and video streams can be multiplexed together for recording or transmission over a network. MPEG-3 was originally slated to support HDTV, but it was found that the MPEG-2 standards could be devised to support both DVD and HDTV and MPEG-3 was never developed. MP3 is sometimes mistaken for MPEG-3 but MP3 actually refers to either MPEG-1 or MPEG-2 Layer 3 formats. MPEG-4 was developed to support the world of data communications over networks which are frequently shared or limited in their transmission rates. Thus, it is optimized for the world of computer networks, uses different compression techniques than the other MPEG formats, and is more appropriate for applications such as videoconferencing, whiteboarding, and streaming video rather than for high-quality optical media-based consumer entertainment applications. MPEG is an asymmetric technology, based upon the use of MPEG encoders (to compress and store or transmit data) and MPEG decoders (to decompress and display data). It is asymmetric in the sense that

the speed and processing power required for encoding is not necessarily the same as that needed to decode the MPEG data stream. MPEG decoders are used to decompress and play back MPEG-based sound and videos either separately or together. The digital technology offers many appealing options for this process whether or not the MPEG video is combined with MPEG sound or with Dolby Digital sound. One of the reasons for the quick acceptance of digital videodiscs is their versatility. For example, on a DVD disc, there may be a video track, several sound tracks, and even data tracks for the display of textual commentary or subtitles. Thus, a favorite movie could be viewed several times, in its original form, in other languages, or in its original form with subtitles or other textual information. Many commercial entertainment DVDs include audio commentaries with the verbal thoughts and impressions of the directors and actors superimposed over the original movie (with the original soundtrack at a lower sound level in the background). This valueadded means of packaging entertainment titles is one of the forces behind the quick acceptance of MPEGbased commercial products. To be practical for the delivery of cinema-style education and entertainment programs, the playback display of MPEG data needs to be fast, so the tech-

nology is optimized with playback in mind. Individual contributors hold a number of patents to various technologies which have been incorporated into MPEG. These contributors agreed in writing to provide the technology nonexclusively at fair and reasonable royalty rates. There have been several enhancements to MPEG since its introduction as shown in the MPEG Versions chart. See animation, B-frame, I-frame, JPEG, MPEG decoder, MPEG encoder, P-frame. MPEG decoder A mechanism for “unraveling” the data on an MPEG-encoded medium to make it accessible for playback. MPEG decoders are built into DVD players, Web browser plugin applications, and a number of other consumer products. The decoder sometimes has to handle more than just the fast decompression and display of frames. Many MPEGencoded products come with several playback options, necessitating that the decoder be coupled with human interface algorithms to enable the user to select the MPEG options desired. On commercial DVDs, these algorithms are usually presented in much the same manner as application menus and buttons as are used on desktop computers. When the user selects an option, the information is used to configure and control the way in which the information is decoded for playback. See MPEG, MPEG encoder.

MPEG Versions Version

Notes

MPEG-1

Coding of Moving Pictures and Associated Audio for Digital Storage Media at up to about 1.5 Mbps. ISO/IEC 11172, standardized between 1993 and 1995. An optimized 1.5 Mbps bit stream for compressed video and audio, for compatibility with existing CD and DAT data rates. Non-interlaced color video is typically implemented at 352 x 240 (288 in Europe), which is relatively low resolution, as it derives from a CCIR-601 digital television standard. Replay speed is 30 frames per second (25 in Europe), fast enough for natural-looking motion. Sample precision is 8 bits.

MPEG-2

Generic Coding of Moving Pictures and Associated Audio ISO/IEC 13818, presented in draft form in 1993. ITU-T recommendation H.262. Similar in structure to MPEG-1, the documentation includes four parts in addition to the categories discussed in MPEG-1. MPEG-2 can address very low bit-rate applications with limited bandwidth needs, and support for surround sound multichannel applications. Video resolution is typically implemented at 720 to 550 x 480, somewhat similar to computer monitors, and a frame may be either interlaced or progressive formats.

MPEG-1+

MPEG-1 presented at MPEG-2 resolution. Frames are de-interlaced and compressed.

MPEG-3

Merged into MPEG-2 when it was decided that MPEG-2 syntax could be scaled to support HDTV applications. Often confused with MPEG-1/2 Layer 3 (MP3).

MPEG-4

Very Low Bitrate Audio-Visual Coding. Launched in 1992 to develop new algorithms for providing support for a wider range of applications, and to improve efficiency. New applications include low-bitrate speech coding and interactive mobile communications.

M

MPEG encoder A mechanism for creating MPEGformat compressed data styles for storage or transmission. While the format for MPEG compression has been standardized, the algorithms and hardware systems for creating MPEG-format data have been left up to the discretion of developers. Thus, MPEGformat files can be created in a number of ways on a variety of media and developers can create the MPEG files in a way that is appropriate for their application. MPEG decoders can even be incorporated into dedicated chips, for optimal portability or optimization for the task of encoding MPEG-format files. In general, MPEG encoding seeks to minimize file sizes without significantly compromising picture quality. This enables faster delivery of MPEG data over computer networks and makes it possible to fit more content on storage media. To accomplish these goals, a number of clever schemes for exploiting picture redundancy (where a frame is similar to a preceding frame) have been developed, such as differential encoding. Differential encoding is when you analyze a series of image frames and make some assessments about their similarities and differences and then use this information to remove redundancies (and thus reduce file size). Since video sequences commonly include many frames in a row with almost the same picture information (e.g., a kite fluttering against a blue sky), there are opportunities to save time and storage/transmission space by encoding only those portions of the image that change from one frame or field to the next. As with many optimization schemes, differential coding comprises a tradeoff. If a series of frames must be reconstructed “on the fly,” based upon a reference frame, with only the differences encoded, you cannot randomly jump to any frame in the sequence in the playback process and see the full picture without some fancy footwork and fast processing in the background. The other disadvantage to differential coding is that the playback algorithm must handle the reconstruction process and the error-checking accurately, or errors in decoding the reference frame, from which the others are derived, would be propagated through any frames that subsequently depend upon it. To help mitigate propagation errors that could occur from frame to frame in the playback of differentially encoded MPEGs, a scheme to insert the occasional full-frame picture has been developed. An intracoded picture (I-picture) is a complete image that is inserted every few frames to stop any reference image errors from continuing for a large number of frames. How often these frames should be inserted is a matter of balancing file size and potential error levels. Since differential encoding is intended to reduce file sizes, inserting I-pictures too frequently would negate this advantage. Sometimes images are constructed based upon the previous frames, but image processing can work the other way as well. A prediction-error picture (P-picture) is an image constructed from information taken from previous I- or P-pictures, while a bidirectionally encoded picture (B-picture) is one that uses later

images to construct a previous image. Confused? Think of it this way: imagine watching a video of a car driving past a house. Most of the image stays the same from one frame to the next since the house isn’t moving (assume a stationary camera photographing the scene). As the car moves past the house, however, some of the image changes. File space can be saved by encoding only the portions that change and constructing the successive frames from the information that is known rather than displaying every frame. Now here comes the tricky part. Suppose this scene opened with the car parked in front of the house before pulling out and driving by. There’s no way to construct the portion of the house obscured by the car from previous frames because the information isn’t there. With bidirectional predicted/interpolated encoding, the processor can look forward, to the frames of the house that show the portions that were obscured before the car drove off-camera, and insert that information into previous frames in the encoding process. Thus, differential encoding may be used to construct the scene based upon previous and later frames. Sound complicated? It can be, which is why MPEG is an asymmetric technology. Depending upon how it’s done, a significant amount of processing may be required to encode a movie to fit onto a DVD, for example, and the equipment to accomplish the task may cost hundreds of thousands of dollars, compared to a couple of hundred dollars for the playback deck. See MPEG, MPEG decoder. MP lambda switching MPlS (note MPLS in all uppercase is used as an abbreviation for multiprotocol label switching). multiprotocol lambda switching. See lambda switching. MPLS See Multiprotocol Label Switching. MPOA MultiProtocol Over ATM. A client/server protocol integration effort specified by a working group of the ATM Forum to provide direct connectivity across an ATM network between ATM hosts, legacy devices, and future network-layer protocols from different logical networks. This will enable the production of lower-latency, scalable ATM internetworks through a standardized virtual network with fewer router hops. See Anchorage Accord, LANE, IPv4, Next Hop Resolution Protocol. MPOA Client An ATM term. A device which implements the client side of one or more of the MPOA client/server protocols, (i.e., a SCP client or an RDP client). An MPOA Client is either an Edge Device Functional Group (EDFG) or a Host Behavior Functional Group (HBFG). MPOA over ATM sub-working group A group that seeks to solve some of the implementation problems associated with asynchronous transfer mode (ATM). It is integrating LAN Emulation (LANE), Next Hop Resolution Protocol (NHRP), Classical IP, multiprotocol encapsulation, and multicast address resolution in order to provide end-to-end internetworking ATM connectivity. MPOA is a packet-oriented protocol similar to LANE. The group provides courses, support, research, documents, and systems testing services.

MPOA Reference Model MultiProtocol Over ATM Reference Model. A specification approved by the ATM Forum in June 1997 for routing/switching over ATM networks. There are Internet MPOA resources (links, white papers, specifications, etc.) at the ATM Forum’s site. http://www.atmforum.com/atmforum/specs/approved.html MPOE Minimum Point of Entry. MPP See Multichannel Point-to-Point Protocol. MPT See Ministry of Posts and Telecommunications. MRI See magnetic resonance imaging. MRU maximum receive unit. MS Mobile Station. MS-CDEX A set of Microsoft DOS extensions for CD-ROM which allow MS-DOS to recognize the presence of a CD-ROM drive and access it accordingly. MS-DOS Microsoft disk operating system. MSDOS originated from a commercial text-oriented operating system developed from Tim Paterson’s QDOS, first released by Microsoft in 1981 to accompany IBM’s Intel-based microcomputer system. This was a somewhat different move for IBM, as the company had often created its products in-house. But IBM was under pressure to release a successful microcomputer in order to avoid being locked out of the growing market; Radio Shack at one point had almost 80% market share with its TRS-80 line. IBM’s move to look outside its own research and development resources provided a window of opportunity for emerging computer companies. They contracted to purchase an operating system from Microsoft and, in a remarkable turn of events, Microsoft managed to retain the rights to market the product

themselves, in competition with IBM, who called their version PC-DOS. Early versions of MS-DOS were intended for singleuser applications, but by version 3.1 network functionality was added. At about this time, multitasking graphical operating systems were being released by several other vendors, and there was pressure on MS-DOS to provide features found on other systems. MS-DOS became widespread through the 1980s, only slowly giving away to Microsoft’s later graphics-based Windows products, which were developed in the mid-1980s as front-ends to MS-DOS. MSDOS’s text interface is now used much less but, in syntax and functionality, it was very similar to CP/M, the dominant operating system at the time, developed by Gary Kildall of Digital Research (originally Inter-Galactic Research). MS-DOS became the pivotal product behind the financial success of Microsoft, and it and its successors have been installed on millions of computers worldwide. To give an introductory idea of the flavor of MSDOS, see the Examples of Some Commonly Used MS-DOS Commands chart. See MS-DOS history, operating system. MS-DOS history The Microsoft disk operating system (MS-DOS) was originally Tim Paterson’s QDOS. Paterson has reported that he gleaned ideas from a CP/M operating system manual published in the mid-1970s. CP/M was developed by Gary Kildall, a university professor and programmer, founder of Digital Research (originally Inter-Galactic Research). When IBM first approached Microsoft in the early 1980s to purchase the BASIC programming language for their personal computer, they apparently thought they were also obtaining the rights to CP/M. Bill Gates signed a nondisclosure

Examples of Some Commonly Used MS-DOS Commands Command

Function

CD or CHDIR COMP COPY DEL or ERASE DISKCOPY FORMAT MKDIR PATH

Change the current directory. Compare files or sets of files (PC-DOS). Copy files, duplicate. Delete/erase a file (use with caution). Copy from one floppy disk to another. Format a diskette. Make a new directory. Define the search path. This is where the system seeks executables and batch files so that the entire command path doesn’t have to be typed to run a command or application. Change the name of a file. Display the contents of a file (intended for ASCII files). Copy files and directories, optionally copy subdirectories. Clear the current screen.

REN or RENAME TYPE XCOPY CLS

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agreement to work with IBM, and promised to supply BASIC. When IBM found out they hadn’t purchased an operating system as well, Gates suggested they call Digital Research, developers of CP/M. Gates didn’t want to lose the languages contract for lack of an operating system, and Microsoft didn’t have an operating system that would meet IBM’s needs. Up until this time, Microsoft had concentrated on languages, Digital Research had concentrated on operating systems, and Kildall had not expected the “gentleman’s agreement” to change. IBM was in a hurry. They paid a call to Digital Research (DR) at a time when Gary Kildall had another commitment. His wife/business partner was present to talk to the corporate giant, but was uncomfortable with signing the one-sided nondisclosure agreement presented by IBM without consultation with Kildall, especially since DR’s attorney didn’t like the terms of the agreement. IBM went back to Gates and, seeing an opportunity, Gates offered to supply an operating system as well as BASIC. IBM accepted. Kildall was probably surprised at not having the opportunity to meet further with IBM to negotiate terms, as was customary at the time. Since Microsoft didn’t have an operating system that would fulfil the contractual agreement with IBM, they went to a company called Seattle Computer Products (one wonders why they didn’t first contact Kildall about licensing CP/M) and bought a simple operating system called QDOS (Quick and Dirty DOS) developed from CP/M by Tim Paterson. Microsoft contracted Tim Paterson to make a few enhancements in collaboration with Robert O’Rear, and soon after delivered the product to IBM. It was released first as PC-DOS by IBM, and later as MSDOS by Microsoft. There are some small differences between the two. This was the beginning of a long alliance and the launching of a tiny entrepreneurial effort into a major empire, with MS-DOS as the pivotal product. See Microsoft, MS-DOS, Digital Research. MSA See Metropolitan Service Area. MSAT Mobile Satellite. A commercial mobile satellite communications service developed jointly by AMSC in the United States and TMI in Canada. MSAU See Multistation Access Unit. MSB most significant bit. See least significant bit for explanation of MSB and LSB. MSC Mobile Switching Center. A switch providing coordination and services between mobile network users and external networks. MSK See minimal shift keying. MSN multiple subscriber number (e.g., as in ISDN Q.81 and Q.731 number identification services) MSNF See multisystem networking facility. MSP See Message Security Protocol. MSR magnetic-induced super resolution. MSS See multispectral scanner. MSU 1. microwave sounding unit. 2. See mobile subscriber unit. MTA 1. Macintosh Telephony Architecture. 2. See Major Trading Area. 3. Message Transfer Agent.

4. Metropolitan Trading Area. A Federal Communications Commission (FCC) designation for a region. This is an administrative process used to facilitate licensing for various communications services. MTBF See mean time between failures. MTI Moving Target Indication. In radar, the analysis of Doppler-shifted returning signals to select moving targets from various other nonsignificant or interfering objects (clutter). MTM Maintenance Trunk Monitor. MTS 1. member of technical staff. 2. Message Telecommunications Service. An AT&T designation for standard telephone service through direct dialing. 3. See Message Transfer System. MTSAT See Multifunctional Transport Satellite. MTSO See Mobile Telephone Switching Office. MTTR mean time to repair. A computed average of the amount of time it takes to bring a broken or faulty device back into service. MTU 1. See maintenance termination unit. 2. Maximum Transfer Unit. 3. multiple tenant unit. Mu-law A pulse code modulation (PCM) coding and companding standard. Mu-law is commonly used for encoding speech in 8-bit format by sampling the audio waveforms at 8000 times per second. A-law/Mulaw pulse code modulation (PCM) is the most widely used scheme for encoding telephone conversations. A-law PCM is primarily used in European systems, while Mu-law PCM is primarily used in North American and Japanese systems. See A-law, E carrier, pulse code modulation, quantization, U-law. MUD Multi-User Dungeon/Dimension. An addictive role-playing game prevalent on the Internet and most college campuses since MUDs were invented in the late 1970s. In fact, it was one of the few games that college network administrators tolerated on their systems, because the development and administration of a MUD involved the exercise of quite a few gray cells, and involved more programming and technical expertise than the usual shoot-em-up games that distracted students from their studies. MUDs involve fantasy characters, developed by the players, which interact in various rooms within the MUD. The first MUD has been attributed to R. Bartle and R. Trubshaw at the University of Essex. mud ring A mounting bracket, for mounting a faceplate in a wall, for example. These can be used instead of receptacle boxes for terminating low-voltage cables. Mud rings should be mounted in dry areas away from alternating current (AC) wiring and should be positioned so that the faceplate mounted on top of the mud ring is straight. MUF See maximum usable frequency. Mu-law encoding, µlaw encoding A companding technique used to compress audio signals. This is useful for speeding up data transmission and reducing storage space. Mu-law coding can improve the signal-to-noise (S/N) ratio without increasing the amount of data and thus is suitable for use in telecommunications applications. Mu-law is logarithmic in nature; it carries more information about the lowamplitude samples than high-amplitude ones and is

based on known statistical characteristics of audio signals. Segments of digitized audio, called samples, are reduced to about half their original size. Zero code suppression is used. Mu-law encoding compresses at almost the same ratio as A-law encoding. Mu-law is primarily used in North America and Japan, while A-law tends to be used outside North America and Japan. Telephony codecs commonly used Mu-law samples. See A-law encoding, U-law encoding. Multi-Agent Systems Laboratory MAS Lab. A lab at the University of Massachusetts at Amherst involved in the research, analysis, and development of sophisticated artificial intelligence (AI) problemsolving and control architectures for single- and multiple-agent systems. The lab has developed realtime AI and control systems and techniques for the coordination of multiple agents. Multi-Service, Multi-Carrier, Distributed Communications MMDC. Pioneering commercial technology from Tekmar Sistemi for radio communications over fiber applications. This is particularly applicable to in-building, short-range radio applications and is currently being used in the design and manufacture of a MMDC system for the Singapore Mass Rapid Transportation system for installation in trains, elevators, platforms, and stairways. The MMDC system will provide a platform for common commercial services, including FM/DAB Radio Rebroadcast, TV Rebroadcast, paging, and various digital communications services (AMPS/DAMPS, GSM, PCS, 3G,. etc.) Multi-Vendor Integration Protocol MVIP. MVIP originated in 1989 from an initial consortium of three companies: Natural MicroSystems, Inc., Mitel, and GammaLink; four more helped the project to coalesce a year later. MVIP has since become one of the two common software/hardware bus standards in computer telephony (along with SCbus). The purpose of the standardization was to bring together the various telephone and computer technologies so they

could readily interconnect and intercommunicate. MVIP provides an open, nonproprietary, uniform, yet flexible way of providing telephony components with computer equipment through open software development environments. In other words, phone-related technologies can be accessed and controlled through a desktop computer. The MVIP standard includes the capability to reconfigure “on the fly” to handle various call functions. The original single-chassis standard designed for a synchronous environment was MVIP-90 and additional versions followed, including H-MVIP (high capacity MVIP), and MC-MVIP (multi-chassis MVIP). The Outline of MVIP Versions chart shows three MVIP formats. MVIP supports Unix, OS/2, and Microsoft DOS or Windows. The work was officially taken over in 1994 by the GO-MVIP project. See Go-MVIP. http://www.mvip.org MultiAudio A specification released by the Optical Storage Technology Association (OSTA) in July 2001. MultiAudio specifies a Table of Contents mechanism for retrieving, managing, and playing back audio files on popular optical formats such as CD or DVD media. Thus, direct reading of the Table of Contents, rather than lengthy disc initialization, is facilitated. It also facilitates the development of playlists and lists of various attributes of the files, such as genre, artists, album titles, etc. The MultiAudio format is an extension of MP3 capability on consumer electronics devices and is backwardly compatible with current MP3 disc players. A standard scheme for storing the track name, year recorded, performer name, composer name, songwriter name, arranger name, album name, and genre is defined. Hopefully, future versions also include conductor and soloist (especially for classical music where guest conductors and soloists are common). The OSTA MultiAudio logo can be used through a royalty-free license by manufacturers demonstrating compliance with the specification through

Outline of MVIP Versions Format

Notes

MVIP-90

Original single-chassis specification consisting of a multiplexed digital telephony bus with 512 x 64 Kbps capacity, distributed circuit-switching capability, and digital clocks architecture. MVIP-90 provides for 16 serial lines.

H-MVIP

High Density MVIP. A scalable, high-capacity, downwardly compatible superset of MVIP-90 adopted as a standard by the GO-MVIP technical committee in 1995. H-MVIP provides for 24 serial lines.

MC-MVIP

Multi-Chassis MVIP. A high-capacity version which provides several alternate physical layer connections with a common set of software interfaces for interconnecting single-chassis MVIP systems and telephony systems. MC-MVIP provides 1536 x 64 Kbps over copper twisted pair (MC1), FDDI-II for 1536 x 64 Kbps over copper or fiber (MC2), or SONET/SDH at 155 Mbps for 4800 x 64 Kbps over fiber.

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the self-certification requirements. The test disc is available through a onetime fee from OSTA. The logo will alert consumers to products featuring the enhanced playlist features. See MultiPlay, Optical Storage Technology Association. multicarrier modulation MCM. A number of modulation techniques for multiplexed transmission of data by dividing the communications channel into smaller units and evaluating the units individually in terms of speed and suitability for transmission. MCM is used to implement Digital Subscriber Line (DSL) services over existing twisted-pair copper wires, which can vary widely in their characteristics. MCM optimizes bandwidth usage for multiple media transmissions and reduces interference from impulsive and narrowband noise. See carrierless amplitude and phase modulation, orthogonal frequency division multiplex, discrete multitone, discrete wavelet multitone. multicast An organizational arrangement and physical/data capability in which programming or data are distributed to more than one recipient from one or more sources. Broadcast television, in which one local TV station might broadcast to 50,000 local residents, is an example of a wireless, analog form of multicast communication. There are a number of ways in which a multicast system can be configured. The one-to-many relationship may be a simple one, with one endstation transmitting to all the other stations receiving data, or it may be selective, in that static or dynamic groups are configured to receive the multicast transmissions. An example would be cable TV services. A single cable TV distributor may have 10,000 customers with premium services, 40,000 customers with basic services, and 20,000 customers with a combination of basic and premium selected services. Thus, multicast management groups are defined for who gets which cable stations. In a dynamic computing network, multicasting is more subtle and complex, with the added capabilities that certain applications or users can be defined to receive certain services at specific times of the day through certain authorized privileges. A multicast group manager (MGM) is an application for handling the information needed to organize and administer the many and varied aspects of multicast network groups. More specifically, in the context of digital internetworking, multicast is a type of Internet Protocol (IP) address identifier for a set of interfaces. Frames sent from one endstation are received by one or more endstations as opposed to a singlecast or unicast topology in which frames sent from one endstation are received by only one station. In IPv6 multicast addresses supersede broadcast addresses. In ATM networking, the form of the multicast command is atm multicast Xpress Transport Protocol is an example of a multicast protocol coexisting with other protocols (e.g., security mechanisms) that enables a number of different configurations of multicast groups. See anycast, unicast, IPv6 addressing, multicast backbone.

multicast backbone Mbone. Technology that extends the Internet Protocol (IP) to support multicasting, developed by Steve Deering at Xerox PARC. The Mbone was adopted by the Internet Engineering Task Force (IETF) in 1992. Mbone supports two-way transmissions of data between multiple network sites. Thus, with Mbone, a single packet can have multiple destinations and pass through a number of routers before being split up to run through different paths. The packets reach their destinations at about the same time. This leads to greater support for multimedia capabilities over the Internet. Mbone systems are assigned Class D Internet Protocol addresses. Multichannel Interface Processor MIP. A Cisco Systems interface router processor which provides up to two channelized T1 or E1 serial cable connections to a channel service unit (CSU). Multichannel Point-to-Point Protocol MPP. A protocol from Ascend Communications similar to Pointto-Point protocol (PPP), but which supports multiple network channels in inverse multiplexed systems. multichannel video programming distribution See MVPD. multifeed dish, multifocus dish A type of parabolic satellite receiving dish which can be positioned to capture signals from more than one satellite at a time, with the signals reflected to a series of feedhorns. Multifunctional Transport Satellite MTSAT. A Japanese system of satellites with updated transmission capabilities evolving out of the Geostations Meteorological Satellite (GMS) system. The Japan Meteorological Agency administers the operational plans for the satellite system, which will begin with MTSAT-1R and MTSAT-2. The system will make hourly observations for the northern hemisphere and observations each six hours for cloud-motion winds in the northern and southern hemispheres. Newer sensing and transmission technologies are being introduced into the MTSAT series. In addition to previous capabilities of the GMS systems, MTSAT will quickly relay high-resolution digital images and will include a new infrared channel (IR4) for detecting low-level night clouds. The upgraded transfer capabilities necessitate the installation of new equipment and software. It is expected that the MTSAT systems will come online around 2003, superseding the still operational GMS-5. MTSAT data will be used by more than two dozen countries and by domestic Japanese services such as the Japan Weather Association (JWA). multihop routing A ubiquitous approach to wired or wireless data transmissions that involves one or more relays or intermediate routing devices (nodes) in the transmission path between the sending and receiving devices. Multihop routing is commonly used to increase the transmissions range or to increase the flexibility of a system so that messages can be transmitted flexibly or to multiple destinations individually or simultaneously. The phrases ad hoc or on demand are often used in connection with multihop routing to indicate routing that is dynamically assigned to accommodate the routing needs at hand.

Multihop routing is characteristic of distributed computer and relay radio networks. The intermediate device may dynamically assign the next hop or be involved in amplification of the signal, as in wireless communications. In analog networks or digital networks with analog relays, generally a price must be paid for the extra hops in terms of attenuation and sources of interference. In optical networks, the trend has been from electromechanical connectors and relays to all-optical relays to reduce attenuation in the various hops. The length of a hop is related to the type of technology used. Hops in physical wireline networks may range from a few inches to a few feet, or with suitable cables, a few hundred feet. Hops in wireless networks are related to the power of the sending and receiving equipment (and associated regulations) and may range from a few feet to many hundreds of yards. High-frequency wireless propagation over distances of 2000 miles or more is usually accomplished by bouncing the signals multiple times between the Earth’s ionosphere and the ground or a body of water. Another strategy is to aim the signal into the F region (a region above the Earth that is active in daytime) and bounce the signal within the region such that it doesn’t bounce up and down to the Earth, thus preserving some of the strength of the signal. Depending upon the size or type of network, multihop routing architectures can be designed and configured in a number of ways. Distance-vector, hierarchical, and dynamic source routing are just a few examples. Single-hop topologies are sometimes combined with multihop topologies in a two-level architecture to take advantage of the relative stability of a single-hop signal and the flexibility and distance advantages of multihop transmissions. Some of the important issues related to the design and configuration of multihop networks include optimization, signal strength, and Quality of Service (QoS). See backscatter, ionospheric; M hop; Multihop project; propagation. Multihop project A wireless network dynamic configuration project supported by the German Federal Ministry of Education, Science, Research, and Technology, initiated in May 2000. The project encompasses the development of wireless, channel-oriented, ad hoc multihop broadband transmissions with decentralized topologies as well as interoperability and WLAN issues. multilevel coding A coding scheme or system, usually bandwidth-efficient encoding, for carrying more data through a channel in a specified period of time. There are many approaches to improving the efficiency of transmissions. Multilink Protocol MP. Multilink is an Internet standards-track protocol which enables the splitting, recombining, and sequencing of datagrams across multiple logical data links. Originally designed as a software solution for implementing multiple simultaneous channels over ISDN, the concepts are generalizable to multiple PPP links between two systems. The purpose of multilink implementation is

to coordinate multiple independent links (i.e., to aggregate a bundle) between a fixed pair of systems to create a virtual link with greater bandwidth than individual parts used alone. See RFC 1990. Multilink Protocol Plus MP+. An extension to the PPP Multilink Protocol (MP) for managing multiple data links bundled by Multilink Protocol. MP+ adds an inband control channel and remote device management features to MP. Thus, an unconfigured system with the capability to answer incoming calls can be accessed and managed remotely prior to entering various protocol configuration parameters. See Multilink Protocol, RFC 1934. multimedia A catchall term for sensory-rich communications media, that is, media that contain images, motion, sound, tactile feedback, etc. Multimedia educational and entertainment products are more common than multimedia business applications. Networks need greater bandwidth and faster processing speeds to handle multimedia traffic. See animation, frame buffer, Mbone, virtual reality. multimedia mail Electronic mail (email) that incorporates media capabilities such as audio and visual components whether through MIME or proprietary methods. These types of capabilities were pioneered in the 1970s and 1980s on research computers, implemented on a number of workstations in the early 1990s (NeXT, Sun, etc.), and began to appear on common consumer desktop systems in the late 1990s. Email is created and viewed as HTML with graphics and embedded links is one example of the gradual integration of multimedia capabilities into day-to-day mail exchanges. The inclusion of multimedia files along with text-based mail messages is also becoming common, with .jpg, .tiff, and .pdf file formats commonly used for lossy, lossless, and PostScript file types, respectively. MultiPlay A compatibility specification originally proposed by Oak Technology, Inc. in December 2000 and adopted and promoted by the Optical Storage Technology Association (OSTA). The MultiPlay specification was announced in December 2000, aimed at ensuring Compact Disc Recordable (CDR) and Compact Disc ReWritable (CD-RW) disc compatibility in consumer CD and DVD players, along with personal computer CD and DVD players. The specification includes Red Book Audio, CDText, and VideoCD as the initial formats. The requirements for a consumer CD/DVD player to be considered MultiPlay-compatible include • CD-Audio only players must play CD-Audio from CD-R and CD-RW discs, • CD-Audio and CD-Text players must play CD-Audio and CD-Text from CD-R and CD-RW discs, • DVD players capable only of CD-Audio (besides DVD Movie) must play CD-Audio from CD-R and CD-RW discs, and • DVD players capable of CD-Audio and VideoCD must play CD-Audio and VideoCD from CD-R and CD-RW discs. The MultiPlay logo can be licensed to manufactur-

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ers distributing compatible devices on a royalty-free basis. Compatibility is demonstrated through a selfcertification process using test discs provided by OSTA on a onetime fee basis. See MultiAudio, Optical Storage Technology Association. Multi-Media and Digital Communications lab MDCC lab. Located at Northern Oklahoma College, the MDCC lab is the largest Media 100 Inc. Finish/ Intergraph installation in the world. Through Fibre Channel storage, video recording equipment, and multiple Intergraph stations, students can study and create multimedia productions. Multimedia Cable Network System MCNS. A North American cable data communications industry specification developed by the Multimedia Cable Network System Holdings partners. The specification is known as Data Over Cable Service Interface Specification (DOCSIS), MCSN, or MCSN/ DOCSIS. In 1997, VLSI Technology, Inc., announced a data security chip to support MCNS cable modem specifications. In 1998, Cisco Systems, Inc. announced integrated router/cable modem termination equipment to support the MCNS. With this type of support for the specification, cable modem vendors began announcing cable modem devices. The system and associated services were especially attractive to residential and small business subscribers, and MCNS became the de facto standard. Some vendors continued to support proprietary schemes in addition to MCNS, such as 3Com, distributors of ATM-compatible modems, in the hope that niche markets would continue to be viable. There were some objections to the development of DOCSIS, as it was felt it could not be deployed in Europe in support of a global standard. Nevertheless, some European vendors began selling MCNS/ DOCSIS-compatible modems. In the development phases, the MCNS approach was quite different from the other primary cable modem format, IEEE 802.14, in terms of how the medium access control (MAC) protocol was integrated. While both formats traded off upstream speeds in favor of downstream, MCNS was more efficient in the downstream direction, while 802.14 broadband protocol was more efficient in the upstream direction. See Data Over Cable Service Interface Specification, Multimedia Cable Network System Holdings. Multimedia Cable Network System Holdings MCNS Holdings. A North American cable industry group comprising Comcast Cable Communications, Cox Communications, Tele-Communications, Inc. (TCI), and Time Warner Cable. MCNS developed the MCNS Removable/Renewable Security System, in 1995, for securing voice and data communications and protecting from theft-of-service and denial-ofservice attacks. It further developed the Data Over Cable Service Interface Specification (DOCSIS) in 1996. MCNS specifications have been widely adopted by cable modem manufacturers. See Data Over Cable Service Interface Specification, Multimedia Cable Network System. MultiMediaCard MMC. A compact, removable,

low-power-consumption, solid-state media card for storing and retrieving digital information that can be used with small, lower-power devices such as mobile communications and music appliances. MMC began as a joint project between SanDisk Corporation and Siemens AG/Infineon Technologies AG. It was first introduced in November 1997. Support for the concept has come from a variety of semiconductor suppliers, software vendors, and manufacturers of portable navigation, communication, and entertainment products. MMCs are about the size of a postage stamp (32 x 24 x 1/4 mm), weighing less than 2 g. The connection is through a seven-pad serial interface. Readonly memory (ROM) is used for read operations and Flash technology is used for read/write applications. A single card can store, in its current form, up to about 64 Mbytes of data, a capacity similar to that of a hard drive of the early 1990s, but in a tiny, portable format. This is sufficient to contain the textual contents of about 100 books or the contents of a standard music CD. MMCs have potential not only for existing portable devices, but also for new hybrid devices such as cell phone/Internet appliances. MultiMediaCard Association MMCA. A trade association founded in 1998 to support and promote the MultiMediaCard (MMC) standard and its global adoption. The MMCA develops and regulates open industry standards related to the MultiMediaCard technology. See MultiMediaCard. http://www.mmca.org/ Multimedia Communications Forum MMCF. A nonprofit international multimedia communications and software research and development organization founded in 1993. MMCF consists of telecommunications service providers, multimedia application and equipment developers, and multimedia users. MMCF promotes market acceptance of networking multimedia products and serves as a clearinghouse for multimedia-related specifications, standards, and recommendations. http://www.mmcf.org/ Multimedia Communication Exchange MMCX. A commercial phone/data server software developed by AT&T’s Global Business Communications Systems (GBCS) for providing multimedia services for private phone branch exchanges. See Global Business Communications Systems. Multimedia Communications Research Laboratory MCRL. A division of Bell Labs doing fundamental research in speech production and hearing, speech recognition, coding of audio, speech, and images, and echo cancellation. MCRL provides Lucent Technologies with innovative competitive products such as the electret microphone, capture and storage technologies, and media translation tools. multimedia desktop collaboration MMDC. A software application enabling end users to significantly enhance desktop productivity through the utilization of multimedia communications technologies such as whiteboarding, realtime document collaboration, etc. Multimedia Development Center MMDC. A center of the University of Nebraska associated with the Office of Information Technology Services.

MultiMedia Development Center MMDC. A service of Johns Hopkins University providing multimedia development tools (scanners, audio/visual tools, CD burning, etc.) and an introduction to advanced multimedia to staff and students of the Homewood Schools of Arts and Sciences and Engineering, by appointment. multimedia information retrieval MIR. The access and retrieval or receipt of a transmission of multimedia data. MIR is commonly associated with databases on and off the Internet and is also now commonly carried out through email and certain videoconferencing products. Multimedia Learning Lab MLL. Originally called the Multimedia and Visualization Laboratory (MVL), the facility was rededicated in January 2001 as the Multimedia Learning Lab. This is a teaching lab at the University of Arizona that enables the study and creation of multimedia audio/visual technologies, including digitization, animation, audio recording, etc. Multimedia Mail Service MMMS. A means to transmit media types not explicitly specified in the X.400 standard through the use of Externally Defined Bodyparts. It adds the concept of a global store for high-volume data to the Message Transfer System (MTS). Research, development, and manufacturing entities within Berlin, Munich, and other German centers collaborated in the development of the Multimedia Collaboration Services. Multimedia Mail Security MMMSec. A German research project of the Open Distributed Multimedia Applications Group at the GMD Institute for Open Communication, funded by DeTeBerkom, Ltd. The goal of MMMSec is primarily to develop a security platform to support multimedia messaging and its integration within a multimessaging-system-enabled multimedia-mail user agent, in a user friendly manner. An X.420-Security-Bodypart was developed within the project to provide integrity, confidentiality, and digital signatures through encapsulation. See Multimedia Mail Service. Multimedia Message Entity MME. In the context of a nonrealtime Multimedia Messaging Service (MMS), entities that may be located in a fixed network or Message Service between which different types of information may be transferred. Multimedia Messaging Service MMS. A nonrealtime service in development by technical working groups for transferring different types of information between two Multimedia Message Entities (MME) in a store-and-forward fashion. MMS enables the development of unified applications for integrating the composition, delivery, and access of a variety of types of media communications (text, image, voice, etc.). See Multimedia Message Entity. MultiMedia Telecommunications Association MMTA. A professional telephony/computer integration trade association descended from the North American Telephone Association. The MMTA is organized as an open public policy, market development, member support, and educational forum for

telecommunications product and service developers and resellers. http://www.mmta.org/ Multimedia Virtual Laboratory MVL. The MVL is a research and development center of the Telecommunications Advancement Organization of Japan (TAO). This is a virtual facility with distant laboratories interconnected by high bandwidth networks to exchange communications and share high-cost equipment resources. Multimedia Visualization Laboratory MVL. See Multimedia Learning Lab. multimeter, multirange meter A measuring instrument commonly used in the communications industry which has several scales for evaluating an electrical circuit, including voltage, resistance, and current. multimodel data compression MMDC. A meta data software compression algorithm for managing the creation, invocation, and destruction of other software algorithms. MMDC is suitable for handling interleaved data streams of different types. It was developed by Ross N. Williams, implemented in Ada on a VAX/VMS system. multimode optical fiber MMF. A multimode fiber optic transmissions cable, usually with a relatively thick core, acting as a waveguide to reflect and propagate light at many angles. A thicker core has advantages and disadvantages. More light signals can be sent at one time, but the signal transmission distance is shorter than single mode fiber, due to the interaction of the reflected signals within the core and gradual fading over distance. Thus, it is limited to about 2 km. Signals are usually transmitted through multimode cables with light-emitting diodes (LEDs) and received at the other end with a photodiode detector. This detector translates the signals back into electrical impulses. See single mode optical fiber. Multiparty Multimedia Session Control MMUSIC. An architectural framework to support Internet teleconferencing. To date the MMUSIC Working Group has defined a number of IETF Draft documents to support this capability under the original umbrella of the Internet Multimedia Conferencing Architecture, including the Simple Conference Control Protocol, the Session Description Protocol, media alignment and messaging support, and others. See Mbus, RFC 2326, RFC 2327, RFC 2543, RFC 2974. Multiparty Multimedia Session Control Working Group MMUSIC Working Group. An IETF Working Group chartered with the development of standards-track protocols to support Internet teleconferencing. MMUSIC’s focus is on supporting the loosely controlled conferences common on the MBone. To support these functions, the MMUSIC Working Group has described the architectural framework for MMUSIC and interoperability scenarios and drafted protocols for various aspects of session initiation, control, and security. multipath fading A signal loss characteristic of mobile communications in areas where buildings or uneven terrain bounce the transmission waves in

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many directions such that several “copies” reach the receiving station. The deflected signals may interfere with, or even partly cancel out, the primary signal. When a subscriber listens to an analog cell phone conversation or a motorist listens to an AM car radio, the sound volume may decrease. Digital transmission systems provide error-correction techniques to combat the problems of fade, and spreading the spectrum over a broader bandwidth, if feasible, can sometimes help. multiplayer gaming Many computer games are designed for one player to sit and play against the computer. Some of these games have a mode in which the user can elect to play against an opponent, usually on the same system, with the two players alternately using the input devices, or using two sets of joysticks, for example. These are usually known as single- or dual-player games. Multiplayer gaming is implemented in a number of ways. There are games in which multiple players can play on the same machine in much the same way as dual-player games, each one taking a turn, but multiplayer more often connotes a game in which multiple players can interact at the same time with the computer, with each other, or both. This opens up a whole new dimension in gaming, and multiplayer games are very popular due to the human element, and the higher sophistication that they often provide. Most multiplayer games can now be played over networks and, in fact, a large proportion of sales of inexpensive Ethernet cards for home and small business computers has resulted from the popularity of fast-action multiplayer computer games. See MUD. multiple access A means to increase communications capacity over a limited bandwidth medium. There are many ways to do this; some are specific to the type of technology, and whether it is analog or digital. In computer networks, multitasking and common address schemes and protocols allow multiuser access. Web pages on the Internet are a good example of multiple access technologies, since many thousands of people may be accessing the same site at virtually the same time. In cellular communications and transponders, there are at least three types of basic schemes that allow multiuser access to limited resources. See the Radio Frequency Transmission Schemes chart for some examples. Multiple Address System MAS. In wireless communications, a designation for low-capacity not-forprofit, not-for-hire internal business networks with at least four remote stations. In 1992, more than 50,000 applications were made to the Federal Communications Commission (FCC) for MAS facilities; these were to be resolved through a lottery system. In winter 1998, the FCC dismissed the MAS facilities in the 932- to 932.5- and 941- to 941.5-MHz frequency bands and refunded the filing fees. MAS Spectrum Auction No. 42 was scheduled to begin in November 2001. This auction was for 5104 licenses to cover 176 Economic Areas from paired frequencies in the approximately 928.85625to 959.85625-MHz range. These licenses cover terrestrial point-to-multipoint and point-to-point fixed

and mobile transmission excluding video entertainment material. multiple customer group access For many expensive technologies, there are options for different institutions or departments with lower access needs to share the technology. In Frame Relay systems, several groups can share the network through a Frame Relay cloud. In telephony, several firms with individual trunks may send and receive through a shared private branch system. For Internet service access, a group of users might share a limited pool of dynamically assigned Internet Protocol (IP) numbers or a small pool of fast modems, on a first-come, firstserve basis. Multiple Exchange Carrier Access Billing MECAB. A document prepared under the auspices of the Carrier Liaison Committee of the Alliance for Telecommunications Industry Solutions (ATIS), which establishes the methods for processing orders for access service provided by two or more local carriers, that is, a local exchange carrier (LEC) and a competitive local carrier (CLC). multiple frequency shift keying MFSK. Frequency shift keying is a modulation technique used in data transmissions such as wireless communications in which binary “1” and binary “0” (zero) are coded on separate frequencies. This scheme can also be adapted to regular phone lines by assigning binary “1” to a tone and binary “0” (zero) to a different tone. In multiple frequency shift keying, greater use is made of different frequencies to represent information. These multiple frequencies may be transmitted one after the other, or simultaneously. See frequency modulation, frequency shift keying, phase shift keying. multiple homing 1. In networking, taking an additional service line, which is often a leased line through a larger provider. This is sometimes done by Internet Service Providers (ISPs) as their customer bases increase. Thus, it becomes necessary to maintain and announce an additional set of routes through which addresses can be reached. 2. In telephony, adding phone connections so calls can be routed through more than one switching center to provide redundancy in case of problems with the initial service loop. Multiple-Image Portable Graphics MNG. A format for using multiple subimages in a single frame, a multimedia graphics format originally developed as Portable Network Graphics (PNG) for animations. PNF was submitted as Draft 1 by Glenn RandersPehrson in June 1996. With Draft 12, in August 1996, PNF came to be known as MNG and, by December 1997, it was up to Draft 42 and considered essentially finished. See Portable Network Frame, Portable Network Graphics. Multiple Module Data Computer MMDC. A Marine Product Group commercial instrument system computer that intercommunicates through a Controller Area Network (CAN). The CAN message center enables mariners to observe and control functions related to the operation and optimal performance of a boat. This is essentially a “smart boat” concept.

Multiple Station Message Waiting In telephony, a means of indicating on more than one telephone station that a message (e.g., voice mail) is stored and waiting to be accessed. This is usually indicated with a blinking light or brief text message. multiple switchboard A manual switchboard with multiple operators in which answering jacks are divided up among operators, usually in rectangularly organized banks. Multiple Virtual Line MVL. A communications system that uses existing analog phone lines to provide higher speed digital communications and simultaneous voice. A mid-range option between cable modems and ISDN modems. An MVL switch must be installed at the switching center and the subscriber point. multiplex See multiplexing. multiplexed analog component MAC. A means of television transmission used with direct broadcast satellite (DBS) programming. The various signal components – audio, luminance (brightness), and chrominance (color) – were transmitted independently. The advantage of this, particularly for DBS in European regions, is that the audio can be individually tailored to the language desired. multiplexing Splitting the use of a circuit in one of a variety of ways so more than one signal can be carried at a time over a single transmission. This is an extremely important way of increasing channel efficiency and capacity in most telecommunications technologies. Multiplexed phone circuitry began to appear in the late 1930s, and was widely established by the mid1950s. A historically significant practical application of multiplexing was developed in 1953 by E. H. Armstrong and John Bose, in which they enabled a single FM station to simultaneously transmit more than one signal at a time. This made possible multiple simultaneous broadcasts, including the transmission of stereo broadcasts. Many different multiplexing schemes are included under individual headings in this dictionary. multiprocessing Using intercommunicating processors to solve computing tasks. The various processors may be housed inside one computer, or may be in separate systems, connected by a network. Multiprocessing is associated with parallel processors with distributed computer systems and often with highend computing tasks such as scientific calculations, rendering, ray tracing, and computer animation. In a multiprocessing system, a centralized processor often assigns and distributes tasks, with the other processors feeding back information to the system or following instructions from this central administrator. The software development to optimize these kinds of systems still has room for development, and there are many opportunities to contribute to research and implementations in this area. Not all tasks benefit from multiprocessing. In other words, it doesn’t make everything faster. If the overhead involved in managing and coordinating the different processing tasks is greater than the speedup

in the tasks themselves, then it’s not a good candidate for multiprocessing. One of the most exciting aspects of multiprocessing is that the speed of communication between the processors is an intrinsic part of the system. With higher and higher data rates, faster CPUs, and faster data buses, we may someday realize a time when the speed of the data transfer meets or exceeds the speed of its associated processors, in which case the various networked systems will function more like a single organism than a set of separate computers. Multiprotocol Label Switching MPLS. A connection-oriented routing system for switching network frames or packets. Network control and data transfer are handled separately and MPLS can support multiple network layer protocols. It is typically used in backbone networks. The IETF developed the scheme out of a number of switching technologies, most of them Internet Protocol-based, beginning in 1996. MPLS was intended to support scalable, efficient, high-speed forwarding, routing-controllable networks. Since MPLS is a label-switching technology, the labels are important and are dependent upon the link layer used. MPLS transmission paths may be explicitly defined or controlled through information contained in the label. MPLS differs from conventional Internet Protocol (IP) forwarding in that the assignment of a particular packet to a particular stream is done only once, as the packet enters the network. This facilitates the use of explicit routing, without each packet carrying the explicit route. The assigned stream is encoded with a short fixed-length label that follows it to the next hop. Thus, at subsequent hops, rather than analyzing the packet each time to gather information from the network layer header, the label is used as an index to a table specifying the next hop, and a new label supplants the old label. MPLS is particularly suited to implementation with Asynchronous Transfer Mode (ATM) and is of interest to IP-over-ATM. It has also been suggested for use with Frame Relay networks. MPLS provides explicit class of service (CoS) information, or information for inferring the CoS or precedence from the label. Routers that support MPLS are called label switched (or switching) routers (LSRs). Concurrent with the development of MPLS was an Optical Label Switching (OLS) system proposed by Yoo in 1997. It shares a number of similarities with MPLS and also has some advantages. See Forwarding Equivalence Class, label switching, Optical Label Switching. Multiprotocol Label Switching domain MPLS domain. A contiguous set of nodes that provide MPLS routing and forwarding operations. Multiprotocol Label Switching edge node MPLS edge node. An MPLS node that connects an MPLS domain with a node outside the domain. Multiprotocol over ATM MPOA. A multiprotocol virtual routing scheme for Asynchronous Transfer Mode (ATM) finalized by the ATM Forum in July 1997. Through bridging, devices in an Internet Protocol (IP) subnet can be interfaced with different

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physical ports on various MPOA edge devices while still appearing to be associated through the bridging. To legacy systems, the MPOA system appears as a traditional router. Multipurpose Internet Mail Extension MIME. Since any type of binary file can be transported over the Internet using appropriate conversion routines, protocols, and compression algorithms, if needed, it is logical that text, graphics, and sound can all be transmitted through binary files. Yet, Internet Mail had provisions for only the transmission of ASCII documents. For this reason, developers sought to give email a richer set of capabilities, and released MIME specifications in 1992 as a general framework and format for the representation of many kinds of data types in Internet mail. MIME enables a developer to write email software clients which can include pictures of the kids, sounds of the dog barking, and messages to loved ones all in the same message. This provides the user with a multimedia mail interface to the Internet. Since email accounts for at least 75% of the communications of regular consumers on the Net, enhanced email capabilities will probably be appreciated by many. Content-rich email has been around on several workstation platforms since the late 1980s, but most of these applications were proprietary and could not intercommunicate. Text mail messages for the Internet were defined even earlier, in 1982 (RFC 833). Then, in 1992, a standards track protocol for a generalized Internet extensions format was submitted as a MIME Request for Comments (RFC) from the IETF Network Working Group. MIME provides ways in which to include multiple objects in a single message, and to represent text in character sets other than just U.S.-ASCII. It supports multiple typefaces, images, and audio. While many email programs are MIME-compliant, not all of them support all the features of MIME, but it is expected that MIME implementations will increase, especially as MIME has been designed to be extensible; additional content types can be defined and supported. See RFC 1341. multisession A feature of CD-ROM discs and drives which enables the CD-ROM to have information written to it in more than one session with access to everything on the disc. Since CDs were historically write once/read many (WORM) media, the early CD-ROM drives would not recognize additional information on the disc if it was written to the disk at a later date from the original information. This wasn’t a problem if the consumer was buying a game disk with 600 Mbytes of information on the original disc. Then Kodak developed a type of image storage format called a PhotoCD in which photographs are scanned, digitized, and saved on a CD-ROM. Since the user could bring the CD-ROM back to the processor to have another roll of film digitized and stored on the same disc (assuming there was still space remaining), it became important to create a CD-ROM format and a CD-ROM drive that could read the data from the multiple sessions. Most CD-ROM drives now are multisession.

multispectral scanner MSS. A nonphotographic imaging system, commonly used on remote sensing satellites, that utilizes an oscillating mirror and fiber optic sensor array. As the mirror sweeps, it transmits brightness values a strip at a time. Multiple detectors are placed in an array in order to sense radiant energy in selected spectral bands. The color seen on satellite image posters that can now be bought in poster and stationery stores is actually added by computers after the image is geocoded (the strips resolved into a cohesive image). In early days of colorizing satellite images, the color assignments were not as appealing as they are currently. The MSS technology was first developed for the Earth Resources Technology Satellite (ERTS-1) in 1968, a program which later developed into the LANDSAT satellites. Multistation Access Unit MSAU, MAU. In a Token-Ring network, a passive concentrating device used in simpler or older Token-Ring installations to extend a Token-Ring setup by allowing a group of computers to be connected to the ring in a star topology configuration. The network still appears as a logical ring, however, with data passing through each computer. This makes the network a little more robust (a bad unit can be bypassed) and flexible than a basic Token-Ring. In general, these are being replaced by active Controlled Access Units. It is better abbreviated as MSAU to distinguish it from Media Access Unit (MAU). With extra ports, multiple MSAUs can be interconnected, provided the basic ring structure is retained. Each MSAU can accommodate Lobe Attachment Modules up to a specified number. See Controlled Access Unit, Lobe Attachment Module, Media Access Unit, Token-Ring network. multisync A device which can handle transmissions at a variety of frequencies. This is a common feature of monitors that allows them to display at various resolutions when attached to different graphics display cards and computers. When installing a multisync monitor for the first time, it is very important to read the documentation with the graphics card or computer to determine the correct frequency settings for the monitor. If the settings are too high, you can damage the monitor. Most consumer color multisync monitors run at about 60 MHz. multitasking Carrying out two or more tasks simultaneously. Many computer systems that claim to be multitasking are actually task switching. In other words, you can switch from one task to another, or one application to another, without closing the first task or application, but the background task freezes; in other words, it does not continue processing while the foreground task is active. If you can run a sound program in the background or format a floppy while doing something else, like using a paint program or a word processor in the foreground, without the sound stopping or jittering or without waiting for the floppy drive to finish, then you probably are working on a multitasking system. Most current workstations and many current microcomputers are fully multitasking.

Historically, multitasking microcomputer operating systems have existed since the early 1980s, the most notable examples being some of systems that ran on the Tandy Color Computer (CoCo), Digital Research’s multitasking version of CP/M, and the AmigaOS (1985), which had pre-emptive multitasking. In the late 1980s some of the other systems began to implement task switching and multitasking. In 1987, the NeXT computer was introduced with multitasking. Workstation-level computers such as Sun stations, SGIs, etc., have been multitasking for some time. By the early 1990s, most microcomputers had some degree of task switching or multitasking, and full multitasking on desktop systems is quickly becoming standard. multithreaded Programming on microcomputers with threads became more common in the 1990s, although the practice has been around longer on mainframes and workstation-level computers. A system which is multithreaded can have a number of processes running independently of the others while still using common resources. Even though they function somewhat independently, they can also be programmed to communicate with one another at intervals or as certain events occur. See threads. MultiUser Talk MUT. A simple multiuser chat program used on computer bulletin boards in the midto late-1980s, written by Jukka Pihl. It was superseded by more powerful, robust programs, most importantly, Internet Relay Chat (IRC). See Internet Relay Chat. Munsell color model A three-dimensional, ordered representation of color relationships for pigments, developed in the early 1900s by an art instructor. For the purposes of illustration, imagine a sphere of no fixed diameter, in which white and black are the north and south poles and hues are represented around the sphere in terms of the basic colors of red, yellow, green, and purple and their complements, and are equally spaced around the perimeter, with the blended colors occurring as transitions at their junctions. But now, unlike a sphere, imagine chroma as a characteristic that radiates outward from the sphere’s central axis, thus influencing the hues that it passes through. Although a complex model, it has the advantage of being somewhat scalable. As new pigments are invented, they can be incorporated into the model without redefining existing colors. See CIE, color space, Maxwell’s triangle. Murgas, Josef (1864-1929) A Slovakian-born priest, artist, and scientist, Murgas spent many years studying and working in Europe and then relocated to the U.S., using “Joseph” as his first name. Like Benjamin Franklin, Murgas was multitalented and tirelessly inquisitive and set up a laboratory in the attic for experiments. Over the years, he received numerous patents for his devices; he transferred these to a syndicate called the Universal Aether Telegraph Company. In 1904, Murgas patented a tone system of wireless telegraphy based on a rotary spark for transmitting faster than the traditional Morse code system. He then built a high transmitting tower which was hailed

in the local newspaper as the “World’s First Telegraphy Tower.” Many prominent citizens witnessed a test demonstration in September 1905 and a public demonstration in November 1905, after which Murgas traveled to New York to meet with Guglielmo Marconi and Reginald Fessenden. Unfortunately, gale force winds destroyed Murgas’ transmitting tower and other bad luck befell him soon after. He was getting on in years and having financial difficulties, so he sold his important invention to Guglielmo Marconi, to prevent his discoveries from being lost to humanity.

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Josef Murgas, pastor of the Sacred Heart Church. [Photo portrait courtesy of the Wyoming Historical and Geological Society, copyright expired by date. ]

A “quenched spark” device from one of Joseph Murgas’ patents from 1911. [U.S. patent diagram, public domain.]

Murgas’ achievements have not gone entirely unrecognized. President Calvin Coolidge honored him by appointing him to the National Radio Commission.

Liberty ship #2881 was named after him during World War II. A U.S. Senate Bill adopted 1 October 1985 urged the Citizen Stamp Advisory Committee of the U.S.P.S. to issued a commemorative stamp of Father Murgas to celebrate Slovak Heritage Month. See Marconi, Guglielmo. Murphy’s law Reportedly stated by Edward A. Murphy as “If there are two or more ways to do something, and one of those can result in catastrophe, then someone will do it.” and also reported as “If there is any way to do it wrong, he will.” However it was originally worded, Murphy’s apropos observation was quoted a few days later, in a news conference, by Dr. John Stapp, a surgeon and research subject in studies of human tolerance to highvelocity ejections and gravity forces (Gs). The statement is often restated more simply as “If something can go wrong, it will.” See Murphy, Edward. Murphy, Edward A. An American engineer involved in human testing of some spectacular acceleration/deceleration experiments in the U.S. Air Force in the 1950s. Following his observations about the configuration of sensors, he is best known for a prescient observation about catastrophes now known as Murphy’s law. See Murphy’s law. Murray loop test A type of diagnostic procedure which uses resistance through a bridge to locate an “open” in a length of circuit. It is similar to a Varley loop test, except that instead of adjustable dials, one arm is eliminated and a variable resistance arm connected in its place, and a third wire is not required. See Varley loop test, Wheatstone bridge. Museum of Independent Telephony In Abilene, Kansas, the home of the United Telephone Company from 1898 to 1966, one of its former presidents, Carl A. Scupin, helped found the Dickinson County Historical Society and Museum. The Museum of Independent Telephony now shares premises with this museum. Museum of Radio and Technology A nonprofit, volunteer-assisted antique radio technology museum, located in a converted elementary school in Huntington, West Virginia. It includes crystal radio sets, vacuum tube technologies, schematics, vintage books and magazines, and other educational resources and exhibits. Museum of Television and Radio A nonprofit, New York-based preservation and education institution established in 1975 by William S. Paley. Its goal is to collect and preserve historic radio and television programs and make them available for public education and use. In 1991, it was moved to the William S. Paley building. It houses over 60,000 programs selected for their historic, artistic, and cultural value. The collection adds about 3000 programs per year. The museum works in conjunction with the Museum of Television and Radio in L.A., California. Both institutions sponsor seminars and exhibitions. Museum of Television and Radio in L.A. Also known as the West Coast Museum of Television and Radio, it was established in 1995 in Los Angeles. This museum is named after Leonard H. Goldenson,

considered a pioneer of the broadcasting industry. It works in conjunction with the original Museum of Television and Radio in New York.

In this music box, tiny spikes have been painstakingly placed in a wooden cylinder to “store” the song.

This music box is similar to a gramophone in that it has a revolving platter; however, the song is stored in small rectangular holes, rather than in a spiral groove. Both music boxes above are included in the American Radio Museum collection.

music box A historic form of entertainment medium which preceded computers in storing data for later playback. Many different means of creating the pattern for the sounds were developed over the years, from nails and holes in boards and cylinders to paper tapes and piano rolls. Jacquard looms were another form of technology which incorporated holes in cards to store a weaving pattern. It was not until the 1970s that magnetic storage of software programs for computers superseded the Hollerith punch cards that followed the same conceptual design as the stored songs on these music boxes. music-on-demand A service offered not long after the invention of the gramophone and the telephone. Since switchboards were operated by humans, it was not difficult to set up a system where the caller could request a song and the operator would put on a phonograph record and play the song to the nearby telephone. The system went out of favor as switchboards became automated and radio and stereo systems became prevalent. It has now come back in a slightly updated form as video-on-demand in which a user

can request a particular movie or other video entertainment through a computer interface or interactive television interface.

Music-on-demand is not a new idea. This historic system, with a phonograph placed near a telephone receiver, was a service for transmitting music requested by a caller.

music on hold Background music on a phone line that is heard when a caller is put on hold. It can be set up to play music from a radio, cassette tape, or CD player, usually with a simple RCA jack near the phone panel. Recorded music is generally better, as most radio stations play advertising, which is not appreciated by most callers. Some people don’t care for background music while on hold, but it’s probably better than not knowing whether or not you’ve been cut off. Musical Instrument Digital Interface MIDI. MIDI is a standard protocol for communication of sound information through a number of specified parameters. Functions provided on MIDI-capable instruments are assigned numeric values which can be digitally intercommunicated and remotely or locally controlled. MIDI capabilities are built into many musical editing and sequencing software programs. MIDI-compatible instruments generally have DIN plugs for interconnecting the various MIDI devices, and usually include MIDI in, MIDI out, and sometimes MIDI through. A simple example of a MIDI setup would be a keyboard connected to the fast serial port or MIDI port of a computer with MIDI-compatible software. There may also be separate speakers, since most computer and keyboard speakers tend to be minimally useful for sound reproduction. MIDI allows the songs from the keyboard to be communicated to the computer and stored and edited. Conversely, compositions created on the computer, sometimes including custom sound patches, can be communicated back to the keyboard. MIDI is not the only music protocol, but it’s definitely the most widespread and best supported. It is built into numerous synthesizers, keyboards, drums, and software music editing and sequencing programs. Musschenbroek, Pieter van See van Musschenbroek, Pieter. MUT See MultiUser Talk.

mute A feature or device that allows sound to be turned off or lowered in volume. A mute button on a phone can cut out the sound to the mouthpiece so something can be said in the background without being transmitted over the connected call (handy if you have to call the dog or ask a co-worker a sensitive question). A mute on a stringed instrument dampens the vibrations of the bridge so that the sound of the instrument is much softer. mutual capacitance Capacitance is the capability or inherent tendency of an object or substances to store electrical charge. This characteristic is related to the composition and structure of the object or substance, but also to the environment within which the entity exists. Influences from other objects will affect the capacitance of an object and increase its capacitance as they draw nearer to that object, hence the phrase mutual capacitance. As a somewhat imprecise example, but one that helps illustrate this idea, think of a satellite orbiting in space. As it draws nearer the Earth, the greater is its tendency to be pulled by the Earth’s gravitational field. Similarly, with objects, the nearer they draw to another object, the greater is the tendency for capacitance, the capability to store a charge. Capacitance is also affected by the medium that exists between objects. Objects covered in plastic or a gel will have a different capacitance in relation to one another than objects separated by air. Thus, capacitance may be expressed as it applies to a particular object but must also be taken into consideration as it applies to the atomic interactions between two (or more) objects. If the objects come into contact with one another, or are connected by a conducting substance, then the capability to store up an electrical charge with relation to one other changes in that the conducting surface effects a discharge or balancing of charges between the two objects. In general, electrical conductors have higher capacitance than, say, a block of wood, but even people store up electrical charges. The human body acts as a capacitor when it picks up electrical charges through friction contact with carpets, for example. The next time you touch a conducting surface after storing up a charge, you may feel a spark as the excess electrical energy in your body is rapidly discharged. The extra charge is not always discharged quickly, however. If you hang around without generating a lot of friction with your feet nor having any contact with highly-conducting surfaces, you will still gradually discharge the stored up charge as it “leaks” more slowly into lesser-conducting materials such as the air, and wood or vinyl floors. See grounding, static electricity, triboelectricity. MUX See multiplexer. MVIP Multi-Vendor Integration Protocol. See MultiVendor Integration Protocol. MVL 1. Man Vehicle Laboratory. A lab within the Center for Space Research (CSR) at the Massachusetts Institute of Technology, founded in 1962. 2. See Multimedia Virtual Laboratory. 3. Multimedia and Visualization Laboratory. See Multimedia Learning Laboratory. 4. See Multiple Virtual Line.

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MVP multichannel video programming. Any of a variety of types of multiple-channel video programming genres, including television, network animations, Internet streaming video, or video programming delivered through traditional or fast data-rate phone lines. Due to the continued need to review, assess, and regulate video programming, the Federal Communications Commission prepared a report in 1999 on MVP that was released in January 2000. In its report, the FCC described a number of aspects of video programming, including the market share of different means of delivering programming, and reiterated the belief that competition was the best way

to promote broadbased access to video programming and competitive rates for the general public. MVPD multichannel video programming distributor/distribution. A broadcast distributor of a number of video programming channels, usually provided through cable TV or satellite feeds. Broadband Internet is now considered to be a viable distribution channel. See MVP. MVS Multiple Virtual Storage. MXR 1. mixer. 2. multiplexer. MZI Mach-Zehnder Interferometer.

n 1. abbrev. nano-. See nano-. 2. In mathematics, a symbol for a numerical quantity used to denote that any number can be substituted in place of the n or, quite commonly, n will represent any value within a stated number set such as any positive integer (whole numbers greater than zero). It is usually written in italics in lower or upper case. Scalable solutions to network configurations or database data sets are sometimes called n solutions to indicate that the system can be expanded to handle exceedingly large numbers or quantities far in excess of what might be needed in any given situation. See N definition #4. N 1. abbrev. noise, usually as it pertains to signal interference. Thus, S/N represents signal-to-noise ratio and C/N represents carrier-to-noise ratio. 2. abbrev. “north,” on a magnet or compass. The north-seeking end of a compass needle points to a region near the Earth’s North Pole called magnetic north. 3. symb. “on,” with F as the corresponding symbol for “off.” 4. symb. the last component, value, routine, link, or other virtual, conceptual, or physical aspect of a multipart system. In this context, it is usually written in italics. In a database, for example, N may be the largest conceivable number of records that might be expected to be needed or entered. In a distributed network, N may represent the largest number of hops that might be expected for a data transmission path. N is an important concept in both programming and physical topologies. The concept of N as a theoretical maximum enables planners to design and construct systems with the view of making the system efficient within the perceived constraints of N. See n definition #2. See N definition #1. 4. In a Central Office telephone code, any integer between 2 and 9. See NXX. N connector A standardized medium-power, barrelshaped cable/device coupler for interconnecting components in a system or devices on a network. N series connectors and adaptors come in a variety of shapes and configurations from simple connectors to extend the length of a cable to adaptors to change the “sex” of the cable between male and female to terminators for establishing the end link in a series of connections. N connectors are selectively coated in nickel, silver, or synthetics over brass, phosphor bronze, or beryllium

N

copper and typically support 50-ohm signals (though 70-ohm versions are available). They are widely used for connecting radio frequency (RF) coaxial components. For Ethernet connections, 10Base-5 “thick” Ethernet cables with N connectors are becoming less common in favor of 10Base-2 “thin” Ethernet cables with BNC connectors or 10Base-T twisted-pair phonestyle RJ-45 connectors. See F connector. N port, node port. A port that enables an endstation device (peripheral, computer, etc.) to be connected as a node in a Fibre Channel network. The N port is connected to the switched fabric port or F port. The N port is assigned a higher address than FL and NL ports and thus would have lower loop control priority compared to these ports. A name server in the Fibre Channel fabric switch typically uses a discovery process to determine the fabric topology to obtain the addresses of other N ports for port logins. The N port may be built into the connected device or may be contained on an interface board, such as a PCI-compatible board in a computer. High bandwidth devices, such as broadband storage devices, may have multiple Fibre Channel ports. See F port, FL port, NL port. n region In a semiconductor, a region in which the conduction-electron density exceeds the hole density. Usually referenced in relation to the p region, the n materials interact with the p materials at the p-n junction in some types of semiconductors. See p region, p-n junction. N Series Recommendations A series of ITU-T recommendations providing guidelines for the maintenance of international sound programming and television transmission circuits. These guidelines are available as publications from the ITU-T for purchase from the Net. Since ITU-T specifications and recommendations are widely followed by vendors in the telecommunications industry, those wanting to maximize interoperability with other systems need to be aware of the information disseminated by the ITU-T. A full list of general categories is listed in Appendix C and specific series topics are listed under individual entries in this dictionary, e.g., K Series Recommendations. See N Series Recommendations chart.

N

ITU-T N Series Recommendations Recom.

Description

General, Definitions

N.17

Monitoring the transmission

N.18

Monitoring for charging purposes, releasing

N.21

Limits and procedures for the liningup of a sound-program circuit

N.23

Maintenance measurements to be made on international sound-program circuits

N.1

Definitions for application to international sound-program and televisionsound transmission

N.54

Definition and duration of the line-up period and the preparatory period

N.2

Different types of sound-program circuit

N.52

Multiple destination television transmissions and coordination centers

N.3

Control circuits

N.60

N.4

Definition and duration of the line-up period and the preparatory period

Nominal amplitude of video signals at video interconnection points

N.61

Measurements to be made before the line-up period that precedes a television transmission

N.5

Sound-program control, subcontrol and send reference stations

N.10

Limits for the lining-up of international sound-program links and connections

N.62

Tests to be made during the line-up period that precedes a television transmission

N.11

Essential transmission performance objectives for international soundprogram centers (ISPCs)

N.63

Test signals to be used by the broadcasting organizations during the preparatory period

N.51

Definitions for application to international television transmissions

N.64

Quality and impairment assessment

N.67

Monitoring television transmissions – use of the field blanking interval

N.73

Maintenance of permanent international television circuits, links and connections

N.86

Line-up and service commissioning of international videoconference systems operating at transmission bit rates of 1544 and 2048 Kbps

N.90

Maintenance of international videoconference systems operating at transmission bit rates of 1544 and 2048 Kbps

N.81

Definition for application to international videoconference transmissions

Administration N.55

Organization, responsibilities and functions of control and subcontrol international television centers and control and subcontrol stations for international television connections, links, circuits and circuit sections

Testing, Monitoring, and Measurements N.12

Measurements to be made during the line-up period that precedes a soundprogram transmission

N.13

Measurements to be made by the broadcasting organizations during the preparatory period

N.15

Maximum permissible power during an international sound-program transmission

N.16

Identification signal

Supplements N.Sup5.1 Requirements for the transmission of television signals over long distances N.Sup5.2 Setting-up and testing of international videoconference studios N.Sup6.1 Effect on maintenance of the introduction of new components and of modern equipment design

N-1, N-minus-one The second-to-last or penultimate node, device, link, router, hop, subroutine, loop, or other virtual or physical link or component. This concept is important in many respects. The secondto-last link in a programming loop, a physical or virtual network or other multipart system may have to be handled or configured differently, given that the next virtual or physical component in the system is the last. The penultimate item or data bit is often significant in programming routines. For example, in computer sorting algorithms, the number of iterations required in a particular function is frequently equal to N-1. The handling of software stacks, dynamic groupings of stored data, also is related to the concept of the penultimate item or data grouping in the stack. In routines where the program ends if it reaches the last or N data set, an awareness of reaching the penultimate set may be important to restarting, backtracking, or otherwise looping back and continuing program execution. See N definition #4. N-ISDN Narrowband ISDN, Narrowband Integrated Services Digital Network. Definitions vary but, in general, Narrowband ISDN is used to refer to earlier installations of ISDN providing lower data rates through copper wires as opposed to newer Broadband ISDN providing higher data rates through fiber optic cables. See ISDN for a fuller explanation. N-scope A type of radar display in which the target appears as a pair of vertical blips coming from a horizontal time base. The direction of the target is inferred by the amplitudes of the related vertical blips. A target distance can also be determined by comparison to a pedestal signal along the base line. N/A 1. not applicable. 2. not available. NA 1. See naming authority. 2. network administrator/administration. 3. See Night Answer. 4. night attendant. 5. North America. NAB 1. See National Alliance of Business. 2. See National Association of Broadcasters. NABTS See North American Basic Teletext Specification. NAC 1. Network Access Center. 2. See Network Access Control. 3. See Network Applications Consortium. 4. See Numbering Advisory Committee. 5. See null attachment concentrator. NACIC See National Counterintelligence Information Center. NACN See North American Cellular Network. NADC See North American Digital Cellular. NADF 1. See North American Directory Plan. 2. North Atlantic Directory Forum. nadir In satellite imaging, a point on the ground centered vertically below a remote sensing platform. NAK See negative acknowledge. name resolution A means of associating an assigned name with its origin, location, or other relevant characteristics. In a network where a name has been used as a mnemonic alias to allow easy recognition of an address, application, or process, there needs to be a mechanism to resolve the name into a form that can

be easily recognized and subsequently located by the system. In other words, mysite.com has to be translated into a machine-readable address of the location of the host site for mysite.com. This is done through name resolution, usually through a lookup table or larger database. Sometimes the name itself will provide some information about its origin or date of establishment, e.g., the name is a set of alphanumeric characters assigned according to a system that can be understood by humans. See naming authority. naming authority 1. A legislative or organizational body that assigns names, usually as unique identifiers. Various types of naming structures include hierarchical, flat, random, etc. There are many wellknown naming authorities: the U.S. Library of Congress; R.R. Bowker (ISBN); IANA (Internet). On the Internet, the various registered domains may assign subauthorities and subnames for local machines. See IANA. 2. In a hierarchical document management system, a tree of entities which provides a unique identifier to each document. This task may be shared by subauthorities. NAMPS Narrowband Analog Mobile Phone Service. An analog cellular communications technology which provides triple the capacity of an analog cellular voice channel by splitting the channel into 10 kHz bandwidth narrow bands. Narrowband standards were released by the Telecommunications Industry Association (TIA) in 1992 (IS-88, IS-89, IS90). Digital mobile phone services are gaining ground on traditional analog systems. See AMPS, DAMPS, code division multiple access, time division multiple access. NAMTS See Nippon Advanced Mobile Telephone System. NANC See North American Numbering Council nano- (abbrev. – n) A unit prefix for one billionth (North American system), or 10 -9, that is, .000 000 001. NANOG See North American Network Operators Group. NANP See North American Numbering Plan. NANPA See North American Numbering Plan Administration. NAP See Network Access Point. NAPP See National Aerial Photography Program. NAPT Native American Public Telecommunications, Inc. narrowband 1. A term which varies in definition depending upon the industry and its bandwidth needs, and on the current state of technology. Narrowband usually represents the lower end of the available capacity or spectrum of a system. In some cases it is used to denote a single band within a multiplexed group of bands sent more-or-less simultaneously. In traditional telephony, it represents a subvoice-grade line. In cellular communications, it represents one division of the broadcast spectrum consisting of a channel frequency (CF) of about 30 kHz, usually accomplished through frequency division duplexing (FDD). See AMPS, NAMPS.

N

Narrowband Analog Mobile Phone Service See NAMPS. narrowband ISDN ISDN services at basic channel speeds up to 64 kbps, which is fine for voice and some data communications, but only adequate for applications like full-motion video, or video and sound. Efforts are being made to incorporate new standards into broadband ISDN (B-ISDN) that will remove the fixed channel structure limitation of narrowband ISDN. narrowcasting A type of program delivery that targets specific people and often specific services to those people. If broadcasting is considered to be program delivery to a wide and sometimes scattered audience, from one to many, then narrowcasting can be seen as one to one or one to few. For example, electronic industries’ personnel might subscribe to programming on circuit board fabrication. At an even more specific level is “pointcasting,” that is, program services which target user-selected information, a type of electronic clipping service providing electronic information on specified topics of interest. NARTE See National Association of Radio and Telecommunications Engineers. NAS See network-attached storage. NASA National Aeronautics and Space Administration. nasa7 A double-precision Systems Performance Evaluation Cooperative (SPEC) benchmark used in scientific and engineering applications. A benchmark tends to be a specific quantitative measure of a particular aspect of computer functioning, and by itself conveys a picture of overall system performance. However, in the specific context for which it is intended, a benchmark can provide valuable information for design engineers, researchers, and manufacturers. Nasa7 generates input data, performs one of seven floating point-intensive kernel routines, and compares the results against an expected reference measure. It is used to evaluate performance, memory, I/O operations, and networking factors. See benchmark, Rhealstone, Whetstone. NASD Project Network-Attached Storage Devices Project. A project of the National Storage Industry Consortium (NSIC) to explore, validate, and document the technologies needed to enable the deployment of network-attached storage device systems and subsystems. The project was initiated because the trend towards large distributed networks is causing people to rethink the most efficient ways to implement storage capabilities, and more networks are using remote rather than local storage to handle large data repositories. Fibre Channel is seen as one of the technologies appropriate for fast-access remote storage. See National Storage Industry Consortium. NASDA 1. National Association of State Development Agencies. 2. See National Space Development Agency of Japan. NASTD See National Association of State Telecommunications Directors. NATA See North American Telecommunications Association.

National Aerial Photography Program NAPP. A program initially established in 1980 as the National High Altitude Photography (NHAP) program. In 1987, the height of the satellites was lowered, and the name changed to NAPP. NAPP is administered by the U.S. Geological Survey’s National Mapping Division, and exists to coordinate the collection and processing of aerial photos of the 48 contiguous states and Hawaii in a format that meets the requirements of a variety of U.S. Federal and state agencies. National Alliance of Business NAB. An association established to promote innovative, long-term solutions for improving the quality of the workforce, in terms of productivity, education, and security. National Association of Broadcasters NAB. A well-known American broadcast industry association providing support and education to its members through literature, standards activities, programming, conventions, and seminars. http://www.nab.org/ National Association of Radio and Telecommunications Engineers NARTE. An international professional association which provides support to members along with certification programs. National Association of Regulatory Utility Commissioners NARUC. A Washington D.C.-based organization serving the needs of the various United States government utility commissioners. http://www.naruc.org/ National Association of State Telecommunications Directors (NASTD). An association of telecommunications professionals in state government engaged in the promotion and advancement of effective telecommunications policies and technology implementation to improve government operations. NASTD was founded in 1978 and is affiliated with the Council of State Governments (CSG). It includes representatives from the American states, territories, and the District of Columbia. http://www.nastd.org/ National Association of Telecommunications Officers and Advisors NATOA. A professional association which supports and services the telecommunications needs of local governments. NATOA provides education, information, and advocacy for their members. http://www.natoa.org/ National Bell Telephone Company A merger of the Bell Telephone Company and the New England Telephone Company, in a bid to achieve widespread national coverage of services. A court decree dissolved the company only 4 years later. National Broadcasting Company NBC. A major broadcast company for many decades, formed in 1926 by David Sarnoff. NBC provides general television programming, entertainment, sports, news, local/interactive, programming transcripts, contests, games, and arts. See Sarnoff, David. National Bureau Of Standards NBS. A bureau of the U.S. government which provides testing and standardization services. The NBS had an important role in the development of early computing devices in the 1940s when it undertook the construction of two large-scale computing machines for its internal

needs, one to be installed on each coast. This resulted in the building of the Standards Eastern Automatic Computer (SEAC) and the Standards Western Automatic Computer (SWAC). National Cable & Telecommunications Association NCTA. Formerly the National Cable Television Association, the NCTA is the primary trade association of the cable television industry in the U.S., founded in 1952. It provides members with industry information and a unified voice for advancing the technology and industry of cable telecommunications, serving more than 150 cable program networks. NCTA hosts an annual industry trade show. http://www.ncta.com/ National Cable Television Association NCTA. A trade association representing the cable broadcast industry founded in 1952. NCTA represents the interests of its members to public policy makers in the U.S. Congress, the judicial system, and the public. NCTA hosts a large annual trade show. NCTA is now the National Cable & Telecommunications Association. National Center for Supercomputing Applications NCSA. A research center at the University of Illinois, best known for the development of NCSA Mosaic, the historic Web information browser that preceded Netscape Navigator. National Code Change A designated day in the U.K. when old telephone codes and numbers were changed to revamp the system. New codes and telephone numbers became available in August 1994 and the Code Change took place in April 1995. On the same day, the dialing code for international calls originating in the U.K. changed from 010 to 00. National Committee for Information Technology Standardization NCITS. A U.S. organization for developing national information technology (IT) standards in cooperation with national and international standards bodies. http://www.ncits.org/ National Communications System NCS. A branch of the U.S. government formed in 1962 during the Cuban Missile Crisis. The recommendation of an interdepartmental committee reporting to President John F. Kennedy was to form a single communications system to serve the President, the Department of Defense (DoD), diplomatic and intelligence activities, and civilian leaders. The NCS was officially established in 1963 to link, improve, and extend the communication facilities and components of various federal agencies. It cooperates with various standards bodies, and develops emergency procedures for the American communications infrastructure. It also provides documents and CD-ROMs, including a Glossary of Telecommunications Terms (FS-1037C). The NCS is administered by the General Services Administration (GSA). See Glossary of Telecommunications Terms. http://www.ncs.gov/ National Continental Telephone, Telegraph & Cable Company of America Founded in 1899, this ambitious undertaking was an attempt to gain control of all the independent telephone companies, that is, all those not controlled by Bell. Despite backing by some of America’s richest high-profile financiers,

this project was unsuccessful. National Coordinating Center NCC. A joint U.S. government-industry organization established by the National Communications System (NCS) to provide for the U.S. government’s telecommunications service requirements. The NCC initiates, coordinates, and restores NS/EP telecommunications services. It is one of several divisions of the Office of the Manager of the National Communications System (OMNCS). National Coordination Office for Computing, Information, and Communications NCO. A U.S. information and communications coordinating agency. http://www.hpcc.gov/ National Counterintelligence Information Center A U.S. government center within the National Security Council (NSC) for coordinating the identification and countering of foreign intelligence threats to the U.S. national/economic security. National Digital Cartographic Data Base NDCDB. A U.S. database of digital cartographic/ geographic data files compiled by the U.S. Geological Survey (USGS). The database includes elevation, planimetric, landcover, and landuse data at various scales. National Electrical Code NEC. A code developed to safeguard public safety and property from hazards associated with the use of electricity. This includes wiring and electrical device construction, materials, installation, and maintenance and is adopted in many parts of the country as law for various building, equipment, and utility pole (below supply space) installations. The Code is developed by the American National Standards Institute (ANSI) and is published by the National Fire Protection Association (NFPA). See National Electrical Safety Code. National Electrical Safety Code NESC. A code governing electrical facilities located in public rightsof-way to ensure the safety of the public and installation/maintenance professionals. It is published by the Institute of Electrical and Electronics Engineers (IEEE). See National Electrical Code. National Emergency Number Association NENA. A not-for-profit standard-setting organization that supports and promotes the development and availability of a universal emergency telephone number system (currently 911). NENA was founded in 1982 as a result of meetings of the National Telecommunications Information Administration (NTIA). NENA further supports research and education in the advancement and use of emergency number services. http://www.nena9-1-1.org/ National Exchange Carrier Association NECA. A nonprofit organization established by the Federal Communications Commission (FCC) in 1983 to administer issues related to service and access charges. The NECA serves the interests of incumbent local exchange carriers (LECs), and administers the universal service fund (USF), which subsidizes certain loop services. http://www.neca.org/ National Federation of Community Broadcasters NFCB. A national U.S. alliance of noncommercial community-oriented radio wave broadcast stations

N

and producers. The NFCB was founded in the 1970s as a result of discussions at a meeting called the National Alternative Radio Konvention (NARK). It subsequently provided assistance and education to community broadcasters including the publishing of Audiocraft and The Public Radio Legal Handbook as standard references. In 1995, the head office was moved from Washington, D.C. to San Francisco. NFCB member stations are committed to community support and participation. They are funded by listeners, grants, and the Corporation for Public Broadcasting (CPB). Almost half of them service rural communities, and a third are dedicated to minority radio broadcasting. The NFCB has become a lobbying voice at Congressional hearings and liaises with other national organizations. Lynn Chadwick has been credited with long-term leadership of the organization through some of its most important growth and development phases. See Community Broadcasters Association, Communications Policy Project. http://www.nfob.org/ National Geophysical Data Center NGDC. One of three data and information centers of the U.S. National Environmental Satellite, Data and Information Service (NESDIS). National High Altitude Photography NHAP. Originally established in 1980 with satellites at 40,000 feet, the height was lowered to 20,000 feet, and the program renamed to National Aerial Photography Program in 1987. See National Aerial Photography Program. National Communications System NCS. A governmental organization established in 1963 as a result of the Cuban missile crisis during which the U.S., NATO, and the U.S.S.R. experienced communications problems that could have had deadly repercussions. Following the crisis, President Kennedy ordered the investigation of national security communications and a committee recommended a single, unified system to serve the President, the Department of Defense (DoD), and other relevant bodies. The NCS focused on interconnectivity and survivability of an extended, interlinked governmental communication system. In 1984, the NCS’s mandate was broadened to include national security and emergency preparedness. Support for the NCS within the Operations Division is provided by Training, Planning & Operational Support (TPOS). See National Coordinating Center for Telecommunications. http://www.ncs.gov/ National Coordinating Center for Telecommunications NCC. A joint government and industry organization for coordinating the initiation, restoration, and reconstitution of U.S. government national security and emergency preparedness telecommunications services in the U.S. and abroad. The National Communications System Operations Division (N3) provides guidance to NCC. See National Communications System. http://www.ncs.gov/ncc/ National ID Card An identification concept proposed many times over the decades for a variety of reasons. In the U.S., there has been a great deal of

opposition to the concept, with concerns about security breaches (people using the information in unethical ways to access private information in centralized databases), loss, replacement, forgeries, and more. In a sense, National ID Cards already exist for non-American legal residents (and a National ID Card doesn’t solve the problem of illegal residents). The commonly called Green Card (Immigration Visa for Resident Aliens/Permanent Residents) is a biometric national identification card issued over the course of many decades that includes a photo and a fingerprint (bio metric identifier) tied to a Federal database that already serves the purposes most people want a National ID Card to cover. To get a Green Card, you have to provide birth, background, educational, and other personal information to the Federal Government and be approved through a background check and interview, which is usually repeated approximately every 10 years. Asking every U.S. citizen to also carry a National ID Card in addition to the many driver’s license/passport/birth certificate/social security documents already issued calls to question why yet another card should be issued and how it would be any different or better than the documents already routinely carried. Some people have even compared it somewhat radically to the skin branding that the Nazi regime carried out to identify Jewish people in the World War II holocaust. A National ID Card can be easily lost, as with any other card, and fall into the wrong hands. Wrongdoers often use forged or stolen documents; this might give them one more document to forge or steal and may not have any substantial security benefits in relation to the increased security risks associated with the loss of the card. Nevertheless, after the events of September 11, 2001, the issue of National ID cards has again been brought forward and will no doubt be debated for a long time. In the world of electronics, where the information on the ID card may be directly linked to a powerful central database, it must be carefully weighed whether a National ID Card program should be undertaken, especially given that, once the database exists, it may over time be commandeered for other purposes by future governments, or eventually be used by law enforcement agencies to track and profile individuals without their knowledge. Stranger things have happened in the past. National Information and Communications Infrastructure – Africa NICI. A framework for developing policy, guidelines, regulations, and laws for directing and shaping Africa’s communications infrastructure. In 2001, the number of Internet users in Africa was approaching 3 million, the majority being in the Sub-Saharan region, primarily South Africa. National Information Infrastructure NII. The name for the political, administrative, and physical underpinnings of an interconnected collection of public and commercial national narrowband and broadband data networks. One of the biggest

stakeholders in the NII is the National Information Infrastructure Advisory Council (NIIAC), established in 1994 through a 1993 executive order. The NIIAC is responsible for advising the government on a national strategy for promoting development of the NII and the Global Information Infrastructure (GII). The NII is a physically and regionally diverse system which is considered as a whole, mainly on the basis of interconnectivity. It includes small and large networks, wireless and wireline connections, public and private systems, and many sizes and types of organizations and individuals. The NII is also known by the catchphrase “Information Superhighway,” although this describes the communications aspect of the NII and could be considered a subset. National Institute of Standards and Technology NIST. This national standards organization is affiliated with the U.S. Department of Commerce. http://www.nist.gov/ National Internet Services Provider NISP or NSP. An Internet Services Provider of national scope, usually with broader regional access and a variety of connection points. The Internet services provided by local ISPs and NSPs are usually similar. The main difference is that national providers often have dialups in major cities that the user can access with a local call when traveling, thus avoiding long-distance connect charges. National ISDN Council See ISDN associations. National Laboratory for Applied Network Research NLANR. An organization that researches leading-edge networks and supports the evolution of a U.S. national network infrastructure. Its main function is to provide technical, engineering, and traffic analysis support to National Science Foundation High Performance Connection sites. NLANR is divided into three main areas serving applications and users, engineers, and measurement and analysis professionals. It began as a collaborative project among NSF-supported supercomputer sites and was established in 1995. National Oceanic and Atmospheric Administration NOAA. A U.S. government agency which sets strategic goals for environmental assessment, prediction, and stewardship and describes and predicts changes in the Earth’s environment, to manage coastal and marine resources. http://www.noaa.gov/ National Public Broadcasting Archives NPBA. Housed at the University of Maryland in the Hornbake Library, the NPBA started as a cooperative project of several broadcasting and educational institutions. It was initiated by Donald R. McNeil, a Public Broadcasting System (PBS) board member, and officially dedicated in June 1990. NPBS provides an archival record of major documents and selected programming from U.S. noncommercial broadcasting history. http://www.lib.umd.edu/UMCP/NPBA/ National Public Radio NPR. A major award-winning producer and distributor of public radio broadcast programs developed by independent producers. Based in Washington, D.C., NPR provides popular shows such as All Things Considered, Car Talk, and

Morning Edition plus NPR hourly news on the Internet. It also hosts lively discussion groups online about issues raised on NPR programs. See Public Radio International. http://www.npr.org/ National Public Safety Telecommunications Council NPSTC. A federation of associations representing and advocating telecommunications for public safety, founded in 1997. Recommendations from the Public Safety Wireless Advisory Committee (PSWAC) are followed up by NPSTC. The associations affiliated with NPSTC include the National Association of State Telecommunications Directors, the Association of Public-Safety Communications Officials – International (APCO), the National Association of State Emergency Medical Services Directors (NASEMSD), and others. http://npstc.du.edu/ National Research and Education Network NREN. A government-funded, gigabit-per-second, national research backbone proposed in the early 1990s after an initial proposal was presented in 1987 to the Congress by the Federal Coordinating Committee for Science Engineering and Technology (FCCSET). It was intended to support voice and video, and to become a significant means of finding and disseminating information. See National Science Foundation. National Research Council NRC. A U.S. organization established in 1916 by the National Academy of Sciences to serve the needs of the science and technology community in advising the federal government. It is now the principal operating agency of the National Academy of Sciences and the National Academy of Engineering. The NRC provides services to the government, scientific and engineering communities, and the public. It is administered jointly by the Academies and the Institute of Medicine. In 1989, the NRC expressed concern in a report about the vulnerability of a fully interconnected public switched network (PSN) and its implications for national security. See Network Reliability and Interoperability Council. http://www.nas.edu/nrc National Rural Telecommunications Cooperative NRTC. A trade organization supporting over 1000 rural utilities organizations in 46 states in delivering telecommunications and information technology services. NRTC was founded in 1986 by the National Rural Electric Cooperative Association (NRECA) and the National Rural Utilities Cooperative Finance Corporation (CFC). In the early 1990s, in partnership with DIRECTV, Inc., NRTC made a significant investment toward launching the first U.S. highpower direct broadcast satellite (DBS) system, acquiring exclusive sales rights to 8% of DIRECTV subscribers. It is now the leading distributor of satellite broadcasting services and hardware to rural consumers. To promote legislative and distribution support for rural satellite technologies, NRTC also collaborated in the development of the Satellite Home Viewer Improvement Act in 1999. See LOCAL TV Act of 2000, Satellite Home Viewer Improvement Act. http://www.nrtc.org/

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National Security Telecommunications Advisory Committee NSTAC. A committee of corporate leaders representing major telecommunications industries providing advice to the U.S. President on issues and vulnerabilities in national security and emergency preparedness telecommunications policies. See National Communications System. http://www.ncs.gov/ National Science Foundation NSF An independent U.S. government agency, established in 1950 to promote public welfare through science and engineering research and education projects through various types of educational and financial support. The NSF was established by the National Science Foundation Act of 1950, and provided with additional authority through the Science and Engineering Equal Opportunities Act. It is administered by the National Science Board appointed by the President with the advice and consent of the U.S. Senate. See NSFNET. http://www.nsf.gov/ National Space Development Agency NASDA. A Japanese national agency established to promote the development and peaceful use of space through the Japanese Space Development Program, NASDA was founded in October, 1969. The headquarters are located at the Tanegashima Space Center, where satellites are launched into orbit. In 1972, a further Tsukuba Space Center was established, followed six years later by an Earth Observation Center and, in 1980, by the Kakuda Propulsion Center. By the early 1990s, NASDA was involved in a number of national and collaborative space experiments. NASDA jointly supports the Geostationary Meteorological Satellite (GMS) system in conjunction with the Japan Meteorological Association. See Geostationary Meteorological Satellite. http://www.nasda.go.jp/ National Spatial Data Infrastructure NSDI. A U.S. Executive Order signed in 1994 under which federal agencies must document, and make accessible through the electronic Clearinghouse network, all new geospatial data collected or produced, either directly or indirectly, using the Federal Geographic Data Committee (FGDC) standard. National Standards System NSS. A Canadian standards association which is managed by and works in conjunction with the Standards Council of Canada and a committee of volunteers to write standards, and to test and certify products and systems. See Canadian Standards Association, Standards Council of Canada. National Storage Industry Consortium NSIC. A nonprofit consortium of more than 50 universities, research laboratories, and corporations dedicated to research and development in digital information storage systems. NSIC is headquartered in San Diego, California, and was incorporated in April 1991. Among other things, NSIC defines, organizes, and manages longer-range research projects such as the Extremely High Density Recording (EHDR) Project and the Network-Attached Storage Devices (NASD) Project. See NASD Project. http://www.nsic.org/ National Technical Information Service NTIS. An

agency of the U.S. Department of Commerce, through the Technology Administration. NTIS is the official source for various types and formats of U.S. government-sponsored global scientific, technical, engineering, and business-related information, supplied by many U.S. government agencies. http://www.ntis.gov/ National Telecommunications and Information Administration NTIA. An Executive Branch agency of the U.S. Department of Commerce founded in 1978. NTIA is responsible for domestic and international telecommunications policy issues, and is a principal advisor to the President. NTIA works to promote efficient and effective uses of telecommunications information and resources in order to support U.S. competitiveness and job opportunities. NTIA is descended from a reorganization of the Office of Telecommunications Policy (OTP) and the Office of Telecommunications (OT). It cooperates with the Federal Communications Commission (FCC) in managing broadcast spectrum administration and assignment. Various endowment and grant programs have been transferred to the NTIA, including the Public Telecommunications Facilities Program from the Department of Health, Education, and Welfare. The NTIA has a laboratory for conducting applied research in telecommunications, located in Boulder, Colorado. See Federal Communications Commission, Institute for Telecommunication Sciences. http://www.ntia.doc.gov/ National Telecommunications Commission - Philippines NTC. An independent government agency created in the late 1970s, superseding the Board of Communications and the Telecommunications Control Bureau. The NTC performs regulatory and quasijudicial functions for enforcing telecommunications in the Philippines. It is affiliated with the Department of Transportation and Communications; however, decisions are accountable directly to the Supreme Court. The NTC traces its origins to a regulatory office established when the Ship Radio Station Law was enacted in 1927. In 1995, a Special Committee for Children was established to deal with the problem of sexual abuse and child prostitution using children as performers or models. Internet entrepreneurs were exploiting and promoting Filipino children as easily available for sexual tourism. Due to the growing prevalence and concern over cable piracy, the NTC formed the Cable TV Piracy Task Force (CTP-TF) to cooperate with other agencies in educating the public about cable piracy with the goal of reducing cable broadcast signals theft. National Telecommunications Damage Prevention Council NTDPC. Initially established in 1989 as the California Common Carrier Steering Committee, the group first addressed contractual issues related to railroad coastal cable ducts. Over time, the mandate of the group grew to support the protection of all below-surface telecommunications facilities.

In the mid-1990s, the name was changed to The National Common Carriers Cable Hazard Prevention Committee and then changed to NTDPC to reflect the broader focus; a number of significant telecommunications carriers joined the organization. The NTDPC is a noncompetitive forum dedicated to protecting all telecommunications networks, regardless of ownership, with a focus on preventing damage to buried facilities forming part of the nation’s communications infrastructure. National Telephone Cooperative Association NTCA. A national trade association representing over 500 small and rural independent local exchange carriers (LECs), based in Arlington, Virginia. Small telephone cooperatives overseas are also becoming part of the organization, in addition to nonlocal exchange businesses (wireless, Internet, cable television, DBS). NTCA promotes the regulatory and educational needs of its members, and supports and coordinates a number of employee benefit programs. http://www.ntca.org/ National Television System Committee See NTSC. native format The structure of a raw application or data file prior to modification for compatibility, emulation, or compression. A format designed to work optimally with a particular architecture. For example, many Amiga computer programs were designed to take advantage of the Amiga’s unique hardware features such as the blitter and NTSC output. Color cycling, hardware sprites, video output, and other graphics capabilities that were “native” on the Amiga were not available on other systems at the time without special hardware add-ons. Native file formats abound in many applications programs, that is, data formats for saved files that don’t work with other applications. Electronic Data Interchange (EDI) was developed as a file-transfer solution for a variety of types of files from otherwise incompatible applications, thus allowing the user to combine the speed and ease of native formats with the practical interchange of data between programs. See ASCII, Electronic Data Interchange. native mode The common way of running software within the natural operating functions of a specific computer platform, i.e., software specifically designed to run on a system without emulation or modification to mimic or support a different architecture. Since no emulation overhead is needed, native mode software typically runs faster than emulation software. In spite of this, the trend is away from native mode software. Since intercompatibility and especially Internet compatibility are high priorities and since machines are now fast enough that emulators run reasonably well, platform-independent, non-native mode software or software which falls somewhere in between is becoming more prevalent and practical. See native format. Contrast with emulator, Java, OpenGL, Perl, platform-independent. NATOA See National Association of Telecommunications Officers and Advisors natural antenna frequency An antenna’s lowest natural resonance frequency when operated without

external capacitance or inductance. natural frequency The frequency at which an otherwise uninfluenced or unimpeded body will oscillate when stimulated to move. natural language A human language, such as Japanese, Russian, English, French, Indian, Chinese, Arabic, Senegalese, Hawaiian, etc. Natural language processing, both in written and spoken form, is one of the ongoing challenges of computing, with many of the algorithms derived from studies in artificial intelligence. natural language programming Natural language computer programming is the creation of computer instructions similar to a human language. The implementation of natural language programming is as yet still somewhat rudimentary and experimental, although success in specific areas has been achieved. Even the BASIC programming language, which was developed to be similar to the English language, is symbolic in its syntax and structure in ways that are different from English. See speech recognition. natural magnet There are two types of permanent magnets. One is a substance that exhibits and retains magnetic properties without application of a current after it has been magnetized with another magnetic source. The second is a substance which exhibits magnetic properties as it comes out of the ground, without needing to be exposed to magnetic influences for it to become a magnet. The second type of permanent magnet is called a natural magnet. See lodestone. natural wavelength The wavelength that corresponds to an antenna’s natural frequency. Matching an antenna’s resonant frequency to the characteristics of the wave being received (or transmitted) is an important aspect of antenna design. nautical mile NM. A standard means of describing a distance traveled through water. A knot is one nautical mile per hour, or 6076 ft (1 knot = 1.15 mph). An international nautical mile is 1852 m. The term knot originates from a physical means of estimating the distance. A log line was marked by knots at 47.33 foot intervals. A weighted log chip was attached to one end and thrown overboard to the stern. It would remain somewhat stationary as the boat moved away, and the line was allowed to run for 28 seconds and then hauled back into the boat. The knots that slipped away were tallied to calculate the boat’s speed. navigate 1. To move on or through, with selective consideration of the path taken along the way. 2. To follow a course through the various features of the Internet, to “surf the Net.” In its broadest sense, the path may be selected in many different ways and combinations, including by geography, topic, name, feature, whim or personal interest, institution, server, etc. Pathways through the Web can be followed through hypertext links embedded in HTML pages. 3. On the World Wide Web, to follow a course through a path of hypertext links set up by the designers of the Web pages. NAVSTAR A series of Global Positioning System (GPS) satellites operated by the U.S. Department of

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Defense, whose navigational signals are available to civilian users. See Global Positioning System (GPS), GLONASS, Standard Positioning Service.

The 19th NAVSTAR satellite was launched in 1993, on board an Air Force Delta II craft. The NAVSTAR satellites are used for GPS data and geodite research. [NASA/Marshall images.]

NAVTEX An international, automated weather and maritime navigational warning distribution system. NAVTEX sends warnings to ships as they move in and out of areas for which broadcast information is available that may be relevant to marine safety. See Global Maritime Distress and Safety System.

Navy Navigation Satellite System NNSS. A system of satellites moving in polar orbits about 700 miles above Earth, which preceded the Global Positioning System (GPS) used today. NNSS Doppler technology could compute group positions on or around the Earth to about 1-meter accuracy by means of multiple readings. The long time between transits over the same location (about 90 minutes), and the difficulty of determining instantaneous velocity led to the development of the GPS system. See Global Positioning System. NBC See National Broadcasting Company. NBFCP See NetBIOS Frames Control Protocol. NBFM narrowband frequency modulation. NBMA nonbroadcast multiple access. NCACHE, DNS NCACHE Negative caching is a part of the DNS specification that deals with caching the nonexistence of a domain name or RRset, thus reducing message load and response time for negative answers. With the growth of network traffic and increased need for quick and frequent resolution of domain names, the importance of negative caching has grown to the point where it was suggested by Andrews and others that negative caching be routine rather than optional. See negative caching, RFC 1034, RFC 2308. NCAR National Center for Atmospheric Research. NCC 1. National Communications Committee. 2. National Coordinating Center. NCCS Network Control Center System. NCHPC National Consortium for High-Performance Computing. NCIA native client interface architecture. An SNA applications-access architecture developed by Cisco Systems. NCIA encapsulates SNA traffic on a client computer, preserving the user interface from the native SNA system so that the end-user can work in a familiar environment and also have direct TCP/IP access. NCITS See National Committee for Information Technology Standardization. NCO See National Coordination Office for Computing, Information, and Communications. NCOP Network Code Of Practice. NCS See National Communications System. NCSA 1. See National Center for Supercomputing Applications. 2. National Computer Security Association. Now the International Computer Security Association. NCSA Mosaic A well-known Internet information browser and World Wide Web client developed at the National Center for Supercomputing Applications. Mosaic was the predecessor to Netscape Navigator distributed by Netscape Communications. Navigator was later declared open source software. See Mosaic for a fuller history; see Netscape Navigator. NCUG National Centrex Users Group. NDCDB National Digital Cartographic Data Base. NDIS See Network Driver Interface Specification. NDSI See National Spatial Data Infrastructure. NDT 1. network downtime. In telephony, the elapsed

time from when network managers become aware of a problem until the moment at which the subscriber’s service is restored. In computer networking, the time during which normal processes are unable to execute due to electrical outages, software crashes, network link disconnections, processing overload, malicious tampering, or unintentional bugs that interfere with processes outside of the application that has the bugs. 2. No Dial Tone. NE See network element. near end crosstalk NEXT. When wires are packed tightly together, and signals are traveling through most or all of the wires, especially in two directions, the signals originating at one end can exceed or interfere with weaker signals coming from the other end, resulting in crosstalk. With much higher speed transmissions media, such as gigabit Ethernet, which involve bidirectional signals in more complex systems of aggregated wires, this can be a severe impediment. One means of compensating for NEXT is to include a NEXT canceler, which detects and adjusts for noise in the circuit. See far end crosstalk. NEC See National Electrical Code. NECA See National Exchange Carrier Association. neck The narrow portion of a cathode-ray tube (CRT) at the end where the electron beams are emitted from the cathode. needle An instrument used to probe the holes in punched metal discs, punch cards, or punch tape, or to create or read the grooves in a phonograph record to play back the sound. A phonograph needle, sometimes called a stylus, is often made of steel or sapphire. needle chatter, needle talk Undesirable sounds produced by the extraneous vibration of a phonograph needle when it comes in contact with a rotating platter. needle telegraph See telegraph, needle. negative acknowledge, negative acknowledgment NAK A commonly used international communications control character which indicates that data was not received, or not received so that it could be understood. This is common to handshaking protocols, in which an acknowledgment is required before the sender can continue. See acknowledge. negative bias In an electron tube, voltage applied to a control grid to make it hold more of a negative charge than the electron-emitting cathode. Manipulation of the control grid is what makes it possible to control the flow of electrons from the cathode to the anode, and thus to create different types of circuits and effects. negative caching The storage of information about the nonexistence of an object, entity, or service. The availability of this information can reduce the time it takes to determine the components or configuration of a system or file. Negative caching statistics are commonly stored in tables or headers, depending on the application. On computer networks, for example, storage of the nonexistence of certain servers or machines can lead to more efficient polling or routing of processes or network services. If certain

printers or fax servers are offline for maintenance, negative caching information can be used to prevent overflowing queues. If certain hosts are offline, routing of packets can be renegotiated through other servers. If certain elements of an image file do not exist, negative caching can be used to prevent expensive production tasks on a printing press or milling machine holding up the line. See NCACHE. negative glow A luminous glow which can be observed between an electron-emitting cathode and the Faraday dark space in a cold-cathode discharge tube. See Faraday dark space. negative image An image in which the dark and the light values are reversed, or in which the complements of the colors are displayed instead of the normal colors; also called an inverse image. Photographic negatives contain a negative image. In desktop publishing, negative images are sometimes created so the printout can be processed some way in manufacturing. For example, an image printed on film for subsequent exposure to a printing plate might be printed in negative. Negative images are often used for posterization and other special effects. In monochrome television display systems, a negative image may arise from reversal of the polarity of the signals. negative plate, negative terminal In a storage battery, the grid and any conductive material directly attached to the negative terminal, that is, the terminal that emits electrons when the circuit is active. negative-going video In a four-field analog video sequence, a reference point in the subcarrier cycle (the other being positive-going) that is related to the start of an NTSC video frame. The positive-going and negative-going cycles alternate in sequence to form the video field. A video frame is constructed by drawing scanlines in a sequential, repeating pattern from left to right and top to bottom at a specified rate (e.g., 30 frames per second). When the electron beam is moving from right to left to begin the next line (or from bottom right to top left when it has finished the full screen) it is turned off or “blanked” so as not to interfere with the image on the screen. In an interlaced system, it takes two screen images to make up the full frame since only the odd or even lines are drawn with each half-frame. The process happens so fast that the human eye resolves two half-frames as a full image (although a bit of flicker may be noticed). A horizontal drive (H drive) triggers a low-voltage negative-going pulse at the beginning of the horizontal blanking point (in standard systems this is at the right edge of the screen, the trailing edge of the scanline that has just been drawn) and ending where the edge of the sync for the next line begins. Subcarrier/horizontal (SC/H) phase resolution is synchronization between the zero crossing point of the subcarrier sine wave and the negative-going (leading) edge of the horizontal sync in the first field and a specified line at the halfway point. This aids in resolving phase issues that are important in vide tape recording. The timing provided by the leading edge

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of a negative-going pulse to the leading edge of the subsequent negative-going pulse can be used as a start-stop mechanism. Similarly, negative-going and positive-going edges of the same pulse can be useful for timing and integration of signals from multiple video components. Some display monitors expect horizontal and vertical sync polarities to conform to certain specifications and, thus, some graphics output devices will include a hardware switch to output the signal with negative-going polarities. A grab pulse can be a positive-going or negative-going polarity output pulse for synching video to a component such as a frame grabber. Negroponte, Nicolas Outspoken author, philosopher, and educator, Negroponte is well known for his lectures and back-page editorials in Wired magazine. He is the founder and director of the Massachusetts Institute of Technology’s celebrated Media Laboratory, established in the late 1980s. Prior to that, he founded MIT’s Architecture Machine Group, a think tank and research lab for discussing new approaches to human-computer interfaces. neighbors A networking term used to describe nodes attached to the same link. NENA See National Emergency Number Association. neon gas (symb. – Ne) An inert gas with many industrial and commercial applications. When ionized, neon glows red. It was popularly used to illuminate signs in the 1940s and 1950s, and is still used for this purpose, along with other gases that emit other colors. neon lamp A long glass illuminating tube with an electrode at each end and low-pressure neon gas inside, which may be angled into interesting shapes. When illuminated, it produces a red-orange light that can be seen in daylight and can penetrate fog better than most conventional types of lights. Neon has also been used in older tubes in the broadcasting industries, in simple oscillating circuits, and in commercial signs. neper (pron. – nay-per, symb. – Np ) A dimensionless mathematical unit for expressing relative measurements. It is used to express ratios that are useful in physics and electronics, as for voltage and current relationships. The neper is similar to the decibel except that it is established upon a base of 2.718281828...; quantities expressed by nepers are based upon natural (Napierian) logarithms rather than base 10 logarithms. The neper is not a Système Internationale (SI) unit, but it is widely used and thus 1 Np has been assigned an SI equivalent value of 1. In terms of decibels, 1 Np = 8.686 dB. The neper is named after the Scottish mathematician John Napier (Jhone Neper) who did historic research on logarithms. See decibel; Neper, Jhone. Neper, Jhone (1550-1617) A Scottish mathematician, now more commonly known as John Napier, who did pioneer work in logarithms and published Mirifici logarithmorum canonis descriptio in Latin,

in 1614. There were no computers in those days, so logarithmic tables had to be methodically calculated and inscribed by hand. Neper published a followup document in 1617 describing a means of simplifying calculations using ivory numbering rods (Napier’s bones) marked with numbers (a physical calculating device that facilitates computations just as a slide rule facilitates computations). Neper’s logarithmic discoveries were important fundamentals for many future discoveries in mathematics, physics, and astronomy. Nernst effect A potential difference develops in a heated metal band or strip when it is placed perpendicular to a magnetic field. NESC See National Electrical Safety Code. NESDIS National Environmental Satellite, Data and Information Service. nesting In computer programming, a nest is a programming structure in which a block of data or a function, procedure, or subroutine is logically placed within another structure. Nesting is a means of organizing information and the order of processing data. Nesting is a common means of setting up routines to repeat, sometimes within recursively repeating routines several layers deep. Here is an example of a trivial, inelegant progress and warning subroutine in BASIC-like pseudocode which executes i, the outer loop, a specific number of times (3) and produces an audible beep signal each time it begins; then nested within i is j, which executes up to the value of a variable n - 1, which comes from outside the subroutine, but only if n has a value of minimum_var or more. Further nested within this are two print statements, if j is 50 or less, the dashes are not printed, but three dots are always printed (provided n has a value of the prestated minimum_var or more). If the routine fails the minimum variable test (minimum_var), then three signal beeps will be sounded in succession, with no characters printed. At the minimum_var value or above, however, three dots followed by three dashes will be printed, a visual SOS warning sign that a value of 50 has been exceeded: Nest_routine (n, minimum_var): For i = 1 to 3 Print beep For j = 1 to n-1 unless n < minimum_var Print “...” Print “—” if j > 50 Next J Next I Return While nests can be many layers deep, it may be a sign of weak program structure if they routinely are more than about three or four levels deep. See recursion. Net Citizen, Net Denizen See Netizen. Net Police A generic term for the various individuals who moderate communications on the net for appropriateness, tact, good taste, honesty, and fair

use. Although some resent the activities of the Net Police, for the most part, these folks are committed, caring, hard-working volunteers who want to see the broadest possible access to the Internet, and who encourage voluntary compliance with Netiquette in order to try to prevent government regulation of the Internet’s open communications forums. See Netiquette. NET/ROM A packet radio communications protocol which has largely superseded AX.25. It provides support for a wider variety of types of packets with automatic routing. See AX.25. NetBIOS Frames Control Protocol NBFCP. Originally the NetBEUI protocol, NBFCP establishes NBF Protocol to run over Point-to-Point Protocol (PPP). NBFCP enables an end system to connect to a peer system or to the local area network (LAN) in which the peer is located. It is not suitable for interconnecting LANs. NBFCP defines a method for encapsulating multiprotocol datagrams, a link control protocol (LCP) for establishing and configuring the data link connection, and a family of network control protocols (NCPs) for establishing and configuring different network-layer protocols. See RFC 2097. NETBLT NETwork BLock Transfer Protocol. This is a transport level networking protocol intended for the fast transfer of large quantities of data. It provides flow control and reliability characteristics, with maximum throughput over different types of networks. It runs over Internet Protocol (IP), but need not be limited to IP. The protocol opens a connection between two clients, transfers data in large data aggregates called “buffers,” and closes the connection. Each buffer is transferred as a sequence of packets. Enhanced Trivial File Transfer Protocol (ETFTP) is an implementation of NETBLT. See RFC 998. Netcast Broadcasting through the Internet. See Webcast. Netgod An individual recognized by colleagues, or a large body of Internet participants, as having made significant contributions to the development and functioning of the Internet. NetHead, Net Junkie Someone who has no life outside the Internet. An Internet addict (yes, they exist). Employers sometimes have to curtail the activities of NetHeads who are accessing the Internet for personal entertainment on company time. Parents sometimes are concerned, as well, that their children will spend too little time outside or with friends and relatives, if they spend too much time on the Net. NetHead need not have a negative connotation; sometimes being a NetHead isn’t so bad. The Net has opened up a world of communication to people who are bedridden or have trouble getting around. Not only does the Net give them a world to explore, but people on the Net get to know them without any prejudices they may have toward those who have physical limitations to free movement. Netiquette Newsgroup etiquette, Network etiquette. An important, well-respected voluntary code of ethics and etiquette on the Internet. Many people have

contributed to Netiquette, but it was mainly developed by Rachel Kadel at the Harvard Computer Society, and subsequently maintained by Cindy Alvarez. The whole point of having Netiquette is so that network citizens can enjoy maximum freedom by not abusing the rights and sensibilities of others, so that the Net will remain largely unregulated and unrestricted. This freedom depends upon the cooperation of everyone. In the early days of BBSs, in the late 1970s, most systems were completely open and not password protected. Gradually the constant vandalism and lack of consideration for others caused passwords to be implemented. Eventually, by the mid-1980s, even this was not sufficient to curtail childish or destructive behavior and many of the system operators (sysops) gave up trying to maintain the systems. Many of the same unfortunate patterns of abuse have damaged the USENET newsgroup system, which used to be a fantastic open forum for discussion, with many scientific and cultural leaders participating under their real names in the mid-1980s. Unfortunately, this system is now abused by bad language, inappropriate remarks, and get-rich-quick come-ons. Consequently, many groups have been forced to close up or go to moderated status, and most celebrities now use assumed names. If members of the Internet community realize that it is completely possible to voluntarily appreciate and respect the rights of others, the Internet can remain an open resource for all. It’s a good idea to read Netiquette. Its adherents encourage people to choose voluntary self-restraint and freedom over regulation. See emoticon, Frequently Asked Question, Netizen. Also, Arlene H. Rinaldi’s “Net User Guidelines and Netiquette” in text format is available at many sites on the Internet, including: ftp://ftp.lib.berkeley.edu/pub/net.training/FAU/netiquette.txt Netizen Net citizen or Net denizen. A responsible user of the Internet. Many founders and users of the Internet consider themselves members of a new type of global community that shares and promotes a vision of an open, freely accessible, self-governed communications venue in which participants voluntarily deport themselves with responsibility, integrity, charity, and tolerance toward the many diverse opinions expressed online. A Netizen is one who contributes to the positive evolution of the Net and respects online Netiquette. One could also more broadly say that anyone who uses the Net is a Netizen, although some people online have less polite terms for those who abuse their freedoms and those of others on the Net. See Netiquette. netmask A symbolic representation of an Internet Protocol (IP) address that identifies which part is the host number and which part is the network number through a bitwise-AND operation. The result of this logical operation is the network number. Netmasks are specified for different classes of addresses, and are used in classless addressing as well. See name resolution. NetRanger An intrusion detection utility from Cisco Systems now known as the Cisco Secure Intrusion

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Detection System. A service pack was issued to support the detection system sensor component to reduce the chance of the system being circumvented by an encoding vulnerability. See CodeRed, virus. NETS See Normes Européenne de Télécommunications. Netscape Communications Originally Mosaic communications, Netscape Communications is the developer and distributor of Netscape Navigator, the best-known browser on the Internet. The company was founded by Mark Andreessen and some very experienced business people from Silicon Graphics Corporation and McCaw Cellular Communications. It had one of the highest profile public offerings in the computer industry. See Andreessen, Mark. Netscape Navigator The most broadly distributed and used Web browser on the World Wide Web, and the name of its related server software. Descended from Mosaic, the browser was developed by Netscape Communications and widely distributed as shareware until late 1997. At that point, Netscape made the decision, in 1998, to freely distribute the software as open source software and concentrate on marketing their server software. The first beta release was distributed in 1994. NETscout Applications software from Cisco Systems which provides a graphical user interface (GUI) for network system administrations data collection, reporting, monitoring of statistics, and protocol analysis. Netware A commercial proprietary networking product from Novell Corporation. Netware is widely distributed for use on local area networks (LANs). network An interconnected or inter-related system, fabric, or structure. A logical, physical, or electrical grouping in which there is some electromagnetic or biological intercommunication between some or all of the parts. A broadcast network is a physical and communications association of directors, actors, production personnel, and technologies which together cooperate and are used to create and distribute programming to its viewers. A computer network is one in which computers are able to intercommunicate and share resources by means of wireless and/or wired connections and transmissions protocols. A cellular communications network is one in which a cooperative system of wireless communications protocols, geographically spaced transceivers, relay and controlling stations, and transceiving user devices are used to interconnect callers while moving within or among transceiving cells. network-attached storage NAS. In general terms, a dedicated file storage device or system of associated devices on a network server. The NAS is intended to take the storage burden off the processing server so that a greater amount of storage and more specialized storage-related resources can be concentrated within the NAS. In more specific terms, NAS is the implementation of a storage access protocol over a network transmissions protocol (e.g., TCP/IP) such that the storage resources are concentrated and separate from the process server (and may even be

in a remote location). The advantage of NAS is that storage devices can be placed where it is convenient to install or maintain them and large storage closets can be established for high-end storage needs. The disadvantage is that the burden of the transmissions between remote users and the NAS is handled across the network, increasing traffic over what would occur if the storage devices were associated with individual workstations and decreasing access times, depending upon the distance and the relative load on the network. NAS is often implemented within a storage area network (SAN), which is a broader concept, and may be designated as SAN/NAS. See NASD Project, National Storage Industry Consortium, storage area network. network, broadcast n. A commercial or amateur radio or television broadcast station. A few examples of well-known broadcast networks include CBC (Canada), BBC (Britain), ABC, NBC, and PBS. Amateurs often run local or special-interest radio, television, or slow-scan television broadcasts. See ANIK. network, computer n. 1. A system comprising nodes and their associated interconnected paths. 2. A system of interconnected communications lines, channels, or circuits. A small-scale computer network typically consists of a server, a number of computers, some printers, modems, and sometimes scanners, and facsimile machines. The highway system is a type of network, as is the very effective train system in Europe. See local area network, wide area network. network, social A social communications system consisting of friends, colleagues, and acquaintances. A great deal of the content of human networks consists of unrecorded oral communications (although with email, video phones, and online public chats, recorded conversations are increasing, a dynamic probably of interest to historians and biographers). The term “networking” is often used in association with business and political alliances formed through social contacts, trade shows, trade association memberships, and referrals. network access control NAC. Network policies, configurations, and administrative steps that control the data transmissions to a server, switching/routing component, network, workstation, or peripheral device. Password accounts, dedicated workstations and peripherals, gateways, firewalls, and employee passcards are examples of NAC components and procedures. NAC policies and systems are of particular interest at institutions where sensitive information or expensive services must be handled efficiently or protected from tampering or misuse. NAC is important in business and educational local area networks and particularly important in classified government and military systems, especially on systems where links to the outside world through the Internet are desired without compromising internal security. In some cases biometrics (e.g., iris scans) may be used to control

access to computer terminals or rooms. Monitors and logs may be implemented to oversee general use and to provide an audit trail to check back through unusual activities. See authentication, firewall, gateway. Network Access Point NAP. A major backbone point which provides service to ISPs and is designated to exchange data with other NAPs. NAP was a development in the mid-1990s which arose from the change in the U.S. Internet from a single, dominant backbone to a shared backbone across four NAPs (California, Illinois, New Jersey, Washington, D.C.). See MAE East, MAE West, Metropolitan Area Ethernet, Public Exchange Point. network address An identifier for a physical or logical component on a network. Components often have a fixed hardware address, but may also have one or more logical addresses. Logical addresses may change dynamically as the network is altered physically, or as the network software is tuned or protocols changed. Network addresses are typically associated with nodes and stations. See address resolution, domain name, Media Access Control. network administrator 1. The human in charge of the installation, configuration, customization, security, and lower level operating functions of a computer network. On larger networks, these tasks may be divided among a number of professionals. See SysOp. 2. A software program that handles details of the job of a human network administrator. Activities automated with network administration software include monitoring, archiving, and system checks. See daemon, dragon. Network Applications Consortium NAC. A trade organization seeking to support and promote generally accepted standards rather than a large number of fragmented proprietary standards for network applications in order to promote interoperability. http://www.netapps.org/ Network Control Protocols NCP. The Point-toPoint Protocol handles assignment and management of Internet Protocol (IP) addresses and other functions through a family of Network Control Protocols (NCPs) which manage the specific needs of their associated network-layer protocols. See Point-to-Point Protocol, RFC 1661. network drive A drive accessible to multiple users on a computer network. On some network systems, users have to specify and access a particular drive to take advantage of the shared storage space. On other systems, this shared arrangement can be set up so that it is transparent to the user and, in fact, a volume may traverse several drives. Network drives are sometimes set up to create data redundancy in case one of the drives or partitions is corrupted. This is a good idea and, since it is in constant effect, there is less chance of loss as with systems backed up only at intervals (although companies with important data should do both). See redundant array of inexpensive disks. Network Driver Interface Specification NDIS. A network protocol/driver interface jointly developed

by Microsoft Corporation and 3Com Corporation. NDIS provides a standard interface layer that receives information from network transport stacks and network adapter card software drivers. The transport protocols are thus hardware-independent. network element NE This is defined in the Telecommunications Act of 1996, and published by the Federal Communications Commission (FCC), as: “... a facility or equipment used in the provision of a telecommunications service. Such term also includes features, functions, and capabilities that are provided by means of such facility or equipment, including subscriber numbers, databases, signaling systems, and information sufficient for billing and collection or used in the transmission, routing, or other provision of a telecommunications service.” See Federal Communications Commission, Telecommunications Act of 1996. network fax server A workstation equipped with fax/modem hardware and software so multiple users of the network can route a fax in and out through the server. This removes the necessity for having a fax modem (or fax machine) physically attached to each computer in a network. The fax server can then also be located near its associated phone line, or lines. Fax servers also exist that can use Internet connections (T1, frame relay, etc.) rather than phone lines to send and receive messages. network filter A transducer designed to separate transmission waves on the basis of frequency. Network Information Service NIS. A client/server protocol developed by Sun Microsystems for distributing system configuration data among networked computers, formerly and informally known as Yellow Pages. NIS is licensed to other Unix vendors. network interface NI. A junction or reference point in a network that supports or represents a change in the physical and/or logical structure of a link or, in some cases, represents a jurisdictional change (even if there is no physical change or data conversion). The point at which a phone service line connects to a subscriber’s premises is a network interface and various aspects of this connection have been standardized. For example, the network interface electrical characteristics and interactions for an analog connection between a telecommunications carrier and the customer premises are described in ANSI T1.401-1993. network interface card, network interface controller NIC. A PC board that provides a means to physically and logically connect a computer to a network. For microcomputers, typically these cards are equipped with BNC and/or RJ-45 sockets facing the outside of the computer and edge card connectors that fit into the expansion slots inside a computer. The cables resemble video cables, or fat phone cables, depending upon the type used. Most systems require a physical terminator on the physical endpoints of the network (if the network isn’t working, it may be because termination is missing or incorrectly installed). Separate software, not included with

N

the computer operating system, may be required to use the specific card installed. Many workstationlevel computers come with network hardware and software built in, and Macintosh users are familiar with the built-in AppleTalk hardware and software. The trend is for microcomputers to use TCP/IP networking over Ethernet. Network Integration Verification Test NIVT. A test designed to evaluate and improve three different Front End Processors (FEPs) handling routing and transport protocols in mixed high-performance routing systems with large Topology Databases to assess scalability. Information on NIVT and actual test reports are available through the IBM Web site. network intrusion detection system NIDS. A means or set of procedures and/or programs designed to alert the system administrator or individual users about vandalistic attacks or unauthorized access to a computer network. There are many types of intrusion, including system flooding, account access, file access, and physical access. NIDS more often refers to the first three categories. (Physical access to the electronics inside a computer may be detected by video cameras, marks, fingerprints, or detection chemicals, but this type of intrusion is less prevalent than day-to-day attempts by unauthorized users to view, steal, or compromise data on a system.) An intrusion detection system is rarely just one application or device, but rather the implementation of a collection of policies, procedures, and tools to ensure system security. In general, NIDS refers to systems that actively detect signs of intrusion (e.g., a utility that detects repeated entries of incorrect passwords) as opposed to passive systems that primarily deter intrusion (e.g., the necessity for a password). As networks are increasingly connected to the Internet, they become more accessible to outside intruders. Electronic commerce sites on the Web are particularly vulnerable, as there are people who search for credit card numbers and other commodities that are recorded on computer systems. Two of the more important intrusion detection mechanisms include: monitors – These are applications that display realtime or recent statistics and events. On older systems and mainframes, monitors commonly represent data as text displays arranged in columns. On some of the newer systems, graphical tables and graphs are also available. System monitors are often bundled with operating systems to allow sysops to view CPU usage, connection requests, numbers of users, entries and exits to the system, locations of machines being accessed, numbers or types of packets being transferred, URLs of users accessing Web servers, etc. Operators use a combination of live audio/visual monitoring and software utilities to generate an alert when anomalous patterns occur. logs – These are records of activities. The data generated by monitors are often kept in running logs that can be archived indefinitely or stored for a period of hours or months, depending on the need. In addition to system monitors, software installation and system reconfiguration activities are

often logged to record when changes were made, which files were added or deleted, and where the files were installed. Intruders are not always hightech computer experts; often they are employees snooping or stealing data with little understanding of the electronic trail they leave when they engage in unauthorized access. Even if they do search for logs, with the intention of changing or deleting them, they may be unsuccessful if the system is configured to duplicate log entries on another computer or a protected directory. One of the more difficult types of intrusion to detect is access by someone who has stolen a legitimate password. Since the intruder isn’t breaking into the system, but logging on normally, the intrusion may go unnoticed for a long time. However, even this type of activity can sometimes be detected with a combination of monitors and logs. If CPU usage during the night or lunch hour is usually low, and the various monitors show John Doe’s account becomes active during times when John isn’t at his desk, there is reason to investigate the anomalous patterns. Intrusion detection systems are, in large part, dependent upon the ability of the system administrator and the capability of the system to determine normal usage patterns and variations from the norm. The most difficult type of intrusion to detect is unauthorized activity by a system administrator or programmer. A small percentage of sysops take advantage of their privileged positions for personal gain. Since a high-level administrator or systems programmer has access to almost everything on a network, it’s very difficult for others to detect tampering or unethical use of network resources. They are also expert at hiding a data trail when using one system to access another or when snooping on passwordprotected file systems. These types of intrusion often go unnoticed until funds disappear or until strange things happen after the individual leaves a project or firm. The primary ways to reduce system administrator intrusions are careful employee screening, built-in accountability policies and procedures, and good employee relations. For the most part, system administrators are intelligent, dedicated professionals, proud of their systems and concerned about maintaining good system security. Contrary to what might be expected, the majority of intrusions are probably not by system administrators, but by curious or mischievous programmers on the one hand and professionals trying to divert funds or information or save a buck on the other (statistics suggest that a surprising proportion of computer-related theft is by doctors and businesspeople as opposed to university students and teenagers). Network intrusion detection is not a simple configuration that can be set up and used indefinitely. Computer security requires a responsive approach to a dynamically changing environment, like a farmer adapting to constantly changing weather and market conditions. A system administrator must monitor, fine-tune, and reconfigure on an ongoing basis to achieve network security. See cracker, firewall, hacker, virus, worm.

O A symbol used on many consumer electronics devices to indicate “off.” On rocker switches, it indicates the side of the rocker which turns an appliance or component off. Its complement is “I” to designate “on.” O Series Recommendations A series of ITU-T recommendations providing guidelines for specifications of measuring equipment. These guidelines are available as publications from the ITU-T for purchase on the Net. Since ITU-T specifications and recommendations are widely followed by vendors in the telecommunications industry, those wanting to maximize interoperability with other systems need to be aware of the information disseminated by the ITU-T. A full list of general categories is listed in Appendix C and specific series topics are listed under individual entries in this dictionary, e.g., K Series Recommendations. See O Series Recommendations chart. O&M, O & M operations and maintenance. O/P output. O/R Originator/Recipient. A concept associated with the X.400 Message Handling System (MHS). The O/R address is used by the MTS for routing. The MTS.ORAddress is a set of structured and unstructured attribute value pairs which can be ASCIIencoded for interactions with gateways. (Thus, a text string form of O/R address has been specified by ISO.) The standard encoding of the MTS.ORAddress is a BNF representation. Each unstructured attribute has a key and a specified encoding. Each structured attribute has the X.400 attribute mapped onto one or more attribute value pairs. For domain-defined attributes, each element of the sequence is mapped onto a triple (a key and two values); each value has the same encoding. For RFC 822 routing to gateways, O/R address attributes are considered a hierarchy, and may be specified by the domain. Their order is: 1. country 2. Administrative Management Domain (ADMD) 3. Private Management Domain (PRMD) 4. organization 5. organizational unit (there may be more than one of these)

O

In cases where values are omitted, they are skipped. Null values are processed separately from omitted values (a domain cannot be null). As an example: /I=J/S=Doe/GQ=5/@Sales.GreatGoods.COM

is an encoded MTS.ORAddress which can be broken down right to left as follows: MTS.CountryName MTS.AdministrationDomainName MTS.OrganizationName MTS.OrganizationalUnitNames.value MTS.PersonalName.generation-qualifier MTS.PersonalName.surname

= “TC” = “BTT” = “GreatGoods” = “Sales” = “5” = “Doe”

MTS.PersonalName.initials

= “J”

OA See office automation. OAI See Open Application Interface. OALC4 A family of relatively small-diameter fiber optic submarine cables developed by Alcatel. These cables are specifically intended for repeater-equipped systems. They can house up to 16 optical fibers within a welded steel tube. A gel substance protects the fibers from moisture and hydrogen effects. A steel wire vault surrounded by a seam-welded copper tube provides additional protection. High-density polyethylene provides abrasion resistance. Cables of the OALC4 family are suitable for use at sea depths of between 0 and 7000 to 8000 m, depending upon the ohms per kilometer rating. OAM operations, administration, and maintenance. Various related management functions often associated with telephone and computer networks. In telephone networks, significant management and accounting tasks are associated with maintaining a dynamic environment in which subscribers all request different types and levels of service, and where the subscriber population is very mobile, thus changing their locations on a continual basis. Some systems have computer networks and entire facilities associated with just these aspects of the business. With mobile communications on the rise, these management tasks become even more intricate, and computer systems are used to facilitate the administrative tasks. OAM Operations And Maintenance. Preventive maintenance information which, in an ATM B-ISDN

O

ITU-T O Series Recommendations O.1

Scope and application of measurement equipment specifications covered in the O-series Recommendations O.3 Climatic conditions and relevant tests for measuring equipment O.6 1020-Hz reference test frequency O.9 Measuring arrangements to assess the degree of unbalance about Earth O.11 Maintenance access lines O.22 CCITT automatic transmission measuring and signaling testing equipment ATME No. 2 O.25 Semiautomatic in-circuit echo suppressor testing system (ESTS) O.27 In-station echo canceller test equipment O.31 Automatic measuring equipment for sound-program circuits O.32 Automatic measuring equipment for stereophonic pairs of sound-program circuits O.33 Automatic equipment for rapidly measuring stereophonic pairs and monophonic sound-program circuits, links, and connections O.41 Psophometer for use on telephone-type circuits O.42 Equipment to measure nonlinear distortion using the 4-tone intermodulation method O.51 Volume meters O.61 Simple equipment to measure interruptions on telephone-type circuits O.62 Sophisticated equipment to measure interruptions on telephone-type circuits O.71 Impulsive noise measuring equipment for telephone-type circuits O.72 Characteristics of an impulsive noise measuring instrument for wideband data transmissions O.81 Group-delay measuring equipment for telephone-type circuits O.82 Group-delay measuring equipment for the range of 5 to 600 kHz O.91 Phase jitter measuring equipment for telephone-type circuits O.95 Phase and amplitude hit counters for telephone-type circuits O.111 Frequency shift measuring equipment for use on carrier channels O.131 Quantizing distortion measuring equipment using a pseudo-random noise test signal

O.132 Quantizing distortion measuring equipment using a sinusoidal test signal O.133 Equipment for measuring the performance of PCM encoders and decoders O.150 General requirements for instrumentation for performance measurements on digital transmission equipment O.151 Error performance measuring equipment operating at the primary rate and above O.152 Error performance measuring equipment for bit rates of 64 Kbps and N x 64 Kbps O.153 Basic parameters for the measurement of error performance at bit rates below the primary rate O.161 In-service code violation monitors for digital systems O.162 Equipment to perform in-service monitoring on 2048-, 8448-, 34,368- and 139,264-Kbps signals O.163 Equipment to perform in-service monitoring on 1544-Kbps signals O.171 Timing jitter and wander measuring equipment for digital systems based upon the plesiochronous digital hierarchy (PDH) O.172 Jitter and wander measuring equipment for digital systems based upon the synchronous digital hierarchy (SDH) O.181 Equipment to assess error performance on STM-N interfaces O.191 Equipment to measure the cell transfer performance of ATM connections Supplements O.Sup3.1

O.Sup3.2 O.Sup3.3 O.Sup3.4

O.Sup3.6 O.Sup3.7

O.Sup3.8

Measuring instrument requirements – sinusoidal signal generators and level-measuring instruments Noise measuring instruments for telecommunication circuits Principal characteristics of volume indicators Consideration of interworking between different designs of apparatus for measuring quantizing distortion Crosstalk test device for carriertransmission on coaxial systems A measuring signal (multitone test signal) for fast measurement of amplitude and phase for telephone type circuits Guidelines concerning the measurement of jitter

environment, is included in the transmitted cells. OAM&P operation, administration, maintenance, and provisioning. OAM&P ANSI standards There are a number of important American National Standards (ANSI) of Committee T1 related to OAM&P, which are available from ANSI and described in the form of ab-

stracts on the Web. See the ANSI Standards OAM&P chart for examples. OAO orbiting astronomical observatory. Since 1966, a series of OAOs has been launched from Cape Canaveral to explore and measure astronomical phenomena that can more easily be seen from outside the Earth’s atmospheric envelope.

ANSI Standards OAM&P Abstracts ANSI Standard

ANSI Document Title

T1.118-1992

G Interface Specification for Use with the Telecommunications Management Network

T1.204-1997

Lower Layer Protocols for Telecommunications Management Network Interfaces, Q3 and X Interfaces

T1.208-1997

Upper Layer Protocols for Telecommunications Management Network, Q3 and X Interfaces

T1.209a-1995

Supplement – Network Tones and Announcements

T1.214-1990

A Generic Network Model for Interfaces between Operations Systems and Network Elements

T1.215-1994

Fault Management Messages for Interfaces between Operations Systems and Network Elements

T1.221-1995

In-Service, Nonintrusive Measurement Device Voice Service Measurements

T1.224-1992

Protocols for Interfaces between Operations Systems in Different Jurisdictions

T1.226-1992

Management of Functions for Signaling System No. 7 Network Interconnections

T1.227-1995

Extension to Generic Network Model for Interface between Operations Systems across Jurisdictional Boundaries to Support Fault Management

T1.228-1995

Services to Interfaces between Operations Systems across Jurisdictional Boundaries to Support Fault Management (Trouble Administration)

T1.229-1992

Performance Management Functional Area Services for Interfaces between Operations Systems and Network Elements

T1.233-1993

Security Framework for Telecommunications Management Network (TMN) Interfaces

T1.240-1996

Generic Network Information Model for Interfaces between Operations Systems and Network Elements

T1.243-1995

Baseline Security Requirements for the Telecommunications Management Network

T1.240-1996

Generic Network Information Model for Interfaces between Operations Systems and Network Elements

T1.244-1995

Interface Standards for Personal Communications Services (withdrawn)

T1.246-1995

Operations Systems across Jurisdictional Boundaries to Support Configuration Management – Customer Account Record Exchange

T1.247-1995

Performance Management Functional Area Services and Information Model for Interfaces between Operations Systems and Network Elements

T1.250-1996

Extension to Generic Network Information Model for Interfaces between Operations Systems and Network Elements to Support Configuration Management – Analog and Narrowband ISDN Customer Service Provisioning

T1.252-1996

Security for the Telecommunications Management Network Directory

O

OAS See Organization of American States. OBI See Open Buying on the Internet. object 1. A thing, article, entity, or unit of information. 2. An individually identifiable part, entity, or component. 3. In programming, an entity, often compartmentalized, that stores or receives data, e.g., a byte, block, register, segment, etc. 4. In the X Windows System, a software concept practically implemented as private data with private and public routines to operate on that data. 5. In typed objects, an entity that interacts as part of a defined operation. object, drag and drop In drag and drop or cut-andpaste operations, an object is an entity moved as a unit into another environment, window, or application, with a link retained to the original file location. Adjustments to the format of the information may be necessary and are handled by the drag and drop operation. object, programming In object-oriented programming, a reusable, modular, “wrapped up” collection of software characteristics, functions, and parameters at a basic level. For example, a button may be designed with certain visual and operational characteristics and stored for reuse in various applications, so that the code for the object isn’t constantly reinvented. An object may consist of a collection of other objects to serve some related or higher function. See class. Object Database Management Group ODMG. An independent standards organization now called the Object Data Management Group to reflect the broader efforts of the organization to support Universal Object Storage Specifications (UOSS). See CORBA. http://www.odmg.org/ Object Definition Alliance ODA. A vendor association established by Oracle which aims to promote and develop new interactive TV and other multimedia services and networks that will operate over a variety of platforms. ODA seeks to establish associated technical standards for these products. Vendors include a number of high-profile financial institutions and retailers, and computer and media developers including Time-Warner, Apple Computer, Xerox, and Compaq. See video-on-demand. object encapsulation A technique for combining related data and functions into an operational bundle, thus simplifying its use within a larger framework. The purpose is not to hide the intrinsic components of an encapsulated object, but to create a common superset of characteristics that work together and may be frequently used and reused. This technique is one type of modular approach to programming. See encapsulation, object-oriented programming. object inheritance A concept in object-oriented programming (OOP) which describes a hierarchical passing on of characteristics down through associated objects. Object Linking and Embedding OLE. A software system developed by Microsoft Corporation which allows various applications programs that are OLEcompatible to share and exchange information. It is an interoperability system that lowers the distinction

between various applications developed by different vendors so users can integrate the applications files and environments, and use them more as a suite of tools than as separate items. It further provides specification guidelines for the interface for accomplishing these tasks. OLE is a very good concept, in principle, and works well a lot of the time. Unfortunately, the various implementations are not yet perfect, as the OLE-compliant programs and OLE software programs installed on a system sometimes will clobber some of the other programs that don’t support OLE, causing odd behaviors and situations where software has to be reinstalled, or OLE disabled temporarily. As OLE-capability must be incorporated into each software application by individual developers, there is some variation as to the completeness and dependability of these implementations. When it works, OLE is a very good means to develop documents that take their various elements from a variety of text, image, sound, and other programs and combine them via links and drag and drop. Spreadsheet totals or statistics can be incorporated into stock offering documents, images can be incorporated into proposals, sounds can be incorporated into multimedia presentations, etc. without constantly opening and closing applications and converting various file formats with external utilities. OLE does more than just provide a means to insert information from one source into another; it further keeps a record of the links so that if the source information in one document is updated, it will also be updated in subsequently linked documents. OLE is used by various applications in Windows and Macintosh operating systems. See ActiveX. Object Management Architecture OMA. An architectural framework developed by the Object Management Group (OMG) to lower the complexity and cost of developing new software applications. See CORBA, Object Management Group. Object Management Architecture Board OMAB. A group established in 1996 by the Object Management Group (OMG) to oversee the OMG Technical Process, including the tracking and revision of technical specifications. See CORBA, Object Management Group. Object Management Group OMG. A nonprofit organization of over 800 software developers, vendors, and end users whose aim is to establish the widespread use of CORBA through global standard specifications. Headquartered in Massachusetts and established by eight companies in 1989, OMG promotes the theory and practice of object technology for the development of distributed computing systems through a common architectural framework. OMG seeks to establish industry guidelines and object management specifications to further the development of standardized object software, which it hopes will encourage a heterogenous computing environment across platforms and operating systems. See CORBA, Object Management Architecture, Unified Modeling Language. http://www.omg.org/ Object Request Broker ORB. The communications center of the Common Object Request Broker

Architecture (CORBA) standard developed by the Object Management Group (ORG). It provides an infrastructure for program objects to intercommunicate, independent of the techniques used to implement them and the platform on which the software is running. Compliance with the ORB provides portability over many different systems. The ORB administers objects so that an application need only request an object by name. There are now many commercial and freely distributable ORBs. See CORBA, Fnorb, Object Management Group, TAO. There is general information on CORBA at http://www.omg.org/ There is a good list of ORB resources on the Web at http://patriot.net/~tvalesky/freecorba.html Object Serialization Stream Protocol OSSP. A means to represent objects within a stream. Objects are grammatically represented and assigned a handle for use as a reference to the object. See byte-stream protocol, Java. Object Services Management components of the Common Object Request Broker Architecture (CORBA) standard developed by the Object Management Group (OMG). A set of services for facilitating development productivity and consistency of implementation. The Object Services provide generic environments for objects to perform their functions, interfaces for the creation of objects, control of access to the objects, and administration of the location of objects. See CORBA, Object Management Group. object-oriented programming OOP. A software development approach that follows a more natural and efficient evolution than many older reinvent-thewheel approaches to programming. To understand the difference between non-object-oriented programming and object-oriented programming in a simplistic way, imagine a toy shop in which each elf is working in a separate little room, each with a separate set of tools, creating some kind of toy doll. At the end of the day, the creations are brought into a central room and it is discovered that some toys have been duplicated, none have interchangeable parts, and the end result is only a half dozen different toys. That’s pretty much how traditional programming has been done, with an enormous amount of replication of effort. Every company writes the same sorting algorithms, there are hundreds of half-baked proprietary editors, and file search and retrieval methods are reinvented by thousands of programmers on a daily basis. It isn’t very efficient. It isn’t even very much fun. Now picture a toy shop in which some general guidelines are set out for joints and limbs, and in which each toymaker has a magic replicator in which his or her components can be copied an indefinite number of times. Now imagine one of the toymakers is a mechanical wizard, and another is an artist, able to make beautiful embellishments. At the end of the day, instead of having a dozen toys, a limitless number of heads and feet, bodies and legs can be shared

among all the toymakers. Not only that, but some particularly intricate mechanical parts and some wonderfully aesthetic ones can be used by all. Since guidelines were set out, the parts are interchangeable. The elves have created the basis for thousands of toys, rather than just a dozen. Assuming unlimited replication of individual parts is possible, there’s no limit to how often each component can be used. That’s what object-oriented programming is, in the ideal sense. Once you create an eye object and give it certain parameters so that the color, shape, and various eye characteristics (contact lenses, eyelashes, ability to track a moving shape, etc.) can be individualized, you don’t have to do it again; you can mix and match it with head, nose, and hair objects in thousands of different ways. Similarly, in programming it is possible to create directory, menu, window, and button objects. Objectoriented concepts are not limited to physical attributes; the software can also incorporate more abstract user security objects, sort or fetch objects, and functions and behavioral characteristics associated with a type or class of objects. Object-oriented programming is a modular approach that allows objects to be mixed and matched, or arranged in hierarchies, and customized to suit an individual application. Once created, they can be reused indefinitely. This can save development time and provides the basis for platform-independent software; it also gives a certain level of consistency to the interface, so users don’t have a high learning curve for interacting with new applications programs. It further provides the programmer with a number of levels of interaction with an object. The developer can use the object in a transparent way, with the definition of the object encapsulated (bound together as an attribute or functional unit) by passing messages and parameters without worrying about how it was coded, or the programmer can take apart the object and use its individual components, or combine it with others to create a larger functional unit. This too is different from traditional programming. In many cases using someone else’s non-object-oriented code involves a lot of study and adaptation to make it work in another setting, and it’s rarely easy to mix and match parts of the code so that the characteristics can be inherited among the different parts. In contrast, program objects can be designed so that their characteristics and behaviors are known, so they can be immediately used without a long ramp-up period or restructuring. Object-oriented programming languages are still evolving. Smalltalk is one of the first object-oriented programming environments, developed 20 years ago, but many common languages currently used in commercial software development are not object-oriented; efforts to create object-oriented versions of traditional languages have not been fully satisfactory. Nevertheless, the trend is toward object orientation, given its obvious advantages of portability and efficiency in many contexts. For important and interesting information on taking the object-oriented model to global implementation

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and distribution, see CORBA and Object Management Architecture. See Open Systems Interconnect, Smalltalk. OBRA See Omnibus Budget Reconciliation Act. OBS See optical burst switching. obscenity Obscenity, in its everyday sense, refers to actions or materials which are offensive, repellent, or vile. In a legal sense, it is more specific, as individual interpretations of what is offensive vary dramatically. Questions involving obscenity often conflict with individuals’ rights and opinions regarding freedom of speech, and thus are important issues on the global Internet. The Internet has evolved in a strongly tolerant and open advocation of people’s rights to their opinions. Much content on the Internet is frank, open, shocking to some, and more explicit than what people typically encounter when going about their daily work or shopping. See Communications Decency Act of 1996, Electronic Frontier Foundation. OC 1. operator centralization. 2. See optical carrier. OCC See Other Common Carrier. Occam’s Razor A maxim well known to scientists attributed to William of Occam in the 1300s that it is vain to do with more what can be done with fewer (or less). It has been restated in many ways, in many contexts, but essentially, in science and in human spheres of activity, the idea is that the simplest explanation or one which doesn’t require any additional hypotheses is usually the best, and often correct. OCIR overcoat-incident recording. OCP operator control panel. OCR 1. See optical character recognition. 2. Outgoing Call Restriction. octal A base eight numbering system utilizing the numerals 0 through 7. See decimal, hexadecimal. octathorp See octothorpe. octet A data unit very widely used in digital networks. An octet consists of eight data bits. octopus, hydra A visually descriptive name for a 25pair cable common in multiple phone system installations. At the far end, the 25-pair wire is organized into individual connectors (two, four, six, or eight wires) with phone cord connectors. An octopus is useful for stringing a single wire into a location where several phone connections are planned. octothorpe, octathorp The # symbol, sometimes also called pound, hash, crosshatch, or number sign. It is used as an end signal (or “long” signal) on some touchtone phone menu systems. It represents a number sign in financial contexts, a suite number in postal addresses, and the sharp sign in music notation. See pound. ODBC See Open Database Connectivity. ODC See Open Development Consortium. ODMG See Object Database Management Group. ODP open distributed processing. Odyssey A medium Earth orbit (MEO) satellite communications system which was intended to begin service in 1999 with 12 medium Earth orbit (MEO) satellites. Planned services included voice, data, fac-

simile, and Global Positioning Service (GPS). The project was discontinued in 1997 and TRW transferred technical expertise to the ICO Global Communications ICONET when it became a leading ICO shareholder later in 1997. TRW Inc. announced that it would turn back the license it had received for the Odyssey program to the U.S. Federal Communications Commission (FCC), in order to make the assigned frequencies available to other communications services. See ICO Global Communications. OEM original equipment manufacturer. A manufacturer who often supplies to other manufacturers or value-adding distributors. oersted (symb. – Oe, Ø) A centimeter-gram-second (CGS) unit of magnetic intensity (field strength) equal to the intensity of a magnetic field in a vacuum in which a unit magnetic pole experiences a mechanical force of one dyne in the direction of the field. It can be expressed as 103/4pA m-1. Named after Hans Christian Ørsted (sometimes transcribed as Oersted). See ampere. Oersted (Ørsted), Hans Christian (1777-1851) A Danish physicist and educator who demonstrated the effects of current on a magnetic needle to a class of physics students around 1819. He reported on the magnetic effects of electric currents, information that brought together magnetism and electricity as never before, and resulted in a change in scientific thinking and the development of electric telegraphs in Europe and America. The oersted unit of magnetic intensity is named after him. OFDM See orthogonal frequency division multiplex. off-hook On a phone set, the state of having the plunger or switch-hook in the active or “up” position so the circuit is connected. The term comes from the old wall phones on which the earpiece (receiver) was taken off a curved hook when in use (and when the battery power was engaged). When the phone is first taken off-hook, it alerts the switching exchange to the fact that the caller wants to use a line. The switching exchange returns a dial tone to the caller to indicate that the line is available for dialing. See on-hook. off hours The times outside normal operating or working hours. Telephone and Internet services are often discounted in off hours or off-peak hours. off-peak hours Hours of low usage. In telephony, the hours between 11:00 pm and 7:00 am are designated as off-peak in many areas, and calling rates are lower. The concept also applies to transportation systems, and fewer buses, trains, or subway cars may be in service during these hours. off the shelf Products and services that are ready to use without any customization. Products which can be readily purchased by anyone walking into a store or ordering from a catalog, and run with little or no configuration. Essentially the same as shrinkwrapped products. office automation A catchall term for procedures and systems that are designed to streamline or increase the efficiency of the operations of a business,

often through the installment of technology which may or may not displace human workers. In some respects office automation has freed people from drudge work; it is no longer necessary to have rooms full of “human calculators” sitting and working out sums by hand, but the introduction of technology has also introduced greater needs for training, storage of information, information retrieval, and other timeconsuming activities that don’t necessarily improve quality of life or shorten the work day. Office of Science and Technology Policy OSTP. The science policy coordinating group for the Federal Government Executive Branch. The OSTP is led by presidentially appointed directors, and is organized into four divisions: environment, national security and international affairs, science, and technology. The OSTP provides expert advice to the President of the United States in matters of science and technology. http://www.whitehouse.gov/WH/ EOP/OSTP/html/OSTP_Info.html Office of Telecommunications Along with the Office of Telecommunications Policy, this organization was rolled into the U.S. National Telecommunications and Information Administration in 1978 as a result of a reorganization. Office of Telecommunications Policy OTP. Office of the Director of Telecommunications Regulation ODTR. The National Regulatory Authority for telecommunications in Ireland, established June 1997 under the Telecommunications Miscellaneous Provision Act 1996. The ODTR administers the development of a liberal telecom market in accordance with the European Union and Irish law, allocates radio spectrum, and regulates broadcast transmissions and telecommunications equipment. OFX See Open Financial Exchange. OGT outgoing trunk. ohm A practical unit in the meter-kilogram-second (MKS) system equal to the resistance of a circuit in which a potential difference of 1V produces a 1A current. Thus, if the values of two of these three are known, the third can be calculated. Named after Georg Simon Ohm. In 1908 the International Congress established the International ohm as the resistance offered to an unvarying current by a column of mercury at 0°C, 106.3 cm long, of a constant crosssectional area of 1 square mm, and weighing 14.4521 g. In the U.S. in 1950, Congress defined the ohm as equal to one thousand million units (109) of resistance. See ampere, electromotive force, Ohm’s law, resistance, volt. Ohm, Georg Simon (1787-1854) A German physicist who, in 1820, investigated the conducting properties of various materials. He described the flow of electricity through a conductor and discovered the relationships among current, resistance, and electromotive force, information that greatly influenced subsequent theory and application in electricity. See Ohm’s law. Ohm’s law In any specific direct current electrical circuit, the strength of the current is directly proportional to the potential difference in the circuit and

inversely proportional to the resistance. Thus, current (in amperes) equals electromotive force (in volts) divided by resistance (in ohms), or I = E/R. See ampere, ohm, resistance, volt. OHR See optical handwriting recognition. OLE See Object Linking and Embedding. OLIU Optical Line Interface Unit. OLNS Originating Line Number Screening. OLT optical line termination. OM Operational Measurement OMA See Object Management Architecture. OMAT Operational Measurement and Analysis Tool. OMG See Object Management Group. Omnibus Budget Reconciliation Act OBRA. OBRA is a 1993 U.S. Congress amendment to the Communications Act of 1932 which preempts state jurisdiction in such a way that individual states no longer regulate rates and entry by companies offering wireless services. The federally controlled spectrum was transferred to the Federal Communications Commission (FCC). It further organized wireless into two categories: commercial mobile radio services (CMRS), including cellular radio services and personal communications services (PCS), and private mobile radio services (PMRS), including public safety and government services. See Telecommunications Act of 1932. omnidirectional Effective in all directions, radiating in all directions, or receiving from all directions. Functional in many directions without preference to any one. An omnidirectional antenna is one which is designed to send or receive signals in a maximum number of directions. A theoretical isotropic antenna is fully omnidirectional and often used as a reference for comparing antenna patterns or effectiveness. An omnidirectional speaker directs sound in all directions. Since this is structurally difficult to achieve, the speaker is usually a collection of speakers pointing in many directions, housed in one cabinet. omnidirectional antenna An antenna designed to transceive signals through a wide range of directions. Since an antenna’s capabilities are determined by shape and location, it is rarely completely omnidirectional, but broad omnidirectionality is achieved by maintaining equal field strength through the horizontal plane, and radiating in or out through the vertical plane. See isotropic, omnidirectional. omnidirectional microphone A microphone designed to capture sound from all around its location. This is actually less common than directional microphones. Tape players, camcorders, digitizing sound sample microphones, phoneset microphones, and others have directional microphones to zero in on the crucial input, so they can screen out extraneous noises and conversations. Omnidirectional microphones can be said to capture sound “environments.” OmniWeb One of the earliest commercial Web Browsers, OmniWeb 1.0 was released in March 1995 for NeXTStep platforms by Lighthouse Design, Ltd. In spite of being a first release, it was a well-designed, full-featured browser, utilizing the Display

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PostScript and object-oriented capabilities of NeXTStep. It had flexible bookmark and other accessory capabilities not available in other popular browsers until about a year later. OmniWeb was subsequently ported to run on Macintosh Systems by The Omni Group and continues to be enhanced to take advantage of evolutionary changes in HTML and related Web languages. on-hook On a phone set, the state of having the plunger or switch-hook in the inactive, depressed, or “down” position to interrupt the circuit, so it is not active while the phone is not being used. The term comes from the old wall phones on which the earpiece (receiver) was cradled on a curved hook when not in use (to conserve battery power). See off-hook. on-line See online. on/off keying A type of modulation scheme similar to frequency shift keying (FSK), except that no signal is used for binary “0” (zero). See frequency shift keying, phase shift keying. on-ramp colloq. Access to a main communications link, such as highway, phone trunk, or networking service. The on-ramp is the link between the user’s system and the main system. An Internet Access Provider (IAP) can be considered an Internet on-ramp. ONA See Open Network Architecture. ONAC Operations Network Administration Center. ONAL Off Network Access Line. online 1. Having access to a system which is at least minimally functioning, and is largely automated. Interacting with a proceduralized system. A user is said to be online when he or she logs into a computer or a network, or accesses an automated phone system. 2. To bring a system online is to connect or power it up so that it is at least minimally functioning. 3. To bring an employee online refers to fitting the person into an organizational structure within an established system of priorities and procedures. Online Public Access Catalog OPAC. An online service for providing access to bibliographic records. OPAC can be used to search records based upon author, title, subject, title keywords, and other search criteria. Many libraries worldwide offer access to OPAC through Telnet, Web interfaces, or internal Libsys systems. Similar to OPAC is the British Library Public Catalogue (BLPC); COPAC is a publicly accessible catalog from 20 of the largest research libraries in Ireland and the U.K. who are members of the Consortium of University Research Libraries (CURL). ONT optical network terminal/termination. ONU optical network unit. OOP See object-oriented programming. OPAC 1. See Online Public Access Catalog 2. See outside plant access cabinet. open 1. Unbounded, having no barriers or extents, unconcealed, exposed, uncovered. 2. An open circuit is one which is not currently connected, usually because no power is coming to it (as when it is turned off). A circuit breaker or blown fuse may create an open circuit. 3. An open transmission channel is one

that is not currently in use, so may be available. An open channel may also imply one that is unsecured, where others can hear any communication that occurs. Open 56k Forum A consortium of telecommunications vendors promoting K56flex modem technology. open air transmission A type of transmission which either depends on air for the propagation of the signals or which is commonly broadcast through the air. Radio, shortwave, and microwave transmissions are primarily open air systems. open applications interface OAI. An interface built into a system and documented in such a way that third-party vendors can develop equipment and software applications that tie into that system. Open Buying on the Internet OBI. An open, vendor-neutral, scalable, securable, business-to-business standards effort for the support of electronic commerce. The effort was initiated by a round-table dialogue by a number of Fortune 500 companies in October 1996. The founding participants included prominent firms such as American Express, BASF Corporation, Ford Motor Company, and others. The goal was the quick and effective implementation of interoperable Internet-based e-commerce solutions amenable to universal, high-speed access and paperless transactions. In June 1998, CommerceNet assumed management of the OBI Consortium to facilitate standardization efforts. The OBI specification supports purchasing solutions for procuring high-volume, low-dollar, indirect products and services. OBI was first publicly demonstrated through the OBI Interoperability Showcase at the CommerceNet 99 conference. The first version of OBI was released in March 1997, with V2.1 released in November 1999. Open Buying on the Internet Consortium OBI Consortium. An independent nonprofit organization dedicated to the development of open standards for business-to-business Internet commerce. http://www.openbuy.org/ Open Collaboration Environment OCE. An environment created by Apple Computer which provides a means for third-party developers to create telecommunications applications that interface with the Macintosh operating system (MacOS). Thus, developers can create Internet phone, facsimile, network, and other telecommunications-related products for Macintosh owners. Open Database Connectivity ODC. Microsoft’s telephony software open application processing interface (API), part of a system that provides interoperability between Microsoft business-oriented database, spreadsheet, and word processing software, which is especially useful for digital telephony applications. The interface itself is independent of the application that provides the formatted data. In this way, call records and statistics can be stored and manipulated with popular software applications, providing computer-telephone integration and advanced call-recording capabilities.

Open Development Consortium ODC. An administrative concept introduced in November 2000 and formed early in 2001 to promote open standards for effective and collaborative exchange of development information. The consortium evolved out of ODC discussion list messages supporting informational concepts related to open development and open source software. Open Financial Exchange OFX. A specification for the electronic exchange of financial data among businesses, consumers, and financial institutions over the Internet. The specification was jointly developed by CheckFree, Intuit, and Microsoft in 1997. The specification supports a wide variety of types of financial transactions including bill presentation and payment, banking, investment and stock tracking, pension account inquiries, and more. In 2000, the OFX specification was made XML 1.0compliant and certain tax form capabilities were added. A number of development toolkits are available for creating OFX-compliant applications, including JOFX (Java OFX). By late 2001, OFX was supported by more than 1400 payroll processing, brokerage, and banking firms. See JOFX. http://www.ofx.net/ Open Group, The Formerly the Open Software Foundation, The Open Group is an organization which aids in the development and implementation of secure and reliable network infrastructures. The Open Brand is a registration mark (X) awarded by The Open Group to products which conform to the standard specifications. http://www.opengroup.org/ Open Network Architecture ONA. A system developed to encourage third-party vendors to supply public phone network products and services. Under the Federal Communication Commission’s (FCC’s) ONA, the telephone companies must provide the same service guarantees and levels to outside vendors’ products that use the phone lines, as they use themselves. Network services must be stipulated as individual services in order to make them available to unaffiliated Internet Service Providers (ISPs). The Bell Operating Companies are required to comply with ONA. Open Systems Networking Initiative OSN. A trade organization promoting and supporting open network technologies such as high-capacity storage solutions for enterprise-level systems. The organization was founded by Cisco Systems, Quantum Corporation, and others. The OSN architecture is intended to facilitate the interoperability and accessibility of data via industry-standard networks. open office An administrative and physical structure in which low walls or no walls are favored over high walls, movable walls are favored over fixed walls, and work stations are generally within view of more administrators and employees than in other office designs. Open office concepts are designed to promote flexibility and communication. open skies colloq. Regulatory policies that are liberal enough to allow private use. Prior to 1972, the Federal Communications Commission (FCC) did not

permit private American satellites to be launched for commercial communications. It then opened the doors on private domestic satellite launchings and operations, a move that created an opportunity for new competitive services to be established. MCI is one of the companies that got its start partly through recognizing and taking advantage of the opportunities presented by these openings. Open Software Foundation OSF. This has now become the Open Group. See Open Group. http://www.opengroup.org/ open-space cutout In telephone wiring, a protective grounding mechanism, often used in conjunction with fuses and heat coils to guard against possible danger to people and equipment from large power fluctuations. If voltage is too high, the wire grounds by arcing across a small air gap between carbon blocks mounted on an insulator such as porcelain. open system An open computer system is one which has few security barriers. Passwords may not be needed or individual users’ directories may be open to all users. In many ways the Unix operating system and the Internet global network have been developed with an effort to keep them open and accessible; some people advocate that all systems should be that way. Open Systems Interconnection OSI. An important layered architecture specification released as a standard by the International Organization for Standardization (ISO). OSI is designed to facilitate communications development between computer equipment and network software. Many vendors have opted to support this standard. Essentially, the communication is mapped onto seven layers as shown in the ISO/ Open Systems Interconnection Reference Models chart. See ISO/OSI Reference Model for more information. Open Trading Protocol OTP. See Internet Open Trading Protocol. Open Video System OVS. A regulatory distinction for video services carried by Local Exchange Carriers (LECs), for example, who are not recognized as local cable service providers per Federal Communications Commission (FCC) guidelines and regulations. Thus, a local exchange carrier (LEC) could become an OVS operator, but was also required to provide nondiscriminatory access on a portion of its channel capacity to unaffiliated program providers. By 2000, 25 OVS operators had been certified to serve 50 areas. The mid-1990s was an important time during which technological advances made it possible for a wider range of types of providers to offer a broader range of telephony and cable programming options to their subscribers. In addition to this, the Telecommunications Act of 1996 opened the doors for telcos to offer video through phone lines, to seek cable franchises, or to develop wireless cable systems. Together, these conditions resulted in blurred distinctions between cable and telephone companies since many services were now being offered over the same media. Thus, regulatory authorities were asked to

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clarify some of the issues and the FCC Cable Services Bureau became involved in this process. On the other side of the equation, in 1996 the cable providers expressed concerns about telcos not being regulated in the same way as cable companies were by the Cable Act. Organizations such as the National Cable Telecommunications Association argued that the FCC exceeded its authority by preventing cable operators from switching to become Open Video Systems (OVS) providers, as defined by the FCC.

In January 2001, the FCC presented its seventh Annual Report on competition in the video markets. The document confirmed that cable TV was still the dominant video delivery technology, but with a declining market share of a couple of percentage points per year. Cable service rates increased slightly more than the rate of inflation in general over the study period. Interestingly, it was found that few telephone companies had sought OVS certification since 1996. See Telecommunications Act of 1996, Video Dial Tone.

ISO/Open Systems Interconnection (OSI) Reference Model From bottom to top, seven layers have been defined for OSI, ranging from physical and data layers through presentation and applications layers, thus following a low-level to high-level arrangement common in many computer architecture models. The selection of the layers was based on subdivisions chosen to distinguish well-defined functions and various levels of abstraction. In general, layers are related to services provided by the layers below. In actual implementations, the situation is a little more complex and many variations with sublayers or lesser-used layers exist. Layer Funct.

Number

Purpose, Implementation

Application

Layer 7

User interfaces, applications programs, emulation, and other higher-level software implementations.

Presentation

Layer 6

Character sets, text handling. Data conversion into standard formats for transmission over a network or conversion from the transmitted format to something that user applications can understand. Encryption and other means of data security are also handled at this layer.

Session

Layer 5

Connection and session mechanisms for facilitating intercommunication between networks. File transfers, program sharing, data sharing, and basic traffic direction are managed at this layer to provide an orderly exchange of information (e.g., management of simultaneous requests from different users that might affect data integrity).

Transport

Layer 4

Process-to-process communications, addressing, and a number of endto-end services. The data are packaged into packets in preparation for transmission. Identification is added so that disassembled packets that may travel different routes can be reassembled at the destination. Local network addresses may be defined at this layer. Error handling not already managed by lower levels may be handled here with respect to reliability and data integrity.

Network

Layer 3

Host-to-host communications and basic transfer units (packets), network addressing, forwarding, and routing. Addresses may be provided by the Network Layer to the Transport Layer.

Data Link

Layer 2

Activation, handshaking, interfacing, and other basic communications intended to initiate, regulate, and terminate a communications session. Common functions at this level include the management of wired connections (modems, Ethernet, etc.) or wireless transmissions, although the actual physical medium used is handled by the Physical Layer transparently to the Data Link Layer. Low-level error handling, data synchronization, and flow control are managed at this layer.

Physical

Layer 1

The transmission medium, electromagnetic properties, and other physical aspects associated with getting the signal from one place to another such as cables, devices, buses, signaing, etc. The physical layer is independent of the actual medium used and thus the layer model applies equally to electrical voltages in wired lines, radio waves in wireless transmissions, and laser light beams in fiber optic cables.

operand A quantity or information which is being manipulated. For example, in mathematics, if you divide 200 by 10, then 200 is the operand. In computer algorithms, data, or the address of the data to be operated upon, are passed to an instruction in order for the instruction to act upon the data. operating environment This has two meanings, depending upon the context. It is used in a limiting context to describe an operating system which isn’t fully integrated or fully multitasking. It may be taskswitching, or it may have a graphical user interface on top of a text-based operating system not fully implemented as multitasking. Many vendors have claimed multitasking operating systems which were not really so. In its second, broader context, it refers to the environment surrounding an operating system, that is, the system, the software that runs it, the peripherals and applications that support it, etc. An operating environment, in this broad sense, may encompass more than one operating system. operating system OS. The most important software on a computer is that which lies between the user applications and the hardware. It’s not possible to control the CPU, manage memory, access a disk drive, send images to a monitor, or transmit data through a network connection or modem without an operating system. The operating system handles interrupts, timing, the movement of data from one register to another, and all the nitty-gritty operations that are typically not seen or understood on a technical level by most users. Microcomputer operating systems began to be developed in the 1970s. The early ones were text-based. One of the first widely used, popular operating systems was CP/M, designed by Gary Kildall. CP/M was the forerunner of QDOS, and hence, MS-DOS, and the syntax and commands are very similar. LDOS, TRS-DOS, UltraDOS, and other TRS-80 operating systems shared many common properties with CP/M. Kildall also later designed a multitasking operating system and a graphical user environment (GEM). In the early 1980s, Apple created proprietary operating systems for their Apple and Macintosh lines of computers, featuring the first widely distributed graphical operating system descended from pioneering work at Xerox PARC. This concept was so successful that it has since been adapted by virtually all subsequent vendors, including Atari, Commodore Amiga, Apollo, Sun Microsystems, Microsoft, SGI, The X Windows System, and NeXT. It’s difficult to find a computer now that doesn’t have a graphical user interface on top of, or in conjunction with a text operating system, or which is fundamentally a graphical operating system. The various versions of Windows are popular on consumer-level, Intel-based systems. A number of multitasking systems were developed in the late 1970s and early 1980s, but the first widely distributed commercially successful preemptive multitasking operating system on a microcomputer was AmigaOS, introduced in 1985. Most of the workstation level computers had multitasking operating

systems by the early or mid-1980s, and the other vendors began to follow this lead in the late 1980s, most notably OS/2 (Operating System 2), originally developed jointly by IBM and Microsoft. Many other operating systems released around this time were task-switching rather than fully multitasking. Microsoft Windows has since become widespread on personal computers, with Windows NT, originating out of the OS/2 collaboration, used on many server systems. Unix is one of the most robust, earliest, and most important operating systems. A high proportion of institutional computing operations, much scientific research, and many Internet hosts run on Unix systems. Unix is freely distributable, powerful, flexible, dependable, well-supported, and runs on most computers. Linux is a popular implementation of Unix (as is BSD), available from a number of commercial and free distribution sources. Along with Apache, a freely distributable server software, Unix/Apache systems are used by thousands of Internet Services Providers to provide gateways to the Internet through the Web. An operating system runs a computer, and computers are increasingly delegated control tasks beyond those humans can handle alone or in cooperation with one another. Navigational aids on aircraft are a good example. Fighter jets traveling at hundreds of miles per hour move too quickly for the human nervous system to react in time to control every aspect of the plane’s behavior, so computerized systems handle many functions on the pilot’s behalf. Extrapolate that type of control to appliances, houses, security systems, currency exchange, intelligent vehicle systems, and every aspect of human society that will someday be controlled by computers through a 24-hour Internet connection to all the other computers in the world. Given this broader outlook on our probable future, the importance of carefully choosing a reliable operating system cannot be overemphasized. Buying the cheapest system or the most popular system, or passively allowing the choices to be made by profit-based corporations is, in the long run, a more far-reaching decision than selecting a President or other political leader. Why? Because a President who does a bad job can be voted out. An operating system that does a bad job cannot be disabled if it has been delegated important tasks such as running medical equipment, automated transportations systems, or environmental controls. Once a fighter plane has been designed with a dependency upon computer control, you can’t just turn off the software in midflight. Similarly, if 5 or 10 years from now a family’s financial transactions, medical prescriptions, education, and travel arrangements are handled by a computer operating system through the Internet, it may no longer be possible to turn off the computer at will. That bears thought and forethought and suggests that open source operating systems coexisting with commercial products can help maintain balance. See BSD, Linux, Mac OS X, Microsoft Windows, NeXTStep, OS/2, Solaris, SunOS, Unix, UNIX. operational load 1. The full power requirement of

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a facility, which may be expressed in terms of averages or maximums. 2. The administrative and personnel requirements of an organization when in full operation. operator An individual with system access privileges hierarchically higher or more powerful than general users. A telephone operator can manage calls and access services and control mechanisms that are not accessible by regular phone subscribers. A chat room operator can include or exclude specific users or set other restrictions or standards of use. A system operator has access to monitors, security devices, software programs, and other computer operations mechanisms not available to regular users.

Historic telephone switchboards. Top: A telephone operator staffing the first switchboard in Idaho Springs, Colorado, wearing a headset. Bottom: The Mountain States Telephone and Telegraph switchboard office in Grand Junction, Colorado, 1903. [Denver Public Library Collection; copyrights expired by date.]

operator, telephone An individual who handles the routing of calls from callers to callees and provides a variety of types of assistance such as directory assistance, long-distance procedures, billing options, etc. Many of these processes have now been automated, but in the early days, the telephone operator had complete responsibility for connecting, monitoring, and disconnecting calls through manual patchcords. He or she was also implicitly expected to provide emotional support, emergency information, local news and gossip, and business tips. In fact, the position of the phone operator included so much

power (over connections to alternate business options) and information that a direct dial system was invented expressly to bypass the operator! Later switchboard systems required a higher level of concentration and expertise as many more lines would be serviced and the switchboards included lights to indicate connections and incoming calls, switches, cards for recording toll calls, and more. While the names of the very first telephone operators have probably been lost to history, George Willard Coy is generally credited as the first telephone operator and Emma Nutt as the first female telephone operator. Nutt was instated following the relative failure of male telegraph operators to adapt to the task of courteously handling customer voice calls. Nutt apparently moved from a telegraph office to the phone exchange in Boston, hired in September 1878 by A. Graham Bell. She was paid a salary of $10 per month for a 54-hour work week (minus lunch). This was a year of great expansion, during which the New England Telephone Company was formed to sell licenses to telephone company operators in the New England area. Ms. Nutt apparently could remember every number in the directory. Preferred Voice has created a synthesized voice speech attendant for delivery of information services named EMMA in honor of Ms. Nutt. Records are spotty, but a small selection of notable first telephone operators for their regions prior to about 1913 is shown in the Selection of Pioneering “First” Telephone Operators chart. See Call Girls, Strowger switch, switchboard, telephone history. operator-assisted call Any phone call in which the caller contacts the operator to handle some part of the transaction or connection, rather than direct dialing. There are usually surcharges associated with operator-assisted calls. operator console, computer In computer networks, a console is a computer terminal which allows access to management and administrative functions that monitor and control the network. Common operations carried out on the console include user password assignments, new user account allocations, virtual configuration of devices and the network topology, server configuration, etc. Often the operator console is in a separate room for security reasons and, at the very least, is password protected to prevent unauthorized users, or well-meaning but uninformed users from accessing lower level system functions that could interrupt the functioning of the network. operator console, phone In telephony, the main console of a multiline phone system. The operator console often is programmable and may include a handsfree earphone set. Operator Service Provider OSP. Previously called Alternate Operator Services. A competitive provider of operator-assisted long-distance calls, especially third-party billing, collect, etc., which usually leases the services of existing phone networks. Large hotels sometimes provide AOS services to hotel guests for a premium. See splashing. OPRE Operations Order Review.

Ops Abbreviation for operations, operators, operator services, and system operators. This is a particularly common abbreviation on Internet chat systems, where the operators (ops) or channel operators (chops, chanops) enforce accepted behavior on chat

channels. See operator. OPS off-premises station. optical amplifier A type of device used as a cable repeater on fiber optic transmission lines, which functions without converting the optical signal. Early

A Selection of Pioneering “First” Telephone Operators Name

Location

George Willard Coy Emma N. Nutt ___? Lajeunesse T.A. “Tom” LePatourel

New Haven, Connecticut 1878 (switchboard inventor/op.) Telephone Despatch Co., Boston 1878 (first female operator) Vankleek Hill, Ontario ? Burlington, Ontario late 1880s (when LePatourel moved the exchange to Brant St., Pansy Smith took over as operator) Trimble County, Kentucky ? Bayreuth, Germany 1891 Edmonton, Alberta 1892 Cuba, Illinois ? Tuolumne County ca. early 1890s New Haven? ? Harlan County, Kentucky (later bought out by the Bell Company) Brockton ? Shaner’s Corners, Oklahoma ? Odessa, Texas late 1800s? Montello, Wisconsin late 1800s? Paxico, Kansas late 1800s? Laconia, New Hampshire late 1800s Idaho Springs, Colorado 1898 Hico, Texas 1900 Victoria, Illinois ca. 1900s Rockville, Pennsylvania early 1900s Preston early 1900s Urbana, Illinois early 1900s Luce, Nebraska early 1900s Valentine, Nebraska ? Gunnison, Colorado ? Monroe City, Missouri ? La Grande, Oregon ca. 1902 Chincoteague, Virginia 1902 Lost Nation, Ontario ca. 1902 Sequim, Washington 1903 Bellwood, Nebraska 1904 Frontier, Michigan 1906 Licking, Texas ca. 1906 Vernal, Utah 1907 Lakeland, ? 1908 Parsons, ? ? St. John, North Dakota ca. early 1900s Pacific Grove, California ? Murfreesboro ? Elk Point, Alberta 1913 Arbon Valley, Idaho 1913

Effie Joyce Mosley ? Jennie Lauder Mable Mowery Campbell? John M. Curtin George Coy Lindy Blair Johnson Mrs. Bill Jenks Bessie McArdle Edna Gielding Mrs. Jason Daniels Esther C. W. Webb Angie Champlin Anna McKinley? Stella Dunigan Sarah Gothard Eliza Woods Mabel Chatterton Mary Moore ___? Fox Clara Collett Jennie Dofflemyer Lenna Evans Lear Mae Robinson West Retta Smith R.M. Gable Mary Priest Stone Frank Selzer Sto Devine Tennie Dorsey Wilson Essie A. Christie Neal Jennie Nelson Maude Arnold Octavie Croteau Winifred Tuttle Clois Futrell Charles Hood Susanna Evans

Approx. date

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versions were based on semiconductor lasers. Most are now erbium-doped fiber amplifiers (EDFAs), that is, directly doped silica fibers, with the principal parameters defined by atomic composition. optical burst switching OBS. A mechanism proposed in 1999 by Chunming Qiao and Myungsik Yoo for managing bursty network traffic on the Internet. The research, supported in part by a National Science Foundation (NSF) grant, is intended to streamline network switching in anticipation of high-speed endto-end optical networks of the future. The system combines aspects of optical circuit switching and packet/cell switching. While transition technologies are expected to combine optical networks with electrical switching, at some point there may be second generation all-optical networks that can be established as a layer beneath Internet Protocol (IP). OBS anticipates this evolution in technology. Many broadband transmissions are inherently bursty (e.g., multimedia), as apparently are large numbers of self-similar traffic streams. Thus, a system more efficient for this situation than optical circuit switching was sought. The researchers have observed that a packet can be sent along with the header, to reduce setup time and overhead, but that this approach has limitations as well. In OBS, a control packet is transmitted to set up a connection, followed by a data burst before the connection acknowledgment is received, essentially a one-way reservation system. In addition, data burst buffering at intermediate nodes is eliminated, reducing the wait for processing of control packets. Signaling is out-of-band. See Just-EnoughTime, Optical-Label Switching. optical bypass In a Fiber Distributed Data Interface (FDDI) token-passing network, port adaptors can be equipped with optical bypass switches to avoid segmentation which might occur if there is a failure in the system and a station is temporarily eliminated. Normally, optical signals pass through the bypass switch uninterrupted, but if a station fails and is eliminated from the ring, the optical bypass can reroute the signal back onto a ring before the signal reaches the failed station, thus providing fault tolerance

for the system. The optical bypass switch is attached to the FDDI port adaptors between the attachment station and token-passing ring. See A port, dual attachment station. optical carrier OC. A series of optical network transport levels defined in conjunction with SONET. See SONET Optical Carrier Transport Levels chart. optical character recognition OCR. A software process, or combination of hardware scanning devices and software, which evaluates marks on a page and determines whether they have the predefined characteristics of text, symbols, and images, depending upon the software. Most OCR programs use a combination of intelligent algorithms and character tables to process marks. These marks are typically text and character symbols, although some programs will also recognize mathematical and logical symbols if these are added to the program dictionary or the user dictionary. Some programs can automatically discern columns of text and images, and divide the page up appropriately, handling the regions separately. Once the document has been “recognized,” the characters and symbols are converted to a common format, such as ASCII or one of the many flavors of extended ASCII, and stored as a file that can be further edited with a text editor, word processor, or desktop publishing program. In its strictest sense, OCR just recognizes the characters; software which handles images as well is called optical document recognition. However, most OCR applications these days have some document processing and image recognition functions, so the phrase is used broadly here. Most of the early work on pattern matching algorithms used in character recognition was done in the late 1950s and the early 1960s. By 1963, IBM had a system that could recognize Roman and Cyrillic characters at the rate of about 50 words per minute, the speed of a moderately competent typist, and faster than most typists can type information with many numerals. See optical document recognition, scanner. optical computer A type of processing hardware

SONET Optical Carrier (OC-) Transport Levels Carrier OC-1 OC-3 OC-9 OC-12 OC-18 OC-24 OC-36 OC-48 OC-96 OC-192

Rate (Mbps) 51.84 155.52 466.56 622.08 933.12 1244.16 1866.24 2488.32 4976.64 9953.28

DS-3

DS-1

DS-0

1 3 9 12 18 24 36 48 96 192

28 84 252 336 504 672 1008 1344 2688 5376

672 2016 6048 8064 12096 16128 24192 32256 64512 129024

based on photons rather than electrons. This is a more experimental technology than is used with traditional computers, but it has possible advantages, particularly in speed and resistance to interference over current technologies, and may become more prevalent in the future. optical connectors Connectors specially designed to couple fiber optic cable junctions so they interfere as little as possible with the path of the optical beams passing through the connectors. The connectors are usually used at points where the fibers connect with routing or switching circuitry, or with the optical interface to the system itself. Optical connections have to be well-engineered, as they must handle very precise beams and paths, and often must maintain the proximity and orientation of a bundle of optical fibers. Connectors for blown fiber installations are easier to install and maintain than a number of other types of fiber attachments. See blown fiber. optical cross connect OXC. Optical connection components of telecommunications carrier networks that help operators manage the larger amounts of bandwidth enabled by newer capacity-increasing technologies. OXCs began to become generally available in the late 1990s. OXCs can facilitate network administration by enabling a network to be more readily reconfigured or restored using optical switches. OXCs can handle data streams in the terabit ranges and work with a range of wavelengths and bit rates, making it easier to quickly effect rerouting. Currently OXC components are part of the optical portion of mixed wire and optical fiber networks, but as the optical market grows, demand for OXCs will likely increase. See lambda switching. optical detector A substance or circuit which detects and converts electromagnetic waves in the form of optical waves. Solar panels contain substances that allow the conversion of light into electricity, which are widely used in the satellite industry to provide power for telemetry adjustment of orbits. See solar panel. optical disc Any of a number of technologies used to store digital data which is subsequently accessed by light, usually a laser beam pickup. The information on an optical disc is commonly stored in a series of pits, that is, indentations in a metal disc coated with a plastic substrate. The placement, size, and proximity of these pits is defined in part for the specification for the type of optical technology. Newer technologies have been developed to increase the information capacity of a disc, as in digital videodiscs (DVDs) that are slightly thicker, to bring the disc closer to the laser pickup, with slightly smaller, tighter pits. Compact discs, videodiscs, PhotoCDs, and DVDs are popular forms of audio and visual storage media. Optical discs are also used for computer data storage, particularly for backups. optical document recognition ODR. A software process or combination of hardware scanning devices and software, which evaluates the various elements on a page to determine whether they are distinguishable as text, images, symbols, or lines, and

identifies them accordingly. The ODR in its simplest sense does not interpret the text into characters; it merely identifies page layout elements: images, columns, page numbers, text, etc. However, in commercial products, it is commonly combined with optical character recognition (OCR) capabilities in order to optically identify and interpret areas that are text into characters that can be edited with a word processor, text editor, or desktop publishing program. ODR is a somewhat more complex process than OCR; together they comprise powerful tools which are a part of image document management and processing. ODR is particularly valuable for converting archived image information (e.g., microfiche) into documents that can be desktop published, or archived in databases for faster and more efficient search and retrieval. See image document management, optical character recognition, scanner. optical fiber A flexible, light-conducting, filamentous plastic or glass medium used for optical signal transmissions. Optical fiber is typically from 2 to 125 µm thick, and is capable of carrying a variety of highspeed, wide bandwidth transmissions with relatively low loss, when correctly installed. Unlike wire, fiber is not subject to electromagnetic interference or most of the types of radiant eavesdropping techniques that can be used on wire. This has made it very popular for backbone, hazardous area, and multimedia installations. It also does not present the same potential fire hazard as wire electrical cables. Two common types of optical fiber include step-index fibers and graded-index fibers. Step-index fibers have two layers: a lower refractive outer cladding layer and an inner core with a high refractive index. Graded-index fibers also are less refractive toward the outer edge, but rather than being two layers sandwiched together, as in the step-index fibers, the refractivity in the material overall decreases gradually in relation to its distance from the innermost point of the cylinder. Fiber can be bundled without the electrical interference common to bundled wires; a group of fibers works together to provide greater capacity. Singlemode fiber transmissions, in which the signal can only follow one path through the filament, can travel greater distances without repeaters. See multimode optical fiber, single mode optical fiber. optical fiber cable See fiber optic cable. optical fiber ribbon A way of bundling the fibers so that they are laid side-by-side to form a flat ribbon or strip. This is convenient if they are to be installed in narrow areas such as walls or under carpeting. This way of arranging fibers is less common than bundling them into a cylindrical shape. optical handwriting recognition OHR A specialized form of character recognition designed to separate joined shapes and recognize variations of particular letters, in addition to other generalized optical character recognition (OCR) functions. Most OHR systems have to be trained to recognize a particular style of handwriting, since there is so much variation in the letter forms in the way different people write.

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Optical Internetworking Forum OIF. An open trade organization fostering the global development and deployment of interoperable optical data switching and routing technologies. Membership includes service providers, equipment manufacturers, and end users. http://www.oiforum.com/ optical label switching See optical-label switching. optical scanner See optical character recognition, scanner. Optical Society of Japan OSJ. Founded in 1952 as a division of the Japan Society of Applied Physics (JSAP), it is now the biggest division of JSAP with almost 2000 members. OSJ publishes the Japanese Journal of Optics and the Optical Review. It provides educational support, technical working groups, and conferences for its members and sponsors a number of awards for excellence in the field of optics. http:/ /annex.jsap.or.jp/OSJ/index-e.shtml Optical Storage Technology Association OSTA. An international trade association promoting the use of writable optical storage technology, incorporated in 1992. OSTA develops technology “roadmaps,” statistical illustrations of optical storage progress and trends, to define compatible product classes. It is not a standards-development organization per se, but it develops specifications and provides input to other organizations regarding practical implementations of optical storage standards. In July 2001, OSTA announced the development and approval of a new specification for organizing compressed audio files on optical disc, called MultiAudio. The intent is to ensure that discs with compressed audio files (e.g., MP3) are as straightforward and standard Red Book CDs. The format specifies a table of contents access mechanism for CD and DVD playlists and media playback. See MultiAudio, MultiPlay. http://www.osta.org/ optical-label switching OLS. A network switching system developed under the direction of S.J. Ben Yoo through a DARPA ITO-sponsored research project. It was first proposed by Yoo in 1997 and developed independently at around the same time as Multiprotocol Label Switching (MPLS). OLS is a means of implementing packet-switching protocols over optical media. OLS is a scalable ultra-low-latency multiprotocol optical routing/switching system that shares some characteristics with MPLS. Underlying OLS is the packet-switching fabric comprising rapidly tunable wavelength conversion capabilities and scalable arrayed-waveguide grating. OLS is built upon this with a forward look to next generation all-optical Internetworks. OLS routing uses an optical header with a label in the header to determine the packet forwarding. The data are held in the fiber path while the header is examined and may be replaced for the next leg in the transmission path. OLS project goals as of 2000 included router connectivity in excess of 1024 x 1024 and aggregate switching bandwidth of almost a peta-bits-per-second. The multiprotocol optical routing is intended to be interoperable with circuit-, burst-, flow-, and

packet-switched networks. See label switching, Multiprotocol Label Switching, optical burst switching. OQPSK offset quadrature phase shift keying. See quadrature phase shift keying. Orange Book A set of standards for Compact Disc readable (write once) optical media. The previous Red and Yellow Book standards established the basic standards for recording audio and computer data to a Compact Disc. The Orange Book extended these capabilities to enable multisession recordings to be created (though they are not recommended as masters). Red and Yellow Book data can be combined on one disc in whatever order is desired. See Blue Book. ORB See Object Request Broker. ORBCOMM Orbital Communications.

Satellite orbits tend to be circular or more flatly elliptical, and may be further controlled so that the satellite spends a greater part of the orbit over ocean or land masses, depending upon whether it is serving marine or terrestrial communications needs. The orbits are often described in terms of their distance from the Earth as low, medium, and high Earth orbits (LEO, MEO, HEO). Geostationary orbits are a type of high Earth orbit in which the satellite’s movement is paced such that it remains in the same position relative to the Earth.

orbit The path described by a moving body in moreor-less stable balance with the gravity of the body being orbited so that it continues in that path for a significant period of time (usually at least a few hours or days, although orbits of artificial satellites can last for years in a stable orbit). The Earth is in orbit around the Sun, and the Moon is in orbit around the Earth. When the balance is lost and the orbit becomes smaller as the orbiting body is drawn inward, it is said that the orbit is decaying. Many types of orbits (orbits at different heights, with differently shaped paths) are used in telecommunications with artificial satellites. Early communications satellite orbits tended to be circular or low and somewhat flatly elliptical (and tended to decay quickly). Communications were hindered by the necessity of locating the orbiting satellite and keeping it in range before it passed around to the other side of the Earth. Later satellites were put into higher, more stable orbits, which were often geostationary; that is, the orbit was synchronized with the movement of the Earth so that the location

of the satellite was roughly above the same location at all times. The amount by which an orbit deviates from a circle is referred to as its eccentricity. See geostationary, satellite. Orbital Sciences Corporation Commercial developers of global satellite communications services. Orbital Sciences is a space and information systems company which designs, manufactures, and markets space-related infrastructures and products. See OrbLink. OrbLink A global broadband commercial satellite communications network being developed by Orbital Sciences Corporation for deployment around 2002. The designers intend to use the newest technology to construct broadband services that can be offered at lower prices than existing services. OrbLink is based on seven medium Earth orbit (MEO) satellites orbiting at 9000 km in an equatorial orbit, transmitting in extremely high frequency radio bands. Services will include digital voice, data videoconferencing, computer networking, imaging, and other broadband applications. Pending Federal Communications Commission (FCC) approval, intersatellite communications will be at 65.0 to 71.0 GHz at speeds up to 15 Gbps, supporting high-capacity intercontinental trunking. Twoway digital connections will be between 37.5 to 38.5 GHz and 47.7 and 48.7 GHz bands up to about 1.5 Mbps. The seven satellites, plus one spare, are based on Orbital’s STARBus, a small, lightweight, geostationary technology, acquired through a purchase of CTA Incorporated’s space system business. Each satellite will support 100 spot beams. As an economic note on the dynamics of new telecommunications technologies, the total cost of building and deploying the orbital network, according to Orbital Sciences, compares to the cost of installing two transatlantic fiber cables, which provide only about 10% of the trunking capacity of the proposed satellite system. Orckit Communications A developer and manufacturer of high-speed local loop communications systems and participant in a number of network standards working groups. Orckit partners with Fujitsu Network Communications, Inc. order entry The inputting, usually by voice or keyboard, of a customer request for a product or service. On the World Wide Web, Web forms are often available for customers to put in their own order entry. These Web applications are often in the form of shopping carts in which the customer browses various Web pages and enters each product desired into the shopping cart (order batch). The order is typically preprocessed by a CGI and then sent to the appropriate order fulfillment personnel for shipping and billing. Other automated systems allow customers to carry out a complete ordering transaction over a touchtone phone by using the keypad to enter codes and digits. See Automatic Call Distribution. Organization of American States OAS. The OAS Web site provides information on the group. http://www.oas.org/

Organizationally Unique Identifier OUI. A globally unique 24-bit Ethernet address identifier for LANs and MANs managed and assigned by the IEEE Registration Authority online or by phone. The OUI is assigned as a three-octet field in the SubNetwork Attachment Point (SNAP) header, identifying an organization which further creates unique six octet numbers. Together they constitute a distinct Media Access Control (MAC) address or Ethernet address. See Ethernet, IEEE, Token-Ring. originate/answer On a computer data modem, when the user wants to dial out to connect to another computer, a bulletin board, or an Internet access point, the commands for controlling the phone line and dialing the desired number come from the originating modem. “Originate mode” sets up a sequence of events which checks for a dial tone, dials, and handshakes with the receiving modem to establish the connection rate and protocol (or hangs up if the line is busy or is dropped). The receiving modem is set to “answer mode” so it detects an incoming call, answers it, and participates in the rate and protocol negotiation. Most of this is automatically handled through a terminal software program, but it may be necessary to set originate or answer through menu selections, or direct commands through the software to the terminal program. originate restriction A security or specialized use restriction on a phone line which causes it to work only for incoming calls. Outgoing calls are blocked. This restriction is sometimes set on phones adjacent to public areas to prevent people from monopolizing or misusing a phone line. Sometimes the originate restriction applies only to long-distance calls or calls outside a private branch exchange. In some circumstances, the local phone company will partially disconnect a line by setting an originate restriction if the subscriber is behind in the payment of the phone bill. After paying the bill, it is usually necessary to request restoration of full service, as it is seldom done automatically. originator Initiator, beginner, inventor, introducer, founder. The person, entity, device, or station that first communicated a message or started an action or process. Orion A broadband data satellite service provider aiming at international common carriers and individual companies. ortho-correction In satellite imaging, a correctional adjustment for distortion resulting from terrain. orthogonal frequency division multiplex OFDM. A multicarrier modulation system which is similar to discrete multitone in that it utilizes Fourier transforms of data blocks. OFDM is suitable for Digital Subscriber Line (DSL) services. See Digital Subscriber Line, discrete multitone. OS X See Mac OS X. OS/2 Operating System/2. International Business Machines’ 32-bit preemptive multitasking text and object-oriented graphical operating system targeted for Intel-based microcomputers in the late 1980s. It was originally developed for IBM by both IBM and

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Microsoft Corporation, and version 1.0 was released in 1987 to succeed MS-DOS. When an upgrade to OS/2 was well under way, Microsoft pulled out to concentrate on their own operating system in competition with IBM. Many of the same concepts that were part of OS/2 were incorporated into Microsoft Windows NT, which was marketed as a direct competitor to OS/2. In 1991, IBM released OS/2 version 2.0. Version 2.1 added support for multimedia and Windows 3.1 applications. OS/2 had some commercial success in the early and mid-1990s, but by 1996, through aggressive advertising and bundling programs, Windows was better known and more widespread in North America. In spite of this, there are many strong supporters of OS/2, including a worldwide network of Team OS/2 Groups. It is still a popular choice in Western Europe and Canada. Team OS/2 information for OS/2 users is available at their Web site. See Team OS/2. OS/2 SMP OS/2 Symmetric Multiprocessing. This version of IBM’s OS/2 supports systems with multiple processors, making it suitable for Internet services, graphics, and corporate applications, particularly those which operate as various types of resource servers in a networked environment. See OS/2. OS/2 Warp Operating System/2 Warp. By version 3 of IBM’s OS/2 operating system, their operating system product was called OS/2 Warp. The Warp version added increased support for various peripheral devices and reduced memory requirements. It was succeeded by OS/2 Warp Connect which offered networking through full TCP/IP capabilities. OS/2 Warp version 4 was aimed at corporate users. This version included increased networking features, speech-to-text speech recognition software, and built-in support for Sun Microsystems’ Java. See International Business Machines, Java, OS/2. OS/2 Warp Server IBM’s Warp Connect system integrated with their local area network (LAN) server 4.0. This version of OS/2 was designed for handling file and device service sharing on networks. See OS/2. OSCAR Orbiting Satellite Carrying Amateur Radio. A series of orbiting satellites originally developed in the homes and garages of a group of amateur radio enthusiasts. In 1962, the OSCAR Association was incorporated as Project OSCAR, Inc. The early OSCAR satellite projects began in 1961 and continue today in a much expanded and more sophisticated form. Early OSCARs used fairly simple beacon transmitters with nonrechargeable batteries, so they were only useful for a few weeks, but they showed what might be accomplished with relatively simple materials and a lot of cooperative effort. Solar cells and telemetry equipment were added to later versions in order to extend useful life and provide greater control over positioning. Relays were then added, with the aim of eventually providing two-way (bidirectional) communications. OSCAR-AMSAT projects became increasingly sophisticated and, by the time the OSCAR 6, 7, and 8

were in orbit, telemedicine and search and rescue satellite communications were demonstrated to be feasible.

launch mounting spring solar cell antenna

The early OSCAR satellites were put together in a cooperative effort out of makeshift donated parts, yet were well-conceived, pioneer satellite technologies, increasing in sophistication with later projects. OSCAR III is shown here.

The deployment mechanisms of the early OSCARs were particularly interesting to scientists researching satellite installation. The building, launching, and especially the tenuous securement of domestic and international regulatory permissions to launch and operate were a great achievement for amateur enthusiasts, and benefits are still accruing from the hard work and voluntary contributions of radio amateurs. See Overview of OSCAR Projects chart. See AMSAT. OSCE Organization for Security and Co-operation in Europe. oscillation 1. Variation, fluctuation, continuing periodic reversal. Although oscillation in the general sense does not imply a regular oscillation, many waves, materials, and circuits studied or constructed by scientists exhibit fairly regular, predictable oscillating properties. See quartz. 2. The cyclic alternation of electrical properties in a circuit. oscillator An electronic device designed to generate a low-current alternating current (AC) power at a particular frequency according to the values of certain constants in its circuits. In microcomputers, an oscillator can be used to provide a reference frequency for clocking. An oscillator is also useful for generating test signals. See oscilloscope, quartz. oscilloscope A device designed to provide a visual representation of variations in electrical quantities as a function of time, displayed in the form of pulses or waves on a monitor. The size and form of the waves are traditionally tuned for optimum viewing with knobs, as on an old radio. Oscilloscopes are sometimes interfaced with computers to provide a means of directly adjusting and analyzing the oscilloscope signals through software. Oscilloscopes are useful for diagnosis and testing of electronic circuits. OSF See Open Software Foundation (now the Open Group). OSI See Open Systems Interconnection.

Overview of Early OSCAR Satellite Projects Satellite

Launch Date

Tech. Details

Notes

Phase I Satellites – experimental, low orbit, short lifespan.

OSCAR I

12 Dec. 1961

10 lb., beacon, 22-day orbit. Nonrechargeable batteries.

Initiated by a U.S. West Coast group. U.S. Air Force launched.

OSCAR II

2 Jun. 1962

Better coatings and temperature control.

Similar to OSCAR I, but incorporating improvements.

OSCAR *

Not launched

Phase-coherent keying.

Similar structurally to previous.

OSCAR III

9 Mar. 1965

First relay transponder. Solar backup.

Tracking and telemetry equipment. Approx. 3000 mi. range. 18-day transponder use.

OSCAR IV

21 Dec. 1965

High altitude, transponder. Solar, beacon, no telemetry.

Unplanned varying elliptical orbit. Two-way communication achieved. Link between Russia and U.S.

OSCAR 5

23 Jan. 1970

Controllable, magnetic attitude stabilization. No solar or transponder.

Seven analog telemetry channels. Australis-OSCAR 5 (AO-5). Built in Australia. First NASA-launched OSCAR.

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Phase II Satellites – developmental, low orbit, operational, longer lifespan OSCAR 6

15 Oct. 1972

Telemetry, command, transponder. Solar. Store-and-forward system.

Twenty-four telemetry channels. Two-way communications. Falsing and beacon problems. Life span exceeded 4 years. Educational materials printed.

OSCAR 7

15 Nov. 1974

Two transponders, linear frequency translation. Telemetry, radio teletype. Beacons. Up to 4500 miles low altitude.

Many countries contributed various technologies and parts. AMSAT-OSCAR 7 (AO-7). Relayed with OSCAR 6! Almost 7-year lifespan.

OSCAR 8

5 Mar. 1978

10-m antenna. Two transponders (Modes A & J) that could operate simultaneously.

ARRL operated. Cooperatively built by Project OSCAR, AMSAT and JAMSAT. Lasted 5 years.

Phase III Satellites – operational, high elliptical orbit, longer lifespan (see AMSAT).

OSI Transport Protocol OSI TP. The ISO-recommended communications protocol used by X/Open. OSN 1. operations system network. 2. See Open Systems Networking Initiative. OSP See Operator Service Provider. OSSP See Object Serialization Stream Protocol. OST Office of Science and Technology. A U.K. government group founded in 1992 to coordinate science and technology issues across government departments. OSTA See Optical Storage Technology Association. OSTP See Office of Science and Technology Policy. OT See Office of Telecommunications. OTA Office of Technology Assessment (U.S.). OTAR over the air rekey. OTDR See Office of the Director of Telecommunications Regulation. OTE The primary telecommunications carrier in Greece. OTE is government-owned. OTGR Operations Technology Generic Requirements. OTH over the horizon. OTOH An abbreviation for “on the other hand” commonly used in email and online public forums. See AFAIK, IMHO. OTP 1. See Office of Telecommunications Policy. 2. See Open Trading Protocol. OUI See Organizationally Unique Identifier. out-band/out-of-band signaling Control signaling that is carried separate from the informational portion of a message. See Signaling System 7. out-of-range alert In wireless communications, a beep or light that alerts the user that the handset is at the edge of its range and the user shouldn’t move further from the source of the transmission. outage Loss of power, service interruption. See blackout, brownout. outlet 1. Exit, opening for egress, vent. 2. Plug receptacle in a circuit, usually for electricity or connectivity to data transmissions. 3. Source of goods, supplier. outline font, algorithmic font, vector font A character set defined by mathematical algorithms that describe the shape of the letters with graphics primitives such as lines, arcs, ellipses, spline curves, etc. That way, when printed or displayed on a monitor, they will be drawn at the best possible resolution offered by the display system. Unlike bitmap fonts, which are hand drawn as raster images that cannot be significantly reduced or enlarged, vector fonts look good at sizes ranging from 4 points to 100 points and much larger. Outline fonts are resolution- and platform-independent, provided an interpreter is available on the system for the particular format that is being used. Since outline fonts are widely supported on many platforms, this is usually not a limitation. The first outline fonts widely used on desktop computers were defined with the PostScript page description language in the mid-1980s. These were released

for use with desktop publishing programs on the Macintosh computer, and were incorporated into the Apple LaserWriter printer introduced in 1985, which almost single-handedly launched the desktop publishing revolution. The introduction of outline fonts at a price that consumers could afford allowed individual publishers, writers, and small presses to release documents, books, pamphlets, and other printed matter that were cost prohibitive prior to the mid1980s. Adobe continued to develop PostScript fonts after they were first released. “Hinting” was added, a process that adjusts small fonts to reproduce better on lower resolution devices (e.g., 300 dpi printers). Type I, Type II and, recently, Type III fonts were specified. Type I and Type II are still widely in use. PostScript fonts have been ported to many computer platforms and printers, and continue to be well-supported, particularly in the service bureau and printing industries. TrueType fonts are another type of vector font commonly used in computer applications. Unlike bitmap fonts, TrueType fonts provide professional-looking output on common printers, such as the HP LaserJet series, without the need of a PostScript interpreter. Thus, it’s a lower cost option to PostScript. The main difference between Adobe PostScript and Microsoft TrueType fonts is that PostScript is a full page description language, so it can define not only the shape of the font, but the behavior of the letters, and their positioning on the page (swirls, curves, graphic inserts, clipping, etc.). TrueType fonts were intended more specifically to define typefaces, rather than all the graphic elements of a page, and thus are more limited and more commonly used for less embellished text effects in word processing. outline font attribute While an “outline font” generally means a vector font, an “outlined font” or font manipulated with an outline text attribute means one rendered as an outline, rather than as a filled entity. Outlining is a common feature in desktop publishing programs and some word processors. The effect is usually used for emphasis or variety, particularly in headlines. It should be used with discretion. Too much outlined text or outlined text that is too small can interfere with legibility.

ABCabc123 ABCabc123 output 1. That which results from, or comes out of, a process or system. 2. The combined signal and content information of a transmission. 3. The result of a computer process, e.g., the output of a word processing session might be a printed document, Web page, or a facsimile transmission. output device A device that facilitates the communication or transmission of information, usually in another form or format. In most cases, an output device is a human interface in the sense that it facilitates the translation or movement of information between nonhuman-readable forms and humanreadable forms, or between single-copy modes and

multiple-distribution modes intended for a wider audience. outside plant OSP. The various outside structures, devices, and cabling installations that together comprise a network. These may be installed above or below ground. Those supported by utility poles may be termed aerial. See joint pole for utility pole information and diagrams. outside plant access cabinet OPAC. Solid, compact weather-resistant cabinets for housing remote-access network equipment and connections, usually in office and industrial park environments. The cabinets may be controlled for factors such as temperature and humidity in order to protect sensitive electronic components and are usually designed to deter vandalism. Besides leaving more space free inside the building, the outside access cabinet makes it possible for maintenance personnel to access the devices without entering the building premises. outsourcing Outsourcing is the process of assigning production or management tasks to an external consultant or organization. Outsourcing is practical when special expertise is needed, or the project is short, and it is not cost effective to hire new permanent staff to handle a project that may take only a few days or months. Specialized design projects, advertising, documentation, and cyclic/seasonal projects are often outsourced. Network administration is often outsourced by small companies, whereas a company with a larger or more complex network would probably have an in-house system administrator. Telephone answering services are a common form of outsourcing used by small businesses and home businesses. Utilizing an answering service is less expensive than hiring a receptionist – a good solution for small companies that don’t receive a lot of incoming calls. OutWATS Outward Wide Area Telephone Services. A WATS service for outgoing calls, which is available at bulk-use discounts. See InWATS, WATS. OV2-5 A research satellite designed to measure solar and cosmic rays and magnetic influences. It was launched in September 1968 into a circular equatorial orbit at an altitude of 22,000 miles. A model of the OV2 was donated to the U.S. Air Force Museum by the Northrop Corporation. overcoat-incident recording OCIR. A new technology for recording optical storage media that permits higher density data per unit area than previous methods such as substrated-incident recording. Traditionally, optical discs have used a substrate laid down over the recording surface to protect the data from abrasions, contamination, and oxidation. This limited the areal density of the recorded information. OCIR technology was developed by Maxoptix (trademarked as OverCoat Incident Recording with patents pending). In OCIR, the recorded information is imprinted on top of the substrate (similar to hard disk media) and then covered with a protective layer of acrylic that is much thicker than hard disk and tape recording media, but thinner than standard optical

recording substrates. Thus, the lens can be positioned closer to the recording surface, realizing a higher numerical aperture (NA) for recording at higher data densities. Maxoptix’s goal was to realize 40 GBytes of recorded data at 30 Mbps transfer rates. See airincident recording, substrate-incident recording, surface-array recording. overflow 1. Traffic or data in excess of what is typically found on a system, or in excess of what the system is capable of handling. Some systems have additional or alternate circuits, lines, systems, or operators to handle overflow, while others may be slowed down in terms of speed of service, or may cease to function. 2. In telephone circuits, overflow traffic may be diverted to another trunk line. See erlang. overflow, data In programming, an overflow occurs when an operation generates a result for which there is insufficient address or storage space. overhead The portion of a task, data block, or operation that provides management information pertaining to the task, data, or operation, which is not part of its integral content. For example, the overhead in a graphics file may consist of a header containing size and palette information, which is not part of the image itself. The overhead in a parallel processing operation may be the time and processing it takes to handle the logistics of farming out the tasks and recombining the results of the processes. In networks, overhead exists in the form of protocol information, timing information, error data, security bits, routing, priority, and more. Given the amount of overhead in networks, it’s a marvel that they can work so effectively. overhead transparency, foil A transparent medium receptive to photocopy toner or various inks which is used in conjunction with a bright light and projector to project information on a large surface such as a screen or plain wall. Overhead transparencies are often used for presentations, especially to illustrate lectures. Overhead transparency films come in a variety of compositions; some can be photocopied in black and white, some in color. Don’t use regular transparency paper in a laser printer or photocopier, as the plastic may melt and destroy the internal mechanisms. Cardboard frames can be purchased to support the transparencies, which are somewhat flimsy and otherwise hard to hold and organize. overlay 1. n. A keyboard template or sheath. See keyboard overlay. 2. v. A programming technique in which a limited amount of storage is extended by reusing portions which are not immediately or subsequently required, or by initiating less commonly used routines only on demand. In telephone applications, overlays may be used to bring various tasks into memory as needed. Some versions of BASIC have commands (e.g., LSET) which allow a variable in RAM to be overwritten with a subsequent variable in order to prevent eventual slowdowns from garbage collection, that is, from the reorganization of storage to accommodate more information. overlay area code A telephone area code assigned as a parallel code in an existing service area. These

O

are commonly assigned to mobile services, like cellular and pager services, so that the area code is separate from the geographic code assigned to that region. These are not yet prevalent, but are expected to increase as mobile services are more widely distributed. See North American area codes for a chart of telephone and mobile service area codes. overlay network A protocol or application-specific subnetwork, managed and configured independently of its underlying infrastructure, and interconnected by Internet Protocol (IP) encapsulation tunnels over production networks. Recent protocols are supported on overlay networks, including Mbone (multicast IP) and 6bone (IPv6). overlay, video In video editing, it is common to overlay two video signals, or to overlay a computer signal over a video signal, or vice versa. Newscasts will often overlay a human weather forecaster over a computer-generated weather map. In cinema action shots, a stunt worker in a barrel may be overlaid on an image of the Niagara Falls. See chromakey. override 1. To overlap, to neutralize, to take over, to dominate. A stronger signal, such as an emergency signal, can override a regular transmission. A boss can override the decision of a subordinate; a priority transmission can override current transmissions. An operator can override a current phone conversation. Some private branch phone systems are configured so that someone in authority has the option of overriding other conversations, a power that should be used with discretion. overrun To overwhelm, to swarm, to go above or beyond an edge or capacity, to overflow. A cost overrun happens when someone goes over budget or some other allotted quantity. A data overrun can happen when the receiving system isn’t fast enough or smart enough to handle the incoming transmission. A printer overrun can happen if the print mechanism continues to function after the paper runs out (some facsimile machines still do this). Overruns often result in discard or loss of information. See cell rate, leaky bucket. oversampling A process of redundant sampling used in some multiplexing schemes. overscan, full scan An image output to a monitor that extends to the maximum outer extents of the cathode ray tube (CRT) or other scanning display device. Overscan on computers may be achieved by increasing the resolution of the display or by adjusting position and size controls associated with the display device. Overscan display modes are common in video applications, where the signal is not being optimized for the computer monitor, but for the video recording medium to which it is being output. Overscan may also be a screen option on some systems that are adapted for desktop video and usually adds about 10 to 30 pixels to each edge of the displayable resolution. (Thus, a 320 x 480-scanline interlaced image might become 360 x 525 scanlines in overscan mode, for example.)

outer extents regular display region overscan display region

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Employing overscan modes will increase the image area of an image by using the scanning region around the outer edges on a computer monitor. These regions are not used for all applications due to memory constraints and curvature at the outer monitor edges. Nevertheless, there are times when this extra resolution may be important for displaying information or outputting to traditional video recording resolutions.

Flat screen monitors are becoming more widely available, but in the past, cathode ray tubes had a significant curvature at the outer edges which would distort the image (like looking through a lens) at the outer edges. In order to minimize distortion, the image is usually not displayed to its fullest extent, but rather to the point on the front of the tube at which the curve begins. The edge of the monitor casing is usually designed by the manufacturer to fall approximately at the same point or slightly outside the point at which the overscan image falls. See cathode ray tube. overtime period In a pay-per-time-connected service, the time that elapses after the paid-up period has been exceeded. When using a payphone, the time after the first insertion of the coins has run out is overtime, and the operator may request additional funds or terminate the call. The same general idea applies to per-pay network access, time-sharing, or any other system in which a set amount of time is billed periodically, or is prepaid, with the option for the user to exceed the usage period as long as additional fees are paid, often at a higher rate. OVS See Open Video System. OWT Operator Work Time. OXC See optical cross connect. oxidation The process of combining with oxygen, often resulting in a significant change in the material oxidized that may degrade it or otherwise influence its integrity or usefulness for a particular purpose. Oxidation is a particular concern in external wiring installations or those exposed to water or chemicals. See corrosion. oxymoron A combination of contradictory, incongruous words. Puns sometimes employ oxymoronic implications which may or may not be true. Satirical examples include: common sense, military intelligence, smart ass, casual dress, friendly fire, and authentic reproduction.

p 1. symb. pico-. 2. abbrev. power. P 1. symb. permeance. 2. symb. peta-. p connector A power connector commonly used for attaching internal computer peripherals such as floppy drives, hard drives, CD-ROM drives, etc. Computer power connectors are largely standardized as 4-pin, keyed connectors. (In the late 1970s and early 1980s, they weren’t always keyed.) It is preferable to call this a power connector to prevent ambiguity with 68-pin P connectors. See P connector. +5 volts (red) ground (black)

ground (black) +12 volts (yellow)

+12 volts ground ground +5 volts

A typical power connector for computer peripherals such as hard disk drives. In early systems, they weren’t keyed and could cause damage if inserted the wrong way. They are now typically keyed (notched on one side) to prevent incorrect connections.

P connector 1. A standardized 68-pin electrical data connector, specified by ANSI, commonly used for 8and 16-bit data buses for computer peripherals such as SCSI drives, especially SCSI-3, as a P connector can support wide bus, high-density data transmissions. The Very High Density Cable Interconnect (VHDCI) connector is an Alternative 4 P connector with the same pinouts as the 68-pin connector, but it enables multiple SCSI connectors to be connected to one backplate. See A connector, p connector. 2. See Polaroid connector. P channel, partial channel On the Ranger series of aircraft sent to the Moon to take pictures in the early 1960s, the camera system was divided into two channels, the F (full) channel and the P (partial) channel, each with separate timers, transmitters, and power supplies. The P channel had four cameras: two narrow-angle cameras and two wide-angle cameras. The final P channel image was taken approximately 0.3 seconds before impact with the Moon’s surface, at

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an altitude of about 600 m. The mission not only provided images 1000 times better than those that could be taken from Earth, but also provided important data regarding the landing of a piloted spacecraft on the Moon’s surface. p region In semiconductor component theory and engineering, the p region is a region in which the conduction-electron density characteristics result in positive “holes.” The p region is related to n materials in the n region, where conduction-electron density exceeds hole density. See n region, p-n junction. P Series Recommendations A series of ITU-T recommendations providing guidelines for telephone transmissions quality, installations, and local phone line networks. These guidelines are available as publications from the ITU-T for purchase from the Net. Since ITU-T specifications and recommendations are widely followed by vendors in the telecommunications industry, those wanting to maximize interoperability with other systems need to be aware of the information disseminated by the ITU-T. A full list of general categories is listed in the Appendix and specific series topics are listed under individual entries in this dictionary, e.g., M Series Recommendations. See P Series Recommendations chart. P-frame predictive-coded frame. In MPEG animations, a picture which has been encoded into a video frame according to information extrapolated from past frames in the sequence, using predicted motion compensation algorithms. See B-frame, I-frame, MPEG decoder. P-picture predictive-coded picture. In MPEG animations, a picture that is to be encoded according to past frames in the sequence using predicted motion compensation algorithms. Once it is encoded, it is considered to be a P-frame. See MPEG decoder. P3P See Platform for Privacy. pA abbrev. picoampere. PA See public address system. PABX See Private Automatic Branch Exchange. PACA 1. See Pacific and Asian Communication Association. 2. Picture Agency Council of America. A trade organization supporting stock image agencies in North America. http://www.stockindustry.org. 3. See Priority Access and Channel Assignment.

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ITU-T P Series Recommendations Telephone transmission quality, telephone installations, local line networks

P.63

Methods for the evaluation of transmission quality on the basis of objective measurements

P.10

Vocabulary of terms on telephone transmission quality and telephone sets

P.64

Determination of sensitivity/frequency characteristics of local telephone systems

P.11

Effect of transmission impairments

P.65

P.16

Subjective effects of direct crosstalk; thresholds of audibility and intelligibility

Objective instrumentation for the determination of loudness ratings

P.66

Methods for evaluating the transmission performance of digital telephone sets

P.30

Transmission performance of group audio terminals (GATs)

P.75

P.32

Evaluation of the efficiency of telephone booths and acoustic hoods

Standard conditioning method for handsets with carbon microphones

P.76

Determination of loudness ratings; fundamental principles

P.78

Subjective testing method for determination of loudness ratings in accordance with Recommendation P.76

P.79

Calculation of loudness ratings for telephone sets

P.82

Method for evaluation of service from the standpoint of speech transmission quality

P.84

Subjective listening test method for evaluating digital circuit multiplication and packetized voice systems

P.85

A method for subjective performance assessment of the quality of speech voice output devices

P.310

Transmission characteristics for telephone-band (300 to 3400 Hz) digital telephones

P.311

Transmission characteristics for wideband (150 to 7000 Hz) digital handset telephones

P.313

Transmission characteristics for cordless and mobile digital terminals

P.340

Transmission characteristics of handsfree telephones

P.341

Transmission characteristics for wideband (150 to 7000 Hz) digital handsfree telephony terminals

P.342

Transmission characteristics for telephone band (300 to 3400 Hz) digital loudspeaking and hands-free telephony terminals

P.350

Handset dimensions – formerly ITU-T P.35

P.33

Subscriber telephone sets containing either loudspeaking receivers or microphones associated with amplifiers

P.35

Handset telephones

P.36

Efficiency of devices for preventing the occurrence of excessive acoustic pressure by telephone receivers

P.38

Transmission characteristics of operator telephone systems (OTS)

P.48

Specification for an intermediate reference system

P.50

Test signals

P.51

Artificial mouth

P.52

Volume meters

P.53

Psophometer for use on telephonetype circuits

P.54

Sound level meters (apparatus for the objective measurement of room noise)

P.55

Apparatus for the measurement of impulsive noise

P.56

Objective measurement of active speech level

P.57

Artificial ears

P.58

Head and torso simulator for telephonometry

P.59

Artificial conversational speech

P.61

Methods for the calibration of condenser microphones

P.62

Measurements on subscribers' telephone equipment

P.360

Efficiency of devices for preventing the occurrence of excessive acoustic pressure by telephone receivers

P.931

Multimedia communications delay, synchronization and frame rate measurement

P.370

Coupling hearing aids to telephone sets

Supplements

P.501

Test signals for use in telephonometry

P.Sup1

P.502

Objective test methods for speech communication systems using complex test signals

Precautions to be taken for correct installation and maintenance of an IRS

P.Sup10 Considerations relating to transmission characteristics for analogue handset telephones

P.561

In-service nonintrusive measurement device – voice service measurements

P.562

Analysis and interpretation of INMD voice service measurements

P.Sup14 Subjective performance assessment of digital processes using the modulated noise reference unit (MNRU)

P.581

Use of head and torso simulator (HATS) for hands-free terminal testing

P.Sup15 Wideband (7 kHz) modulated noise reference unit (MNRU) with noise shaping

P.800

Methods for subjective determination of transmission quality

P.810

Modulated noise reference unit (MNRU)

P.Sup16 Guidelines for placement of microphones and loudspeakers in telephone conference rooms and for Group Audio Terminals (GATs)

P.830

Subjective performance assessment of telephone-band and wideband digital codecs

P.831

Subjective performance evaluation of network echo cancellers

P.832

Subjective performance evaluation of hands-free terminals

P.833

Methodology for derivation of equipment impairment factors from subjective listening-only tests

P.861

Objective quality measurement of telephone-band (300 to 3400 Hz) speech codecs

P.862

Perceptual evaluation of speech quality (PESQ), an objective method for end-to-end speech quality assessment of narrowband telephone networks and speech codecs

P.910

Subjective video quality assessment methods for multimedia applications

P.911

Subjective audiovisual quality assessment methods for multimedia applications

P.920

Interactive test methods for audiovisual communications

P.930

Principles of a reference impairment system for video

P.Sup17 Direct loudness balance against the intermediate reference system (IRS) for the subjective determination of loudness ratings P.Sup19 Information on some loudness loss related ratings P.Sup20 Examples of measurements of handset receive-frequency responses: dependence on earcap leakage losses P.Sup22 Transmission characteristics of wideband audio telephones P.Sup23 ITU-T coded-speech database

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Pacific and Asian Communication Association PACA. A nonprofit educational, literary, and scientific organization founded in March 1995. PACA supports and promotes the research, criticism, and application of artistic, humanistic, and social scientific principles of communication. PACA publishes the journal Human Communication, and sponsors various educational workshops and conferences. http://www.ukans.edu/~paca/ pack To compress characters or data together to conserve space. In the old 4-kilobyte computers from the 1970s that used BASIC as the programming language, “string packing” was often employed to save precious memory. String packing involved running as many characters and commands together in as brief a way as possible on each numbered line of the source code. Packing is most commonly used now to reduce the size of medium and large binary files, especially sound and image files, to lower the amount of time it takes to transmit the files over a network, as when downloading from an ftp site. Database entries often have a lot of empty space in them and so may be packed to reduce the storage size of files. Packard, David (1912-1996) Founder, along with William Hewlett, of the Hewlett-Packard computer company, one of the well-respected pioneering companies of the computing industry. The company had its humble beginnings in the Packard garage in Palo Alto, California, and has grown into a multinational company with over 100,000 employees. Packard also cofounded the American Electronics Association, and was a member of the President’s Council of Advisors on Science and Technology for 4 years. In 1996, David Packard, successful businessman and philanthropist, died at the age of 83. See Hewlett, William R.; Hewlett-Packard. Packed Encoding Rules PER. Developed in the early 1990s, PER is one of three major encoding schemes used in open architectures development. Unlike BER, tags are ignored and length fields may be omitted. PER provides a means for creating more succinct encodings optimized for bits on the line and generally has lower bandwidth requirements than BER or LWER. See Basic Encoding Rules, LightWeight Encoding Rules. packet 1. A generic term for a unit of data formed as a bundle with a certain specified organization, according to a protocol. Other designations for network units and bundles include cell and frame. Although packet formats vary, they most typically include a header, an information payload, and a trailer. The header may contain a number of pieces of information, including priority, source, destination, length of packet, etc. The payload is the message or information being sent, and may be split over a number of packets. The trailer may include flags, signals, and error detection or correction data. When a series of related packets is transmitted over a network, they may not all take the same route, and so disassembly, routing, and assembly procedures may be applied to transmitted packets; instructions to coordinate this process may or may not be included in some of the packets.

Sometimes packet-switched networks are connected to non-packet-switched networks, in which case tunneling takes place, or conversion through a packet assembler/disassembler, to accommodate the differences in formats. packet assembler/disassembler PAD. In packetbased systems, information is converted into data units known as packets, and then transmitted. At the receiving end, these packets are apprehended and disassembled to turn them back into the information contained in the original content. packet filtering The evaluation of packet structure or contents in order to selectively reject or accept passage of the packet through a network junction. See firewall. packet radio Packet radio is a combination of computer equipment and radio transmissions used to exchange messages. Microcomputers and terminal node controllers (TNCs) are commonly used in packet radio systems. The computer is cabled to a radio transceiver at each end of the communication. Because computers have store and forward, or other types of scheduling capabilities, the operator doesn’t have to be present when the message is sent or received. In radio, this is called time-shifted communications. The system could be configured to send at a time when interference is less likely to be encountered, or when a favorable time of day occurs at the sending or receiving end. Packet radio transmission speeds are fast enough that various types of propagation can be used, including meteor-scatter. Due to the nature of packet transmission and its built-in error-correcting mechanisms, packet transmissions are reliable. Packet radio uses a number of protocols and favors the Open Systems Interconnection (OSI) reference model. Common protocols in use include NET/ROM, AX.25, TCP/IP, and ROSE. packet reservation multiple access PRMA. An enhanced time division multiple access (TDMA), which incorporates aspects of S-ALOHA. It is suitable for mobile transmissions. See ALOHA, time division multiple access. packet sniffer A diagnostic and snooping mechanism for examining the contents of network packets during transmission. See packet tracing. packet switched radio See packet radio. packet switching A computer communications technology developed in the early 1960s that bundles up information into discrete data packets which can be sent out in separate paths, like breaking up the cars on a train sending them on separate tracks, and putting them all back together again at the destination. In the 1960s, computing was becoming more accessible, generating greater interest in its use and spurring the manufacture of various types of systems. Practical packet-switched implementations began to appear in the 1970s, and separate server computers to handle various specialized purposes, such as accounting, opened the doors to the development of various types of distributed computing architectures. The rise of ARPANET greatly influenced the devel-

opment and acceptance of packet switching. With hosts springing up in distant locations and specialization and the variety of computing tasks increasing, packet switching was a practical way to facilitate intercomputer communications. Gradually, layered architectures emerged, separating user functions and applications from lower level operating functions. This enabled information carried in packets to be communicated through many different types of systems, while still retaining the unique operating features and user interfaces of each system. Historically, telephone networks were built around circuit-switching. This meant that a dedicated path through the switching system had to be established (and was tied up) for the duration of the call. In a large global network where many institutions are online all the time, this is not a practical solution. A better way for large systems is to route information through whatever path is most practical at the time (since some systems may be inaccessible or offline without notice), to divide the packets up, if necessary, if routes change while the data are en route, and to resend any portions of the message that don’t make it through. It works 24 hours a day, and will continue to try to send the data in a dynamically changing environment, even if intermediate hosts or the receiving party are temporarily offline. This essential flexibility is at the heart of packet-switching architectures and is incorporated into huge cooperative systems like the Internet. See circuit switching, Open Systems Interconnection, Systems Network Architecture, X.25. packet switching network A communications network in which a channel is occupied only for the time during which the packet, a unit of data, is transmitted, a common distributed data network format. See Frame Relay. packet tracing See packet sniffer. pad connector Short for touchpad connector. A connector that enables a touchpad keyboard (with a flat surface rather than raised keys) or other flat input configuration to be attached to an electronic device (usually a computer or kiosk terminal). PAG See Producers Advocacy Group. page description language PDL. A means of providing commands to a system for the placement and formatting of page elements, such as text and graphics. Adobe PostScript is widely used, powerful page description language, and HTML is a very basic page description language extensively used to format information for viewing with a Web browser. Various printers include page description languages which are usually somewhere between PostScript and HTML in complexity. PageNet A registered trademark service of Paging Network, Inc., one of the largest international wireless messaging companies. PageNet services include a range of one- and two-directional voice, text, and numeric paging services. pager 1. A general broadcasting loudspeaker connected to a phone or microphone, usually in a business,

or educational or health care institution. See public address system. 2. A portable, wireless handheld device which can emit an audible, short verbal message or short alphanumeric message. These are often used by emergency workers, sales representatives, and business professionals. See paging. paging Alerting a recipient that there is a message or item awaiting his or her attention. Public address systems can be used to page employees or clientele when packages are ready, when there is a phone call, or when lost children or items have been located or turned in. Pagers commonly known as beepers are portable wireless devices that will make an audible beeping sound to signal that a message or call is waiting, or that the user has to go to a certain location if paged. Portable wireless alphanumeric pagers can display a short message or telephone number to notify the user of a situation or phone message. Pagers are commonly used by professionals in the field, emergency workers, and industrial yard workers. See public address system, Short Message Service. paging system PS. A system which allows a message to be broadcast broadly to anyone within range of the speaker, usually to attract the attention of a particular person or party, to give instructions, or to ask someone to pick up a message. Paging systems are common in hospitals, schools, and shopping malls. See public address system. pair A pair of associated wires, often twisted together to facilitate electrical conductance and/or to reduce noise. Most phone networks are based on decadesold circuits of twisted-pair copper wires. pair assignment The assigning of a specific current, transmission, or function to a twisted-pair wire. These are often designated with a code or color, in order to make interconnections quicker and less error-prone. PAL 1. See phase alternate line. 2. See programmable array logic. PALC plasma-addressed liquid crystal. See liquid crystal display, plasma display panel. palette The colors which collectively comprise the available options for creating an image. In paint pigments, the palette usually includes a number of primary colors, a few difficult-to-mix intermediary pigments (such as some shades of mauve and brown), and white and black. In computer palettes, several choices are usually available, depending partly upon the number of colors in which the image will be displayed, and also depending upon whether the output will be RGB, CMYK, or some other system. palette board The physical board or virtual menu which holds the available pigments or colors. Thus, a painter’s palette is usually some type of wooden or plastic tray, and a computer artist’s palette is usually a window, menu, or dialog box. In some software, the term palette is more loosely used to mean any window that comes up with a range of drawingrelated options (patterns, line drawing tools, etc.). Paley, William S. An American experimenter and business tycoon who purchased and developed the Columbia Phonograph Broadcasting System (1927) into the Columbia Broadcasting System (CBS) in

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1928. Under his leadership, the company grew and added new products and services to its line. In 1983 Paley retired from CBS, only to return 3 years later to work with Lawrence Tisch. In 1995 CBS was bought by Westinghouse. In 1975, Paley established the Museum of Television and Radio in New York, an educational resource and archive of historical and culturally important broadcasts. The William S. Paley Foundation, Inc. has been established in his honor. Palo Alto Research Center PARC. One of several Xerox research installations, PARC was founded in 1970 in the Stanford University Industrial Park. It is the site of many remarkable pioneer developments in the field of computers and telecommunications. The PARC was a hotbed in the 1970s for many original developments in object-oriented programming and computer interface design. Both Apple and Microsoft toured the facility in their early days and were inspired by their experiences there, particularly demonstrations of the Alto computer running Smalltalk applications. See Kay, Alan; Smalltalk. PAM 1. payload assist module. A shuttle satellite deployment mechanism. The satellite in this context is considered the payload. 2. See port adapter module. 3. See pulse amplitude modulation. panel switch A commercially successful electromechanical telephone switching system developed in the AT&T labs in 1921, based on Lorimer one-step selection concepts. It incorporated mechanical selectors to connect calls. At the time the panel switch was introduced, independents were widely using the step-by-step switch developed a year earlier. The panel switch technology allowed customers to dial their own calls, albeit with a lot of noise in the early versions. The panel switch was widely used in the United States until the 1950s, when it was superseded by the crossbar switch, which had been developed in the late 1930s. See crossbar switch, Lorimer switch, rotary switch, step-by-step switch. panoramic camera A camera configured to take very wide, cinematic shots to provide the same feel that humans experience when scanning the horizon. The first patent for the panoramic camera was granted in 1888 to Canadian inventor John Connon. Connon’s camera could swivel a full 360° in one exposure by advancing the film in synchronization with the movement of the camera, resulting in a long, twoand-a-half-foot, unspliced image. In spite of its innovative aspects and the fidelity of the images it produced, it unfortunately never caught on, with most photographers using fish eye lenses or taking a series of shots and then combining them later. panoramic receiver A device used in radio communications which provides continuous monitoring of a specified band of frequencies. On a computer monitor, signals are displayed in graph form, with vertical blips moving horizontally along the X axis and amplitude graphed on the Y axis. Pantone Matching System PMS. A model for standardizing the selection of pigments and reproduction

of color printed materials. Pantone colors are used almost universally by printing professionals as one of the means to display, select, and specify the contents of colored inks used on presses. In the last few years, Pantone matching has also been added to many better quality computer desktop publishing and graphics programs. Pantone systems describe both solid (spot) color printing and process color printing for glossy and matte papers. The swatches are invaluable for design work. They should be shielded from light sources, and replaced every year or so. PANSAT A small, spherical, nonrecoverable communications satellite developed by the Naval Postgraduate School (NPS) in Monterey, California, deployed by the Space Shuttle Discovery in October 1998.

An electronic still image of PANSAT just after deployment from the Space Shuttle Discovery while in Earth orbit. [NASA image.]

PAP 1. packet-level procedure. 2. See Public Access Profile. paper tape An information storage medium. Paper designed to have specific areas of the tape encoded and punched or electrostatically recorded onto the tape, for subsequent reading by a paper tape reader or other interpretive device, such as a computer, stock ticker machine, player piano, or music box. This means of information encoding and storage was used to program early computers and had many characteristics in common with computer punch cards. Early telegraph receivers used paper tape systems designed by inventors such as Bain and Morse. Later teletypewriter systems used tapes to save transmission time and money by being composed offline and sent only when complete. This also provided a way to correct significant errors before transmission, since a bad tape could always be repunched. Paper tapes have been superseded by tape drives, hard drives, floppy diskettes, magneto-optical discs, cartridges, and memory cards. See Bain, Alexander; Morse, Samuel F. B. paper tape punch A device designed to receive or interpret coded information and translate it into physical locations on a paper tape and punch them accordingly.

paper tape reader A device which detects and translates the encoded holes in punched paper tape as the tape moves through the machine. The machine may be an interface to a display device, or may be selfcontained. Older paper tape readers required that the holes be completely punched out and were usually read by optical means. Later machines could read semi-perforated or chadless tape, usually by means of physical sensors. See Hollerith code, paper tape punch, punch card. “paperclip” computer A true homebrew hobbyist computer concept, this digital computer was described by Edward Alcosser et al., in 1967 in the book titled How to Build a Working Digital Computer. The computer is built from common items found around a house, including tin cans and paperclips. A commercial version of the machine was marketed in 1969 by COMSPACE under the name of Arkay CT-650 for about $1000. See Arkay CT-650. papertape, electrostatic A type of chemically sensitive paper tape stimulated by electricity such that a mark appears on the paper. Used in early telegraph receivers. PAR 1. Positive Acknowledgment Retransmit. 2. Precision Approach Radar. parabola A plane curve that is frequently studied and described in various disciplines including physics, geometry, and art. Parabolic curves are observed in the motion of objects and are used in the manufacture of reflectors and antennas. See parabolic antenna, parabolic reflector. parabolic antenna An antenna designed with a characteristic parabolic “dish” shape that captures a directional beam and focuses it, usually through a feed horn. This shape is especially appropriate for very short, directional transmission waves, such as microwaves, and the diameter of the antenna is designed to correspond with a multiple of the length of the wavelength being received. Parabolic antennas may be made from a variety of materials: solid metal, mesh metal, fiberglass. This style of antenna is commonly used for microwave satellite transmissions, though it is also used for some long-distance space applications, such as space probe communications. See antenna, feed horn, microwave antenna, low noise amplifier. parabolic reflector An antenna, or other reflector, which utilizes the characteristics of the shape of a parabola to concentrate and direct reflecting beams. See parabola, parabolic antenna. paradigm A clear or typical example, a standard, ideal, or archetype. paradigm shift A fundamental, significant change in the way something is perceived or understood, particularly if it has been taken for granted, or assumed to be true for a long time, or by a majority of the population. In other words, the situation or thing itself has not changed, but our way of understanding it has. A general paradigm shift occurred when humans, most of whom believed that the Earth was the center of the solar system and even the universe, acknowl-

edged that the Earth revolves around the sun. The discovery that matter at the atomic level (quantum mechanics) did not behave according to accepted models of classical mechanics represented a paradigm shift in physics. Paradigm shifts often take a long time, sometimes decades or centuries (although transition periods are collapsing as education and television become widespread), and those who first propose new ideas and ways of looking at things are often pilloried or persecuted (even beaten to death or hanged) for their assertions. The suggestion that computers could be taught to be “intelligent,” or to play games intelligently, was met with almost universal contempt in the 1960s and 1970s. In 1997, a computer beat a grandmaster chess player, an event that added credence to the argument that intelligent computers could be developed, and may someday surpass humans in specific or generalized intelligence, or develop machine intelligence of which humans are not capable.

feed horn parabolic reflector supporting struts

P This roof-mounted parabolic antenna is about 8 feet across and uses a mesh parabola to reduce weight and wind resistance.

One of the bigger challenges in telecommunications is designing antennas and transmissions technologies that can communicate over vast distances in the inclement, radiation-high, temperature-fluctuating environments characteristic of space. The Cassini Saturn probe shown here in its testing phases, in 1996, is equipped on top with a parabolic radio antenna provided by the Italian Space Agency (ASI). [NASA/JPL image detail.]

parallel port An interface port on a computing system that permits the connection of parallel devices for the simultaneous transfer of data across multiple transmission wires. Most microcomputers are now standardized to 25-pin parallel D connectors, communicating with Centronics-compatible parallel protocols (although there are individual makers who use slight variations of the standard). Due to the increased speed of transmission over serial communications, parallel ports are commonly used for outputting to printers and other types of peripherals like cartridge drives. See serial port. parallel processing Carrying out two or more tasks, more or less concurrently, usually with the intention of carrying out the processing at a faster speed, or otherwise more efficiently. See concurrent programming. parameter A property which records, embodies, or determines a characteristic of an object or system. In communications, parameters affect many characteristics such as size, shape, speed, timing intervals, addresses, identities, etc. parametric amplifier A type of low noise, radio-frequency amplifier which employs high-frequency alternating current (AC) for power. Used with microwave frequency electron beam devices.

The U.S. Patent and Trademark Office is endeavoring to make patent and trademark information available online to the public. Patent abstracts and descriptions are currently available, and diagrams are scheduled to come online following the text information.

parametric design The process of using general parameters, rather than individual measures, to automate computer-aided design and drafting (CAD) and computer-aided manufacturing (CAM). Parametric design incorporates a form of expert system and is particularly valuable in situations where many small variations on a basic design (bolts, boxes, modem covers, PC boards, telephone handsets, etc.) need to be designed and manufactured. In these cases,

a computer program can be used to automate the design process, by providing guidelines, rather than single-part measurements, to turn out the many needed variations thousands of times faster than a CAD operator could draw each one by hand. One of the early patents for an applied parametric design computer program was awarded to Synthesis (OfficeCad), in Washington State, in the 1980s. It can be accessed online, along with other patents filed since the mid-1970s, on the U.S. Patent and Trademark Office’s Web site. See CAD, expert system. http://patents.uspto.gov/ parametric equalizer A component device used in sound systems to selectively manipulate selected frequencies in order to adjust the sound, usually to suit the taste of the listener. parasite An organism or process which feeds off another without providing a return. In technology, the term can refer to a process, or a mechanical or electrical device that monitors or uses transmissions clandestinely, or without the usual compensation to the provider of the transmission. Small wiretap devices are sometimes called parasites, especially if they draw their power from the line being tapped. PARC, Xerox PARC See Palo Alto Research Center. parity Equality, state of being the same, equivalent, matching. parity bit A bit which is included in a transmission for error checking or status purposes. In telecommunications over a modem, most protocols allow the use of a parity bit appended to a data stream of a specified length, the parity bit set to zero or one, depending upon the preceding data. Parity values calculated and stored as the sent bits are checked against parity values calculated from the received bits. See parity checking. parity checking A simple means of checking data integrity after a transmission by comparing the calculated value of the parity at the receiving end with the value calculated and stored at the sending end. Parity checking is very commonly used in file transfer through modems over phone lines. First the transmitting and receiving ends negotiate a common protocol, for example, ZModem, then the parity setting is selected as odd or even (or none). Assume a parity setting of even for this example. Parity is calculated prior to sending, by tallying the ones or zeros in a group of bits (usually seven), and then assigning a parity value of zero if there is an even number of one bits and of one if there is an odd number of one bits, (or the converse, by looking at zero bits for odd parity). The sender transmits the data and its associated parity bit. The receiver calculates the parity of the received bits and checks to see if there is a match with the transmitted parity bit. If not, there is a problem. The system is not foolproof; a match does not guarantee that the data were correctly transmitted, as the parity bit itself may have become altered along with the data, but mechanisms in most software evaluate the frequency of parity errors so that the user may be alerted and the transmission aborted, restarted

from an earlier point, or resumed later, depending upon the protocol. park drive In hard drives, “parking” the drive is a means to secure any moving mechanisms which may be damaged by being jiggled in transit. Some hard drives park automatically when not in use, and some use mechanisms which do not cause damage if the unit is transported (e.g., drives in laptops). Older drives were often equipped with software-parking, and it was quite important to run the software command to park the drive before moving the system or removing the drive. This system is now uncommon. Mobile computers are equipped with self-parking drives. park phone In telephony, parking is the process of putting a line through to a particular phone so that it can be picked up at another station, or to put a line on “soft hold” so the conversation can be continued from another phone. park timeout In telephony, a time limit on a parked line after which it hangs up the line if the call is not resumed on another line (or the same line). parking 1. In telephony, parking is the process of putting a line through to a particular phone so that it can be picked up at another station, or putting a line on “soft hold” so the conversation can be continued from another phone. 2. In computing, the process of securing a device so that any moving parts that might be damaged or that might damage other components are kept in check. For example, the read/write head of a hard disk drive could damage the head and the magnetic media if it skitters across the drive when it is moved. Parking the drive through software or builtin electronic sensors ensures that this type of damage doesn’t occur. Depending upon the operating system and type of drive, a drive may have to be unparked or mounted after it has been parked. Older OSs and drives tend not to be auto-parking. It may be necessary to run a software utility to park the drive when powering down the system to remove the drive or to move the computer system. 3. In general consumer electronics, the process of tying down, bolting, or otherwise securing moving parts so they are not damaged or do not cause damage in transit. It is very common for laserdisc and compact disc players to have a transit bolt in the back to prevent the trays from moving around during shipment. Always take care to remove the transit bolt before use, save it by taping it to the manual or the underneath of the player, and always reinsert the same bolt (the length may be important) before moving the equipment, especially if it is being shipped by a third party. Parkinson’s law C. Northcote Parkinson wrote in the 1950s that work expands to fill the time available for its completion. (For those who are perfectionists, and believe that if a job is worth doing, it’s worth doing right, this is doubly true.) partial response/maximum likelihood PRML. PRML is a means of digitally encoding analog data and reconstructing it. This concept can be applied to many aspects of technology but has been particularly useful in the development of improved data broadcasting and storage devices.

PRML-technology hard drives, for example, can provide high disc capacities and faster transfer rates than earlier technologies based on peak detection (the detection of voltage spikes resulting from magnetic flux reversals). Peak voltages become harder to detect as data are more densely packed (the peaks become difficult to distinguish from the noise). To overcome this problem, a new approach, based on digitally sampling the analog signal, was developed. Vendors like Seagate have applied a PRML digital sampling and data reconstruction approach to the development of high-capacity drives that use partial response (PR) in magnetoresistive (MR) hard drive heads. These heads detect and sample an analog signal prior to Viterbi detection decoding. Together, PR and MR eliminate overhead in the electronic equalization (undershoot filtering) process, freeing up as much as an additional storage space. Maximum likelihood (ML) is used in the conversion of analog waveforms into digital data. Through Viterbi detection, all possible combinations of data are checked for the best match of least error with the incoming data. The assumption is that the least error pattern will most likely be correct and, in practice, it works quite well. Together PR and ML enable faster data transfer rates through run length limited (RLL) coding and significant areal density increases over peak detection methods are possible. As PRML technology caught on and was adopted by a number of vendors, the algorithms and underlying technology were improved to the point where the higher performance versions were called extended partial response/maximum likelihood (EPRML) to reflect further significant improvements over the earlier PRML drives. See Super DLTtape. partition Subset, class, section, or division. partition, drive On hard drives, a usually contiguous section of a disk individually initialized and handled by the operating system as a distinct unit. Some systems can format the individual partitions in a variety of formats, i.e., a 1-Gbyte hard drive with a NeXTStep 400-Mbyte volume on one partition, a 400-Mbyte Linux volume on another, and a 200Mbyte Macintosh volume on a third, all recognized by the OS and readable/writable without any unusual technical expertise or demands upon the user. On many microcomputer operating systems, disk volumes and files cannot cross partitions, but many Unix and workstation operating systems can handle volumes that cross partitions transparently to the user, e.g., two 500-Mbyte hard drives used together might appear to the user as a 1-Gbyte virtual drive. There are many schools of thought as to whether a hard drive needs to be partitioned. A few operating systems can only handle up to four partitions, each with up to 2 Gbytes of space and, consequently, a larger hard drive must be sectioned into smaller pieces in order to be handled by the operating system. Others don’t have this limitation on the number of partitions, and can manage larger-sized partitions. In terms of disk management, in the case of problems, it may be easier to rebuild partitions or handle data recovery procedures, if there are several partitions rather than

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just one. Redundant array drives are another way of handling error recovery. Often a small 200- to 500Mbyte partition will be set aside as a “swap drive” and not used for other purposes. See RAID. partition, memory In computer memory, a linked or contiguous section, separate from other sections, that is allocated for a specific purpose or process, such as video display or frame buffering. partly perforated tape See chadless tape, paper tape. party 1. One of the individuals in a transaction. A common legal term used to stipulate an individual or organizational entity. To be party to a transaction is to listen in or participate. In telecommunications, the transaction might be a telephone call, a conversation, or a computer communication. 2. Two or more individuals engaged in a group activity, especially a social activity (e.g., celebrating after completing a very long writing project). party line In telephony, a line shared by two or more subscribers, so if one or more subscribers pick up the line and listen when someone else is engaged in the call, they can hear the conversation, and can’t make further calls until the current conversation is disconnected. Party lines were very common on older shared phone circuits until the 1960s; they are now uncommon in North America. On ISDN lines and Frame Relay networks, a sort of party line system exists, but is rarely a hindrance to the user, unless too many subscribers are assigned to the line. party line, following Following the party line is a phrase from politics that indicates acceptance and promotion of the administration’s point of view. The administration might be a political party, a business entity, or other institution. It is sometimes used as a derogatory phrase for ambitious compliance, or for a person who doesn’t think for him- or herself, but promotes the current popular point of view. PAS See Priority Access Service. pascal An SI unit of pressure equal to one newton per square meter. Pascal A programming language descended from ALGOL, developed by Niklaus Wirth in 1970. Pascal became especially popular in the 1980s for teaching programming concepts and techniques. A structured, typed language, Pascal is somewhat similar to Modula II, and fits somewhere between C and higher level languages like BASIC and FORTRAN. It is less cryptic than C, but also less preferred by programmers in commercial development environments, yet is generally preferred over the less structured BASIC in educational environments. See Modula II, C. Pascal, Blaise (1623-1662) A talented French inventor and mathematician, Pascal devised one of the earliest calculators, a “Pascaline,” while still in his teens. It was a numerical base ten, movable dial, wheel calculator designed to assist his father in carrying out his duties as a tax collector. Pascal appears to have come up with the design independently, and probably was not aware of the earlier calculator developed by Schickard at about the time of Pascal’s birth. Pascal also did research in fluid dynamics. See Schickard, Wilhelm.

pass through v. To move through a component device or leg of a network without significantly altering the characteristics of that which has just been passed through, or without being altered by that which is passed through. See passthrough device, tunneling. passband The range of transmissions frequencies which can pass through a filter without a significant decrease in amplitude (attenuation). A passband filter allows selective screening out of irrelevant or undesired frequencies in order to create a device for a specific purpose, or to simplify its operation. passband A signal which poses no spectral energy at direct currents (DC), unlike a baseband signal. A Manchester-encoded signal is one example of a passband signal. passthrough device 1. A device chained between two other devices, which passes data through without changing them. For example, an external memory module might be attached to a computer, with an external hard drive attached to the memory module. The memory module passes through the hard drive signals in such a way that the hard drive works just as though it were directly attached to the computer. See daisy chain. 2. A device that provides access to and passes back the signals transmitted by another. Sometimes used as a diagnostic tool. password A word or combination of characters which, when provided by a person or entity wishing to gain entry to a system or situation, is checked against certain characteristics, or a list of those who are authorized to have access. If a match is found, entry is permitted. Password protection systems are very common on computers and networks. It is very unwise to tape passwords to monitors or desks where anyone can see them. It is also unwise to use common words as passwords; a moderately long password with a combination of letters and symbols is safer. See anonymous FTP, back door, back porch. patch v. To connect one circuit with another, usually through an intermediate line. For example, on old telephone switchboards, the operator would patch through a call by taking a jack connected at the other end to the main switchboard, and plugging it into the phone receptacle for the individual getting the call. A patch is a temporary connection, one subject to frequent change or used for diagnostic purposes. patch, software n. In software, a patch is a piece of code that is inserted into the original code to override some of the original programming, or to add capabilities or data which weren’t in the original code and perhaps should have been. A patch is distinguished from an upgrade in that it typically is intended to correct oversights or errors, whereas an upgrade is usually of greater scope, intended to enhance or extend the capabilities of the program. In many products, the two are combined. patch, sound In electronic music, a sampled segment of sound stored digitally. The sound is measured and recorded, that is, “quantized,” at rapid intervals in order to create a digital impression of the analog sound wave. For the most part, the more frequent the sampling, up to the limits of human perception, the more

true to the original the sample tends to sound (the capabilities of the playback mechanism contribute as well). Sound patches can be generated by and used with many commercial sound synthesizers and computer synthesizer software. MIDI is a common protocol used in the music industry for communicating digitized sound between MIDI-compatible instruments and software programs. Speech and music sound patches are often used to enhance multimedia CD-ROM educational and entertainment products. More recently, messages composed from speech patches are becoming common on the Web. See quantize, sampling. patch bay, patch board A hardware panel designed with connections which can be easily changed. In other words, it is set up so that temporary circuits, or those which are frequently changed, can easily be rewired. Patch bays are often equipped with wheels, and usually have receptacles or terminals for easy insertion and removal of patch cords and/or wires. Patch boards are useful for prototyping, monitoring, and testing new circuit layouts. See patch panel. patch cord A short length of wire or cable used to connect circuits. The connectors at either end vary, but are often RCA jacks or BNC connectors. Patch cords are commonly used with patch bays, patch panels, and electronics components. Videographers and musicians often refer to video and audio connecting cables as patch cords, since video equipment connections are frequently reconfigured. patch panel A hardware device, often wall-mounted, that facilitates the connection and reconfiguration of temporary circuits. A patch panel may resemble a distribution frame, in that it has a grid of openings or connectors through which circuits can be routed. It commonly has mounted receptacles to match the types of jacks used in that particular circuit. patent A registration process formally established in the United States in April 1790 which provides a record of the ownership, development, and date and method of creation of unique products and processes. The first American patent was granted on 31 July 1790. By 1802, applications had increased to the point where a separate Patent Office was set up, and more rigorous scrutiny was established by 1836. In the United States, the documents are processed and stored in a central government repository that is open to the public and intended to further technological progress by the encouragement of the dissemination of ideas. Japanese patents have been available over networks for some time now, and recent U.S. patents are now searchable on the Web through the U.S. Patent and Trademark Office site. The Clinton Administration announced on June 25, 1998 that over 20 million pages of patent and trademark information would be provided free to the public on the Internet by year’s end. Content is supplied through the Commerce Department’s large database of text and images. The collection will include the full text of 2 million patents dating from 1976, 800,000 trademarks and 300,000 pending registrations dating from the 1800s. Images will follow, with low and medium resolution images available for printing with Web

browsers, and high quality print copies available by order. Patent applications must follow very specific format and content guidelines laid out by the patent office. Patent registration grants exclusive intellectual and certain commercialization protections to the inventor for a term of 17 years in the U.S. (international patents are similar). In cases of others coming up with the same idea simultaneously or previously, without knowledge that the idea has been patented, preference for the idea now goes to the inventor who first is granted the patent. This is a change from historical procedures in which an earlier inventor, if she or he had documents to prove the case, could have a patent from a later inventor overturned. Many people incorrectly assume that the patent process exists to explicitly prevent others from infringing on patents, but it is the responsibility of the patent owners, not the patent office, to police the use and abuse of patented ideas. The patent does, however, define the nature and extent of the legal protection available to the inventor through the justice system. Granting of a patent does not include granting of a right to manufacture a product incorporating the idea, since other patents for other aspects of the invention may exist. The most important aspect of the patent and the submission of patent applications is the Claims section, in which the inventor lays out, in point form, the characteristics which make the invention unique and nonobvious. Some or all of these claims may be accepted by the patent office, and the document is critiqued and rejected or returned to the applicant for revisions. Since uniqueness is often evaluated in a historical context in the Prior Art section, historical antecedents and current similar inventions must be described by the applicant thoroughly and succinctly. The invention must also be more than a half-baked idea, since the patent application must include a clear description of how to build or otherwise recreate the invention itself, without undue difficulty to a layperson or someone appropriately skilled in the area of specialization appropriate to a specialized invention. Hardware patents usually fall under the products category and software patents under the process category. Note that patents, copyrights, and other legal registration procedures may grant ownership to the employer of the inventor rather than the inventor, if the employee undertook the invention in the course of his or her normal work hours or duties. One of the most famous patent clerks in history was Albert Einstein, who worked as a junior clerk in the Swiss Patent Office when unable to find work as a teacher or research scientist. While working there, he wrote some of his most startling, insightful treatises on relativity. See copyright, trademark. http://www.uspto.gov/ Paterson, Tim Paterson developed a historic disk operating system for Seattle Computer Products in the late 1970s. The product was derived from Gary Kildall’s CP/M operating system, which was the most successful and well known at the time, with over half

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a million copies distributed. Paterson created a basic operating system called QDOS (Quick and Dirty Operating System) which he has stated was derived in part from the program interface described in a CPM manual from the mid-1970s. Microsoft bought it, fixed it up a little, and provided it to IBM soon after. IBM released it initially as PC DOS 1.0. Meanwhile, Seattle Computer Products retained the rights to QDOS. Microsoft subsequently bought out all QDOS distribution rights for $50,000. The Microsoft financial empire essentially sprung from this transaction as the product was developed into MSDOS and, eventually, after many facelifts and enhancements, evolved into Windows. See Digital Research; Kildall, Gary; Microsoft Corporation. path A route, track, directional identifier, runway, conduit, or other end-to-end, hop-to-hop, or as-yougo means of delineating the track followed by a person, process, transmission, or data unit while traveling from one point, node, or endpoint to another. A file path is one which indicates the hierarchical organization and location of a specific file or grouping of files. A transmissions path is the specific or general direction of radiant energy travel. path information unit PIU. In packet networking, a message unit which consists of a transmission header (TM) or a transmission header combined with a following basic information unit (BIU) or segment. See datagram. Path Terminating Element See SONET path terminating element. pattern matching, pattern recognition The process of comparing text, symbols, images, or other elements to determine whether they are the same, similar, or mathematically equal. The process of pattern matching is widely used in database search and analysis mechanisms, and its cousin, pattern recognition, is common to artificial intelligence applications including expert systems, robotics, and others. Pattern recognition was in its infancy in the late 1950s and early 1960s, when computing systems were expensive, cumbersome, and programmed with punch cards. Nevertheless, early researchers at the time, sensing its potential, developed equipment and algorithms which could read a few handwritten letters, if they were plainly written. See Perceptrons. pay phone, pay telephone See payphone. payload The user information, and sometimes accounting and network administration information, carried in the upper layers in a layered architecture, within a cell, frame, packet, or other network data transmission unit. Separate from but associated with the payload, there is frequently signaling, header, error checking, and other data which relate more to the type and manner of transmission than to the information content from the user or process sending the transmission. Payload Data Segment PDS. In communications satellites, the data services that are made available to authorized users. See Unified User Interface. Payment Extension Protocol PEP. An HTTP payment extension protocol described by the JEPI

project in August 1996 in conjunction with seven examples of the Universal Payment Preamble (UPP) that could be used over PEP. The purpose of the system was to develop a practical, automatable payment system for running over the widely distributed HTTP applications on the Web. PEP enables UPP to be embedded in HTTP to support Web client/server payment transactions. Examples of basic payment mechanisms include queries to determine what types of payment forms are supported, presentation of payment options, demand payment options, payment acceptance/rejection, and payment option queries. See e-commerce, JEPI, Universal Payment Preamble. payphone, paystation phone Any self-contained public or private telephone unit which requires a percall or per-minute fee, usually directly transacted with the phone, although some human-operated stations exist. The first pay telephones were attended by operators who collected the fees for the calls.

Coin payphones have in many ways remained unchanged from their historical antecedents in the 1800s. Most now employ a single slot, and credit card/calling card slots are being added as older coin-only phones are gradually replaced.

payphone history One of the early coin box patents was issued in 1885, and William Gray installed a public coin phone in Connecticut in 1889 while employed by Pratt & Whitney. He later founded the Gray Telephone Pay Station Company with George A. Long, and together they filed additional patents for payphone technology, establishing a strong hold on the market. The first payphones were actually human-attended pay stations. The Social Telegraphy Association charged 15 cents per call in 1878. In 1880, pay stations began to be established in New York, and a pay station was announced by the Connecticut Telephone

Company for 10 cents per call, which is interesting since the reduction in price of the technology and wider distribution of payphones over the next century meant that calls in the 1960s were still only 10 cents each. In Europe, payphones were beginning to appear by the early 1900s. Since the early attended stations were not as profitable as automated stations, there was a lot of economic incentive to find an automated way to collect the money. This also made it easier to provide service 24 hours a day. While there were many incremental improvements, like the change from three slots to one in the mid1960s, payphones did not change significantly until the 1980s, when calling card and credit card mechanisms were added to selected stations. By the 1990s, in the United States, Canada, and Western Europe, card-reading payphones were common. payphone postpay Payphone calls which are paid after completion, usually with a calling card or credit card. payphone, private Also known as COCOT, this is a customer-owned coin-operated phone, as might be found in a hotel lobby or tavern. COCOTs may provide only limited access to long-distance carriers. PBX Private Branch Exchange. See Private Automatic Branch Exchange. PC 1. personal computer. While many people use PC to refer specifically to IBM and third-party licensed hardware, in fact, PC correctly refers not only to Intel/ IBM computers, but also to any personal computer or microcomputer priced in a consumer or small business price range. 2. printed circuit. See printed circuit board. 3. program counter. 4. protocol control. PC card See PCMCIA card. PC Pursuit A commercial Telnet dialup service that was very popular in the 1980s for accessing Internet Service Providers in distant cities. PC Pursuit allowed users to connect with any PC Pursuit-supported city for a low monthly charge, and dial out a call from there to anywhere in the local dialing area. PC, IBM/Intel colloq. In general and marketing terms, PC is understood as a subset of personal computers, consisting of Intel-based IBM hardware, or third-party licensed hardware, running the IBM OS/2 software or, more commonly, running the Microsoft Windows graphical operating environment in conjunction with MS-DOS. For information on specific IBM desktop computers, see the listings under IBM Personal Computers. PC-AT See IBM Personal Computer AT. PC-XT See IBM Personal Computer XT. PCA 1. point of closest approach. In a satellite communications system, a point on a segment of the orbit or ground track when the satellite is closest to a specific ground station. 2. Premises Cabling Association. 3. protective connecting arrangement. Commercial connecting rental agreement, required by AT&T/Bell prior to divestiture for telecommunications devices that were not AT&T/Bell, were connected to the AT&T/Bell system. See Carterfone decision.

PCB 1. power control box. 2. process control block. 3. See printed circuit board. 4. protocol control block. PCCA See Portable Computer and Communications Association. PCI 1. See Peripheral Connect Interface. 2. Protocol Control Information. PCIA Personal Communications Industry Association. Formerly known as Telocator, PCIA is a national association representing the mobile communications industry. PCjr See IBM PCjr. PCL See printer control language. PCM 1. See phase conjugation mirror. 2. See pulse code modulation. PCMCIA Personal Computer Memory Card Interface Association. A professional association of electronics peripherals and semiconductor manufacturers and software engineers. See PCMCIA card, PCMCIA standards. PCMCIA card, PC card A standardized computer peripheral card format, not much bigger than a fat wallet card, which is commonly used in portable computing applications. PCMCIA cards (since the mid-1990s called PC cards because it’s easier to say) are microminiaturized devices with a thin edge connector, including memory cards, hard drive cards, fax/modem cards, network interface hookups, and more. They are used in radio phones, laptop and palmtop computers, digital cameras and camcorders, and various other portable electronic devices. The most common cards are called Type I or Type II (Type III is less common, and Type IV is vendor-specific). Most laptop peripherals use Type II cards, and it pays to have at least one Type II slot on a portable computer. Hard drives and radio devices tend to use the thicker Type III cards. PCMCIA standards A set of 8-bit bus standards which bears the same name as the organization which developed the standards, the Personal Computer Memory Card Interface Association. PCMCIA standards were developed and tested in the late 1980s and released for general use in 1991. While there is fairly good adherence to the standards, compatibility is not absolute. It’s advisable to try cards before buying them, or to get them with a good return policy. The set of standards includes Type I, Type II, Type III, and Type IV. See PCMCIA card. PCMIA Personal Computer Manufacturer Interface Adaptor. PCN See Personal Communication Network. PCO See Private Cable Operator. PCP 1. See Predictor Compression Protocol. 2. Private Carrier Paging. PCR 1. See peak cell rate. 2. See phase change rewritable. 3. problem/change report. 4. See processor configuration register. 5. See Program Clock Reference. PCS 1. See Personal Communications Service. 2. personal communications software. PD See phase drive. PDA See PDA microbrowser, PDA macrobrowser, Personal Digital Assistant.

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PDA macrobrowser A software application providing full Web compatibility on limited-resource portable devices through quick conversion and display algorithms transparent to users, Web page designers, and security providers. Macrobrowsers include display software technology installed on a Personal Digital Assistant (PDA) working in conjunction with a proxy server. Thus, unlike microbrowsers, information providers don’t have to maintain two sets of Web pages or a separate type of digital certificate – a macrobrowser supports the existing Web infrastructure. Macrobrowsers began appearing in 2001 as PDAs with better memory and display technologies were released. They will likely co-exist with microbrowsers for a while, but may supersede them due to the improving power and resolution of handheld wireless devices and the relative ease of implementing Web pages and security features compatible with macrobrowser-enabled devices. See PDA microbrowser, SoftSource, Wireless Application Protocol.

A full color, graphics-capable Palm personal digital assistant (PDA) connected via radio link to the Internet and installed with the innovative SoftSource/ Catarra HTML-compatible macrobrowser client, which enables the same full-featured Web surfing as a desktop computer, with a pen to scroll, click, enlarge, or carry out other typical browser actions. This fully HTML-compatible combination of hardware and software has many advantages over more limited microbrowsers and WAP technologies, including the convenience of accessing standard Web pages and security features rather than requiring special software designed for WAP-based devices. WAP is appropriate for limited resource devices, but for full Web browsing, the SoftSource/Catarra server/client combination is currently the only product to bring unrestricted graphical Web-surfing to PDA mobile devices.

PDA microbrowser A software application designed to provide limited Web access compatibility for constrained-resource devices. Microbrowsers began to appear on the market in 1999. In general, they implement limited-set, proprietary, or specialized adaptations of current Web browsing languages to run effectively on Personal Digital Assistant (PDA) devices with limited memory and display resolutions. The

most common strategy for microbrowsers is to run a Web proxy gateway and to adapt Web pages to the limited-set languages compatible with these devices, through simplified/specialized markup languages. Microbrowsers are a reasonable way to support constrained-environment handheld computing devices, but put an extra burden of time and expense on Web page designers, programmers, and security providers, as two sets of Web pages and digital certificates must be maintained if microbrowsers and regular HTML browsers are to be supported on the same Web site. Microbrowsers will remain viable for a while for limited-resource devices but may eventually be superseded by PDA macrobrowsers for general purpose browsing, as handheld devices become more powerful and feature-rich. See CHTML, PDA macrobrowser, Personal Digital Assistant, WAP Forum. PDC See Personal Digital Cellular. PDF See Portable Document Format. PDL See page description language. PDP 1. See plasma display panel. 2. See power distribution panel. PDP- A series of Digital Equipment Corporation (DEC) Programmed Data Processors (PDPs) that would today be called minicomputers. Right from the beginning, the PDP-x series filled a need for powerful, smaller-scale, lower-cost computers. The PDP-1 sold for only a tenth of the price of many computer behemoth mainframes. This made the PDP- line marketable to educational institutions and businesses that couldn’t afford million-dollar computing systems and they became very popular with computer science students, with many user (and hacker) groups springing up around the machines. DEC’s first computer, the 18-bit PDP-1 was released in 1960 and a PDP-3 was built by a DEC client. The PDP-4 and PDP-5 followed in 1962 and 1963 and DEC released about one a year from then on. By the mid-1960s, DEC had launched a desktop model of the PDP-8. To be useful, it needed lots of peripherals, and its price was far beyond the range of personal computer owners, but for under $20,000, it was a transitional machine to the smaller scale mini- and, eventually, desktop computers of the late 1970s and beyond. By the early 1970s, the series was up to the PDP-16, but many purchasers were still using PDP-8, PDP-10, and PDP-11 machines into the 1980s. The PDP-x series was gradually superseded by DEC’s VAX computers in the mid-1980s, but hobbyists still like to pick up the PDP-x computers at auctions and computer salvages. See VAX. PDS See Payload Data Segment. PDU See Protocol Data Unit. PDUS Primary Data User Station. The combination of a ground station and a satellite image processing system. PE processing element. peak cell rate PCR. In ATM networking, a traffic flow measure that describes the upper cell rate limit, which may not be exceeded by the sender. See cell rate. peek/poke Higher level language instructions, generally found in BASIC, which allow the programmer to examine (peek) the contents of a specified area of

memory or insert (poke) data into a specified area of memory. This was often used by BASIC programmers to manipulate data directly on early microcomputers, such as the TRS-80, to speed up interpreted BASIC programs, or to carry out operations which were not directly supported by the BASIC instruction set. Peek is a safe operation, but poke should always be handled with deference and care, since poking information directly into memory may interfere with subsequent running of the software, or may immediately overwrite something crucial and crash the system. peer entities In layer-oriented network models, entities within the same layer, usually diagramed and visualized as horizontally related. peer model A networking model built with the assumption that internetwork layer addresses can be mapped onto ATM addresses, and vice versa, and reachability information between ATM routing and internetwork layer routing can be exchanged. See integrated model. peering The voluntary exchange of routing announcements in order to effectively establish data paths among providers. PEG Regulated Public, Educational or Government access. See cable access. Pel See picture element. Pender, John (ca. 1860-1896) A British merchant who succeeded in establishing ambitious historic telegraph cable links between Western Europe and the Far East and Australia. In 1856, John Pender became a director in the Atlantic Telegraph Company and thus was involved in the first transatlantic cable enterprise speerheaded by Cyrus W. Field. Pender’s subsequent ventures indicate that he was inspired by the success of the Atlantic telegraph cable installation and its future economic impact. Wanting to get in on the ground floor of the new industry, in 1864, Pender formed the Telegraph Construction and Maintenance Company (Telcon), foreseeing the future need for cable manufacture and maintenance. Not satisfied with this alone, however, he then founded the British Indian Submarine Telegraph Company, in 1869, with the goal of linking Britain and India. For building the local Falmouth link, Pender formed the Falmouth-Gibralter-Malta Telegraph Company but soon changed it to the more generic Eastern Telegraph Company as plans and locations changed as the project advanced and the port location was changed to Porthcurnow (later Porthcurno – PK). By 1879 Pender was not only a significant telecommunications magnate, but had realized the remarkable feat of building a telegraph cable link between London, England, and Bombay, India. In 1882, Douro mail steamer and passenger ship sank off Cape Finisterre following a collision with a Spanish steamer. The John Pender telegraph ship, part of Eastern Telegraph’s fleet, was nearby and took off a number of passengers, providing them with basic needs and enabling them to telegraph their loved ones with reassurances. See Field, Cyrus West; Porthcurno. pendulum A suspended object which, when stimulated into an unimpeded swing, will oscillate in regular,

predictable patterns related to the plane of the oscillation and the movement of the Earth. The most celebrated experiments with pendulums are those of Foucault in the 1800s in which he studied the behavior of large pendulums on very long lines, over 200 ft. long. These were suspended so as to inscribe a pattern in sand at the lowest point of the pendulum. As Foucault’s immense pendulum moved, the pattern changed, becoming the first tangible rather than theoretical evidence of the movement of the Earth. penetration Gaining access to a system, circuit, facility, or operation, usually for security reasons or unlawful access. Physical penetration of circuits or networks can be done through means of taps or black boxes. Logical penetration can be done through password-guessing, Trojan horses, viruses, and back doors. Bodily penetration can be done through overriding electronic security measures, entering as an impostor, or using insider privileged access in an unethical manner. See back door, Trojan horse. penetration tap 1. Any means by which a conductor is accessed by piercing the outer layers of shielding and grounding and connecting to the current circuit, with the intention of not disrupting current transmissions. 2. A network connection technique which enables devices to be attached to the network cable without interrupting current network operation. The tap is carried out with a sharp tool which can pierce the outer and inner ground shielding of the network cable, such as a coaxial cable commonly used in Ethernet implementations. penetration testing Testing a system for the integrity of its security. This is sometimes done by internal staff, contractors installing the security measures, or outside experts hired to try to penetrate the system. In the telephone and computing worlds, known “hackers” are sometimes hired to try to penetrate a system to try to identify security holes before the system is opened up to employees or the public, depending upon its nature. In 1998 it was found that cash cards, which were generally considered reasonably safe from decryption and unauthorized use, could be penetrated by measuring their electrical emanations and properties, a finding that calls into question the use of cash cards in place of traditional means of currency exchange. Pentium An Intel Corporation 80586-based central processing unit (CPU), designed to succeed the 80486, introduced in 1993. Originally released at 66 MHz clock speed, other versions came out, including a 100 MHz version with a 16-bit cache and a 64bit memory interface, and eight 32-bit general-purpose processing registers. The name is derived from the “5” in the processor line 80x86 due to a court ruling that a number cannot be trademarked. Pentium II An Intel Corporation central processing unit (CPU) similar to the Pentium Pro. Unlike the Pentium Pro, which incorporates the level 2 (L2) cache into the chip with the CPU, the Pentium II operates with a cache inserted in a slot on the motherboard, thereby increasing the amount of time it takes for the two to communicate. It also incorporates MMX circuitry intended to improve graphics and

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multimedia-related operations. Pentium MMX Pentium Multimedia Extension, Pentium Matrix Math Extension. The MMX is essentially a Pentium Pro chip enhanced with a number of new data types and floating point instructions that enhance computing-intensive operations such as graphics. Applications are becoming increasingly visual in nature, with more graphical user interfaces, image processing, rendering and raytracing, videoconferencing, realtime games, and virtual reality applications, so support for commonly executed graphics and math-intensive computing processes on the chip is intended to support these growing areas of interest. Also, by incorporating capabilities similar to those supplied by direct memory access (DSP), Intel can reduce its reliance on the DSP technologies of other vendors The Pentium MMX incorporates what Intel calls Single Instruction, Multiple Data (SIMD) techniques to allow several processes to be carried out with a single instruction. See Pentium II, reduced instruction set computing. Pentium Pro, P6 An Intel Corporation 80686 central processing unit (CPU) in the Pentium brand name line, introduced in 1995 as a successor to the Pentium processor. The Pentium Pro originally shipped as a 133-MHz CPU and shares a number of commonalities with the Pentium, including a 64-bit memory interface. It is a two-part chip in the sense that it has a CPU and a level 1 memory cache, plus a level 2 (L2) memory cache layered into the CPU rather than residing separately on the motherboard. It is a hybrid chip with an underlying RISC structure, but also includes a CISC-RISC translator for downward compatibility. The clock speed of the first version was 133-MHz, with other versions following. People’s Communication Charter A global movement by a number of international communications associations to demand the protection of the quality of communication services, their accessibility, affordability, and ease of use by the public in order to safeguard basic human rights. The Charter grew out of concerns about new and existing communication technologies conscripted around the world by selfinterested governments or allocated preferentially to private parties for use as conduits for information delivery for propaganda or for-profit ventures, at the expense of communications supporting education, community needs, and civil rights. See Milan Declaration on Communication and Human Rights. http://www.waag.org/pcc PEP 1. Packetized Ensemble Protocol. A high-speed, proprietary, full duplex transmission protocol from Telebit. It has error-correcting mechanisms and is said to handle line noise well; it is no longer in general use. 2. See Payment Extension Protocol. 3. See Public Exchange Point. PER See Packed Encoding Rules. Percent Local Usage PLU. A measure of telecommunications usage by time. PLU is a ratio of the local minutes to the sum of local and intraLATA longdistance minutes between exchange carriers, sent over Local Interconnection Trunks. Switched access

and transiting calls are not included. Perceptrons Self-organizing, pattern recognition systems built in the early 1960s at Cornell University. These systems were rudimentary, barely managing to recognize simple letters, yet studies and experiments of this kind led to the optical character recognition and handwriting recognition systems we now take for granted. At the same time, at the Massachusetts Institute of Technology (MIT), researchers were developing pattern-matching systems for medical diagnosis, with a system designed to screen for cancer cells through a microscope. See neural networks, pattern matching. Peregrinas, Peter An earlier experimenter in magnetism, Peregrinas designated the magnetic poles. He was a student of Roger Bacon, an English scientist. perforator A tool to make a hole, to penetrate a substance, to punch an opening. Common three-hole punches are perforators. Electronic perforators are widely used to turn electronic signals into code pattern holes in punch cards and paper tapes. See chad, Hollerith card, punch card. performance category See category of performance. perigee The point in an orbit nearest the gravitational center of the body being orbited. See apogee, periapsis.

The perigee is the closest point of an orbiting object to the body being orbited.

period 1. Cycle, interval of time, portion of time encompassing a distinct culture (historical period). 2. Geologic time division that is part of an era and longer than an epoch. 3. The time interval between two consecutive orbits of a satellite through a specific point (usually the perigee) in the orbit. 4. In electronics, one interval of a regular, repeating event. periodic postings Most public discussion lists on the Internet have a number of areas of general interest, guidelines for postings, and frequently answered questions collected and organized by newsgroup and discussion list administrators or volunteers. These are disseminated as periodic postings to all readers in order to bring new participants up to speed quickly and to keep repeated postings of common questions to a minimum. Peripheral Component Interconnect, Peripheral Connect Interface PCI. A very popular local bus standard developed by Intel in the early 1990s to support 32/64 bit data that was compatible with the new Pentium processors coming out at the time. It was

designed with a newer chipset, to improve on the ISAs and VLBs that were then common, and to include bus mastering (use of the system bus). Since PCI’s development, PCI slots have become common in Apple Macintosh and Intel-based IBM-licensed machines, along with upgraded versions of the VESA VL bus. The PCI Mezzanine Card (IEEE P1386.1) was designed to work with the PCI specification. peripheral device 1. A piece of equipment which is not a main component of a system, but which, when connected to that system, enhances its functionality, speed, or storage capabilities. Peripheral devices generally cannot perform useful functions unless connected to the main system. Monitors, speakers, keyboards, scanners, video cameras, and printers are examples of peripheral devices. CD-ROM drives are an exception in that some are now designed to play audio CDs even if not connected to a computer. 2. In the telephone industry peripherals may also be called outboard processors, applications processors, or adjunct processors. Peripheral Technology Group An international commercial distributor of computer connectivity products. Perl Practical extraction and reporting language. A powerful, flexible, general-purpose, interpreted scripting language (originally spelled with a lowercase “p”) developed by Larry Wall in 1986, and now extensively used for platform-independent scripting on multiple platforms on the Internet. The syntactical structure of Perl is quite remarkable (perhaps owing to Larry Wall’s expertise as a linguist); useful, powerful routines can be written in a few lines or sometimes even in a few characters. An important tool for shell scripting, Common Gateway Interface (CGI) development, and much more. When combined with Penguin, it may be a serious contender with Java for object-oriented, Web-related interface design and Automation. The Perl Journal gives practical assistance to Perl programmers. Permanent Number Portability PNP. A means by which a telecommunications subscriber can transparently maintain an existing telephone number, even if changing to a different service provider in the same locality. permanent virtual connection, permanent virtual circuit PVC. A logical communications channel (which may differ from the physical topology over which it is laid) established with the intent that it stay the same for some time. In an ATM environment, there are two types of PVCs: permanent virtual path connections (PVPCs) and permanent virtual channel connections (PVCCs). PVCs provide manually configured connections between end systems. The addressing information, Virtual Path Identifier/Virtual Channel Identifier (VPI/VCI), must be put into both devices for connectivity. 2. In Frame Relay networks, a PVC is a logical link, with network managementdefined endpoints and Class of Service (CoS). The link consists of an originating element address, data link control identifier, terminating element address, and termination data link control identifier. See RFC 1577.

permeability The porosity or penetrability of a substance. The degree to which liquids or gases can pass through a substance. Contrast with reluctance. permeability, magnetic The property of a magnetizable material that determines the degree to which it will modify the magnetic flux in a region it occupies within a magnetic field. See magnetic field. persistence 1. Perseverance, endurance, running the course, keeping on or with, tending to continue. (A quality essential to writing a reference of this magnitude, since documenting the telecommunications industry is like trying to gas up a car that’s driving away at full speed.) 2. The tendency to continue a signal, echo, electrical charge, or data transmission after the actual communication has ceased or the message part has been received. 3. In a phosphor display system, the tendency of the phosphors to continue to fluoresce after the stimulus has stopped. This may be an undesired property, causing smear, or may be a desired property, enabling the image to remain viewable while the rest of the frame is being imaged. persistence of vision A phrase that describes the way in which human visual perception “holds” an image for a brief moment, about a tenth of a second, even if the objects in the visual field have changed or moved. Thus, humans can only scan or perceive still images up to a speed of about 24 to 60 frames per second. Faster than that and they are no longer seen as still images, but as a series of moving or related images, especially if the forms in the images are closely related to the previous ones. Researchers Muensterberg and Wertheimer demonstrated in the early 1900s that this was a property of brain processing and perception more than a physical property of the retina. These characteristics of visual perception have greatly influenced the design and development of moving visual communications technologies. See frame, scan lines. Personal Communication Network PCN. See Global System for Mobile Communications for the background and technology base for PCN. PCN was developed, starting in the late 1980s, as a modified form of GSM operating in the 1800-MHz frequency band (GSM is 900 MHz). It has smaller cell sizes, requires lower power, and is optimized to handle higher density traffic than GSM, but otherwise is essentially the same. The PCN standard was finalized in 1991. It is primarily used in the United Kingdom. See Global System for Mobile Communications. Personal Communications Service. PCS. A lowpower, higher frequency, standards-based, wireless mobile communications system, operating in the 1800- and 1900-MHz range, implemented in the mid1990s. Most PCS systems are 100% digital. In contrast to cellular, which is limited to A and B carriers, PCS operates across six (A to F) carriers. In other words, cellular can be thought of as a subset of PCS in its broadest sense. Three operational categories of PCS have been defined by the Federal Communication Commission (FCC) as shown in the PCS Categories chart. In PCS, particular channels are assigned to specific cells, with provision for reuse. A channel is associated

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with one uplink and one downlink frequency. A specific number of channels is assigned to an operator’s authorized frequency block. PCS service can be installed as a centralized or distributed architecture, and supports both time and code division multiple access (TDMA, CDMA). Designed to broaden market distribution of wireless services, the system may have more limited range than traditional cellular, but the cheaper connect times and handsets may be appealing to consumers. Industry watchers are predicting steady growth in mobile communications. In Japan alone, there were more than 20 million Internet-capable PCS system subscribers by 2001. See AMPS, cellular phone, DAMPS, DCS, GSM, Personal HandyPhone Service.

PCS Categories Category

Notes

narrowband PCS

PCS operating in limited bandwidth in the 900-MHz spectrum and not suited to high speed data communications, although low-bandwidth short text messages would work. Best suited to in-building and near outside-premises use, pagers, and cordless phones.

broadband PCS

PCS in the 1.9-GHz spectrum range for better quality voice communications and higher duplex-mode data communications.

unlicensed PCS

PCS in the 1910- to 1930MHz range, suitable for inhouse and in-company systems, and small independent service providers. Limited to low-power signals.

personal computer PC. A compact, relatively lowcost computer system designed for home, school, small business, and prosumer (high-end consumer) use. The first fully assembled, affordable PC with a keyboard and CRT monitor was probably the SPHERE computer released in 1975, but it didn’t sell well. Subsequently, the Radio Shack TRS-80 series, followed closely by the Apple computers and the Commodore PET were all commercially successful. At the time of the introduction of personal computers in the mid- and late-1970s, the cost of a workstation-level computer was typically $40,000 and more, so the price tag of about $2000 to $6000 for a personal computer with useful peripherals (printer, modem, etc.) was revolutionary in terms of availability to individuals. In the early 1980s, when networks that could interconnect individual PCs began to proliferate and CPUs became more powerful, the distinction between personal computers and higher end systems

began to blur – a progression that continues to this day, with personal computers of the 1990s being more powerful than minicomputers a decade earlier and laptop computers of the 2000s being more powerful than mid-range institutional computing systems of the late 1980s. The development of PC networks also opened up hybrid systems, with PCs sharing the computing power of mainframes and mainframes using PCs as I/O devices. The term PC has been generically applied to systems used by individuals for personal, educational, and business purposes, and so does not fit the term “personal” in its strictest sense. Some people use PC to refer only to IBM-compatibles, which is not really a correct use of the term and has probably proliferated because “IBM-compatible” is such a mouthful. The distinction between a PC and a workstation is not as cut and dry as many people think. By the time you add a graphics card, sound card, CD-ROM drive, more memory, and network interface card to a personal computer, its cost is comparable to many offthe-shelf workstation-level computers. See Amiga, Atari, Intel, Macintosh, TRS-80, workstation.

The Palm Personal Digital Assistant (PDA) provides handheld mobile computing through a color graphics display resolution better than early desktop computers. Full point-and-click Web browsing capabilities (right) are provided by the SoftSource/Catarra display client/proxy server programs communicating through a wireless radio link to the Internet.

Personal Digital Assistant PDA. A handheld computerized wireless device optimized for common time-scheduling and note-taking activities that many business and personal users particularly desire. These include calendars, account keepers, note-takers, calculators, alarm signals, modem connections, databases, etc. Some PDAs support handwriting recognition through a penlike interface, others have small text keypad input screens, and some have both. The more recent PDAs have color graphics displays and the capability of full Internet browsing without the HTML and security certificate restrictions of WAP-based limited-resource instruction sets.

PDAs were introduced in the late 1980s, with penrecognition PDAs coming out in the early 1990s. Most PDAs work on batteries or AC power with a converter. Some work only with batteries. Battery life ranges from 2 to 5 hours on most systems, depending upon usage. Apple ClockWorker is an interesting evolution in PDA technology. This little 300-MHz RISC chip with 30-MBytes of RAM and 70-Mbyte memory chip outruns many full-sized desktop computers. Even more surprising is that it is powered by a clockwork mechanism developed in the U.K. Twelve turns of the AppleKey are said to provide up to 3 hours of continuous use. The idea is not entirely new; analog wound watches have existed for decades, but this is an interesting adaptation to computer technology being tested in full-sized notebook computers. See PDA macrobrowser, PDA microbrowser, SoftSource, Wireless Application Protocol. Personal Digital Cellular PDC. Formerly called Japan Digital Cellular, this is a time division multiple access (TDMA) digital cellular phone system used in Japan and, to a small extent, in the Asia-Pacific region. PDC services operate in the 800- and 1500-MHz radio frequency bands. It is an important standard due to the large number of subscribers (over 50 million) using PDC-based services. See Personal HandyPhone Service. Personal HandyPhone Service PHP. A commercial 32 Kbps mobile data Personal Communications Service (PCS) popular in Japan. PHP was established in 1995 and began providing services to subscribers in 1997. In 1998, 64 Kbps services were introduced in some areas. The PHS network can be accessed by subscribers through various Personal Digital Assistants (PDAs) and notebook computers. The PHS network is separate from or totally independent of the public switched telephone network (PSTN). Personal Identification Number PIN. A system of alphanumeric characters, usually numerals, which identifies a particular user or holder of an identification card. PINs are commonly used for credit cards, bank cards, ID cards, calling cards, and other forms of wallet-sized identification to access security doors, ATMs, phones, and vending machines. Personal Information Manager A collected group of applications, usually including an address book, time management tools, database, appointment, notes, and other similar applications or print materials used to keep track of schedules and contacts. PersonalJava applications environment See Java. Personal Wireless Telecommunications PWT. An in-building wireless telecommunications transmission standard in North America (U.S., Canada, Puerto Rico) developed in the mid-1990s. It is similar to the Digital European Cordless Telecommunications (DECT) standard in Europe. It is intended for short distance, high-bit-rate, packet-based communications. PWT uses unlicensed Personal Communications System (PCS) spectrum in the 1.9-GHz radio frequency band. Standards for the use of Frame Relay for mobile PWT-compliant devices (Project

4247) and for expanded PWT in the 1850 to 1910 and 1930 to 1990 MHz frequency bands were initiated within the TIA and EIA. Enhanced PWT uses licensed PCS spectrum. PET See Portable Earth Terminal. peta- P. A prefix for an SI unit quantity of 1015, or 1,000,000,000,000,000 – a really huge quantity. See exa-, femto-. petticoat insulator A historic utility pole electrical line insulator that still has practical use. Many historians have suggested they were developed around 1910, but it was certainly much earlier, as glass or porcelain petticoat insulators were already listed as a requirement for outside wiring in the National Electrical Code of 1899. The earliest forms were single petticoats, with double-petticoat insulators developed later. The name refers to the outer underskirt-like shape of the insulator, which has flare for channeling moisture away from electrical wires, a shape practical for both glass and non-glass insulators. Hemingray produced many glass petticoat insulators, from the post-World War II years up until the 1960s. The different petticoat skirt shapes were distinguished with letter designations. Early single petticoats were used in telephone toll lines. The base of a petticoat insulator, like petticoats themselves, can have a variety of protruding shapes. These are intended to channel moisture drops down along sharp, smooth, or corrugated points. See insulator, utility pole. PGP See Pretty Good Privacy. PGP Inc. A company jointly established by Philip Zimmermann, the developer of Pretty Good Privacy, and Jonathan Seybold. See Pretty Good Privacy; Zimmermann, Philip. PGP/MIME Pretty Good Privacy/Multipurpose Internet Mail Extensions. An IETF working group Internet messaging standard for the transmission of secure network communications. A variety of content types have been provided for MIME, and more continue to be added. Unlike S/MIME, PGP/MIME does not use public keys distributed through X.509 digital certificates. PGP can generate ASCII armor (required) or binary output for the encryption of data. The trend is for the signed portion of the message and the message body to be treated separately. PGP/ MIME can support 128-bit encryption, although not all implementations will use the full 128 bits. See S/ MIME, RFC 1847, RFC 1848, RFC 2015. phantom circuit In telephony, a means of devising an additional circuit by utilizing resources from existing circuits on either side. Thus, three circuits can be configured to prevent crosstalk and used simultaneously with only four line conductors. The use of phantom circuits has, for the most part, been superseded by a variety of multiplexing techniques. See Carty, John J. phantom group In telephony, a phantom circuit and the balanced circuits that flank it and from which it draws some of its circuitry are called a phantom group.

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phase alternate line PAL. A color television broadcast and display standard widely used in the United Kingdom and a number of European, South American, and Asian countries. The name originates from the fact that the color signal phase is inverted on alternate lines. The format was introduced in the early 1960s. It displays at 25 frames per second and can support up to 625 scan lines (not all are seen on the screen; some at the bottom may be obscured). It provides a better picture than the NTSC format prevalent in North America and is not compatible with NTSC or SECAM. PAL-M is a variation on PAL which supports 525 lines. phase change rewritable PCR. A type of high-capacity optical storage technology, developed gradually over the period from the early 1980s to the mid1990s. During the 1980s, Matsushita developed a number of PCR WORM drives, and released a read/ write drive in 1991. PCR enables multiple rewrites on the same cartridge. Using a pulsed laser diode at a higher power level, the recording surface of a disc can be changed between low reflectivity amorphous states to crystalline states, enabling data to be erased and written/ rewritten. The data can be written in one pass rather than the two passes required for a number of magneto-optical technologies. Once the technology appeared commercially promising, Matsushita developed a combination PCR/CD drive, announced in 1994, and Toshiba led a development group to adapt phase change technology for creating rewritable Digital Versatile Discs (DVDs). At first, industry adoption and standardization efforts were not broadly supported. phase conjugation A phenomenon discovered in the 1960s, phase conjugation is now a general concept used to describe a number of nonlinear optical phasing processes. Phase conjugation involves the precise reversing of the direction of the phase and propagation of a wave such that it travels back through the same path through which it originally arrived. Thus, optical phase conjugation is the precise reflection of a light beam back through its original path. Phase conjugation has many applications. It can be used in the development of tracking systems, lensless imaging technologies (e.g., holograms), and defect detection systems. It can also be used to filter a signal or to regenerate a signal that has degraded en route, which would be a boon to many types of communication transmissions. NASA/JPL is using the concept to propose designs for very fine fiber opticbased probes for imaging in tightly confined spaces. See phase conjugation mirror. phase conjugation mirror PCM. A reflecting mirror that may be used in conjunction with other mirrors in laser light beam directing systems, for example, but which is distinguished by its capability of precisely reversing the direction of a wave hitting the mirror. Contrast this with conventional mirrors, in which the direction of the reflected wave is related to the angle at which the wave hits the mirror. In addition, in a conventional mirror, only the sign of the wave vector component is changed, while in a PCM,

the entire propagated beam reverses direction and the phase of the beam is conjugated or joined together. The phase conjugation process can be enhanced, depending upon the environment in which the process is carried out. Freon has shown potential as a stable medium. In the early 1990s, photorefractive polymers were developed in IBM laboratories. Since then, layered versions have increased their usefulness for industrial purposes. New polymer-based photorefractive compounds may replace crystals for some types of PCM applications as their technology improves and the cost dramatically drops. See phase conjugation, photorefraction. phase drive PD. A type of optical data storage drive based on phase-change recording such that the optical medium can be rewritten. See change rewritable. phase jitter A particular type of undesirable aberration in which analog signals are abnormally shortened or lengthened. See jitter. phase-shift keying PSK. A type of modulation scheme which distinguishes between a binary “1” (one) and a binary “0” (zero), by changing the phase of the transmitted signal 180° if the next input unit is a binary “0” (zero). If it is binary “1” (one), then a phase shift is not executed. See frequency modulation, frequency shift keying, on/off keying, quadrature phase-shift keying. phase-locked loop PLL. A technology used in silicon-based integrated circuits (ICs), a PLL circuit controls an oscillator at a constant phase angle relative to a reference signal. The three basic aspects of a digital PLL are a controllable oscillator, a filter, and a phase detector/comparator combined within a closed-loop frequency feedback system. PLLs are useful for signal processing and synchronization applications such as controlling automatic phase adjustments in a signal. The signal can be referenced by the PLL in various ways; it can be based upon a carrier signal or linear or nonlinear baseband references. PLL was traditionally analog, but there are now also digital versions and both are suitable for various types of applications. PLL has been around for several decades; it is commonly used to synch a reference broadcast signal to the horizontal oscillator of a television receiver, for example. Because it is a basic timing technology, it is found in components ranging from voltmeters and spectrometers to cell phones and space-based tracking and synchronization systems. In communications devices, newer PLL circuits support products with higher data transfer rates, higher frequencies, and smaller footprints. Commercial dual phase-locked loop-based ICs are small, low-powerconsumption components that can offer frequencies up to 2.5 GHz (in some cases, up to 4.8 GHz), making them suitable for radio transceivers for a variety of types of products, including cellular phones and PCS. PLL ICs can also be used as secondary circuits for providing intermediate frequency radio waves that are commonly used in cell phone receivers. PLL circuits can be readily modeled in software for educational and design purposes. Java-based PLL modelers are available on the Web.

Phelps, George M. (1820-1895) An American machinist and inventor best known for his telegraphic key and printer inventions, although he also designed stock tickers (a type of specialized telegraph) and early telephone equipment. As a youth, Phelps was apprenticed as a machinist to his uncle, Jonas H. Phelps, to build scientific instruments. The Phelps and Gurley surveying instruments company evolved into Gurley Precision Instruments, which is still in business. George Phelps set up shop in 1850, in Troy, New York, and began designing and patenting a wide variety of precision electromechanical devices, including telegraph keys (e.g., a camelback key). He was known for elegance of design and superior workmanship. When approached about improving upon the popular but complex telegraphic instrument of R.E. House, Phelps joined with Jarius Dickerman to form Phelps and Dickerman and House’s Printing Telegraph Instrument Manufacturer, located in Ferry Street in Troy. Thus, Phelps built House instruments for several years. The American Telegraph Company purchased the Phelps and Dickerman holdings, retaining Phelps as a superintendent. After the American Civil War, American Telegraph was purchased by Western Union, again retaining Phelps for his knowledge and experience in the field. Western Union also acquired the patent rights to Phelps’ printing telegraph. Phelps

was assigned to work on a “harmonic telegraph,” the forerunner to the telephone, a device first patented in the U.S. by A. Graham Bell. Phelps was an associate of Thomas Edison and created some of the patent models for Edison’s early inventions. Phelps became the superintendent of Western Union Telegraph in New York and remained as a staff inventor in his later career. He may also have been associated with the Field brothers, who were instrumental in laying the first successful transatlantic telegraph cable. See Phelps Combination Printer. Phelps Combination Printer A printing telegraph system designed by George Phelps and patented in 1859 (U.S. #26,003). The device looked like a cross between a cabinet sewing machine and a tiny piano keyboard. It was based on the earlier House and Hughes telegraphs and became one of the most successful telegraph instruments in the world, particularly in North America. The 28-key keyboard enable messages to be readily typed, rather than keyed in code, which meant that any clerical worker with typing-type skills could operate the device without learning Morse Code. The key set included the 26 letters of the English alphabet plus a space key and a dot key – essentially the forerunner of a teletype machine. See House telegraph, Hughes telegraph. PHIGS Programmer’s Hierarchical Interactive Graphics System. An official standard for 3D graph-

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The 1942 Carlson patent shows the various parts of a photocopier (right), with a detail of the drum mechanism (left). Large companies were not willing to risk purchasing the new technology. A small company called Xerox did!

ics from the late 1980s. The PHIGS+ extension added sophisticated rendering of realistic looking objects on raster displays. Simple PHIGS (SPHIGS) is a powerful, display-independent subset of PHIGS which incorporates some PHIGS+ features. Phillips code A shorthand telegraphic code assembled/revised from existing systems by Walter Polk Phillips, published in 1879. Originally an American Telegraph messenger, Phillips became an accomplished press telegrapher (2731 wph) and his code was widely used for decades. See 73 (Numerals). Philmore Manufacturing Company Originally founded in 1921 as the Ajax Products Company by Philip Schwartz and Morris L. Granat, it was incorporated under the name Philmore in 1925. Philmore was the predominant manufacturer of crystal detectors and crystal detector parts used in early radio wave detection, continuing for almost 60 years. phoneme A unit of speech, considered to be the smallest distinguishable unit, which may vary from language to language and among dialects of a particular language. Phonemes are of interest to programmers for speech recognition and speech generation applications. See speech recognition. phonograph A device for reproducing sounds stored in grooves on a solid medium by means of a stylus or needle. Early phonograph recording media took many different forms, from the Edison cylinders to flat vinyl discs, which came to be known as records, and later as LPs (long-playing records) and 45s. The vibration of the stylus within the groove as the recorded medium rotated was translated into an acoustic signal and amplified through a horn on early machines, and was translated into an electrical signal and amplified electronically on later machines. One of the earliest recording devices was the phonautograph, built in 1857 by Léon Scott. It incorporated a sensitive diaphragm to move a stylus and thus record information. In 1876 and 1877, Edison did some historic experiments with recording voice on paper and later on tinfoil. Edison took the basic mechanism of a phonautograph and wrapped fine metal foil around the recording cylinder. He then spoke into a microphone as the cylinder was revolving and played back the recording by substituting a “reading” stylus for the cutting stylus. It worked, and Edison named it the Phonograph. Later, a flat rotating disc was found to be more practical than a rotating cylinder. One of the earliest examples was patented by Emile Berliner in 1888 as the Gramophone, a name which became generically associated with the technology. Basic monaural record players, essentially the same in design as modern records, emerged, although cylinders and discs competed for a little over a decade before Edison gave in and starting selling flat discs. The phonograph became very popular in the early part of the century until live radio broadcasts claimed part of the listening market. Changes from that point on focused on recording quality and playing speed, with the industry eventually standardizing on 33 1/3 revolutions per minute (rpm) in the 1970s. Phonograph records were largely

superseded by compact discs in the 1980s. Stereo sound was eventually added by taking advantage not only of the up and down movement of the stylus, but also of the left and right movement, thus allowing additional information from two sound sources to be recorded and played back, resulting in richer, more lifelike stereo sound. See compact disc, phonograph records, telegraphone.

Two historic phonographs are shown here, a GramoPhone and a Phonola, both of which relied upon acoustics for conveying the sound, whereas modern electronics provide electronic amplification through speakers. Old phonographs used sharp steel needles and heavy platters or cylinders that were recorded to be played at 70 or 78 revolutions per minute.

phonograph records A medium on which sound is stored for playback on phonograph players. Various materials have been introduced as the recording and distribution media for phonograph records, from paper and tinfoil to rubber and vinyl. The original tinfoil cylinders had a playing time of about 2 or 3 minutes. Eight years later, wax cylinders were introduced by Bell and Tainter and, in 1888, Berliner produced the first commercially successful phonograph that is essentially the same as those used today. It was a flat 7-in. rubber vulcanite disk, with lateral grooves. The earliest copies were one-sided and rotated at 70 rpm. Their capacity was about 2 minutes, roughly equivalent to the earlier Edison cylinders. By 1897, shellac records were replacing rubber vulcanite, and by 1904 double-sided records were being produced in Europe. Edison continued to provide innovations in recording and playing technology for many years, in hot competition with other inventors and historic recording companies. Materials were tried, recording times increased, and the market for audio recordings boomed. In the 1920s, electrical recordings were developed at the Bell Laboratories, making it possible for symphonic music to be recorded. Acetate coatings were developed around the same time. Long play recordings were introduced in the late 1940s, with 45s becoming popular about a year later. Records were widely used for music distribution until compact discs began to outsell records in the 1980s.

This Edison “Amberol Record” was one of the first “long play” cylinders, with a duration of 4 minutes, enough for two songs. The Edison name and image was licensed and the phonograph cylinder made and sold by the National Phonograph Company in 1909. Later, flat platters were developed, a design that was popular for the next 80 years. [Classic Concepts photo.]

Phonograph technology led to the related development of tape recorders and video cassette tapes. These media were differently shaped, but the basic recording and playing principles were similar, as was their use for consumer audio. Consumers also welcomed the increased playing times and tapes became popular and practical for car stereo systems. Phonograph use began to decline in the 1980s. Records were easily scratched, would hiss and pop on all but the very finest stereos, and didn’t have the features of the compact discs that superseded them. While records still remain as collectors’ items, the golden age of the phonograph is over, having enjoyed about 100 years of popularity. See compact disc, Graphophone, Gramophone, phonograph, telegraphone.

The historic masthead from The Talking Machine World, a monthly publication originating from Madison Avenue, New York, published between 1905 and 1928. The publication supported manufacturers and distributors of photograph and radio products. One of the articles describes Thomas A. Edison, Inc.’s intention to market a new 12-in. “long play” record that would play for 20+ minutes, more than five times longer than an average 2-in. record. The Edison Lab accomplished this by increasing the number of grooves from 150 to 450 per record. [Library of Congress, January 15, 1926; copyright expired by date.]

Photo CD Kodak Digital Science Photo CD System. An image storage and retrieval format developed by Kodak and introduced in 1992. PhotoCD is a means to store digitized still images in various resolutions on a compact disc so it can be read back from CDROM drives. It is used by many stock photo suppliers and graphic design professionals. Conventional 35mm film shot with a traditional camera can be taken to photofinishers supporting PhotoCD and developed into both pictures and digital images. At the lab, the file is scanned with a high resolution drum scanner and saved onto PhotoCD discs. If there is room, additional pictures can be added to the disc later, and read back with a multisession CD-ROM XA drive and an appropriate software driver (including Apple QuickTime Photo CD extension, SGI’s IRIX, Sun’s Solaris, IBM’s OS2/ WARP, AmigaOS 3.1, IBM AIX, etc.). A Photo CD disc can hold about 100 images, that is, about three or four rolls of film. The images are stored in Photo YCC color encoding, with multiple resolution levels. Pixel resolutions include: 2048 x 3072, 1024 x 1536, 512 x 768, 256 x 384, 128 x 192. The Photo CD Pro format also includes 4096 x 6144. See compact disc. photocopy A dry transfer replication, sometimes also called a xerograph, after Xerox, the company that popularized the technology. C.F. Carlson was awarded a patent for the technology in 1942 and failed to sell it to some of the larger business-oriented companies. But a small company called Xerox took a chance on the technology. See the Carlson patent diagram. photoelectric cell A type of sensing device activated by light and widely used in security systems, automatic lighting systems (e.g., street lights), automatic doors, etc. A photoelectric cell can be made by coating cesium on one of the electrodes in a vacuum tube. This technology was used in early television cameras. photography The art and science of registering light from objects in a scene and storing them in the form of an image. Later it became possible to produce multiples of these images by a number of means. Most photography involves capturing three-dimensional imagery in a two-dimensional format. Light is usually recorded from the visible spectrum, but there are cameras and films designed to record heat and infrared radiation which show images in a form different from the way humans perceive them, and electron microscopes record the movement of a beam of electrons. Traditional photography was developed in the early 1800s by a number of inventors including Joseph Nicephone Niepce, a French inventor, who developed a process called heliography or sun drawing, on paper coated with silver chloride. Other pioneers included Daguerré (originator of the daguerréotype), Herschel, Talbot, and Archer. One of the earliest photos was captured with silver chloride by Thomas Wedgewood in 1802. More than 150 years passed before 3D photography, in the form of holographs, became practical. Newer digital cameras can immediately

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relay an image to a computer network so the image can be viewed almost instantly at great distances from the actual scene of the event. See Daguerré, Louis Jacques Mandé; heliography. photophone A device which transmitted voice by means of light waves, invented by Alexander Graham Bell in 1880. photorefraction A phenomenon in which illumination influences the electromagnetic characteristics of a material, thus altering its index of refraction. This effect can be exploited with dual laser beams to form advanced types of holographic images. In the 1990s, polymers with photorefractive capabilities were developed in the lab. These polymers have the potential to increase the industrial applications of photorefractive technologies and, when fabricated in layers, are useful for components such as phase conjugation mirrors. See phase conjugated mirrors. photovoltaic A specialized semiconductor device which converts light into electrical energy. A basic photovoltaic cell is a slice of semiconductor material. These cells are combined into an integrated array called a panel, many of which are commonly called solar panels. A number of photovoltaic technologies such as monocrystalline silicon and polycrystalline silicon (wafers cut from silicon) are common. Photovoltaic panels are important for powering orbiting satellite transceivers and their various telemetry devices. phreaker jargon A person who seeks to access telephone services by bypassing standard procedures or acquiring technical knowledge of the system. Phreaking involves unauthorized and often unconventional methods of accessing, controlling, or subverting the public phone system. Phreaking became prevalent in the mid-1970s, when in-band telephone signaling systems enabled control of phone switching systems through tones transmitted through the wires. A second level of phone phreakers, who simply wanted to use blue boxes to steal phone services and didn’t care about the technical structure of the system, emerged in the late 1970s. Due to the increasing technical similarity between personal computer systems and the evolving public phone system in the 1980s, there was a high degree of overlap between computer hackers and phreakers. Historically, intellectual curiosity and the possibility of entrepreneurial gain from selling illegal blue boxes motivated phone phreakers, but the allure of free long-distance phone services was hard to resist and phreakers often continued their activities far beyond learning about the system, repeating many of the same arguments used to justify software piracy. Popularly, phone phreakers were assumed to be high school and college students but phone company studies revealed that about half of blue box users were business executives, doctors, and other working professionals. The evolution of the phone system from in-band to out-of-band signaling greatly reduced the incidence of phone phreaking, as did the increase in the use of Internet email for long-distance communications. Phreaking has largely returned to being a subculture

of technologically curious individuals, although theft of phone services still occurs. Phrack is a publication devoted to the dissemination of in-depth information for phone phreakers and telephone technology devotees. It began in November 1985 as an effort to pool the combined knowledge of hackers and phone crackers. The Hacker Crackdown by Bruce Sterling documents some of the history of phreakers and hackers. See blue box, cracker, hacker, in-band signaling. PHS See Personal HandyPhone Service. Physical Layer Convergence Procedure PLCP. A networking convergence procedure commonly used in Distributed Queue Dual Bus (DQDB). physical layer signaling PLS. In layer-oriented network architectures, a way to transfer information from the physical interface components to the communications channel. In some standards, the PLS is treated as a specific signaling sublayer of the physical layer. pica In typography, a unit of measurement applied to graphic elements and to linear measures of type size and composition. 6 picas = 1inch and 12 points = 1 pica. See em, point size. Pickard, Greenleaf Whittier A scientist who followed up on the observations of Karl Ferdinand Braun by testing hundreds of natural and synthetic substances for their conductivity. Braun had observed that some substances conducted radiant energy in one direction, inhibiting the backward return of a wave. Pickard researched these properties more closely, examining substances that exhibited this property, and to what degree they did so. In the course of his research, he found more than 200 substances which, in conjunction with a metal contact, could detect radio waves. This led to the development of an early form of radio component called a crystal detector, which was first marketed in 1906 and patented by Pickard in 1908. See crystal detector. pico- A prefix for an SI unit quantity of 10-12, or 0.000 000 000 001 or one trillionth of – it’s a very tiny quantity. See tera-, femto-. picocell A limited-reach wireless services base station with low output, intended to serve a very limited area, such as a single building or industrial yard. PICS See Platform for Internet Content Selection. pictographs Images dating back about 30,000 years painted by humans on stones with natural dyes which have retained their shapes and some of their colors to this day. Along with petroglyphs (rock carvings), they are the first known examples of the “publishing” of human thoughts and events. In a poetic sense, pictographs have tele (far) communicated over great distances of time. picture element PEL. The smallest individual unit that can be addressed and controlled on a computer video display. Picturephone A pioneer videoconferencing system developed by AT&T Bell Laboratories. It has been decades since the development of the first prototype Picturephone system; it was not practical

to introduce it to the public until 1970 and, even then, the technology, while appealing, was too expensive and cumbersome for consumer distribution. Since then the Picturephone concept has been refined to take advantage of advances in technology, and competing products have been developed to provide a number of practical videoconferencing options to businesses and individual consumers. Picturephone Meeting Service PMS. An AT&T service that combined TV and voice transmissions to provide a means to carry out audiographics conferences. It was a little before its time and generally expensive, and there is now a lot of competition for videoconferencing technologies. See audiographics, Picturephone. PictureTel Live 100 A commercial, standards-based microcomputer videoconferencing system designed to work with Microsoft Windows 95. It provides six transmission speeds up to a maximum of 384 Kbps. Three ISDN telephone lines are required to operate the system. piezoelectricity A form of electricity or electromagnetic polarity that arises from pressure, especially in crystalline substances. For example, compressing or twisting a quartz crystal causes its ends to assume opposite charges. The charge itself is not different from other charges; the name is descriptive of the manner in which it arises. A basic condenser can be constructed using a quartz crystal slice sandwiched between thin plates of metal foil. The vibrational interval of a quartz crystal is so constant that it is used for very fine clocks and to stabilize broadcast waves. See lap, quartz, Y-cut. pike poles Long poles with spikes on the end which aid in erecting tall poles, masts, antennas, utility poles, and other tall narrow extensions which are frequently used to hold transmission wires. These are sometimes called boom poles, and their users boomers. PIN See Personal Identification Number. pincushion distortion A type of visual aberration in which the outer corners of an image are stretched outward and the centers between the corners curve in. The opposite of pincushion distortion is barrel distortion. See keystoning. ping packet internet groper. In data communications, a software utility which employs an echo to detect the presence of another system and any delay which might be occurring in the connection. Often used as a diagnostic tool in conjunction with traceroute. Here is some sample output from ping, interrupted after three status outputs to the screen: PING othercomputer: 56 data bytes 64 bytes from 192.42.172.20: icmp_seq=0. time=14. ms 64 bytes from 192.42.172.20: icmp_seq=1. time=2. ms 64 bytes from 192.42.172.20: icmp_seq=2. time=1. ms ^C ——othercomputer PING Statistics—— 3 packets transmitted, 3 packets received, 0% packet loss round-trip (ms) min/avg/max = 1/5/14

pink noise A slightly altered pure tone. This is sometimes used by “blue boxers” attempting to gain unauthorized use of phone lines for long-distance calls, to avoid detection up until the connection with the toll network. Once it reaches the network, however, only a pure 2600-Hz tone will be processed by the system. See blue box. PINT Service Protocol PSTN/Internet Interworking Service Protocol. A digital telephony protocol to support the invocation of common telephone services from an Internet Protocol (IP) network. These services range from basic telephone or facsimile communications to content provision. PINT was submitted as a Standards Track RFC by Petrack et al. in June 2000. PINT is an enhancement to services offered through SIP 2.0 and SDP protocols. PINT services can be delivered over Intelligent Networks (INs), private branch exchanges (PBXs), cell phone networks, and ISDN networks. PINT services are negotiated over what is presently two separate networks: the telephone network and the Internet. Calls are initiated on an Internet Protocol (IP) network, with the request passed onto the Global Switched Telephone Network (GSTN) for actual connection. The types of services that can be offered through PINT are defined as Milestone PINT services, and are restricted with an eye to the development and inclusion of further additional services. See RFC 2848. pilot tone In linear modulation transmission schemes, a tone inserted into or above the frequency band to split or otherwise influence the signal with the intention of improving capacity or reducing noise (or both). A transparent pilot tone is one inaudible to human ears. See linear modulation, tone in band. pipelining 1. In data networks, the transmission of multiple frames without checking for acknowledgment of individual frames at the time of receipt (this may be done later by a variety of means). 2. A technique used in certain central processing units to aggregate processor instructions into a set of overlapping processing steps. pits Minute indentations in the plastic medium of an optical recording disc which encode the information, and are read by laser pickup mechanisms. PIU See path information unit. pixel picture element. A unit representing the smallest resolvable area on a monitor or broadcast display. Typically used to describe individual picture elements in raster displays such as computer monitors. The pixel is a useful unit in terms of storing raster images, creating image processing programs (e.g., computer “paint” programs), and describing the resolution of raster-based devices and image sizes (e.g., 1024 x768 pixel display). See addressable graphics, pixmap, raster display. pixel clock In video technology, this is a timing signal used to convert an incoming video signal into pixels, that is, into individual dots or display points. Pixel clocks are found in frame grabbers and can be output by some of the newer cameras. A frame grabber is a device that takes an analog video signal

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and converts it into a pixelized digital raster image (e.g., for freeze framing). Reference signals may be used to synchronize various aspects of video, especially when coming from different sources that may be at different points in the frame display cycle, that is, out of phase. The reference signal may be generated by the frame grabber or may be coordinated with an external reference source, such as the camera or a separate clock reference supplied to the frame grabber. pixel jitter A type of undesirable interference that may occur in pixel synchronization systems such as pixel clocks. Jitter is variance in the timing of a clock that is expected to be even and reliable. Pixel jitter can cause a reference or signal being synchronized with a reference to occur slightly too soon or too late, degrading the signal quality. See pixel clock. PKCS See Public-Key Cryptography Standards. PKZIP A widely distributed, very popular, lossless data compression/archiving utility from PKWARE, Inc. that was first introduced in 1989. The program was initially released for DOS/Windows platforms, but was expanded to provide cross-platform support in 1997. PKZIP has been evolving along with computer technologies. Newer versions can accommodate the increased storage capacities of bigger drives and the desire for users to secure their data for transmission over public networks. With version 4.5, the ZIP file’s size is limited more by the capacity of the system than the capacity of the program archive. There is now also support for Public Key Infrastructure (PKI) digital signatures from recognized signature authorities. PKZIP files can be split to span several storage diskettes or cartridges or for reducing file size when sending file attachments through networks with file size limits. See Java Archive, RAR. plan position indicator A common type of radar display that shows target bearing in terms of a rotating intensity trace synchronized with the rotation of the antenna. There will often be reference marks on the display to help the operator interpret the radar pips. See radar. planar antenna array See antenna, planar array.

A French postage stamp commemorating the contributions of Gaston Planté to storage cell technology. The original lead-acid cell was very simple, with only two plates, but later versions used multiple plates and were more effective than the original. [French Postal Service design by Mazelin, 1957.]

Planté, Raymond Gaston (1834-1889) A French physicist who was one of the first inventors of an electrolytic power storage cell (battery), historically called an accumulateur, in 1859. Planté and another scientist, the chemist Faure, gave seminars on accumulateurs in the early 1880s in Paris, inspiring further generations of engineers and theorists, including Henri Tudor, who created practical applications of storage technologies for the emerging automobile industry and mobile military installations, near the end of the 1800s. Planté’s inventions were also important to the development of X-ray technology. Planté battery Developed in 1859 by R. Gaston Planté, the Planté battery used a sheet of lead and a sheet of positively charged lead oxide separated by rubber, rolled into a tight cylinder, with two electrode connections pointing out of one end. The whole thing was then immersed in a dilute solution of sulfuric acid. This invention was the evolutionary forerunner to the lead-acid car batteries of today. A later version of Planté’s device, with more elements, a housing, and terminals connected in parallel, was presented to the Academy of Sciences by César Despretz in 1860. PLAR See Private Line Automatic Ringdown. plasma display panel A type of display technology which consists of outer layers sandwiched around an inner layer of tiny neon bulbs imbedded in glass. The bulbs can be selectively lit by controlling voltages through matrix addressing. Unlike excited phosphors in CRTs, the bulbs remain lit until explicitly turned off, and thus do not need to be refreshed. Plasma panels are sturdy and flat and used in a variety of field applications. See liquid crystal display. Platform for Internet Content Selection PICS. An effort of the World Wide Web Consortium since 1995, PICS seeks to create a means for voluntarily assessing and declaring the content of a Web site. This provides a way to implement filtering and searches. The first officially recommended PICS document was offered in 1996 as PICSRules1.1, and a number of Web browsers can now detect PICS ratings. PICS contains a language for defining Web page profiles and a number of rating systems have been developed, including ARC (Ararat Software), Net Shepherd CRC, SafeSurf Internet Rating System, and Voluntary Content Rating (VCR). Platform for Privacy Preferences P3P. A development project of the World Wide Web Consortium (W3C) to provide a simple, automated way for Web users to better control use of their personal information on Web sites that they may visit and patronize. It is, in a sense, a checklist of questions related to a Web site’s privacy policies that aids the user in assessing them. Thus, if a site is P3P-enabled, this information is available in a standardized, machinereadable format and can be automatically compared to the consumer’s set of privacy preferences and discrepancies reported. A working draft of the first version of P3P was issued by the W3C in September 2001. This type of development project has arisen due to the high volume of information, including personal

demographics, gender, age, credit card numbers, etc. requested by online vendors. The problem is that an order form may require all or most of the fields to be filled out, thus forcing the consumer to volunteer information that makes him or her uncomfortable. The alternative is often a long, drawn-out search for a phone contact number (after the user has spent considerable time going through a shopping cart program and doesn’t want to abandon the purchase). To better negotiate the volunteering of personal information and safeguarding of personal privacy, the P3P system is intended to arbitrate and streamline this process. platform-independent Software or hardware which follows a standard, or is self-contained, so it can run without modification or significant modification, on a variety of computers. With faster processors, it is possible for more programs and languages to be designed as platform-independent, thus increasing the user’s choice of systems. There exist standards designed to promote consistency in the design of software objects so that computer applications can be platform-independent as well. See CORBA, HTML, Java, Open Systems Interconnection, Perl, Unix. PLC Power Line Carrier. PLCP See Physical Layer Convergence Procedure. PLL See phase-locked loop. PL/M Programming Language/Microprocessor. The first programming language for the first commercially distributed microprocessor, the Intel 4004, designed by a consultant to Intel, Gary Kildall, who later founded Inter-Galactic Digital Research and developed CP/M. PL/M was developed to run on an IBM 360 computer to generate the code, which was burned into the ROM of the 4004. It was later modified by Kildall to support the successor to the 4004, the 8008. PLM See Public Land Mobile. Some have used this to refer to Private Land Mobile, as well, but private mobile services are best distinguished by calling them PrivLM. PLMR Public Land Mobile Radio. PLS See physical layer signaling. PLU See Percent Local Usage.

Plug and Play PnP. A format designed by a number of commercial vendors to overcome some of the problems associated with interrupt-driven computers based on IRQ assignment systems. Not all computer architectures use this means of handling interrupts, but many widely purchased Intel-based computers do. In the days when consumers had only one modem and one printer as peripherals, the IRQassignment design of these microcomputers was not seen as a particularly severe limitation. Unfortunately, as users added mice, sound cards, extra printers, scanner cards, network cards, and other device controllers to their systems, it became a significant problem to keep track of and set up IRQ numbers for interrupts so that there were no system conflicts, especially since some devices were designed to be associated with specific interrupts. As a result, some peripherals wouldn’t work together on the same machine, and the user could run out of interrupts. At this point the architectural structure became a significant hindrance, and vendors developed Plug and Play to overcome some of the problems. Plug and Play is a system that provides dynamic arbitration of system interrupts and sometimes also permits hot swapping of peripheral components or cards. To fully take advantage of Plug and Play, the user needs a Plug and Play-compatible operating system, a Plug and Play BIOS, and Plug and Playcompatible peripheral cards that don’t have overlapping IRQ requirements. Plutarch An ancient Greek philosopher who attempted to explain the static phenomena associated with lodestone, a natural magnet, and the attractive properties associated with the rubbing of amber. Although it took centuries for them to be understood, these early speculations led to an understanding of electricity. He also made an important observation about the differences between lodestone and amber, in that lodestone appeared to attract only certain substances, primarily iron, whereas amber attracted a multitude of objects, as long as they were very small and light. PM performance monitoring. PMA physical medium attachment. A device which connects physically with a network.

Point-to-Point Protocol Framing +-----------------+-----------------+-----------------------+| Protocol | Information | Padding up to MRU | | 8 or 16 bits | 0 or more | ... | +-----------------+-----------------+-----------------------+A basic, unembellished frame as described in RFC 1171 looks like this: +----------+----------+----------+----------+----------+----------+----------+ | Flag | Address | Control | Protocol | Informa- | FCS | Flag | | 01111110 | 11111111 | 00000011 | 16 bits | tion | 16 bits | 01111110 | +----------+----------+----------+----------+----------+----------+----------+

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PMARS Police Mutual Aid Radio System. PMDF A store-and-forward system from Innosoft International, Inc. for distributing electronic mail. PMDF is a mail transport agent (MTA) which directs messages to the appropriate network transport and ensures reliable delivery over that transport. PMDF is implemented for DEC Unix and VMS systems, and Sun Solaris and SunOS systems. PMR 1. See poor man’s routing. 2. private mobile radio. PMS 1. See Pantone Matching System. 2. See Picturephone Meeting Service. PMT 1. Photo Multiplier Tube. Light control technology commonly used in higher end drum scanners. See charged coupled device. 2. Photo Mechanical Transfer. A camera-ready layout tool used in the printing industry. pn junction, p-n junction Within some types of semiconductors, a region of transition between p materials (positive holes) and n materials (negative electrons). See n region, p region. PNG See Portable Network Graphics. PNG Development Group A group initiated in January 1995 by the release of the first draft of the Portable Bitmap Format (PBF), which evolved into Portable Network Graphics (PNG). Thomas Boutell, Scott Elliott, Tom Lane, and many other early contributors developed an open source, freely distributable graphics compression format successor to Compuserve’s proprietary Graphics Interchange Format (GIF). In an unprecedented development effort, the format went from first draft to final draft in only 2 months, a remarkable example to the standards-development community. See Portable Network Graphics. PNM public network management. PnP See Plug and Play. PNP See Permanent Number Portability. Pockels effect A very small linear electro-optical effect, similar to the Kerr electro-optical effect, except that the change in the index is proportional to the applied electric field. Pockels-based cells require lower voltages than similar Kerr cells. Optical shutters can be designed to exploit the Pockels and Kerr effects. See Kerr electro-optical effect. PODP Public Office Dialing Plan. point of interconnection POI. The physical point of interconnection between various telecommunications networks. This may also represent a demarcation point for service and responsibility for connections. Point of Presence POP. In data networks, a node consisting of a server, network connection, router, and one or more hosts, but not including a network operations center or network information center. A POP is sometimes serviced remotely from a Network Operations Center (NOC). point of presence, telephony POP. In telephone networks, the central location of an Inter Exchange Carrier (IXC), the point at which the IXCs long-distance lines connect with the various local phone companies’ lines. The point of connection for long-distance calls or for cellular calls.

point size A typographic unit of measure equal to ~.0139 in., approx. 1/72 in. (72.27). Point size is sometimes used to describe the sizes of graphic elements, and almost universally used to describe the height of a typestyle and distances between lines of type. It may include a small amount of space above and below the ascenders and descenders as it was originally based upon the physical size of a wooden or metal block on which the typeface was mounted, but does not include extra space added between the lines with leading. Type sizes from 10 to 12 points are common for business or personal correspondence. Headlines in newspapers are frequently as large as 72 points. Point sizes below 9 are difficult for many people to read and do not render well on printers with resolutions of 200 dpi or lower. It is never correct to refer to the size of a font on a computer monitor in terms of point size if you are talking about pixel resolution or size relative to the settings of the monitor. A 10-point font can vary from 8 scanlines to 20 scanlines (or more), depending upon the monitor settings and the degree of zoom. A 20scanline font is not the same as a 20-point font. It is best to use point size to describe fixed media, such as the size of the font on a piece of paper once it has been printed. See ascender, descender, leading, pica, typeface. point-to-multipoint A system in which a transmission originates from a single source and is transmitted to multiple destinations. Most broadcast media are point-to-multipoint. point-to-point A system in which a transmission originates at a single source and is transmitted to a single destination. Many personal and business transactions, such as email addressed to a single recipient, are point to point communications. See Pointto-Point Protocol. Point-to-Point Protocol PPP. A standard method for transporting multiprotocol datagrams over point-topoint links. PPP is intended for facilitating connections through a wide variety of hosts, bridges, and routers. PPP provides a method for encapsulating datagrams; a Link Control Protocol (LCP) for establishing, configuring, and testing the data-link connections; and a family of Network Control Protocols (NCPs) for establishing and configuring different network-layer protocols. PPP is intended for simple, bidirectional, full duplex links transporting packets between peers. With PPP, different network-layer protocols can be simultaneously multiplexed over the same link. PPP encapsulation requires framing to indicate the beginning and ending of the encapsulation. PPP consists of a 1- or 2-octet protocol field, followed by an information field of zero or more octets, followed by an arbitrary number of octets to pad up to the Maximum Receive Unit (MRU), which includes the Information field and Padding, as shown in the PPP Framing chart. In order to establish communications, each end of the link must first send LCP packets to configure and test the data link. Once the link is established, peer authentication may be optionally carried out. PPP must

then send NCP packets to select and configure one or more network-layer protocols. Once this has been done, datagrams may be transmitted. The link remains open until the LCP or NCP packets close it, or until some external event terminates the link. See Link Control Protocol, RFC 1171, RFC 1220 (Extensions for Bridging), RFC 1661. Point-to-Point Tunneling Protocol PPTP. A networking protocol proposed as a draft in July 1997 by a group of commercial networking vendors including Ascend Communications, U.S. Robotics & 3Com, Copper Mountain Networks, Microsoft Corporation, and ECI Telematics. PPTP allows Point-toPoint Protocol (PPP) to be tunneled through an Internet Protocol (IP) network; that is, it provides a means of carrying PPP traffic so users can benefit from secure remote access over virtual private networks (VPNs). PPTP seeks to increase the flexibility of IP management. Dial-in users of a common PNS can retain a single IP address. Users of other protocols such as AppleTalk could be tunneled through an IP-only system. In ISDN systems, where multilink PPP is typically used to aggregate B channels, a single PPTP Network Server (PNS) can handle the bundle, instead of grouping it at a single Network Access Server (NAS), thus making it possible to spread the bundle across multiple PPTP access concentrators (PACs). PPTP specifies a client/server call-control and management protocol, allowing the server to control access for dial-in circuit-switched calls originated from a public switched telephone network (PSTN) or ISDN. It can also initiate outbound, circuit-switched connections. Flow- and congestion-controlled encapsulated datagram packet services are provided by an enhanced Generic Routing Encapsulation (GRE). PPTP provides for the decoupling of a number of Network Access Server functions in order to gain flexibility. See Point-to-Point Protocol. pointcasting The broadcasting of specialized information or custom-selected information to a particular subscriber. Pointcasting is occurring over the Net, where it is possible to sign up for subscriptions for individualized information and have them electronically forwarded, somewhat like a traditional clipping service. See broadcasting, narrowcasting. poke See peek/poke. polar keying A transmission technique, commonly used in telegraphy, which employs two current states (as opposed to just turning the current on and off), i.e., current flowing in opposite directions, positive or negative voltages, to indicate mark and space signals. See telegraph, needle. The idea of using polarities led to later duplex and multiplex systems, and alternate polarities are now incorporated into digital transmissions systems. polar mount A common type of antenna mount for parabolic antennas that is installed with the elevation mount pointed at the North Star (hence the name). Once installed, the hour axis, on which the dish swivels, is adjusted to correspond to the arc of the satellite orbit, and can be interfaced with a

computer control device to simplify positioning. This type of mount is used with antennas that require orientation toward highly directional beams. See azimuth-elevation mount, parabolic antenna, microwave antenna. polar relay A type of relay used in older communications switching systems such as telegraph systems, which uses a permanent magnet to center the armature, and a split magnetic circuit so the relay can be polarized to operate in one direction or the other. A vibrating circuit is sometimes added to a polar relay to increase its sensitivity and reduce its response time. horizontal filtering

vertical filtering

An incoming wave can be separated into its horizontal or vertical polarized components by filtering. This has two advantages: it permits selection of incoming information and the transmission of more information in the same bandwidth.

polarization n. 1. A movement or division in opposite directions or into opposite parts. 2. When radiation, especially light, vibrates perpendicular (normal) to the main electromagnetic beam (which may be straight or elliptical). In photography and sunglasses, polarization is selectively controlled to influence the light reflections that pass through the lens. 3. In an atom, the slight displacement of the positive charge of a dielectric, when influenced by an electric field. 4. The orientation of molecules in a magnetic material, when aligned in the direction of magnetic lines of force. 5. In antenna transceivers, a way to process a transmission wave’s characteristics and direction. Horizontal and vertical polarization provide ways to reduce certain types of interference and facilitate the directing of a beam. Vertical and horizontal polarization can be combined to create circular polarization. This creates a helical wave that can be received by either vertically or horizontally polarized antennas. Polaroid connector A 9-pin connector that is used as a terminal connection on a Polaroid 6500 sonar ranging module (for sensing distances). Police Radio Service PRS. A mobile communications service for handling police communications such as dispatching, information requests, tactical instructions, and various administrative communications. policy-based management In networking, an administrative adaptation to the management of

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A Morse code-based rapid telegraphy system, theoretically capable of transmitting 88,000 words an hour, was developed in the late 1800s by Hungarian inventors, Pollak and Viràg.

networks that are too large to evaluate and maintain on a device-by-device basis. Policy-based management typically entails the development of a set of rules and guidelines for implementing network-wide decisions in areas such as security, quality of service (QoS), reliability, etc. poll-safe See Logical Storage Unit. Pollak and Viràg telegraph A rapid telegraphy system developed in the late 1800s by two Hungarian inventors: Pollak, a telegraph agent, and Viràg, a patent examiner. The system employed Morse code transferred to a perforated tape which passed around an electrically connected wheel. The perforations were organized in two lines, the top for dashes. Metal brushes connected to a galvanic battery registered the pulses as the brushes passed across the holes and briefly closed the electrical circuit. The negative and positive pulses caused a mirror to swing right or left, reflecting incandescent light onto light-sensitive paper. Subsequent development of the paper message took about 5 minutes, imaging the Morse code. In 1900, the inventors communicated a message of 220 words in 9 seconds (a rate of 88,000 words per hour) between Berlin and OfenPest. polyvinyl chloride PVC. A weather-resistant polymerized vinyl compound, plastic or resin, widely used in piping and as insulation in low-voltage electrical installations. PVC is not suitable in high temperature environments, as the material will give out dangerous gases or will burn when subjected to heat. Pony Express A colorful contributor to American history, the Pony Express service was organized by William Hepburn Russell to provide postal and parcel delivery among growing urban centers and farflung pioneer towns and villages. It was an ambitious undertaking in a large, undeveloped country

with only about 15 million residents spread across a vast distance of 3000 miles east to west. In good conditions, a rider could cover two-thirds of that distance, with a relay of horses, in less than 10 days. The service was organized in shifts, with stations dotting the landscape at about 10- to 15-mile intervals, where riders would change their horses, and the riders themselves would switch off after about five to seven changes of horses. The Pony Express began in April 1860 and would have only run until July 1861 when news spread of the creation of the Western Union transcontinental telegraph line. The Express was induced to continue for the 4 extra months it took to complete the line, and ceased operating in October 1861. It achieved such legendary status in books and movies that many people are unaware of the briefness of its history. poor man’s routing A means of routing packets according to a route defined at the source, without using network layer routing algorithms. It can be a simple, appropriate means of accomplishing the transmission on a small network with known characteristics, or on a larger network which is known to be stable and through which an efficient route has been precharted and considered to have a high likelihood of being available. POP 1. See point of presence. 2. See Post Office Protocol. 3. Abbreviation for population. One population unit, in other words, one person. In wireless services, carriers are rated partly according to POPs. Popow, Aleksandr Stepanowitsch (1859-1906) A Russian physicist and educator, who improved on the discoveries of Oliver Lodge and created a receiver with an antenna wire for better reception in 1895 or 1896. Around the same time, he sent a wireless message from an ocean vessel to his laboratory in

St. Petersburg. See telegraph history. populated In electronics, a printed circuit board (PC board) that has had components added to the traces, as opposed to a bare board. popup As one word, it is a noun; as two words, it is a verb, as in “I saw it pop up a moment ago.” A memory-resident program that remains out of sight until needed and then pops up in front of the current application (and then disappears again when not needed). Making the program memory-resident is a convenient way to have it load and display very quickly, hence the name. See popup menu, TSR. popup menu A type of computer menu frequently used in graphical user interfaces in situations where the user has a number of possible selections, but those selections should be displayed only on an as-needed basis, so as not to obscure the rest of the screen. A popup menu or dialog box is usually selected through a keyboard or pointing device. On dedicated computer devices, popups sometimes are activated by pressing a specific button or hot key sequence. port 1. Point of ingress or egress, or both. Data input/output point. 2. Entrance or exit to a network, firewall, or gateway; a transmissions interface. 3. Data input or output path to peripheral devices such as modems and printers. port, access Access point to a virtual port, such as a chat room or a physical port, as a connecting point, switch, or card interface. Port management, security, protocol conversion, and traffic management are essential aspects of networks, especially mixed networks and those with shared resources. See port adapter. port adapter In a Fiber Distributed Data Interface (FDDI) token-passing network there are two physical ports, designated PHY A and PHY B. Each of these ports is connected to the primary and secondary ring, to act as a receiver for one and a transmitter for the other. The port adapters are typically configured as peripheral cards that fit into slots in an interface processor. In many systems, several slots are available, and it may be necessary to insert a blank card in open slots for ventilation, and to conform to emissions requirements for computer-related devices. Port adapters may be equipped with optical bypass switches to avoid segmentation which might occur if there is a failure in the system and a station is temporarily eliminated. FDDI ports can be directly connected to either single mode or multimode fiber optic media, providing half duplex transmissions. LEDs are commonly used on port adapters as status indicators. Optical bypass switches may in turn be attached to the port adapters. See Fiber Distributed Data Interface, optical bypass. port adapter module PAM. A Cisco Systems ATM module with ports that can be configured as redundant links for use by ATM routing protocols. Port status is indicated by LEDs, and each port can be configured to a variety of clocking options. Aggregate output traffic rates can be controlled to accommodate slow receivers of public network connections with peak rate tariffs.

port sharing A networked system in which two or more devices or two or more virtual connections (VCs) share a single port. Common ports are printer and modem ports, and it is not uncommon for many computers to share a limited number of printers and modems. Port sharing is usually accomplished through a combination of software and hardware. In manual systems, the port may be shared by using an A/B switch device. For example, two computers may be sharing one modem and, since most modems cannot handle two ongoing transmissions, the switcher is set to one computer or the other. Multiple printers on medium or large systems may need more sophisticated management to handle the traffic, in which case an automatic switcher may handle the queues and access to the various printers or other ports. Not all ports connect to physical devices in the sense of a modem or printer. Some ports are virtual communications ports for chat lines, or other networked services, in which the handling of the port access is generally handled through software. port-sharing device A device which selectively limits or administers shared access to a virtual or physical port. A switcher, from simple A/B switch to an intelligent logical switching device, is a common means with which to share resources on a networked systems. See port sharing. portability 1. An attribute of a hardware device that makes it easy to carry around. Pen computers, palmtops, and laptops are light and battery-powered to maximize their portability. 2. An attribute of software that makes it easy to move from one platform to another. Hardware-independence. Languages like HTML, Sun’s Java, and Perl were designed to be portable. Unix software is portable to a wide variety of systems. 3. An attribute of a virtual address that allows the user to access a phone or computer network from a variety of locations. See mobile computing, cellular. portable Easy to carry around, particularly devices which have desktop analogs as a desktop computer and a smaller portable computer, a desktop or wall phone, and a battery-powered, small portable phone. Portable is considered the category of devices that are easiest to use while mobile. Luggables and transportables are the next level up, as they are a little heavier and usually require more power consumption. Portable Computer and Communications Association PCCA. A nonprofit organization established to provide a forum for the various industries to cooperate in the evolution of interoperable mobile computing and communications standards and implementations. http://www.outlook.com/pcca Portable Document Format PDF. An Adobe Systems Inc. proprietary document encoding and display format used on many Web sites to distribute readmostly document files. PDF files can be created and exported from many desktop publishing and layout programs, or with Adobe Systems Acrobat, which is designed for this purpose. Freely distributable PDF readers are widely available for download on the Internet. PDF files typically carry a .pdf file extension.

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Portable Earth Terminal PET. A ground-based communications satellite terminal. The phrase is used generically and also refers to NASA units developed in the late 1970s.

A portable Earth terminal for satellite communications. [NASA/GRC image by Brown.]

Portable Network Frame PNF. A format for using multiple subimages in a single frame; a multimedia graphics format intended as the foundation for the Multiple-image Network Graphics format (MNG) which is essentially Portable Network Graphics (PNG) for animations. PNF was submitted as Draft 1 by Glenn Randers-Pehrson in June 1996. With Draft 12, in August 1996, PNF came to be known as MNG. See Multiple-image Network Graphics, Portable Network Graphics. Portable Network Graphics PNG. (pron. ping) A graphics standard developed during the first two months of 1995, with the Web in mind, which is recommended by the World Wide Web Consortium (W3C, WWWC). It received official “done” status in May, 1996. A standard for lossless, variable-transparency, cross-platform, “truecolor” graphics which includes, in the file, information about the authoring platform so the viewer can adjust the image accordingly. PNG was developed as a result of an unexpected patent announcement by Unisys Corporation in the mid-1990s. Unisys claimed intellectual property ownership over the Lempel-Ziv-Welch compression algorithm, which was integral to many graphics compression schemes, the most visible of which was CompuServe, Inc.’s GIF format. GIF was well supported and widely used on the Web. Programmers were taken aback and reacted with concern, and soon there was a move to create an alternate format – not just a simple alternate, in fact, but a better format, which would provide an evolutionary improvement over GIF. At about the same time, CompuServe announced that they would begin development of a GIF successor, GIF24, followed by an official announcement a month later that PNG would be used as the basis for GIF24. The Internet community of programmers, some of

whose contributors included members of The World Wide Web Consortium (W3C) and Compuserve, began work on the development of PNG. The current consensus is that PNG is a good format and it is quickly being adopted by the Web community. The PNG specification was transcribed by Thomas Boutell and Tom Lane and released as RFC 2083 in 1997. The features of PNG include an open software standard, good lossless compression ratios, 8-bit color palette support, 16-bit grayscale support, 24- and 48bit truecolor support, alpha blending transparency for supporting different degrees of transparency, gamma correction, two-dimensional interlacing, text chunk support, multiple CRCs for error checking without viewing, security signature, full online references, and source code availability. PNG was not designed for animation support; it was intended for single images. MNG was subsequently developed to support animation. See Graphics Interchange Format, Lempel-Ziv-Welch, magic signature, PNG Development Group, Portable Network Frame, Virtual Reality Modeling Language, See RFC 2083. http://www.cdrom.com/pub/png/png.html Porthcurno The U.K. port location of historic submarine telegraph cables, established primarily by John Pender in the 1870s, Porthcurno (historically Porthcurnow, in southwest England) is now the port link for a new fiber optics cable, installed in 1997. It is also the home of the Centre for the History of International Telegraph Communications, including the Museum of Submarine Telegraphy images and artifacts documenting the region and telegraphic communications. The collection includes telegraph keys, sounders, relays, synchronizers, and more, some of which may be viewed online. The surrounding landscape includes historic cables under the sand and underground tunnels. http://www.porthcurno.org.uk/ portrait A descriptive word that refers to the direction of roughly rectangular objects, usually printouts, photographs, or monitors, which are oriented so the long side is vertical and the short side is horizontal. The term is widely used in the photography and printing industries to describe the orientation of text or images on a page. Some monitors have been designed to pivot 180° so they can be used in both portrait and landscape modes. Most monitors are designed to be used in landscape mode, but portrait mode monitors are handy for WYSIWYG desktop publishing of printed page-oriented layouts. Contrast with landscape. portrule A historic telegraphic device with a metal, toothed bar acting as symbolic contact points to define digits or code symbols. This device was later superseded by the simpler telegraph key. POSIX 1003.0 Portable Operating System Interface UNIX. An open systems standards architectural framework, also known as IEEE 10030.0 POST See power on self test. Post Roads Act A regulation of the telecommunications industry in the United States begun in 1866 with the Post Roads Act in which authority was granted to the Postmaster General to oversee rates for

government telegrams and to assign rights of way through public lands. By 1934, after passing through some intermediate bodies, including the U.S. Department of Commerce, telecommunications became the primary responsibility of the Federal Communications Commission (FCC). Post Telephone & Telegraph administration. Telecommunications operating bodies around the world that are individually controlled by their regional governments. Postal Telegraph Company A historic communications provider, founded in 1881. Postal was formed to market some of the new telegraph technologies, particularly those of Elisha Gray. Postal pioneered the use of a new type of copper wire with a steel core, known later as Copperweld. In 1883, controlling interest in Postal was acquired by John W. Mackay, cofounder of Commercial Cable Company. It reorganized after filing for bankruptcy in 1884. Control of the company then passed through the hands of Albert B. Chandler to Mackay’s son, Clarence H. Mackay. It merged with IT&T in 1928, reorganized in 1939, and finally was merged into Western Union in 1943. Postel, Jonathan B. (1943-1998) No dictionary about the Internet would be complete without expressing appreciation to Jonathan Postel. From the early ARPANET to the current Internet, he contributed three decades of low-key, passionate, dedicated service and volumes of fundamental information as a developer, advisor, protocol prototype implementor, and offical RFC documents editor. Like the underlying thread that runs through a tapestry, Postel held quietly to a vision, avoiding the fanfare and business opportunities that constantly presented themselves to pioneers of the computing industry. He chose instead to concentrate on the structure and orderly evolution of this most important communications medium, for the benefit of all. Over the years, Postel worked for a number of educational institutions and high technology companies including the Network Measurement Center at UCLA (ARPANET) and SRI International with Doug Engelbart. See IANA, Request for Comments. postmaster The person responsible for configuring and maintaining a network mail server, often including administering users, setting up mailboxes, distribution lists, aliases, filters, etc. Many of the postmaster functions are actually handled by computer software such as dragons and mailer daemons. PostScript, Adobe PostScript A powerful, highlevel, device-independent page description language and document format widely used in desktop publishing and electronic document design. PostScript, from Adobe Systems, Inc., is used for bitmap and scalable images, scalable fonts, computer monitor display systems, and much more. PostScript originated as the Design System language in 1976 at Evans & Sutherland Computer Corporation, a company renowned for its pioneering flight simulator programs. John Gaffney is credited by John Warnock as the inspiration behind many of PostScript’s major design components. In 1978,

when John Warnock joined Martin Newell at Xerox PARC, they reimplemented Design System as JaM (after their first names, John and Mark). At this time, the language was used for experimental applications in VLSI design, printing, and graphic arts, resulting in Xerox’s printing protocol called Interpress. Warnock joined forces with Charles (Chuck) Geschke in 1982 to form Adobe Systems Incorporated. He and Geschke further developed JaM in collaboration with Doug Brotz, Bill Paxton, and Ed Taft; PostScript was born of the effort. One of the important developments that helped introduce the PostScript language and make consumers aware of its capabilities was the release of the Apple LaserWriter PostScript-capable printer in 1984. Although PostScript doesn’t seem as remarkable now, in 1984 most people had 9-pin dot matrix printers and bitmap fonts that provided output that even the most undiscriminating viewer would admit was crude at best. Suddenly, with PostScript, a prosumer-priced laser printer could print legible, beautiful text down to 4 points in size in some of the finest fonts in the world. This launched the desktop publishing revolution, one which is still having a farreaching impact on the publishing market, especially among small presses, self-publishing individuals, and genealogists. PostScript fonts are some of the best computer fonts in the world. Adobe Systems maintains a large library for sale to consumers and service bureaus. PostScript fonts are scalable, in order to print out at the best resolution of the output device. Many people think that PostScript fonts and other scalable fonts are essentially the same, but most other scalable fonts are not integrated into a page description language, and so are not as flexible and powerful as PostScript fonts. Since PostScript is a programming language, fonts can be swirled, stretched, and individually rendered so that each letter differs from the previous in some essential way. The possibilities have even now not been fully exploited. PostScript is commonly used to distribute documents on the Web, as is Adobe Acrobat format, a secondcousin to PostScript for displaying text and graphics. It is also possible to send high-quality PostScript documents through email, by sending the file as an email file attachment. This is a means by which people can send professional-looking text and graphics résumés, business documents, manuals, and much more over the Internet or be linked to a Web page for instant download. See vector fonts. potentiometer 1. An instrument for measuring electromotive forces. 2. A device used to regulate a current by varying the resistances at either end. It can also perform the functions of a rheostat, which is more limited. Potentiometers are commonly incorporated into dials and computer input devices like joysticks. See rheostat. POTS Plain Old Telephone Service. The basic analog phone service, which has been available from local phone companies and used in homes for years and years. No ISDN, no surcharge services such as Caller ID, Call Waiting, etc. See loop start.

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potting To embed within an insulating or protective material or layer, usually for the purpose of reducing electrical interference or fire hazards. Potting is sometimes required in cases where higher voltage computer components may be interfaced with lower voltage phone lines. Poulsen arc A device enclosed in a gas atmosphere with a strong magnetic field, which created an electric arc that could generate high frequency radio waves. It was found that larger versions of the Poulsen arc could generate even greater arcs. The rights to market this technology were purchased in 1909 by C. Elwell, who formed the Federal Telegraph Company to design and build industrial arc transmitters used in the newly developing broadcast industry. Eventually the technology was superseded by vacuum tube transmitters. See arc converter; Duddell, William; Poulsen, Valdemar. Poulsen, Valdemar (1867-1942) A Danish scientist and inventor who built upon the work of William du Bois Duddell and devised a way to use an electric arc to generate continuous waves at high frequencies by placing the arc in a controlled atmosphere within a strong magnetic field. He collaborated with P.O. Pedersen in inventing a form of wireless telegraphy technology. In 1898, Poulsen recorded electronic waves on a thin conducting wire, a pioneer electromagnetic tape recorder that was called the telegrafon or telegraphone. He was awarded a patent for his magnetic recording device in November 1900 (U.S. #661,619). pound 1. An alternate term for the number or crosshatch sign (#), sometimes called an octothorpe. Programmers often refer to it as a hash sign. On pushbutton phones using automated menu systems, the instructions will sometimes tell the user to input a number followed by the pound key. The pound key signals the system that you have finished typing in the number. 2. In music notation, the symbol for a sharp, a note raised a half tone. power, electrical Expressed in watts, the product of the electromotive force (in volts) and the current (in amperes). Thus, P = E I. In terms of resistance, according to Ohm’s law, this can be expressed as P = I2 R. See ampere, Ohm’s law, ohm, resistance, volt, watt. power down To initiate or perform a sequence of operations in order to shut down a system. For example, a power down on a computer may involve closing files, asking the user to save data, logging out the user, etc. before actually terminating the power to the system. Power down sequences are designed to clean up systems, remove unwanted files, and prevent the accidental loss of data. power hole digger A machine for digging deep narrow holes for utility poles, starting with the early telegraph lines. It was introduced in North America around 1915, although line workers using long spades still dug the holes in undeveloped regions for several decades after the introduction of the power hole digger. See pike pole. Power Macintosh computer, PowerMac The successor to the original Macintosh line, the PowerMac

is based upon IBM POWER RISC chip architecture. This popular line is gradually being succeeded by even faster Macintoshes built with G3 and G4 chips.The PowerMac series is not obsolete, however; a number of third-part developers such as XLR8 and Sonnet have developed reasonably priced PCI-format G3 and G4 accelerator cards that are compatible with most of the PowerMac machines, providing speeds ranging from 300- to 600- MHz and higher. See G3, Macintosh computer, POWER. POWER, Power PC Performance Optimization With Enhanced RISC. A complex processor, one of the first superscalar processors, initially implemented by IBM with three integrated circuits (branch, integer, floating point). This technology was further developed as a microprocessor by IBM, Motorola, and Apple Computing in the early 1990s. The idea was to create a successor to the Motorola 68000 line and the Intel 80x86 line; the PowerPC was the result of this collaboration. The first version was the PowerPC 601, released in 1993, derived strongly from the IBM POWER specification. Since then, a series has been released, including the 603, 604, and G3, and the chips are incorporated most familiarly into the PowerMacs and Macintosh G3s. power connector See p connector. power hole digger A machine for digging deep narrow holes for utility poles, starting with the early telegraph lines. It was introduced in North America around 1915, although line workers using long spades still dug the holes in undeveloped regions for several decades after the introduction of the power hole digger. See pike pole. power on self test POST. The process of checking internal systems prior to becoming fully operational that occurs in many electronic devices immediately after the system is powered on. For example, in computers, the system may check memory subsystems, configuration parameters, electrical voltages, the presence or absence of certain peripherals (e.g., monitors) before coming online in terms of initiating external data or operating systems that may be contained on a CD-ROM or hard drive. Many laser printers have self tests and may optionally display the results of the test and basic configuration parameters on a printed page. If the self tests fail, the system may power down, flash warning lights, or display a message on an LCD screen, depending upon how it is programmed to respond to problems and how early in the test sequence the problem occurs. See power up sequence. power save mode See sleep mode. power up sequence The operational bootstrap and test sequence that a computer goes through when first powered on. This usually includes loading very low level routines, often from read-only memory (ROM), which then make it possible to load other routines and operating system capabilities from a hard disk, floppy, cartridge, or CD-ROM drive. It is very common for a computer to run through a hardware systems check in the power up sequence to test memory, sound, graphics, and other basic input/output devices. Device drivers and external device checks may also

be performed, in addition to locating and interfacing with a network, if applicable. If many devices are attached to a computer, it may be important to power them up in the right order. If you turn on the computer before turning on external hard drives, CD-ROM drives, or video signal sources, the computer may not recognize the device or synchronize correctly with the signal. As a general rule, turn on peripherals before turning on the computer. Give a hard drive a moment to “spin up,” that is, get the drive revolutions up to speed, before turning on the computer. Similarly, with a device such as a scanner or printer, which may also have test sequences, count to five before you turn on the computer. If a system is being powered up right after being shut down, it is important to wait 30 seconds or so before turning it back on. Some of the electronic components in a computer will retain current after the system is shut down, and a sudden surge of additional current may stress the circuitry. Give the current a few moments to drain off, then turn the system back on. Newer peripheral bus technologies such as Apple FireWire are more flexible in terms of monitoring a live electrical connection or data stream. They may be hot swappable and configurable on-the-fly, thus freeing the user from worrying about startup and selftest sequences. PPDN Public Packet Data Network. PPI 1. pixels per inch. See resolution. 2. See plan position indicator. PPP See Point-to-Point Protocol. PPS 1. packets per second. A means of quantifying network traffic by tallying the number of packets transmitted through a given point in a given amount of time. 2. Path Protection Switched. See SONET. 3. See Precise Positioning Service. 4. pulses per second. PPSN Public Packet Switched Network. PPTP See Point-to-Point Tunneling Protocol. PRAM programmable random access memory. A chip that is sometimes used on computers to save semipermanent configuration settings such as monitor settings. The chip retains its information by being refreshed with power from a battery, usually a small lithium cell. This battery may have to be replaced every 6 years or so. PRB Private Radio Bureau. Precise Positioning Service PPS. One of the precise location data signals transmitted from Global Positioning System (GPS) satellites. This signal is for military and general government use, requires a specially equipped receiver, and is encrypted. Horizontal and vertical accuracy are about 22 to 28 m, respectively, and time accuracy is 100 nsec. See Global Positioning System, Standard Positioning Service (SPS). Preece, William A British researcher who experimented in the late 1800s with conductivity methods for sending wireless communications. He was able to send a message a distance of 5 miles. See conductivity method.

Predictor Compression Protocol PCP. A method for transporting multiprotocol datagrams over PPP encapsulated links proposed in the mid-1990s. PCP is based on Predictor, a freely available high-speed compression algorithm implemented by Timo Raita in the mid-1980s. While not considered the fastest compression algorithm, it had the advantage of availability. See Point-to-Point Protocol, RFC 1978. prepaid phone card A credit card-like monetary storage medium which is charged or credited with a certain amount of prepaid phone access. This phone card can then be inserted in a card-compatible phone and will automatically allow access to calls up to the amount charged on the card. Copying machine cards are somewhat similar. Unfortunately, many phone cards are not rechargeable, which is an unfortunate waste of resources since a phone card can last many years, as do copy cards. This is mainly due to the way the accounting is done. The value of the card is not simply embedded in the card as it is on a copy card, rather it is handled through accounting software at the switching center. The best reason to get a phone card is to avoid inserting coins into a telephone, especially for a long-distance call during which you might be interrupted by an operator to add more change (which might not be handy). The denominations on a phone card vary from region to region, but amounts such as $4.95, $9.95, and $19.95 are common. A variety of vendors offer phone cards; the service is not necessarily directly provided by the local phone company. This accounts for the different designs on the cards, the different ways in which they are promoted, and the different denominations that are available. Presentation Manager PM. IBM’s standard toolkit and graphical user interface for OS/2, a multitasking operating system for desktop Intel-based computers. PM provides a means to develop applications that conform to the windows-based interface characteristics of OS/2. Presentation Time Stamp PTS. In MPEG-2 encoding, a timestamp that is encoded into the elementary packet stream. This is used for synchronization of different streams by comparing it against the System Time Clock (STC). A video decoder synchronizes the MPEG video data with the STC, with the assumption that the audio decoder follows suit. If the synchronization is within acceptable parameters, the decoded picture is displayed; otherwise, it is repeated, the STC is readjusted, or the next B or P frame is skipped over to maintain synchronization. preset A setting configured in advance so it can quickly be accessed later. Thus, in video and audio editing, cuts and dubs are sometimes preset; in computer programs, times or online activities may be preset. Pushbutton radios can be preset to instantly tune to a desired frequency. President’s Task Force on Telecommunications Policy See Telecommunications Policy, President’s Task Force on. PREST Centre for Policy Research in Engineering, Science and Technology. U.K. group.

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Pretty Good Privacy PGP. A powerful high-security encryption scheme developed in the early 1990s by Philip Zimmermann, based on the Blowfish encryption technology. PGP provides privacy and authentication of transmitted messages. Only the person intended to see the message can read it. An intercepted message cannot be deciphered. Authentication provides assurance of the authenticity of the sender and that the message has not been changed. PGP is freely distributed to U.S. and Canadian citizens for noncommercial use by the Massachusetts Institute of Technology (MIT) in cooperation with Zimmermann and with RSA Data Security, Inc., which licenses patents to the publickey encryption technology incorporated into PGP. PGPfone has now been developed to provide for secure online digital phone conversations. In 1998, Network Associates acquired PGP technology. See Blowfish; International Data Encryption Algorithm; PGP Inc.; Zimmermann, Philip. There is a useful PGP-related informational FAQ on the Web. http://cryptography.org/getpgp.htm preventive maintenance Regular inspection, testing, adjusting, and maintenance of equipment in order to prevent problems before they cause damage or affect service. Computers (especially floppy disk drives and the area around the fan) tend to accumulate dust every couple of years; the fuzz should be gently brushed out or vacuumed with a low-power, finenozzled vacuum, making sure the computer equipment is turned off and probably even unplugged. Don’t use a metal nozzle for vacuuming and ground yourself first by touching the power supply casing to drain off accumulated static electricity. A good time to clean is when swapping or installing memory. Also gently check the various chips on the motherboard to ensure that they are firmly seated. Chips occasionally work their way up out of their seating or may loosen when a system is transported. Monitors should be turned off when not in use, and should have a screen saver active when in use. Batteries in phones that have extra features (like LCD readouts) should be replaced regularly, before you lose all the phone numbers programmed into the system. See screen saver. Price Cap Regulation A means by which local monopolistic phone companies are regulated so that rates remain the same for a specified period. Unlike Profit Cap Regulation, which did not carry large incentives to pare back staff or adopt more cost-effective, newer technologies, it was intended that Price Cap Regulation would provide incentives for innovation. Many companies changed from Profit Cap Regulation to Price Cap Regulation in the mid-1990s. Primary Rate Interface PRI. One of two major categories of ISDN services, PRI caters to higher-end customers and businesses. See Basic Rate Interface, ISDN. primitive A representation of a basic unit in computing. As examples, a graphics primitive may be a circle, line, or square; an audio primitive may be a phoneme or sound; a programming primitive may be a routine, procedure, or object. A primitive is some

type of basic building block, usually one frequently used or reused. In networking, a primitive is an abstract representation across a layer service access point, where information is exchanged between a user and provider. principal Main, central, overriding; the highest authority or administrator. principle A general, or fundamental concept, statement, or truth. A basis for decision-making, actions, or operations. print server, printer server A system that handles the logistics of requests to one or more printers on a network. Frequently there will be a variety of types of printers shared among users. These might include plotters, laser printers, dot matrix printers, high-speed page printers, and specialized color dye sublimation or thermal wax printers. The print server handles queuing; messages to users if a printer is not in service; alternate routing if the printers have been reorganized; scheduling, if some types of jobs (e.g., big ones) are to be run at night or after hours; and prioritizing, if some users have higher precedence. The print server can also be used to send messages to maintenance personnel if there is trouble with paper jams, empty trays, etc. Some printers have sufficient processing power to send status and error messages to the server, which in turn may be relayed to the user or the appropriate service center. print spooler An application which manages and schedules a printing job to a printing device in such a way that the computer is not tied up, waiting for the print job to finish. For example, imagine sending a large plotting job to a plotter from a CAD program. If it is a single-tasking system and cannot handle the print job in the background, and if there isn’t a large buffer in the plotter itself, it might take 10 to 40 minutes for the plot to finish, and the computer would be unusable for that period of time. In order to reduce wait time on this type of system, print spoolers were developed so that a plot could be printed to disk rather than to the plotting device, a process which might take 2 minutes instead of 20. The plot can then be spooled to the printer during a lunch break, after hours, or when the plotter is not tied up by another user. With the spread of multitasking systems and printers with large buffers, the use of spoolers is diminishing. On larger networks, a print server may handle printing tasks as a type of “smart spooler.” In other words, the print job might be sent to a file, or sent directly to the print server, and scheduled and spooled from there rather than from the originating machine. See spool. printed circuit board PCB. A board upon which electronic circuits are mounted, with the circuit connections etched, foiled, or blasted onto the surface of the board, usually on the side opposite the majority of the components. The etched electrical pathways, called traces, provide flat, convenient electrical contacts without wires. This is a very practical, lightweight method of doing away with wires and enables mass production of PCBs. The conventional wisdom is that printed circuit

boards were first invented in the 1940s, but the American Radio Museum has a radio in its collection dating from the late 1920s which is designed with a copper, blasted circuit on the underside of the board as shown in the following photos. Thus, the founder of the museum has fascinating evidence that the technology was introduced almost 20 years before its previously acknowledged invention.

Copper traces blasted onto the underside of a 1928 cabinet radio discovered by Jonathan Winter, curator and founder of the America Radio Museum (the wires were added later). This may be the earliest known radio based upon a “printed” circuit board.

Detail close-up of copper blasted traces on the underside. Small bolts and nuts were used to provide the electrical connection to the vacuum tube components on the top side. This historic example of one of the first printed circuit boards in existence is part of the American Radio Museum collection.

printer A device for transcribing information onto a medium which can be read directly or otherwise understood directly, or with a minimum of manipulation (as in mirror writing), by someone familiar with the communications medium (writing, illustrations, Morse code, seismographic charts, etc.). The printing medium is often paper, card stock, metal plates, or other portable media. printer control character A character which has a specific control effect on the action of a printer. The effects include line feeds, page feeds, carriage returns, mode changes, font changes, page length control, and other features that might be specific to the printer. Control characters can be sent to a printer before sending the document, in order to set up the printing parameters, or may be imbedded in the document itself to set typefaces, font sizes, text attributes, space, line feeds, etc. Printer control characters are handled transparently by word processing programs, which send the appropriate characters through a printer driver without explicit programming by the user. In cases where a user is imbedding printer control characters in the document, a hex editor, or ASCII editor with hex capabilities, is often used because the control characters cannot always be entered from the keyboard, as they lie beyond the range of the alphabet. Printer control characters are often not displayable, or may display as unusual symbols. printer control language A language designed to utilize the capabilities of a particular type of printer, or one conforming to a common standard such as Hewlett Packard Graphics Language (HPGL), widely used on plotters, for example. printer driver A file or program providing information on the physical, operational, and control characteristics of a printer. This may include relevant control codes, available font shapes and sizes, paper feed controls, etc. Typically an operating system or applications program will interact with a printer through a printer driver stored as a computer file. Many printer drivers may be available, and if the relevant one is not online, often a substitute can be found from a maker with a similar printer. Many different laser printers will function with the same commands as Hewlett Packard or Apple laser printers, and many impact and inkjet printers will work with Hewlett Packard or Epson printer drivers. printer emulation Any software which formats and outputs text to a device as though it were outputting to a printer. This way, for example, a word-processed program with all the text formatting, margins, and images can be sent through a facsimile transmission without first being printed and scanned. This saves paper and avoids problems such as slippage through the fax machine. printer font A font that is stored in the printer’s memory or on a hard drive directly attached to the printer. Dot matrix printers often have a few memory-resident font styles optimized for printing at low resolutions. High-end PostScript printers often have the capability of storing a variety of highquality Adobe PostScript fonts on a hard drive, for

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quick access and printing, so that the system doesn’t have to download fonts from the computer to the printer. printer server See print server. printing Printing is the production and reproduction of characters, symbols, and images on physical media for the purposes of preserving information or artistic works and/or to communicate or distribute them to others. Printing has long been associated with printing presses that enable many copies of a single master to be created. There is evidence that movable type, in the form of clay discs, may have been used in Crete as early as 1500 BC, and type was used in southeast Asia by the 11th century. In the mid-1400s Johann Gutenberg introduced movable type to the west. Type was set by hand until the early 1800s, when the first typesetting machines began to appear. Mass market microcomputer printers were introduced in the 1970s, and the home and prosumer desktop publishing markets became widespread in the mid- and late-1980s. Dry printing processes (e.g., photocopying with toner) became prevalent in the 1970s and have replaced a large proportion of wet printing processes (e.g., ink). A modern desktop laser printer costing $1000 is easier to use and more flexible than the letter presses of the 1960s that cost $30,000 or more. Color printing processes are numerous, from traditional ink presses which use spot color while running the paper through the press several times, once for each color, to process color, which uses cyan, magenta, yellow, and black dots to simulate a wide range of colors. Computer printers use thermal wax, dye sublimation, inkjet, and colored ribbons to create printouts that rival commercial color photocopies and photographs, and may someday supersede them. printing plates Printing plates were originally made of metal, wood, or other solid materials that could hold an image. These were used to insert illustrations into layouts which included movable type, or used in place of movable type. The plates were then mounted on traditional presses for use with ink reproduction processes. Mounting the plates was an art, since the individual pieces of type had to be fit around the image blocks, with the whole thing balanced in a case with spacers and pressure bars to keep it together. A small mistake or bumping the assemblage could cause a day’s work to end up in pieces on the floor. Today, printing plates often contain an image of the entire page, both type and images, greatly streamlining the process. The earliest printing plates were probably etched stones and clay tablets and, later, hand-carved wood blocks, which evolved into copper and steel engravings in the 1400s. In most cases the metal engravings provided finer detail and longer edition life than wood blocks, although M.C. Escher has created wood engravings that rival some of the finest metal engravings. Lithographic stones, which are “sensitized” to an image through a process of blocking off the negative areas with a greasy substance and then chemically etching the stone to repel ink, are a form of printing

plate used for fine pencil-like image reproductions. Printing plates were once created by hand with etching tools. This required a high degree of artistic and technical skill, as traditional plates had to be etched in reverse for the image to come out the right way when printed. Later, photographic methods almost completely replaced hand etching. More recently, laser and other automated forms of etching are beginning to replace traditional photographic methods. The number of reproductions that can be created from a single traditional plate is limited by the ability of the material to withstand the pressure of going through the printing press. Paper plates may only be able to make a few hundred impressions, soft metal plates or stones a few thousand, and denser metals a few tens of thousands. Thus, several plates of the same images may have to be prepared to print millions of copies of the same material. Even computer printers are limited by the lifespan of the printing drum (the modern equivalent of the plate) and the toner cartridge, which must be replaced every few months or so, depending upon frequency of use. Metal and asbestos plates can now be run through certain phototypesetting printers in the $6000 range to quickly create plates from computer files for use on traditional ink presses. These same desktop typesetting machines can produce dry-process laser printouts at about 1200 dpi. With the advent of desktop publishing, and printing presses that can go straight from a computer file to a drum on the press, the traditional concept of printing plates is almost obsolete. priority A level of access or usage which ranks higher than others. For example, on a computer system, operating system functions usually take precedence over user or network requests. On a server, such as a print server or network server, certain types of tasks may be handled first. In graphical user interfaces, a window which is clicked to the front may be assigned a higher priority, and greater proportion of processing time, than windows in the background. On most network systems, system administration functions take priority over user functions. Priority Access and Channel Assignment PACA. A Supplementary Bearer Service (SBC) scheme for handling radio communications transmission access and channel assignment. PACA is of interest to emergency service administrators and providers because it can be used to queue priority calls (e.g., emergency calls) when all channels are busy. ANSI standard 664 describes PACA queuing for priority call handling. Enhanced Priority Access and Channel Assignment (PACA-E) was developed in the mid-1990s to support up to 15 priority levels to support emergency service Personal Communications System (PCS) users and is described in ANSI T1.706-1997. In 1998, the Technical Subcommittee T1P1 submitted a draft proposal to the American National Standards Institute for a Stage 2 Service Description for PCS-based PACA-E. This document defined and described call setup procedures for priority access and priority egress for PCS systems. Typically, many more calls than usual are made during storms, natural disasters, and times of local

or national emergencies. This can overload landbased trunk lines and result in “fast busy” signals. Under these conditions, mobile networks also tend to become congested and PACA queuing has been studied as a means to handle busy channels in private and public wireless communications. PACA services can be accessed by the caller through a designated high-priority line or through dialing an assigned access code. In studies of the efficiency of PACA queuing, static queuing, and dynamic queuing conducted in the late 1990s, PACA compared favorably to the other methods. Priority Access Service PAS. A program of the U.S. government, in association with the National Communications System (NCS), to provide a means for national security and emergency preparedness (NS/EP) telecommunications users to obtain priority access to available wireless channels when needed for initiating emergency calls. PAS was established because wireless airwaves are not unlimited and are frequently congested during emergency situations. Priority access provides some level of guarantee of completing an important national security or emergency-related call. See National Communications System, Wireless Priority Services. http://pas.ncs.gov/ Private Automatic Branch Exchange, Private Branch Exchange PABX, PBX. A private telephone exchange, usually located in a business or educational institution, which can handle switching and other functions automatically. In an automated exchange, an operator is not needed to handle outgoing calls; connections can be made by first dialing “9” to access an outside line. PABX was derived from Private Branch Exchange (PBX) which originally was attended by a switchboard operator. Since private exchanges are almost all automated, the terms PABX and PBX are now used interchangeably. See Centrex. Private Cable Operator PCO. An independent cable operator providing video and telephony services to subscribers in niche markets such as multiple dwelling units. Many markets that are too small or specialized to be readily served by local exchange carriers (LECs) and thus alternative service providers have found viable ways to provide telecommunications services to these subscribers. These markets largely consist of apartment, motel, college, and housing cooperative dwellers. PCOs work in close cooperation with multiple dwelling unit (MDU) owners and managers. PCOs are supported, in part, by the Independent Cable & Telecommunications Association. private carrier A privately owned, commercial public messenger service or telecommunications service provider that may or may not be in competition with a dominant commercial carrier or governmentfunded service. private line In the early days of phone service, a private line was a line that went from one business or person to another, without necessarily going through a public phone exchange, or from one floor or room to another. It was not uncommon in the early part of the century for hundreds of wires to crisscross over

a street between one building and another. As more people were connected through public wiring systems that could handle multiple connections, the meaning of the phrase changed and, until about the 1960s, a private telephone line came to mean one that was not a party line. That is, the phone line was dedicated to only one user, and there was no possibility of a neighbor on the same exchange listening to a conversation or tying up the connection so another subscriber couldn’t dial a call. As private lines became the norm and party lines began to disappear, “private line” began to take on a different meaning, similar to its early meaning, referring to a direct connection between two businesses, between a home and a business, or between different departments in a business or institutional complex. Private Line Automatic Ringdown PLAR. A means of interconnecting two lines to form a “hotline” direct connection. privileges 1. On a telephone system, particular functions and services available on particular consoles or to particular individuals in a company, sometimes through keying in an access code. 2. On a data network system, access to specific applications, processes, devices, or data files. More specifically, file privileges are a record of the actions an individual or group member can take on a file, typically read, write, execute, or delete. PrivLM Private Land Mobile. PRMA packet reservation multiple access. PRML See Partial Response/Maximum Likelihood. probe A detection or measuring device, often with a narrow tip, used to assess temperature, wind, humidity, current, voltage, amperage, polarity, or other properties of air or electrical circuits. A probe is often used in conjunction with an analog or digital readout displaying the results of the probe. On a computer system, a probe is any software process which seeks out specified information or detects certain actions or types of data. The results of the problem are typically reported to another program, which analyzes the information and acts accordingly. A probe can be used to locate a particular site, user, address, archive, or other type of information. It may be used as a diagnostic tool to troubleshoot or configure a network. See protocol analyzer. process A software activity consisting of carrying out a set of predetermined or situation-influenced logical instructions, which may be low-level background processes integral to the operating system, router, or intelligent switcher, or higher-level processes related to the running of an applications program. process switching On a network, packet processing at process level speeds, without the use of a route cache, as is used in fast switching. A Cisco Systems distinction. processor configuration register PCR. processor configuration register. A computer processor-related programming register that typically contains a variety of bootstrap, break, data rate, and software configuration information. When spelled in capitals, it refers more specifically to the PCR in the Motorola 68000-family CPU.

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Prodigy One of the earlier commercial online services established by IBM and Sears Roebuck. Prodigy employed proprietary software to provide a graphical user interface access to the Internet. A lot of parents signed on to Prodigy to give their children educational access to online services. Like most of the largest commercial services, Prodigy earned revenues through placing ads on viewer pages. This practice is uncommon on the smaller, independent Internet Services Providers. Now that freely distributable Web browsers are available, proprietary software like that provided by Prodigy is less common. However, the ads remain, as many Web sites are subsidized by banner ad revenues. Producers Advocacy Group PAG. An ad hoc collective of independent public radio producers formed in October 1995. PAG members are responsible for some of the best known and respected public radio programs in North America, including drama, documentaries, comedy, and popular music programs such as The Thistle and the Shamrock. They have also provided educational programs at home and abroad. PAG funding is from diverse sources including charitable trusts and endowments, the Corporation for Public Broadcasting, and corporate and individual donors. See Association of Independents in Radio. Profile F, TIFF-F A black-and-white subset of the TIFF specification suitable for minimal facsimile document encoding but which has some extensions to the basic Profile S specification. See TIFF-FX. Profile S, TIFF-S A basic black-and-white subset of the TIFF specification suitable for minimal facsimile document encoding. See TIFF-FX. Profit Cap Regulation, Rate of Return Regulation Prior to the mid-1990s, the predominant means by which local monopolistic phone companies were regulated. Excess profits were required to be passed back to consumers as, for example, a rate reduction. By the mid-1990s, many companies changed to Price Cap Regulation. See Price Cap Regulation. Program Clock Reference A synchronization reference clock used, for example, in MPEG decoding. The PCR can synchronize a Station Time Clock (STC). An MPEG-2 video decoder chip can be designed to include an internal counter useful in a Station Time Clock, which can in turn be accessed by other components through an interface. program counter In general terms, a display or internal reference that keeps track of a location in a presentation (e.g., video or laserdisc program, TV broadcast, computer animation, etc.), sometimes to provide information to the viewer and sometimes as a reference point for searches or editing. In computer software execution, a program counter is a reference that monitors the location in a program that is currently being accessed. This is handy when debugging, testing a program, or tracing a logical path. programmable Any device which can be controlled or altered through logical instructions without reconfiguring the physical connections. programmable array logic PAL. In the design and manufacturing of computer circuits, a PAL is a circuit in which the OR array is predefined and cannot be

changed, but the AND array is programmable. This was a simpler approach that followed the development of programmable array logic (PAL). See programmable logic. programmable logic Circuit logic designed so that it can be reconfigured, as through linked flip-flops. In conjunction with memory circuits, programmable logic enables stored logic functions to be called upon and executed to configure the circuit. Programmable logic devices range from simple to complex (complex programmable logic devices [CPLDs]). The programmable logic array (PLA) is a more complex forerunner of programmable array logic (PAL). See programmable array logic. programming language Instructions used by a programmer to control computer operations. Programming languages are roughly divided into low-, medium-, and high-level languages. Low-level languages are those which most directly translate into machine instructions and interact most directly with the hardware architecture of the system. Machine language and assembly language are considered low level programming languages. Machine language programs are typically written in binary, with ones and zeros. Assembly language is similar to machine language, except that instructions are more symbolically represented, and routines can be written to pass control to different parts of the program. Machine language and assembly language are more difficult and time consuming for some to learn, and more difficult to trace and debug than higher-level languages. Medium-level languages include those which are reasonably powerful, somewhat cryptic in their instruction sets and syntax, but comprehensible enough that some of the commands resemble written English. C is a common, somewhat medium-level language. It is powerful, but requires a good understanding of memory allocation, pointers, and arrays, and takes some time to learn and to apply. C is a compiled language, which means that the code is compiled down to machine code in advance, before the program is run. Higher-level languages like BASIC and various authoring systems were designed to be easy to learn and to use, with commands and syntax that are fairly close to written English. They often are run as interpreted languages (although compilers may exist), and so do not require knowledge of how to configure and run a compiler before they can be used. Interpreted languages are translated to machine code as the program is run, and thus will execute more slowly than a program which is precompiled. Interpreted languages tend to be more limited, but also more portable, than lower-level languages. programming overlay, configuration overlay A covering made from membrane, plastic, cardboard or another material that provides information on a keyboard, keypad, or graphics tablet setup. Overlays were especially prevalent before graphical user interfaces, when complicated, difficult-to-remember control code combinations were used to run word processors and graphics programs. progressive scanning A method of displaying broadcast video signals in which each frame is transmit-

ted one after the other, rather than dividing the frame into sets of two fields interlaced. See interlaced. Project Athena See Athena project. promiscuous mode In data networks, an open mode in which the network interface controller (NIC) passes all the frames which it receives, regardless of the destination address, to high-level layers in the network. This is usually only done in diagnostic situations, or by users gaining unauthorized access to information from the system. In normal operations, frames are evaluated and selectively passed along if the destination address maps to that device. prompt n. 1. A mechanism for gaining the attention of the user to indicate that the system is ready for input or that input is required before continuing. 2. A prompt on a computer system may be in the form of a cursor, dialog box, flashing area, audible tone, or spoken message. 3. A prompt on an automated phone system may be a spoken question or suggestion to which the user can respond by typing in codes or, in some cases, by clearly speaking numbers or words. PROMPT Institute for Prospective Technological Studies. Founded in 1989 as a result of reorganization of the Joint Research Centre to monitor and analyze new sciences and technologies. Monitoring is carried out by by the European Science and Technology Observatory (ESTO). proof of concept A strategy for communicating an idea which is not readily accepted when communicated through verbal means alone. Proof of concept usually involves producing a prototype which is partially or mostly functioning, at least enough to show that the idea can work. Many new inventions or ideas are not believed until they are actually demonstrated. Edwin Armstrong spent years going against the stated assumption that frequency modulation was mathematically impossible, but eventually succeeded in his attempts. When it was shown that it was possible, resources were made available to develop and implement the technology. Proof of concept demonstrations are created to attract interest, support, or research and investment dollars. propagate 1. Pass along, continue, extend. 2. To travel through a material or space, to cause to spread out over a greater area. propagation The concept of propagation is intrinsic to every aspect of communication. When you send a message, sound, computer packet, modulated radio frequency signal, etc., you are propagating a phenomenon through space/time and any data along with any information coded into the propagation of the phenomenon. The study of propagation involves very fundamental research of transmissions media, such as radio waves, as well as higher-level research in ways to compose, encode, transmit, and route analog and digital signals. It also is dependent upon mathematical theories and applied engineering techniques for determining and implementing the most effective use of limited resources. Radio wave propagation, for example, can be facilitated by a number of physical phenomena associated with the Earth, its atmosphere, and various solar influences. The ionosphere is often used to propagate

radio waves, but there are other methods, including auroral, grayline (the sunrise and sunset zones), tropospheric scatter, and more. Since it can be time-consuming and impractical to physically test alternative propagation models for radio or computer communications, programmers have developed modeling programs that enable users to try different scenarios for efficient propagation. If the software is sophisticated enough to develop the different options as well as running unattended, a great deal of data can be generated in a short amount of time, with the software even suggesting the best alternatives from those discovered. These can then be tested on real systems. Propagation models are often used to develop prediction models. The U.S. Department of Commerce NTIA/Institute for Telecommunication Sciences makes software available online for modeling high-frequency radio wave propagation. See attenuation, backscatter, hop, ionosphere, routing. propeller head slang A technical person who may lack social graces. Derived from beanies (caps) with propeller tops that were popularized by the Beanie and Cecil characters of the 1950s; the caps became especially popular in geek/hacker culture in the 1980s when prominent notables wore them to scifi cons. proportional font A font in which each character is designed for maximum legibility and aesthetic beauty, so the width of individual characters varies with the needs of the character and its relation to other characters. Most high-end printing uses proportional fonts. See ligature. Contrast with monospaced font. Prospero The Prospero Directory Service. A client/ server directory resource on the Internet, accessible through the prospero://...../ Uniform Resource Locator (URL). prosumer A combination word derived from professional and consumer, intended to indicate a level of literacy or competency somewhere between a skilled layperson, and a technical professional. In other words, the reading level or skill level for the product or service requires more knowledge than possessed by an average layperson but not as much as might be required by a technician or design engineer in that industry. Computer technology has brought many new products into the marketplace that were previously used only by professionals with years or decades of experience. The printing, desktop publishing, and desktop video industries are good examples of sectors that now include a large number of prosumer products. PROTECT Act A bill introduced to the U.S. Senate by Senator John McCain and others in April 1999. It is strongly associated with the Safety and Freedom through Encryption (SAFE) Act and covers the use and export of encryption products. It seeks to guarantee the right to domestic use of encryption products and to ease export restrictions, but not to the degree suggested in the version of the SAFE Act debated at the time. In June 1999, it was approved as S 798 by the Senate Commerce Committee. protocol 1. A code of etiquette and procedure. 2. An agreed-upon system of configuring a communications network and carrying out transmissions flow

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so that connected systems can “talk” with one another and exchange information. There are many different types and levels of protocols used in computer networking and telephony. Internet Protocol (IP) is one of the most widespread and important general network protocols and File Transfer Protocol (FTP) is one of the most prevalent of the specialized utility protocols. protocol, networking In networking, a procedure for organizing and exchanging data transmissions that may include specific rules and/or formats. Protocols for various Internet transmission and application protocols are well documented in online RFCs (Requests for Comments), some of which are standards or draft standards. For technical information on protocols, consult the RFCs. Many of the important protocols are briefly described in this dictionary under individual entries, but especially important on the Internet are Internet Protocol, Point-to-Point Protocol, and Transmission Control Protocol. See the Appendix for a list of RFCs related to Internet protocols. protocol analyzer ProtAn. A diagnostic tool that can capture a segment of network data traffic to reveal its characteristics. A protocol analyzer is useful for educational programs, systems development, systems monitoring, and troubleshooting. In the early days of computer bulletin board systems (BBSs), there were relatively few protocols; they were fairly simple in design, and problems with a network connection were often traceable to a hardware device or break in the physical link. Since then, networks have evolved, the number of protocols has burgeoned, and network capacity and speed are now further optimized through sophisticated software processes. A protocol analyzer has become an indispensable tool for network administrators and, given the learning curve on all these new technologies, more sophisticated expert system versions have been developed to help the administrator search and evaluate the data based on heuristics and common scenarios. The information extracted by the ProtAn may be displayed as text, tables, graphics, or a combination of these. Hardware or software filters help the user to separate out data of particular interest. Much of the information extracted by the ProtAn is contained in the headers associated with packets, but general statistics and overall characteristics are also important. Wireless communications, using radio frequencies, differ somewhat from wired communications using conductive wires or fiber optics. There are ProtAns for both categories of media that are similar in concept but somewhat different in detail: On wired systems, much of the protocol analysis is handled with software tools on a computer attached physically to the wired network. The analyzer may be used in conjunction with a decoding engine to display information about the captured data. Analyzers vary in design, but they can usually capture data from a live network or examine data previously captured and stored for later analysis. A ProtAn can reveal normal activities like traffic load and utilization (e.g., peak usage),

server queries and lookup activity, domain name resolution, and the ASCII contents of a data stream. It can also help detect potential problems, including long pauses or duplicate or missing sequence numbers. A wide variety of packet types can be analyzed by freely distributable protocol analyzers, including AARP, ASCEND, BBOTP, FTP, LDAP, LDP, TCP, TELNET, TFTP, WLAN, and many more. Commercial ProtAns are also available. In wireless communications, self-contained transceiver units with built-in software are more commonly used or may be designed as portable units with serial (or other) interfaces to transfer the data to a desktop computer for further processing. Since wireless radio and telephony systems are increasingly prevalent, some commercial wireless protocol analyzers (WPAs) can provide data analysis and evaluation of cordless phone signals, trunked radio data and voice channels, and digital private telephone lines. A more general and encompassing tool for overall network performance testing and evaluation is a performance analyzer. This tool may incorporate a protocol analyzer, protocol simulator, and other query generation and evaluation tools or may be used in conjunction with separate modules handling the various functions. In terms of network integrity and security, keep in mind that a protocol analyzer may be inserted into the communications circuit to evaluate its characteristics. Since some channels on a network may be involved in transmitting signaling information, the ProtAn could be used to manipulate signals on the network, thus interfering with normal operations. See probe. Protocol Data Unit PDU. A data unit consisting of control information and user data which is exchanged between peer layers. In the Open Systems Interconnect (OSI) layered networking model, a PDU is associated with each of the seven layers (as well as a Service Data Unit (SDU)). The PDUs are used for peer-to-peer communications. At the lower layers of the model, the PDUs have been specified as Transport, Network, Data Link, and Physical, associated with segments, packets, frames, and bits, respectively. Services for the PDUs may be conveyed via Service Data Units (SDUs) in lower layers. Higherlayer PDUs are encapsulated in lower layer PDUs (a header is added). See asynchronous transfer mode, LLC, RFC 1042. protocol simulator An implementation tool that enables developers and network service providers to test and verify protocols prior to setting them up on a network. A simulator typically allows the tester to set up data rates and basic operating parameters and to initiate and respond to queries and perform the other basic functions of a telecommunications network. It may be used in conjunction with a protocol analyzer to evaluate performance characteristics and perform fine-tuning prior to implementation on a client’s system. A protocol simulator may be designed to simulate one specific protocol or related

group of protocols or may be capable of simulating a variety of protocols, depending upon the product. Providence Group An informal name for a group of scientists who contributed their time and energy to research that was turned over to Alexander Graham Bell and never credited as promised. As spokesperson for the members of the group, Henry W. Vaughn wrote to Bell on February 1, 1900 to express his disappointment at Bell’s conduct and stated in part: “... you have apparently forgotten or care little for the work done in your behalf by a little band of Providence scientists of which I was a member. Prof. John Pierce, shortly before his death, assured [sic] me that at heart he believed you appreciated our labors and the value of the results of our experiments which were all turned over to you....” See Bell, Alexander Graham; telephone, history. proxy An agent, deputy, or authority acting on behalf of another. proxy, computer A software intermediary or agent that acts on behalf of clients and can act as a server or client. Proxy systems are frequently placed in points of a network where there are connections between LANs, or between a LAN and the Internet, or between a LAN and another external system such as an Internet Services Provider (ISP) or phone network. Proxies act as protocol managers and security administrators, and handle requests by servicing them or passing them through to other services. In cases where they are passed through, the proxy may interpret and modify a request before sending it on. Conceptually, a proxy server differs from a gateway in that requests are passed through as though from the original client, whereas a gateway handles the request as though it were originating from the gateway, thus forming a barrier between the server of the request and the client. A system can be configured as a security firewall to allow selective passing of messages through its portal. See firewall, gateway. proxy server A software program that serves up requests on behalf of another process or machine. As such it can manage processes on a single machine, or broader server functions on a local or public network. In computer networks, a proxy is an intermediary server providing services between a client or clients and another server, usually a primary or secured server. Proxy servers are commonly used to improve network efficiency and security. By filtering requests, proxy servers can reduce the load on other servers and handle specific types of tasks or frequently requested tasks. If connected to the Internet, they can be used to manage common processing tasks or storage dedicated to warehousing frequently requested documents, files, or Web pages. A proxy server need not necessarily be configured as a security mechanism. It may simply handle overflow requests for the primary server when it is busy without any concern about who is making the requests. However, a proxy server lends itself to screening requests and is often used to help secure

communications, even if only in a minimal sense. Proxy servers can be configured to selectively control access to authorized users and, as such, can act as gateways or firewalls themselves, or they can work in conjunction with gateways or firewalls on one or both sides of the gateway or firewall link. See firewall; gateway; proxy, computer. PRS 1. personal radio service. 2. See Police Radio Service. PRSM Post Release Software Manager. PS See paging system. PSA Protected Service Area. PSAP See Public Safety Answering Point. PSAP Pro A commercial E-911 database program developed by Public Safety Associates, Inc., in collaboration with MapInfo. PSAP Pro enables telecommunications providers to route E-911 calls to an appropriate Public Safety Answering Point (PSAP) for the dispatch of emergency personnel. The software includes data for the U.S., 10-digit emergency numbers, address information, geographical information (latitude and longitude), and jurisdictional boundaries for PSAPs. The software is based upon a product distributed earlier by Public Safety Associates and the National Emergency Number Association (NENA). See Pseudo-Automatic Number Identification, Public Safety Answering Point. PSDN packet-switched data network. See packet switching. PSDS Public Switched Digital Service. PSE packet-switched exchange. Pseudo-Automatic Number Identification P-ANI, Pseudo-ANI. A non-dialiable telephone number assigned to cellular transceiver sites or sectors to enable emergency call routing for mobile phone subscribers. Since mobile users are always on the move, there is no direct way to correlate the cell phone number with a house address or business street location. By the mid-1990s, requests to the Federal Communications Commission (FCC) to facilitate improved wireless emergency location services resulted in some progress. In Texas, a system was developed in which virtual phone numbers were assigned to cell sites in fixed locations. These numbers are not dialed, but they enable a number and a location to be related to one another so that if a specific site is being used by a mobile user, it provides a ballpark idea of where the caller might be. FCC rules for mobile emergency location services began to be phased in beginning in 1996. The rule-making has changed several times to reflect improvements in technology since that time. There is more than one way to implement P-ANI for emergency services. P-ANIs may be statically assigned to cell sites or may be dynamically assigned when a call is received. The size of the region and the demand for phone numbers are factors that may influence the choice. In one implementation of Pseudo-ANI, a mobile user calls E-911 (Extended 911), the Mobile Switching Center (MSC) sends the P-ANI together with the WS-ANI to the appropriate emergency routers so that an Automatic Location

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Identification (ALI) host can correlate the P-ANI with a location. Feature Group D trunks may be used to transmit calls to E-911 routers. Once the emergency service has been contacted, the situation can be assessed, the caller can be contacted by a Public Safety Answering Point (PSAP) dispatcher, and the appropriate help dispatched to the caller’s approximate location if the caller is unable to specify the exact location. The P-ANI system may eventually become obsolete. Increasingly, Global Positioning System (GPS) receivers are being incorporated into cell phones, which means that GPS readings of the caller’s location, within a couple of hundred feet or less, can potentially be transmitted to emergency services once E911 services have been called. This would free up the nondialable numbers for use as dialable telephone numbers and enable more precise determination of the geographic location of a caller in distress. See Automatic Number Identification, E-911, Global Positioning System. pseudocode 1. A software program or process listing written in somewhat plain language (not a programming language per se) which delineates the steps and algorithms in a process in order to outline or draft it so it can be transcribed into a programming language. Many programmers find pseudocode more practical and useful than flow charts for drafting software program flow. 2. P-code. A type of code which is compiled down to an intermediary stage without being specifically tied to one computer architecture. A number of high level languages can be compiled down to P-code, so they can execute faster (and sometimes to protect proprietary programming algorithms); they can then be distributed for a variety of computers. Each computer on which the P-code is run will need software to execute the program to do any further platform-specific translation of machine instructions which might be needed. PSI 1. packet switching interface. 2. Policy Studies Institute. U.K. government consortium. PSK See phase shift keying. psophometer A diagnostic instrument that provides a visual reading of noise at various frequencies in audio circuits. It is a form of voltmeter incorporating a type of band-limiting filter called a weighting filter. Weighting filters aid in testing in such a way as to accommodate perception of sound at different frequencies and levels. Depending upon the model of instrument, various types of noise, including longitudinal noise and metallic noise, may be measured as to their presence, level, and relationship to loss in a transmission. Selective level meters that are used as voice band analyzers may also be suitable for use as psophometers. The frequency ranges tested by this instrument are within human hearing ranges, with emphasis on frequencies used in speech (if measuring speech circuits) or music (with a broader range than speech circuits). Psophometers are used to test telephone, sound system, and broadcast networks. They may be integrated with other audio testing tools (e.g., distortion meter) and audio frequency generators.

Psophometers for testing telephone circuits may be further specialized to accommodate local telephone standards (e.g., North American vs. European standards). The ITU-T has published recommendations for the use of photometers on telephone-type circuits (O.41, P.53). PSTN See Public Switched Telephone Network. PSTN/Internet Interworking Service Protocol See PINT Service Protocol. PSU Packet Switch Unit. PSWAC See Public Safety Wireless Advisory Committee. PSWN Public Safety Wireless Network. PTE See SONET path terminating element. PTFE polytetrafluoroethylene. A synthetic material useful for insulating wires in environments where they might be subjected to heat. PTI Payload Type Identifier. An ATM cell header descriptor which indicates the type of payload in the cells, such as user or management. See cell rate. PTN Public Telecommunications Network. PTO public telecommunication operators. PTS 1. Personal Telecommunications System. 2. See Presentation Time Stamp. 3. Public Telecommunications System. PTT See Post Telephone & Telegraph administration. Public Access Profile PAP. A profile is defined by the Open Systems Interconnection (OSI) model as a combination of one or more base standards and association classes, necessary for performing a particular function. The PAP is an ETSI-published profile incorporated into Digital European Cordless Telecommunications (DECT) as a test specification. See Digital European Cordless Telecommunications. public address system PA, PA system. A system designed to receive and transmit amplified sound, especially voice or music, to a wide audience. It may be acoustical or electrical. An acoustical PA may amplify through a horn-shaped object that directs sound. An electrical PA is familiar to most people as the microphone, circuits, and speakers installed in most public schools and hospitals. See amplifier, intercom, loudspeaker, sound. public key In public-key encryption schemes, this is the key given to the public to act as one of the tools to create a message addressed to the person to whom the key corresponds. The recipient then uses his or her private key to open and read the encrypted message. It is important to create a private key password that can be remembered for a long, long time; otherwise it isn’t very useful to distribute it to the public because it will not be possible to decipher encrypted messages if the password is forgotten. Public-Key Cryptography Standards A set of standards for public-key cryptography developed by RSA Laboratories in cooperation with members of an informal consortium that included Apple, Lotus, Microsoft, MIT, Sun, and others. The Open Systems Interconnect (OSI) Implementor’s Workshop has cited PKCS as a means of implementing securityrelated aspects of the OSI standards.

PKCS are compatible with the ITU-T X.509 standard and support binary and ASCII data formats. They support algorithm-specific and algorithm-independent implementations and provide an algorithm-independent syntax for digital signatures, envelopes, and extended certificates, to facilitate interoperability. See RSA Security Inc. public-key encryption An encryption scheme that often also incorporates an authentication scheme in which public keys are distributed for encryption of messages to the person owning the key, and private keys are established for decrypting messages. Sometimes the encrypted message is differentiated into two components: signature and message. It is possible in some systems to encrypt the signature to provide authentication without encrypting the message. Pretty Good Privacy is a public key encryption technology that has been incorporated into various Internet applications, for example, in email through MIME. By the late 1990s, there was a trend to promote public key encryption as having the same legal and commercial force as handwritten signatures. See Blowfish, Diffie-Hellman, PGP/MIME, Pretty Good Privacy. public-key infrastructure PKI. A general term for the foundation, architectural framework, and basic components that comprise a public key encryption system. In general, industries are in favor of the security provided by PKIs, but implementation has been slow, due to the extra steps and occasional confusion that arise from installing, using (and remembering to use) PKI-based systems. In spite of the difficulties, by the end of 2000 a number of firms were seeking solutions for the development of easier-touse PKIs, especially for mobile business/commerce applications. See public key encryption, wearable public key infrastructure, wireless public key infrastructure. Public Land Mobile PLM. A network administered for the purpose of providing publicly accessible, land-based mobile telecommunications services. It may be considered as intrinsic to or as an extension of the public switched telephone network (PSTN). A land mobile service is essentially a communications service between base stations and land mobile services, or among land mobile stations. Services thus provided include cellular telephony, PCS, and other governmental, industrial, and business mobile services. Since PLM services are used in part for public safety and emerging Intelligent Transportation Systems (ITSs), there has been concern over the allocation of sufficient radio frequency spectrum to support the system as it grows and changes. It is anticipated that approximately 240 MHz of additional spectrum will be needed over the next decade to satisfy these needs. Public Radio International PRI. A major producer, financer, and distributor of more than 400 hours per week of world audio programming from international and independent producers, including popular programs such as As It Happens, BBC World Service, The World, Beyond Computers, and others. PRI was formed in 1994 from American Public Radio (APR),

which had operated since 1983. The majority of programming is distributed through noncommercial public radio stations. See National Public Radio. http://www.pri.org/ Public Safety Answering Point PSAP. Services that support the administration of emergency services and the handling of emergency telephone calls. PSAP stations are typically centralized facilities with supervisors and a number of trained public safety communicators and dispatchers. PSAP responsibilities are somewhat tailored to their individual regions but, in general, their staff members monitor safety patrols and justice information systems, and process emergency service calls and nonemergency law enforcement-related calls. PSAPs must satisfy a number of requirements in order to provide reliable, unified emergency services. For example, PSAPs must be able to handle calls from E-911 services from a variety of types of callers, including those using mobile phones. They must also be able to communicate with hearing-impaired callers. In many cases, upgrades to PSAP equipment have been necessary to accommodate the specialized needs of the growing mobile telephone community and the new regulatory requirements by the Federal Communications Commission (FCC). Some large phone service providers are now providing services to aid in the implementation of emergency regulations to help minimize the impact on and costs incurred by PSAPs. See Pseudo-Automatic Number Identification. Public Safety Wireless Advisory Committee PSWAC. A committee established in 1995 by the Federal Communications Commission (FCC) and the National Telecommunications and Information Administration (NTIA). The PSWAC provides advice on the various public safety agencies’ wireless communications requirements through 2010. This includes identification of emerging technologies and recommendations as to their utility and role, and emphasizes the importance of semiconductor technologies. Public Service Commission PSC. A state regulatory authority for communications. See Public Utility Commission. Public Switched Telephone Network PSTN. The national telephone infrastructure consisting of the RBOCs, the IXCs, and LECs. The PSTN is intended to further the goals of universal access to telephone service described in the 1934 Communications Act. Public Switched Telephone Network history PSTNs have long been regulated in the U.S., beginning with the Post Roads Act in 1866. The Bell System and AT&T are an intrinsic part of the history of the PSTN; their dominance, research contributions, and many voluntary and required reorganizations have formed a colorful history in which the rewards of a competitive market, and the demands of independents to further fair competition have often been difficult to sort out and maintain. AT&T was divested from Western Union in 1913 and mandated to provide access to independent carriers

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across its long-distance network. Further divestiture occurred in 1975, and a Modified Final Judgment, approved by Judge Harold Greene, came into effect on 1 January 1984. The Justice Department formed 22 Bell Operating Companies (BOC) from AT&T, which were organized into seven regional Bell holding companies. Until 1991, when the Supreme Court granted wider privileges, the BOCs were not permitted to provide electronic data services. Service divisions that resulted from the restructuring fall into the following general categories, which are described more fully under individual headings in this dictionary: Local Access and Transport Areas (LATAs), Local Exchange Carriers (LECs), Independent Telephone Companies (ITCs), Interexchange Carriers (IXCs), and Other Common Carriers (OCC). Public Utility Commission PUC. State regulatory commission with jurisdiction over phone companies. See Public Service Commission. publish v.t. To consolidate, organize, and present information in one or more communications media such as print, video, or Web pages. While publish in its broadest sense can mean to publish music or voice, and certainly music and voice are often included in multimedia publications, publish nevertheless tends to be used in conjunction with visual media, or media which are predominantly visual, with record more often used to describe the publishing of sound media. The concept of publishing has broadened with the new media-rich technologies. In fact, the creation of software is called software publishing, even though software itself is diverse and sometimes quite different in form from traditional publications. Nevertheless, it can be broadly stated that visual information brought together and organized on some media, in order to provide information and/or entertainment, has been published. PUC See Public Utility Commission. pull box In wiring installations, a box inserted into a long cabling run, especially at major junctions that allows easier access and working room for changing existing cables, removing them, or running new ones. pull rig A piece of rigging equipment used to install or deinstall a line conductor. The pull ring facilitates this with a puller, a pulling rope, and a take-up reel for winding the line. pulling eye A round open device incorporated into lines and other objects which are intended to be threaded through conduits or similar tight spaces. The eye is used to attach a line to thread the line. See birdie. pulling glass colloq. Installing fiber optic cable, especially by pulling it through with various implements for this purpose, as opposed to air-blowing. See pulling eye. pulling strength This is an industry- and materialspecific term but, in general communications terms, it refers to the maximum amount of pulling force that can be applied to a material or object (such as a communications cable) before its physical or data transmission properties are compromised. Pulling

strength varies from material to material; a fine electrical wire has a lower pulling strength that a medium-gage bundled wire. It is important to have a good intuition and established procedures regarding pulling strength when installing and deinstalling wire and optical cables, especially when pulling through conduits stretching around corners. pulp A low-grade “prepaper,” that is, a material processed from natural plants such as wood or hemp that is made from the courser parts of the plant or which has undergone less processing than fine-grade paper. Pulp has long been used as an alternative to more expensive long-fiber bleached papers or those including a high proportion of cotton plant matter (as is found in fine stationery papers). Pulp has long been used in newspapers, comic books, low-budget alternative books and papers. It was also historically used as an insulating material. See pulp insulation. pulp insulation A type of paper-based winding insulation historically used with electrical wires, especially internal wires in components or appliances (e.g., stoves) that had a low likelihood of being bent or twisted during use, although for a while pulp was even used on some outside wiring. Materials to increase water-resistance or to reduce erosion were sometimes applied to the outside of the pulp, such as wax or shellac. Pulp is now rarely used, as synthetics are cheap, effective, and readily available, but pulp insulation can still be found inside many vintage electrical devices. Fabrics such as cotton were sometimes used in place of pulp, where greater flexibility was needed, as on electric cords for plugging in lamps. See pulp. pulse 1. A rhythmic beating, throbbing, vibrating, or burst of electricity, sound, or light. 2. A briefly transmitted electromagnetic wave or modulation. 3. In telephony, a brief, timed signal sent out by a pulsedialing phone to indicate the desired destination. 4. In radar, a brief burst of microwaves. pulse amplitude modulation PAM. A common means of converting a continuous stream of information into a series of samples with assigned discrete values used in analog to digital conversions. PAM takes into consideration the fact that for many media, it is not necessary for the entire communication to be transmitted for it to be understood. For example, in a voice conversation, if you were to take samples of the speech at frequent intervals and transmit those to a human listener, enough of the information is retained that most people can still understand what was said, even if subtle parts of the original message are not included. The more frequent the samples, the closer to the original, up to the limits of human perception. For example, moving images played by a film movie projector are typically displayed at the rate of about 24 to 30 frames per second. Higher sampling rates (more frames per second) do not substantially improve the quality, since humans can’t see the individual frames, and the whole is perceived as motion, rather than as a series of still images. PAM is a baseband transmission multiplexing scheme used, for example, in Digital Subscriber Line (DSL) transmissions. PAM uses the amplitude of the

modulated information to determine the amplitude modulation characteristics of the transmission. PAM’s advantage is that it uses lower frequency bands, which are less subject to attenuation and crosstalk, two areas that have caused concern in DSL installations over existing copper wires. See carrierless amplitude and phase modulation, pulse code modulation. pulse code modulation PCM. PCM is a means of sampling a signal and assigning values to the individual samples. As such it is a fundamental digitization technique that forms the foundation of many aspects of electronics, particularly voice-carrying transmissions and audio recording technologies. Because the signal at the end of the transmission carries the same data as the signal transmitted at the beginning of the transmission, the data portion is essentially a “lossless” process compared to analog signals in which the information contained within the signal can be affected by attenuation and other factors. (Attenuation can also occur in digital transmissions, but it compromises the strength of the signal more than the information content of the data itself; loss of data through aging or lossy compression/decompression results from implementation rather than from the essential characteristics of the digital transmissions technology.) The digitization process inherent in PCM also enables error correction, compression, and encryption technologies to be applied to the data in ways that are not practical with analog transmissions. PCM was one of the historic digitization schemes that did not come into use until sometime after the theory had been developed, but once it became practical, it became a significant aspect of communications that is still used today. A number of inventors were responsible for discovering, rediscovering, and applying PCM. Pulse code modulation can be carried out in a number of ways but generally the process involves • • • • • •

establishing a resolution at which the signal will be sampled, establishing cutoff levels within which the signal will be sampled, filtering the incoming analog signal, sampling the signal and assigning values to the samples, converting the quantized sample into a digital bitstream, and reconstructing the signal at the receiving end.

It is not uncommon for the digital signal to be converted back to analog at the receiving end, as on analog telephone voice lines or analog stereo equipment. However, more and more phone services and stereo systems have digital lines and components and it may only be a few years before these transmissions and playback systems are predominantly digital. Since PCM digitization can be applied in a number of ways, not all PCM transmissions are compatible, and different schemes are used in Europe and North America.

PCM is widely used in telecommunications. With Alaw/Mu-law encoding, it is the most common encoding scheme used for telephone conversations. Sampling rates may vary, but 6000 to 10,000 times per second is typical. Eight-bit sampling is sufficient for voice communications. In contrast, 16-bit sampling or higher is preferred for quality music sampling. Pulse code modulation is sometimes used in multiple modulation schemes. For example, PCM subcarriers may be used to frequency modulate another carrier. See differential pulse code modulation, pulse amplitude modulation, sampling. See individual listings for scientists Kotel’nikov, Reeves, Shannon. See the Pulse Code Modulation History chart for some of the highlights in the development of PCM and related technologies. pulse compression In radar, a technique of using long pulses to increase the energy of the received signal while still retaining the resolution of short pulses. pulse dialing A means of transmitting phone numbers through a phone line by converting the length of the signal that occurs with the rotation of the rotary dial into electrical pulses. Pulse dialing phones are becoming rare and pulsed signals will not work with online automated menu systems. The other common means of dialing is through tones, with each number assigned a particular tonal frequency. See tone dialing. pulse dispersion The gradual spread of pulses as they travel over some transmissions medium. pulse duration modulation PDM. A type of pulse modulation in which the length of time of the modulation is controlled to impart information. See pulse code modulation. pulse generator A device for creating pulses of various specific amplitudes, shapes, repetition rates, and durations. Thus, a pulse generator can be used in a variety of pulse modulation schemes. pulse inverter A wideband, low-distortion waveform-modifying device which enables an output wave to be the inverted form of the input wave. pulse modulation A simple means of modulating a signal by applying pulses of current (often just on or off) without changing the frequency of the signal. See pulse code modulation, pulse width modulator. pulse repetition frequency PRF. The number of pulses which occur in a unit of time, such as the number of pulses per second or minute. Pulse repeition frequency is important to many technologies, especially those that involve signaling or synchronization. pulse width modulator PWM. A digital circuit that can be configured to produce a pulse with desired characteristics (period, cycles, etc.). Thus, it can be used for a variety of purposes, including the control of the speed of mechanisms or to modulate transmission signals. pulsing Using discrete bursts of sound or electromagnetic energy to send signals through a communications medium. The strength or duration of the pulses may have relevance, depending upon the system. In older phone systems, pulses were used to indicate the number dialed. Beacons often use pulses to signal their presence and location. See pulse dialing.

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Pulse Code Modulation (PCM) History – Highlights • • • •

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In the 1870s, J.E. Baudot inserted sychronization signals between baseband signals to multiplex the signal. This was the beginning of time division multiplexing (TDM). Edmund T. Whittaker developed a mathematical basis for sampling theory, in 1915, that is now applicable to pulse code modulation and time code modulation. Some sources cite that in 1926, P.M. Rainey at Western Electric was the first to patent PCM methodology. The author was unable to locate documents to confirm or deny this claim. In 1933, Russian scientist V.A. Kotel’nikov built on the mathematical basis described earlier by Whittaker and demonstrated how discrete samples could represent continuous functions. He later applied his theories to advances in radio astronomy and satellite communications. While working in Paris with ITT Laboratories, Englishman Alec H. Reeves described PCM as a means for transmitting voices. His invention was patented in France in 1937 (#833,929, #837,921) and subsequently patented in Britain and the U.S (#2,272,070 – 1942). Reeves was later to research optical communications at Standard Telecommunication Laboratories in the late 1950s and applied for further patents for PCM technologies in the early 1960s. In 1945, E.M. Deloraine developed a different method for digitizing speech, now known as delta modulation, which Reeves felt might have future applications when used in conjunction with PCM. In the U.S., Bell Laboratories explored the technology under Harold S. Black and developed a PCM system that was used by the U.S. Army Signal Corps. By 1947, Bell Telephone Laboratory researchers had an experimental 96-channel PCM system running between New Jersey and New York City and W.M. Goodall authored “Telephony by Pulse Code Modulation,” in the Bell System Tech Journal the same month that Harold Black authored “Pulse Code Modulation” in the Bell Lab Record. In the late 1940s Claude Shannon, John R. Pierce, and Bernard M. Oliver developed information theory related to PCM, based on groundwork laid by Harry Nyquist and Hartley, that provided support for Kotel’nikov’s theories. Oliver, Pierce, and Shannon authored “The Philosophy of PCM,” in November 1948. In December 1948, Reisling’s “Companding in PCM,” was published in the Bell Lab Record. By 1951, the Nippon Telegraph and Telephone Public Corporation (NTT) labs were researching PCM. Dr. Kiyasu, who headed up electronic switching research for NTT in the 1960s, invented the reflected binary pattern scheme for encoding. Frank Gray, another Bell Laboratories engineer, developed a binary code system for pulse code communications described in 1953 and 1958 U.S. patents (#2632058, #2,632,058). In 1958, the Paris-based Laboratoire Central de Telecommunications of ITT included PCM in their research and development of electronic switching systems, work that was followed up in the London and U.S. labs of AT&T. In 1962, after almost a decade of development and testing, Bell Laboratories developed a working digital T1 carrier system that could transmit 24 separate voice communications over a single twisted-pair wire. The data for each conversation were encoded at 64,000 bps. By 1964, British Telecom had experimentally introduced PCM systems into junction cables. By 1965, T1 systems had also been designed and introduced for use in Italy. In Japan, a DEX-T1 pulse code modulation switch was being developed by NTT, with a prototype released in 1967. A. H. Reeves predicted that “... by the year 2000, pulse code modulation in some form will be the very backbone of the world’s communication systems... for the year 2000 there is no doubt that optical PCM methods will have to be used....” In 1967, a PCM cable route was opened in London by British Telecom. The following year the London Post Office installed a PCM-based exchange, which opened in September 1968. This was the first to implement switching in digital form and demonstrated that digital switches could work within an electromechanical system. By the early 1970s, audio equipment and recording companies such as Denon and Nippon Columbia were using PCM techniques to create digital sound recordings. Through the 1970s, the technology improved and spread until, by the late 1970s, various international standards for PCM were adopted and commercial PCM-based recorders were available. By the early 1980s, consumer markets for audio CDs were being established.

PUMA Product Upgrade Manager. A manager in charge of updated versions of a product, which may include error fixes, embellishments, interface changes, or structural adjustments. punch v. 1. To prod, poke, or perforate. 2. To perforate small regular holes in paper, card, fine metal, or other similar flat surfaces in order to create a semipermanent record of a code. Early gramophone cylinders, player pianos, patterned looms, music boxes, and punch card reading computers employed this technique to encode and store information intended to be read back later. See Hollerith card. 3. To apply pressure to an enclosure in order to pop out a small section, to enable the threading of circuit lines. 4. To apply pressure with a punchdown tool to a wire and terminal block. See punch down, punchdown tool. punch card Any sturdy paper or card stock in which parts of the card are punched out according to a code that can later be reread and decoded to produce the original meaning. Punched codes in various media have been around for centuries, with early ones incorporated into music boxes. The Jacquard loom incorporated punch cards to store loom patterns in the early 1800s, revolutionizing the textile industry and causing a substantial uprising among human weavers, whose jobs were obsoleted by the automation. Punch cards can be used to store many sorts of codes and variations of the concept are used in music boxes, player piano rolls, older computing devices, etc. See Hollerith card, zone punch. punch down v. [The verb form is two words, the noun form often combined into one word.] To apply pressure, usually with a specialized punchdown tool, to wires looped around a terminal block to strip insulation from the end of the wire, and insert the conductive surface between the prongs of the terminal in order to make a solid, clean connection. See punchdown block, punchdown tool. punchdown block, terminal block, cross-connect block A multiterminal block designed to facilitate electrical cross connections, especially those which may change from time to time or where future expansion is planned. Very common in telephone installations where a multiline wire is threaded into a building and then, at the punchdown block, is split into pairs to wire several individual phones in different locations. See punchdown tool. punchdown tool A handheld wire installation device that resembles a screwdriver with an extremely short, notched shaft. The handle may be spring-loaded. The ends are designed to fit particular sizes of terminals and used to quickly connect wires to a punchdown block. The wire is looped over the prongs of one of the terminals in the block, and the punchdown tool is pushed against them to spread the prongs and snap the wire securely into place. Some punchdown tools will punch and cut. See punchdown block. Pupin, Michael Idvorski (1858-1935) An Eastern European-born American inventor and educator. He studied low pressure vacuum tube discharges and X-rays, and invented an electrical resonator and inductive loading coils, paving the way for long-distance wired transmissions.

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Telecommunications wires can often be attached to wiring blocks with screwdrivers and pliers, but the task becomes tedious if there are many wires to connect. A punchdown tool is specialized for attaching and trimming the wires more quickly and readily than generalpurpose tools.

Pure ALOHA See ALOHA. PureVoice See Qualcomm Code Excited Linear Predictive Coding. purge v. To rid of, or remove. In computing, there are many instances where the operating system or applications software retains information, files, or backup files until explicitly instructed to remove them. For example, many workstations enable the number of backup versions of a file to be set automatically. Thus, each file may be saved under a slightly modified name or with the same name, but a different time stamp. Purging the directory deletes all the multiple copies of each file and retains only the most recent. Similarly, many desktop publishing and word processing programs save a history of edits and additions within the file, so that the information is available for recovery, if needed. This may result in very large files. These programs often will purge the file edit history if the user selects Save As instead of Save, resulting in smaller, cleaner files (but which are more difficult to recover if problems arise). Many database programs retain information such as customer names and addresses even if the customer entry has been deleted. In this way, it can be recovered if the entry is needed in the future, but doesn’t clutter up directories or slow down searches in the meantime. There may be a menu item called Purge which allows you to permanently remove these records, or in some programs, you can set the system to purge any deleted records that have remained inactive for longer than a specified amount of time. Purkinje effect The human visual system is more sensitive to blue light in conditions of lower illumination and more sensitive to yellow light in conditions of higher illumination. purple wire An IBM color designation for wires that have been incorporated during testing and debugging to accommodate errors (purple wires may actually be yellow). See blue wire, red wire, yellow wire.

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push-pull circuit A circuit consisting of elements operating in a phase relationship rotated 180°. This makes it possible to cancel or filter certain elements and to amplify or magnify others. This circuit is used in oscillators, amplifiers, and transformers. pushbutton dial A capability through a set of buttons, usually on a phone or computer keypad, for sending signals to a transmission system. The button “dial” generates a tone at a specific frequency, which is then transmitted and interpreted as a numbered location for the destination receiver. A few units have both rotary and pushbutton capabilities. See touchtone. Contrast with rotary dial. put In file transfers over a network, e.g., through File Transfer Protocol (FTP), a line command or graphics “put” button for uploading a file. In other words, “putting” a file involves sending the file from the local system to a remote system. The analogous command for downloading/receiving a file is get. putup A packaged wire or cable product, which may be wound on a spool, over a rack, or coiled in a box. PVC 1. See permanent virtual connection. 2. See polyvinyl chloride. PVCC Permanent Virtual Channel Connection. PVN See private virtual network. pW abbrev. picowatt. See pico-, watt. PWB printed wire/wiring board. PWM See pulse width modulator. PWR An abbreviation for power sometimes seen in technical manuals or on components. PWT 1. parking without ticket. A video surveillance system that enables parking management through computer software with video display capabilities that replaces traditional paper tickets. 2. See Personal Wireless Telecommunications. 3. project work team. px64 A videophone/videoconferencing standard within the ITU-T H.320 videoconferencing recommendations family. Px64, officially known as ITU-T H.261 is an interoperability standard for video data streams originally developed in the mid-1980s to support transmission of analog video services over Integrated Services Digital Network (ISDN) services. The name is derived from data rates based upon p x 64 kbps with p = 1,2,...,30 (depending upon the available number of ISDN channels). In 1990, the Video Codec for Audiovisual Services was completed and approved for Europe, with a modified version adapted in North America. The encoding is hierarchically grouped, with video streams comprising Groups of Blocks (GoBs) of images or frames. Discrete cosine transform (DCT) algorithms are used to subdivide image parts into smaller building blocks. The standards were originally specified for fixeddata-rate ISDN circuits, but were found adaptable to packet-switched circuits (e.g., the Internet), as well. Thus, in 1996, a standards-track RFC was submitted by Turletti and Huitema of Bellcore for an RTP Payload Format for H.261 video streams. In 1997, Zhu submitted a standards-track RFC for an RTP Payload Format for H.263 to enable packetization of H.263 video streams. This greatly increases the

versatility of H.261, as packetization enables transmissions over distributed networks with standard User Datagram Protocol (UDP) datagrams. See RFC 2032,RFC 2190, RFC 2736. pylon 1. A tower or other tall supporting structure for stringing wire over a wide span, buildings, people, or other structures. The pylon often serves to provide both structural support and safety. 2. A broadcast transmissions tower, often a tall one, for increasing line-of-sight distance transmissions by “towering” over terrain and buildings that might otherwise obstruct or reflect the signals. pylon antenna A vertical standing antenna of slotted sheet-metal cylinders, sometimes combined in sections, one atop the other, to achieve greater height. The name comes from the cylindrical shape and orientation which resemble log pylons on a dock. pyrheliometer An instrument for measuring infrared radiation which borders the visible spectrum on one side and radio waves on the other. pyroelectricity Electromagnetic charge created through a change in temperature (usually heating). Pyroelectricity refers to the means of generating the charge, not the nature of the charge itself, which is the same as others. Crystals have valuable oscillating characteristics and are commonly used in timing mechanisms and radio electronics and some have interesting electrical activity when exposed to heat. pyromagnetic effect The combined effect of heat and magnetism in a material or circuit. pyrometer An electronic instrument for determining temperature in situations hotter than those typically measured by a traditional mercury thermometer. Temperature can be measured in a number of ways by electrical resistance, optical, or other radiant energy emissions. pyrone detector A type of radio wave crystal detector comprising iron pyrite and other conducting materials; rectification occurs between the materials. See detector.

C B

A

The sum of the squares of the sides (A, B) of a right angle triangle equals the square of the hypotenuse (C).

Pythagoras’ theorem, Pythagorean theorem A mathematical rule that states that, in a right-angled triangle, the sum of the squares of the sides is equal to the square of the hypotenuse (the longest side). This theorem is widely used in mathematics for calculating distances and other measures. It is named for the Pythagoreans, a philosophical group connected with Pythagoras.

Q q 1. symb. quantum value. 2. symb. electrical quantity in coulombs. See coulomb. Q 1. abbrev. quality. See Q factor. 2. abbrev. queue. See queue. 3. A merit indicator for a capacitor or inductor equal to the reactance divided by the resistance. Q address A storage location for data, from which the information can be accessed and retrieved. Q antenna A type of dipole antenna in which the feed line impedance is made to match the radiometer center impedance by the interposition of a vertical section, consisting of parallel bars between the two. Q bit In an X.25 network, the Q bit is a binary indicator located at the beginning of a data packet, immediately preceding the D bit. The Q bit signals the existence of user data or qualified data in the form of control information. Protocols in higher layers can set this bit to one (1) to indicate control packets, otherwise a value of zero (0) indicates data packets. See D bit, M bit. Q channel 1. In NTSC color television broadcasting, a frequency band in which green-magenta color information is transmitted. 2. In ISDN Basic Rate Interface (BRI) S/T interface implementations, an 800-bps maintenance channel. 3. In data transmissions, a channel associated with an I channel in modulated transmissions (e.g., phase-shift keying). See Q signal. Q demodulation Demodulation of an incoming broadcast signal in a color television receiver to combine the chrominance signal and the color-burst oscillator signal in order to recover the Q signal. Q factor (symb. – Q) quality factor. 1. In electronic circuits, a means of describing the desired characteristics of a system. The terms of the Q factor vary depending upon what is described (capacitance, inductance, etc.). Generally, a higher number is used to indicate a more efficiently operating component. 2. A measure of frequency selectivity, or the sharpness of resonance in a resonant vibratory system which has one degree of mechanical or electrical freedom. Q multiplier A circuit used to enhance the selectivity of a component by feeding the signal back through

the resonant network. This was used in early superheterodyne receivers, but various types of filters have, for the most part, superseded it. Q output The reference output of an electronic flipflop state, which may be one or zero. Q Series Recommendations A set of ITU-T recommendations providing guidelines for switching and signaling. These are available as publications from the ITU-T for purchase from the Net. Some of the related general categories and specific Q category recommendations are included in charts on the following pages to give a sense of the breadth and scope of the topics listed here. A full list of general categories is listed in Appendix C and specific series topics are listed under individual entries in this dictionary. See also I, V, and X Series Recommendations. Q signal 1. In various data transmission schemes, it is common to split a signal and to alter the characteristics of one or both of the two data streams so that they can be transmitted together without excessive interference or crosstalk. A Q signal or quadrature-phase signal is one of two common streams; the other is the in-phase signal or I signal, into which data are commonly split in various modulation systems. See quadrature amplitude modulation. See I signal. 2. A telegraph code shorthand signal consisting of two letters prefaced by a “Q” that is still wellknown to amateur radio operators. For example, QST is a general call preceding a message addressed to all members and amateurs. As such, it is also the name of the journal of the American Relay Radio League (ARRL). See QBF. Q spoiling A technique used with lasers in which a more powerful burst or pulse is attained by inhibiting the action of the laser for a few moments, to allow an increase in the number of ions, and then Q switching to allow the extra burst of light to be emitted. Q-band A microwave frequency spectrum ranging from 36 to 46 GHz, between the Ka-band and the Vband. Frequencies in this range tend to be used for radar and small aperture satellite transmissions. See band allocations for a chart of designated frequencies.

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ITU-T Q Series Recommendations General Q.9

Vocabulary of switching and signaling terms Q.1300 Telecommunication applications for switches and computers (TASC) – general overview Q.1302 Telecommunication applications for switches and computers (TASC) – TASC functional services Q.1303 Telecommunication applications for switches and computers (TASC) – TASC management: architecture, methodology and requirements Q.1290 Glossary of terms used in the definition of intelligent networks Q.1201/I.312 Principles of intelligent network architecture Q.1202/I.328 Intelligent Network – service plane architecture Q.1203/I.329 Intelligent Network – global functional plane architecture Automatic and semiautomatic switching Q.4 Q.5 Q.6

Automatic switching functions for use in national networks Advantages of semiautomatic service in the international telephone service Advantages of international automatic working

Signaling systems Q.7

Signaling systems to be used for international automatic and semiautomatic telephone working Q.8 Signaling systems to be used for international manual and automatic working on analogue leased circuits Q.48 Demand assignment signaling systems Q.50 Signaling between circuit multiplication equipment (CME) and international switching centers (ISC) Q.55 Signaling between signal processing network equipment and international switching centers Q.698 Interworking of signaling system No. 7 ISUP, TUP, and signaling system No. 6 using arrow diagrams Q.700 Introduction to CCITT Signaling System No. 7 Q.701 Functional description of the message transfer part (MTP) of Signaling System No. 7

Q.721 Signaling System No. 7 functional description of the Signaling System No. 7 Telephone User Part (TUP) In-band and out-band Q.20 Q.21 Q.22 Q.25

Q.25

Comparative advantages of “in-band” and “out-band” systems Systems recommended for out-band signaling Frequencies to be used for in-band signaling Splitting arrangements and signal recognition times in “in-band” signaling systems Splitting arrangements and signal recognition times in “in-band” signaling systems

Phone features and signals Q.23

Technical features of push-button telephone sets Q.24 Multifrequency push-button signal reception Q.27 Transmission of the answer signal Q.28 Determination of the moment of the called subscriber’s answer in the automatic service Q.35 Technical characteristics of tones for the telephone service Q.109 Transmission of the answer signal in international exchanges Network access Q.26

Direct access to the international network from the national network

Quality of transmissions; interference and noise Q.29 Q.30 Q.31 Q.32 Q.33 Q.44

Causes of noise and ways of reducing noise in telephone exchanges Improving the reliability of contacts in speech circuits Noise in a national 4-wire automatic exchange Reduction of the risk of instability by switching means Protection against effects of faulty transmission on groups of circuits Attenuation distortion

ISDN and B-ISDN Q.71 Q.80 Q.81 Q.82 Q.83 Q.84 Q.85 Q.86 Q.87 Q.761 Q.762

Q.763 Q.764 Q.767

Q.768

Q.850

Q.860 Q.920 Q.921 Q.922 Q.923

Q.930 Q.931

Q.932 Q.933 Q.939

ISDN circuit mode switched bearer services Introduction to Stage 2 service descriptions for supplementary services Number identification Call offering Call completion Multiparty Community of interest Charging Additional information transfer Functional description of the ISDN user part of Signaling System No. 7 General function of messages and signals of the ISDN user part of Signaling System No. 7 Formats and codes of the ISDN user part of Signaling System No. 7 Signaling System No. 7 ISDN user part signaling procedures Application of the ISDN user part of CCITT Signaling System No. 7 for international ISDN interconnections Signaling interface between an international switching centre (ISC) and an ISDN satellite subnetwork Usage of cause and location in the digital subscriber signaling system no 1 and the Signaling System No. 7 ISDN user part ISDN and B-ISDN Generic Addressing and Transport (GAT) Protocol DSS1 – ISDN user-network interface data link layer, general aspects ISDN user-network interface, data link layer specification ISDN data link layer specification for frame mode bearer services Specification of a synchronization and coordination function for the provision of the OSI connection-mode network service in an ISDN environment DSS1 – ISDN user-network interface layer 3, general aspects DSS1 – ISDN user-network interface layer 3 specification for basic call control DSS1 – generic procedures for the control of ISDN supplementary services ISDN DSS1 – signaling specification for frame mode basic call control Typical DSS1 service indicator codings for ISDN telecommunications services

Q.940 ISDN user-network interface protocol for management, general aspects Q.950 ISDN supplementary services protocols, structure, and general principles Q.951 Number identification Q.952 Stage 3 description for call offering supplementary services using DSS 1 – diversion supplementary services Q.953 Call completion Q.954 Multiplarty Q.955 Community of interest Q.956 Charging Q.967 Additional information transfer Q.1901 Bearer-Independent Call Control Protocol Q.1950 Bearer-Independent Call Control Protocol Q.1970 Bearer-Independent Call Control IP Bearer Control Protocol Q.1990 Bearer-Independent Call Control Tunneling Protocol Q.2010 Broadband integrated services digital network overview – signaling Capability Set 1 (CS-1) Q.2100 B-ISDN signaling ATM adaptation layer (SAAL) overview description Q.2110 B-ISDN ATM adaptation layer – service specified connection oriented protocol (SSCOP) Q.2111 Service-Specific Connection-Oriented Protocol in a multilink and connectionless environment (SSCOPMCE) Q.2119 B-ISDN ATM adaptation layer – convergence function for SSCOP above the frame relay core service Q.2120 B-ISDN meta-signaling protocol Q.2130 B-ISDN signaling ATM adaptation layer – service-specific coordination function for support of signaling at the user network interface (SSFC At UNI) Q.2140 B-ISDN ATM adaptation layer – service specific coordination function for signaling at the network node interface (SSCF at NNI) Q.2144 B-ISDN Signaling ATM adaptation layer (SAAL) – layer management for the SAAL at the network node interface (NNI) Q.2150 AAL2 signaling transport converter Q.2210 Message transfer part level 3 functions and messages using the services of ITU-T Recommendation Q.2140

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ITU-T Q Series Recommendations, cont. ISDN and B-ISDN, cont. Q.2610 B-ISDN usage of cause and location in B-ISDN user part and DSS-2 Q.2650 B-ISDN – internetworking between Signaling System No. 7 B-ISDN User Part (B-ISUP) and digital subscriber Signaling System No. 2 (DSS-2) Q.2660 B-ISDN – internetworking between signaling System No. 7 B-ISDN User Part (B-ISUP) and N-ISDN User Part (N-ISUP) Q.2723 Extensions to SS7 B-ISDN User Part (B-ISUP) Q.2725 B-ISDN User Part CS-2.1 See Q.2761 through Q.2764 Q.2726 B-ISDN User Part CS-2.1 See Q.2761 through Q.2764 Q.2727 B-ISDN User Part (B-ISUP) support of Frame Relay Q.2730 B-ISDN – SS7 B-ISDN User Part (BISUP) supplementary services Q.2735 Stage 3 description of Community of Interest supplementary services for BISDN using SS7 Q.2761 B-ISDN – functional description of the B-ISDN User Part (B-ISUP) of SS7 Q.2762 B-ISDN – general functions of messages and signals of the B-ISUP of SS7 Q.2763 B-ISDN – SS7 B-ISDN User Part (BISUP) – Formats and codes Q.2764 B-ISDN – SS7 B-ISDN User Part (BISUP) – Basic call procedures Q.2765 B-ISDN SS7 B-ISUP – Application Transport Mechanism (APM) Q.2931 B-ISDN – Digital Subscriber Signaling System No. 2 (DSS-2) – User Network Interface (UNI) Layer 3 specification for basic call/connection control Q.2934 B-ISDN DSS-2 switched virtual path capability Q.2941 B-ISDN DSS-2 extensions Q.2951 B-ISDN – Stage 3 description for number identification supplementary services using B-ISDN DSS-2 – basic call Q.2955 B-ISDN DSS-2 – stage 3 description for community of interest supplementary services – basic call Q.2957 B-ISDN DSS-2 – stage 3 description for additional information transfer supplementary services – basic call Q.2959 B-ISDN DSS-2 – call priority Q.2961 B-ISDN DSS-2 – support of additional parameters

Q.2962 B-ISDN DSS-2 – connection characteristics negotiation during call/connection establishment phase Q.2963 B-ISDN DSS-2 – extensions for ATM Q.2964 B-ISDN DSS-2 – basic look-ahead and other clauses Q.2965 B-ISDN DSS-2 – Quality of Service (QoS) issues Q.2971 B-ISDN – digital subscriber DSS-2 – user network interface Layer 3 specification for point-to-multipoint call/connection control Q.2981 B-ISDN and B-PISN – call control protocol Q.2982 B-ISDN DSS-2 – Q.2931-based separated call control protocol Q.2983 B-ISDN DSS-2 – Q.2931-based bearer control protocol Q.2984 B-ISDN and B-PISN – prenegotiation for multiconnection Q.2991 Abstract test suite for the network integration testing for B-ISDN and B-ISDN/N-ISDN Modeling, Intelligent Networks Q.76 Q.1200 Q.1201 Q.1202 Q.1203 Q.1204 Q.1205 Q.1208 Q.1210 Q.1211 Q.1213 Q.1214 Q.1215 Q.1218 Q.1219 Q.1220

UPT functional modeling and information flow Intelligent Networks (INs) recommendation structure Principles of Intelligent Networks architecture Intelligent Networks – service plane architecture Intelligent Networks – global functional plane architecture Intelligent Networks – distributed functional plan architecture Intelligent Networks – physical plane architecture General aspects of the Intelligent Networks application protocol Q.12xx series structure for Intelligent Networks Introduction to Intelligent Networks Capability Set 1 (CS-1) Global functional plane for Intelligent Networks CS-1 Distributed functional plane for Intelligent Networks CS-1 Physical plane for Intelligent Networks CS-1 Interface recommendation for Intelligent Networks CS-1 Intelligent Networks user guide for CS-1 Q.122x series Intelligent Networks Capability Set 2 (CS-2) recommendation structure

Q.1221 Instruction to Intelligent Networks CS-2 Q.1222 Service plane for Intelligent Networks CS-2 Q.1223 Global functional plane for Intelligent Networks CS-2 Q.1224 Distributed functional plane for Intelligent Networks CS-2 Q.1225 Physical plane for Intelligent Networks CS-2 Q.1228 Interface recommendation for Intelligent Networks CS-2 Q.1229 Intelligent Networks user’s guide for CS-2 Q.1231 Introduction to Intelligent Networks Capability Set 3 (CS-3) Q.1236 Intelligent Networks CS-3 Management Information Model requirements and methodology Q.1237 Extensions to Intelligent Network CS-3 in support of B-ISDN Q.1238 Interface recommendation for Intelligent Network CS-3 Q.1241 Introduction to Intelligent Networks Capability Set 4 (CS-4) Q.1244 Distributed functional plane for Intelligent Networks CS-4 Q.1248 Interface recommendation for Intelligent Network CS-3 Q.1290 Glossary of terms for Intelligent Networks (included in Q.9) Q.1300 Telecom applications for switches and computers (TASC) – general overview Q.1301 TASC – architecture Q.1302 TASC – functional services Q.1303 TASC – management, architecture, methodology, and requirements Q.1400 Architecture framework for the development of signaling and organization, administration, and maintenance protocols using OSI concepts Q.1521 Requirements on underlying networks and signaling protocols to support UPT Q.1531 UPT security requirements for Service Set 1 (SS-1) Q.1541 UPT Stage 2 for SS-1 on SC-1-1995: procedures for UPT functional modeling and information flows Q.1542 UPT Stage 2 for SS-1 on CS-2 – procedures for universal personal telecommunication functional modeling and information flows Q.1551 Application of Intelligent Network application protocols (INAP) CS-1 for UPT SS-1 Q.1600 Signaling System No. 7 interaction between ISIUP and INAP Q.1601 Signaling System No. 7 interaction be-

tween N-ISDN and INAP CS-2 Q.1701 Framework for IMT-2000 networks Q.1711 Functional model for IMT-2000 networks Q.1721 Information flows for IMT-2000 CS-1 Q.1731 Radio technology independent requirements for IMT-2000 Layer 2 radio interface Q.1751 Internetwork signaling requirements for IMT-2000 CS-1 Wireless communications Q.14 Q.1000 Q.1001 Q.1002 Q.1003 Q.1004 Q.1005 Q.1032 Q.1051 Q.1100

Q.1101

Q.1111

Q.1112

Q.1151

Q.1152

Q.1237

Means to control the number of satellite links in an international telephone connection Structure of the Q.1000 series recommendations for public land mobile networks General aspects of public land mobile networks Network functions for public land mobile networks Location registration procedures for public land mobile networks Location register restoration procedures for public land mobile networks Handover procedures for public land mobile networks Signaling requirements relating to routing of calls to mobile subscribers Mobile application part for public land mobile networks Interworking with Standard A INMARSAT system – structure of the Recommendations on the INMARSAT mobile satellite systems General requirements for the interworking of the terrestrial telephone network and INMARSAT Standard A system Interfaces between the INMARSAT standard B system and the international public switched telephone network/ ISDN Procedures for interworking between INMARSAT standard-B system and the international public switched telephone network/ISDN Interfaces for interworking between the INMARSAT aeronautical mobile-satellite system and the international public switched telephone network/ISDN Procedures for interworking between INMARSAT aeronautical mobile satellite system and the international public switched telephone network/ISDN Extensions to Intelligent Network CS-3 in support of B-ISDN

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Q.SIG A global common channel signaling protocol (CCS), based upon the ISDN signaling protocol, used in the digital transmission of voice over digital networks such as ATM. In addition to the features in the ISDN signaling protocol, Q.SIG includes private branch exchange (PBX) features so a network of PBXs can interact as a distributed system. CCS systems are more prevalent in Europe than in the United States. See voice over ATM. QA 1. quality assurance. 2. queued arbitrated. In DQDB, an information field segment used to transfer slots when they arrive through a nonisochronous transfer. QAM See quadrature amplitude modulation. QBE See query by example. QBF, fox message QBF = “quick brown fox.” The Q signal code to send a test sentence that includes all the letters of the English alphabet. A QBF message is commonly used to verify whether all letters available to a device or contained within a coding system are present and/or working correctly. It is familiar to most as “THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG” (which is then repeated in lowercase, if needed). The idea is to convey the entire alphabet in the shortest sentence that is comfortably memorable as possible. In wireline devices, it is more often called a “fox message” since Q signals are associated more specifically with radio frequency communications. The phrase “fox message” is used more generically to test alphabetic communication signals and the physical integrity of typewriter or computer keyboard keys. See Q signal, Z code. QC quality control. QC laser See quantum cascade laser. QCELP See Qualcomm Code Excited Linear Predictive Coding. QCIF See Quarter Common Intermediate Format. QCT Qualcomm CDMA Technologies. See Qualcomm Code Excited Linear Predictive Coding QD See queuing delay. QD-DOS, QDOS A historic microcomputer operating system (Quick and Dirty Operating System) developed by Tim Paterson, which was derived from a mid-1970s manual describing Gary Kildall’s CP/ M, and extremely similar in syntax and functionality. At that time, IBM was looking for an operating system for its line of microcomputers. IBM contacted Microsoft about contracting their (computer language) products, thinking they had also purchased the rights to CP/M. When they found that Microsoft didn’t have an operating system, they went to visit Digital Research (originally Inter-Galactic Research), but the DR representative was reluctant to sign IBM’s nondisclosure agreement on DR’s behalf, especially when the attorney didn’t like the terms of the contract. IBM went back to Microsoft and DR thought it would have a further opportunity to talk terms with IBM, especially since Microsoft didn’t have an operating system that could meet IBM’s needs at the time, as they had been concentrating their efforts on

developing computer languages. Microsoft, however, promised one to IBM in a very short time period, and delivered on the contract by purchasing the code for QDOS from Seattle Computing, the company for which Paterson was working. They provided it to IBM who released it as PC-DOS. Microsoft subsequently purchased the distribution rights for QDOS for $50,000 and later released a slightly altered version of PC-DOS as MS-DOS (Microsoft Disk Operating System). Microsoft managed to stipulate contractually that they could retain the rights to sell the product they had developed for IBM, in competition with IBM. Thus, QDOS, derived from CP/M became IBM’s product, rather than CP/M itself, and evolved into MS-DOS, and eventually Windows. See CP/M, Microsoft Corporation, MS-DOS, Digital Research. QDU See quantizing distortion units. QFA See Quick File Access. QFC See Quantum Flow Control. QFM See quadrature frequency modulation. QIC quarter inch cartridge. See Quarter Inch Cartridge Drive Standards. QICC 1. See Quad Integrated Communications Controller. 2. See Quad International Communications Corporation. QIP A commercial Internet Protocol (IP) address management software product from Quadritek (now Lucent IPGSP) that facilitates the central management of network databases. In March 2000, Lucent announced that QIP had been ranked as the market share leader for standalone Internet Protocol (IP) address management products. The product is used by prominent companies such as MCI Worldcom’s UUNET, Discover Financial Services, Ford Motor Company, and others. See Quadritek. QJDP QIP/Windows 2000 Joint Developer Program. Lucent Technologies’ initiative launched in December 1999 to foster development of design interfaces and requirements between QIP 5.0 IP address management software and Windows 2000. See QIP, Quadritek. QL See query language. QLLC See Qualified Logical Link Control. QM quality module. QMS Queue Management System. See queue management. QoR See Query on Release. QoS See Quality of Service. QPL Qualcomm PureVoice Library. See Qualcomm Code Excited Linear Predictive Coding. QPSK 1. See quadrature phase shift keying. 2. See quaternary phase shift keying. QR queuing requirements. See queuing theory. QRP A designation for low-power amateur frequency radio transmissions. Low-power transmitters and receivers are an interesting subgroup of hobbyist radio, when used with respect for the privacy of individuals and within regulatory guidelines. Regulations for short distance, low-power transmissions are more lenient than for other types of broadcasts.

QRP transmitters can be used for short-distance broadcasting, home security systems, door intercoms, climbing communicators, baby and child monitors, and other short-range projects. QRP ARCI The QRP Amateur Radio Club International is a nonprofit organization dedicated to amateur design, construction, and use of QRP (low power) transmitters. See Amateur Radio Relay League, QRP. http://www.qrparci.org/ QSAM see quadrature sideband amplitude modulation. QSDG See Quality of Service Development Group. QTAM See Queued Telecommunications Access Method. QTC QuickTime Conference. See QuickTime. QTSS QuickTime Streaming Server. See QuickTime. QTVR QuickTime Virtual Reality. See QuickTime. QuAD Quorum Associate Distributor. See Quorum International. quad- Prefix for four. quad antenna A type of array antenna similar in principle to a Yagi-Uda antenna, except that it uses full-wavelength loops in the place of half-wavelength straight elements, thus providing greater gain over a similar Yagi-Uda antenna. As with many antennas, the feed is commonly 75-ohm coaxial cable. A twoelement quad antenna is called a quagi. Quad antennas come in a variety of configurations with the elements mounted on a boom or radiating out like the support threads of a spider web. In one common configuration, the prominent features include simple straight-pole elements mounted in a horizontal plane at right angles to one another with a diamond-shaped configuration on one pole mounted in the vertical plane. There are variations on quad antennas including cubical quads (which can resemble an open umbrella with the fabric missing) and hybrid quads. Mini-quads – compact quad antennas – have some advantages that are appealing to amateur radio enthusiasts including reasonable cost, low wind loading, and small turning radius. Quad/mini-quad antennas in the 15±5 m frequencies are readily available. Quad Integrated Communications Controller QICC (pron. qwik). A single-chip integrated CPU32+ microprocessor from Motorola designed for embedded telecommunications and internetworking applications. The MC68360 QICC is a next-generation MC68302 with four serial communications controllers, two serial management controllers, and one serial peripheral interface that operates at 4.5 MIPS at 24 MHz. The QICC is useful for controller applications. Quad International Communications Corporation QICC. A California-based international supplier of telecommunications products including Frame Relay. quad wiring Wiring bundles consisting of four individually sheathed, untwisted wires brought

together (aggregated) within a single cover. Quad wiring is often used for the internal wiring of twoline analog phones, with the lines inside generally color-coded green and red (tip and ring) for the first line, and black and yellow for the second line. This type of wiring is not recommended for data transmission installations. Quad fiber cables consist of four individual fiber cables bundled together within a single cover. quadrature A state in which cyclic events are 90 degrees out of phase. In signal transmission quadrature, phasing is a common technique used to distinguish information in signals. It is also used to vary a signal so crosstalk between two closely associated transmissions is reduced. quadrature amplitude modulation QAM. A modulation technique employing variations in signal amplitude. This modulation scheme is used in asymmetric digital subscriber line services, for example. It is a two-dimensional coding scheme that can be transmitted in a narrower spectrum, a combination of amplitude and phase-shift modulation. The QAM spectrum derives from the spectrum of the baseband signals as they apply to the quadrature channels. QAM is similar to nonreturn-to-zero baseband transmission and multiphase phase shift keying (PSK), except that QAM does not have a constant envelope as in PSK. QAM requires lower sampling frequencies and the spectral width can be optimized by keeping the baud rate lower, thus reducing the potential for crosstalk. See modulation. quadrature/quadriphase phase-shift keying QPSK. A type of phase shift keying modulation scheme in which four signals are used, each shifted by 90°, with each phase representing two data bits per symbol, in order to carry twice as much information as binary phase shift keying (BPSK), which can be seen as two independent binary phase shift key (BPSK) systems. QPSK can be used to carry bit timing and can be filtered using raised cosine filters for out-of-band suppression. Even more sophisticated systems exist that employ differential encoding of symbol phases. Linear power amplifiers are used with the various QPSK schemes. Staggered quadrature/quadriphase phase shift keying (SQPSK) is similar to QPSK except that the data channels are offset to shift the carrier 90°. The staggering facilitates recovery of I and Q channels. See frequency modulation, frequency shift keying, on/ off keying, modulation, quadrature sideband amplitude modulation. quadrature sideband amplitude modulation QSAM. A modulation encoding technique in which different signal amplitude states are used to represent data. Quadritek Systems Inc. A network products firm founded in 1993 to provide server-related solutions. QIP is Quadritek’s (IP) network address management software product. In March 1998, IBM and Quadritek announced a

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collaboration in which IBM would make changes to its Dynamic Host Configuration Protocol (DHCP) and Domain Name Server (DNS) to enable Quadritek and other vendors to use an open standard API to manage servers. Thus, Quadritek’s QIP product could be used to manage multiple, distributed IBM DHCP/DNS servers. Quadritek is now Lucent Technologies IPSPG. quadruplex circuit A circuit which is carrying two bidirectional transmissions simultaneously to make a total of four. Qualcomm Code Excited Linear Predictive Coding QCELP. A proprietary algorithm from Qual comm CDMA Technologies (QCT) that supports digital voice coding/decoding through code division multiple access (CDMA) methods. QCELP compression supports fixed and variable encoding. In the mid-1990s, Qualcomm released the PureVoice vocoder (voice coder), based on 13-kilobit QCELP for use in cellular and Personal Communications System (PCS) products. The design goal of the PureVoice vocoder was to provide voice quality approaching that of wireline while still keeping the bit rate as low as possible to work within the capacity limitations of mobile communications devices. Since it is a software solution, it can be integrated into a wide variety of desktop and mobile devices. In 1998, Qualcomm announced an agreement with Apple Computer to integrate the PureVoice QCELPbased audio codec technology into Apple’s popular QuickTime multimedia software. The PureVoice technology is popular because of its relatively high quality and small file size, which is significantly smaller than audio files stored in .wav format, for example. PureVoice was also adapted for use in email in the late 1990s, so users could send actual voice messages through computer networks such as the Internet. The excellent compression ratios inherent in the QCELP technology made this a practical application and enabled greetings to be communicated without traditional long-distance telephone charges. The PureVoice Player/Recorder and the PureVoice Converter are available online as licensed, freely distributable software from Qualcomm Incorporated. Qualified Logical Link Control QLLC. A data link control protocol from IBM which works with the IBM SNA systems to allow them to operate over X.25 packet switched data networks. quality 1. Meeting subjective and/or objective standards of excellence in operation, manufacture, aesthetics, or a combination of these. 2. In manufacturing, quality is more narrowly defined as conformance to high objective standards of appropriateness, functionality, and longevity within the context of related products. 3. In service industries, quality is generally determined by adherence to operating and ethical standards of the industry and degree of customer satisfaction. See quality assurance. quality assurance Systematic actions which seek to assure satisfactory levels of manufacture, service, functionality, and longevity. quality factor See Q factor.

quality of service QoS. This has a general meaning across many industries and somewhat more specific meanings in the context of telecommunications networks. In general, quality of service is a descriptor and reference of performance for the provision of services on a network. It includes parameters and values such as data rates, acceptable delays, losses, errors, etc. As part of the QoS requirements for an ATM network, four class of service (CoS) traffic types have been specified: CoS

Characteristics

Class A

Connection-oriented, constant bit rate (CBR), with a strong timing relationship between source and destination. Constant bit rate video and PCM encoded voice are included in this category.

Class B

Connection-oriented; bit rate may vary, with a strong timing relationship between source and destination.

Class C

Connection-oriented; bit rate varies, no timing relationship between source and destination. TCP/IP and X.25 are included in this category.

Class D

Connectionless; bit rate varies, no timing relationship between source and destination. Connectionless packet data are included in this category.

There are many types of data, and how they are perceived in part determines how their quality is evaluated. Consequently, QoS requirements vary with the type of data. See cell rate, class of service. Quality of Service Development Group QSDG. A Telecommunication Standardization Sector group of the International Telecommunications Union established in 1984 to help develop practical implementations of international telecommunication quality of service (QoS) standards. It is funded primarily by administrations and ROAs. quantization A process in which a continuous range of values, such as an incoming analog signal, is subdivided into ranges, with a discrete value assigned to each subset. This is a means of converting analog data to digital data, and is used in musical sound sampling, modem communications, voice over data networks, radio wave modulation, and many other aspects of telecommunications. Generally the frequency of the sampling influences the quality and fidelity of the outgoing quantized signal, within certain limits set by the capabilities of the equipment and the characteristics of the human perceptual system. Higher sampling rates tend to pro-

duce closer approximations to the original signal, but also require greater transmission speeds and bandwidth. Quantization is used in a number of modulation schemes, including pulse code modulation (PCM), which is commonly used in voice communications. See modulation, patches, pulse code modulation, sampling, quantization error. quantization, vector A vector version of scalar quantization, designed to reduce the volume of data files or the bit rates of data transfers. Vector quantization has practical applications for image and speech coding. quantization error A number of aspects can introduce error into a quantized signal, including the amount of noise and interference accompanying the signal, the signal range or amplitude as it relates to the capabilities of the quantizing mechanism, the strength and complexity of the signal being quantized, and the mathematics used to carry out the conversion. Quantization error is sometimes assessed after a digital signal is reconverted to analog format, and the end signal is compared to the original, with the differences assessed subjectively (as in music systems) or evaluated with various measuring instruments. quantize To convert a continuous range of values into discrete, nonoverlapping values or steps. This is an important means to convert analog to digital values. quantizing distortion units QDU. A measure of the degree of degradation in a voice channel that occurs as a result of format and signal conversions (e.g., analog to digital to analog). This is described in the ITU-T G Series Recommendation G.113 (transmission impairments). quantometer An instrument for the measurement of magnetic flux. quantum (plural – quanta, symb. – q) A name for a relatively recently discovered and investigated phenomenon related to the movement of electrons. Quantum theory was first stated by physicist Max Planck in 1900. A quantum is a discrete quantity of electromagnetic energy, the smallest possible amount of energy at any given frequency v. Quantum phenomena are of great interest to physicists, and researchers are now investigating ways of enlisting quantum behaviors in the manufacture and use of various industrial products such as lasers and in operations associated with digital logic, with some surprising and provocative success. See quantum cascade laser. quantum cascade laser QC laser. A new type of “NanoLaser” developed by Frederico Capasso and Jerome Faist at Bell Laboratories in 1994. The QC laser is a continuously tunable, single-mode, distributed-feedback device. To understand how a QC laser works, imagine an electric current stimulating a number of electrons to cascade over a series of steppes (a terraced organization), squeezed through quantum wells in successive layers, dropping off energy in the form of photons

(light pulses) as they contact and travel through each steppe. At each steppe, the electrons perform a quantum jump between well-defined energy levels. The photons emitted as a result of their activity reflect back and forth in an amplification process that stimulates other quantum jumps and emissions and results in a high output. The QC laser has a number of advantages over diode lasers, including higher optical power and finer linewidth. QC lasers can be used in a wide variety of applications, including medical diagnostics, radar heterodyne detectors, and remote sensing applications – particularly environmental monitoring in toxic environments. The wavelength of the laser is determined by quantum confinement. Thus, it can be used selectively over a wide range of the infrared spectrum by varying the layer thicknesses and spacing of the different materials used in its manufacture. This differs from other technologies in that the output wavelength is not dependent upon the chemical composition of the semiconductors, but upon their thickness and positioning. These layers, created with a molecular beam epitaxy (MBE) materials-growth process, are sometimes only a few atoms thick. The QC laser also functions at higher temperatures than diode lasers, making it practical for room temperature use. See Capasso, Frederico; vertical-cavity surface-emitting laser. Quantum Corporation A prominent data storage device developer/distributor, founded in 1980. Quantum became well-known for computer hard drives in the late 1980s and the 1990s and, more recently, has introduced Super DLTtape technologies that provide fast transfer-rate, high-capacity storage on tape cartridges. See Super DLTtape. Quantum Flow Control QFC. In ATM networks, a congestion avoidance scheme proposed for use on available bit rate (ABR) connections. For example, in a network in which VCI tunneling is implemented, the ATM device will send only after receiving explicit credit from a receiving ATM device at the other end of the connection. If tunneling is not used, buffer allocation and a credit manager must be included. If the buffer allocation is exceeded, noncomplying cells will be discarded. quantum mechanics The study of atomic structure and behaviors using various measuring instruments and techniques. See Heisenberg uncertainty principle, quantum. quantum noise When using a detector to investigate quantum characteristics in electromagnetic phenomena, there may be noise from random variations or fluctuations in the average rate of incidence of quantum interactions with the detector. These may be expressed in terms of photons. quantum well QW. A quantum phenomenon associated with a structure fabricated from ultrathin alternating layers of wide bandgap (barrier) and narrow bandgap (well) materials. When an electron is caught in a well formed between the barriers, the probability of escaping the well is limited and the

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electron’s energy level is affected. The quantization effects resulting from these events are related to the height and width of the fabricated barrier and can be derived through quantum mechanical calculations. Quantum well exhibiting structures can be constructed using crystal growth techniques. Quantum well components have unique properties that can be exploited for a variety of optical technologies related to telecommunications: • Quantum well physics can be used to create modulators through the application of an electrical field perpendicular to the surface of the quantum well or alternately to its sides. Thus, the optical absorption of the QW is changed sufficiently to make it useful for signaling. This phenomenon can be exploited for semiconductor design to make small optical modulators with two-dimensional optical arrays. • A quantum well infrared photodetector (QWIP) is a multiple quantum well device based upon layered high-bandgap semiconductor fabrication. Bandgap discontinuity associated with the layers of differing materials creates quantized subbands in the potential wells. The phenomena associated with the layers is a photoexcitation of electrons between ground and first excited-state subbands. The carriers resulting from the photoexcitation are then able to escape from the potential quantum wells to generate a photocurrent. • In the U.S. Naval Research Lab, quantum well physics has been used to develop a number of types of semiconductor lasers emitting mid-infrared light. Using “wavefunction engineering,” engineers have designed complex, layered quantum well structures. This has a number of possible applications, including laser radar (ladar). • Researchers at Imperial College demonstrated a new quantum well solar cell (QWSC) that may be more efficient than previous solar energy sources. • In 1997, scientists described an uncooled strained quantum well laser that could be used in SONET/SDH networks, especially short- and medium-haul transmissions. See electroabsorption, quantum cascade laser, selfelectro-optic effect device. Quarter Common Intermediate Format QCIF, Quarter CIF. A standard for the transmission of video frames in the ITU-T H.261 standard. QCIF consists of 144 lines of luminance and 176 pixels per line (144 x 176 CIF format is optionally supported by H.261). This relatively low resolution creates an image that has a soft-focus, indefinite appearance, but has the advantage of using fewer system resources and less bandwidth. In fact, the standard was developed with the needs of circuit-switched networks in mind. For small windows, simple images, and small display devices, it has practical applications, and it is widely favored for videoconferencing, especially on ISDN networks. H.261 is usually implemented in conjunction

with other related standards. See Common Intermediate Format. Quarter Inch Cartridge Drive Standards QIC. An international association, established in 1987, to promote the acceptance and use of quarter-inch readable/writable data cartridge drives and media. These types of storage media are commonly used for computer backup, secondary storage, and temporary storage for files that need to be transported. More than 100 QIC standards have been developed since 1988. The list on the following pages describes a few of the standards of interest, to provide a sampling of their scope and contents. QIC-40, QIC-80, QIC-3101, and QIC-3020 have been particularly prevalent in the tape cartridge field, although they are now being superseded by higher capacity formats. A complete list and fuller description of each standard are available on the QIC Web site. http://www2.qic.org/ quarter wave The distance, or elapsed time, in a conducting line or through a conducting space, which is 90° to a wave disturbance. This information in used in the design of antennas and in the quadrature transmission of signals, particularly in modulation schemes. See quadrature. quartz A silicon dioxide mineral found or synthesized in crystal form and in crystalline masses, which is widely used in scientific research and telecommunications due to its oscillating qualities. Quartz is transparent, harder than glass, and varies in its oscillating frequencies depending upon its size and shape. Quartz crystal watches are extremely accurate, and quartz arc lamps are used for sterilization, due to the way ultraviolet light passes through the crystal. See piezoelectricity. Quartz A 2D graphics engine from Apple Computer, based upon the standardized Portable Document Format (PDF). Quartz is incorporated into Mac OS X. quartz crystal A quartz crystal is a piece of quartz cut to a precise size for a specific purpose. Quartz has remarkable constancy in its vibratory qualities , making it suitable for extremely precise time devices. These vibratory qualities can be controlled by manipulating the shape and size of the crystal. Early radio sets were called “crystal detectors” as they used crystals (galena and carborundum were popular) to detect (rectify) and channel a radio wave. Quartz is commonly used in oscillators and filters. Quartz crystals are used to provide timing in watches and to stabilize broadcast waves. See quartz, quartz crystal filter. quartz crystal filter The properties of quartz crystals make them useful for a variety of applications which require highly selective electrical circuitry, and hence they are used in the creation of various types of filters. Synthetic quartz crystals, developed in the 1950s, furthered the manufacture of quartz filters for use as electronic components. There were, in fact, few other materials that offered the advantages of natural or synthetic quartz until the development of lithium-tantalate crystals in the Bell Laboratories. See lithium-tantalate, quartz, quartz crystal.

quaternary phase-shift keying QPSK. A modulation technique which is used to encode digital information to be transmitted over wire or fiber networks. It is a subset of phase shift keying (PSK), and is essentially a four-level version of phase modulation (PM). QPSK divides the bit stream into two streams, and sends them alternately to in-phase and out-ofphase modulators, where they are subsequently demodulated at the receiving end. QUBE An Interactive TV information utility. Warner instituted the QUBE interactive educational TV network in the late 1970s. The first interactive television concert, broadcast live over the QUBE system in 1978, featured Todd Rundgren, pioneer multimedia recording artist. quench To bring to a sudden halt, to cool rapidly, to quickly extinguish a flame, spark, or gas emission. quench oscillator In some super-regenerator circuits, a type of ultrasonic oscillator which serves to quench, or rapidly reduce, the regeneration when it has almost increased to the point of oscillation. quenched spark gap Early wireless transmitters used spark gaps in their spark transmitters, with several types of gaps: open gaps, rotary gaps, and quenched gaps, each with different strengths and weaknesses. Quenched gaps employed a racklike series of metal plates separated by thin layers of mica, resulting in a very small spark that is quickly quenched and does not tend to overheat as do open gaps. Due to improvements in technology and the need for regular cleaning to keep quenched gap transmitters working optimally, they were eventually superseded by continuous wave (CW) transmitters. query 1. Request for data, in which the content of the data is the desired result. Common in database applications. 2. Request for data which provides information about the state (operating parameters, mode, security, etc.) or functioning (availability, readiness, status, responsiveness, etc.) of a system. Usually at a low operating level and generally transparent to the user. query by example QBE. An idea introduced in the 1970s whereby a user interacts with a front end to a database by supplying examples of the type of information that the user wants to retrieve. Sometimes this is more practical than querying by keywords or algorithms. A number of popular database programs provide this capability. query language A programming language intended to facilitate search and retrieval of information, usually from a database. Query languages are frequently in the form of interpreted scripting languages or graphical report generators, with commands that are similar to common English words, to make them easier to program by those without programming backgrounds. Query on Release QoR. A number portability mechanism suggested by Pacific Bell to trigger a database query, depending upon circumstances related to a subscriber’s current carrier. In QoR, a telephone call setup signal is routed to the end office switch to which the dialed phone number was

originally assigned (e.g., the NPA-NXX of the dialed number). If the dialed number has been transferred to another carrier’s switch, the database is queried for routing information and the call completed to the new switch. The system is also called Look Ahead. In 1997, the Federal Communications Commission affirmed its conclusion that this (interim) solution was not acceptable over the long term because it violated a statutory requirement for consumers to be able to retain numbers without impairment of the quality, reliability, or convenience when switching from one carrier to another. The Commission felt that degradation in service in terms of post-dial delays could compromise QoR forwarding and supported Location Routing Number (LRN) as statutorily acceptable. See Release to Pivot. queue A stream of items or tasks waiting to be processed or executed, such as calls to an operating system, a network, or a phone system. Queues are used to maximize the use of existing resources, especially on shared systems. It’s expensive to put a printer on every computer in a network and, since printing doesn’t happen as often as data input/output, it’s not efficient either. By allocating one printer to every few workstations, user print requests can be handled efficiently by the network, with simultaneous requests administered through a set of parameters. This also can improve resource choice. By sharing printers, it may be possible to offer a variety of types of printers and paper sizes, which is more practical and economical than trying to purchase several printers for each computer. See queuing. queue administration Queues are widely used to manage resource-sharing on a network. Whether the resource is a printer or modem, applications program, data file, or gateway to the Internet or Web, computer systems create, manage, authorize, and prioritize access to these resources and services through queues which are usually transparent to the user. On phone networks, queue administration may involve putting a caller on hold, checking to see if and when agents are ready to take the call, playing periodic messages to the caller, and assigning the call to the appropriate agent. On computer networks, queue administration may involve logging in users as they sign on to the system, checking for the existence of devices when a resource request occurs (e.g., a printing job), determining if others are in the queue, and where to slot the new request (the size of the print job, or relative priority of the user requesting the job may be taken into consideration), and may even change the queuing arrangement dynamically if another printer comes online or a print request is canceled before the job is run. Queued Telecommunications Access Method QTAM. An IBM communications control protocol which handles some applications processing tasks. QTAM is used in a number of telecommunications applications, including message switching, data processing, etc.

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Quarter Inch Cartridge Drive Standards QIC-140 QIC Stand. Date

Notes

Interface-related QIC-02 QIC-59 QIC-36 QIC-103 QIC-104

QIC-106

QIC-107

QIC-115

QIC-117

QIC-121

19-Apr-88 1/4-Inch Cartridge Tape Drive Intelligent Interface 28-Mar-85 1/4-Inch Cartridge Tape Drive Enhanced Basic Interface 14-Sep-84 1/4-Inch Cartridge Tape Drive Basic Interface 3-Feb-86 Basic Interface for QIC-100MC 1/4-Inch Cartridge Tape Drive 12-Feb-87 Implementation of Small Computer System Interface (SCSI) for QIC-Compatible Sequential Storage Devices 11-Feb-87 Single-Channel Magnetic Head for Use with QIC-40-MC FloppyInterface Minicartridge Tape Drives 5-Jun-86 Basic Drive Interface for Flexible-Disk-Controller-Compatible 1/4-Inch (6.35 mm) Mini Data Cartridge Tape Drives. 3-Feb-88 Basic Drive Interface for PS/2 Flexible-Disk-Controller-Compatible 1/4-Inch (6.35 mm) Minicartridge Tape Drives 28-Aug-96 Command Set Interface Specification for Flexible Disk Controller Based Mini Data Cartridge Tape Drives 14-Dec-95 Implementation of Small Computer System Interface (SCSI-2) for QIC-Compatible Sequential Storage Devices

Information Interchange-related QIC-24-DC 22-Apr-83 Serial Recorded Magnetic Tape Cartridge for Information Interchange (9 tracks, 10,000 FTPI, GCR, 60 Mbytes) QIC-40-MC 2-Sep-92 Flexible-Disk-ControllerCompatible Recording Format for Information Interchange (20 tracks, 10,000 BPI, MFM, 40 Mbytes) QIC-80-MC 20-Mar-96 Flexible-Disk-ControllerCompatible Recording Format for Information Interchange (28 tracks, 14,700 BPI, MFM, 80 Mbytes) QIC-136 23-Apr-97 Unrecorded Magnetic Tape Cartridge for Information Interchange (0.25 in., 45,000 and 50,800 ftpi, 900 Oe) QIC-137 20-Mar-96 Unrecorded Magnetic Tape Cartridge for Information Interchange (0.25 in., 38,750 ftpi, 900 Oe) QIC-139 23-Apr-97 Unrecorded Magnetic Tape Cartridge for Information Interchange (0.25 in., 50,800 ftpi, 900 Oe)

26-Feb-92 Read-Only Unrecorded Magnetic Tape Minicartridge for Information Interchange [For Program Distribution] (0.25 in., 10,000 to 14,700 ftpi, 550 Oe) QIC-141 26-Feb-92 Read-Only Unrecorded Magnetic Tape Cartridge for Information Interchange [For Program Distribution] (0.25 in., 10,000 to 12,500 ftpi, 550 Oe) QIC-142 26-Feb-92 Unrecorded Magnetic Tape Minicartridge for Information Interchange (0.25 in., 550 Oe, “Pegasus”) QIC-156 20-Mar-96 Unrecorded Magnetic Tape Minicartridge for Information Interchange (0.25 in., 45,000 ftpi, 900 Oe) QIC-159 20-June-96 Unrecorded Magnetic Tape Minicartridge for Information Interchange (0.315 in., 400 ft, 10,000 to 14,700 ftpi, 550 Oe) QIC-160 14-Dec-94 Unrecorded Magnetic Tape Minicartridge for Information Interchange (0.25 in., 425 ft, 10,000 to 14,700 ftpi, 550 Oe) QIC-161 13-Dec-95 Unrecorded Magnetic Tape Minicartridge for Information Interchange (0.315 in., 750 ft, 14,700 ftpi, 550 Oe, Travan) QIC-162 20-Mar-96 Unrecorded Magnetic Tape Minicartridge for Information Interchange (0.315 in., 750 ft, 44,000 ftpi, 900 Oe, Travan) QIC-163 20-Jun-96 Unrecorded Magnetic Tape Minicartridge for Information Interchange (0.315 in., 425 ft, 76,300 ftpi, 1800 Oe, MP++) QIC-180 27-Aug-97 Unrecorded, Servo Bursts, Track I.D., Magnetic Tape Minicartridge for Information Interchange (0.315 in., 740 ft, 79,800 ftpi, 1650 Oe) QIC-525-DC 10-Mar-94Serial Recorded Magnetic Tape Cartridge for Information Interchange (26 tracks, 20,000 ftpi, GCR, ECC, 525 MB) QIC-1000-DC 10-Mar-94Serial Recorded Magnetic Tape Cartridge for Information Interchange (30 tracks, 45,000 ftpi, GCR, ECC, 1010 MB) QIC-1350-DC 4-Mar-93 Serial Recorded Magnetic Tape Cartridge for Information Interchange (30 tracks, 38,750 ftpi, RLL 1,7, ECC, 1350 MB) QIC-2100-DC 4-Mar-93 Serial Recorded Magnetic Tape Cartridge for Information Interchange (30 tracks, 50,800 ftpi, RLL 1,7, ECC, 2.1 Gbytes with 875 ft of 900 Oe Tape)

QIC-3010-MC 27-Aug-97 Serial Recorded Magnetic Tape Minicartridge for Information Interchange (40 or 50 tracks, 22,125 BPI, MFM, 340 MBytes with 400 feet of 900 Oe 0.25-in. tape, 425 MBytes with 0.315-in. tape) QIC-3020-MC 20-Mar-96Serial Recorded Magnetic Tape Minicartridge for Information Interchange (40 or 50 tracks, 42,000 BPI, MFM, 680 MBytes with 400 feet of 900 Oe 0.25-in. tape, 833 MBytes with 0.315-in. tape) QIC-3030-MC 2-Sep-92 Serial Recorded Magnetic Tape Minicartridge for Information Interchange (40 tracks, 50,800 ftpi, GCR 4,5, ECC, 555 Mbytes with 275-foot 900 Oe Tape) QIC-3040-MC 20-Jun-96 Serial Recorded Magnetic Tape Minicartridge for Information Interchange (42 or 52 tracks, 50,800 ftpi, GCR 0,2 4,5, ECC, 840 MBytes with 400 feet of 900 Oe 0.25-in. tape, 1 Gbytes with 0.315-in. tape) QIC-3050-MC 14-Jun-95 Serial Recorded Magnetic Tape Minicartridge for Information Interchange (40 tracks, 38,750 ftpi, RLL 1,7, ECC, 750 MBytes with 295 feet of 900 Oe tape) QIC-3060-MC 4-Mar-93 Serial Recorded Magnetic Tape Minicartridge for Information Interchange (38 tracks, 50,800 ftpi, RLL 1,7, ECC, 875 MBytes with 295 feet of 900 Oe tape) (inactive) QIC-3080-MC 15-Dec-94Serial Recorded Magnetic Tape Cartridge for Information Interchange, 15 track, 0.250 in (6.35 mm), 10,000 bpi (394 bpmm) Streaming Mode Group Code Recording QIC-126 15-Jun-94 Magnetic Recording Head for Use in 1 GBQIC-1000-DC Cartridge Drives QIC-131 2-Dec-92 Magnetic Recording Head for Use in 555 MBQIC-3030-MC Minicartridge Drives QIC-133 27-Aug-97 Magnetic Head for Use in QIC-3010-MC and QIC-3020-MC Recording Format QIC-134 20-June-96 Magnetic Recording Head for Use in 4 GBQIC-3070-MC Minicartridge and 13 GBQIC-5010-DC Cartridge Drives QIC-151 15-Jun-94 Magnetic Recording Head for Use in 750 MBQIC-3050-MC Minicartridge Drives QIC-152 20-Mar-96 Preformatted Magnetic Tape Minicartridge for Information Interchange (0.25 in., 45,000 ftpi, 900 Oe) QIC-153 20-Mar-96 Unrecorded Magnetic Tape Minicartridge for Information Interchange (0.25 in., 70,000 ftpi, 1400 Oe) QIC-158 20-June-96 Magnetic Head for Use with 1.6 GBQIC-3080-MC Recording Format

QIC-171

QIC-177 QIC-178 QIC-179 QIC-181

11-Dec-96 Magnetic Head for Use with 4 GBQIC-3095-MC Recording Format 27-Aug-97 Magnetic Head for Use with QIC-3220-MC Recording Format 27-Aug-97 Magnetic Head for Use with QIC-3210-MC Recording Format 27-Aug-97 Magnetic Head for Use with QIC-4GB-DC Recording Format 27-Aug-97 Magnetic Head for Use with QIC-5210-DC Recording Format

Format-related QIC-112 QIC-113 QIC-123

27-Oct-87 ECC Format 15-Jun-95 Host Interchange Format 1-Sep-94 Registry of Data Algorithm Identifiers for 1/4-Inch Cartridge Tape Drives QIC-147 13-Dec-95 Cleaning Cartridge Recognition QIC-174 21-Mar-96 CD-ROM Compatible Tape Format for Installable File System QIC-176 28-Aug-96 Cleaning Cartridge Recognition with Light Prism QIC-CRF1 11-Dec-96 Common Recording Format with Multichannel Capability for Use with RLL 1,7 Encoded Recording Formats QIC-CRF2 15-Dec-94 Common Recording Format for Use with RLL 1,7 Encoded Recording Formats with Data Capacities of Less than 8 GB QIC-CRF3 21-Mar-96 Common Recording Format for Use with Flexible Diskette Encoded Recording Formats QIC 90-14 24-Apr-97 Hole Pattern assignments – 5.25 Inch Data Cartridge Identification Table QIC 91-16 24-Apr-97 Hole Pattern assignments – 3.5 Inch Minicartridge Identification Table QIC 95-101 27-Sept-97 Medium Types and Density Codes

Format-related - Compression QIC-122 QIC-130 QIC-154

6-Feb-91 Data Compression Format for 1/4-Inch Data Cartridge Tape Drives 3-Sep-92 DCLZ Data Compression Format 10-Mar-94 Adaptive Lossless Data Compression (ALDC)

Format-related - Protocols, Command Sets QIC-157 QIC-172 QIC-146

13-Dec-95 Common SCSI/ATAPI Command Set for Streaming Tape 20-Mar-96 Common SCSI/ATAPI Command Set for Floppy Tape 2-Dec-92 Autoloader SCSI Gateway Protocol: Serial Bus Implementation

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queuing delay QD. In its most general sense, a delay caused by queues or lineups within a system through which objects, information, or data are channeled. As a simple example, shopping in a downtown store with a queue at the cash register can result in a delay that causes a shopper to receive a parking ticket. When placing a phone call, a delay may be imposed on the caller by congested trunk lines or by the various switchers, routings, and routing priorities inherent in or configured into a system. Queuing delays can have many negative effects including customer frustration, loss of revenue, extra costs, and even death (in the case of emergency calls), so queuing theories and solutions are considered to be an important aspect of telecommunications. The queuing delay in a transmission system can be assessed in terms of particular legs within a route or in terms of a transmission as a whole, from sender to recipient. This is often a dynamic process without a single catch-all solution. Queuing delay is often evaluated in conjunction with other types of delays, including processing, propagation, and transmission delays. Queuing refers to those aspects where data or objects “bump up” against one another, in the sense that (usually) similar objects congregate “behind” one another in order to pass through a gateway or other channel that cannot accommodate the queued entities simultaneously. In cell-based transmissions, a queuing delay is a delay imposed on a cell due to the current inability of the cell to be passed on to the next element or function (because of congestion or errors). Depending upon the system and priorities, significant delays may have several results; the buffered cell data may be returned or destroyed. See queuing theory. queuing theory Queuing, in its broadest sense, involves an understanding of mathematics, statistics, modeling, data flow, and human behavior as they relate to the ways in which machines may be configured, tuned, and operated so as to carry out worthwhile tasks and processes in an efficient and orderly manner. Researchers in queuing theory regularly come from fields such as probability mathematics, complex systems theory, and simulation research. In the context of networking, queuing theory focuses on understanding, describing, and predicting patterns in transmission organization, priorities, delay, loss, and standards for quality of service (QoS). One of the most important pioneers of queuing concepts was Danish telephone engineer A.K. Erlang, who studied and described telephone traffic in its mathematical context and practical applications in the early 1900s. Another significant contributor to the body of knowledge in queuing theory is Leonard Kleinrock, who was involved in the early development of the ARPANET and who authored Information Flow in Large Communication Nets, in 1961. He subsequently wrote Communication Nets, in 1964, which provides design and queuing theory for building packet networks, in spite of a common sentiment at the time that packet switching wouldn’t work. Queuing theory is an important aspect of performance

evaluation and configuration in communications networks. Without a theoretical model for installing, configuring, and tuning a network, much time can be wasted in trying out the many different ways in which network traffic can be routed, especially in a heavily used system in which congestion and “bursty” traffic occur. Queuing applies to a broad range of environments, from individual circuit transmissions to global distributed networks. A single queue system is one of the most basic models discussed in queuing theory. When all traffic is routed through a single channel on a first-come, firstserved basis (e.g., a single cash register in a corner grocery store), the impact of extra traffic and overflow may be different from traffic management in multiple queue systems (a supermarket with multiple cash registers or multiple turnstyles at a sports stadium). The same concepts can be applied to telecommunications systems. A single phone routed through a dedicated line will be managed differently from a single line through a public phone system (wireline or wireless) where congestion might occur. The problems of queuing become more intricate when multiple users of multiple phones (or modems) are sharing network resources over a public network, especially in distributed networks where individual nodes may or may not be available at any particular point in time. See Erlang, Agner; queuing delay. QUICC See Quad Integrated Communications Controller. quick connection block A connection block for more quickly and easily making electrical connections without the necessity of learning to use specialized tools and wiring codes. Quick connection blocks are typically made of plastic or other nonconductive materials with metal terminal connecting points and may be preterminated for ease of installation. They are sold for a variety of uses, including electrical wiring, quick installation of multiple lights, computer network connections, and internal telephone line installation, especially for multiphone systems. Quick connection blocks are especially appealing to small businesses installing their own phone systems. These blocks enable wires to be inserted with easily available screwdrivers, pliers, and wire cutters rather than punchdown tools. One common configuration for telephone quick connection blocks is a premade 66 block, so-called because it supports up to 66 crossconnections. Panasonic has a commercial Quick Connect Block, a premade 66 block, that connects to the standard building wiring and supports up to eight analog or digital phone stations for each block (depending upon the phone model). Homaco, Inc. provides premade 66 blocks for telephone connections in 25-, 50-, and 100-pair sizes. Comm-Omni International supplies cable termination and surge protection for cables for multiple-family residences and office buildings (e.g., private branch exchange terminations) with a quick connection block accessory with 50 6-pin interconnected rows.

Quick File Access QFA. A system for enabling faster access to data on tape-based storage systems such as computer cartridge drives. Prior to QFA and similar systems, tape drives had to read through blocks of data sequentially to find the desired data, resulting in slow read times, especially if the desired data were near the end of the tape. With tapes and data stored on tapes getting longer, this became impractical. Thus, a system of commands known as Quick File Access enables a block number to be read so that the tape can be fast-forwarded to the appropriate place in the tape to locate the data. Since the block information pointers cannot be easily manipulated on tape, they are usually held in a database. Unfortunately, if the database is compromised (or logging disabled), then data location can be a problem (especially if it is a backup tape to restore a crashed system upon which the database was stored). Nevertheless, QFA is much more convenient than traditional serial-access tapes. quick-break fuse A type of fuse which breaks a circuit very quickly if a surge or other anomalous electrical condition occurs. Quick-break fuses are especially useful with electronics components, which are sensitive to electrical fluctuations and prone to damage. QuickDraw A widely used proprietary computer drawing and display specification from Apple Computer Inc. QuickDraw provides a means for displaying images on the screen and processing PostScript files so they can be printed on nonPostScriptequipped printers. quicksilver colloq. mercury. QuickTime A proprietary cross-platform computer display, audio, and animation environment from Apple Computer Inc. that runs on Macintosh, PowerMac, Windows 95, Windows NT 4.0, Windows ME, and Windows 2000. QuickTime is actually a suite of software applications for supporting picture display, multimedia authoring, and server support for streaming audio/video. QuickTime allows some interesting applications to be developed and distributed, including frame-based animation, whiteboarding, video clips, teleconferencing applications, virtual reality environments, games, and more. The QuickTime format is widely supported on the Internet, with many Web-based multimedia applications distributed in QuickTime. Many digital cameras also support the QuickTime format. Most recently, QuickTime has been enhanced to support streaming media in Internet browsers (HTTP, RTP, RTSP) to support more than 30 different audio and video file formats (AIFF, BMP, GIF, JPEG, MPEG-1, MP3, M3U, PICT, PNG, SGI, Targa, TIFF, VR, Wave, and more), and added modules for saving digital video (DV) camcorder formats for the development of digital video. Most QuickTime software is freely distributed, including the QuickTime Player and PictureViewer. The QuickTime Streaming Server and Darwin Streaming Server are also freely distributed, with no streaming data license fees. QuickTime Pro is

commercial software, available for about $30. QuickTime 3D Apple Computer’s 3D QuickTime cross-platform 3D rendering software. QuickTime Conference QTC. Designed on Apple Computer’s QuickTime compression technology, QuickTime Conference supports videoconferencing in a window on the computer screen. Electronic whiteboarding is also supported, so participants can communicate and collaborate on shared drawing, text, or other projects. The software can be used to deliver Web events using QuickTime Live! software. See Simple Multicast Routing Protocol. QuickTime Player A software application for playing back audio and video files created by QuickTime Pro authoring software and other applications that export the QuickTime Pro authoring file format. QuickTime 5 has support for skip protection for streaming sources with uneven video delivery, media “skins” to enable the user to customize the look of the player, Internet TV channel display and audio control features, and support for plugins from Apple and third-party developers. QuickTime Pro A low-cost, commercial authoring system for creating QuickTime multimedia images and presentations. It supports many popular file formats that may be played on freelydownloadable QuickTime Player programs. QuickTime Streaming Server An extension to QuickTime that delivers multimedia files in realtime over the Internet using the Real-Time Transport Protocol/Real-Time Streaming Protocol (RTP/RTSP). Thus, it can deliver video on demand and, when combined with broadcasting software, can deliver live streaming news, interviews, or entertainment through a network. QuickTime Streaming Server is available in Mac OS X Server and the Darwin Streaming Server is available through the Darwin open source project. The Streaming Server is available on a variety of platforms and the open source software makes it possible to port to additional platforms. The software provides Web-based server configuration, TCP-based broadcast support, skip protection, and other features. QuickTime VR An extension to QuickTime that adds cross-platform virtual reality capabilities through a movie-like presentation of images. The user can move through the scene, pan the surroundings, interact with objects, and much more. QuickTime Authoring Studio can be used to create virtual reality scenarios for display in QuickTime VR. QTVR Make Cubic enables users to build Cubic Virtual Reality software. quiet tuning In radio receivers, a tuning characteristic in which the signal is kept quiet, that is, not broadcast to the listener, except when the tuner is getting a clean, clear signal of a specified frequency on the incoming carrier wave. In other words, if it isn’t a good signal, the receiver mutes the sound to

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save the listener from the distraction of weak or noisy stations. Quorum International The marketing and distribution arm of Applied Electronics, a Hong Kong-based Original Equipment Manufacturer (OEM). Applied Electronics supplies many major computer and telecommunications companies, including National Semi Conductor, IBM, Texas Instruments, and others. The range of products includes security systems and pagers. In conjunction with MCI, the MCI-Q Program was developed to enable Quorum to purchase telecommunications products and services at special rates. Through the Quorum Associate Distributor (QuAD), distributors receive discounted MCI Q-Connection rates and access to additional services (pagers, personalized calling cards, etc.). Quorum Teleconferencing Bridge A commercial, integrated voice and data device from AT&T to facilitate conference call set up and administration. The Quorum Teleconferencing Bridge connects and controls multipoint conference calls. It enables a local operator to set up, control, and monitor up to four simultaneous conference calls from participants in up to seven locations for each call (or a single meeting with up to 28 locations). QWERTY A ubiquitous computer and typewriter keyboard configuration designation, named after the six lettered keys on the top left side. Although each computer keyboard has a variety of individual symbol and function keys, most follow common QWERTY configurations for numbers, letters, and common punctuation marks. This configuration was originally designed to slow down typing in order to help prevent jamming on the old manual typewriters (anyone who has used one knows how easily they jam). Other keyboard layouts have since been proposed which consider ergonomics and physical properties,

the most recognized being the keyboard designed by August Dvorak. The Dvorak keyboard was developed on the basis of studying finger motion and lettering combinations which were easier and more efficient to execute, and incorporating them into new keyboard character arrangements. A number of variations of this by other people have also been called Dvorak keyboards, even when they differ from that developed by A. Dvorak. Unlike typewriters, computers make it relatively easy to remap the key positions and alternate keyboards can be designed to put the letters anywhere the user desires. In spite of this, the QWERTY keyboard has remained prevalent, and manufacturers and teaching institutions are reluctant to change to other systems, even if they have advantages. Qwest Communications A telecommunications company creating fiber optic networks in over 100 U.S. and Mexican cities. Commercial services provided by Qwest include dedicated business Internet access, Internet faxing, Internet phone (Q.talk), and video. In June 2000, Qwest Communications International Inc. completed a merger with U.S. West, Inc. creating an announced $85 billion market capitalization with services in 14 states. In October 2001, Qwest and its principal shareholder, Anschutz Company, announced plans to purchase 14 million and 6 million shares, respectively, of the Netherlands company Koninklijke KPN N.V. The company further announced plans for the acquisition of Global TeleSystems, Inc., indicating a significant European expansion. QZ billing A telephone subscriber service in which the time and charges for an outgoing call (usually a toll call) can be obtained from the phone company. This is especially useful for business professionals and educational institutions that bill back to the calling department. QZ billing is being superseded by automated call accounting information.

r abbrev. roentgen (røntgen). See roentgen. R 1. symb. range. 2. symb. resistance. See resistance. R interface In ISDN, a number of reference points have been specified as R, S, T, U, and V interfaces. To establish ISDN services, the telephone company and ISDN subscriber typically have to install a number of devices and links to create the all-digital circuit connection necessary to send and receive digital voice and data transmissions. The R interface is the portion of the link between an ISDN terminal adapter (TA) on the customer premises, and customer non-ISDN station equipment (TE-2) such as phones, facsimile machines, computers using modems, etc. Some communications devices are being manufactured with ISDN terminal adapters built in, in which case, the R interface is not needed (or is considered to exist inside the component itself). See ISDN interfaces for a diagram. R reference point In ISDN, the point in the digital communications path at which non-ISDN TE-1 devices connect to a Terminal Adapter (TA). See R interface. R Series Recommendations A series of ITU-T recommendations providing guidelines for radio systems, operations, and spectrum use. These guidelines are available as publications from the ITU-T for purchase from the Net. Since ITU-T specifications and recommendations are widely followed by vendors in the telecommunications industry, those wanting to maximize interoperability with other systems need to be aware of the information disseminated by the ITU-T. A full list of general categories is listed in Appendix C and specific series topics are listed under individual entries in this dictionary, e.g., S Series Recommendations. See R Series Recommendations chart. R-Y red-luminance. In the YUV video color model in which chrominance and luminance are separate, the color R (red) minus Y (luminance) equals V, which is used to calculate color differences. Associated with this is the color B (blue) minus Y (luminance) equals U. If both calculations were to be zero (0), it would indicate no color (chrominance). In video engineering, R-Y (red - luma) and B-Y (blue luma) are multiplied by defined values to derive V and U, respectively. Color difference components

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with luma removed are represented as R´-Y´ and B´-Y´. Color component removal is a mathematical approach to decomposing a YUV video signal that is useful for a variety of reasons, including as a means to reduce bandwidth for transmission and for special effects. It is used in the PAL analog video standard and CCIR 601 digital video standard.

ITU-T R Series Recommendations Subseries BO BR BS BT F IS M P PI RA S SA SF SM SNG TF V

Description Broadcasting-satellite service (sound and television) Sound and television recording Broadcasting service (sound) Broadcasting service (television) Fixed service Inter-service sharing and compatibility Mobile, radiodetermination, amateur and related satellite services Radiowave propagation Propagation in ionized media Radioastronomy Fixed-satellite service Space applications and meteorology Frequency sharing between the fixedsatellite service and the fixed service Spectrum management Satellite news gathering Time signals and frequency standards emissions Vocabulary and related subjects

R/T 1. See realtime. 2. receive/transmit. R/W read/write. R&D See research and development.

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R&E 1. See Research and Education. 2. research and engineering. R&S research and statistics. R1 signaling A type of signaling scheme commonly used in channelized voice networks in North America and Japan that is typically implemented through a T1 line. It enables supervisory and address signals to be transmitted between network switches using a single frequency for supervisory (line) information and multiple frequencies for address (register) information. T1 signaling is specified in ITU-T recommendations Q.310 to Q. 331. See channel-associated signaling, R2 signaling. R2 signaling A type of signaling scheme commonly used in channelized voice networks outside North America and Japan. In association with E1 networks, it is similar to channelized T1. R2 implementations tend to be variants of ITU-T Q.400 to Q.490 recommendations; there is some flexibility in the channelized signaling parameters for setting the parameters for specific countries, an important capability in the multicultural European Union. Signal types are configured as line signals and interregister signals. See channel-associated signaling, R1 signaling. RA 1. radar altimeter. 2. rate area. A region designated to receive products and services at described rates for the purposes of administration and billing. 3. See RealAudio. 4. Reliability Action Center. RA number See return authorization number. A number assigned to products returned to the vendor or manufacturer. The number documents that the return was authorized and provides a number for tracking and stock-handling purposes once the product has been received at the return point. RA-EN See Radio Amateur Emergency Network. RAC 1. See Radio Amateurs of Canada. 2. Radio Austria Communications. Based in Vienna. 3. See remote access concentrator. RACE 1. random access computer equipment. 2. See Research in Advanced Communications in Europe. RACES See Radio Amateur Civil Emergency Service. raceway A duct or channel system designed to hold, protect, and direct interior wiring circuits. Raceways are typically plastic or metal modular construction, with a variety of fittings so individual sections can be interconnected and holes can be punched where needed. Raceways can be mounted on or in walls or floors. See molding raceway. RACF 1. See Radio Access Control Function. 2. See resource access control facility. rack, tray A support structure designed for the easy insertion, removal, and configuration of modular component systems. Racks are frequently equipped with rollers, although large ones may be attached to a wall for better support. They are generally assembled from rigid metal strips, interconnected to produce a strong open structure so the components can be quickly slid in and out of the individual bays from the front, and cabled to one another at the back. Racks are commonly used in the broadcast TV and

video editing industries; they can also be found in telephone switching installations and on large computer networks with a variety of storage media. See distribution frame, rack unit. rack mountable A component designed to specifications so it will fit easily and securely into a storage and support rack of a standard size for components from that industry. See rack, rack unit. rack unit RU. A measure of distance based on physical rack structures that are common within various industries. Rack sizes have long been standardized in the power distribution, audio/visual, and portions of the retail sales industries. Racks are especially common for supporting video processors, frame synchronizers, frame grabbers, and other video editing and broadcast components. In the video industry, the rack width for rack-mountable audio and video components is typically 19 in. and the vertical rack unit (RU) is 1.75 in. Thus, a 3.5in.-high component would be described as having a height of 2RU. See rack. racon See radar beacon. RACS 1. remote access calibration/control/computing services/system. RACT remote access computer/control terminal. rad radiation absorbed dose. A quantification of radiation energy that describes how much radiation is delivered to 1 g of a substance by 100 ergs of energy. Radiation absorbed by body tissue is measured in roentgens. RAD 1. rapid application development/design. 2. See Radiance. 3. random access device. 4. recorded announcement device. 5. remote antenna driver. radar radio detection and ranging. In its basic form, radar is a means of detecting distant or unseen objects by emitting radio frequency electromagnetic waves and measuring the reflected response. As such it can operate at night, during fog, and in situations where something is too distant to be seen by unaided eyes. Radar works on the principle that radio waves will deflect off of solid or sufficiently dense objects in a way that can be anticipated or controlled so the returning signal can be analyzed for the presence of the objects, their general shape and size, and their distance. Radar is a powerful and flexible technology that has become an intrinsic aspect of navigation, reconnaissance, and imaging systems. Radar typically operates in ultra high frequencies (UHF) and microwave frequencies. See radar, history; sonar; Taylor, A.H. radar, history Radar and sonar originated in much the same way in the late 1800s and the two technologies still share many terms and general principles. Johann Christian Doppler (1803-1853) made important contributions to both radar and sonar history by studying the way in which compressions arising from motion could alter sound frequencies, relative to the position of the viewer (or sensing instrument). It was discovered that this characteristic was also applicable to electromagnetic phenomena like radio waves and light, resulting in Doppler radar technologies about 100 years later.

This is a mobile radar-based detection system used by the military to assess incoming artillery such as mortars and gun rounds down to .50 calibers. The information from the sensors can be processed to determine the geographic source and probable landing location of an incoming fire. This system is part of the NATO Implementation Force effort that was deployed to the Bosnia region in 1996. [U.S. DoD photo by J. Schaible, 1996, released.]

The fact that electromagnetic waves could be reflected was first demonstrated by Heinrich R. Hertz (1857-1894) in 1886. In 1904, Christian Hülsmeyer (1881-1957) patented a “far-moving scope” which used reflected radio waves (early radar) for detecting marine vessels in order to prevent collisions at sea, a system that eventually superseded searchlights for detecting nearby vessels in the dark or fog. In 1906, William R. Blair described the use of electromagnetic oscillations to determine the incident energy returning from various reflecting surfaces. By 1916, interest in radio sensing devices was spreading rapidly. Dominik and Scherl had invented a radio echo sensing device in Europe and Nicola Tesla, in 1917, wrote about radar concepts in the Electrical Experimenter in America. The earliest commercial use of radio frequencies for bouncing signals was in the 1920s and 1930s, where it was used to determine the presence of marine vessels and aircraft to help prevent collisions. By the mid-1930s, when cathode-ray tube displays were becoming commercially viable, radar was used in both military and commercial navigation and documented in engineering textbooks. With the onslaught of World War II, interest in radar increased dramatically and substantial resources were devoted to its improvement and adaptation for military purposes. Since then, radar has been adapted to many industries and continues to be used for its original purpose, navigational safety, and for many diverse military and commercial applications. See radar. radar beacon A device associated with a particular

location or object that is capable of emitting a radarrange radio signal to indicate its geographic location. A passive radar beacon is one that sends out a radar signal from time to time that can be sensed by an appropriately tuned radar receiver within range. However, it does not have a receiver and cannot detect whether a radar signal has been aimed in its direction. An active radar beacon includes both a radar receiver and a radar transmitter. The receiver enables the beacon to sense a triggering pulse from a remote radar that causes the beacon to broadcast a returning signal or a series of returning signals. The information contained within the signal depends upon the system used, but can provide range, bearing, and, optionally, identification information. Because radar technology tends to be expensive, radar beacons are more often installed in industrial shipping facilities and military applications than in consumer devices. Sometimes they are used in lighthouses.

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Much attention has been given to the development of radar technologies for navigation and military tracking purposes. This radar scope, on board a U.S. aircraft carrier, is used for aircraft approach control. Civilian and military air traffic control personnel ensure the safe and orderly flow of air traffic in commercial airports and on military vessels at sea. This photo was taken during NATO Implementation Force (IFOR) patrols of the waters of the Adriatic Sea. The U.S. Air Force C-14B aircraft was the first to use ground-based radio beacons for a completely automated landing in August 1937. The system of five transmitting beacons used to accomplish this feat was developed by Carl J. Crane. [Detail of DoD photo by J. Hendricks, U.S. Navy.]

Some less expensive radar beacons do exist, however, in the form of police speed detectors. The speed detector determines a vehicle’s speed by sending out a radar pulse that essentially acts as a beacon to any

suitably tuned automobile radar detection units within range. radar detector A device designed to detect the presence of radar-range radio signals. These are used in military applications to detect or interpret radarrange communications. They are also sold for civilian use in the form of car-mountable devices to detect police speed-detection radar systems. The use of radar detectors is regulated and prohibited in some areas. See radar, radar beacon. radar screen/scope A small display device, usually round or rectangular, which shows target signals as illuminated dots or blips. There may be grids and other alignment and location marks superimposed over the illuminated blips on the screen to aid in tracking and location. The term radar “scope” comes from the early days when cathode-ray tubes (CRTs) were being adapted for use as oscilloscopes and various types of radar screens. See radar. radar systems Devices incorporating radio waves to detect the presence and characteristics of distant or otherwise unseen objects. Although radio echoes were observed in the 1920s and put into practical use in the 1930s, developments in radar guidance, detection, and identification systems did not flourish until the second World War. See cavity magnetron. RADARSAT A Canadian satellite system launched in November 1995. The satellite supports a syntheticaperture radar sensor that can deliver data in seven sizes based upon 25 beam positions. Images vary, depending upon the way the sensors are angled and the Earth viewed. Each beam position has a specific elevation angle and size. The two beam modes are single beam and multiple-beam ScanSAR. RADARSAT is part of the RADARSAT Network System. radial acceleration Acceleration in a circular trajectory, characteristic of a spinning solid or liquid substance. Radial acceleration is used in centrifugal separators to isolate particular particles or substances. The radial acceleration characteristics of various spiraling entities are of interest to astronomers. In optical media, radial acceleration is one of the characteristics measured to determine conformance with expected properties or standards, along with axial acceleration and radial runout. Radiance RAD. A native file format for Radiance, a public domain Unix-compatible radiosity rendering engine. The file extension .rad may be used to distinguish RAD files. radiant energy Transmitted electromagnetic energy such as heat, light, or radio waves. Radiant energy is typically measured in calories, ergs, or joules. radio An appliance or other device designed for the transmission and/or receipt of radio wave communications. There are many types of radio technology: amplitude modulation (AM), frequency modulation (FM), shortwave, cellular, short-range (cordless phones, wireless intercoms), etc. With increased demand for wireless communications, harnessing and using radio waves efficiently has become extremely important in both scientific and commercial research. More details about radio communications can be

found under individual listings in this dictionary. See crystal detector, detector. Radio The publication name of a widely-distributed Soviet electronics journal which, in June 1957, announced the Soviet Union’s plans to soon launch a satellite (“sputnik” in Russian), and provided details of the planned launch date, modulation techniques, and frequencies to be used. Sputnik I did in fact launch at the end of that year. See Sputnik I. Radio Access Control Function RACF. In a PACAE Personal Communications System (PCS), the RACF intercommunicates with a number of entities while handling the service logic, including the Radio Control Function (RCF) and the Call Control Function (CCF)/Service Switching Function (SSF). See Priority Access and Channel Assignment. Radio Act of 1912 With increasing interest in radio broadcasting and demand on airwaves, the U.S. Congress passed an act which granted the U.S. Department of Commerce the authority to regulate amateur broadcasting in order to prevent interference with government stations and to increase maritime safety, largely due to the sinking of the Titanic. See Titanic. Radio Act of 1927 As a response to the enormous rising demand for broadcast channels in the early part of the century, a conference was held to sort out the chaos. As of the Radio Act of 1912, the U.S. Department of Commerce took control of radio broadcasting. Zenith Radio Corporation applied for a license to operate at a frequency that was being used by other stations as well, and so was granted a license to broadcast at a different frequency. Zenith changed frequencies to one that had already been granted, instead of using the one that had been licensed. In the process of investigating the violation, it was found that the Department of Commerce didn’t have sufficient jurisdiction to stop the actions of the broadcaster, and one of the consequences was the creation of the Federal Radio Commission (FRC) in 1927. This was later to become the Federal Communications Commission (FCC) through the Communications Act of 1934. See Communications Act of 1934, Federal Communications Commission. Radio Advertising Bureau RAB. A national trade organization established in 1950 as the Broadcast Advertisers Bureau to promote radio as an effective advertising medium. The organization collected ads from all over the country and began sponsoring awards for excellence in radio advertising. The collection is now housed as the Radio Advertising Bureau Collection at the Library of American Broadcasting. The majority of the examples in the archive are from 1958 to 1964. Radio Amateur Civil Emergency Service RACES. A public emergency service provided by reserve volunteer communications personnel to assist regular emergency services in times of extraordinary need. The organization was established in 1952. Planning guidance for RACES deployment is provided by the Federal Emergency Management Agency (FEMA). http://www.races.net/ Radio Amateur Emergency Network Raynet. Raynet was established as a result of a violent storm

that pummeled the eastern coast of England in January 1953. Coastal towns and villages were ravaged and more than 300 drowned. Since telephone lines were destroyed as well, there was no reliable communication into or out of the area during the storm. The police authorities appealed to radio amateurs to help and the Home Office gave permission for amateur radios to coordinate rescue services, saving many lives. Thus RA-EN was born, and grew in capabilities in 1989 when legislation restriction was lifted to enable the organization to provide greater help. It is now known as Raynet. Radio Amateur Satellite Corporation RASC, AMSAT-NA. This is the North American branch of the international amateur radio satellite community, a not-for-profit agency founded in 1969. Over the decades, radio amateurs have made significant contributions to the evolution of satellite broadcasting technologies in spite of the budget constraints typical of amateur organizations. AMSAT-NA supports and promotes scientific research and development in radio communications satellites and space science in the public interest. The air waves, by legal right in the U.S., belong to the people, and radio amateurs are exercising not only their right to use this wonderful resource, but have furthered the art of wireless communications in countless ways. AMSAT has successfully launched more than two dozen noncommercial radio communications satellites into Earth orbit since the historic OSCAR satellites of the early 1960s. See AMSAT, OSCAR. http://www.amsat.org/ Radio Amateurs of Canada RAC. RAC provides liaison, coordinating functions, and policy decisions for the benefit of Canadian amateur radio organizations and individual amateur radio operators. http://www.rac.ca/ radio astronomy The art and science of electromagnetic waves, especially those distant from the Earth, used in radio communications, including their characteristics, control, and practical applications. See sky maps. radio broadcasting Commercial radio broadcasting began in the early 1900s, arising out of the experimental broadcasts of inventor R. Fessenden in 1906. There were many amateur broadcasts between 1906 and 1920, including the regularly scheduled shows by Charles “Doc” Herrold, at the Herrold College of Wireless and Engineering in California, and the pre-KDKA broadcasts from the garage of F. Conrad in 1919. CFCF amd KDKA are acknowledged as the first commercial stations, beginning in 1920. Commercial broadcasting in Europe was underway by 1913, and the Eiffel Tower still stands as a historic reminder of the lofty ambitions of the broadcast pioneers. It was built for the Paris World’s Fair in the 1800s and there have been several attempts to remove it since then, but its usefulness as a giant antenna is one of the reasons it was preserved. Lee de Forest participated in one of the first transcontinental broadcasts from the world’s largest radio tower. The Radio Corporation of America (RCA), founded in 1920, is one of the most well known and influential

of the early radio pioneers, and much of its history is related to the activities of David Sarnoff. Sarnoff was also instrumental in forming the National Broadcasting Corporation (NBC), in 1926. The following year the Columbia Broadcasting System (CBS) was formed (originally Columbia Phonograph Broadcasting until William S. Paley bought out the company in 1928). From 1921 to 1922 the number of commercial stations in the U.S. increased from five to over 500. In the early 1930s, record companies became nervous about competition from radio stations and began restricting the open broadcasting of audio recordings. From that point on, royalties and other means of enforcing payment for broadcasts were instituted. By the late 1930s the wonderful music from bands and orchestras around the world could be heard through the magic of radio, and listeners who had never been to a theater to hear a live performance enjoyed the new form of entertainment. The advent of radio meant the eventual death of vaudeville, but some of the vaudevillian actors, perhaps best exemplified by George Burns and Gracie Allen, made a successful transition to radio, and eventually to TV programming. By the early 1940s, frequency modulated (FM) broadcasting, made possible by the tireless efforts of inventor Edwin Armstrong, was beginning to catch on and, while it didn’t supersede AM, it provided clean, clear transmissions that were favored by public broadcast and classical music stations. The invention of the transistor created a revolution in miniaturization and manufacturing. By the 1950s, radio had competition from TV broadcast stations, but unlike many technologies, it didn’t lose its practicality and appeal. Radio stations in North America still outnumber TV stations, and radio sets continue to be in demand. The next major milestone in radio broadcasting came with Sputnik and the exploration of space. In 1969, American astronauts sent sound and images from the Moon to Earth. Soon communications satellites were being launched into orbit in the 1970s and 1980s. This provided a means to develop mobile communications, and linked computers and radios as never before. Many of the pioneer communications efforts and new technologies were contributed by amateur radio enthusiasts, most notably through the OSCAR and AMSAT satellite programs. With digital electronics, laptops, and cell phones, the importance of radio continued to grow, as wireless communications were integrated into increasingly mobile lifestyles. One of the significant recent events in radio broadcasting is the introduction of digital broadcasting, pioneered by Sweden in 1996. See AMSAT; ANIK; CKAC; Emergency Alert System; KDKA; OSCAR; Radio Corporation of America; Sarnoff, David; radio history. radio broadcasting regulations Many different sets of guidelines and regulations have been developed to manage radio broadcasting. Some of these were intended to curtail unfair business practices, such as more powerful transmitting stations deliberately

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drowning out less powerful ones, and some were implemented to organize and coordinate the use of limited airspace, that is, the limited availability of broadcast frequencies. Others were put into effect in wartime to shut down broadcasting almost entirely, curbing the broadcast pirates, but also curbing responsible amateurs. In 1963 the Emergency Broadcasting System (EBS) was established, recently replaced in 1997 by the Emergency Alert System (EAS). Several Radio Acts and later Telecommunications Acts have controlled American broadcasting over the decades. The jurisdiction has changed hands a number of times, from the U.S. Secretary of Commerce to the Federal Radio Commission (FRC) in 1927, to the Federal Communications Commission (FCC) in the mid-1930s. The FCC has retained its wide-ranging licensing and regulatory powers up to the present time. See Emergency Alert System, Federal Communications Commission, Radio Act of 1912. radio button A physical button on a component, or iconic button in a software program, which permits selection of only one option from a group of mutually exclusive selections. Selecting any one option automatically deselects the previous option. The name derives from the action of pushbutton radio sets in which buttons can be pretuned to selected stations, and then pushed for the desired station, one at a time. Software radio buttons are often seen on input forms on Web pages. Radio Club of America This historic amateur radio group is still operating after its birth in the early 1900s. It held its first meeting in 1909 and was founded as the Junior Wireless Club Limited in 1910 in New York City. The organization changed its name the following year to the Radio Club of America. The young members of the club successfully lobbied for the interests of amateur radio enthusiasts before the U.S. Senate Commerce Subcommittee. The first official meeting of the organization under its new name was in November 1911. As it grew, some of the great names in radio history became associated with the club, including Paul Godley, Edwin Armstrong, and David Sarnoff. It exists for the charitable, educational, and scientific furtherance of radio communications and provides scholarship funds for needy and worthy students of radio communications. See Junior Wireless Club Limited. http://www.radio-club-ofamerica.org/ Radio Common Carrier RCC. Service providers of mobile telephone and paging services employing radio technology, as opposed to land line transmissions. Radio Communication Laws of the United States The sinking of the Republic and the Titanic, in addition to the International RadioTelegraphic Convention, were strong factors in the development of American regulations for radio communications. In 1910 and 1912, U.S. acts were approved resulting in the publication of the Radio Communication Laws of the United States and the International Radiotelegraphic Convention, by the U.S. Department of Commerce Bureau of Navigation Radio Service, in

1914. This document described the major international agreements and U.S. radio regulations and guidelines and spelled out the requirement for any steamer navigating U.S. waters carrying 50 or more persons to be “... equipped with an efficient apparatus for radio communication ... capable of transmitting and receiving messages over a distance of at least one hundred miles, day or night. An auxiliary power supply, independent of the vessel’s main electric power plant, must be provided which will enable the sending set for at least four hours to send messages over a distance of at least one hundred miles, day or night, and efficient communication between the operator in the radio room and the bridge shall be maintained at all times. The radio equipment must be in charge of two or more persons skilled in the use of such apparatus, one or the other of whom shall be on duty at all times while the vessel is being navigated....” The document further described licensing requirements for amateur and commercial operators, stipulated the designation of certain definite wavelengths as normal communications frequencies for a station, and standardized SOS (dot-dot-dot dash-dash-dash dot-dot-dot) in Morse Code as the official distress call, in addition to other basic tenets of radio communications. See International Radiotelegraphic Convention. radio control The control of various models, vessels, and other moving objects by means of radio waves. J. Hammond received a patent for radio control technology in 1912. Radio Control Function RCF. In a PACA-E Personal Communications System (PCS), the point towards which Radio Terminal Function transmissions are directed and from which the RTF interacts with other network entities in the processing of a PACAE (priority access) call. See Priority Access and Channel Assignment. Radio Corporation of America RCA. An offshoot of General Electric founded in 1919 as a result of a merger with the Marconi Wireless Telegraph Company of America. In 1920, RCA made a significant agreement with WSA, AT&T, GE, Westinghouse, and others, to be the exclusive distributor of radio receiving sets and crystal detectors. In 1921, David Sarnoff joined the company as its general manager, and later moved up in the corporation, becoming vice president in 1926. Sarnoff was a colorful part of its history for many decades. See Armstrong, Edwin Howard; Sarnoff, David. radio facsimile The transmission of the contents of pages including text and images by means of radio signals. Radio facsimiles were pioneered in the 1800s, and this early form of facsimile machine was in use at least as early as 1943. See facsimile. radio frequency RF. Radiant electromagnetic waves that range from about 3 to 10 kHz at the lowest end to just about 300 GHz at the high end, a position that falls between the audio frequencies and the boundary of the visible spectrum where infrared is found.

Radio frequencies are widely used for radio and television broadcasting, and for various types of wireless communication. The frequency range has been administratively subdivided into a number of categories so that limited airwaves can be assigned and licensed in an efficient way. In the U.S., this responsibility is managed by the Federal Communications Commission (FCC); in Canada it’s managed by the Canadian Radio Television and Telecommunications Commission (CRTC). See band allocations for chart. radio history Radio history is one of the most interesting histories in technology. As soon as humankind discovered that communications could be transmitted at the speed of light, they enthusiastically sought ways to achieve practical embodiments of the possibilities. The gradual discovery and harnessing of electromagnetic frequencies to carry meaningful communications changed society in fundamental ways and radio waves have since been developed for a bewildering variety of technologies, from interstellar telemetry to radar range ovens that almost instantly cook food. The earliest radios were low-power crystal detectors that exploited the oscillating properties of natural and synthetic crystals to “capture” (resonate with) radio waves and transmit the signal to earphones worn by the listener. This wasn’t a very easy way to share radio communications with a room full of people, so improvements for increasing the sound volume and the development of antennas to intercept the signals were pursued by radio inventors. The significant history of modern radio technology starts with Lee de Forest’s invention of the Audion, a three-element electron tube derived from Fleming’s two-element tube. The addition of the third element was highly important, as it enabled the flow of electrons to be controlled which, in turn, made it possible to build radio signal amplifiers for hundreds of different applications. De Forest claims he made voice broadcasts from New York around 1906. In 1916 he broadcast incorrect election results. With the development of practical methods of radio broadcasting, creative minds quickly grasped the social, cultural, military, and commercial applications of radio communications. Experimental radio stations sprang up everywhere beginning around 1910 with many early broadcasts sent in Morse code. Consumer radio sets, called “talking machines,” gradually replaced hobbyist crystal radios. Guglielmo Marconi was a young, ambitious inventor who became a prominent radio pioneer. He was the first to develop many radio technologies and the first to use or adapt many technologies developed by other all-but-forgotten inventors. A true broadcasting pioneer, Doc Herrold began transmitting in 1909 and made history by airing music and news to the 1915 World’s Fair. In 1916, he received callsign 6XF from the U.S. Department of Commerce. At about this time, Leninn began using radio to reach the public in Russia while Marconi set up broadcasting in Europe and North America. Wartime restrictions hampered broadcasting around this time but didn’t stop the evolution of radio. In

Montreal, Canada, Marconi’s station XWA received an experimental license in 1918, a general license in 1919, and broadcast its first regularly scheduled musical concert in May 1920. XWA evolved into CFCF in November 1920. Station KDKA in Pittsburgh (under its original 8Xk call sign) broadcast election events in November 1920. No doubt there are many uncredited radio pioneers as early callsigns were self-assigned, the technology was loosely regulated, and few listeners existed to credit the true pioneers. From the 1920s onward, however, regulated radio broadcasting flourished, making it easier to unravel and confirm its history.

President Herbert Hoover listening to an early electron tube-based radio set, around 1925. Hoover and Coolidge were two of the first presidents to exploit the informational and political potential of radio communications. [Library of Congress American Memory National Photo Company Collection.]

Calvin Coolidge was quick to exploit radio technology in the U.S. in the 1920s, for political communications, as was Vladimir Lenin in Russia. Radio is now an inextricable aspect of political campaigns and communications and is used by government agencies for coordination, national security, and emergency services. The general public benefited from wireless letters and radio broadcasting. The importance of the development of transistors at the Bell lab in the late 1940s cannot be overstated. Transistors not only made it possible to shrink building-sized computers down to the size of a large photocopier, but enabled portable radio technologies and mobile communications technologies to evolve and flourish from the 1950s onward. The semiconductor industry further enabled hardware engineers to combine many functions on a single chip, increasing processing speeds and reducing component sizes even further. Radio is still a highly significant communications technology, which is now being incorporated into telephones and other traditional wired devices. The evolution of the technology is ongoing.

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See Audion, CFCF; Conrad, Frank; crystal detector; Herrold, Doc; KDKA; Marconi, Guglielmo; Tesla, Nikola; telegraph history; XWA.

The masthead from The Talking Machine World, a monthly journal issued from Madison Avenue, New York, a useful resource for historic “radiobilia.” It was published between 1905 and 1928 to provide trade information for manufacturers and distributors of photograph and radio products. One of the articles describes the Thomas A. Edison company marketing a new 12-in. “long play” record that would play for over 20 minutes. [January 15, 1926 issue.]

and governmental organizations. The RTCA includes prominent names in the aviation industry, including the National Business Aviation Association, NASA, the National Air Traffic Controllers Association and various international airlines, and pilot associations. It makes recommendations to the Federal Aviation Administration (FAA) (also a member). http://www.rtca.org/ Radio Terminal Function RTF. In a PACA-E Personal Communications System (PCS), the RTF is the point from which the PACA-E subscriber accesses the mobile communications network. Communications are directed from the RTF towards the Radio Control Function (RCF) through which it can interact with other network entities. See Priority Access and Channel Assignment. radio wave An electromagnetic wave, commonly used to carry audio transmissions, in a frequency spectrum that ranges from 10 KHz to 200 GHz. Transmission waves such as radio waves are further classified into subcategories according to various properties; examples include ionospheric waves (sky waves), ground waves, short waves, and others. The characteristics of various transmissions media, chiefly the Earth’s ionosphere, are exploited to aim and propagate these waves. Frequency divisions of radio waves according to wavelength (higher frequencies have shorter wavelengths) have been designated as shown in the chart under band allocations. Sounds and other signals are converted to radiating waves for transmission, then converted back at the receiving end. See antenna, ionospheric wave, ground wave, radio, short wave.

Tools of the radio technicians around 1935±15 years. Radios were based upon simple circuits and vacuum tubes at the time. Later, transistors and VLSI technologies changed the design of radios and the ways in which they were repaired. [Library of Congress Theodor Horydczak Collection.]

Radio Link Protocol RLP, RLP1. A protocol standardized by the Telecommunications Industry Association (TIA), in the mid-1990s, using SDI, a formal specification language. RLP is a data link layer circuit-mode protocol for connecting a Mobile Terminal (MT) with a Mobile Base Station (MBS) to provide a stationary digital radio interface through a public switched telephone network (PSTN) to another data-compatible telephony device. This makes it useful for cellular data transmissions applications. Radio Technical Commission of Aeronautics RTCA, Inc. A private, not-for-profit corporation promoting consensus-based recommendations for communications, air traffic management, navigation, and surveillance issues. The RTCA was established in 1935. It now represents more than 270 trade, academic,

Two examples of mastheads from “Radiograms,” the historic name for telegrams from the Radio Corporation of America (RCA). The area below the header would list the date and source of the Radiogram followed by a text message, handwritten or typed, that usually had been decoded from Morse code. [RCA 1924 and 1926.]

Radio-Television News Directors Association RTNDA. An international nonprofit professional organization of network and local news executives in the broadcasting, cable, and multimedia industries. Established in 1946, the RTNDA promotes high standards of electronic journalism, the exchange of knowledge among members, public understanding

of the profession, and journalistic freedom. It sponsors an annual international conference for professionals in the news industry. http://www.rtnda.org/ Radio-Television News Directors Foundation RTNDF. Affiliated with the Radio-Television News Directors Association, the foundation promotes excellence in electronic journalism through research and educational programs for news professionals and students of journalism. The work of the Foundation is supported by other foundations, corporations, and RTNDA members. Research results of interest are posted or summarized on the RTNDA Web site. radiogram 1. A telegram sent through radiotelegraphy, also called “radiograph.” See telegram. 2. Combined radio receiver and phonograph. radiometeorograph See radiosonde. radiophone A device that transmits sound through radio waves. Although the term is less common, radiophones are everywhere; they have more individual names now due to their specialization (cordless phones, cell phones, etc.). radiosonde, radiometeorograph A miniature, automatic radio transmitter usually sent aloft on an aircraft or meteorological balloon, to transmit back meteorological information, such as temperature, humidity, pressure, etc. radiotelegraphy Transmission of telegraph signals through radio waves. The carrier wave was modulated to carry Morse code. The two main types were continuous-wave (CW), in which the carrier wave was interrupted to form the coded symbols, and interrupted continuous-wave (ICW), in which the carrier was modulated at a fixed frequency. radiotelephony The art and science of communicating through radio waves, often by means of various types of radiophones. RADIR random access document indexing and retrieval. RADIUS Protocol Remote Authentication Dial In User Service. A client/server network protocol for carrying authentication, authorization, and configuration information between a Network Access Server (NAS) (a client), desiring to authenticate its links, and a shared authentication server. RADIUS was submitted as a Standards Track RFC by Rigney et al. in June 2000. A RADIUS client passes user information to designated RADIUS servers and acts upon the responses. The server receives connection requests and authenticates the user, returning all configuration information needed for clients to deliver services to the user. A RADIUS server may acts as a proxy client to other servers. Authentication transactions are handled as “shared secrets” that are not transmitted over the network. Any transmitted user passwords are encrypted and RADIUS can work with a variety of authentication schemes (e.g., CHAP). The officially assigned port number for RADIUS messages has been changed from 1645 to 1812. See RFC 2865, which obsoletes RFC 2138. See RFC 2868 for RADIUS support for compulsory tunneling and RFC 2869 for RADIUS

extensions. RADIUS Accounting Protocol An administrative client/server protocol used in conjunction with RADIUS Authentication and Authorization services to deliver accounting information from a Network Access Server (NAS) to a RADIUS accounting server. The RADIUS accounting server receives an accounting request associated with a database of users of a modem pool, for example. It returns an acknowledgment of the user request. The RADIUS Accounting server may act as a proxy client to other types of accounting servers, as well. RADIUS Accounting was submitted as an Informational RFC by C. Rigney in June 2000. The officially assigned port number for RADIUS Accounting has been changed from 1646 to 1813. See RFC 2866, which obsoletes RFC 2139. See RFC 2867 for modifications for Tunnel Protocol support. See RADIUS Protocol. RADL radio laboratory. 2. See Reticular Agent Definition Language. radome A radar “dome,” a housing around a radar antenna which protects it without interfering with the signals. Radomes are especially important in radar antennas exposed to the elements, as in an airplane. RADSL See Rate Adaptive Digital Subscriber Line. RAF Royal Air Force. ragged In desktop publishing, an uneven margin, usually on the right side of the line. This occurs when proportional text is not justified (lined up). Ragged text is generally easier to read than double-justified text, particularly if the column widths are somewhat narrow. RAI remote alarm indication. RAID See redundant array of inexpensive disks. RAIN See redundant array of independent netports. RAIS redundant array of inexpensive systems. raised floor distribution A type of structure designed to accommodate a horizontal distribution frame for the attachment and management of wiring installations. It is typically designed so that the floor covering can be pulled aside or lifted to gain access for changes or additions. See distribution frame. RAM See random access memory. RAM disk An area of chip memory allocated and managed as though it were a disk drive. Unlike a disk drive, RAM is volatile; it requires a continuous source of power to retain its information and will lose the stored data if the system is turned off. A RAM disk is a means of disk caching that was popular when many systems had only floppy drives and no hard drives. It provided a fast way to access data without doing disk seeks or swapping out disks. RAM disks are now less prevalent. RAM Mobile Data An open architecture, nationwide commercial data communications service offered by Ericsson, BellSouth, and RAM Broadcasting. It is similar to ARDIS, a packet data service offered by Motorola. Base stations are used for relaying messages to users or to other stations.

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RAMAC Random Access Memory Accounting Machine. A historic large-scale computing machine announced by IBM, in 1956, for plant automation accounting and data processing applications. It included magnetic disk memory with a capacity of 5 million digits. Results of computations were recorded on punch cards. Over 1000 RAMACs were built before production was discontinued in 1961. RAMbus random access memory bus. See bus, random access memory. RAMDAC random access memory digital-to-analog converter. A graphics adapter display circuit which converts the computer digital information for representing the screen image into analog signals that a cathode-ray tube (CRT) display monitor can use. Ramsden, Jesse (1735-1800) An English instrument maker and engraver who invented micrometers, a pyrometer and a new type of eyeglasses and authored a description of a new “universal equatoreal.” He is credited with furthering the technology of the Cassegrain telescope devised 100 years earlier by Guillaume Cassegrain. Ramsden was elected to the Royal Society in 1786 and received the Copley Medal in 1795. RAND 1. random. 2. rural area network design. random access memory RAM. A type of computer memory in which data in any part of memory can be accessed in any order, that is, it is not restricted to reading and writing data sequentially as in serial data, tapes, etc. RAM is a very fast access device almost universally incorporated into computing systems for use by applications for frequent operations or those that must be executed quickly. In the mid-1970s, microcomputers typically had 4 Kbytes RAM and the price per kilobyte was about $100. Since then, the amount of memory installed in microcomputers has increased as prices have decreased. While there have been some interim fluctuations in prices, they have dropped dramatically as installed quantities have increased, as illustrated in this summary of the quantity/price changes over two decades. Time Period

Typical Quantity

mid 1970s late 1970s early 1980s 1983-1984 1985-1986 late 1980s early 1990s mid 1990s early 1998 late 1998 late 2000 late 2001

4 Kbytes 8 Kbytes 128 Kbytes 256 Kbytes 1 Mbyte 4 to 8 Mbytes 8 Mbytes 8 to 16 Mbytes 16 to 32 Mbytes 32 to 64 Mbytes 32 to 128 Mbytes 128 Mbytes +

Approx. Price/Mbyte $100,000 $2000 $1000 $700 $700 $400 $250 $200 $4 $1 $0.50 $0.10

random access storage RAS. A variety of types of memory and storage drives (e.g., hard disk drives) that enable data to be randomly accessed rather than sequentially accessed. These tend to be faster and more convenient than sequential access storage such as older tape drives. See random access memory. random early detection (RED) An active router queue mechanism for detecting incipient congestion on a network through a number of congestion indicators. RED drops packets probabilistically rather than when the buffer overflows, with the probability increasing as the queue size increases. Signals from RED may indicate persistent congestion, information that is useful for network management. RED can help control the average size of a queue on a system that experiences occasional transmissions bursts and thus reduces the chance of data loss. The maximum probability of a router packet being marked is set with the maximum drop rate. The random nature of RED reduces the tendency of synchronized processes to lock up when congestion is detected. Dropped packets have traditionally been used as a congestion indicator, but with RED, packets may be dropped before a queue overflows and thus may not always be the best indicator of congestion for security purposes. RED also may not be the best mechanism for effectively handling a very large number of very tiny transmissions. See explicit congestion notification. random number generator A device or algorithm intended to produce a truly random number or one that is at least difficult to predict. This is not as easy as it might seem, especially in computing devices that operate on rule- and clock-based principles. Their consistent modes of operation may cause them to generate the same random number, or the same pattern of random numbers, each time a random number generator is invoked. This is why most random number generators associated with computers are considered to generate pseudorandom numbers. Sometimes the “randomness” of the number is at the whim of a software developer who has written or compiled a random number-generating routine. Many computer operating system-level or machinelevel random number generators will fetch the same number the first time they are invoked and some will generate the same (or nearly the same) sequence of random numbers the first time they are invoked after a machine has been restarted or reset. Some random numbers are simply extracted from a list. To overcome some of the problems of generating an unpredictable or “true” random number, programmers have tried several strategies based on looking at a changing timer or piece of data unconnected with the regular operation of a system. Various input operations on the part of the user, or processes associated with another application on the system, are sometimes sampled to obtain an unpredicted value. Scientists have investigated the use of radioactive decay and radio waves for generating a random value or seed. There are even semiconductor-based random

number generating devices based on amplifying and sampling electronic noise. In 1998, Matsumoto and Nishimura described a 623dimensionally equidistributed uniform pseudorandom number generator that they called Mersenne Twister. This is a fast, efficient algorithm with a longer period than other generators. The source code is available online in C and Java. DIEHARD is a suite of programs for testing random number generators developed by G. Gasram, with support from the National Science Foundation. Source code in C is available for several platforms. With the growth of distributed networks like the Internet, it becomes possible to go outside the local system to find another system or timing device from which to fetch a number to use as a random value or a seed for generating a random number on the local system. There is even a site called www.random.org that provides a random number service for Web users. Random numbers are not just intellectual oddities. They are used in a wide variety of practical applications, including fundamental research, gaming theory and applications, gambling systems, statistical studies, and software/hardware systems testing. They are especially important for generating encryption keys and cryptologic algorithms for securing data and digital voice communications. See encryption. range 1. The extent, distance, or scope represented or traversed. 2. In a Global Positioning System (GPS), a fixed distance between two points, such as the distance between a GPS receiver and a satellite. 3. In mobile communications, the maximum distance of a transmission sufficiently clear to be useful. RAO radio astronomy observatory. RAP See Route Access Protocol. Rapid City IP switch See Accelar routing switch. Rapid Transport Protocol RTP. An end-to-end, full duplex, high-speed, connection-oriented transport connection protocol. Flow control is adaptive ratebased (ARB) at the endpoints, and error recovery is handled via selective retransmission. RTP can be used to transport Systems Network Architecture (SNA) session traffic, for example. RAR 1. An efficient data compression program developed by Eugene Roshal as shareware for DOS/ Windows-based systems. Files are just a little smaller than those generated by PKZIP and can be made selfextracting. UnRAR utilities are also available for the Macintosh. See Java Archive, LHarc, PKZIP. 2. return address register, RA register. A programming register or data compartment (as might be found in a stack, for example) for storing and accessing return address information. Depending upon the architecture, other registers associated with the RA register typically contain variables, parameters, etc. RARE See Réseaux Associés pour la Recherche Européenne. rare earth Some rare earth elements are commonly used as doping agents which can aid in the propagation of signals when added to transmissions media, such as optical fiber, during manufacture. Rare earth

doping is also being applied toward the design and manufacture of electrically pumped lasers that employ electronic circuitry. Erbium, Gadolinium, Europium, and Samarium are examples of rare earth elements. rare earth doping A means of using small amounts of rare earth substances to alter the transmission-carrying capacity of a medium such as a fiber optic waveguide. Doping allows a signal to be amplified by the stimulation of the rare earth substances, thus increasing the transmissions capability and the distance that the signal can transmit. Since fiber optic cable is not a long-distance carrier in the same sense as other media, anything which increases the distance is a great boon to fiber cable manufacture. Transoceanic cable applications can particularly benefit from this technology. Erbium is one of the rare earths used in this process; Samarium is another, used to dope lasers. See doping. RARP See Reverse Address Resolution Protocol. RAS 1. See random access storage. 2. RAS. The nickname for Sun Microsystems raster-format files. The file extension .ras may be used to distinguish these files. See raster. 3. See remote access server. 4. Royal Astronomy Society. 5. Russian Academy of Sciences. RASC 1. See Radio Amateur Satellite Corporation. 2. Royal Astronomy Society of Canada. raser acronym radio amplification by stimulated emission of radiation. raster A sequence of adjacent scanning lines on a cathode-ray tube (CRT) displayed quickly enough and closely enough together that they are perceived as a fairly uniform coverage of the display surface of the tube. The full coverage of the screen is called a frame. Most television broadcasts and computer monitor images start the raster at the top left corner, with each line sweeping horizontally left to right down the tube, and ending in the bottom right corner. There may be two sets of interleaved rasters displaying concurrently. Color raster systems typically employ three beams: red, green, and blue (RGB), the primary colors of light (the primary colors of pigment are red, yellow, and blue). Unlike a vector display, in which a straight line rendered at an angle appears reasonably straight (depending upon the resolution of the monitor), raster displays may have artifacts which cause the image to appear jagged or staircased. Antialiasing can perceptually decrease this effect. See antialiased, bitmap, interlaced, vector display, refresh. raster fill The filling in of spaces between raster lines on a CRT to provide an image that appears brighter or sharper. See raster. raster image processor RIP. A device to accelerate the process of data conversion, such as scan conversion on a monitor, or vector-to-raster conversion on a high-end printer. PostScript files, which are widely used in the printing industry, define vector-format files so that they can be output to a variety of types of devices at the highest quality possible for that device. Thus, service bureaus will take a PostScript file (as generated by a desktop publishing product such

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as PageMaker or FrameMaker) and RIP that file to their high-quality imaging device to create a rasterbased paper printout or a paper, asbestos, or metal printing plate. A printer device file is a file that includes information specific to the capabilities of a printer that is used in “rasterizing” an image. This can be used by a PostScript RIP, for example, to turn the vector-based instructions into objects and raster points that can be output to a printer. Adobe Acrobat distiller is a form of RIP that converts PostScript into high-quality PDF files (popular on the Internet). These files can then be readily viewed on a variety of monitors and, if desired, printed to a variety of printers. raster line A single line sweep (usually horizontal) of the electron beam on a cathode-ray tube. The time during which the image is rendered by exciting the phosphors on the inside front of the CRT. When the beam travels back to start the next raster line, it is suppressed in a process called blanking. See blanking, frame, raster. rastering, rasterizing The process by which an image is converted to data, usually as a stream of bits. Rastering is a common process in document transfer, and is often accompanied by compression and decompression of the data in order to minimize transmission time. RATCC radar air traffic control center. rate The cost per object unit or unit of time of an equipment lease or service. Phone services are typically billed at a flat rate per month with individual surcharges for connect time for long-distance calls or cellular calls. Internet Service Providers (ISPs) typically charge a flat rate per month, although some add surcharges for popular services like email, file storage, and Web access. Rate Adaptive Digital Subscriber Line RADSL. A means to optimize the throughput of data communications in a Digital Subscriber Line (DSL) service by adjusting the connection to compensate for variations in the line characteristics of the local loop. The desired bit rate may be initialized manually or automatically at startup or, if there is a way to monitor line conditions, may be adjusted as needed, based upon the performance characteristics of the line. This is in addition to the normal rate adaptation capabilities of the ADSL service. See chart under Digital Subscriber Line. See Asymmetric Digital Subscriber Line. rate averaging An economic method for providing uniform, simpler pricing options for equipment or services which normally might vary widely in their costs of installation and operation to different groups of consumers. For example, phone companies have fairly uniform rates over a wide variety of terrains, services, and population densities. Postal services also employ rate averaging; in other words, a letter to the next town requires the same postage as a letter to the most distant part of the country from the sender’s locality. rate decrease factor RDF. In ATM networking, an available bit rate (ABR) flow control service parameter which controls the decrease in the transmission

rate of cells when it is needed. See cell rate. rate increase factor RIF. In ATM networking, an available bit rate (ABR) flow control service parameter which controls the increase in the transmission rate on receiving an RM-cell. See cell rate. rate period In telephone service, a segment of time designated as a specific period in order to assign billing charges. Rate periods are determined by evaluation of phone call traffic volume, cultural customs, and time of day, and then usually established semipermanently so that subscribers become familiar with peak and off-peak rate periods. Rate periods vary from country to country. In the U.S., for example, the least expensive rate period on weekdays is from 23:00 to 08:00, and cheaper rate periods are available on weekends. Companies often schedule fax transmissions to be sent out automatically after midnight to take advantage of the cheaper rate period. See rate period specific. rate period specific When telephone calls which cross rate periods are billed at a higher or lower rate when the period changes, they are called rate period specific. International calls originating in the U.S. are usually not rate period specific, and the call is billed according to the rate period during which it was initiated. See rate period. Rate Quote System A computerized telephone rate/ quote system which can be accessed by TSPS operators. rated voltage A designation of the voltage at which an electrical component is set to operate, or, if put in a variable voltage environment, the safest maximum voltage at which it can be used for extended periods without risk of hazard or component burnout. RATP See Reliable Asynchronous Transfer Protocol. rat’s nest Mess; poor configuration; snarled, complicated arrangement of wires, machines, processes, or code statements. RATS Radio Amateur Telecommunications Society. RATS broadcasts to a Java-enabled site on the Internet on a 145.790 MHz channel. RaW read after write. RAX See rural automatic exchange. RAY See Rayshade. RAYDAC Raytheon Digital Automatic Computer. A historic large-scale computer manufactured by Raytheon and named in the same tradition as the ENIAC. The RAYDAC began operations in 1953. See ENIAC, JOHNNIAC, UNIVAC. Rayleigh disc An instrument for the fundamental measurement of particle velocity by means of acoustical radiometry. Rayleigh fading Fading, or loss of signal strength, as a result of interaction with the various objects or particles which are part of the environment of the transmission. This phenomenon is often found in mobile communications in which the interaction of the radio signals with the surrounding terrain causes signal fading. A number of techniques are being developed to reduce the incidence of fading. For example, in systems where long delays are acceptable,

fade can be reduced by interleaving. Named after J. W. Strutt (Lord Rayleigh). Rayleigh scattering Scattering of radiant waves by contact or interaction with minute suspended particles such as dust or moisture, or by impurities in a transmissions medium such as fiber optic cable. Named after J. W. Strutt (Lord Rayleigh). Rayleigh, Lord (1842-1919) John William Strutt, an English physicist and mathematician who made fundamental mathematical contributions to the field of physics, including atomic physics, acoustics, and optics. In 1870, he published On the Light from the Sky – Its Polarization and Colour, which presented his ideas and calculations based on observations of the scattering of light and the relationship of the scattered radiation to wavelengths. In 1904 he was awarded a Nobel Prize for his discovery of argon. Rayleigh scattering is named after him. RAYNET See Radio Amateur Emergency Network. Rayshade A native scene description language used with the Rayshade 3D raytracing software. Rayshade files may be distinguished by a .ray file extension. RB 1. See radar beacon. 2. reverse battery. RBBS remote bulletin board system. See bulletin board system. RBOC See Regional Bell Operating Company. RBS See robbed-bit signaling. RC6 A block cipher encryption algorithm developed by RSA Security Inc. that was selected as a finalist when entered as a submission to the U.S. Federal Advanced Encryption Standard. RC6 was jointly developed by Ron Rivest (originator of the MD series message delivery algorithms), Matt Robshaw, Ray Signey, and Yiqun Lisa Yin of RSA Laboratories and was originally specified in 1998. It is the evolutionary descendent of the RC5 block cipher, which is based upon the concept of data-dependent rotations. See Rijndael. RCA 1. remote control access. 2. See Radio Corporation of America. 3. root cause analysis. RCA connectors A basic electrical connection format for cables carrying audio/visual and sometimes data signals. The RCA connector is a simple, pegshaped jack or plug commonly used for single-signal cables (though they are sometimes also attached to the end of coaxial cables, with only one of the two coaxial conductors actively transmitting through the RCA end). RCA connectors are widely used in the audio and video broadcast and recording industries to interconnect components such as audio components, VCRs, DVD players, camcorders, switchers, and more. RCA connectors depend upon friction to stay in place, which means they are easy to plug and unplug, but should not be used for connections where a secure connection is vital or where there is tension against the connection (BNC connectors work better in these circumstances). RCAF Royal Canadian Air Force. RCC 1. See Radio Common Carrier. 2. reduced complexity computing. 3. remote control center/circuit. RCF 1. See Radio Control Function. 2. See Remote Call Forwarding. 3. remote control facility.

RCL runtime control library. RCM remote carrier module. RCP remote control panel.

RCA-jack cables are frequently combined in one cable for convenience (the signals run on separate wires), with the jacks color-coded (yellow–video, red–audio mono/combined or audio right, white–audio left) to help consumers interconnect the correct plugs. Three common examples include A. video, audio–mono B. audio left, audio right C. audio left, video, audio right.

There are many adapters available to enable RCA cables and components to connect with other components (headphones, portable recorders, etc.). Some common adapters include A. gender bender or extender for adding an extra length of cable B. RCA to mini (ca. 1/16-in.) audio mono C. RCA to ca. 1/8-in. audio stereo D. RCA to ca. 1/8-in. audio mono E. RCA to audio mono female F. RCA splitter/joiner to split a single signal out to two receivers or to join two signals into one.

RCS 1. radar cross-section. 2. See remote control system. 3. See revision control system. RCU remote concentration unit. An off-site facility or device in which multiple devices/services of the same basic type are aggregated and handled together within one basic management device housing. Telecommunications services (such as Internet access or cable TV) and electrical power distribution are two examples of RCU applications. RD See routing domain. RDB 1. receive data buffer. 2. remote database. RDF 1. radio direction finding. In radar, a British term for a tracking system based on locating the source of unidentified or foreign radio signals. 2. See rate decrease factor. rdist remote file distribution program. A program to distribute and maintain file copies on multiple hosts on a network. See DHCP. RDP 1. radar data processing. 2. rapid development program. 3. See Reliable Data Protocol.

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RDT 1. recall dial tone. 2. remote digital terminal. RDY ready. RE radio emergency. REAC Reeves Electronic Analogue Computer. A historic large-scale analog computer series first introduced in 1948 by the Reeves Instrument Corporation. One of the selling points of REAC computers was the “patchbay system” for patching interconnections. The Aeronautical Computer Laboratory (ACL) was among the first organizations to purchase REAC computers. Documents about this system form part of the Marvin L. Stein Papers collection at the Charles Babbage Institute and are also included in the National Museum of American History Oral History Collection. read A command commonly used in software application menus to provide the user with the ability to load data from permanent or semipermanent storage such as a floppy diskette, hard drive, cartridge drive, tape, RAM disk, or other medium. Files on a drive can be set with protections to be read only, or read/ write, or write only so that they can’t be read. Similarly a disk can usually be set to write-enabled or write-protected mode. Most optical storage media are read only, and cannot be rewritten or written without special, more expensive devices than are used by most consumers. read only memory ROM. A nonvolatile, randomaccess data storage unit which is preconfigurable, and not changeable by the user by normal means. ROM chips are commonly used for kernel level operating instructions or other information for the lowlevel functioning of a system which needs to be quickly accessed and transparent to the user. See CPU, RAM, PROM, EPROM, kernel. read-while-write RWW. A capability of some data storage devices to verify written data in realtime. This can be accomplished by executing code in one array while data are stored in another. In March 2000, Toshiba Corporation announced that they had developed the first 64-Mbyte read-while-write NOR flash memory device for use in various types of wireless, handheld consumer devices, and set-top boxes. See linear tape open. Realtime Transport Protocol RTP. A packet-oriented data delivery services protocol for end-to-end services to support applications transmitting realtime data such as Interactive audio/video applications over unicast and multicast networks. RTP provides time stamping, rate control and source/payload identification as augmented by the Realtime Transport Control Protocol (RTCP) to enable the monitoring of data delivery in a scalable manner. RTP and RTCP are independent of the underlying network and transport layers and may be integrated into the processing of an application rather than implemented as a separate layer. RTP was submitted as a Standards Track RFC by Schulzrinne et al. in January 1996. See RFC 1889. Real Time Markup Language RTML. A trademarked, proprietary set of extensions to the Hypertext Markup Language (HTML) for specifying the inclusion of streaming textual data on HTML-based

Web pages using RTTP data as a source. Thus, live, streaming text data can be readily incorporated into a Web page. This is of interest to vendors of realtime services and information such as stock quotes, news, or racing results. RTML is a product of Caplin Systems Ltd. based on Dynamic HTML (DHTML) combined with Java 1.1 or higher. Once it is installed, the user need not worry about programming any Java or other language. All that is required, once the streaming engine is installed, is to add a <SCRIPT> tag with optional attributes to the HTML pages. Newer browsers are required to view the streaming text messages. The software will alert the user if the browser is not compatible with the RTML feed. Real Time Streaming Protocol RTSP. An extensible, application-level protocol for delivery control of realtime data. RTSP enables the on-demand delivery of multimedia streams delivered, for example, by service delivery protocols such as Rapid Transit Protocol. Sources of data may include stored or live streaming data feeds. The protocol supports multiple data delivery sessions. RTSP was submitted as a Standards Track RFC by Schulzrinne et al. in April 1998. See Rapid Transit Protocol. See RFC 2326. real world A phrase to describe the application or testing of products or services in a real world environment, in other words, in the end population or facility for which the product or service is intended. Thus, a real world test of a new telephone might be to install it in a telemarketing firm. A real world test of a new computer might be to put it into a classroom or business. Real world testing is sadly lacking in the software industry. The pressure to get products to market tends to cause software companies to release a product after it has been tested in-house and through beta testers, but not by actual customers. This can have disastrous consequences as real world customers will always use the product in ways that cannot be anticipated by programmers and beta testers. RealAudio A commercial on-demand, multiplatform, realtime audio player for multimedia-capable computers from Progressive Networks. The RealAudio format is widely supported on the Web and may be played through a Web browser plugin or launched separately (on multitasking systems). Earlier versions of the software (e.g., version 2.0) supported monophonic sound designed for the 14.4 and 28.8 kbps transmission speeds typical of dialup network connections at the time. Subsequent versions are being updated to support higher-bandwidth connections as well. RealAudio files typically use the .ra file extension. realtime The term realtime is used somewhat differently by two groups of people: (1) marketing personnel and users and (2) technical systems designers and operators. First, a more general description of realtime. Realtime is a description of computer processes that occur at a speed which corresponds with human perception of the speed of events in “real life,” and in immediate response to requests. In other words, a ray tracing program that takes two hours to render and

display a frame of an animation is not realtime, as there is a delay during which the viewer must wait for the image to be constructed and displayed. In contrast, a fast action video game, in which the motions are displayed at 20 or 30 frames per second so that they are perceived as natural motion, and in which the joystick, mouse, or other inputs from the user have immediate effect upon the game, is considered to be a realtime game. Realtime flight simulators are used to train pilots, and realtime rendering programs exist on some fast, high-end platforms. In telephony, realtime processing involves handling calls as they are received. If callers are put on hold or experience delays in automated menu processing systems, the system is not providing realtime service. Realtime effects and processing, especially if they involve graphics, typically require fast, wide data buses, fast CPUs, and efficient mathematical algorithms for handling input, calculations, and display. In spite of the resources needed, humans seem to have a compelling interest in creating realtime scenarios and striving for real and fantasy simulations that mimic or outstrip the pace of life. This creates economic incentives for creating realtime simulations, especially in the entertainment industry, with audiences eager for these scenarios. Indeed, many of the advances in computer technology have been pioneered, fueled, and financed by the games industry. In a more technical systems implementation sense, realtime occurs in a computing system when computations are processed not only as expected, and with logical correctness, but also within certain predetermined or expected timing frames, and with a certain guaranteed minimum level of usefulness of the service. In this sense of the word, speed is not so much the issue, as is the appropriateness of the response time to the task at hand. Some realtime systems rely on sensor and other feedback mechanisms, and may be used not only in consumer computing operations, but also in industrial robotics or remote sensing applications. Realtime functionality is likely to be important in future space probes and the vehicles that deploy them, as well as in intelligent vehicle autonavigation systems. realtime capacity The capability of a system to handle calls, inputs, requests, or other stimuli as they are received. In configuring and tuning various types of networks, realtime capacity is one of the criteria many systems use as a reference point for smooth operations. realtime diagnostics Tests which allow measuring, diagnostic, or display instruments to monitor and report events as they are occurring. Most electrical instruments work in realtime, reporting circuit status at the moment the instrument is applied to the circuit. This is not so easily done with sophisticated computer systems, where it is difficult to track everything happening on the system at any one time. More often software “monitors” (statistical display programs) for specific processes are used, which include the representation of statistics for load, CPU speed and processes, congestion, failed packet ratios, quality of service (QoS), etc.

Realtime Transport Protocol RTP. An IETF data format that provides higher video priorities to facilitate realtime multimedia transport over Internet Protocol (IP). reassembly An important aspect of network communications in which an Internet Protocol (IP) datagram or other type of data unit, which has been split up at the source or en route and may have been transmitted in sections at different times and/or through different routes, is reassembled at the receiving end. The process of disassembly and reassembly allows packets to be transported through a large, dynamic network environment, like the Internet, which changes topologically in unpredictable ways. Reassembly and synchronization are also important in applications like videoconferencing, where more than one line may be used to transmit the various audio and video signals that make up the communication. reboot To cause a system to return to its initial operating status, as it was at the beginning of a system startup, usually without turning off the power. This typically clears memory, closes all applications and files, sets initial test sequences and starting parameters for timing, sound, video, etc. and reinitializes devices. The term is derived from “boot,” which comes from “bootstrapping.” If the power is turned off to reboot a system, it is called a cold boot. You should always count to 20 before flipping the power switch on again. Electronic components are sensitive to sudden power surges, and there is always some residual power in some of the chips that needs to drain off when electronics devices are turned off. Most reboots are warm boots, in which the power to the system is not interrupted. Rebooting is seldom necessary in stable operating systems, which can operate 24 hours per day for years without crashing, hanging, or fragmenting memory. However, some operating systems do not handle error conditions or memory management well and may hang, freeze, or crash, in which case a reboot may be necessary in order to continue using the system. receive-only device A device which can receive data but not send it. Technically, there are very few receive-only devices in computer networking, since most devices employ handshaking to negotiate a transmission. For example, a computer printer may seem to be a receive-only device, but a printer has to be able to tell the computer when it is ready to receive, when it is busy printing and can’t receive more data, and when it is available again for other jobs or other users on a network. This involves two-way communication. It may even signal the sender about its capabilities and configuration parameters. Most receive-only devices are passive devices or broadcasting devices such as simple PA speakers, buzzers, lights, etc. receiver 1. A device for receiving signals, impulses, or data transmissions. 2. A device which captures, and sometimes converts electromagnetic waves or signals into a form meaningful to humans. Receivers are often combined with tuners to specify the frequency desired, and amplifiers to increase the

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power of the signal. See telephone receiver. receiving perforator See reperforator. Recognized Private Operating Agency RPOA. An ITU-T designation for telephone companies providing internetworking services. Recommended Standard 232 See RS-232 for an entry and accompanying chart of Recommended Standards. RECON reconnaissance. reconnaissance A preliminary or exploratory survey to gain information or data that can potentially be analyzed to yield information (it’s often difficult to know in advance what data might later be useful or significant). Reconnaissance and surveillance are closely related activities. Reconnaissance is distinguished from surveillance in that surveillance is keeping watch over or observing someone, something, or some activities or phenomena. Reconnaissance is often used to support surveillance activities. Surveillance may also be used to obtain some of the data collected in reconnaissance activities. Typing a few exploratory passwords into a computer system is a reconnaissance activity intended to see if it would be easy to breach a secure computer system. Using a computer to remotely view a scene captured by a video camera is an example of a surveillance activity that may also be part of a larger reconnaissance operation. Recording Industry Association of America RIAA. A national trade organization representing the recording industry. The organization supports and promotes the protection of intellectual property rights and business prosperity of its members who collectively produce the vast majority of commercial sound recordings in the trade. The RIAA became prominent in the media when it opposed the alleged distribution of its members’ copyright materials by unauthorized users through the Napster Web site. In October 2000, the RIAA announced that it was going to develop a globally standardized system for identifying digital sound files in order for the copyright owner of the files to be able to track their use and to collect any royalties rightfully due for the materials. This was intended to enable the distribution of digital editions of the recordings quickly and easily over the Internet without jeopardizing the economic viability of the people creating and vending the music. http://www.riaa.com/ rectification 1. A condition in which current flowing through a material or circuit in one direction encounters greater resistance than current flowing through in the opposite direction. 2. The one-directional processing of an alternating current (AC). rectifier 1. A material or circuit that offers greater resistance to an electrical current flowing in one direction than in its opposite direction. 2. A device for converting alternating current (AC) to direct current (DC). Rectifiers are commonly used on power transformers for electronics devices with power requirements different from the power coming directly from an electrical source. Vacuum tubes were used as rectifiers in early radios, with selenium rectifiers

beginning to supersede them in the mid-1940s. recursion 1. Returning, moving back upon. 2. A repetitive succession of elements or operations that affects the preceding elements or operations in a like (although not necessarily identical) manner according to a finite rule or formula. Recursive algorithms often generate data or images with the characteristic of “self similarity,” with fractal display programs being a popular, visually appealing example. 3. See recursion. red alarm In telephone transmissions systems, a critical failure alert signal which occurs if an incoming signal is lost or corrupted. This is implemented in various T3, T1, or SONET network systems. Red Book 1. The original Compact Disc digital audio (CD-DA) specification, developed in the late 1970s and introduced in the early 1980s by Sony and Philips. Audio sectors, tracks, and channels are specified, along with other physical parameters. The format enabled up to 74 minutes of digital audio to be recorded at a sampling rate of 44.1 KHz, a rate that is sufficiently good to support the recording of classical music. The Red Book was followed, in the mid1980s, by the Yellow Book, which specified CDROM parameters. See Yellow Book. 2. In telephony, books in the ITU-T (formerly CCITT) 1984 series of recommendations. 3. The Adobe PostScript Language Reference manual. Red Box An environment for running Windows applications under Apple’s Rhapsody on Intel-based computers and possibly on PowerPC-based computers, generally analogous to the Blue Box environment for running legacy Mac operating systems under Rhapsody. This would make it possible to have full compatibility with Intel-based operating systems such as Microsoft Windows on Apple hardware. See Blue Box, Yellow Box. red gun In a color cathode-ray tube (CRT), using a red-green-blue (RGB) system, the electron gun which is specifically aimed to excite the red phosphors on the inside coated surface of the front of the tube. Sometimes a shadow mask is used to increase the precision of this process, so the green and blue phosphors are not affected, resulting in a crisper color image. See shadow mask. red signal An alert or failure signal or “stop” indicator used in many industries and in association with many different types of devices, networks, and gauges. See yellow signal for a fuller explanation or red and yellow signals. red wire A color designation used by IBM to indicate wires used to establish a hardware patch to accommodate a code change. See blue wire, purple wire, yellow wire. Reduced Instruction Set Computing RISC. A type of programming and system architecture which uses a set of simpler instructions performing single, discrete functions to carry out an operation than would be used in a comparable operation by a Complex Instruction Set Computing (CISC) design. Most of the newer computers tend to incorporate RISC architectures, although not all support circuitry enables the

full capabilities of RISC architecture to be used. Unlike CISC commands, RISC commands are the same size, which means that less time is required for subsequent processing of the instructions, because individual evaluation of the commands for size and conversion to microcode is not required. When RISC software is compiled, it is evaluated to determine which operations are not dependent on the operation or results of others, and slates them for simultaneous execution. Due to the reduced instruction set and processing that takes place, the circuitry on RISC chips is simpler than on most CISC chips, resulting in a smaller physical size and, usually, lower heat output. Not all chips are strictly RISC or CISC. For example, in the Intel line of processors, the Pentium chips are a transitional architecture that maintains some downward compatibility with the earlier CISC architectures, while still incorporating some of the advantages of RISC architectures. The chips tend to be larger and hotter than straight RISC chips, but meet a market demand through a transition period. redundancy Replication, duplication, superfluity, repetition. Redundancy is important in computing because the loss of data, whether stored or in the process of transport, can have serious consequences to human safety, economics, or business transactions. See redundant array of inexpensive disks. redundant array of independent netports RAIN. ZNYX Network technology that provides a scalable, modular architecture for delivering high-performance, high-availability, customized intranet connectivity through clusters of network servers.

RAINswitch server switches were announced in 1997 to support RAIN implementation in Fast Ethernetworks. redundant array of inexpensive disks RAID. A data storage, retrieval, and protection system using multiple disk storage devices, a system commonly used in networks. RAID consists of multiple hard drive storage devices linked together to provide data mirroring or data striping and parity-checking across disks in order to record the information redundantly. Duplication or data mirroring is primarily a function of software, whereas parity-checking requires a controller and is associated more closely with hardware. Many RAID systems are SCSI-based. A basic low-end RAID center may consist of four drives, each with 2.1 Gbytes of storage, sometimes set up in a rack, talking through a centralized controller system, usually through a server. Although a certain amount of storage is inevitably lost due to duplication of data, the big advantage of RAID systems is that they provide pretty good protection against data loss if a drive goes down. There is less protection if several drives go down but, since this happens rarely and since companies are reluctant to back up data sufficiently often on systems like tape drives, the RAID alternative works well in practice. Many RAID systems are “hot-swappable” which means that an individual drive can be pulled out and replaced while the system is online, thus not necessitating a system shutdown or inconveniencing current users on the system. Specifications released in 1988 in the RAID paper proposed five levels. Since that time, changes and

Redundant Array of Inexpensive Disks (RAID) – Level Specifications in Brief Level

Notes

Level 0

Striping, no redundancy or error correction. This can provide faster access, but does not protect data from loss.

Level 1

Disk mirroring. Complete redundancy. Provides data protection.

Level 2

Byte striping, dedicates at least one drive for parity information. Uses Thinking Machines, Inc.’s proprietary setup, which is not commonly used.

Level 3

Generally used instead of level 2. Block striping will improve performance if data are written in large blocks and simultaneous reads are used. Distributed parity information (originally required a dedicated parity disk, a stipulation removed in 1994). In other words, when appropriately implemented, better performance and data protection can be achieved.

Level 4

Similar to level 3, but larger data blocks are striped across disks; each drive is not necessarily involved in each access.

Level 5

Block striping, parity information distributed across drives. At least three drives are required for a minimum implementation. Each drive is not necessarily involved in each access. Parity information is also striped across disks. Provides data protection and, in many cases, will improve performance. This is a popular implementation of RAID.

Level 6

Not consistently specified or implemented.

Level 7

Similar to level 4, with larger data blocks striped across disks. Uses Storage Technology, Inc.’s proprietary caching mechanism and operating system.

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enhancements have occurred; the levels are not cut and dry since configuring various parameters, such as stripe size, creates overlapping characteristics between the different levels. Hybrid systems also exist. Generally, however, to provide an introductory understanding, the RAID levels can be summarized as shown in the RAID Levels chart. In addition to redundancy and parity checking, a RAID system may have some intelligent monitoring incorporated into the system, which does periodic checks and analysis and reports anomalies to the controller. The controller can then signal a warning which allows the device administrator to check for potential problems, or swap out a drive before it fails. See dynamic sector repair, SMART. re-engineer To step back from a system or process, take a new look at it, and redesign it, sometimes from the ground up, with the intention of making it more efficient and cost effective. Software often has to be re-engineered, as legacy systems tend to be slower and less efficient over time, due in part to the way they are upgraded and, in part, because of technological improvements and changes in hardware which are accommodated in a variety of ways. Market pressures also cause many software programs to be released before their time, in which case, they may be re-engineered before the next release. Work environments in companies that are growing or downsizing quickly often must be re-engineered as the ways of organizing facilities and staff appropriate to a small company are not necessarily appropriate to a large company. reed relay switch A type of electronic telephone switch developed in the 1960s. Reed relay switches began to supersede crossbar switches, which were prevalent at the time, and some of the step-by-step switches still in use. Electronic switches opened up possibilities for many new types of caller services, such as Caller ID, Call Waiting, etc. reel-to-reel tape Magnetic recording tape wound onto separate round reels which are usually about 4-in. to 8-in. in diameter. Although most tape is now distributed on cassettes rather than reels, reel-to-reel is still used in some professional recording studios, especially if eight or 16 tracks are required for sound mixing and dubbing. Gradually these reel-to-reel sound recorders are being superseded by digital recording media. See cassette tape. Reeves, Alex H. A British engineer who is one of the significant pioneers of pulse code modulation (PCM) or, as he calls it, “coded step modulation.” PCM is a fundamental quantization system used in audio recording and transmission technologies. Reeves conceived the idea while working at the International Telephone and Telegraph Corporation (ITT) in Paris in 1937 and received several patents for the technology between 1937 and 1942. Reeves recognized the potential for PCM to counteract interference on transmitted speech communications. In 1965, Reeves authored The Past, Present and Future of PCM. See pulse code modulation. reference clock A clock considered very accurate or stable, which is used as a reference for other clocks

or processes, such as computer processes. Quartz crystal clocks are considered very accurate due to their vibrational properties and are often used in computers and watches. The speeds of various computer processes are described in clock cycles. Atomic clocks are used to establish Coordinated Universal Time and in satellite positioning systems which require accurate clock references. In multimedia editing environments, a reference clock is used to provide “house sync,” that is, longterm synchronization of various audio or other signals, which resolve to the reference clock rather than to the time code signal. See atomic clock, chase trigger, Coordinated Universal Time, quartz crystal, time code. reference vector equalization RVE. A derivative of transparent tone in band (TTIB) modulation and a basic aspect of linear modulation systems, RVE utilizes equalization for linear amplitude and phase correction to improve transmissions. It is suitable for trunked narrowband mobile radio systems, for example. RVE enables a digital radio to equalize a transmission signal at the receiver increasing potential schemes for high bit-rate densities. See linear modulation, tone in band. Referral Whois See RWhois. reflector/director elements On antennas, two or more protruberances from the main rod that are usually narrow and regularly spaced in an array. Reflector and director rods help improve gain and directivity. See Yagi-Uda antenna. refresh rate, scan rate The rate per unit of time at which information or an image is recreated in order for it to remain current or visible. This phrase is frequently applied to broadcast and computer display technologies, especially cathode-ray tube (CRT) displays in which the action of electron beams on the phosphors is very limited and must be reinitiated (refreshed) in order for the image to continue to be visible. Refresh is a general concept which applies to many different types of situations in computing, from individual phosphor refreshes to graphical user interface element refreshes. The refresh rates of the phosphors on the inside coating at the front of a cathode-ray tube will affect the clarity and amount of flicker seen on the screen. Monochrome or gray scale monitors have longer persistence; that is, the image from the excited phosphors is visible longer, and thus do not need to be refreshed as often as color images. Refresh of the entire CRT image is described as the number of times per second the frame is redrawn. Refresh rates slower than about 20 to 40 frames per second are perceived as flickering to the human eye, especially if the image involves fast action. Still or slow-moving images do not need to be refreshed as often. The refresh rate of a computer program image is a combination of operating system and applications programming, and is not simply dependent on the hardware attributes of the system. In order to optimize speed on a computer display, the OS or programmer may choose to refresh only a section which

has just been manipulated or changed. If the software does not keep track of what is transpiring on the screen or if several processes are active at once, it may seem that the display is slow to update or refresh a new window, gadget, or element drawn in a paint program. In general, quicker refreshes are desired over slower ones, but the cost of more computing power and faster hardware puts some economic constraints on the refresh rates of various systems.

refurbished equipment Used equipment that has been serviced and tested by a technician to bring it back to original operating condition. If further work is done and substantial numbers of parts replaced or upgraded, it may also be referred to as remanufactured equipment. Refurbished equipment, or refurbs, are usually cleaned up and made to appear new or nearly new. Refurbished items are typically sold at a discount of about 15 to 30% over the price of new ones. If the

Resolution of Various Computer-Related Peripheral Devices Device

Notes

Scanners

The resolution of scanning devices describes the smallest discernible or recordable unit into which the image can be digitally encoded, usually dots per inch (dpi). In most current scanners, this is an optical resolution of about 1200 to 2400 dpi; interpolated resolutions may be higher.

Printers

The resolution of printing devices is usually described in terms of dots per inch (dpi), with 300 to 800 dpi common, particularly in consumer laser and inkjet printers. Professional typesetting machines range from 1000 to 2700 dpi and require special papers, metal plates, or film to retain the very fine details.

Monitors

In common computer display devices, resolution is of two general kinds, based upon the rate of change possible in a repeating pattern of scanning lines or upon discrete points or vectors that are addressable on the screen. For example, the resolution of most consumer desktop cathode-ray monitors is described in terms of a line of horizontal dots of a particular size, designated by dot pitch. The size of individual dots is determined by a cathode beam (sometimes passing through a shadow mask) that excites a phosphor coating. Rasterbased monitors usually range from about .30 to .27 mm dot pitch, with lower numbers signifying smaller, finer dots, and thus higher resolution, because it is possible to fit more of them across a specified area. Some use a similar system based upon aperture grill, in which .26 is said to be perceptually about the same resolution as .28 dot pitch. The resolution in either case is really dependent on two factors: the size of the individual dots and the distance between them. In most cases, the smaller the dots and the closer they are positioned, the more that can be fit horizontally across the screen. Since most CRT display devices employ scanning to create a picture image as a “frame,” the vertical resolution is described in scan lines rather than in individual pixels, but since most computer monitors these days are addressable in terms of pixels within individual scan lines, vertical resolution may be described in the same terms as horizontal resolution. Common screen resolutions are 640 x 480, 800 x 600, 1024 x 768, 1280 x 768, 1024 x 1024, 1280 x 1024, 1150 x 786, 1600 x 1280, and others. Most current computer operating systems can display the higher resolutions, but the graphics display card that comes with the computer may only support the lower resolutions, and the monitor, if it is an RGB monitor, may not work with higher resolutions, which require faster refresh rates. To get the higher-resolution modes, it may be necessary to purchase a multisync monitor and a high resolution graphics card or, if the monitor already supports higher resolutions, to swap out the graphics card for one with more memory and higher processing speeds.

Rangers

The resolution of a ranging system that attempts to discern objects in three dimensions is expressed in terms of its ability to distinguish one object from another. This is difficult to express precisely, as color, movement, shape, and other factors affect this measurement. Nevertheless, ranging resolution can be used to distinguish high-end from low-end specialized systems.

Positioners

The resolution of positioning systems is a description of how small a unit of distance can be resolved, recorded, and reported by the system. For example, the resolution of the Global Positioning System (GPS) for civilians is lower than the resolution for military and other government use. See Global Positioning System.

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refurbished item comes with a good warranty and is the type of product that doesn’t wear out readily, like switch boxes, modems, peripheral cards, or motherboards, it may be worth it to buy a refurbished product. However, limited-life products like monitors and various types of printers, which are susceptible to mechanical wear and tear, should be considered only if the discount is significant. regenerate To restore, bring back to original condition, recreate, duplicate. In electronics, signal regeneration is an important issue. Transmissions typically suffer from loss and interference over distances, and any means that can be used to maintain a signal or regenerate parts or all of a signal experiencing loss or change in some form is usually desired. There are many physical and digital schemes for regenerating systems. In some digital systems, regeneration may involve putting a signal back into its original form at the receiving end. In a sense, single sideband transmissions are a type of regenerated transmission, since only a portion of the signal is sent. The opposite sideband and the carrier signal are mathematically constructed, and the original signal thus reconstructed at the receiving end. See regenerative repeater, relay, repeater, single sideband. regenerative repeater A type of repeater used in communications that are characterized by uniformity of length and signal to correct the timing of the signal and retransmit the cleaned-up impulses. These are common in older teletype communications. See repeater. Regional Bell Operating Company RBOC. One of a number of companies which were formed by the divestiture of AT&T, which originated from the original Bell Telephone Company through a long, colorful history of mergers and splits. In the mid-1980s Judge Harold Greene broke AT&T into seven RBOCs. For more detail, see divestiture, Consent Decree of 1982, Modified Final Judgment. register A repository for data, a storage area which may or may not also be used for data manipulation. There are many areas of telecommunications where registers are used. Many computer chip architectures have registers for holding information about to be moved or manipulated. Palette configurations for computer displays may be saved in color registers. Data modems have registers for setting various parameters, with Hayes AT command “S” registers common. Flags, configuration settings, etc. are stored in registers. registration marks, register marks In printing and desktop publishing, small marks, often resembling very fine targets, which are placed around an image to be printed in more than one run through the press, or in more than one color, in order to align the various layers so that they print perfectly on top of one another. Registration is especially important in process color printing, since the dots that make up the multiple colors will not create the correct patterns and the illusion of many colors, unless the alignment is nearly perfect. Note that there is no room for registration marks if the extents of an image reach the edge of the paper on which they are laid out.

When desktop publishing an 8.5 x 11-in. image with bleed, or with registration marks for color or multiple press passes, it is necessary to select a paper size larger than 8.5 x 11-in. (letter extra is a common setting) to provide room for registration and other printers’ marks. See crop marks.

By lining up registration marks, which resemble targets, color separations and other types of separate press runs can be “registered,” that is, lined up or composited with all the elements and colors in the right places.

Registration Number As part of the Federal Communication Commission’s (FCC’s) jurisdiction over equipment which may emit radiant waves that interfere with other equipment, appliances, radios, etc. There is a process of submission, evaluation, and certification which warrants that the equipment has passed FCC requirements. This Registration Number is not related to quality, suitability for a particular use, or other usability issues; it simply confirms that the equipment falls within acceptable emission standards. Reis, Johann Philip (1834-1874) A German inventor who did substantial pioneer investigations in transmitting tones and possibly also voice over wires. Reis accomplished this with various transmitters and other equipment that he developed and publicly demonstrated in Frankfurt to the Physical Society in 1861. No directly verifiable evidence indicates whether voice was transmitted at the 1861 demonstration, but Reis’ subsequent work indicates that he recognized the potential for voice communications and concentrated many of his efforts in that direction, eventually developing a telephone design that was not unlike telephones actually put into production in the United States some years later. Subsequent inventors, excited about the breakthrough, made improvements on Reis’s early crude mechanisms, while Reis himself continued to study and improve the technology until his early death in 1874. See telephone history. relay n. 1. A means of passing on signals, objects, or communications to another node after which they are further transmitted or transported. 2. An electromagnetic device in a circuit for providing automatic control, which is activated by varying electrical impulses. A relay is usually combined with switches to control when they open and close, and widely used to automate older telephone switching centers. Thus, it was important to design relays for durability, since they had to open and close circuits many millions of times. Because the relay is essentially a simple mechanism, it can be greatly varied by adjusting contact springs and windings, thus producing a large variety of types of relays. Multicontact relays were

developed in order for numerous switching contacts to operate simultaneously. See crossbar switch. Release to Pivot RTP. A number portability mechanism, similar to Query on Release (QoR), in which a telephone number that has been ported from a release switch returns the addressing information for routing a call (as opposed to the previous switch). If the number has been transferred, the information may be contained in the release switch or in an external database. See Query on Release. reliability An expression of the dependability of a system under actual conditions of use. See availability, mean time between failures (MTBF). Reliable Asynchronous Transfer Protocol RATP. A packet-based serial communications transfer protocol described by G. Finn in 1984. RATP is intended to facilitate reliable, easy-to-use communications between computers through public telephone circuits. Based on the ubiquitous RS-232 standard, RATP enabled full-duplex, point-to-point communication more simply than some of the other protocols at the time as well as some capabilities not found in others. RATP is now considered a historic protocol. See RFC 916. Reliable Data Protocol RDP. A data protocol for providing reliable packet-based data transport services such as remote loading and debugging. It is, in part, adapted from Transmission Control Protocol (TCP), and was submitted as an RFC by Velten et al. in 1984. RDP supports the bulk transfer of data for various monitoring and control applications, as needed, with a simpler set of functions than TCP. Version 2 was submitted by Partridge and Hinden in 1990 to address some problems discovered in testing in 1986 and 1987. It makes changes to the protocol header and corrects some minor errors. See RFC 793, RFC 908, RFC 1151. Reliable SAP Update Protocol RSUP. A bandwidthsaving protocol developed by Cisco Systems for propagating services information. RSUP enables routers to reliably transmit standard Novell SAP packets only when a change in advertised services is detected by the routers. Network information can be transported in conjunction with, or independently of, the Enhanced IGRP routing function for IPX. reluctance Opposition, or resistance in a magnetic circuit against the creation of magnetic flux. Similar to the concept of resistance in an electrical circuit. See resistance. Contrast with permeability. REM 1. remote equipment module. 2. See ring error monitor. remailer Any online electronic mail transit station which changes or prepends the header in such a way that the originating information is changed or obscured, or which intercepts mail and then forwards it on to its destination. Sometimes these remailers are LAN servers configured so that the header changes when incoming mail is served out to the local recipients. This is unfortunate in that the recipients cannot automatically reply to the sender and must manually type in the return email address in order to respond to their correspondents. This is not a recommended way of configuring a mail server and should only be

done when a specific reason warrants it. Remailers are sometimes used irresponsibly. Thousands of get-rich-quick and commercial products promoters use remailers to obscure the origin of their online postings because there is much legitimate opposition to unsolicited commercial messages on public forums and in private email. Anonymous remailers are mail transit points which deliberately obscure the identity of the poster in order to ensure his or her privacy. See anonymous remailer, spam. remanufactured equipment See refurbished equipment. remapping On a computer system, remapping is moving data, often in the form of blocks, arrays, or tables, from one area of storage to another. Memory remapping, address remapping, file location remapping, and keyboard remapping are some common examples. Remapping is sometimes used to double-buffer computer graphics screens – building a screen in a background while the current screen is viewed by the user and then displaying it by remapping the entire image to the video display area. It can improve the likelihood of fast, clean transitions. See frame buffer. remote access An important aspect of networking in which access to computing services, devices, and information can be gained through a remote device on the network, usually a computer terminal or phone line. On a phone line, remote access to an answering machine can enable a user to dial up the answering machine from a different phone, punch in some codes to see if there are messages available, retrieve those messages remotely, and even change the message on the answering machine through the phone line. Remote access does not imply the level of operations that can be accomplished, only that the device can be accessed in some basic way. Remote access terminals vary greatly in their ability to interact with a server or other user functions. For example, on a basic text-oriented “dumb terminal” connected to the main computer with a serial line, the user may only be able to execute simple text commands and won’t be able to display graphics or run sophisticated applications locally. On the other end of the spectrum, some systems provide full access to remote applications, especially if they are connected with a fast transmissions protocol over fiber. In other words, there may be a graphical database program available on the server that the user can run on a smart terminal as though the terminal was the main computer. Not all operating systems can do this. The X Window System is designed to provide this type of capability in conjunction with various Unix systems. It has also been upgraded to provide similar services over the Internet. See X Window System 11. remote access concentrator RAC. A network system for interconnecting numerous multiple remote telecommunications links to a local system such as a local area network (LAN). Businesses with wide area networks (WANs) and telecommunications

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providers make wide use of concentrators, as they aid in channeling and aggregating many types of equipment in order to serve broader needs such as large numbers of employees or telecommunications clients. High-performance concentrators may support several services, including access, switching, and routing. Commercial RACs are created for many purposes such as interconnecting multiple ISDN B-channel lines to LANs through Ethernet or multiple computer modems to T1/E1 networks. Multiple RACS can sometimes be attached to one access switch. Depending upon the protocols supported by a RAC, it may be connected indirectly or directly to the public switched telephone network (POTS). Many vendors promote a similar product called a remote access server (RAS), which is basically a lower-end version of a remote access concentrator (usually with fewer ports). Others refer to the operating software for a RAC as remote access server software. See remote access server. remote access control facility RACF. A facility dedicated to the provision and management of remote access transmissions. An Internet Services Provider is a type of RACF that provides multiple subscribers with remote access to Internet services. A telephone switching office is another type of RACF, providing access to multiple remote telephones to its local subscribers. Within a particular business, a remote access facility can be established as a management or security system to control, authorize, log, and secure data and physical resources (printers, modems, etc.) used by a variety of in-house or contract employees. IBM provides the commercially trademarked Remote Access Control Facility system, first introduced for mainframes in 1976. The system is promoted to businesses for the management and securing of valuable corporate data. RACF supports OS/390 and z/OS software systems. See remote access. remote access PBX A private branch telephone exchange which can be accessed from an outside line with appropriate authorization codes. Once logged on to the internal branch system, various features can be used such as voice mail messages, long-distance calls connected and billed through the PBX, etc. remote access server The software and generally also the hardware on which the server software runs for managing transmissions between remote and local devices. Remote access to the Internet and offsite printers, security monitors, and other networkable devices can be facilitated by a dedicated server, especially in situations where numerous people will access the service through limited resources (e.g., a limited number of modems). See remote access concentrator. Remote Authentication Dial In User Service See RADIUS. remote batch processing A means of submitting a computing job remotely to a processing system and receiving it back as or when the job is processed. This is rarely done at the consumer level, but it is still com-

mon for high-end mathematical calculations, scientific research, and other intensive computing applications which may require large amounts of computing time or more sophisticated computing resources. In the earlier days of computing, remote batch processing, especially with punch cards, was the only type of service available, and it could take hours or days to receive the results of a simple calculation. Remote Call Forwarding A service in which a phone number is located in the central office of one exchange and any calls made to that number are forwarded (essentially by internally making a second call) to a line in another exchange. This may be of value to businesses that want to maintain a local presence without the expense of a local office, so that customers can call a local number instead of longdistance. remote control n. A device to allow control of another device without making direct physical contact. The control of the device may be through indirect physical means (through a remote controller and cable), a network (computer-controlled vending machines in another part of a building), or various wireless methods (infrared, FM, audible sound control, etc.). Remote control of computers on a network can be done through various telecommunications products, specialized remote applications and file serving software, or through operating systems which support this capability. remote control access RCA. Access to restricted areas, rooms, or pieces of equipment through wired or wireless remote devices. Many environments and types of buildings control access through remote devices. Examples include remote garage door openers, key cards, parking barrier remotes, audio/video/ computer components with security feature remotes and home automation remotes. remote diagnostics Systems diagnostics which can be run from a remote location. It is common for higher-end routing and switching devices on a computer network to be controlled through software at a main administrative location. This software typically permits the running of test and diagnostic routines and may show graphical diagrams of problems or potential problems or bottlenecks. On phone systems, diagnostic checks can sometimes be carried out with devices that generate specific tones or signals, which can initiate processes at the other end of a phone line. remote file access RFA. A capability for accessing electronic files from a system/terminal separate from the file server. RFA may be at some distance from the file repository. The Internet provides a transmission link to millions of file repositories around the globe that can be accessed and downloaded by various Web browsers and file transfer utilities. See File Transfer Protocol, ftp, Gopher. Remote Imaging Protocol RIP. A protocol for facilitating the implementation of EGA-resolution color images and mouse control from a remote system. RIP was developed to overcome the limitations of text-based bulletin board system (BBS) com-

munications (in the days before the World Wide Web). Vector-based commands are sent and rendered through a point-to-point network connection. The system has some limitations but is an interesting solution to text-based remote terminal connections through dialup links. See Remote Imaging Protocol script language. Remote Imaging Protocol script language RIPscrip. A scripting tool from TeleGrafix Communications, Inc. for facilitating the development of graphical user interfaces for computer bulletin board systems (BBSs) supporting Remote Imaging Protocol (RIP). It is a 7-bit system to maintain compatibility with the many 7-bit communications systems common through dialup connections (e.g., X.25). RIPscrip works in conjunction with RIPaint and RIPterm for developing graphical interface screens and protocol needs. See Remote Imaging Protocol. remote job entry RJE. Generically, this is the entry of computer commands from a remote entry terminal, that is, a local terminal, for execution on a remote machine (e.g., a timeshared mainframe). This applies to individual job requests and to batch requests. The term has changed meaning somewhat as computers have become more common and less expensive. Historically, remote job entry was a batch request submitted on computer punch cards. The cards were punched at a card-punching terminal by the programmer, then physically handed together as a “job” to a computer operator. The operator queued the job with others that were pending and then inserted the card bundle into the computer’s card reader for execution. When the job was completed (or “crashed” due to errors), the operator would return the job cards to the programmer along with any relevant results (or error messages). These days, jobs are usually submitted electronically through software requests rather than physically through punch card stacks. See Remote Job Entry Protocol, remote programming. Remote Job Entry Protocol RJEP. RJEP was first submitted as an RFC by Chuck Holland in the early 1970s. This generated quite a bit of interest and was corrected and developed further in RFC 407 in 1972. Remote job entry is a means by which a user can execute a computer processing job at a location (e.g., a mainframe) other than the local computer (e.g., a remote terminal). The user can thus submit a job to another system acting as a job server, which would process the job and deliver the results to the remote terminal through a TELNET connection. File Transfer Protocol (FTP) served as the file transfer mechanism. RJEP enables connections to be established individually or may leave the connection open for multiple submissions. See File Transfer Protocol, remote job entry, RFC 360, RFC 407. Remote Mail Checking Protocol RMCP. This lowoverhead mail checking protocol was submitted as an experimental RFC by Dorner and Resnick in 1992. It provides a client/server-based mail checking service. A program on the client’s workstation uses RMCP to query a server to see if new email has been received for a specific user. It is suitable for use with

remote mail servers, such as those implementing Post Office Protocol (POP). The protocol is based on the User Datagram Protocol (UDP) port 50. Some authentication in the initial communication between client and server, at the cost of complexity. See RFC 1339. Remote Operations Service Element ROSE. An application layer service that provides the capability to perform interactive remote operations through a request/reply mode. ROSE is a generic information exchange technique which is not applicationspecific and not intended to define the operations it facilitates; this is left up to those implementing remote services. It is defined as ISO 9072-1, and as an X Series Recommendation by the ITU (X.219). See Abstract Syntax Notation One, X Series Recommendations. remote procedure call RPC. A means of making a request to a remote system so that it appears to the user as though the request is being fulfilled on the local machine. In other words, a user may open a word processing program and load in a file. The file may actually reside on a computer in another room or another city, but the user is unaware of any difference in using the file from the remote system or using a file from the local system as the RPC is transparent to the user. Another example would be the use of a terminal communications program which accesses a modem on another computer as though it were physically attached to the local machine. A number of conventions for making requests to a remote system, and fulfilling those requests, have been developed. The RPC standard is a system for defining the parameters of a remote communication. Remote Procedure Call Model RPC Model. Based on concepts of remote procedure calls (RPCs) in which the caller and called procedure are typically on physically separate systems exchanging data through a communications link, the RPC Model operates as a control mechanism functioning through the caller’s process and the server’s process. An RPC interface provides a set of remotely callable operations provided by the server and provides a means to manage server resources made available to the remote caller. As an example of one implementation, the caller sends a call message with parameters to the server process and holds for a reply. When a reply message is received, procedure results are extracted from the data and the caller resumes execution of local applications (or makes further calls). While the model does not exclude the possibility of concurrent processes on the part of the client and server, it is sometimes implemented with only one being active at a time. remote programming The capability whereby a system can be programmed from a remote location, either through a data network or phone lines, usually after input of appropriate authorization codes. Remote programming enables a field worker or telecommuter to administer a system without being physically present. In computing, remote programming is often done by BBS operators who want to

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check and manage their systems when out of town. By dialing their own BBSs and logging in as the Sysop, they can validate new users, check mail, configure the bulletin board, and accomplish various maintenance tasks through a phone connection. Remote programming is often implemented in highend corporate and industrial software programs. The software is set up with security mechanisms so an authorized programmer working for the software vendor can dial into the customer’s machine and do routine maintenance, software tune-ups, diagnostics, and configuration without having to travel to the customer’s site, and during nonbusiness hours, if needed. This type of service is usually provided through a separate service contract for a specified period, or is billed hourly, as needed. remote site A facilities or equipment location which is distant from the one presently occupied, or from which certain maintenance or administration tasks may be carried out. A sales representative with a laptop, a scientist with an intercom radio doing field research, and a computer terminal in an annex building are remote sites often directly or indirectly communicating with or through a main system at another location. Remotes sites may be fixed or mobile. remote switching center RSC. RSC has three generally accepted meanings: (1) a secondary telecommunications switch facility located at some distance from a main facility (at a remote location), (2) a switching center that is designed to serve remote subscribers who are often hundreds of miles away, (3) a switching center in a central or remote location that is remotely managed and controlled through telecommunications links from another center intended for that purpose. The first two meanings are traditional meanings, established before sophisticated software and digital links were available, and are still relevant. The third meaning is becoming more prevalent as telecommunications networks such as the Internet make it practical to configure, manage, log, and maintain switching services from a (remote) location offsite from the actual switching facility. Spelling the third as remoteswitching center helps prevent ambiguity with traditional meanings. Remote Telescope Markup Language RTML. Just as HTML is a markup language for representing information and handling user requests on the Web, RTML is a markup language for handling user requests for astronomical observations. It is a specialized request mechanism based upon XML. RTML was initiated and has been adopted by the Hands-On Universe (HOU) Project as a proposed standard for users to send requests to observatory remotely controlled telescopes. RTML 2.0 was released by F. Hessman in May 2001. This version had changes and additions to RTML 1.1 and subsequently was refined by Denny and Downey. Denny then concurrently developed XRTML as an interim format; this came to be called RTML 2.0 while Hessman’s fuller implementation, called RTML 2.0b, was renamed RTML 3.0. Objects were removed from RTML 2.0 to create RTML 2.1, which is specifically

a request mechanism, with no support for the return of data. RTML 3.0, (released as 2.0b in July 2001) fully specifies a two-way communications protocol for submitting, updating, and acknowledging astronomical data requests, and for returning status information and data related to these requests. See Robotic Telescope Markup Language for the events leading up to RTML. remote terminal A local computer terminal that enables remote access to services or accounts not available on the local terminal. Thus, a remote terminal in a branch office could be used to communicate with a centralized databank in the main office, for example. Remote terminals may be wired or wireless, or may be connected through a combination of wireline and wireless services (e.g., from the terminal to a wireless access concentrator to a satellite link to the main office). Remote terminals are often classified as dumb or smart terminals. In general, dumb terminals are those which have limited capabilities and may have few applications that can be executed locally. Dumb terminals are used in situations where cost or security are concerns. Smart terminals are those that have significant functionality on their own, even if not connected remotely to another system. Remote User Telnet Service A means by which a specific service of User Telnet may be accessed by opening a port connection (107), a mechanism suggested by M. Mulligan and submitted as an RFC in 1982 by Jonathan Postel. This enables remote access to another system for logging in and executing commands. It is now considered a historic service. See RFC 764, RFC 818. remotely piloted vehicle RPV. A land, water, air, or space-based vehicle piloted from a remote location, usually through radio control signals (though other methods are theoretically possible). Military drones, children’s toys, and robots may be controlled this way. removable media Storage cartridges, drives, or diskettes which can be swapped out and replaced with another. This provides a less expensive, portable option to numerous fixed storage devices. In the mid1990s various cartridge drives became very popular, as it was possible to store from 100 to 1000 Mbytes on a cartridge not much bigger than a floppy. The problem was that every cartridge drive had a different format and the formats were not intercompatible. More recently, super diskettes have been introduced, which use normal floppy-sized disks that can store 100 MBytes, but the drives are still downwardly compatible with 1.44 floppies, so that it’s not necessary to have several devices attached to the computer. It is not clear, as of this writing, which of these technologies will prevail or whether another new one will leapfrog them before one or the other is firmly established. REN See Ringer Equivalence Number. RenderMAN Interface Bytestream RIB. RenderMAN is a widely distributed, popular 3D rendering engine distributed by Pixar, which is well-known for its animated, rendered movie features such as Toy

Story. RIB is the file format used by RenderMAN and the files may be distinguished by the .rib extension. REO removable erasable optical. repeat dialing This is both a function of some phones and telephone/computer software programs, and a service of some phone companies in which a number found to be busy can be repeatedly dialed until the connection goes through, without the user dialing the number again. Repeat dialing is very commonly used in telecommunications software programs to dial up BBS numbers that are frequently busy. repeater A device for receiving signals and retransmitting those signals in order to propagate or amplify the signal. Repeaters are commonly used in technologies with signal attenuation and fade. Repeaters are used in digital and in analog systems and are often spaced at intervals over paths that cover long-distances. In digital systems, it is possible to reconstruct the informational content of the signal; in analog systems, more often the signal is amplified, which means that accumulated noise and degradation are still limiting factors. Radio broadcast repeaters and microwave repeaters are examples of common implementations. In networks, a number of devices assist in the conversion and propagation of signals (bridges, routers, etc.). A repeater is simpler than most of these devices, serving only to continue the signal and extend its range, or to clean it in its most basic sense, rather than to change the informational content of the data. See amplifier, bridge, doping, regenerative repeater. reperforator An instrument which translates received signals into a geometrically coded series of locations that are punched or otherwise impressed onto a paper tape. Early telegraph systems and most of the early computing devices used reperforators. These were then read with optical or tactile sensing devices to turn the code back into human-readable form. See chad. reperforator/transmitter RT. A teletypewriter device which includes both a reperforator for punching received codes on paper tape, and a tape transmitting unit for sending the codes to a tape punching mechanism. repetitive pattern suppression RPS. A means of data optimization which compresses digital communications by removing repetitive patterns and reproducing them at the receiving end. replication A process commonly used on computer systems for security, redundancy, distributed access, or other backups. In large companies and on the Internet, whole file archives are often replicated or mirrored in order to provide access at a reasonable speed to a larger number of uses. Replication of data is a means to protect data in case of a serious problem with a system or storage device. RAID systems are a means of replicating data to preserve data in case of a fault. Replication in the form of regular backups is recommended for all important computer data that need to be preserved. In radio communications, transmissions are sometimes repeated to im-

prove the chances of a message getting through. The replication may be of individual small units of transmission or may be repetition of a short message or signal. See ALOHA. reprography Copying and replicating. Republic, S. S. In 1909, due to a collision, the S. S. Republic sank, yet all hands were saved but two. The lifesaving role played by wireless equipment and operators led to legislation requiring other vessels to use wireless emergency equipment. Similarly, when the Titanic sank, legislation was further instigated to require greater diligence in round-the-clock wireless monitoring. See Titanic. REQ request. Request for Comments RFC. A formatted, open communications forum for technical experts which accepts, edits, numbers, publishes, and disseminates Internet-related documents including protocols, draft and official standards, notices, opinions, and research. Known as RFCs, these electronic documents form a body of more than 2200 contributions that provide a remarkable overview of the evolution of the Net, its structure, functioning, and philosophies. There are a number of categories of RFCs. Some of them are tiered and cannot be submitted without passing through previous categories in a specified order, with specified waiting periods for comments and revisions from the RFC community. Code

Category

(no code) I H E PS DS S

Unclassified Informational Historical Experimental Proposed Standard Draft Standard Standard

RFCs are not changed once they have been submitted, assigned a number, and distributed. Any changes regarding an RFC must be submitted as a new RFC. There are many excellent RFC repositories on the Internet, with good indexes and abstracts. Anyone can submit an RFC provided it is topical and follows the official format and procedures. This dictionary includes references to specific RFC numbers where the author felt the technical origin of the information would be of interest, and there is an overview of significant RFCs in the Appendix. For information on submitting RFCs, see RFC 1543. Request for Discussion RFD. Similar to a Request for Comments (RFC) in that it is a means on the Internet to solicit and generate discussion on a specified topic. However, it focuses on intercommunication on a topic in a slightly less formal or definitive manner as opposed to specifying or defining a topic once certain conclusions or draft/final working models have been developed, as in RFCs. RFDs often

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precede RFCs but do not necessarily result in RFCs. See Request for Comments. Request for Information RFI. A solicitation and notification of interest in receiving feedback or information on a specified topic, product, or process, without implying that the requester necessarily wishes to purchase or use that for which the information is solicited. See Request for Comments, Request for Discussion. Request for Proposal RFP. A call for proposals for solving a problem or participating in a project. A Request for Proposal process is used by many institutions to initiate a project such as building a facility, setting up a new organization, or developing a new product or service. People who submit RFPs usually have a community or economic interest in shaping or otherwise participating in the project. A Request for Proposal may or may not be accompanied by a Request for Quote. See Request for Quote. Request for Qute RFQ. A call for monetary quotations for a particular project or venture. The RFQ process is commonly used by institutions to assess various aspects of implementing a project and what that project will cost. Vendor input in the form of RFQs not only provides information on the price, but may also give some idea of the timeline and type of materials involved. It also serves as a form of preliminary contract (and is sometimes the only contract) once a vendor has been selected to undertake a job. An example of a simple RFQ would be a faxed page explaining that the cost of purchasing and installing a new modem might be $200. An example of a more complex RFQ would be a 12-page document detailing the costs involved in setting up a video security system in a business office or factory that can be monitored and controlled (through pan and tilt controls) from a remote location through the Internet. A Request for Quote may accompany a Request for Proposal or may sometimes be combined with a Request for Proposal. See Request for Proposal. reroute A temporary or permanent change in a data path. Rerouting frequently occurs in large, dynamic networks like the Internet. Systems where rerouting is common usually use a hop-by-hop method of routing in order to accommodate changes and to create new paths as needed. In electronics, rerouting of a circuit may be accomplished by a patch or shunt, a wire which bypasses the original path. On Fiber Distributed Data Interface (FDDI) networks using dual rings, rerouting to the second, backup ring is carried out if a problem is detected on the primary ring. RES 1. regional earth station. 2. See Residential Enhanced Service. Resale and Shared Use decision A decision of the Federal Communications Commission (FCC) to allow competition in value-added networks. resampling The process of subsequent sampling of data, as image or sound data, and re-encoding it. Resampling usually occurs when the original sample was not of the resolution level or compression rate desired. Resampling may also occur in order to

update or refresh information that may be changing, as in Internet videocam shots, videoconferencing, etc. See sampling. research and development R&D. The study and associated development of theories, sciences, and technologies. In telecommunications, much R&D is focused on creating marketable products. R&D often consumes a huge proportion of a startup business’s budget. Many large corporations have R&D facilities to enable them to develop new products, prominent among which are IBM, Lucent Technologies (Bell), and Xerox. In many cases, R&D does not directly result in products that can be manufactured and distributed, but the process of R&D indirectly contributes in surprising ways or, sometimes, decades later, when manufacturing processes or needs change or catch up to the theories. As an example, Charles Babbage’s historic analytical engine (a pioneer computer concept) research and design was apparently theoretically sound, but the technology to build his machines did not exist during his lifetime. As a more recent example, space research has resulted in many portable and wireless communications technologies that might not have developed otherwise. Research and Education R&E. Those served by the National Science Foundation’s (NSF) networking efforts. Research in Advanced Communications in Europe RACE, RACE II. Also known as Research and Development in Advanced Communications Technologies in Europe and R&D in Advanced Communications Technologies in Europe, this program began with work by the RACE Management Committee that was tendered to the European Community Council and became the predecessor to the later Advanced Communications Technologies and Services (ACTS). RACE was organized in the mid-1980s to aid in the EC-wide establishment and unification of communications systems and providers. Following a definition stage, the RACE projects were carried out between 1987 and 1995 with financial contributions from the EC. Over the period of its tenure, more than 350 organizations participated in RACE projects and RACE collaborated with many important organizations, including ETSI, EFTA, EUREKA, ESPRIT, and others. In the early and mid-1990s, RACE was involved in the research and development of telecommunications technologies leading to the development of the Integrated Broadband Communications (IBC) system and more specifically the Mobile Broadband System (MBS). With its evolution to ACTS, the third phase of IBC development continued the work beyond the original 5-year mandate of the RACE projects. See Integrated Broadband Communications, Mobile Broadband System. Research Institute for Advanced Computer Science RIACS. A research facility located at the NASA/Ames Research Center in California. In conjunction with the NASA/Ames center, RIACs sponsors a Summer Student Research Program

(SSRP) to provide students with the opportunity to team with research professionals in Moffet Field. Topics include automated reasoning, high-performance computing and networking, and applied research for NASA missions. Research Laboratory of Electronics RLE. The first interdisciplinary research lab established at the Massachusetts Institute of Technology (MIT). The RLE, founded in 1946, is descended from the MIT Radiation Laboratory, which provided some significant discoveries during World War II. RLE brings together expertise from many quarters, including electrical engineering, physics, computer science, chemistry, aeronautics, linguistics, and others. The facility is primarily supported by the U.S. Department of Defense (DoD), the Department of Energy (DOE), and several national institutes and foundations (NASA, NSF). Réseaux Associés pour la Recherche Européenne RARE. A European research network that was merged with EARN in 1994 to form TERENA. A number of technical reports were published by the RARE Working Group prior to the merger. See TERENA. reseller A company which purchases a block of services (e.g., long-distance services) or numbers (e.g., cellular phone numbers) and resells them directly to customers. The reseller does not own and usually does not maintain the physical structures or services, but usually provides information and technical support to the resale customers. See agent, aggregator. reset v. Return to the previous or default or factory operating settings. In computer operating systems, a reset command usually restores the system to the same configuration (or nearly so) as a fresh powerup, although some will restore memory, parameters, etc. without resetting some of the basic subsystems (e.g., sound). A software reset that doesn’t involve a power-down is termed a “warm boot” and a complete power-down is called a “cold boot.” If a software reset doesn’t seem to correct problems, it’s best to do a cold boot. But wait at least 15 seconds for the power to drain from the chips before powering up again. In timing mechanisms or data counters, a reset usually restores the time or counting mechanism to a zero condition or industry default. Residential Broadband RBB. A broad term for higher capacity/higher speed broadcast and networking services to residences. Larger providers such as NTT and AT&T are already engaged in upgrading cables and services to provider a greater range of programming choices to home subscribers. New switching technologies are an important technological and economic component of these upgraded services. See fiber to the home. Residential Broadband working group. RBWG. A working group of the ATM Forum Technical Committee which promotes a single set of global specifications to maximize interoperability of products from various vendors. The Residential Broadband group provides documents and recommendations

regarding enhanced services to residential users of ATM-related technologies. Residential Enhanced Service RES. A telephone subscriber service package offered by Nortel that includes enhancements such as increased security and features such as Call Redirect. resinous electricity A term coined by Dufay to denote the type of electrostatic charge produced on sealing wax when rubbed with flannel (or amber rubbed with wool). Later, in the 1700s, Benjamin Franklin proposed negative, a term that superseded vitreous. See electrostatic, static electricity, vitreous electricity. resistance 1. Opposition, counteracting force or retarding force against. 2. In electricity, opposition to the flow of current, usually expressed in ohms. There is great variability in the resistance of various materials. Those with low resistance, such as silver and copper, make good conductors. Resistance in a particular material may change with temperature, moisture, or the presence or absence of current. Resistance is defined as the reciprocal of conductance. See reluctance, resistor, ohm. Contrast with conductance. resistor A component or system which provides resistance to electrical current. Some materials are naturally resistant, and this property may be further exploited by the way a circuit is configured (e.g., longer wires, more loops, etc.). Controlled current is useful in a number of circumstances and can be used to protect sensitive components or to provide operational control. Electronic resistors use standard color coding schemes to identify the degree of resistance they provide. Applying Ohm’s law, it can be stated that the combined resistance of any two resistors connected in parallel can be expressed by dividing their product by their sum. See Ohm’s law, resistance. resolution Resolution is somewhat technology-specific, since it is often based not only on the size or discrete value of an individual unit, but also on the total area occupied by a block or line of units, and the units will vary depending upon the type of medium or technology described. resonance 1. The enrichment of a sound by supplementary vibration. For example, the body of an acoustical stringed instrument is designed to increase the resonance of the string vibration by transmitting the sound through the bridge, the sound holes, and the body. 2. A greater amplitude vibration arising from smaller periodic vibrations with the same, or nearly the same, period as the natural vibration period of the system. This can arise in both electrical and mechanical systems. 3. The enhancement of an event by creating excitation within the system, as in particle reactions. See magnetic resonance imaging. 4. In a circuit, a balanced condition between inductive- and capacitive-reactance components. resonance curve A diagrammatic representation of the relationship of various frequencies at or near resonance to a tuned circuit. resonant frequency The frequency at which a maximum

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amplitude response occurs in a given object or system when acted upon by a constant amplitude sinusoidal force. In an antenna, for example, the transmitting current is greatest when the impedance level is lowest at a given frequency and power. resonator A device which increases and/or directs sound, as in a musical instrument, music box, or telegraphic sounder. In gramophones, a horn which amplifies and directs sound to the listener. In telegraphic systems, a box which holds a sounder and directs the audible clicks to the ear of the operator. In microwave communications, a hollow, metallic container in which microwaves are produced. In crystal detectors, a piezoelectric crystal which oscillates when stimulated by radio waves. Resource Location Protocol RLP. A network protocol to assist in the location of a network resource in situations where other methods may not be practical. This was submitted as an RFC by M. Accetta in 1983. RLP uses a request/reply procedure to request an IP number or appropriate identifier. As an example, RLP can name a resource by an assigned protocol number and a variable-length protocol/ resource-specific identifier. See RFC 887. Resource Management RM. In an ATM system, cells contain information for managing bandwidth, buffers, and flow control aspects such as loads, traffic congestion, etc. These resource management (RM) cells are thus associated with the administration of the data transmissions. They are passed along the path through various switches to monitor and control congestion by adjusting the various cell rates (current, explicit, minimum) as needed. See cell rate. response time 1. The time it takes to react appropriately to a given situation or signal. In business, response time to customer inquiries is often critical in making sales and getting repeat business. The response time to a phone call usually needs to be four rings or less in a business environment, or eight rings or less in a residential environment, or the caller may give up and terminate the call before it is answered. In computer operations, response time of an input device, or the software, is important in terms of productivity and user satisfaction. 2. A command called ping can be used in network testing and management to determine a response time, or whether a host is even available to respond. See ping. Responsible Organization See SMS/800. restart 1. Initiate again, begin again. Put back into service or operation, to power up again. 2. In computer operating systems, to reinstate operations without having to power down and power up the entire system. Many computers have a key sequence, menu selection, or restart button which will reinitialize the operating parameters without a full power up sequence. In some systems (e.g., Macintosh), the restart option will also do a clean shutdown of the system in order to ensure that files and applications are closed, and important processes finished so no data corruption occurs from a sudden shutdown. See reboot. restocking fee A fee charged by many companies to

partly compensate for the time and expense incurred by the company when the consumer returns an item for a refund or exchange. restore 1. To put back to its previous or original state, to renew, revive, to return to good operating order. 2. To return to the original position, location, or owner, to re-establish, to reinstitute service. 3. To get back data which have been erased or damaged, either by rebuilding or relinking pointers, file tables, and directory tables on the storage medium, or by accessing a backup archive of the data as they were last saved. 4. In programming, to return the value of a variable to a previous value, which may be a default or original value. 5. To recharge or refresh information in a memory circuit with continuous or periodic current. Lithium batteries are sometimes used for this purpose. 6. A gadget on the edge of the windows of most operating systems with graphical user interfaces (GUIs) which allows the window to be automatically sized to its original size without the user having to remember the setting or do it manually. Restricted Numeric Exchange See RNX. Restricted Radiotelephone Operator Permit RP. A fee-based permit granted without examination by the Federal Communications Commission (FCC) for the operation of most aeronautical and ground radiotelephone stations aboard pleasure craft (with some restrictions). The permit also covers the operation, repair, and maintenance of AM, FM, television, or international broadcast stations. See Marine Radio Operator Permit. Reticular Agent Definition Language RADL. An object-oriented language distributed by Reticular Systems, Inc. to facilitate the development of intelligent software agents. RADL is an extension upon work by Shoham (AGENT-0) and Thomas (PLACA – Planning Communicating Agents). Reticular Systems also provides AgentBuilder, graphical tools for developing RADL programs. AgentBuilder can provide support for Knowledge Query and Manipulation Language (KQML), which can be used to share knowledge among multiple intelligent systems. AgentBuilder Enterprise supports realtime examination of remote agent operation, a Role Editor for defining agent roles, mobile agent support, CORBA/ DCOM support, and an enhanced repository manager. See Knowledge Query and Manipulation Language. RETMA Radio Electronics Television Manufacturers Association. See Electronic Industries Alliance. retransmission consent In television cable broadcasting, consent is a local TV station’s right to negotiate fees associated with program provision. It is common for a local station to purchase a variety of television programming from various distributors and broadcasters. They then resell these programs in various packages to local cable subscribers. See cable access, Cable Act. retrofit n. To equip a device or system with new parts or capabilities that were not available, or perhaps not requested, at the time of initial purchase and installation. For example, it is very common for

computer parts retailers to offer accelerator cards, storage device controllers, faster CPUs, and other enhancements to users trying to upgrade or extend the life of their systems. retry Another attempt to perform the same operation if the previous attempt failed. This is an intrinsic part of most computing processes. If a process fails to read or write data from or to a storage location, it will retry a certain number of times before alerting the user that there is a problem. If a modem fails to connect, it may redial a specified number of times before signaling an error condition. If a mail server tries to send email to a recipient who cannot be found, it may try a number of times before bouncing the email back to the sender. For many operating systems, the retry parameters are set by the programmers and are transparent to the user, and not changeable. For individual applications programs, there may be settings in the user preferences which allow retries for various operations to be controlled. return CR. A common designation for the carriage return key on a keyboard (sometimes called the enter key) or carriage return function in a program such as a word processing program. On most systems, the carriage return incorporates not just a return (which returns the cursor to the far left or right of the screen, depending upon the language), but also a new line (which drops the cursor down to the next line). return authorization RA. Permission from a manufacturer or vendor for a consumer or dealer to return a product, usually because it is defective, damaged, or does not meet the advertised specifications. Few vendors will process a return without prior authorization. Authorization is usually identified with a return authorization (RA) number, sometimes called a return material authorization (RMA). The RA is used for internal database tracking and inventory control. return loss A measure of the ratio of incoming to outgoing power, usually expressed in decibels, at a specified reference point. Return loss is a diagnostic means of evaluating various factors such as loss, quality, echo, etc. return material authorization RMA. See return authorization. REV reverse. Reverse Address Resolution Protocol RARP. A client/server tool for reporting an Internet Protocol (IP) address to its client. The protocol is intended for workstations to dynamically determine protocol addresses when only the hardware address is known. The Ethernet address is mapped to the logical IP address. Used in TCP/IP. See RFC 903. reverse bias See back bias. reverse engineering A process of working backward from a finished product or process to determine the steps taken to construct it. Thus, a clock can be taken apart to see what makes it tick, and a software program can be taken apart to see what algorithms and conditional relationships were used in its construction. Software developers are generally nervous about having their software reverse engineered,

because it is difficult to prove reverse engineering in cases of theft of intellectual property. reversing error, reversal error A condition in which current divided through two circuits, such as through a component and a measuring instrument, will vary due to the deflection of the measuring instrument for the same current passing in both directions. See shunting error. revision control system RCS. A system for managing, queuing, and logging revisions. This is important when designing a device or protocol, or creating a document (e.g., a software manual) and is especially relevant for quality assurance and projects with more than one contributor. There are both manual and computerized revision control systems. A simple example is a bulletin board posting to inform the people involved in a revision process. Revision control is increasingly being built into software systems in factories and offices. There are automation systems that will keep track of changes in a manufacturing or packaging process to prevent errors and provide an audit trail. There are word processors that will log changes by individual editors with symbols or colors, as well as automatically date/ time-stamp the changes, so that the process is documented and the changes can be traced backward, or the individual responsible for particular changes can be identified. Software designed for workgroups often has revision control features that prevent different contributors from changing a document at the same time and may notify members of a workgroup whenever new revisions occur. RF 1. See radio frequency. 2. range finder. A device for determining distance (and sometimes also direction). See radar. 3. raster file. See raster. 4. rating factor. RFA 1. See remote file access. 2. request for action. RFC 1. See Request for Comments. 2. required for compliance. RFD See Request for Discussion. RFE Radio Free Europe. RFF raster file format. See raster. RFI 1. Radio France International. 2. radio frequency interference. Electrical noise resulting from some wire or attachment acting as an antenna. 3. See Request for Information. RFP See Request for Proposal. RFQ See Request for Quote. RFS 1. radio frequency shift. Unintentional drift or intentional shift (change) of a broadcasted radio frequency. This may be done for security purposes or to maximize the availability of bandwidth. See frequency hopping. 2. radio frequency system. 3. range finding system. 4. remote file sharing/system. RG-58U A type of thin-wire cable used in 10Base-2 data communications cabling installations. RGB red, green, blue. An abbreviation to describe the three primary colors of an additive (light-based) color model. This is the model used in most computer video display devices. The colors in the spectrum are created by systematically manipulating the

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amount of red, green, or blue that can be individually stimulated. In many computer software application palettes, the absence of any R, G, or B color is designated as 0 and the full intensity (of a transistor or cathode-ray tube gun) is designated as 255, with other colors created by mixing intermediate values. Thus, purple is created by mixing red and blue and white is created by displaying all three colors at full intensity. RGO Royal Greenwich Observatory. RGP raster graphics processor. See raster. RGS radio guidance system. Rhealstone A type of computer processing system benchmark used in realtime multitasking systems. Run times for a set of operations (task switching, interrupt latency, etc.) are independently measured. See benchmark, Whetstone, Dhrystone. rheostat A device with one fixed terminal and a movable contact, used to regulate a current by varying the resistances. Similar to a potentiometer, except that a potentiometer can connect to both ends of the resistance-varying element. See potentiometer. Rhumbatron Oscillator This is a very widespread apparent (mis)spelling on the Internet for Russell Varian’s Rumbatron Oscillator, mentioned here to help find the cross-reference. In Varian’s original handwritten note of July 1937, he called it a Rumbatron Oscillator (at least in this instance). It’s an important forerunner to the linear accelerator. See rumbatron, Klystron. Rhumkorff coil An induction coil which can be used to induce high voltages, first constructed in 1850 by Heinrich Rhumkorff. This technology was developed into ignition coils. See coil, induction. Rhumkorff, Heinrich A German physicist of the 1800s who first constructed the induction coil. Riad computer A type of IBM System/360 seriescompatible computer developed in Russia. RI 1. radio interference. See attenuation, jitter, noise. 2. Rockwell International. RIAA See Recording Industry Association of America. RIACS See Research Institute for Advanced Computer Science. RIAS See Research Institute for Advanced Studies. RIB 1. See RenderMAN Interface Bytestream. 2. See routing information base. ribbon cable A cable design in which the wires are encased so they are aligned side by side, in close proximity with insulating material separating the wires and holding the whole structure together like a long strip of ribbon. Typical ribbon cables carry between 9 and 60 wires. Ribbon cables are commonly used for parallel wiring connections, disk drives, and other data transfer applications, although some types of ribbon cables carry AC power. Ribbon cables are somewhat more fragile than other types of more heavily shielded cables and kinks in the cables can snap the conductors, if they are very fine. Wide ribbon cables can be difficult to attach to other types of connectors. Nevertheless, they are

convenient to use in a number of places (inside computers and under floor coverings) because they are flat and flexible. RIC regional information center. Rice computer The Rice Computer Project was inspired by the MANIAC II at Los Alamos. Three professors, Zevi Salsburg, John Kilpatrick, and Larry Biedenham, initiated the project, which culminated in the development of a computer for research, and research into the development of computers. Joe Bighorse, as head technician, implemented most of the hardware design. The computer came online in 1959 and was fully functional by 1961. For almost a decade it was the primary computing machine on the Rice campus. Architecturally, the Rice 1 (R1) was descended from the Brookhaven computer and the MANIAC II. It was essentially a tagged-architecture computer, using 54-bit vacuum tubes plus two tag bits and seven error-correcting bits. It implemented indirect addressing capabilities and memory was stored in cathode-ray tubes (CRTs). After 1963, transistor-based logic was added.

Examples of two ribbon cables: the top 34 pins, the bottom 50 pins. The flat flexible cables are commonly used inside computers where space is limited and narrow. Several devices, such as hard drives and CDROM drives, can be daisy-chained on one length of cable by inserting connectors that pierce the cables and make contact with the wires.

Rich Text Format RTF. Also called Interchange Format. A document encoding file format developed by Microsoft that retains simple text formatting codes and basic text attributes (typestyle, size, bold, italic, underline, etc.). A widespread format that can be exported and imported between word processing, OCR, and desktop publishing programs. It is a good intermediary format to use when moving text with attributes from one system to another. Many people use ASCII to export/import text, and despair because the formatting is lost. You may wish to try RTF. Although there are different flavors of RTF, it usually works and can save hours of reformatting. Here is a very basic example of Rich Text Format showing the syntax for various formatting parameters.

{\rtf0\ansi {\fonttbl\f0\fswiss Helvetica;} \paperw9880 \paperh3440 \margl120 \margr120 \pard\tx20\tx7120\f0\b\i0\ulnone\fs20\fc0\cf0 Rich Text Format \b0 RTF. Also called Interchange Format. A document encoding file format developed by Microsoft that retains simple text formatting codes, and basic text attributes (typestyle, size, \b bold \b0 , \i italic \i0 , \ul underline \ulnone , etc.). A widespread format that can be exported and imported between most word processing, OCR, and desktop publishing programs. It is a good intermediary format to use when moving text with attributes from one system to another. Many people use ASCII to export/import text, and despair because the formatting is lost. You may wish to try RTF. Although there are different flavors of RTF, it usually works, and can save hours of reformatting. Here is a very basic example of Rich Text Format, showing the syntax for various formatting parameters.\ }

Rich Text Markup Language RTML. A proprietary programming language used by the Yahoo! Store to generate commerce-enabled Web sites. Yahoo! Store third-party developers provide services for automated Web site creation through their RTML tools. RTML is a combination HTML editor and commerce-specific components development tool for adding the types of features that businesses like to include in their Web sites to support product promotion and sales. RIF See rate increase factor. RIFF 1. raster image file format. See raster. 2. Resource Interchange File Format. A platform-independent multimedia specification developed in the early 1990s by a group of vendors including Microsoft Corporation. RIG related interest group. See Birds of a Feather. right-hand rule, Fleming’s rule A handy memory aid widely used in mathematics and physics to determine an axis of rotation or direction of magnetic flow in a current. Extend the thumb and fingers of the right hand so that the fingers are held together and point straight in one direction, with the thumb at a right angle to the fingers, in an ‘L’ shape. Now curl the fingers around a conductive wire, so that the

thumb points in the direction of the current. The direction of the curled fingers then indicates the direction of the magnetic field associated with the current. Using the same hand relationship, point the thumb in the direction of wire motion and the fingers will show the direction of the magnetic lines of force and the direction of the current, for a conductor in the armature of a generator. For the direction of current for a conductor in the armature in a motor, see left-hand rule.

The right-hand rule is a visual mnemonic device for remembering the relationship of the direction of the current in an electromagnetic field.

Rijndael A block cipher data securing system designed by Joan Daemen and Vincent Rijmen selected by the U.S. Government for its Advanced Encryption Standard (AES). Rijndael has variable block and key lengths and has been specified for keys of 128, 192, or 256 bits in length. It can be implemented on a variety of processors. Rijndael was based, in part, upon concepts developed by Daemen and Rijmen for the Square block cipher. See RC6, Square. ring 1. The sound made by a phone or other communications device to indicate an incoming call or imminent announcement (as on a PA system). The frequency of the tone and its cadence vary from country to country. In North America, phones typically ring once every 6 seconds. 2. Traditionally the red wire in a two-wire telephone circuit. The name originates from the configuration of a manual phone jack in an old telephone switchboard in which the large plug was divided into two sections, with an internal wire electrically connected to the tip of the plug and another wire to the ring around the plug partway up the jack, nearer the insulated cord. The ring is traditionally around –48 volts, with the negative charge used to help to prevent corrosion. See tip, tip and ring. ring error monitor REM. In a Token-Ring network, “tokens” are passed around from machine to machine in a ring topology. A ring error monitor is a program that can be installed on machines in the ring to collect and signal ring-related errors in the form of soft errors and hard errors (MAC frames). Ring-related errors may include lost frames, tokens, or Frame Check Sequence (FCS) errors. ring-armature receiver A telephone receiver which began to be widely installed in the 1950s following the development and widespread use of the bipolar receiver. It differed substantially from earlier receivers in its details, incorporating a lighter, more efficient

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dome-shaped diaphragm, driven piston-like by magnetic fields across the armature ring. See bipolar receiver. ring-around-the-rosy A theoretical hazard situation on the phone system, in which a circular tandem connection exists, somewhat like an endless loop in a software routine. ring, network A type of circular network topology. See Token-Ring. Ring Again A telephone service that enables a caller to request notification if a busy number becomes available. When the number can be dialed, the caller’s phone will ring and the call will be automatically placed on the caller’s behalf, without the need to dial a second time, when the phone is picked up/ activated. In general, only one Ring Again request can be set up at a time. See Make Busy. ring topology A network topology in which each station in the network is connected in a closed loop so that no termination is required. In this architecture, data packets are passed around the loop through each intervening node until they reach the destination machine. Ring topologies are fragile in the sense that failure of one node or system affects the entire network. See star topology, topology. ringback A usually undocumented, self-ringing telephone test number that can be used to verify the number of a particular phone. In some regions, when a two- or three-digit number, followed by the expected phone number, is dialed, a new dial tone is provided, which can then be used for ringing tests. Ringback functions are used by service technicians after a phone has been installed to verify that the system is functioning correctly. They are also sometimes used for confirmation by subscribers. In some regions, the ringback service connects the caller to a recording which identifies the exchange in which the phone is located. See ringing tone. ringdown See ringing current. ringer, bell The mechanical or digital sound generator that indicates the presence of an incoming call. The interval and type of tones generated vary from phone to phone, and even more so from country to country. With the proliferation of digital devices, it is likely that ringers will eventually be configurable. You’ll be able to load in a sound patch and have the phone sound like anything desired: a cat, a parrot, a jet airplane, your spouse’s voice, etc. In fact, paired with a Caller ID system, there is no reason why the ringer couldn’t switch to a device that says out loud, “Hank is calling, want to talk to him?” (This definition was originally written in 1997. Since 2001, several wireless phone vendors have begun providing downloadable ringers to their mobile subscribers.) Ringer Equivalence Number REN. When telephone equipment is purchased and several devices are placed on the same line, there is a need for a way to designate and organize the ringer load on the line so as not to exceed the available current. In the United States, a certification number has been developed for telephone products which indicates that they meet certain specified requirements and guidelines. This REN helps installers and consumers to set

up various pieces of equipment (phones, answering machines, fax machines) so that they will not interfere with one another when connected. Various devices on the same line may have different REN values. If a certain maximum number of RENs is exceeded, the various devices cannot be guaranteed to work correctly and may not ring. For data modems, the Ringer Equivalence Number is usually printed on the main chip in the center of the internal modem board, along with the Federal Communications Commission (FCC) registration number. It may also be listed on a label on the back of an electronic device. In most regions, the sum of the RENs on one line should not exceed 5.0. In Canada, the concept of Load Number is essentially the same as the REN. ringing The production of an audible signal at the receiving end by means of a mild AC or DC current to indicate signaling or the presence of an incoming call. In telephony, a ringing current is sent from the central office to the subscriber or from a local console or branch to a local phone device. ringing current, ringdown The current on a telephone system used to transmit ringing signals and ringing tones. This varies with the type of switching system and the distance over which it has to be carried. In older phone signaling systems, for example, the ringing signal was carried by 20 Hz AC current for local distances, and 135 to 1000 Hz AC current for long-distance calls. See talk battery. ringing key In a telephone switching system, a means by which the subscriber’s telephone ringing is initiated by a key at the central office to indicate a call. Signaling current was sent as alternating current from a central office to the subscriber, a system that didn’t work well for long-distance calls due to the loss of the signal over distance. ringing signal Any signal transmitted over a telephone to initiate ringing on the receiving phone to indicate that a call is coming through. Various schemes for sending this signal have been used over the years to make it possible to send the ringing signal over distances without the current interfering with actual call transmissions. See ringing key. ringing tone, ringback A tone generated in the caller’s line to indicate a call is being routed to a receiving phone. The ring at the receiving end is initiated by a ringing signal sent from the central office or private branch switching system. This doesn’t absolutely guarantee that the callee’s phone is ringing. If the bell is defective or the routing of the call was in error (either through incorrect switching or because of dialing the wrong number), the callee may never hear the ring. See ringback, ringing signal. ringing voltage The amount of voltage applied in an analog telephone switching system to cause the called phone or other phone device to ring, usually about 88V. There is a limit to the number of devices which can be rung when attached to a single line, too many, and there will be interference with the ringing circuitry. For more information, see Ringer Equivalence Number.

RIP 1. See Routing Information Protocol. 2. See raster image processor. 3. See Remote Imaging Protocol. RISC See Reduced Instruction Set Computing. Ritchie, Dennis M. (1941- ) An American Bell Laboratories researcher who codeveloped Unix in collaboration with Ken Thompson. He is well known for his development of the C programming language, along with Richard Kernighan. See C, Unix. Ritchie, Foster An inventor and early assistant of Elisha Gray who designed a writing telegraph in 1900 based on principles different from those originally patented by Gray a few years before. Known generally as telautographs, these devices could transcribe handwriting across short distances and were in use for several decades. RJ The Universal Service Ordering Code (USOC) for Federal Communications Commission (FCC) – registered jacks for connecting to a public network. USOC was developed in the 1970s by AT&T and the telecommunications industry is widely standardized on this system. Each type of jack has a number of wiring configurations, depending upon the number of wires connected. Thus RJ-25 wiring uses the same jack as RJ-11 except that eight wires are connected

instead of two. In many cases, not all the wires are used. Wires are often connected in pairs. In order to promote pair continuity when plugging into receptacles with varying numbers of active wires, the wires are usually connected in pairs beginning in the center and working out. In the following Common Wiring Jacks chart, C represents flush or surfaced mounted, W represents wall mounted, and X is complex line. RJE See remote job entry. RJEP See Remote Job Entry Protocol. RL 1. radio locator. See radio beacon. 2. resistor logic. 3. return loss. RLCM Remote Line Concentrating Module. RLE See run length encoding. RLP See Radio Link Protocol. 2. See Resource Location Protocol. RM See Resource Management. RMA, RA returned merchandise authorization. A coding system used to control and track returned merchandise. See return authorization. RMF remote management facility. rms See root mean square. RMF read, modify, write.

Sample of Common Wiring Jacks Described in Universal Service Ordering Code (USOC) Jack

Wiring

RJ-11

Notes Can accommodate up to six wires, though typically only two or four are connected as one or two pairs. A very common type of single-line phone jack used for telephones, modems, and fax machines.

RJ-11C/W

One pair of wires connected, as for a single line phone. Traditionally the green and red wires are connected as tip and ring for the first line. The connection is bridged.

RJ-14C/W

Two pairs of wires connected, as for a two-line connection, e.g., line 1 might be a phone or answering machine and line 2 a modem or fax machine. Traditionally green and red are assigned as tip and ring for the first line, and black and yellow as tip and ring for the second line. The connections are bridged.

RJ-25C/W

All three pairs configured. Thus, line 1 might be a phone, line 2 a modem, and line 3 a fax machine.

RJ-45

Can accommodate up to eight wires and is common for multiple line phones (up to four lines) and for data communications, especially Ethernet and Token-Ring. RJ-48C/X

Four wires are typically connected as two pairs to provide 1.54 Mbps digital data network services.

RJ48S

Four wires are typically connected as two pairs to provide local digital data network services.

RJ61X

Four pairs of wires connected to accommodate four phone devices. Three lines are bridged.

10Base-T

Twisted Pair. Pairs two and three are connected.

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rn A full-screen, configurable news reader developed by Larry Wall, the author of the Perl programming language, and released in 1984. Wayne Davison developed a superset of rn known as trn. RN Royal Navy. RNC radio network controller. RNG See random number generator. RNX Restricted Numeric Exchange. A local telephone exchange in which calls are restricted to the network on which they originate. Suppose a number is 555-1111 when dialed from outside the local exchange. The first three digits are the NXX digits. From inside the restricted exchange, you might instead dial 105-1111, with 105 being the RNX digits. The call then rings through to the number without passing through circuits outside the local exchange. See NXX. RO 1. receive only. 2. remote operation. 3. recovery operation. ROA recognized operating agency. An agency tasked with operating a private or public telecommunications service such as the public land mobile network. roaming Using wireless telecommunications services while moving around, either on foot or in a vehicle. The logistics of designing and managing roaming subscribers is quite complex and requires sophisticated software. See cellular phone. See Inter-Access Point Protocol. robbed bit A commandeered bit in a transmission for something other than its usual purpose. This technique may be used to acquire extra bits for signaling information, especially if the signals are only occasionally needed. See robbed-bit signaling. robbed-bit signaling RBS. In data communications, a means of taking one bit from a data path to provide signaling information. For example, in voice communications over in-band T1 systems, a bit may be robbed to indicate the hook condition of the line. Roberts, H. Edward Founder of MITS, which developed and distributed the first commercially successful computer kit, the Altair 8800, that launched the microcomputer industry. Roberts codesigned the computer when the market for calculators began to slip. Roberts left MITS in 1977 and is now a physician. See Altair. robot In its simplest form, a robot is a mechanical apparatus which automatically moves or senses according to a set program, or an adaptive program. In its most complex form, it is a sophisticated electromechanical logical device that can interact with its environment in ways which are ascribed to human intelligence. That is, it is adaptive, and responds in ways appropriate to its task or to its benefit. Robot arms are used in many production-line tasks, whereas many humanlike robots are portrayed in science fiction stories and films. A humanlike robot (in form and functioning) is called an android. A robot is generally associated with hardware and physical forms, but with the development of software artificial intelligence techniques, online avatars that seem to have a humanlike presence on public forums

and chat lines have also been called robots, or more commonly ‘bots or bots. A bot can be online 24 hours a day, can monitor processes, log user activities and interaction, and more. Bots have been banned from some of the chat rooms due to badly programmed bots violating chat Netiquette. However, system operators sometimes have authorized bots running on Internet Relay Chat (IRC) to perform many useful functions. Bots are also associated with search engines. Just as IRC bots do housekeeping tasks on the chat channels, search bots do useful Web page search and retrieve jobs, like a crew of gofers (“go fer this, go fer that”) working around the clock. See mailer daemon. Robotic Telescope Markup Language RTML. The Berkeley Lab had acquired a 30-in. telescope for astronomical research on supernovas that was installed at the Leuschner Observatory. To automate the functions of the telescope, the scientists created a telescope control system to support scheduling, dataacquisition, database management, and image analysis, thus treating the telescope as a remotely controlled robotic device. Since other telescopes were being controlled by various, similar in-house systems, it seemed appropriate to come up with a simple, standardized, high-level language that could provide a user with access to a broad range of devices – the concept for the Robotic Telescope Markup Language. Initial discussions with telescope manufacturers indicated an interest in supporting RTML commands that users could access through the Web and the Hands-On Universe Project endorsed the concept and provided into an initial plan for development. Thus, the first version was released as the Remote Telescope Markup Language. See Remote Telescope Markup Language. ROC 1. rate of convergence. 2. record of comments. 3. Regional Operating Company. See Regional Bell Operating Company. rocket camera A creative early 1900s invention for taking photographs at high altitude (close to 800 m) by attaching a camera to a stabilizing rod and equipping it with a small parachute. Rocky Mountain Bell Telephone Company An early Bell telephone exchange, established in 1883, with financial assistance from American Bell Company. It rapidly acquired the Ogden Telephone Exchange Company, the Montana Telephone & Telegraphy Company, the Idaho Telephone & Telegraph Company, and the Park City exchange. This pattern of acquisitions continued for a number of years. Rocky Mountain Telephone Company An early telephone exchange established in Salt Lake City in 1800. ROD rewritable optical disc. ROF, ROTF Abbreviations for “rolling on (the) floor” commonly used in online correspondence and text-based chats to convey mirth, where facial and tonal expression are not available to convey emotions. See emoticons, ROFL. roentgen, røntgen (symb. – R) An international unit of X-radiation or gamma radiation which is equal to

the amount of radiation which produces one electrostatic unit (esu) of charge in one cubic centimeter of dry air at 0°C and standard atmospheric pressure ionization of either sign. ROFL Abbreviation for “rolling on the floor laughing” commonly used in online correspondence and text-based chats to convey extreme laughter, where facial and tonal expression are not available to convey emotions. See emoticons, ROFL. Rogers receiver An early batteryless radio receiver first introduced in 1925 at the Canadian National Exhibition in Toronto. ROH receiver (as on a telephone) off hook. ROLC Routing Over Large Clouds. The ROLC Working Group has now merged with the IPoverATM Working Group to form Internetworking over NBMA (ION). See frame relay, Internetworking over NBMA, RFC 1735. role-playing game RPG. This style of game is particularly popular on computer networks as it can be implemented with simple text interfaces and lends itself to including people who are anonymous in the sense that the players, located at different terminals, cannot see one another. In general, game-playing is discouraged on computer terminals in educational institutions (and businesses) unless it directly relates to course work, but roleplaying games have been tolerated since many of them require that players and playmasters use a certain number of programming commands and algorithms to set up the game and participate, thus justifying its educational value. Role-playing games can be addictive, however. More than one role player has failed a school term due to overindulgence. Roll About A commercial, self-contained videoconferencing unit which includes the monitor, camera, microphone, and other components on a stand that can be moved from one office to another as needed. ROM 1. See read only memory. 2. rough order of magnitude. Rømer, Ole (Olaf) Christensen; Rümer, Ole Christensen (1644-1710) A Danish astronomer, physicist, and scientific instrument-maker who, in 1675, demonstrated the velocity of light as 11 minutes per astronomical unit (AU) based upon observations of the planet Jupiter and its moon Io. In the 1660s, he was entrusted with the editing of the great scientist Tycho Brahe’s manuscripts. He was appointed in France by Louis XIV to tutor the Dauphin in astronomy, and also was appointed as the Astronomer Royal at the Danish court of Christian V. He invented a new type of thermometer and communicated some of his ideas to D. Fahrenheit in the early 1700s. In Denmark, he introduced a new system for numbers and weights in which the concepts of weight and length were brought together. Ronalds, Francis (1788-1873) An English researcher who was one of the earliest inventors of telegraph technology, Ronalds developed a frictional telegraph, using above-ground copper wire, that he demonstrated ca. 1816, more than two decades before Wheatstone and Cooke in England and Samuel

Morse in America developed the first widely known telegraph systems. Ronalds also experimented with other types of telegraph systems. Charles Wheatstone corresponded with Francis Ronalds around the time he developed a telegraph with W. F. Cooke. The British Navy failed to adapt Ronalds’ telegraph system, choosing instead to continue their “tried and true” semaphore system of signaling. See Schilling, Pavel Lvovitch; Morrison, Charles; Wheatstone, Charles. Røntgen, Wilhelm Konrad (1845-1923) A German physicist and educator who developed the vacuum tube (1895), the fluoroscope, and pioneer experimental studies in X-ray emissions in industrial radiography and medical radiology. He was the first recipient of the Nobel prize in physics. The roentgen unit of X-radiation is named after him. See roentgen, X-rays. root mean square (abbrev. rms) The effective value of a quantity in a periodic circuit, measured through the duration of one period. root name server On distributed computer networks, name servers provide a means to administer the transmission and routing of data among source and destination computers. Name servers are a type of address allocation and identification tool. Initially, the name servers handling root zones (“.”) also handled top-level domains (TLDs) such as the .com domains. However, due to the growth of the Internet and differences in administration of root name servers and TLD servers, it was proposed in the mid1990s that a distinction be made between the two groups as the performance needs of root servers were felt to be greater than for many other types of servers. It was further proposed that requirements be formally laid down for root name servers so that vendors and implementors would have appropriate tools for handling the more stringent requirements of root name servers. See Domain Name Server, RFC 2010. ROSAT Røntgen Satellite. A research satellite that has expanded knowledge of the universe and past events in this galaxy by aiding in discovering local hot X-ray plasma. ROSE See Remote Operations Service Element. Rosenblueth, Arturo A scientist who collaborated with Norbert Wiener in investigations in artificial intelligence and self-organizing systems, much of which was documented in Wiener’s book on cybernetics. rotary dial A circular dial mechanism typically activated by placing a finger (or pencil end) in one of a series of punched out holes, and turning (dialing). The mechanism springs back to its original position after each selection. The alphanumeric selections are displayed under each associated hole. Turning the dial activates the telephone carrier’s electrical loop for specified intervals that form a simple code to identify the number dialed. Dials were not always circular. Some of the earliest dials consisted of levers, resembling the front of a small slot machine. Rotary dials are normally associated with pulse dialing signals. Rotary phones are steadily being

R

superseded by pushbutton phones, especially since automated systems require touchtone phones in order to use their services. See pulse dialing, tone dialing, keypad, touchtone phone. rotary hunt A means of routing selection for a call that has been placed in a multicircuit hung group. The system cycles through circuits, hunting for an idle one through which it then routes the call. rotary switch A commercially successful electromechanical telephone switching system developed in the AT&T labs in the early 1900s, based on Lorimer one-step selection concepts and incorporating a permanently rotating motor. These were installed in Europe as a result of an International Telegraph and Telephone buyout of Western Electric’s International division in 1925. See Lorimer switch, panel switch, rotary switch. ROTF, ROTFL Abbreviations for “rolling on the floor” and “rolling on the floor, laughing” which are often used in online chat rooms and email correspondence. See emoticons, AFK, IMHO. ROTL Remote Office Test Line. A means of automatically testing telecommunications trunk lines from a remote location through a hardware switch. The remote testing may be conducted manually, through a control unit, or through automated Centralized Automatic Reporting on Trunks (CAROT). Round Robin RR. A scheduling or resource-allocation system that “divvies” up tasks or resources more or less equally among all the participants in a generally cyclic pattern. Thus, a Round Robin system in a classroom with only one computer could be set up to allocate an hour to each student in a repeating rotation through the school year. In general, Round Robin systems deal with discrete events or resources that do not overlap (though there may be exceptions). A chain letter extended by each member in the chain and returned to the source when it is completed is another example. As a more complicated example, the duplicate bridge card game is played on a Round Robin basis so that each person gets to play a set with each other player as his or her partner, against every other set of players so that each dealt hand is played twice (assuming eight players and thus two tables). This enables the duplicate playing of each dealt hand so that the relative strategies of each of the two teams can be evaluated, and overall scores can be given to individual players, even though bridge is a partnership game. Many sports use Round Robin systems (e.g., tennis) and Round Robin tournaments are common in bowling alleys and pool halls. They provide each player with the opportunity to play with every other player. Round Robin systems have been used by humans for centuries (maybe even tens of thousands of years) for scheduling work and play and for providing fair access to resources on a rotating basis. They have even been used to disguise the beginning or end of a circular process or the ringleader in a group of people. While the concept is ages old, the term itself historically appears to have been applied to documents wherein signees signed their names in a circle

so as to obscure the identity of the leaders or to give equal weight to the input of all the participants. These documents were especially associated with sailors although they were likely also used by other groups of disgruntled workers or citizens to put forth complaints, in the days when opposing opinions (heresies) could result in death or imprisonment. The Round Robin system, as we now understand it, is at the heart of many scheduling algorithms that use the same general cyclic event-driven concept. Round Robin systems are used to allocate computers, modems, printers, and many other heavily accessed systems that are expected to be allocated on a more-orless equal basis. They are especially useful when setting up paired Round Robin activities for large numbers of people or multiple Round Robins intended to take place concurrently. A Round Robin scheduling chart that would take hours to create by hand can be generated on a computer in a few minutes. Other common Round Robin applications include • token passing in a Token-Ring network. The token moves around in a circular topology to each machine in the ring, • network routers such as the Cisco CSS 11800, that use Round Robin algorithms to handle data flow, • telemarketing systems that assign incoming calls to available agents on a Round Robin basis, especially in situations where the agent is earning a commission and wants a fair share of the calls, and • computer operating systems running multiple processes in which the computer moves on to the next process if the previous process has completed, but may pre-empt a process if it is not completed after a certain amount of time. Weighted Round Robin schedules take into account the unequal capacities of different participants or processing systems. For example, in a telemarketing firm, if there is a crackerjack sales representative with seniority who always closes a sale, the Round Robin system of assigning incoming calls might be weighted to go to this sales representative . more often than the other agents. Thus, the sales representative is happy and stays with the company and the company is happy because profits are maximized. Weighted systems tend to have the advantage of being more effective in systems with unequal members, but also have the disadvantage of being controversial when they involve people rather than computing processes. See queuing, Token-Ring network. Round Robin, DNS A load-balancing resourcesharing system implemented on the Internet through recent version DNS/BIND 4.9 (Domain Name System with BIND) that arose in part because of heavy access to favored sites on the World Wide Web. This enables a cluster of servers to provide client requests to a very large number of users by allowing address records to be duplicated for a host, with different Internet Protocol (IP) addresses. The name server can

then rotate in a Round Robin fashion through names with multiple address (A) records. The DNS/BIND implementation is not robust in terms of handling server failures, as the Round Robin system is inherently intolerant of missing links in the pool of resources, but other programs can be used with DNS/BIND to handle possible server failures. See Berkeley Internet Name Domain, Domain Name System, Round Robin. round trip delay RTD. A general phrase that refers to a number of aspects of network physics and behavior that contribute to delays in the full path back to the sender. It is a statistical measure useful in installing, configuring, and tuning networks. Some delays are evaluated in relation to what the elapsed time should theoretically be and some are evaluated relative to a test suite of alternate configurations. Sources of delay include the physical length of the path, the media and protocols used to send the information, data processing, compression and errorchecking, data congestion, and even the speed of light itself. route 1. n. Path taken by data or other transmissions. See traceroute. 2. v. To delineate a communications path. This may be fixed before the transmission or may be dynamic according to availability and load levels evaluated en route. See hop-by-hop. Route Access Protocol RAP. An open distance-vector routing protocol for distributing routing information through Internet-connected systems ranging from large Internet Service Provider (ISP) systems to local area networks (LANs). The protocol was submitted as an RFC by R. Ullmann in 1993. The Route Access Protocol is a generalized protocol, making no distinction between external and internal networks and is designed to accommodate both small and large systems. RAP is internally IPv7-compliant but is downwardly compatible with IPv4 networks. Distance-vector routing was selected for RAP to promote scalability. The protocol operates on TCP port 38 through a symmetric connection between RAP ports. Through peer discovery, it may also be used on User Datagram Protocol (UDP) port 38. RAP propagates routes in the opposite direction to the path of the datagrams using the associated routes. Source restriction may be invoked to provide a certain measure of security and must be added to routes if security filters have been established in the Internet Protocol (IP) forwarding layer. Once a connection is established, RAP peers need only send new or changed routing information. The routing information is purged by each system when the session ends. See RFC 1476. route diversity An architecture providing a number of options in routing a transmission. This may be organized in a number of ways, depending upon the type of network, the load on the network, and the existence and quantity of redundant circuits. Route diversity can be as simple as an extra line to take the load if the primary line goes down or as complex as dynamic hop routing in a distributed computer network.

route flap, router flap A fault condition in which changes in routes propagating across a network (usually from losing one or more nodes) exceed the capacity of a router’s processor and memory to cope with the change, and consequently impact its ability to route. Routers are generally selected to well exceed the number of routing paths expected to be needed to prevent this serious problem. router 1. A device or mechanism for selecting a path. 2. In a simple network, an interface device which selects a path for the transmission packets. In layered networks, the router typically functions at layer two or layer three, depending upon the degree of automation and “intelligence” built into the router. There used to be somewhat of a distinction between routers and switches, but switches are becoming so sophisticated that the distinction is disappearing. Routers frequently include routing databases, in addition to algorithms to dynamically select routes. See bridge, switcher. router, ATM In ATM networks, a router delivers and receives Internet Protocol (IP) packets to and from other systems, and relays IP packets among systems. Routers vary in sophistication, with some able to contribute significant network management functions, such as priority and load balancing. They can be protocol-dependent or protocol-independent. Also called an intermediate system. See LIS. router, Frame Relay A Frame Relay-capable router has the ability to encapsulate local area network (LAN) frames in Frame Relay-format frames and feed them to a frame relay switch, as well as receiving frame relay frames, and stripping the frame relay frame to restore the information to its original form, passing it on to the end device. With improved technologies, the distinction between routers and bridges is lessening. Even switches now have many of the capabilities of routers. See bridge, gateway, switch. routing Selecting or establishing a path. In telecommunications, the path may be used to transmit supervisory signals and data (either together, separately, or over separate paths). Routing may be static or dynamic. Dynamic routing is typically used in larger networks, especially those with individual systems in the path that may or may not be available at any given time. Static routing is suitable for small or local systems, or for those carrying priority or secured transmissions. routing aggregation An administrative tool for organizing and optimizing the use and availability of routes to deal with the continually rising demand on networks. Users are encouraged to return unused addresses, and old addresses are assigned prefixes so multiple routes can be aggregated into one. Routing Arbiter Database RADB. A routing database established by the Routing Arbiter project. One of several databases in the Internet Routing Registry. Routing Arbiter Project A National Science Foundation-funded project given the task of coordinating routing for the new NSFNet architecture in cooperation with a number of educational and private business

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concerns. Route Servers were to be installed at connection points to reduce the need for peering. Due to NSFNet legacy database information, a number of large providers have shunned the Routing Arbiter and the project has changed to a service available through some of the Public Exchange Points. See peering. routing code 1. In telephone communications, the area code. 2. In U.S. postal communications, the last four digits of the ZIP+4 code. 3. In networks, the data parsed by the router or switcher to establish a path to the intended destination. routing computations, routing algorithms Mathematical schemes to compute efficient routes through a network. The algorithms may be straightforward if the topology and size of the network are known and are relatively stable. The situation is more complicated on the Internet, which is extensive, encompasses many different types of configurations, and which changes constantly as networks are added or changed. routing domain RD. In ATM networking, a collection of systems that have been grouped topologically within one routing system. routing information base RIB. A static or dynamic table of routing paths maintained within a router or a processor/memory system associated with a router. In distributed networks, in which systems may be added or removed dynamically, RIBs are generally updated dynamically as the information about the changes propagate through the network. Routing Information Protocol RIP. A very common routing protocol from a family of protocols known as the Interior Gateway Protocols (IGPs). RIP evaluates the path between two points in terms of hops between the source and destination points. Each hop in the path is assigned a value which may be incremented by the router and entered into the routing table. The Internet Protocol (IP) address becomes the next hop. In order to prevent continuous routing loops, a limit is defined for a path’s hop count. If the routing table entry exceeds the maximum hop count, the destination is considered unreachable. See RFC 1058, RFC 1723. Route Servers Specialized servers from the Routing Arbiter project intended to hold clearinghouse routing information in a Routing Information Base at each network interconnection point in order to eliminate, or at least reduce, the need for peering. These servers are not intended to actually transmit the traffic, but serve to handle the flow of information concerning pathways. routing table, data network In data networks, a table detailing paths to specific Internet Protocol (IP) addresses. With the explosive growth of the Net, the number of paths, and hence the size of the tables, can become very large. Primary routers sometimes list more than 25,000 routes and the routers themselves must be designed to keep ahead of capacity. Discussions are ongoing as to the benefits and problems in various assignments of routing paths, with providerbased routing being favored due to greater ease of implementation, and geographic-based routing

proposed because it has less of a tendency to concentrate power in the hands of a few large providers. routing table, telephone network In telephone communications, routing tables serve to record and provide information for the processing of incoming calls. Thus, calls may not just go to a particular caller or workstation, they may be directed to automated voice services, voicemail, queued holds, recordings, etc. They may require the capability of stepping back through the route as well, depending upon the sophistication of the system and the selections available to the user. Routing Table Maintenance Protocol An AppleTalk network routing protocol that is based upon Internet Protocol (IP) Routing Information Protocol. RTMP is a transport-layer protocol that manages routing information within an AppleTalk router and facilitates the exchange of routing information among AppleTalk routers to help keep the information current. Hop count is used as the routing metric for RTMP. The RTMP table includes information on the hop count to a destination network, the appropriate router port, the next hop router address, the status of the routing table entry, and the network cable range of the destination network. See Routing Information Protocol. Routing Table Protocol RTP. A network communications routing protocol from Banyan System, Inc., VINES (Virtual Networking System). RTP is based upon Internet Protocol (IP) Routing Information Protocol. The protocol facilitates the distribution of network topology information among the various servers and enables servers and routers to identify others nearby. It works in conjunction with other protocols such as the Address Resolution Protocol (ARP). See Routing Information Protocol. routing update Information provided by a router as to network configuration, and, in some cases, costs associated with use of particular routes. Routing updates can be scheduled to be automatically sent out at specified intervals, and are typically broadcast if significant network configuration changes have been made. row 1. Generally, about three or more elements more or less lined up in one directional plane. 2. In a 2D system, the grouping, between the left and right bounds, of more or less horizontally aligned elements arranged within a grid or tabular format. This meaning of the word is commonly used to describe screen locations or positions within a spreadsheet or printed medium. See column. Royal Society An independent national academy of science, founded in 1660 to support the British scientific community. The Society funds research, stimulates international communication among scientists, hosts conferences, produces reports and journals, and maintains one of the most remarkable historic archives of scientific endeavor in the world dating back to 1470 (which includes records and photos of many of the major advances in computing and telecommunications). Among its publications is the Philosophical Transactions of the Royal Society

which was first printed in 1665. The society has recognized scientific achievement through awards since 1731. Current projects of interest which the Society helps support include AIDS research, byproducts of nuclear technologies, genetics and stem cell use in medicine. http://www.royalsoc.ac.uk/ RP See Restricted Radiotelephone Operator Permit. RPC See remote procedure call. RPE radio paging equipment. Systems that use radio waves to send a signal to a receiving unit. The signal may be a simple pulse to trigger a light, vibration, or sound, or it may contain information that can be printed out on a text-capable paging device. RPG 1. Report Program Generator. A computer programming language for processing and displaying large data files. 2. See role-playing game. RPM Remote Packet Module. RPN reverse Polish notation. A mathematical notation system in which the values to be operated upon are entered first, followed by the operation to be performed. In other words, multiplying two numbers would be done like this: 2 [enter] 4 [enter] * (times) which would display the result as 8 This system is used on HP calculators and others commonly used by the scientific community. Calculators marketed to the nonscientific community tend to use regular notation as follows: 2 [enter] * (times) 4 [enter] = (equals) which would display the result as 8 Those who use one system often curse when they encounter the other, because it necessitates shifting mental gears to enter data and operations in the correct order. RPOA See Recognized Private Operating Agency. RPOP Remote Post Office Protocol. See Post Office Protocol. RPS See repetitive pattern suppression. RPT repeat. RPV See remotely piloted vehicle. RQS See Rate Quote System. RR 1. radio regulation. 2. railroad 3. return rate. 4. See Round Robin. 5. rural route. RRSF RACF remote sharing facility. See remote access control facility. RS 1. radio satellite. 2. recommended standard. See RS-232 for an example using this prefix. 3. remote station. 4. reset. 5. Royal Society. RS-1 Along with RS-2, the first USSR amateur satellites, launched in October 1978. RS-232 Recommended Standard 232. A decades-old single-ended standard for serial transmissions introduced in the early 1960s. RS-232 is widely supported on desktop computers and other devices commonly used for communicating with modems, remote terminals, and printers. RS-232 specifies the electrical and physical characteristics of the connection. The most common implementation is RS-232-C (which is often transcribed as RS-232c for brevity) and many in the industry mean RS-232c when they say RS-232. The RS-232c specification defines a way to connect data terminal equipment (DTE) with data circuit-

terminating equipment (DCE). Most systems support RS-232c through a 25-pin D connector (DB-25), although fewer pins can be used to implement the specification, and 9-pin D connectors are sometimes used (or 25-pin connectors with some of the pins unconnected). A few systems specify more than 11 or 12 pins (pin 12 is not part of the spec. but some vendors assign a proprietary signal to the pin). The basic RS-232 pinouts more-or-less commonly used by manufacturers are as follows. The most important pins for establishing a basic connection are noted with asterisks and a minimal connection would require transmit, receive, and ground. A null modem cable can be made from an RS-232 cable by swapping pins 2 and 3 on one end of the connection. This enables two locally connected computers to network through the cable with suitable communications programs running on each system. The initial RS-232 standard was superseded in 1987 by the standard defined by the Electronic Industries Alliance (EIA) as EIA-232-D, which was followed in 1991 by the EIA/TIA-232-E. RS-232c is similar to the ITU-T Recommendations for V.24 and V.28. The single-ended handling of voltage in the RS-232 specification limits transmission distances to about 50 feet or so. For longer distances, it is preferable to use balanced pair voltage formats like RS-422, to transmit up to about 4000 feet. See RS-422. See EIA Interface Standards for a list of common standards. See Selected Overview of Recommended Standards for Communications chart for a summary of RS data/ video communications standards. Pin

Abbrev.

Function

1 2* 3* 4*

GND TxD RxD RTS

5*

CTS

6

DSR

7 8

GND DCD

9 10 11 12 15 17 18 20 22 24

+12 -12 AUD

earth ground transmit data receive data request to send (control signal) clear to send (control signal) dataset ready (signals that the device is on) signal ground data carrier detect (signal that carrier is on) DC voltage (Amiga) DC voltage (Amiga) audio out (Amiga)

AUD DTR RI

transmit clock receive clock audio in (Amiga) data terminal ready ring indicator auxiliary clock (provided by some vendors for local connections)

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Selected Overview of Recommended Standards (RS) for Communications Designation RS-170

Type

Description

Monochrome Video: a standard for analog black and white (monochrome) video adopted in North America and Japan that was prevalent until color standards became dominant. The format evolved from historic broadcast specifications developed in the 1930s. RS-170 carries both timing and image information on a single signal. It formed the basis for broadcast television for many years. The format is still widely used in monochrome security cameras where a higher-resolution picture or lower installation cost are considerations. For television, RS-170 has been superseded by RS-170a color NTSC systems and is now gradually being superseded by RS-343 and digital video formats. RS-170 broadcast standards specify 525 horizontal lines displayed as 2:1 ratio interlaced frames. These are alternate odd- and even-line half-frames that combine perceptually to create the full frame image, generating the effect of 60 frames per second. The range of the relative intensities of individual ‘points’ in the display is from no light (black) to full light (‘white’), depending upon the voltage level. Not all of the lines are used for display; some aid in synchronization. Since there is no color signal (chrominance) to process and render, it is generally less expensive to manufacture monochrome systems. RS-170 signals are typically transmitted through 75-ohm well-shielded coaxial cables. Europe uses a standard similar to RS-170 called CCIR. It differs in that it supports a higher vertical resolution (625 horizontal scan lines) and operates at the rate of 25 frames per second. See NTSC, RS-170a, RS-343. RS-170a Analog Color Video: an Electronic Industries Association (EIA) standard for analog color video adopted in North America and Japan in 1953. Consumer RS-170a-based televisions and video editing systems superseded RS-170 (monochrome) in the 1970s. RS-170a is also gradually superseding RS-170 standards for security cameras. Eventually, RS-170a will be replaced by digital video, but it is still prevalent in composite National Television System Committee (NTSC) systems. The original RS-170 (monochrome) format specified 525 horizontal lines for display and synchronization purposes. The RS-170a standard was intended to support color while being downwardly compatible with the large installed base of monochrome systems expected to remain for some time after the color standard was introduced. There was also some consideration of video tape recorders that were becoming prevalent in the production and broadcast industries. RS-170a specified 1050 lines due to the four color fields needed for a frame through subcarrier repeats, but the effective resolution is compatible with RS-170, that is, 525 horizontal lines, 485 of which are displayed. RS-170 RGB refers to video signals using the red-green-blue color model (e.g., many computer monitors) timed for compatibility with RS-170 specifications See RS-170, RS-343, RS-343a. RS-330 Monochrome Video: an analog, monochrome composite video standard adopted in North America and Japan primarily for closed-circuit television systems. It supports a resolution of 525 horizontal lines at 60 frames per second. It is similar to RS-170 but does not require equalizing pulses. RS-343/RS-343a Monochrome Video: an analog noninterlaced monochrome video standard used for nonbroadcast high-resolution cameras (625 to 1023 scan lines, not all of which are displayed), especially security cameras for monitoring and recording purposes. Many RS343a cameras also output RS-170 for downward compatibility. Terminated 75-ohm coaxial cables are traditionally used for transmitting the signal but RS-343a is now also supported through RS-422 and fiber optic composite and digital RBG video links for wideband TV, medical video, military monitoring, and computer graphics applications. RS-343a is the monochrome version – which is confusing, since RS-170 and RS-170a are, respectively, monochrome and color. See RS-170, RS-170a. RS-328 Facsimile Communications: a standard for facsimile transmissions introduced in 1966 to help improve interoperability among facsimile equipment from different manufactures which were, at that time, operating on a number of proprietary schemes. This came to be known as the Group 1 standard and other Group x formats have followed. Standardization has aided in implementing fax capabilities on other systems, including fax modems. See facsimile.

Designation RS-366

RS-250c

RS-422

RS-423

RS-449

RS-485

RS-530

Type

Description

Parallel Dialing: a parallel dialing standard for high bandwidth communications such as videoconferencing. RS-366 has been subdivided into Type I, II, and III. RS-366 has been implemented on a number of types of links, including RS-449, RS-530, V.25bis, and V.35 modem interfaces. It is compatible with RS-232 electrical specifications and is commonly transmitted through a DB-25 connector. It has further been implemented on fiber optic modems transmitting data at speeds up to 56 Kbps per channel and is also applicable to video transmissions over ATM networks (e.g., for switched virtual circuits). There are commercial products to convert between RS-366 and Hayes AT commands. They resemble traditional modems in shape and size, with LEDs to signal various indicators. These converters enable a regular asynchronous modem to be used in conjunction with an RS-366 interface. Serial Communications: the most recent version of an analog color video standard for establishing acceptable performance in the transmission of broadcast-quality signals through various distances (short-, medium-, and long-haul) through a variety of wired and wireless links. The 250 series was first established in the 1950s. Unlike other video standards that specify resolutions, frame rates, and synchronization levels for displaying images, this one concerns itself with the delivery of a “clean” signal in terms of the signal-to-noise ratio, phase, gain, and other signal quality characteristics. Short-haul RS-250c requirements are easier to meet now that fiber optic transmission links are available. High-speed Serial: a widely-used balanced/differential voltage twisted-pair standard for high-speed point-to-point serial transmissions. It is backwardly compatible with RS-232 but is faster, up to 100 Kbps, and can be transmitted over longer distances, up to about 4000 feet. RS-422 can be configured to support either software or hardware handshaking. The standard is not tied to any specific attachment device configuration, but is commonly implemented through cables with DB-9, DB-25, or 8-pin mini-DIN connectors. RS-422 is not inherently a multidrop standard, but 4-wire, half-duplex links can be constructed to provide some of the benefits associated with multidrop formats such as RS-485. See RS-485. See differential cable, RS-232. High-speed Serial: a balanced/differential voltage twisted-pair serial transmissions standard backwardly compatible with RS-232, but with multidrop capabilities and transmission distances of up to 4000 feet. Compared to RS0232 and RS-422, this standard has not been widely implemented. High-Speed Serial: a balanced/differential voltage twisted-pair standard for high-speed synchronous data transmissions. The signaling is associated with specific pin assignments for DB-9 and DB-37 connectors. This has been superseded by RS-530. See RS-232, RS-530. High-Speed Serial: a widely used balanced/differential voltage pair standard, downwardly compatible with RS-422, for high-speed serial transmissions, up to 100 Kbps. It has become popular in industrial and telecommunications applications for connecting multiple peripherals (printers, industrial fabricators, etc.) through multidrop transceivers/transmitters. Up to 64 devices may be connected, 32 for each multidrop line. RS-485 supports drivers with higher voltage output ranges than RS-422. It can be used in half-duplex or full-duplex mode, but is commonly implemented as half-duplex. RS-485 may or may not need to be terminated, depending upon the configuration. As with RS-422, the format is not tied to any particular type of connector. See differential cable, RS-422, RS-232. High-Speed Serial: a balanced/differential voltage twisted-pair standard for high-speed serial transmissions that supports RS-422/RS-423 and the oldie-but-prevalent RS-232. It is specified for a DB-25 connector. There are commercial devices to convert between RS-530 and the older RS-232 serial format that is still supported on many computers. There are also cables to convert between RS-530 and V.35, X.21, and RS-449/RS-442 formats. RS-530 can be supported over high-speed, point-to-point fiber optic modem links for distances of up to 30 km. Thus, a system with an RS-530 interface can connect through twisted-pair cable to a fiber optic modem, which then transmits to another fiber optic modem and twisted-pair at the other end of the fiber link. RS-530 supersedes RS-449.

R

RSA See Rural Service Area. RSA An academic security research facility within the corporate structure of RSA Security Inc. The lab provides state-of-the-art expertise in cryptography and security technology to RSA and its customers. The lab personnel were active participants in the IEEE P1363 project specifying standards for public key cryptographic systems. See Public-Key Cryptography Standards. RSA Security Inc. A prominent data security distributor providing products that aid companies in developing security/trust products and processes, especially for electronic commerce applications. The name is based upon the originators of the RSA cryptosystem, Rivest, Shamir, and Adleman. See MD series, RC6. RSB repair service bureau. RSC 1. See remote switching center. 2. repair service center. RSGB Radio Society of Great Britain. RSS 1. remote switching system. 2. root sum square. A statistical calculation that is useful in assessing errors such as signal distortion. RSU remote switching unit. RSUP See Reliable SAP Update Protocol RSVP Internet Reservation Protocol. An extensible, scalable protocol designed in the mid-1990s to provide efficient, robust ways to set up Internet-integrated service reservations, RSVP became an Internet standard in 1997. It has primarily been promoted by commercial interests, as it makes it possible to establish priority connections through reserved bandwidth, a feature of interest to large competitive business network users. RSVP is appropriate for multicast applications, although it supports unicast as well. RSVP interfaces existing routing protocols rather than performing its own routing. The RSVP is used by a host to request a specific Quality of Service (QoS) from the network. RSVP attempts to make a resource reservation for the data stream at each node through which it passes. RSVP communicates with two local decision modules: admission control and policy control, to determine whether the node has sufficient resources to supply the QoS, and whether the user has administrative permission to make the reservation. One of the difficulties in implementing RSVP has been assessing fees for connections across more than one network. Some opponents of the system fear the establishment of “elite” Internet users based on economics rather than on quality of information or services offered. RSVP development has continued since 1995 as RSVP2. See STII. RT 1. radio telephone. 2. See realtime. 3. See remote terminal. 4. reorder tone. 5. routing table. 6. See run time, runtime. RTB regional test bed. A regionally allocated location, lab, or systems setup that enables designers, developers, or implementors to test their systems. Test beds can provide information such as whether the systems work, whether they work reliably, and whether they work compatibly with other systems. Test beds are important in almost every industry,

since testing can be a complex activity involving specialized equipment and skills. Most designers and developers don’t have the resources to set up individual test beds. Test beds are often funded by universities, consortiums, and government grants, especially when they are designed to test products that have a big chance of promoting the common good or being commercially successful and widespread. RTC 1. realtime control. 2. runtime code. 3. runtime control. RTCA See Radio Technical Commission of Aeronautics. RTCP Real Time Conferencing Protocol. RTD 1. realtime display. 2. See round trip delay. RTDNA See Radio-Television News Directors Association. RTDNF See Radio-Television News Directors Foundation. RTE remote terminal emulation. See remote terminal. RTF 1. See Radio Terminal Function. 2. See Rich Text Format. RTFM An abbreviation for “read the freaking manual” used on public forums on the Internet, when a user asks a question which has been asked and answered hundreds of times and is clearly answered in the appropriate documentation, or FAQ. An exhortation for the user not to be lazy, to look it up before using up people’s valuable time in asking an obvious question. See Frequently Asked Question. RTFP read the fine print! An admonition to investigate all the legal ramifications before committing to something. RTL 1. Radio Television Luxemburg. News, sports, comedy, and community programming. 2. runtime license. RTM 1. realtime/runtime monitor. 2. runtime manager. RTML 1. See Real Time Markup Language. 2. See Remote Telescope Markup Language. 3. See Rich Text Markup Language. 4. See Robotic Telescope Markup Language. 5. See Runeberg Text Markup Language. RTOP realtime operating system. RTP 1. See Rapid Transport Protocol. 2. realtime protocol. 3. Realtime Transport Protocol. 4. See Routing Table Protocol. RTTY realtime teletype. See teletypewriter. RTS 1. realtime system. 2. Request to Send. Flow control, typically used in serial communications, which is an output for DTE devices and an input for DCE devices. See TxD, RxD, CTS, DSR, DCD, DTR, RS-232. 3. remote tracking station. RTSP See Real Time Streaming Protocol. RTU 1. remote telemetry unit. A system that enables a device, such as a communications satellite in orbit, to be controlled from a remote location, such as an Earth station or space shuttle. RTUs can typically be used to orient and move the remote system by activating and controlling various motors, gyros, and other positioning systems. The telemetry unit may or may not have feedback capabilities. If the RTU is

one-directional, then coordinates or instructions are usually sent with the hope that they will work or with the understanding that another system (such as a shuttle or telescope) will monitor the effect of the settings. If the RTU is two-directional, various types of information will be relayed back to the RTU from the remote system and corrections made, if necessary. 2. remote terminal unit. A device to activate, control, or query a system in another location. Remote terminal units range from simple to sophisticated but, in general, refer to a remote terminal earmarked for a particular purpose, such as testing and diagnostics in a network system. A small-scale remote terminal is similar in concept to a television/ VCR remote control but usually provides more control and better processing capabilities than typical remote controls. Older computers are often used as remote terminal units to control security systems and home automation systems (heat, lights, etc.). RTV realtime video. Video that appears as natural movement, usually with at least 20 frames per second, and which further may be a live broadcast as opposed to playback from stored information. On the Internet, a technology called streaming video is becoming popular. In the past, most animations were developed, compressed, and stored in an Internet-accessible location for the user to download and play back on his or her local system. However, streaming video enables the user to link into a live data stream and watch the action as it happens. This is becoming especially popular for live news broadcasts, especially by stations that cover disaster-related news and popular sports events. RU 1. In packet networking request unit, response unit, request/response unit. See basic information unit. 2. receive/receiving unit. RUA Remote User Agent. A software agent that acts on behalf of a client making a request or supplying information from a remote terminal. See User Agent. rubber bandwidth jargon A communications channel whose bandwidth can be dynamically altered, that is, it can be changed without terminating and reinitiating the transmission. This colorful phrase apparently originates from Ascend Communications, a supplier of networking-related products, to describe characteristics of an inverse multiplexing system. rumbatron A term used by William Hansen for pioneer cavity resonating devices in the 1930s. The term was subsequently adopted by Russell Varian, in collaboration with Hansen, to describe a Rumbatron Oscillator, the germinal idea for the Klystron tube. Note that the author was not able to find a firsthand reference as to whether Hansen spelled it rumbatron or rhumbatron. For consistency with Varian’s adaptation of the term as Rumbatron Oscillator, it is spelled without the “h.” See Klystron. Rumbatron Oscillator See Klystron. run v. To initiate and execute a software program, or linked suite of programs which form an application. In operating systems that enable the user to execute programs from a shell command line interface, there may be a distinction between typing the name of a program (to run it) or typing run followed

by the name of the program. For example, in AmigaOS, the former means of executing the program runs it in dedicated mode, while the latter means, with the run command, executes it in multitasking mode so that other programs may also be run concurrently. run length encoding RLE. A lossless data compression technique that works well with data that include repeated sequences. The repeated sequences (white spaces in a document, a single background color in an image, etc.) are replaced with a code that indicates that what follows is a string of the same character of a particular length. If run length encoding is used on data with little or no redundancy, the encoded file may be longer than the original. Rundgren, Todd A multimedia recording artist who has managed to stay at the forefront of emerging interactive entertainment technologies, synthesizing the new capabilities in media into video and sound. Rundgren began programming microcomputers in the late 1970s, adapting Macintoshes, Amiga Video Toasters, and other systems to many new creative venues, producing new types of music albums, computer-generated rock videos, and interactive TV entertainment concerts. Since the mid-1990s, Rundgren has been president and CEO of Waking Dreams, which develops, licenses, and distributes products and services which originate from creative and undervalued ideas. run time The time during which a software routine or application executes overall. This can easily be confused with “runtime” which refers to CPU cycles and computer processing time. In contrast, runtime is the overall length of time a job might take from submission to completion. Thus, a database query might take 5 minutes of run time or execution time to provide a result, yet require only 3 seconds of CPU runtime to execute. To confuse matters further, many people use these terms interchangeably and run time licenses are often spelled “runtime.” See runtime. Runeberg Text Markup Language RMLT. Project Runeberg is a project to publish Nordic literature on the Internet. RTML is an extended subset (identified by the <spärr> extension) of Hypertext Markup Language (HTML) for maintaining the Project Runeberg documents. runtime In computer processing terms, this is the duration, that is, the CPU time (usually expressed in cycles), used to execute a routine or program. A process that takes 5 minutes for the user might require only 3 seconds of CPU runtime because computer time is often spent pondering or waiting for peripherals. Runtime is a reasonably objective value with comparative benefits for optimizing software algorithms and practical billing applications for shared access systems. See run time. run time license A onetime, per-use, or other distribution license granted by a software developer to allow a vendor to include the licensor’s algorithms, usually for inclusion in an enduser product (often called a “customer application”). To help understand the distinction, imagine a software company selling an image library created with a software application

R

like Adobe Photoshop or Fractal Design Painter. A runtime application isn’t necessary because the output files from the paint program don’t include code from Photoshop itself. On the other hand, if you sold an image processing program that incorporated some of Photoshop’s paint tools, you would require permission from Adobe, in the form of a runtime license, to allow an enduser to have access to these tools. See run time. rural automatic exchange RAX. An automatic telephone exchange that didn’t require a human operator to patch the connections, intended for rural communities. Siemens is credited with installing the first 40-line RAX in the U.K. in 1921. Radio-equipped, solar-powered RAX systems were introduced to rural areas in India in 1985. Rural Local Broadcast Signals Act H.R. 3615. An act passed by the U.S. House of Representatives in April 2000 that extends loan guarantees to companies providing local television broadcasting through satellite transmissions. H.R. 3615 amends the Rural Electrification Act of 1936 to ensure access to TV broadcasting by multichannel video providers to all households in underserved areas that desire the service by December 31, 2006. The Act was felt to be important because weather, emergency, and other crucial information was often disseminated through broadcast television, in addition to educational and entertainment programming. Other services, such as Internet access, may also be offered. Satellite access also serves as a competitive alternative for rural consumers. The Act will serve to improve access to more than 6 million satellite dish owners in rural areas. However, that still leaves the other 50% unserved and in need of support in having access to the same programming as urban subscribers. The Act was placed on the Senate calendar in May 2000. See Local TV Act of 2000. Rural Local Television Signals Act U.S. regulations adopted in 1999 as part of the Satellite Home Viewer Improvement Act (SHVIA) for delivering local broadcast television signals to satellite television subscribers in unserved and underserved local television markets, a spectrum that would otherwise be allocated to commercial use. There was controversy regarding this issue and whether the terms of SHVIA sufficiently addressed the problem of rural access. These discussions lead to the Rural Local Broadcast Signals Act and the LOCAL TV Act of 2000. See Rural Local Broadcast Signals Act, LOCAL TV Act of 2000. Rural Service Area RSA. An administrative designation used by many commercial and public service organizations, including telecommunications providers and public libraries. For telephone service, regions not defined as Metropolitan Service Areas (MSA) are in the category of Rural Service Area, which includes smaller cities (usually under about 50,000 inhabitants), towns, and rural regions. The Federal Communications Commission has recognized over 300 MSAs and over 400 RSAs in the U.S. and has further used this designation to license non-MSA cellular carriers.

Libraries use a similar categorization to define their public service regions as urban, suburban, and rural service areas. The rural service area is often defined as those areas outside the urban and suburban boundaries or may be defined in terms of its radius distance from the library facility, depending upon the geographical characteristics of the region. Since telecommunications services are typically contained within a fixed building setting, the designation of RSA is an important one because library services such as Internet access may need to be provided in some mobile form (similar to a Bookmobile service). Providers serving RSAs have many unique problems with regard to installing and maintaining profitable enterprises. Rural areas have smaller population-toland ratios that necessitate more wires for fewer people and longer trips for service personnel. Rural areas often require a larger proportion of long-distance services compared to local services. To complicate matters further, the topography of rural areas may be rough and inaccessible, especially in mountainous regions. Even rodents pose a problem in rural areas, chewing through communications wires installed above-ground on rocky terrain. In terms of fast Internet access, ISDN and other services are disproportionately skewed toward Metropolitan Service Areas. Wireless communications might seem to be an ideal solution to many of these problems, but RSA providers often are smaller organizations that have difficulty competing with larger firms for Federal Communications Commission (FCC) licenses for wireless services. rural telephone company This is defined in the Telecommunications Act of 1996 and published by the Federal Communications Commission (FCC) as: “... a local exchange carrier operating entity to the extent that such entity— (A) provides common carrier service to any local exchange carrier study area that does not include either— (i) any incorporated place of 10,000 inhabitants or more, or any part thereof, based on the most recently available population statistics of the Bureau of the Census; or (ii) any territory, incorporated or unincorporated, included in an urbanized area, as defined by the Bureau of the Census as of August 10, 1993; (B) provides telephone exchange service, including exchange access, to fewer than 50,000 access lines; (C) provides telephone exchange service to any local exchange carrier study area with fewer than 100,000 access lines; or (D) has less than 15 percent of its access lines in communities of more than 50,000 on the date of enactment of the Telecommunications Act of 1996.” See Federal Communications Commission, Telecommunications Act of 1996.

Rural Utilities Service RUS. A U.S. Department of Agriculture agency that provides technical and funding support for rural utilities infrastructure projects involving electricity, water, and telecommunications. http://www.rurdev.usda.gov/rus/ RURL Relative Uniform Resource Locator, Relative URL. A compact representation of the location and method of access for a resource accessible over the Internet that is described relative to an absolute base URL. In contrast, an absolute base URL is one for which a specific location is established, such as http://www.4-sights.com/ and remains the same no matter where the Web page holding the link, for example, is located. However, there are situations where an absolute URL is not the best solution. Imagine establishing an extensive Web site at www.4-sights.com that has many document and graphics files hierarchically contained in subdirectories below the main directory. Assume the subdirectories are called docs and pics and that you are building a page in the docs directory (absolute URL - http://www.4-sights.com/docs/mydoc.html) that has many images linked from the pics directory. In terms of building the page in HTML, it is tedious to type http://www.4-sights.com/pics/filename.jpg each time a new image is added to the page with a link. Instead, a relative URL can be used and the image referenced as ../pics/filename.jpg. In the context of the current location of the site, it means the same thing. The dot-dot-slash tells the system to go back up a directory and down into the pics subdirectory. Not only is this shorter and easier to type, but it saves a huge amount of time if the entire Web site must be moved en masse to another domain name or Web host (assuming you’re not renaming directories or rearranging at the same time). With relative URLs, which reference the current location, the links will still point to the same locations in the directory structures as they did on the previous domain location. Voila. If the Webmaster didn’t use relative URLs to build a site for which the domain name is likely to change, rap his or her knuckles. (Of course the Webmaster may be a contractor hoping to log a few extra work hours.) Relative URLs were described in a Standards Track RFC by R. Fielding in June 1995 and have since become an intrinsic part of HTML as it is used on the World Wide Web. See RFC 1808. RUS See Rural Utilities Service. Rutherford, Ernest (1871-1937) A New Zealandborn British physicist who contributed substantially to knowledge about atomic physics. Rutherford researched at the Cavendish lab studying ionizing gases and following up much of the work of the Curies and Philipp Lenard. He collaborated with Hans Geiger, developer of the Geiger counter, and influenced Paul Villard’s studies of gamma rays. RVA recorded voice announcement. A digital or analog recorded or synthesized voice announcement, as might be found on an answering machine, for example. The phone company used RVAs to communicate with callers using touchtone menu systems and also uses them to alert the user to problems (such as

a phone being off-hook). See Barbe, Jane. RW 1. read/write. 2. see real world. 2. remote workstation. RWhois, rwhois Referral Whois. RWhois gives users a means to look up information on the Internet. It is a primarily hierarchical, client/server distributed system for the discovery, retrieval, and maintenance of directory information on computer networks. RWhois facilitates deterministic routing of queries based upon hierarchical tags, referring the user closer to the source of the information. The RWhois specification defines a directory architecture and a directory access protocol, as they are intrinsically related. RWhois extends and enhances its predecessor, Whois (based upon WhoIs Protocol) in a hierarchical, scalable way in order to meet the increased demands on Whois from the explosive growth of the Internet. The protocol and its architecture are structurally derived from the Domain Name System (DNS), and concepts from the X.500 Protocol and Simple Mail Transport Protocol (SMTP) have been incorporated into the specification. To use RWhois from a command line shell that supports the utility, type “rwhois” in lowercase. Whois-based queries are particularly popular for querying information about IP numbers, NIC handles, and domain name registrants through domain registry services such as VeriSign. For example, a VeriSign domain registry search for crcpress.com yields: ---------------------------------------------------Registrant: CRC Press, Inc. (CRCPRESS-DOM) 2000 Corporate Blvd., NW Boca Raton, FL 33431 US Domain Name: CRCPRESS.COM Administrative Contact, Billing Contact: . . . Record last updated on 14-Nov-2001. Record expires on 19-Nov-2003. Record created on 18-Nov-1993. Database last updated on 28-Mar-2002 05:03:00 EST. Domain servers in listed order: NS1.DATARETURN.COM 216.46.236.253 NS2.DATARETURN.COM 63.251.95.25 ---------------------------------------------------The RWhois Operational Development Working Group is an IETF group chartered with coordinating, engineering, and operating the RWhois Protocol. See InterNIC, Whois, RFC 2167.

R

RWW See read-while-write. Rx abbrev. receive. This is most commonly used in the context of signals received over a serial link. Often used in conjunction with Tx (transmit). RxD receive data. Data channel, typically used in serial communications, which is an input for DTE devices and an output for DCE devices. See TxD, RTS, DSR, DTR, RS-232. RYS Abbreviation for “read your screen,” often used in text-based chat rooms online. RYS implies that an individual isn’t responding appropriately to recent events, presumably because she or he hasn’t been paying proper attention to the information typed by other participants (e.g., announcements from a channel operator). RZ return to zero. Return to a value of zero for a variable, file, or other entity. This is often used in binary signaling system contexts. See RZL. RZ-code A variety of signaling codes that have in

common the property of being able to return to zero to indicate a data value. RZ-AMI (alternate mark inversion), RZ-bipolar, and RZ-unipolar are examples. RZ codes are used in many transmission schemes for a variety of data encoding and timing synchronization applications. Some theorists make a distinction between RZ and AMI codes on the basis of frequency components, with reference to modulation, with RZ code streams having two components and AMI code streams having one. This distinction has practical implications in terms of filtering and resulting distortion in the RZ signal. See Alternate Mark Inversion, RZ. RZL return to zero level. Return to a level of zero, which may be zero voltage, zero output (of radio waves, for example), or other varying phenomenon. Zero in this case, usually implies an absence of a phenomenon, but it may also be a reference point such as 0°F. RZL is often used in analog contexts. See RZ.

S abbrev. sleeve or shield (ground shield) in electrical terminology. Cords, wires, and optical cables are protected by sleeves. The designation is sometimes used to describe plug configurations, for example, TRS refers to tip/sleeve or tip/ring/sleeve or tip/ring/ ground shield. A common example of a TRS configuration is a balanced stereo plug on stereo headphones. S bus In ISDN networks the data transmission path interconnecting network terminating equipment (NT1 or NT2) to addressable devices. The S bus can supply up to 8 W normal power or up to 420 mW in restricted power situations. Voltages vary from around 31 volts for normal and from around 37 volts for restricted power. See S interface, SBus. S interface In ISDN networks, a number of reference points have been specified as R, S, T, and U interfaces. To establish ISDN services, the telephone company typically has to install a number of devices to create the all-digital circuit connection necessary to send and receive digital voice and data transmissions. The S interface is typically used in the U.S. to connect an NT1/NT2 network termination device at the customer’s premises to terminal equipment (TE) or terminal adaptors (TA). In parts of Europe, a combined S/T interface provides a four-wire electrical extension interface between network terminating equipment (NT1) and up to eight addressable devices. The use of four wires enables a pair of wires to be used for each direction to and from the NTx equipment. The attached devices are typically telephones or computer interfaces. See ISDN interfaces for a diagram. S Series Recommendations A series of ITU-T recommendations providing guidelines for telegraph services terminal equipment. These guidelines are available as publications from the ITU-T for purchase from the Net. Since ITU-T specifications and recommendations are widely followed by vendors in the telecommunications industry, those wanting to maximize interoperability with other systems need to be aware of the information disseminated by the ITU-T. A full list of general categories is listed in Appendix C and specific series topics are listed under individual entries in this dictionary, e.g., R. Series Recommendations. See the S Series Recommendations chart.

S

S-band A broadcasting frequency spectrum ranging from about 1700 to 2360 MHz. S-band is typically used for radar, space communications, and some types of mobile services. It is terrain-sensitive. NASA uses S-band phase modulation to transmit and receive information between orbiting systems and the ground either directly or through relay satellites. NASA’s orbiter communications forward links (uplinks) are modulated on a center carrier frequency of 2106.4 MHz for the primary system and 2041.9 MHz for the secondary system. Two frequencies are used to prevent interference if two orbiters are transmitting simultaneously. Similarly the return links (downlinks) are modulated on a center carrier frequency of 2287.5 MHz and 2217.5 MHz. The Department of Defense (DoD) forward links are at lower S-band frequencies than the NASA systems (the return link frequencies are the same as NASA) and are channeled through its own ground stations. Radio waves are not used only for communication. They are also used for navigational tracking and the scientific determination of the characteristics of bodies in our solar system. For example, S-band Doppler effect experiments were conducted on Apollo 15 missions 14 to 17. These experiments enabled gravitational fields and other measurements to be calculated by observing the dynamic motion of the spacecraft through S-band radio waves transmitted between the craft and the Earth. One of the limitations of S-band is that it is terrainsensitive, which is why it has largely been used in space applications. However, if you are measuring terrain, this limitation becomes an asset. NASA has applied L-band and S-band frequency sensors to the remote sensing of geographical characteristics such as soil moisture and ocean salinity. The PALS (Passive/Active L/S-band Sensor) was first flown in July 1999 for these purposes. See band allocations for a chart. S-band Linear Collider Test Facility A facility at DESY developed to serve as a test bed for the technical aspects of a large-scale 500GeV e*e--collider to enable S-band technologies to be used more effectively with linear colliders for fundamental research in physics. See S-band. S-band Single-Access Transmitter SSAT. A transmitter installed in the Hubble Space Telescope that

S

ITU-T S Series Reommendations Recom.

Description

S.1

International Telegraph Alphabet No. 2

S.2

Coding scheme using International Telegraph Alphabet No. 2 (ITA2) to allow the transmission of capital and small letters

S.3

Transmission characteristics of the local end with its termination (ITA2)

S.4

Special use of certain characters of the International Telegraph Alphabet No. 2

S.5

Standardization of page-printing start-stop equipment and cooperation between page-printing and tape-printing start-stop equipment (ITA2)

S.6

Characteristics of answerback units (ITA2)

S.7

Control of teleprinter motors

S.8

Intercontinental standardization of the modulation rate of start-stop apparatus and of the use of combination No. 4 in figure-shift

S.9

Switching equipment of start-stop apparatus

S.10

Transmission at reduced-character transfer rate over a standardized 50-baud telegraph channel

S.11

Use of start-stop reperforating equipment for perforated tape retransmission

S.12

Conditions that must be satisfied by synchronous systems operating in connection with standard 50baud teleprinter circuits

S.13

Use on radio circuits of 7-unit synchronous systems giving error correction by automatic repetition

S.14

Suppression of unwanted reception in radiotelegraph multidestination teleprinter systems

S.15

Use of the telex network for data transmission at 50 bauds

S.16

Connection to the telex network of an automatic terminal using a V.24 DCE/DTE interface

Recom.

Description

S.17

Answer-back unit simulators

S.18

Conversion between International Telegraph Alphabet No. 2 and International Alphabet No. 5

S.19

Calling and answering in the telex network with automatic terminal equipment

S.20

Automatic clearing procedure for a telex terminal

S.21

Use of display screens in telex machines

S.22

"Conversation impossible" or prerecorded message in response to J/BELL signals from a telex terminal

S.23

Automatic request of the answerback of the terminal of the calling party, by the telex terminal of the called party or by the international network

S.30

Standardization of basic model page-printing machine using International Alphabet No. 5

S.31

Transmission characteristics for start-stop data terminal equipment using International Alphabet No. 5

S.32

Answer-back units for 200- and 300-baud start-stop machines in accordance with Recommendation S.30

S.33

Alphabets and presentation characteristics for the intex service

S.34

Intex terminals – Requirements to effect interworking with the international telex service

S.35

Answerback coding for the Intex service

S.36

INTEX and similar services – Terminal requirements to effect interworking between terminals operating at different speeds

S.140

Definitions of essential technical terms relating to apparatus for alphabetic telegraphy

Supplements S.Sup1

Minimal specifications for the bilingual (Arabic/Latin) teleprinter

sends data gathered by the Hubble to astronomers on Earth using S-band radio frequency signals. Hubble has two of these transmitters and two large communications dishes that direct the data transmissions to orbiting NASA satellites with single-access antennas, where they are collected and relayed to a ground station in New Mexico. From there the data are forwarded to the Hubble Space Telescope Science Institute in Baltimore. When one of the SSATs failed in 1998, the other was rotated to shoulder some of the load of the failed transmitter. Since the Hubble was designed to be maintained and repaired during space missions, an S-band Single-Access Transmitter was one of the components stored in the Contingency ORU Protective Enclosure (COPE) in the Space Shuttle Discovery’s cargo bay within the Orbital Replacement Unit Carrier. The Discovery crew was scheduled to replace the failed transmitter on Day 3 of Mission 3A. See S-band.

The S-band Single-Access Transmitter unit used in the space-based Hubble Space Telescope for transmitting data via orbiting satellites to data processing centers and astronomers on Earth. [NASA image.]

S-HTTP See Secure HTTP. S-Video, Super Video A video transmissions standard in which the information is carried in two separate signals: chrominance (color) and luminance (brightness). It is also known as S-VHS and as Y/C video with Y representing luminance and C representing chrominance (which in turn carries I and Q signals). S-Video provides a higher quality, sharper image than traditional composite video in which the chrominance and luminance are transmitted as a combined signal. S-Video is commonly supported on newer monitors, camcorders, and other consumer and professional video devices. Beware of bargain basement S-Video cables; inadequate shielding can result in a type of interference called crosstalk and cancels out the benefits of S-Video. Most S-Video cables are 4-pin miniDINs but some manufacturers have created custom cables/pinouts for S-Video (e.g., for game boxes). Note that it may not be enough to hook up an S-Video cable to get S-Video output/input; you may also have to set a menu setting or flip a switch to direct the

device to use the S-Video port as many devices default to a composite port. See I signal, Q signal.

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Two male mini-DIN S-Video connectors. On the left, the standard 4-pin cable compatible with a wide variety of camcorders, video monitors, VCRs, etc. On the right, a 7-pin mini-DIN connector for Macintosh computers (e.g., PowerMac AV) and some video capture cards with standard camera interfaces. Both cable ends are keyed to prevent incorrect insertion. Pinouts – standard S-Video: 1 GND ground (Y) 2 GND ground (C) 3 Y luminance (light intensity) 4 C chrominance (color) Pinouts – PowerMac AV S-Video (capture cards with female connections may assign pins 6 and 7 opposite to the Mac pinouts shown here): 1 A GND ground 2 A GND ground 3 Y luminance (light intensity 4 C chominance (color) 5 I2C clock composite video 6 +12V no connection 7 12C data no connection

S/MAIL A commercial Windows-based product from RSA Data Security, Inc., released in August 1997. S/MAIL is a developer software kit for building S/MIME-enabled applications. It is a high-level toolkit providing a plugin engine for secure email messaging that enables S/MIME functionality to be integrated into a variety of application types, including EDI software, online service clients, and email clients. The S/MAIL toolkit includes core cryptographic components, message formatting, and a security user interface. See Multipurpose Internet Mail Extension, S/MIME. S/MIME A commercial product from RSA Data Security, Inc. for providing interoperable, secure email. S/MIME facilitates the development of interoperable RSA-based security products for electronic messaging so that an S/MIME message can be composed and encrypted with one application and decrypted with another. It is based on standard MIME specifications integrated with the Public Key Cryptography Standards (PKCS). See Multipurpose Internet Mail Extension, S/MAIL. S/N See signal-to-noise. S/W software. SA 1. See Service Agent. 2. source address. In networking, an address to identify the physical or virtual location of the system initiating a transmission. This is important for various reasons, depending

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on the device and the topology of the network, but is used for establishing point-to-point communications, for routing return information, establishing an efficient communications path, auditing secured communications, tracing a path, and many other functions. SAA 1. Standards Association of Australia. See Standards Australia International, Ltd. 2. Supplemental Alert Adapter. A connection device for interfacing alerting devices to analog multiline phones. 3. See Systems Application Architecture. Saco River Telegraph & Telephone Company SRTT. Maine’s oldest independent phone company, established in 1889. The company has gone through many changes in its more than 100-year history. By fall 2001, it had published the Saco River Yellow Pages on its Web site and announced the coming availability of DSL services for its subscribers. SAFE 1. Security and Freedom through Encryption. SAFE Act See Security and Freedom through Encryption Act. See Clipper Chip, Pretty Good Privacy. SAFENET The U.S. Department of Defense’s (DoD’s) military standard for a Survivable Adaptable Fiber Optic Embedded Network intended to provide mission-critical, networked communications. See Xpress Transport Protocol. safety saddle A wide sling-shaped seat that fits around the buttocks of a worker suspended from a pole, line, building, crane, or other high prominence for the purposes of installing, testing, repairing, or maintaining equipment, especially telecommunications lines. The saddle is usually attached to a line or support hook by a hitch arrangement on the top of the saddle, above the user’s belly, although those designed for use when climbing poles may wrap around to the other side of the pole to be hitched up as the lineworker climbs. Safety saddles are typically made of thick, tough, resilient materials (e.g., leather) as the worker’s life depends upon their reliability. sag, cable The characteristic downward caternary curve occurring in the center of horizontally hung cables due to the effect of gravity. The curvature is based upon a variety of factors, including the diameter of the cable, the “straightline” distance (the distance between two adjacent cable supporting structures such as utility poles), and the flexibility of the materials surrounding the conductive materials, if present. Wind, temperature, and humidity sometimes influence the degree of sag in lighter cables. Cable sag estimates are important, since extra cable must be calculated and ordered to compensate for the effects of sag (the cable displacement), especially over long cable segments. Sag estimates must also be calculated for cables that are fragile and more likely to break and for fiber optic cables in which the angle of the light beam should be as straight as possible to prevent signal loss into the cladding. The sag estimate can help determine the maximum recommended distance between attachment points. There are sites on the Web that enable users to calculate displacement cable sag errors by inputting cable tension, distance, weight, and gravity force data.

sag, voltage A short dip or decrease in voltage from a power source. In “mains” alternating current (AC) power sources, voltage sag can result from lightning storms, fallen trees, malfunctions, and other causes. Loss of power may result in a voltage sag while a backup power supply comes online or while a transformer feeds a load during the electrical fault. In public power distribution systems, those closer to the fault are usually the most affected; those farther from the fault may be buffered by intervening transformer stations. Voltage sags may damage many types of sensitive electronic components, especially in their manufacture. As a consequence, the Semiconductor Industry Association (SIA) has developed voltage sag immunity standards for semiconductor manufacturing equipment. Certification according to the SEMI F47 standard indicates that equipment complies with certain voltage sag duration tolerances. Similarly, the IEEE P1564 Task Force on Voltage Sag Indices met in 2001 to review a proposed five-step process for developing Sag Indices based upon a draft IEC document (61000-4-30), as well as alternative means of obtaining voltage sag indices. Voltage sag susceptibility testing is a process for identifying weak links in a system through simulated production modes to identify problem areas and to test possible solution scenarios. A power conditioner is a system installed in conjunction with the electrical distribution system to prevent sags. In electrically sensitive fabrications plants, the cost of a conditioner or other sag-prevention product may be less than the cost of loss or productivity or sag-caused damage. sagan A tongue-in-cheek tribute to Carl Sagan, indicating a very, very large amount. “Billions and billions,” as he would say with infectious enthusiasm in his popular TV series when referring to the many stars in the cosmos. Sagan’s premature death was mourned by many amateur astronomers who got their first taste of the wonders of the galaxy and beyond through Sagan’s show. Sagan, Carl E. (1934-1996) An American astronomer, writer, educator, and inspirational host of the popular “Cosmos” television series on the U.S. Public Broadcast System (PBS). Sagan was the director of the Laboratory for Planetary Studies and the David Duncan Professor of Astronomy and Space Sciences at Cornell University. See sagan. SAGE Semi-Automatic Ground Environment. A U.S. government security digital communications, detection, and craft control network. SAI See Standards Australia International, Ltd. SAIL See Stanford Artificial Intelligence Laboratory. Salvà i Campillo, Francesc (1751-1828) One of the genuine pioneers of telegraphic technology, Salvà was a prodigy who received a degree in medicine at the age of 20 and went on to study communicable diseases, promoting the use of the smallpox vaccine. He was a prolific researcher in many fields and developed a type of underwater craft, a historic

submarine, as well as an aeronautic balloon that was demonstrated in flight in 1784. Salvà was already describing ideas for telegraphs by 1795, before the invention of the voltaic pile, and developed an electrochemical telegraph signaling system around 1804 in Barcelona, Spain, more than three decades earlier than the Wheatstone/Cooke and Morse telegraphs. Each character was assigned to an electrical wire that produced gas bubbles in an acid bath at the receiving end when current was applied to the cable on the transmitting end. This system provided inspiration for Samuel Thomas von Sömmering a few years later. See Sömmering, Samuel Thomas; telegraph history. SAM security accounts manager. samarium A silver rare earth metal discovered through spectroscopy in samarskite in the late 1800s. Samarium is used for doping calcium fluoride crystals for use in lasers. It is one of the rare earth metals used in carbon-arc lights. See doping. Samba An open source client/server system running on Linux systems, Samba facilitates peaceful coexistence between Unix and Windows platforms. Samba communicates with Windows clients transparently, enabling a Unix system to join a Windowsbased “Network Neighborhood.” In the other direction, Windows users can access file and print services and other resources on the Unix system. Communication is facilitated by the Common Internet File System (CIFS), the heir to Server Message Block (SMB) protocol. Samba has been ported to other operating systems as well, including VMS, NetWare, and AmigaOS. See Server Message Block protocol. Samba is freely downloadable from the Samba site. http://samba.org/ sampling Recording a signal by quantizing it at intervals in order to capture its basic properties, usually also accompanied by saving the samples in a digital or abbreviated form. It is a form of analog to digital conversion. In digital sound sampling, for example, the sound of a musical instrument or a voice can be digitally sampled a certain number of times per second in order to be able to play back the sound so that it retains and conveys the character of the original, although not necessarily all the information or format of the original. Music synthesizers use sound samples to recreate the sounds of various traditional instruments. Computers use sound samples to alert or amuse users or to enhance video games or other applications. Telephone systems use sound samples to send voice mail announcements or instructions to users or to transmit voice conversations over digital systems. In general, more frequent samples result in better fidelity to the original during playback. However, there are practical and perceptual limits. More frequent sampling makes higher demands on the equipment, requires more memory to store, and more bandwidth to transmit. Since humans can’t distinguish the sample from the original above certain parameters, it is not practical to commit extra resources to recreating a signal above these limits. In commercial

applications, a sampling rate of 44.1 kHz is used on audio CDs. Audio-only DVDs are higher, but some of this is related more to marketing and technical compatibilities than to increased perceptual enjoyment. Some sounds, like the sound of a concerto played on a violin, are more complex than others (e.g., a doorbell), and require more frequent samples and a greater frequency range to retain the perceptual quality of the original. In some cases, different sampling techniques must be used at different pitch ranges in order to recreate the sound as it is heard by humans. Sampling algorithms are often applied to sound transmissions, but they are also relevant to video transmissions or multimedia transmissions. In videoconferencing over slow transmission lines, the image is usually sampled rather than played in realtime, that is, a new still image is grabbed or digitized and transmitted every few seconds or every few minutes. Generally, as in sound sampling, more frequent samples provide greater fidelity to the original. In video sampling, rates of at least 20 to 30 frames per second are perceived by humans as natural motion. See animation, audiographics, pulse code modulation. sampling rate The number of captures of an input, such as light or sound waves, per unit of time. Sampling rates for images are generally expressed in frames per second, with 24 or more appearing natural to the viewer. Sampling rates for audio are generally expressed in kilohertz (kHz); an instrument might be sampled at 50 kHz, that is 50,000 bits per second. Higher sampling rates generally require more sophisticated equipment, higher processing speeds, and faster transmission speeds, especially if the signals are sent over a network. See sampling, sampling theorem. sampling rate, Nyquist A theoretical sampling frequency (in terms of rate not wavelength) at which the rate is the minimum separation of samples in a Fourier plane that enables a complete reconstruction of the original sampled data. The sampling process itself may introduce errors into the quantization, so the actual sampling rate needed to reconstruct a signal may be higher than the theoretical Nyquist rate. Depending upon the application, half the Nyquist rate may be referred to as the Nyquist frequency. The mathematical and theoretical groundwork for defining the Nyquist rate is based on work by Nyquist in 1928 and Shannon in the late 1940s. The theorem has variously been called the Nyquist or Shannon or Nyquist-Shannon sampling theorem. Sampling at rates below the Nyquist rate is called undersampling and results in less-than-perfect reconstruction of the original sampled data, but may be expedient in terms of resources. Humans are very good at perceptually filling in the blanks when presented with incomplete data. A picture of a familiar face can have most of the face removed with scissors or blotted out by a marking pen and still be recognizable to many. In the same sense, information can be left out of an image or sound sample and

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still be recognizable (if not optimal) for many purposes. Sampling beyond the Nyquist level is termed oversampling and is unnecessary in terms of reconstruction but may be useful in creating redundancy for error correction or transmission purposes. The application of Nyquist rate theories is as much art as science. Since filters are introduced into quantization methods to create high and low cutoff values, some assumptions are made about the signal even before it is sampled. It cannot always be known in advance what these values should be and some adjustments may have to be made based on trial and error. The “complete” reconstruction of a signal is very hard to judge in advance as well. When choosing a sampling rate for audio, for example, and playing it back to a general audience, it might be acceptable to the audience and seem to them to be identical to the original analog signal. If, on the other hand, the same sample is played to a trained musician, such as a concert performer, that individual might notice significant differences between the original and the reconstruction. In fact, this situation happened in the production of early audio CDs, with many music lovers complaining that CD music sounded flat, a situation that has since been improved with experience, technological adjustments, and a better understanding of human auditory perception. See sampling, sampling rate, sampling theorem. sampling theorem A theoretical basis for relating discrete representations, or samples, to continuous functions with the implication that the continuous function can be recreated from the discrete representations to a lesser or greater degree, depending upon the characteristics of the continuous function. In simpler terms, a sampling theorem is a theoretical context within which analog-to-digital and digital-toanalog mathematical conversion formulas can be developed. Sampling theorems form a theoretical basis for developing formulas and practical applications such as analog sound digitization and reconstruction. These formulas are still evolving and it has been suggested that the Poisson Summation Formulas can be used to prove corresponding sampling theorems and, in turn, give rise to new uniform sampling formulas (Benedetto and Zimmermann, 1997). The Interpolation Identity has been proposed as a means to develop a new class of sampling theorems for obtaining efficient discrete-time (DT) systems and the efficient interpolation and reconstruction of samples (Eldar and Oppenheim, 2000). Sampling theorems are often named after the scientists who developed them or who set the mathematical groundwork for subsequent sampling theories. There are sampling theorems named for the work of Whittaker in 1915 and for Shannon in the late 1940s. The theories of Whittaker and Shannon led to important advances in pulse code modulation (PCM). The Shannon sampling theorem is used in uniform sampling, for example, and is especially practical for certain types of transmissions, e.g., FM broadcasts. A variant on this is the Whittaker-ShannonKotel’nikov sampling theorem which may be used,

for example, for sampling stochastic signals. A. Papoulis developed a generalized expansion theorem for uniform sampling and M. Unser suggested an extension of this for nonband-limited functions. The Papoulis-Gerchberg theorem can be used to recover missing samples in finite-length records of band-limited data and has also been applied to wavelet subspaces (Xia et al., 1995). More recent applications of sampling theorems in wavelet technologies have resulted in some intriguing quantization and compression algorithms. See Kotel’nikov, Vladimir. In practical applications, most samples are uniform (periodic) and Fourier transforms are often used in the context of sampling theorems. However, not all sampling environments are uniform; multichannel sets may be used or samples may vary according to time and traditional Fourier-based methods of handling the data may be impractical. Consequently, researchers have been developing general theories to encompass nonuniform sampling in shift-invariant spaces (e.g., Aldroubi et al.). See Fourier transform, pulse code modulation, sampling, sampling rate, wavelet theory. SAN 1. See satellite access node. 2. See storage area network. Sandbox A Sun Microsystems Java security block. Since Java applets are freely shared through public sites on the Internet, there is always reason to question whether they contain hidden viruses or other destructive or annoying capabilities. The Sandbox is a means of restricting doubtful applets to a confined area, that is, quarantining them so they cannot affect other data on the disk or other Sandboxes. sanity check The process of sitting back and reflecting on one’s current priorities, responsibilities, and level of stress. Anyone in the computer industry probably needs to do a sanity check once in a while to evaluate whether the technology is improving the quality of his or her life, or whether it is just eating up time and money and forcing everyone to do more in less time. (Probably descended from the phrase systems check – a step-by-step run-through of a system’s current operating status to determine if there are any issues requiring attention or repair.) SANS Institute The System Administration, Networking, and Security Institute, founded in 1989, is a cooperative research and education organization serving security professionals and systems administrators worldwide. The Institute helps to promote research, incident awareness, and security certification programs related to global network security. http://www.sans.org/ SANZ Standards Association of New Zealand. SAP 1. Scientific Advisory Panel. 2. See Second Audio Program. 3. Service Access Point. An interface point in a network, often associated with a specific layer. 4. See Service Advertising Protocol. 5. See Session Announcement Protocol. SAPI Service Access Point Identifier. SAR 1. See segmentation and reassembly. 2. synthetic aperture radar.

SAREX See Shuttle Amateur Radio Experiment. Sarnoff, David (1891-1971) A Russian emigrant to America, Sarnoff was an ambitious, energetic radio operator and Marconi station manager at the Radio Corporation of America (RCA) widely reported to have intercepted the messages of the Carpathia when the Titanic struck an iceberg, and to have relayed the messages to relatives and friends of the passengers on the sinking ship. While it is likely that Sarnoff did play a part in relaying the messages, the RCA promotional information of this event included a doctored picture of Sarnoff at the console, which lends some doubt to the claim that Sarnoff handled the post single-handedly for 72 hours, as widely promoted. Sarnoff became the general manager of the Radio Corporation of American in 1921 and went on to play a large part in its history and development. He is also remembered for his association with the inventor E. Armstrong in the late 1920s which ended abruptly in 1935 with the removal of Armstrong’s test equipment from the premises and the development of television. In 1926, Sarnoff was instrumental in founding the National Broadcasting Company (NBC). The IEEE now honors Sarnoff’s contributions with the David Sarnoff Award in Electronics. See Radio Corporation of America. SART See search and rescue radar transponder. SAS 1. single address space. 2. simple attachment scheme. 3. Survivable Adaptive Systems. SASL See Simple Security and Authentication Layer. SASMO Syrian Arab Organization for Standardization and Metrology. SASO Saudi Arabian Standards Organization. sat-, -sat A prefix/suffix often prepended/appended to satellite-related names and technologies.

An RCA communications satellite just after being sent out into orbit from the payload bay of the Space Shuttle Atlantis, in December, 1985. This satellite was dubbed Satcom K-2. [NASA image.]

SATCOM, SatCom Satellite Communications.

SATCOM is both a colloquial abbreviation and the trade name of quite a number of satellite-related firms and organizations around the world. • North American Treaty Organization Satellite Communications, known as NATO SATCOM, is a branch of the Communications Systems Division that supports the Satellite Communications Project, which in turn provides support to Major NATO Commands. See SATCOM Integrated Test Network. • Satcom Resources is a commercial supplier of satellite communications systems. • SatCom Systems, Inc. is a Federal Communications Commission-licensed supplier of U.S. market mobile satellite services through the MSAT-1 satellite system. • SatCom Electronics, Inc. provides electronics products for wireless and broadband satellite communications, including DBS-TV satellite services. • The British National Space Centre (BNSC) uses a variation on the name, S@TCOM for a program designed to help companies in the United Kingdom exploit satellite communications and navigations opportunities. SATCOM Integrated Test Network SATIN. A central testbed for NATO SATCOM experiments in communications services and technologies in a SATCOM environment. SATIN can provide communications to other testbeds and can interconnect with other divisions and organizations through NC3A Satellite Experimental Terminal (SET) facilities. Examples of SATIN projects include ATM over SATCOM and Maritime over SATCOM. satellite, artificial A manufactured object launched to orbit the Earth, Moon, or other celestial body. There are currently many communications and Global Positioning System (GPS) satellites in orbit around Earth which send and receive signals to and from ground stations and transportation vehicles (cars, trains, boats, planes, etc.). Satellites now provide the main means for wireless long-distance communications. The first artificial satellite was Sputnik I in 1957, followed by the first geostationary satellite in 1963. See global positioning systems, satellite antennas. satellite, natural A celestial body in orbit around another. satellite access node SAN. A terrestrial satellite link, usually consisting of an Earth station or Earth station hub. satellite antennas Satellite antennas were originally launched into orbit for military monitoring and communications, space research, and cable TV broadcasting, but increasing numbers serve individual parabolic home receivers and data communications providers. GPS satellites orbit at about 18,000 km (11,000 miles) and broadcast satellites at about 36,000 km (22,300 miles) altitude. In its basic form, a broadcast satellite system consists of a broadcasting station sending signals

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through an uplink dish aimed directly at a geostationary satellite antenna in synchronized orbit with the Earth. The signal subsequently is sent from the satellite to a downlink dish (parabolic antenna) attached variously to business complexes or rebroadcast stations, and subsequently directed to subscribers through coaxial cable. Some stations broadcast directly through scrambled signals to apartment blocks or individual households. The lead from the downlink dish feeds into the user’s television or computer system. See antenna, C-band, feed horn, Global Positioning System, Ka-band, Ku-band, microwave antenna, parabolic antenna. satellite broadcast frequencies The various ranges of frequencies over which satellite antenna transmissions take place. These are dependent on many factors, including the type of transmission, the type of satellite, and regulatory guidelines and restrictions. Broadcast stations typically operate in the C-band, with uplinks at about 6000 MHz and downlinks at about 4000 MHz to rebroadcast stations with powerful antennas. The frequency levels are tied to the size of the receiving dishes, with higher frequencies more difficult to accommodate technologically, but with the advantage of much smaller receiving dishes. Higher frequencies can broadcast to smaller receivers, making it possible for some frequencies to be broadcast directly to smaller consumer dishes. See C-band, Ka-band, Ku-band. satellite closet A centralized wiring closet for interconnection of cables and equipment. In a number of satellite installations, the programming is beamed from the satellite to a central service provider with a satellite receiving dish and, from there, delivered by wire or cable to subscribers, necessitating local loop hookups. See distribution frame. satellite communications A wide variety of radio, television, telephone, data, and other broadcast and two-way wireless communications provided by transmission via orbiting satellites to centralized distribution providers or individual subscriber satellite dishes. The age of satellite communications began in the late 1950s, with the launch of Sputnik I, although it was described with remarkable insight by Arthur C. Clarke in the 1940s and 1950s in various articles and books. The early satellites did not last long (from a few weeks to a few months) and power consumption and radiation problems had to be solved before widespread use became practical. In less than four decades from their modest beginnings, satellite communications have developed rapidly and now hundreds of satellites of different designs orbit the Earth at various distances. Their lifespans now range from about 5 to 15 years, and most are powered by solar panels with battery backup. It was not long after the first satellites were launched that they were used by commercial and amateur radio stations. The first television broadcast station to

use satellites was the Canadian Broadcasting Corporation, transmitting through ANIK in 1972. Direct broadcast to consumers, rather than through intermediary stations, did not really become prevalent until the 1990s, when broadcasts of higher frequencies became practical and smaller, more convenient satellite dishes were manufactured. Satellites are launched in conjunction with spacecraft or shuttle craft into elliptical or geostationary orbits from about 500 km to about 36,000 km above the Earth and are able either to passively transmit data back to Earth (these are becoming rare), or actively regenerate or otherwise amplify the signal and retransmit, usually at a different frequency to avoid interference of uplink and downlink signals. Satellites are general purpose with many transponders or specialized for data, voice, broadcast, etc. Broadcast satellites tend to be unidirectional, while data and voice satellites, as for mobile systems, are bidirectional. See AMSAT; Clarke, Arthur C; Global Positioning System; direct broadcast satellite, OSCAR, Syncom, Telstar, and the many listings under satellite services. satellite communications control SCC. The Earthbased station facilities and equipment which control satellite transmissions, including signaling functions, access control, error correction, signal conditioning and noise reduction, etc. satellite constellation A group of satellites in a cluster. A group of satellites is commonly used for Global Positioning System (GPS) applications, for example, where data from three or more related satellites are mathematically manipulated to yield precise positioning information of an Earth location. Satellite Home Viewer Improvement Act SHVIA. An Act signed into law by President Clinton in November 1999. This significant Act modifies a number of existing communications and intellectual property acts, including the Satellite Home Viewer Act of 1988, the Communications Act, and the U.S. Copyright Act. It permits satellite broadcasting services companies to retransmit signals within their designated market area (DMA) without paying a royalty, beginning on January 1, 2002. To offset this privilege, satellite carriers must carry the signals of all full-power TV broadcast stations within that market, upon request. The purpose of the Act is to promote competition among multichannel video programming distributors such as cable television and satellite suppliers, while increasing the programming range for subscribers. Satellite broadcasters would now be permitted to provide local broadcast TV signals to all subscribes within the licensed market (Designated Market Area [DMA]) as defined by Nielsen Media Research. This is known as local-into-local service and would initially include only major network affiliates. Unfortunately, as the service is optional, unprofitable markets such as rural areas would potentially be neglected by this Act without further legislative actions and incentives to promote the delivery of services in underserved areas.

The Act further permits satellite companies to provide distant network stations to eligible satellite subscribers. Some exemptions are contained in the Act, including an exemption for those subscribing to C-band services on or before October 31, 1999 and exemptions for certain recreational vehicles and trucks. Prior to SHVIA, consumers who terminated cable service had to wait 90 days before receiving satellite TV service. This is no longer mandatory. The Act did not pass without subsequent opposition. A number of satellite providers jointly and individually filed suit against the FCC and the Copyright Office on the grounds that the local-to-local service provisions were unconstitutional. A number of public broadcasting organizations intervened in the interests of public television stations. Concerns over rural and other underserved populations resulted in other related Acts, including the LOCAL TV Act of 2000. See Grade B signal, LOCAL TV Act of 2000, National Rural Telecommunications Cooperative, Rural Local Television Signals Act. satellite link A system of transmitters and receivers communicating with a satellite, usually through an active transponder which will amplify and shift the received communications to another frequency before retransmitting on the downlink. Uplinks and downlinks are often managed separately. For example, television broadcasts are primarily in one direction (though interactive TV applications are increasing), while phone and computer data communications are typically in two directions. See geostationary, satellite. satellite scanner See scanner. satellite scatter This has two opposite meanings, as scatter can be the undesirable diffusion and weakening of a signal or, conversely, a deliberate manipulation of the environment to enhance communications. In the latter, it was discovered that ionization of airborne particles could open up communications windows which otherwise were not available. Thus, burns from launched spacecraft or deliberate “seeding” of high regions with elements like barium could provide possibilities for detecting or sending transmissions through these temporary holes. There have also been experiments with heating the ionosphere with high-powered waves to form a type of “aurora” which can facilitate transmissions. Due to their transient nature and the strength of the signals needed, these are not major sources of communications, but it’s valuable to understand the nature of the various phenomena and receive occasional glimpses into frequencies emanating from space. satellite services Profit and not-for-profit organizations which provide various types of satellite-based communications services. See American Mobile Satellite Corporation, AMSAT, ARIES, Astrolink, Constellation Communications, Inc., CyberStar, ECCO, Ellipso, ICO Global Communications, INMARSAT, Globalstar, OrbLink, Skynet, Spaceway, Teledesic. Satellite Work Centers A telework organization similar to a branch office, placed in a residential or rural village area by a business entity, and made

commercially viable by the implementation of new communications technologies. See ADVANCE Project, Shared Facility Centers, telework. saturation To add or adjust such that no more can be absorbed, or contained. In color applications, saturation refers to color purity. Undithered colors on a computer monitor or printing inks made from primary pigments tend to be highly saturated. saucer insulator A historic utility pole insulator developed by Edward Hewlett, which he described in 1907. Like the strain insulator which was developed around the same time, the saucer insulator had an interlocking design. However, the physical appearance was quite different from the strain insulator; the Hewlett insulator resembled a flying saucer or rounded pagoda roof, an inverted saucer shape housing the interlocking ceramic wheel and groove. Hewlett filed for a patent that was granted 7 years later, in 1914, and granted the rights to General Electric Company. See strain insulator. save 1. In computer applications, a selection that permits the storage of information for later retrieval. 2. In phone hardware, a key sequence or button that enables the user to store a number for later quick retrieval. See speed dialing. SBE See Society of Broadcast Engineers. SBR spaceborne radar. SBus A Sun Microsystems data bus is used to support a standardized data format that can be transmitted over a wide variety of computer devices and services, including Fast and Gigabit Ethernet, SCSI, Token-Ring, ISDN, parallel connections, graphics adaptors, and frame buffers. Computers equipped with SBus slots can be extended with SBus-compliant peripheral cards in the same basic way that PCI peripheral cards are installed in Intel-based PCs and Macintosh systems. Sbus cards may provide a data connection to another device or may provide conversion capabilities. For example, there are SBus cards that serve as PCMCIA adapters, providing one or more Type-II PCMCIA slots for inserting popular PC cards. The SBus format is specified in IEEE 1496-1993. SC switching center. scalable Adjustable, able to increase or decrease in size, capacity, or other relevant characteristics, without significant degradation in quality of service or functioning. Scalable fonts and images, usually defined as vectors, have the capability to adapt to lower and higher screen and printer resolutions, displaying at the best possible resolution for that particular device due to the internal algorithmic nature of the font definition. Scalable images are sometimes called resolution-independent images. Scalable networks allow the system to accommodate to changing conditions. In static environments, scalability is not a critical factor, and nonscalable systems tend to be less expensive. In dynamic environments, such as the Internet or large WAN implementations, scalability can be a crucial factor, especially over time, contributing to the flexibility and usability of a system.

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Many aspects of networks need to be scalable. The system software should be scalable to adapt to smaller and larger numbers of users, sometimes on a minute-to-minute basis. Physical storage mediums need to be scalable to accommodate less or more storage as needed. Routing protocols need to be scalable to accommodate changing topologies and numbers of workstations. Scalable Coherent Interface SCI. A high bandwidth, scalable, media-independent network transmission technology developed in the late 1980s that operates up to about 1 Gbps. It is an ANSI/ISO/IEEE standard (1596-1992). SCI supports parallel distributed multiprocessing and cache-coherent interconnection and fits into the upper mid-range in throughput. It is faster than ATM, Fibre Channel, and Ethernet, but slower than HIPPI-6400, and does not have HIPPI-6400’s retransmission capabilities. Initial implementations of SCI tend to be high-end commercial/industrial and military supercomputing applications. scalable typeface A character set defined algorithmically with vectors so that it can be displayed to the highest resolution of any particular display device. In other words, for a 75 dpi monitor, the typeface will display as well as the monitor can handle, but will also display as well as a high-end typesetting machine can handle, say 2400 dpi; that is, with smooth curves and fine details readily visible. In contrast, a nonscalable typeface is usually a raster screen font (composed of a specific number of dots arranged in a grid). It may look fine on the computer monitor, but print it at 600 or 1200 dpi or higher, and it looks the same is it does on the screen: grainy, chunky, staircased, and unappealing. The Adobe PostScript page definition language is used to define high-quality scalable fonts and images, in addition to being able to render images, charts, etc. Microsoft’s TrueType is a common format for scalable fonts. See PostScript, TrueType.

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The raster font on the left is very limited, as it is composed of a set number of pixels and cannot be effectively reduced or enlarged. In contrast, the vector font on the right can be scaled effectively from 4 points to 100 or 500 points or more as it is defined mathematically, based upon the relationships of its shapes and proportions, not a fixed number of dots.

scaling v.t. 1. Sizing, adjusting to size. May be proportional scaling, or selective scaling in one or more axes. Scaling is a common operation in image processing. See cropping. 2. Adjusting to capacity, or number of members. In programming there are often scalable ways of designing algorithms. For example, an operating system may have a fixed number of windows which can be open at one time (e.g., maximum of 200) or it may be scalable, in which the

maximum number of windows is limited only by the system resources, and becomes greater as greater resources are added (e.g., memory, storage space, CPU speed, etc.). Scalable systems are more flexible and less likely to go out of date, but are often more resource-intensive and sometimes more difficult to program. In network transmissions with a variety of protocols, scaling may occur to accommodate differences in bandwidth, data, or speed capacities of the various systems through which the transmission may travel. scan converter A device for converting a video signal. With computers it is common to take the RGB signal that normally leads to the computer monitor and feed the signal through a scan converter so it can be recorded on a video tape.

This AverKey scan converter takes a signal from a graphics card (usually the one leading to the monitor) and converts it to a signal compatible with NTSC video. This is useful for video recording.

scan line, scanning line On a display monitor, a narrow more-or-less continuous line illuminated by the movement of the electron beam across the inside surface of the tube. In television broadcasting and raster monitors, these are typically horizontal. On vector monitors, the scan line can be traced in any direction. See raster, vector. scanner A device that samples objects, information, or processes, and quantifies and records the results in some form that can be further processed or analyzed. Scanners, like digitizers, frequently sample analog information and convert it to digital, or convert a digital sample to a waveform for transmission. Typically the scanner does not process the information; its job is to capture the information, and often it can store that information in a variety of selectable formats. Once the information is captured, it is then sent “live” to a processing application or stored for later conversion or further processing. Scanners are used in a multitude of imaging and sensing applications, including those described in the Scanning Technologies chart. scanning rate 1. The speed, in units per time period, at which a scanning device captures information. Many common technologies are expressed in terms of inches per second. Generally, for moving images,

faster scan rates are associated with higher accuracy or fidelity in conveying motion. In still images, faster scan rates may compromise the resolution or fidelity of an image. 2. In cathode-ray tubes (CRTs), the scanning rate is the speed at which the electron beam sweeps the screen to refresh a full frame. This is usually about 30 frames per second. See cathode-ray tube, frame, interlace. 3. For technologies that use a beam for scanning (antennas, radar), the rate is more often expressed as a specified number of sweeps over a unit of time. scanning rate, optical For optical scanning of images, such as those used with computer scanners and facsimile machines, scanning rate is often not as important as resolution. In other words, the fineness of the scan is described rather than the speed at which it is scanned, with resolutions of 1200 to 4800 dpi interpolated common on desktop scanners. See scanner. scare-straps colloq. Telephone line worker safety belts. scatter v. To separate, to distribute widely or randomly, to disperse, to diffuse in various directions. scatter, transmission To diffuse or spread out in such as way as to lose the strength or directionality

of a transmission signal. In most communication transmissions, this is undesirable. See spreading loss. 3. To enhance communications through exploiting deliberate, controlled scatter. See satellite scatter. SCC 1. Specialized Common Carrier. A carrier competing with the dominant carrier in niche markets. 2. Standards Council of Canada. SCCP See Signaling Connection Control Part. SCE See Service Creation Environment. Scelbi-8H Scientific, electronic, and biological. A forerunner to personal computers, developed between 1972 and 1974 and released in 1974, it followed the Kenbak-1 which was first advertised in 1971. The Scelbi-8H was the first publicly advertised Intel 8008-based personal computer kit, developed by the Scelbi Computer Consulting Company in Milford, Connecticut. It featured one kilobyte of programmable memory and was priced at under $600. It was initially advertised as the Scelbi-8H in QST magazine in March 1974. The Scelbi was not a big seller and was soon overshadowed by the Altair, which was featured on the cover of Popular Electronics less than a year later. See Altair, Arkay CT650, Heathkit EC-1, Intel MCS-4, Kenbak-1, Mark-8, Micral, Simon, SPHERE.

Scanning Technologies for a Variety of Devices Application

Notes

scannning antenna

Parts of a moving antenna which cause the directional scanning of the antenna beam.

facsimile scanner

A component of a facsimile machine which converts a sampled digital image to a waveform for transmission over phone lines. See ITU-T, facsimile, TIFF.

image processing

A computer input device which passes a beam over a 2D or 3D object or image, and converts it to digital data, usually a 2D raster image. See digitizer, optical character recognition, TWAIN.

scanning radio

A radio receiver that scans a range of transmission frequencies automatically, so the user can locate and listen to conversations occurring at the time of the scan. Often used to find emergency or cellular phone conversations.

remote sensing

In satellite remote sensing, a scanner employing an oscillating mirror that captures images in strips was first proposed in 1968 by Hughes Aircraft for use in orbiting satellites, and first deployed in 1972 in the first Earth Resources Technology Satellite. This technology revolutionized understanding and recording of Earth’s topological and geological features. The program became Landsat in 1975.

robot vision

In robotics, a scanner samples visual input and processes the information in a way that provides data useful for tracking, navigating, or object sensing. Robot scanner interfaces vary widely, but often are small video cameras, light detection devices, or pattern sampling devices mounted on the robot itself. Robot scanners may be simple, to detect and record light or dark areas, or complex, to capture sophisticated patterns, further processed as faces or recognized as objects.

scanning software

A software program that searches data for new entries of a particular kind, such as newly uploaded files, email, user logins, etc., or which scans processes such as network load, states, CPU usage, etc.

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SCEP See Service Creation Environment Point. Sceptron spectral comparative pattern recognizer. An intelligent pattern-recognition system developed in the early 1960s by Robert D. Hawkins of Sperry Gyroscope. The Sceptron employed quartz or glass fibers, a photocell, electrical current, and mechanical motion to recognize a spoken word and optionally print it on a little illuminated display. When exposed to audio stimulation, the Sceptron “learns” the sound and can recognize it in the future. Other types of signals translated into the audio frequency can also be recognized. Sceptron was able to pick out a learned word from a stream of human speech. The fiber optic array was the most unique aspect of Sceptron’s design, loosely packing about 700 fibers into 1/4 cubic inch. When stimulated by mechanical excitation, the fibers, all of the same diameter but different lengths, would vibrate, each at its own natural frequency. A piezoelectric or electromechanical driver was provided to convert electrical signals into mechanical motion. A photocell then detected the motion of the fibers, registering the movement or lack of movement as a dark or light spot. Sceptrons were configured in pairs, one with a reference static mask, one as a memory mask, balanced together in a bridge circuit. See neural networks, pattern matching. Scheduled Transfer ST. A media-independent upper-layer protocol, which was originally developed as part of the HIPPI-6400 network transmission standard. schematic A diagrammatic representation of an electrical circuit, floorplan, network, or other interconnected system. Electronics drawings have conventions and symbols for various types of components and connections. Scheme A dialect of the LISP programming language, Scheme was developed by Guy Lewis Steele Jr. and Gerald Jay Sussman. It is dynamically typed, statically scoped, and tail-recursive, incorporating first class procedures. See LISP. Schilling von Cannstedt, Pavel Lvovitch (ca.17801836) A Russian diplomat posted to Germany, Schilling invented multi-needle and single-needle telegraph systems and a code to signal characters, numbers, and stop/finish/continue states. He collaborated with S.T. von Sömmering, who had developed an even earlier telegraph. Schilling’s telegraphs have variously been reported as being demonstrated in 1820, 1832, and in between. Given Sömmering’s inventions around 1809, it is plausible that Schilling’s telegraph may have been demonstrated as early as 1920. See Salvà i Campillo; Sömmering, S.T. Schroeder, Manfred R. (1926- ) A German scientist and educator, Schroeder was an early researcher in chaotic dynamics and microwave waveguides who was hired by Bell Laboratories Research in 1954. At Bell he turned his attention to the study of speech and hearing and headed up the acoustics and speech research projects from 1958 to 1969. Since Bell was a telephone company, there were many practical

applications for acoustics research including voice dialing, conferencing, speech recognition, text-tospeech applications, and more. In conjunction with B. Logan, Schroeder designed a speech compressor that was made available to the American Foundation for the Blind for the Talking Book program. In 1967, Schroeder was involved in the invention of linear predictive coding (LPC) and later in code-excited linear prediction (CELP), important contributions to the evolution of digital voice encoding and synthesized speech. While at Bell, Schroeder was named inventor/coinventor on 45 U.S. patents. In 1969, Schroeder returned to Germany where he became a professor and lecturer in various aspects of physics, including number theory, chaos, fractals, and nonlinear dynamics. He continued to work at Bell Labs for 5 months of the year and to maintain a strong interest in experimental acoustics, particularly in the area of generating speech through phase changes, in collaboration with H.W. Strube. Schroeder’s studies, especially in acoustics, have been honored with several medals and awards. See CELP; Harmon, Leon D.; Knowlton, Kenneth. Schrott effect In a cathode-ray tube (CRT), a random variation that occurs in the emission of electrons. Schweigger, Johann Salomon Christoph (17791857) A German physicist who contributed substantially to the development of the galvanometer and is credited as the first inventor of a practical version of the galvanometer. Schweigger studied electromagnetism and observed in the early 1800s that current passing through a coil could increase the magnetic influence of a needle. Building on the work of Ørsted, Schweigger continued with his research on electromagnetism and various configurations of conductors and, by 1920, had developed an electromagnetic multiplier that could detect very small amounts of attraction or repulsion, thus developing a practical means for detecting and measuring galvanic current. See galvanometer. SCI See Scalable Coherent Interface. SCIA See Smart Card Industry Association. SCO An AT&T specialized network maintenance organization providing a single point of contact for resolving customer network faults. SCO Unix The Santa Cruz Operation’s adaptation of Unix. See Unix, UNIX. scope 1. Generic term for any visual enlargement mechanism typically viewed through a narrow aperture, such as a microscope, telescope, or periscope. 2. colloq. A generic term for a bounded display device representing abstracted data that would otherwise be invisible to human eyes. Radar scopes enable translation of reflected radio signals into visual signals that are positionally displayed and oscilloscopes enable electrical signals to be displayed as waveform representations. See oscilloscope. score v. In the printing industry, to create a crease or indentation in the printing medium, usually heavy paper or card stock, so the medium can be easily and cleanly folded along the score line. Scoring is used in folded pamphlets, covers, and cards.

SCP 1. Satellite Communications Processor. 2. See Service Control Point. See Signaling System 7 (SS7). 3. See Session Control Protocol. SCR 1. silicon-controlled rectifier. 2. See sustainable cell rate. See cell rate for chart. 3. System Clock Reference. A synchronization time reference used, for example, in MPEG decoding. scrambler A device which rearranges or distorts a data communication or broadcast transmission to provide a measure of security. A descrambler is required at the end of the transmission to convert the information back into comprehensible form. Scrambling is a type of encryption, although the term encryption tends to be associated more with sophisticated data encryption schemes, and scrambling is associated more with the simple rearrangement of a few parameters, such as inverting audio frequencies. Black market descramblers are common, especially for television broadcast signals, since scrambling schemes are easier to decode than sophisticated key encryption algorithms. Scrambling and encryption are sometimes combined to maximize security. Scramblers are most commonly used to protect pay services like cable channels, but they are sometimes used to disrupt the transmissions of others, such as communications in war zones or traffic radar detectors. screen font A font specifically designed for optimal readability on a limited resolution computer screen (usually about 75 dpi). Taking a vector or raster font and scaling it to the type size desired on a computer screen does not always result in legible and aesthetic characters, especially at small sizes. For this reason, some operating systems will instead display a font especially designed to overcome some of the limitations. Thus, a system may include two types of fonts: screen fonts, and printer fonts. Ideally, printer fonts are vector fonts designed to print at the highest resolution of the printing device. For a printout that matches the screen fonts (e.g., a screen capture for a software manual), it is best to use a capture utility designed for this purpose. Scribner, Charles Ezra (1857 or 1858-1926) An American inventor and engineer, Scribner was chief engineer at Western Electric, after joining the firm at the age of 18. He had already patented a telegraph receiver at that age, and eventually held over 440 patents, more than any other single man in electrical history. One of his most significant inventions was the multiple telephone switchboard. Scribner founded the Western Electric engineering department, which later evolved into Bell Telephone Laboratories. SCRL See Signal Corps Laboratories. scroll bar A graphical user interface (GUI) device which serves two purposes: to indicate additional information beyond what can be seen in the current window or box, and to allow the user to scroll up and down (or across) the contents of the box by clicking on and dragging the scroll bar or by clicking on arrow indicators at either end of the scroll bar. A welldesigned scroll bar may have a third function – to give a proportional idea of how much information

is being viewed or hidden. Displaying a scaling drag area to match the size proportional to the total of the information contained in the listing, helps the viewer to perceive whether a little or much is hidden from view. Some scroll bars are designed so the scrolling speed accelerates the longer the listing and the longer the user holds down the scroll bar. This type of selectively accelerated scroll can be very handy and is perceived by most users as natural and comfortable. SCSI See Small Computer System Interface.

Traditionally, DB-25 (top left) and 50-pin flat connectors (top right) have been used to interconnect SCSI devices or to connect them to the host or peripheral card associated with the host. Since SCSI devices can be daisy-chained, it is important to terminate the last device in the chain. A common 25-pin SCSI terminator is shown (bottom).

SCSI connector An electrical/data connector supporting the data transmission requirements of the Small Computer System Interface (SCSI) standard. Traditionally, most SCSI devices (hard drives, cartridge drives, scanners, etc.) were connected with DB-25 or 50-pin flat connectors. However, more recent SCSI-2 devices use a connection with finer pins. See Small Computer System Interface. SCT Secretaria de Comunicaciones y Transportes. This state agency was given jurisdiction over communications for Mexico in the 1938 Law of General Means of Communications. It has played an important role in regulation and public services in Mexico’s telecommunications history. In 1992, telecommunications responsibilities were transferred to the Telecomunicaciones de Mexico. SCTE 1. See serial clock transmit external. 2. See Society of Cable Telecommunications Engineers, Inc. SCTP See Stream Control Transmission Protocol. SDL See Specification and Design Language. SDLC See Synchronous Data Link Control. SDLLC SDLC Logical Link Control. A Cisco Systems IOS feature which can provide translation between Synchronous Data Link Control (SDLC) and IEEE 802.2 type 2.

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SDH See Synchronous Digital Hierarchy. SDN See Software Defined Network. SDNS See Secure Data Network System. SDP 1. See Service Data Point. 2. See Service Discovery Protocol. 3. See Session Data Protocol. 3. See Session Description Protocol. 4. See Simple Discovery Protocol. SDSL single-line DSL. One of a number of optional configurations of Digital Subscriber Line telecommunications services. SDSL is intended to provide a basic DSL option delivering 1.544 Mbps data rates in both the upstream and downstream directions over existing copper twisted-pair wireline connections. See Digital Subscriber Line. SDTI See Serial Data Transport Interface. SDTP See Serial Data Transport Protocol. SEAC Standards Eastern Automatic Computer. A historic large-scale computer, undertaken by the U.S. National Bureau of Standards for its internal use in the 1940s. It was developed for installation on the East Coast. A similar system was built at the same time for the West Coast. SEAL Simple and Efficient Adaptation Layer. See asynchronous transfer mode in the Appendix for information about ATM adaptation layers. seal n. 1. A part designed to tightly close or close off a part, adjoining parts, or a container. Seals are sometimes used to make parts air- or watertight. 2. A security/tamper device designed to indicate whether the parts adjoining or underlying the seal have been opened or altered. It is common for technical components such as hard drives, internal parts to computers, and warranteed parts to be sealed by a plastic or metallic adhesive seal, or a dot of colored paint or resin. Breaking the seal may void a warranty. search and rescue radar transponder SART. As part of the new automated marine warning and safety measures implemented through the Global Maritime Distress and Safety System (GMDSS), ships are equipped with radiophone and/or radioteletype equipment in order to receive broadcasts of safety information provided over high frequency bands. One or more search and rescue radar transponders is required to be mounted in the vessel, which aids in locating the marine craft if it is distressed. The SART system creates a series of blips on the searching ship’s radar scope within a range that is under 10 miles. See Global Maritime Distress and Safety System, NAVTEX. search engine A software application designed to search and retrieve information from a database according to user-specified parameters or keywords. See WAIS. search engine, Web A software application combined with a Web site to provide search and retrieval of a great variety of information, such as newsgroup postings, personal or business names and addresses, individual Web pages, or Web site topics. Many include advanced search features with logical operations for more specific or complex searches. Considering the millions of sites on the Web, Web search

engines are indispensable. See Appendix C for a list of Web search engine sites. SECAM sequential couleur avec memoire; sequential color with memory. A composite color television standard developed in France and used also in the French colonies and western regions of the former USSR. It supports up to 625 scanlines at 50 cycles per seconds at a frame rate of 25 per second at 4.42 MHz, with an inverted signal that makes it incompatible with PAL, the other common format in Europe, and NTSC, the format used in North America. second 1. A brief unit of time defined as 1/60th of a minute in reference to a solar day. 2. A unit of time, designated in 1967 by the General Conference of Weights and Measures, as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom. See atomic clock. Second/Secondary Audio Program SAP. A secondary source of audio, usually a better quality audio or similar-quality audio provided in another language, that can be selectively chosen by a listener/viewer. For example, some television stations will broadcast the audio portion of a television program over another station (e.g., an FM station) or a separate signal in order to provide a better quality or different language audio option. Many televisions and VCRs have a SAP option built into the system to tune the second audio source for a TV broadcast. SAP is useful for educational programming, cultural programming (music), enhanced audio for the visually impaired, and for serving a local ethnic population. Section Terminating Equipment STE. In SONET networking, the STE may be a terminating network element or a regenerator between any two adjacent network elements (such as line repeaters or lightwave terminals). It can originate, access, and/or modify the section overhead, or terminate it, if needed. See SONET, Synchronous Transport Signal. Secure Data Network System SDNS. A system which incorporates the SDNS Message Security Protocol (MSP), developed as a cooperative project between government and industry participants and sponsored by the U.S. National Security Agency (NSA). MSP was specified to be integrated into the X.400 Message Handling System (MHS) environment. Secure HTTP, Secure Hypertext Transfer Protocol S-HTTP. A security-enhanced version of HTTP introduced in the mid-1990s. The original experimental version was designed to support multiple public-key algorithms, although a 1997 revision designates the Diffie-Hellman algorithm as the default. It is sometimes called HTTP/SSL. SSL was originally developed for transmitting private documents through the Internet via a browser (e.g., Netscape) and was later standardized as a transport layer security standard. See Hypertext Transfer Protocol, RFC 2616, RFC 2660, RFC 2716, RFC 2817. Secure Multipurpose Internet Mail Extension See S/MIME.

Secure Public Networks Act SPNA. An act of the U.S. Senate (S. 909) introduced by Senators McCain and Kerrey, in 1997. The Act would make it lawful for U.S. persons to use encryption, regardless of algorithm, encryption key length, or implementation; however, it differs from the Security and Freedom through Encryption (SAFE) Act in that it would require U.S. persons to use government-approved third-party encryption key escrow agents to hold spare copies of every encryption key. This type of key recovery system has been brought forward numerous times in the last few years and has always met with strong debate from the business community and privacy advocates. SPNA made it unlawful to use encryption to further the commission of a criminal offense and made it generally unlawful to decrypt communications without authority. This effort was one of the few bills supported by Louis Freeh, Director of the FBI. Exports would be limited to encryption products with 56-bit keys or less. It established a relationship between digital signature certificates and key escrow systems. The act was approved by the Senate Commerce Committee in May 1997 but was not brought to a full Senate vote due to a number of other options that were introduced. See Encryption for the National Interest Act, Security and Freedom through Encryption Act. Security and Freedom through Encryption Act SAFE. An important piece of legislation proposed as an alternative policy for protecting security and personal privacy at the same time as promoting electronic commerce. It has been a long process to work out the terms of SAFE, beginning in 1995. In February 1997, the SAFE Act was introduced with the same terms as H.R. 3011, proposed in 1996. The 1997 bill sought to ensure that Americans could use any type of encryption anywhere in the world and would be permitted to sell any type of encryption domestically. It further sought penalties against the unlawful use of encryption and promoted the relaxation of export controls over encryption algorithms and encryption-related products. Through the work of committees, the text of the original bill submitted by Goodlatte and Lofgren was significantly changed. Introduced into the U.S. House of Representatives as H.R. 695, in 1997, the bill amended title 18, U.S. Code to “... affirm the rights of United States persons to use and sell encryption and to relax export controls on encryption.” As with other privacy-related bills, there was significant debate and the bill was competitive with others, including the Secure Public Networks Act. In May 1997, the House Judiciary Committee unanimously approved SAFE, while agreeing to three amendments. In June, the House International Relations Subcommittee on International Economic Policy and Trade approved SAFE by a majority. Amendments and input from the House Intelligence Committee followed, with consideration of the Oxley-Manton amendment to criminalize the domestic use of strong encryption. This amendment drew

much debate from citizens and law professionals. By the 1999 106th Congress, there were two versions of the proposal. H.R. 850 dealt largely with the export of encryption products and had many implications for the Export Administration Act of 1979. Since it was first introduced, it broadened and became more lenient in terms of restrictions on personal and business use of encryption, essentially opening the door not only to using any encryption products but also in exporting them. It appears that the advocacy of privacy rights supporters and the competitive needs of U.S. exporters swung the pendulum in this direction. The Act subsequently went through many committees for markups and, in some cases, adoption. Under the terms of the Act, it is lawful for persons specified in the Act to sell any encryption, regardless of the algorithm, in interstate commerce. Thus, there would no longer be restrictions on the lengths of encryption keys, for example. It further states that the Federal Government and individual States may not require key escrow/key recovery information as was previously proposed in other bills. In terms of export, a highly contentious issue, SAFE stipulates that the Secretary of Commerce (with concurrence from the Secretary of Defense) has exclusive authority to control computer-related exports, including information security products, except for military uses. The Secretary would carry out a onetime 15-day technical review of entities wanting to export encryption-related products, after which no export licenses would be required, except where national security might be involved (e.g., per the Trading with the Enemy Act). This is a significant change over previous policies that strictly limited encryption key lengths, for example. Pressure from the industry and competition from foreign bodies providing encrypted products and encryption algorithms were probably the basis for this change of heart. The Act expressly stated that nothing in the Act shall limit the authority of the President under the International Emergency Economic Powers Act, the Trading with the Enemy Act, or the Export Administration Act of 1979. Thus, there would continue to be prohibitions on the export of encryption products to countries “... that have been determined to repeatedly provide support for acts of international terrorism...” To satisfy the concerns of law enforcement personnel, who increasingly worry that the ability of criminals to engage in surreptitious, global communications is outstripping the ability of law enforcement to monitor these communications, a stipulation in the Act stated that the Attorney General “... shall compile, and maintain in classified form, data on the instances in which encryption ... has interfered with, impeded, or obstructed the ability of the Department of Justice to enforce the criminal laws of the United States.” SAFE prohibits the use of encryption for hiding messages related to criminal acts. See AntiTerrorism Act of 2001, E-Privacy Act, Secure Public Networks Act. Security Associations SAs. Elements for containing information for the execution of network security

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services such as Internet Protocol (IP) layer services (authentication, encapsulation, etc.), transport layer or applications layers services, or protection of negotiation-related network traffic. See Internet Security Association and Key Management Protocol. Security Multiparts specification A specification for secure messages, separating the content data from the signature, and formatting them as multiple parts of a MIME communication. See S/MIME, RFC 1847. Security Protocols for Sensor Networks SPINS. Based upon the premise that in the future, wireless networks will be comprising millions of small selforganizing sensors, Perrig, Szewczyk et al. have proposed a set of security protocols to explore security issues in sensor networks. The SPINS work has arisen out of the SmartDust program at U.S. Berkeley, in which prototype multihop networks of small, low-power, sensor devices are being built utilizing the TinyOS event-driven operating system. It was discovered that workstation models of security were impractical in a low-power, multisensor environment, including Diffie-Hellman algorithms and digital signatures. There simply is not enough resource space to implement the usual methods. RC5 was chosen as the cryptographic primitive, but other shared key algorithms could be used. The researchers have presented information on µTESLA (a tight version of the Timed, Efficient, Streaming, Loss-tolerant Authentication Protocol) to provide authenticated streaming broadcast; on SNEP (Secure Network Encryption Protocol) for data confidentiality, two-party data authentication, and data freshness; and on an authenticated routing protocol using SPINS building blocks. Results of the project indicate that it is feasible to add security to severely resource-constrained sensor networks through symmetric cryptography. Seebeck, Thomas Johann A German researcher who described thermoelectrical effects in 1823, after observing a connection between electricity and heat. The Seebeck effect is named after him. SEED See self-electro-optic effect device. seek time A quantified description of the time it takes to locate specified information. In software, for example, this could be expressed as the average time in milliseconds or clock cycles it takes for a specific tool to locate queried information from a database of a given size. In hard storage devices, it could be expressed as the average time it takes for the read head to position itself on the track where the information lies. Industry definitions of seek times exist for specific types and sizes of devices. segmentation and reassembly A common process in packet-based networking of dividing up the packets so they can be individually processed or routed, and reassembling them at the receiving end to recreate the original message or transmission. seize To take control of a circuit or system so it cannot be used by others. Computer files are sometimes seized and locked so that the data cannot

be inadvertently modified simultaneously by more than one user. This helps protect data integrity. Transmission circuits may be seized to prevent interference on the line or to preserve privacy. Selective Sequence Control Computer SSEC. The successor to the Automatic Sequence Control Calculator, better known as the Harvard Mark I, instigated by IBM in 1948. By this time a number of different designers and manufacturers were getting involved in the development and marketing of largescale computing machines and IBM was motivated by the competition. Machines built around this time represent a transitional evolution from calculator/ tabulators to computing machines in common understanding. selenium A substance which was first isolated in the early 1800s, selenium’s light-sensitive properties were noted by British scientists in 1873, which subsequently led to many of the important early experiments in television transmissions using selenium. As the technology evolved, selenium came to be used in television cameras. self-electro-optic effect device SEED. A quantum well-based photonic optical device used for photonic switching, developed in the AT&T Bell Laboratories in 1987. This multi-element device, when biased by an external voltage, creates an external field that shifts the wavelength of the onset of absorption which, in turn, causes the intensity of transmitted light to vary. Optical sensors can be used with a SEED system to detect the resulting light. This suggests the possibility of developing light-based switching mechanisms and optical logic. SEED latches were described in the late 1980s and the first SEED devices were created in the late 1980s and early 1990s. In December 1989, Bell Labs announced the development of a very high-capacity gallium-arsenide photonic integrated circuit capable of processing 2 kbits of optical information in parallel. Each element in the chip array is a Symmetric-SEED (S-SEED) which can function as a logic gate, memory cell, or switch. Illumination from a low-power light beam can be used with the S-SEED to cause it to switch in less than a billionth of a second. This has important implications for parallel processing, as complete arrays can be simultaneously accessed. With the spread of optical communications technologies, scientists have been seeking ways to make the physical transmission path all-optical. SEED elements have possibilities as optical memory cells once the means to combine them more effectively into arrays as been worked out. This, in turn, could support the development of an all-optical switching mechanism (e.g., an optical ATM switch). Within the U.S. Navy, J. Bechtel has described research on logic systems for solving Boolean equations based on a Symmetric-SEED (S-SEED) system. A single light source could potentially be split into a matrix of light beams, which are then modulated by a Symmetric-SEED-based spatial modulator and the individual members in the array reset according to Boolean inputs. The value of the remaining

member, unaffected by inputs, would correspond to the Boolean solution with the result signaled by a matrix of equal intensity light beams onto a detector. U.K. researchers, with help from a grant from the European Union, have developed a digital optical network for image processing based upon self-linearized SEED (SL-SEED) concepts. By exploiting the fact that SEED responsivity can be increased by application of voltage, a feedback loop can be established. The modulator photocurrents and detector influence one another until the photocurrents of both match. The photocurrent is proportional to the input light minus the reflected light. The detector photocurrent is proportional to the control light input. Control can then be “subtracted” from the signal. For image processing, an element must then interact with neighboring elements. See electroabsorption, quantum well, Stark effect. semaphore A visual signaling system employing movable apparatus like arms or flags. Individual symbols, words, or instructions are made to correspond to distinct positions of the arms or flags. While electronic communications have superseded most semaphore systems, they are still sometimes preferred in situations where electronic messages might be overheard. See Chappé, Claude.

France had an extensive system of semaphore signaling before the telegraph was invented. Weather and constant monitoring were two disadvantages of the semaphore system.

semaphore, programming 1. An access or exclusion indicator, such as a variable flag. Semaphores are useful for controlling file locks to preserve data integrity. In other words, they can be used to prevent multiple users from accessing a file simultaneously and changing data in a way that could disrupt the information or corrupt the data. 2. A low-level integer variable having only nonzero values; a primitive which can be used for synchronization in concurrent processing implementations. semiconductor A material widely used in electronics due to its relative balance of electrical conducting

and insulating properties (hence the name semiconductor). Semiconductor materials are typically crystalline in structure, and their properties of enabling or impeding the flow of current are used in designing solid state electronic circuitry. Materials commonly used to create semiconductor components include silicon, germanium, and gallium arsenide. Doping, the addition of other elements, is used in the creation of semiconductors to further control and enhance their properties. Current flow in semiconductors is commonly controlled by electricity, but may also be controlled by the influence of light or magnetic fields. Semiconductors are important materials used in the manufacture of integrated circuits. See integrated circuit. Semiconductor Industry Association SIA. The leading U.S. trade association for the microchip industry, established in 1977 by pioneers in the industry. The SIA promotes and supports the competitiveness of the U.S. semiconductor industry and represents its membership through input to government representatives. It also researches and reports on possible health hazards related to the semiconductor industry. In 1982, the SIA formed Semiconductor Research Corporation (SRC) to plan, direct, and fund precompetitive silicon research projects at major academic institutions. In 1985, the organization submitted input to the U.S. government regarding the balancing of trade practices between Japan and the U.S. In 1987, SIA formed SEMATECH, a consortium of chap manufacturers dedicated to improving semiconductor manufacturing technologies. In 1997, the Focus Center Program was established to engage in long-term research to ensure the long-term viability of the industry. sensor glove, data glove A human interface device which fits over the hand and uses electronics to translate hand movements into signals which can be interpreted by a software program. Data gloves are used for many purposes: video games, virtual reality environments, special effects in movies, experimental computer interfaces, and scientific studies in human movement and perception. They are often combined with special types of monitors mounted in helmets, on glasses, or on tiny headsets in order to facilitate natural movement and the illusion of a 3D virtual environment. SEQUEL See SQL. sequential A nonoverlapping succession or series, in chronological or data order, with no significant intervening time or data. See concurrent, consecutive, parallel, serial. serial clock transmit external SCTE. A data stream common to serial cables used to connect computer modems. For example, on 25-pin serial communications connections, one of the pins may be assigned to carry the external clock signal from the data terminal equipment (DTE). serial communication A means of transferring data one element at a time, often through a single wire or trace in a circuit. While it may not seem very fast or efficient, serial communication is easily

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implemented and very commonly used in computing systems. The RS-232 standard is the most common specification for the physical/pin connections for serial communications. See modem, parallel, RS232. Serial Data Transport Interface SDTI. An emerging packet data standard for the transport of audio, video, and data among various multimedia systems, including video servers, cameras, VCRs, editing systems, etc., especially in professional broadcast video environments. SDTI provides a network environment for video data exchange, without a lot of network overhead. It supports single-direction, pointto-point, compressed-data connections. SDTI has been well received due to the many advantages of digital systems, including the reduction of generation loss common to analog editing and transmission loss associated with analog broadcasting. SDTI (SMPTE 305M) evolved from SDI (SMPTE 259M), which is used for transporting uncompressed audio/visual signals between digital broadcast and post-production devices. The two formats are mechanically and electrically compatible to support coexistence in the same facility. SDTI, developed by the SMPTE PT20.04 Workgroup on Packetized Television Interconnections, extended this concept by enabling compressed video to be exchanged without the need for frequent compression/decompression processes that could slow or degrade the transmission. SDTI has been recommended by the EBU/SMPTE Task Force for Harmonized Standards for the Exchange of Programme Material as Bitstreams.

Serial Data Transport Protocol SDTP. A network data protocol which provides a means of transporting serial data streams over PPP links. SDTP arose out of the work of the TR30.1 ad hoc committee in the mid-1990s to provide a standard means for synchronous data compression. SDTP specifies a transport protocol and an associated control protocol (PPP-SDTP and PPP-SDCP) to be used in conjunction with PPP protocols. See Point-to-Point Protocol, RFC 1963. serial interface card A printed circuit card which fits into a slot in a computer or other computerized device or piggybacks on a motherboard to provide standardized electrical connections for the synchronous serial transmission of digital data. The connection on the card is typically a 25-pin D connector. On consumer desktop computer systems, most serial interface cards support data rates up to about 28,800 or 38,400 bps. A serial interface card is a common way to connect remote computer terminals and data modems to a computer. See RS-232. Serial Line Interface Protocol, Serial Line IP SLIP. Originating with an early 1980s 3COM UNET TCP/IP implementation, SLIP became a de facto standard encapsulation protocol for serial lines, used for point-to-point communications with TCP/IP. SLIP has now been superseded by Point-to-Point Protocol (PPP). See Point-to-Point Protocol, RFC 1055. SERN See Software Engineering Research Network. server A system which provides services to other computers connected to it through a network. A server may store and administer software applications,

Service Environments and Systems The following definitions are related to Service architectures that can be used in conjunction with Intelligent Networks (INs). See also Intelligent Network Service Access Code SAC. A specific telephone prefix access code (e.g., 800) for a specific category of service such as toll free numbers. See Service Management System. Service Control Point SCP. A point that provides access to an Intelligent Network (IN) database, which is connected to a Service Management System (SMS), and which accesses Internet Protocol (IP) as needed. SCPs are a mechanism for providing advanced services by processing the format or content of transmitted information. Information contained in the SCP may be downloaded by phone service carriers. Architecturally, the Service Control Point is somewhat self-contained, providing services to Intelligent Networks (e.g., those based upon Signaling System No. 7) that architec-

turally separate switch and service functions. Service Switching Points (SSPs) can relay value-added service calls to the SCP which can appropriately complete the call. The ITUT describes the SSP in Recommendation Q.1205. Service Creation Environment SCE. In the context of Service Control Points interfacing with Intelligent Networks (INs), the SCE enables new telecommunications services to be quickly designed and implemented without necessitating changes in the IN switching system. Service Creation Environment Point SCEP. A protocol used for defining and developing a service, for example, for implementing security features and validating services in networks (often in conjunction with LDAP). The SCEP creates service in conjunction with Service Independent Building-blocks (SIBs) and interfaces with the Service Management Point (SMP). The ITU-T describes the SSP in Recommendation Q.1205. Service Data Point SDP.

Service Environments and Systems, contd. A standard database designed for use with Intelligent Networks (INs). Contemporary phone services are complex compared to historic analog residential/business telephone lines. Users now have different services from different carriers and different variations of those services offered through bundles, specials, prepaid cards, and according to what carriers make available in specific regions. These services are stored, configured, and managed through software that must be associated with specific subscribers or paid calling card access. The SDP works in conjunction with Service Control Points (SCPs) to manage this enormous task. In SDP, the customer information is separated from the logic that manages the services. This compartmentalization is important for the privacy of subscribers and also enables updates, maintenance, and new services to be easily integrated into the system without side effects in other areas. Fast processing and large data storage facilities are needed to make the system viable. The ITU-T describes the SDP in Recommendation Q.1205. Service Discovery Protocol SDP. A wireless network resource discovery protocol from Bluetooth that enables applications/devices to seek out and find compatible devices with services that may be useful. Thus, using SDP, Bluetooth devices can connect wireless to nearby services such as printing, digital cameras, etc. SDP was specified by the Bluetooth SIG in 1999. SDP defines how a Bluetooth client application shell discovers available services and their defined characteristics, without prior knowledge of the services, as the device enters the accessible “region of access” of the services. SDP also makes it possible to detect when a service is no longer available. In March 2001, RidgeRun, Inc., announced support for the Bluetooth technology by releasing an Open Source SDP enabling Bluetooth users to get broader access to on-demand wireless services. Service Management Access Point SMAP. In a network architecture, the SMAP interfaces with the Service Management Point and assists in managing user access and services. The ITU-T describes the SSP in Recommendation Q.1205. See Intelligent Network. Service Management Point SMP. In an Intelligent Network (IN) architecture (e.g., SS7), a centralized manager interfacing with a number of other elements such as the Service Creation Environment Point (SCEP), a Service Management Access Point (SMAP), and various Service Control Points

(SCPs) and other elements to satisfy valueadded service calls from the Service Control Point (SCP). The ITU-T describes SSP in Recommendation Q.1205. See Intelligent Network. Service Management System SMS. A centralized interactive computer system dedicated to coordinating network servicerelated information. The national 800 numbers are managed in a central database computer from IBM. This is one type of Service Control Point providing value-added services to Intelligent Networks (INs) known as SMS/ 800. See SMS/800. Service Profile Identifier SPID. When hooking up ISDN BRI services, the carrier provides the user with a SPID for each number installed, typically two. The SPID points to a memory location in the carrier’s central office where ISDN parameters, including which services are enabled for a particular subscriber, are stored. As not all phone carriers have automatic SPID detection, some newer modems can determine what type of ISDN service is connected and configure the SPIDs accordingly. When connected to carriers with automatic SPID detection, they can configure themselves whether or not a computer is attached to the modem. Modems with these capabilities help compensate for some of the problems traditionally associated with the installation of ISDN services. It is recommended that the subscriber keep a record of SPID numbers filed away somewhere, as it’s easier to look up a lost SPID than to get it again from the phone carrier. Service Switching and Control Point SSCP. An entity in the physical plane that controls network resources and sessions, including the Service Control function, Service Data function, and Service Switching/Call Control functions. Service Switching Point SSP. An entity in the physical plane, the SSP is a point providing local access and an ISDN interface for a Signaling Transfer Point (STP), which, in turn, provides packet switching for message-based signaling protocols in an Intelligent Network (IN). The SSP can be implemented as a central office switching system capable of communicating with a Service Control Point (SCP) in order to enable switched calls to be routed through a somewhat separate service environment that will then complete the call. The ITU-T describes the SSP in Recommendation Q.1205. See Intelligent Network, Service Control Point.

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security measures, access to peripherals or external systems, etc. The server does not necessarily have to be an enhanced system, as servers can be specialized as print servers, mail servers, etc. (and several servers may be on a system), but servers performing the bulk of centralized or generalized tasks often have more memory, processing speed, and storage than other systems on the network. The software is probably the most important aspect of a good server. Good network software is robust, configurable, and usually fully multitasking. There are many well-tuned network workstation options that are reliable and do not crash, except in the most unusual of circumstances. Shop around when selecting network server software; paying a few hundred or thousand extra dollars in terms of the initial cost can often be recouped in six months or less through savings on downtime, software reinstallation, and administrative costs that accrue on unreliable systems. server agent In server/client systems, software that handles the major processing or protocols and serves a request from a client as a Web server, mail server, or FTP server. Server Message Block protocol SMB. A client and/ or server request-response network protocol for sharing resources such as files, ports, printers, and other useful services. SMB was defined by IBM in the mid1980s and is prevalent on Windows-based systems. It works in conjunction with NetBIOS over TCP/IP. In conjunction with Samba, it can also be used with Linux systems. SMB is also known as Common Internet File System (CIRS). See Samba, SMB Project, RFC 1001, RFC 1002. Service Advertising Protocol See Service Location Protocol. Service Agent A network utility which, when queried, provides information about a network service (printer, modem, etc.) such as its URL. service bureau A center providing services that usually require specialized equipment and/or expertise. Copy centers, private postal centers, data entry services, and facsimile centers are examples of common service bureaus. Service bureaus commonly arise when a service is needed on an occasional basis by many businesses or individuals and who don’t have the equipment or the expertise to do the job themselves. See outsourcing. Service Location Protocol SLP. An intelligent resource discovery and registration protocol developed in the mid-1990s. Described as a “quieter” alternative to Service Advertising Protocol (SAP), SLP includes extended attributes information to reduce network traffic queries. Thus, a printer may be described in terms of its capabilities (such as duplex printing, PostScript-capable, tabloid paper) and found transparently, without the user querying for its IP address. See Service Advertising Protocol, Service Agent, SLIP, RFC 2165. service quality Standards of service established by businesses that include such things as service without outages, available lines without lag or busy signals, technical support availability, good data integrity, etc. This is not the same as quality of service

(QoS), which has a more specific meaning. Service-Specific Connection-Oriented Protocol SSCOP. A B-ISDN signaling ATM adaptation layer (SAAL) mechanism for managing the establishment, monitoring, and release of data exchanged between signaling peers. In the context of Q.2931, SSCOP provides error and flow control signaling services somewhat analogous to those provided by TCP for Internet Protocol (IP). Service-Specific Convergence Sublayer SSCS. A component of the ATM adaptation layer (AAL) that coordinates protocols of the next higher layer with the requirements of the next lower layer, the Common Part Convergence Sublayer (CPCS). See asynchronous transfer mode. services-on-demand SoD. Services provided to an audience on a request basis, rather than on a scheduled broadcast basis. The concept is not new; in fact, it has been available for media services for over 100 years, but new digital technologies are providing automated services, thus making available cost-effective SoD delivery options which were not previously possible. See audio-on-demand, video-on-demand. Session Announcement Protocol SAP. A network protocol for sending announcements to users that is common to broadcast communications. It is considered distinct from broadcast content and data triggers. SAP version 2 was submitted as an Experimental RFC by Handley et al. in October 2000. A SAP announcer periodically multicasts an announcement packet to a known multicast address and port. The SAP recipient “listens in” on a SAP address and port for multicast scopes and thus learns of all the sessions being announced so that the sessions may be joined. See enhanced TV, RFC 2974. Session Control Protocol SCP. A simple client/ server network protocol to facilitate multiple conversations over a single TCP connection. With SCP, parties can establish (or reject) a virtual session over a single transport connection. Session Description Protocol SDP. A network protocol used for announcements and other notifications for multimedia broadcasts. The protocol was described by the Multiparty Multimedia Session Control (MMUSIC) working group of the IETF and was submitted as a Standards Track RFC by Handley and Jacobson in April 1998. SDP provides session support for Internet multicast backbone (Mbone) services and more general realtime multimedia services. The protocol is not intended for the negotiation of media encodings. SDP is designed to convey session directory information to recipients that can be used in conjunction with a variety of transport protocols, such as Session Announcement Protocol, Hypertext Transport Protocol, and others. See Session Initiation Protocol, RFC 2327 Session Initiation Protocol SIP. An applicationlayer signaling protocol for creating, changing, and terminating Internet-based telephony, conferencing, messaging, and events notification involving one or more participants.

SIP was originally developed with the IETF Multiparty Multimedia Session Control (MMUSIC) working group and continued, as of September 1999, by the IETF SIP working group. Internet Drafts were submitted by the SIP working group in May and October 2001. SIP invitations provide a means to convey session descriptions so that compatible media types can be agreed upon by participants. Proxy servers are used to help route requests to users and to assist in firewall traversal. SIP runs on top of a number of different transport protocols. See Session Description Protocol. See RFC 2543, RFC 3050, RFC 3087. Session Initiation Protocol Forum SIP Forum. A nonprofit association to promote and support Session Initiation Protocol, formed in June 2000. See Session Initiation Protocol. http://www.sipforum.org/ SET secure electronic transaction. A phrase used in electronic commerce to signify a transaction which is protected by various network security measures such as authentication and verification procedures, digital certificates and signatures, secure servers, etc. set-top box colloq. A media device which sits on top of a TV set or within a home entertainment component cabinet to hook into the system in some way. Set-top boxes provide a variety of capabilities, including conversion of cable TV signals, provision of WebTV services, etc. Some set-top boxes are proprietary units offered through lease or purchase by a service provider or vendor. SETI Search for ExtraTerrestrial Intelligence. An interesting, federally funded scientific project in which arrays of radiotelescopes are used to search for signs of intelligence in other parts of the universe. The movie Contact (Warner Home Video) provides an idea of a SETI-like project. The rationale of SETI is that signals can be sent farther and faster using radiowaves than by sending spacecraft (SETI is also in favor of spacecraft missions and radio signals sent from spacecraft) and that it’s worthwhile to send out signals in the hope that other life forms may intercept them or that humans may intercept the transmissions of other life forms. Unfortunately, to date, no signs of sentient communications have been detected, but SETI concepts have resulted in the discovery of interesting radiowave signals from distant celestial objects. The Columbus Optical (COSETI) Observatory, a pioneering observatory located near Columbus, Ohio, conducts searches for extraterrestrial intelligence in the optical spectrum. http://www.seti.org/ http://www.coseti.org/ SF 1. single frequency. 2. See SuperFrame. SF signaling See single-frequency signaling. SFTP See Simple File Transfer Protocol. SGML Standard Generalized Markup Language. A markup standard adapted by the International Organization on Standardization (ISO) in 1986 which is not a language, but is designed for specifying the content and structure of a document or document language, with the assumption that the actual output or display of the document may vary according to the

output device. SGML allows the development of cross-platform applications and documents, and a document can be processed by an SGML compiler by referencing a document tag definition (DTD). HyperText Markup Language, widely used on the World Wide Web, is a descendant of SGML that incorporates some of its capabilities. Yuri Rubinsky (1952-1996) was one of the pioneers who enthusiastically did much to promote the use of SGML through educational programs. SGMP See Simple Gateway Monitoring Protocol. SGRAM synchronous graphics random access memory. A type of memory optimized for use in memory-hungry graphics applications, particularly 3D rendering and ray tracing. shadow mask A type of cathode-ray tube (CRT) color display technology which incorporates a thin, perforated metal plate mounted close to the front of the inside of the tube to create a mask through which red, green, or blue (RGB) phosphors can be selectively excited. See cathode-ray tube. Shannon, Claude E. (1916-2001) A celebrated American theorist who contributed significantly to the study and understanding of information theory. The history of communications emphasizes the inventors, programmers, and hobbyists who have developed the mechanisms and operations of information systems, but few people at the time had taken a broad look at what information is, how it relates to the technology (e.g., channel capacity), and what the process of conveying information entails from a more abstract, theoretical, statistical, and broadly practical viewpoint. Shannon, while working at Bell Laboratories, is credited with bringing together and clearly stating fundamental theories of information in 1948. Shannon is often credited as wholly developing information theory, and his work may have been done independently of Erlang and Kotel’nikov, who developed similar theories many thousands of miles away, but it is derived at least in part from the work of Harry Nyquist, who is cited in Shannon’s writings. Nyquist developed principles of communications rates and digital sampling in the 1920s. See Erlang, Agner; Kotel’nikov, Vladimir; Nyquist, Harry; sampling theorum. Shannon-Harltley Capacity Theorem A theorem that facilitates calculations for assessing an environment with additive white Gaussian noise and its implications for relative capacities in communications channels. In other words, capacity has been mathematically defined in relation to bandwidth, energy per bit, and noise power density, to yield useful information about total signal and noise power, and bandwidth efficiency (in bits per second per Hertz) in communication technologies. Shared Facility Centers A telework organization similar to a branch office, but co-owned or partially community- or freelance professionals-funded, situated in a residential or rural village area, and made commercially viable by the implementation of new communications technologies. See ADVANCE Project, telework.

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shared tenant services STS. A category of services that applies to residents living in multiple family dwelling units. In these types of residences, cable services, antennas and other communications facilities are often shared among a group of residents within a complex, section, or building. The distinction is important because, historically, many of these residents have been served by independent private carriers considered distinct from local exchange carriers (LECs) and thus are not bound by the same regulatory framework. With the advance of technology, private service provider services are becoming more like LEC services and thus are debated and evaluated in the context of changing technologies. ShareMail A Windows-based email support utility that enables a public email account to be expanded to serve several internal mailboxes. It is thus a local email server for local area networks (LANs). ShareView 3000 A Macintosh-based videoconferencing system from Creative Labs which supports audio, video, whiteboarding, application and document sharing, and file transfers over analog phone lines. An IBM-licensed PC-version called ShareVision PC3000 is also available. See Cameo Personal Video System, Connect 918, MacMICA, IRIS, VISIT Video. Shaw, Wiliam Chester An Ontario-born Canadian who invented the IMAX motion picture system in the 1960s. This large-format film technology provides startling realism and detail. See IMAX. shear In image processing software, to shear is to alter the shape of an object to displace it sequentially in one direction or the other, through one axis. For example, if you take a rectangle and shear it along the X axis (horizontally), either the top or the bottom stays in one place and the opposite top or bottom follows the pointing tool so that it becomes a parallelogram that somewhat resembles a diamond. Shearing a straight vertical bar through the X axis would result in a longer straight bar at an angle (actually, it may have jaggies, depending upon the visual resolution, but mathematically it remains straight). Shearing the same bar through the Y axis would simply lengthen the bar. A good shear tool will allow you to select the axis of shear, although many permit shearing only through X or Y.

A simple example of a rectangle “sheared” through one plane (horizontal).

sheath n. A close-fitting protective covering, usually tubular, often made of plastic. Sheaths can be used to bundle wires, to insulate, to protect from moisture or wear, or to provide identifying colors or symbols. They are commonly used on conducting wires and fiber cables. See conduit.

sheave The round, usually rotating track in a stringing block used to direct a line conductor that is being installed, removed, or temporarily redirected for maintenance or repair. See stringing roller. shelf life The useful life of products in terms of physical functioning, public demand, or profitability. Most electronic products currently have a very short shelf life in terms of the compatibility and hence viability of the technology. Unfortunately, the short shelf life is not related to physical deterioration; the products are perfectly usable and obsolete only because of lack of market demand. The shelf life of computers has changed from years to months and, for individual components such as modems and high capacity storage devices, may be only weeks. This results in massive quantities of unsellable products on warehouse shelves and companies scrambling to unload inventory of perfectly good products. shell, command shell A computer user interface input and display environment which translates user commands into operating system instructions. Sherman Antitrust Act An important 1890 U.S. act passed to prevent the establishment of monopolies which could hinder U.S. trade and competition. SHF super high frequency. About 3 to 30 Ghz, used for satellite transmissions. ship to shore telephone See marine telephone. shock, electric A sudden, often hazardous, electrical stimulation to a living body which may greatly affect nerves and cause convulsive contractions through muscles, possibly endangering the heart muscle. It may also cause severe burning, confusion, and unconsciousness. Light electric shocks are uncomfortable, but not always dangerous and are sometimes used as perimeter boundaries for livestock or secure areas. Light electric shocks are also used in animal experiments for studying the nervous system and are occasionally used in riot control and law enforcement. It is unwise to open up or attempt to repair cathoderay tubes (CRTs), which may store a considerable charge, without careful preparation and knowledge of safety procedures. Electric shocks must be taken seriously and, if severe, may require contacting emergency services or the application of cardiopulmonary resuscitation (CPR). Never touch someone who is experiencing shock from an electrical source until the electricity is turned off or the source of the contact knocked away with a nonconducting material. Consult emergency first aid sources for information. Shockley, William Bradford (1910- ) An Englishborn American physicist who worked in the Bell Telephone Laboratories from 1936. He discovered the rectifying properties of impure germanium crystals at a time when vacuum tube rectifiers had replaced the old galena and carborundum crystal detectors. This led Shockley to explore the various impurities in germanium and he found electron drift toward the positive or negative pole under controlled conditions. When these solid-state rectifiers were combined, the transistor was born and vacuum tubes

superseded. One of the most significant consequences of transistors at the time was miniaturization of communications devices and room-sized computing machines. Shoemaker detector A type of electrolytic detector that incorporates a battery and, consequently, requires no outside power source. It consists of a glass tube with a platinum-sealed point, with a zinc strip rather than the platinum point coming in contact with a mild sulphuric acid solution. Shoemaker detectors were used commercially in wireless telephone receivers in the early 1900s. See electrolytic detector. short See short circuit. short circuit An unintended or harmful cross connection, of low resistance, of electrical circuits. Short circuits can occur from an excess of solder, incorrectly connected wires, conductive debris (such as a screw falling into a circuit box), worn-out insulation in bundled wire, water, or physical bumping of electric conductors, etc. The result is often a sudden flow of current in the wrong direction or of the wrong magnitude, which can potentially damage components. Some systems are configured to shut down or blow a fuse or breaker in the event of an excess of current or other abnormal electrical activity. See burst, spike. short haul A short travel or installation distance. The actual length depends upon the situation or medium employed. A short haul for a SCSI cable is about 3 feet or less; above 6 feet, serious signal degradation occurs and special hardware is needed for distances over 12 feet (see Fibre Channel). A short haul for other media may be several yards or thousands of miles. short haul modem A software/hardware combination used for short distance communications up to a couple of dozen miles, usually over a copper singlechannel line. See baseband modem. Short Message Service SMS. A global, wireless, low bandwidth, two-way service first distributed in Europe in the early 1990s and later in North America. SMS provides the capability of transmitting alphanumeric messages between mobile systems and external systems that support paging, email, and voice mail. The handsets used in these services can send or receive at any time, regardless of whether a data or voice call is in progress. SMS is appropriate for applications like stock quotes, paging, short fax and email messages, online quick banking, etc. Short Message Service Center SMSC. A relay and administrative center for Short Message Service (SMS) which provides store and forward services. This is somewhat like an enhanced alphanumeric paging system with two-way service and guaranteed delivery. See Short Message Service. shortwave, shortwave Long-range radio transmission frequencies in approximately the 1.6 to 30 MHz range, above the commercial broadcast bands. Shortwave signals are easier to apprehend at night, due to lowered atmospheric noise and the fact that many shortwave broadcasters prefer to send in the evening hours. Coordinated Universal Time (UTC) is often

used as the reference time for broadcasts. The Internet has sites that list broadcast times and frequencies for various shortwave stations around the world. See microwave, ionospheric wave, radio. SHOT See Society for the History of Technology. shrinkwrapped products Products that come ready to use off the shelf that require little or no configuration or customization. Shrinkwrap software is generally that which is intended for a mass market. Contrast to custom software written to a customer’s specifications, written for a small market segment, or provided by consultants. SHT Short Hold Time. Shugart A historic disk development company. Shugart floppy disk drives were used on some of the earliest microcomputers. shunt n. A switch, pipe, detour sign, or other diverting mechanism. shunt, electrical In electrical circuits, a means to divert some or all of the current. A shunt is sometimes used to divert part of a current in order to prevent damage to sensitive measuring instruments. Temporary shunts are sometimes established with jumper wires or alligator clip connections. shunt circuit, bypass circuit, detour circuit A circuit configuration through which a specific portion of the current is redirected or subdivided. Often used for diagnostic purposes, temporary arrangements, or circuits in which variable conditions are accommodated or where the original current can be more effectively used by dividing it. Shunts are sometimes incorporated into the internal workings of diagnostic instruments. shunting error A condition in which current divided through two circuits, as through a component and a measuring instrument, will vary depending upon the frequency. See reversing error. Shuttle Amateur Radio Experiment SAREX, SAREX-2, SAREX-II. A series of amateur radio experiments consisting of equipment and procedures carried as payload aboard a number of U.S. space shuttles. SAREX was designed to provide an opportunity for school and community groups to communicate with astronauts in space and for conducting communications experiments with ground-based amateur radio operators. SAREX was later integrated into the International Space Station project and has even been used for emergency messaging. Amateur radio has a long history of cooperation with U.S. aeronautical/space programs leading up to SAREX. In November, 1983, Astronaut Owen Garriott (W5LFL) took his amateur (ham) radio into orbit on the Space Shuttle Columbia STS-9 mission and communicated with Earth amateur radio stations. This tightened the relationship between ham operators and shuttle crewmembers and the experiments continued on future shuttle missions of Columbia, Challenger, Atlantis, Discovery, and Endeavor. Many astronauts are licensed amateur radio operators. In several cases, the entire crew of a space shuttle mission comprised ham operators (e.g., STS-74).

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There has long been a good relationship between the space program and the amateur radio community. As part of SAREX, amateur radio enthusiasts and the wives of Space Shuttle Challenger astronauts Fullerton and England viewed monitors showing images of the astronauts’ wives that were transmitted to Shuttle crew members. [NASA/JSC image detail, July, 1985.]

As examples of specific missions, a SAREX payload was carried aboard the Space Shuttle Columbia in 1993 and the Space Shuttle Endeavour in 1993 and 1994. The SAREX-2 amateur radio system was used to contact elementary and middle school children from space on October 22, 1993. SAREX-II was used in 1994 to contact school and Boy Scout groups and also to communicate with Russian cosmonauts aboard the MIR space station. Amateur radio communications were monitored in realtime by amateur radio stations via rebroadcasts and the telebridge system. SAREX-II was further used to communicate with the Star City training center outside Moscow, Russia, on 16 April 1994. SAREX evolved into Amateur Radio on the International Space Station program (ARISS). The American Relay Radio League (ARRL) chronicles the full history of the interesting SAREX and pioneer amateur radio experiments in their publications and on their Web sites. NASA provides instructional support materials for SAREX participants on their Division of Education Educational Services Web site. See Amateur Radio on the international Space Station, America Relay Radio League, AMSAT.

Two members of the Spacelab Life Sciences crew, McArthur and Searfoss, training with amateur radio equipment for Space Shuttle mission STS-58 in September 1993. [NASA/JSC image detail.] The major unit in an early SAREX containing a slow scan video converter, control circuits, and power supplies. The small tape recorder enables recording of video image data on tape for retransmission through the SAREX equipment. [NASA/JSC image, June 1985.]

Endeavour Astronaut Linda M. Godwin uses the Shuttle Amateur Radio Experiment, as did several of the other STS-59 crew members, to communicate from space with ham radio operators and students on Earth. [NASA/JSC image, April 1994.]

SIA 1. Securities Industries Association. 2. See Semiconductor Industry Association. Sibley, Hiram (1807-1888) Sibley founded the New York and Mississippi Valley Printing Telegraph Company which took on the name of Western Union, suggested by Ezra Cornell in the mid-1850s, when it began westward expansion. Sibley remained president during the expansion and Western Union installed the first transcontinental cable in 1861. After the failure of Western Union’s first Atlantic cable, Sibley traveled to Russia to investigate the installation of a Siberian-Alaskan communications line, and the Russians offered to sell Alaska to Western Union. Sibley turned down the offer, but alerted the U.S.

government to the opportunity. Along with his colleague, Ezra Cornell, Sibley helped to found Cornell University. See Western Union. side circuit In telephone installations and other circuits where additional endstations are desired, but where resources are limited, a side circuit is a means to build an additional circuit using the resources of two adjacent circuits. See phantom circuit. side lobe SL. In a directional antenna, any segment generating a lobe in the antenna pattern other than the primary/main lobe. Antenna patterns are often diagrammed with a radiating region around the segment, a region of influence that appears lobe-shaped. In a Cartesian coordinate system, the lobe shows up as a pronounced hump or “shoulder.” Side lobe peaks are often described in terms of their ratio to the main lobe peak and will vary, depending up the shape of the antenna, its electrical characteristics, and the frequencies transmitted. Depending upon the configuration, an antenna may have several side lobes. In general, low side lobes are desired. Antennas that are likely to be physically adjacent to one another (toll booths, cell phones, even satellites, etc.) are often designed to deliberately suppress side lobes. In radar sensing, side lobe signals can muddy the radar signal and cause confusion. Sometimes an omnidirectional antenna separate from the main antenna is used to send out a reference pulse that is lower than the signal from the main antenna, but stronger than the signal from its side lobes. This enables the transponder to make a few calculations and determine whether a signal came from the main antenna or the side lobe. It can then respond or not respond as appropriate. Antenna pattern modeling programs are ised for generating and assessing the configuration and influence of side lobes (including thermal emissions). Side lobe interference in antennas can be a problem, but it is not restricted to larger physical structures; side lobe issues are also important to small-scale transmissions phenomena such as laser light paths. In optical network links, side lobes can result from various structures integrated into the optical fiber to enhance its transmission qualities. For example, Bragg gratings suffer undesired effects from side lobes in their spectral response. This can reduce the usable bandwidth. side lobe dispersion An undesirable condition in which a directional antenna loses power due to dispersion of the signals or wave patterns out of the “sides” of the antenna (e.g., portions that are not part of the main lobe). sideband The frequencies on either side of the main frequency or carrier band in a communications signal. These frequencies are within the modulation envelope of a transmission wave, but were originally not used because of problems with noise. Later, as technology improved and the demand for airspace continued to grow, sideband transmissions became more interesting, and it was found that one sideband could be transmitted, sometimes even without the

carrier wave, and the original wave mathematically “rebuilt” at the receiving end. The advantages included lower power requirements for the transmission and a narrower wave overall, leaving more room for other transmissions. sidetone In a telephone receiver, transmitting currents are directed into the receiver to make it possible for the speaker to hear his or her own voice (somewhat like an echo) as a form of feedback mechanism. This has to be carefully controlled so that it doesn’t become excessive, and various antisidetone circuits are applied to minimize feedback and reduce transmission of acoustical noise. In early telephones, the sidetone was loud enough to be distracting. In 1920, G.A. Campbell designed a circuit to reduce the excess current from the line and the local receiver, thus reducing sidetone and improving electrical efficiency. Sidetones are also used in telegraph keying systems as well, to provide feedback to the person keying in the (Morse) code. Sieve A protocol- and OS-independent, extensible mail filtering language proposed as a Standards Track RFC by T. Showalter, in Jan. 2001. Sieve is a language for filtering email messages at time of final delivery that can be implemented on either the mail server or a mail client. It is suitable for a variety of systems, including Internet Message Access Protocol (IMAP) servers. Sieve uses IMAIL-compliant messages to enable a user to create filters for organizing incoming electronic mail (email). The language is intended to be powerful enough to be useful, while not being so powerful that it can break out of its operating environment or wreak havoc on a system through uncontrolled variable, loops, or programming bugs. Sieve also facilitates the use of graphical user interfaces (GUIs) for creating and manipulating email filters. See FLAMES, RFC 3028. Simple Discovery Protocol SDP. An experimental minimal request/response multicast network recourse discovery protocol developed by Martin Hamilton. SDP payloads are application-dependent. SDP is not intended for bulk data transfers, due to the size of UDP packets. SLAR side-looking airborne radar. A self-illuminating (through microwaves) electronic image-creation system derived from a radar beam transmitted perpendicular to the ground track during acquisition from an aircraft. Thus, the signal hits the terrain at a rather flattened angle and the view of the terrain is vertical, revealing fine surface features useful in interpretation of the data. The imaging is provided in strips or mosaics, as is true for many satellite imaging systems. SLAR imagery is used by geologists, Earth resource scientists, cartographers, engineers, and others. SLAR encompasses real-aperture and synthetic-aperture radar (SAR). SLAR is not used for very precise topographic mapping, as the resolution is only up to about 30 m. Siemens Telecom Networks A provider of telecommunications services and network equipment emphasizing robust, secure technologies to regional Bell

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operating companies and independent telephone and holding companies. In March 2001, Siemens AG announced that it was cleared by the Federal Trade Commission to merge with Efficient Networks, Inc. (Texas-based suppliers of high-speed DSL networks). In December 2001, together with Cingular Wireless, the second largest mobile carrier in the U.S., Siemens announced that the two companies would be working to upgrade their services/systems to support 3G (third generation) mobile communications using Enhanced Data Rates for Global Evolution (EDGE) technology. Siemens, Werner (1816-1892) An American inventor who, along with his brother, William, developed the dynamo, a device to convert mechanical energy into electrical energy without the use of permanent magnets. In the 1870s, he demonstrated that the velocity of electrical conductivity through a wire could approximately equal that of light. SIF See SONET Interoperability Forum. sign in, sign on See login. sign language Any system of gestures or movements that conveys information. In its broadest sense, sign language includes handheld semaphore systems and, in its most specific sense, includes a number of standardized systems for using arms, hands, and facial expressions to convey meaning. Sign language in the form of hand and arm or flag semaphores is still standard in airports where noise and distance prevent spoken communications with ground personnel. See American Sign Language, semaphore. Signal Corps Radio Laboratories SCRL. A facility established at Fort Monmouth in March 1918 as Camp Alfred Vail. The lab was active in classified research including the development of radio direction finding equipment and aviation radio communications. Following World War I, aviation communication research was moved to the Signal Corps Aircraft Radio Laboratory in Ohio. A few years later, a number of labs in Washington, D.C. and New York state were moved to the Fort Monmouth location and it was redesignated as the Signal Corps Laboratories. The lab was used for radio communications development and adjunct meteorological services. In the early 1930s, marine and aerial sensing were added and radar studies stepped up in the late 1930s. Signal Transfer Point STP. A non-terminal node point which provides access to a database and packet switching for message-based signaling protocols for the Service Control Point (SCP) in an Intelligent Network (IN). STPs are widely used in Common Channel Signaling systems. To provide redundancy in a telephone network, Service Control Points (SCPs) and STPs are usually paired up. Depending on the implementation, the STPs may be arranged hierarchically, with the lower layer serving the smaller or local region and the higher layer serving the larger region. The Intelligent Network is based around Signaling System 7. See Intelligent Network, Service Switching Point. signal-to-noise S/N. A ratio frequently used in electronics and communications to quantify the

proportion of a signal (or communication) that is desired and useful to the proportion of a signal that is undesired and distracting or destructive to the desired signal. It is preferable to have a high signal-to-noise ratio. In electronics the signal can be an electrical or optical signal or a data stream and the noise can be various types of interference such as crosstalk, echo, spurious signals, etc. When Internet Relay Chat (IRC) was first developed, it had a pretty good signal-to-noise ratio in terms of the content of conversations. As the Net has grown, this has changed to the point that public online discussions are often avoided in deference to private chats and moderated email discussions. See noise. Signaling System 1 SS1. Historically, an international CCITT-standardized supervision single-tone signaling protocol to signal call requests between telephone switchboards. A 500-Hz signal tone at 20 Hz was used. Bell had a similar standard for manual ringdown signaling. These days Signaling System 1 is more often associated with newer digital signaling systems, i.e., DSS1. See Digital Subscriber Signaling 1. Signaling System 2 SS2. Historically, a CCITT-standardized supervision dual-tone signaling protocol to handle pulse-dial selection. Dual 600/750 Hz signal tones were used. It was somewhat similar to historic Bell radiotelephone dial signaling systems. Signaling System 3 SS3. Historically, a CCITT-standardized supervision single-tone signaling protocol used in one-way telephone circuits and not intended for use for multinational transit connections. This system was still in use until about the late 1970s. Signaling System 4 SS4. Historically, an international CCITT-standardized supervision dual-tone signaling protocol for international and terminal transit. SS4 was the first to fully support global direct dialing signaling. SS4 is not entirely obsolete; it is sometimes used for signaling for Voice over Packet (VoP) devices. Signaling System 5 SS5. Historically, an international CCITT-standardized supervision dual-tone signaling protocol used in T1 and E1 telephone trunks. Dual 2400/2600 Hz tones were used. SS5 is similar to Bell DDD trunks with supervision used in North America. SS5 is not entirely obsolete. Although it has generally been superseded by SS6 and SS7 for subscriber systems, testing and maintenance devices for central office equipment sometimes use SS5 signaling on digital trunk interfaces for testing gateways and SS5 is still used on analog international gateways. Signaling System 6 SS6. Historically, a CCITT outof-band signaling system developed in the 1960s, which is being superseded by Signaling System 7 in North America but is still popular in Europe. Both SS6 and SS7 owe their origins to Common Channel Interoffice Signaling (CCIS). SS6 was the first system to incorporate packet switching into public switched telephone networks (PSTNs). It supports a message-based protocol for requesting services, similar to the widespread X.25 standard. Signal units

of 28 bits each were assembled into data blocks for transmission. See Signaling System 7. Signaling System 7, Signaling System No. 7 SS7. SS7 is a common channel network signaling system, descended from Signaling System 6 and its precursor Common Channel Interoffice Signaling (CCIS). CCIS was an out-of-band that was inherently more secure than in-band multifrequency signaling systems prevalent at the time. It is sometimes referred to as Common Channel Signaling System 7 (CCS7). SS7, introduced in the 1980s, is more flexible and powerful than earlier versions, making it possible to implement broadband digital services far in advance of basic voice circuits. One of the ways in which SS7 differs from SS6 is that it supports variable-length signal units (up to a defined maximum), while SS6 was constrained to fixed-length units. Unlike earlier phone signaling systems, which operated through many semi-independent switching centers, SS7 brings the communications channels into a more integrated whole. The international data rate for SS7 networks is 64 kbps, although faster data rates are being studied and implemented, such as 1.544 and 2.048 Mbps (international). There are many factors influencing the adoption of SS7, including its flexibility and applicability to both wireline and wireless communications. But one of the first motivations for switching to SS7 was the development of phone services that could be dialed using a common area code, regardless of the geographical location of the subscriber (e.g., 800 numbers). Since local databases and switches could not be used to route calls that could be placed to any region, a central cross-reference registry was needed to associate the 800 number with a regional location and switching office. With SS7’s message-passing capabilities, it became straightforward to associate a virtual area code with a geographical routing code. This opened the door to other types of virtual area code services, such as emergency 911, pay 900, as well as custom calling services (e.g., Caller ID) and enhanced services (e.g., number portability). SS7 is now an important aspect of digital telecommunications services. Users have come to expect the many features that were difficult or impossible to implement over older analog tone-based signaling systems. With its out-of-band architecture, it is also inherently much more secure than historic in-band signaling systems. SS7 is being gradually integrated into ATM/T1 and PCS/UPT networks. See Common Channel Interoffice Signaling. Signaling System 7 ANSI standards There are a number of important American National Standards (ANSI) of Committee T1 related to SS7, that are available from ANSI and described in the form of abstracts on the Web. Signaling System R1 SS R1. An international analog telephony signaling standard, equivalent to Bell’s out-of-band 2600 Hz tone in DDD trunks in North America.

Signaling System R2 SS R2. An international analog telephony signaling standard, equivalent to Bell’s out-of-band 3825 Hz tone inserted between voice channels in the carrier system. signature 1. An identifying mark, usually a name, intended to relate a document or other transactional device to the individual associated with the document. A signature is often used as a means to acknowledge understanding or agreement to the terms of a transaction, e.g., a contract. See digital signature. 2. In a more general sense, a mark, style, method of doing things, or musical sequence that is identifiable as coming from a specific source or strongly associated with a certain person or group. The signing of a name in a person’s handwriting, the creation of a painting with a distinctive and uniquely recognizable origin, or even a specific way of turning a phrase are all examples of signatures in the broader sense. On the Internet, individuals often come up with names, signature files, or icons to uniquely and quickly identify themselves to others in much the same way a corporation identifies itself with a trademark or logo. 2. In printing, a grouping of pages that is created in order to organize the pages for binding. Common sizes for signature groups are 8 or 16 pages. With many people now doing their own desktop publishing and submitting them to printers over the Internet for publication, it helps to understand some of the basic terms and procedures used to create documents in the printing industry. See fascicle, imposition. signature file In computer communications, a common means for communicants to provide some background information on their interests or affiliations. Thus, business owners often include the name of their businesses in their email communications, students often have a signature file (.sig) on their student computer accounts that lists interests and sometimes courses. Professors often list their office hours in a signature file. Geek code was developed as a tongue-in-cheek shorthand homage to the signature file to pack a lot of information into a small amount of space. In general, in email and on public discussion groups such as USENET, it is considered courteous to keep signatures to three lines or less. See digital signature, geek code, signature. SIIA See Software & Information Industry Association. silence compression A technique used in voice over data network applications which involves removing the pauses and spaces that typically occur in many conversations. This reduces transmission time. Two common techniques typically used together include voice activity detection (VAD), which distinguishes speech from the surrounding background noise, and comfort noise generation (CNG), which creates a low type of static that gives humans a certain comfort level and trust that the line is still active and the call hasn’t been cut off. silent discard In packet networking, the discard of a packet without further processing. The system may log the event and may even store the contents of the discarded packet for later evaluation.

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silicon An abundant nonmetallic, tetravalent element, widely used in semiconductor technology. Silica, silicon dioxide, occurs in many common forms, including sand, quartz, and opals. Silicon Bay The city of Bellingham, a port town an hour and a half north of the Silicon Forest (Redmond/ Seattle), has a number of independent software development corporations, many supporting the computer graphics and CAD markets. Silicon Bayou The region of high-technology companies in and around New Orleans. silicon detector An early type of radio wave detector similar in some aspects to electrolytic detectors. Silicon is used in place of the electrolyte, making contact with a platinum wire, and the thumbscrew contact with the silicon can be finely adjusted by filing the end of the thumbscrew to a fine point, using a spring with the thumbscrew to assure even pressure. The interaction of the thumbscrew and the silicon sets up a thermoelectric reaction which can be translated into audible waves in the receiver. See detector, electrolytic detector. Silicon Forest The Microsoft campus and surrounding high-technology region in the Redmond/Seattle area has been dubbed the Silicon Forest due to the surrounding stands of trees which include douglas fir, cedar, Sitka spruce, and western hemlock. Silicon Graphics Incorporated SGI. A computer company known for innovative software and hardware workstation-level computers, especially those with good graphics and sound. SGI was founded in 1981 by James Clark, who later became affiliated with Netscape Communications Corporation. Silicon Valley A region of California with a high density of high-technology companies, many of which pioneered computer technology. The economy, educational institutions, research labs, and climate were all factors that contributed to the growth of technology companies in Silicon Valley. silicone rubber insulator A more recent type of insulator for installing conducting lines found on utility poles. The top and bottom mounting surfaces are metal, while the layers of “skirts” down the body of the insulator are fabricated out of silicone rubber over a fibre-glass core. Silicone rubber is nonconductive, light, water-repellant, resistant to ozone and ultraviolet degradation, and easy to fabricate in a variety of shapes and sizes, making it an alternative for glass and ceramic insulators. SIM4 Historically one of the early desktop computers, introduced over 2 years before the Altair, but several months after the Kenbak-1, in 1972, by the Intel Corporation, which was around the same time Hewlett Packard introduced the HP 9830. The single-board Intel computer was based upon a 4004 processor and was available in at least two models, the SIM4-01 and the SIM4-02. The SIM4-02 could be inserted into an Intel MCB4 chassis and programmed through a programmer card. See Altair, Kenbak-1, Micral. SIMM single inline memory module. Simon A historically remarkable computer project

described in Edmund C. Berkeley’s book Giant Brains or Machines that Think in 1949 and in Radio Electronics articles in the early 1950s. The name was based on Simple Simon. It was basically a desktop logic calculator that could be built for about $300 (about $4000 in today’s money). In his book, Berkeley describes it as “... so simple and so small, in fact, that it could be built to fill up less space than a grocery store box, about 4 cubic feet.” The Simon was an electromechanical assembly for performing different calculating experiments, but it can probably be considered the first desktop computing kit considering the size of computer behemoths at the time. Simon was a papertape computer based on 129 relays and a stepping switch. In Berkeley’s description, a two-hole tape reader was used to input numbers and operations and a four-hole tape reader was used to input instructions, but Berkeley points out that relays and other input modes apply just as well. Problems were entered in binary and answers were displayed on front panel lights (a design aspect used by many early microcomputers until the mid-1970s). The Simon isn’t listed here as the first personal computer because the Kenbak-1, for example, was a desktop-sized digital computer available fully assembled for $750 in 1971 (also equal to about $4000) that seems to better fulfill that role. But the influence of the Simon is not to be underrated, even if it was not generally known outside the electronics and engineering hobbyist industries. With assistance from William A. Porter, Robert A. Jensen, and Andrew Vall, Berkeley got a basic machine working. Considering that most people didn’t know what a computer was in those days, it is amazing that Berkeley wrote about “machines that think” in November 1949 and published plans for actually building the Simon in 1950. Apparently more than 400 plans for the Simon were sold over the next decade. Simon’s little-cousin successor was the GENIAC, a computing “game machine” developed by Berkeley in the mid-1950s with documentation by his partner Oliver Garfield (until a dispute split the name from the technology). See Altair; Arkay CT-650; Berkeley, Edmund C.; GENIAC; Kenbak-1; Simplac. Simplac A design for a transistor-based computer presented as a collaborative progress report documented by Edmund C. Berkeley through Berkeley Enterprises Laboratory in 1956. Milt Stoller had responsibility for the logical design of the machine. The machine was intended to have registers for three binary digits. The author is not sure whether this computer ever came to fruition. Berkeley had a lot of interests in robotics and artificial intelligence and was always beginning new projects. See Simon, GENIAC. Simple File Transfer Protocol SFTP. A simple file transfer protocol that fills the need for a specification that is easier to implement than File Transfer Protocol (FTP). It provides file transfer capabilities combined with user access control, listing of directories, traversing directories, file renaming, and file deleting. In other words, it incorporates the most

common and necessary functions of FTP. See RFC 913. Simple Gateway Monitoring Protocol SGMP. Developed in the mid-1980s and demonstrated in 1987, SGMP later evolved into Simple Network Management Protocol (SNMP). Simple Internet Transition SIT. A set of Internet protocol mechanisms for hosts and routers designed to smooth the transition between IPv4 and IPv6, its successor. SIT eases the transition by supporting incremental upgrades of hosts through upgrading the DNS server with support of existing addresses. SIT employs a number of mechanisms to achieve interoperability and compatibility including: • embedding of IPv4 addresses within IPv6 addresses • encapsulation of IPv6 packets in IPv4 headers for transmission through IPv4 legacy routers • dual IPv4/IPv6 protocol stacks model for hosts and routers • header translation for IPv6 only routing topologies simple line code SLC. A means of transmission through four-level baseband signaling that filters the baseband and restores it at the receiving end. Simple Mail Transfer Protocol SMTP. A transmission subsystem-independent electronic mail protocol which establishes and negotiates communications between sender and receiver (or multiple receivers) across transport service environments. Transmissions may be direct, depending upon the transport service, or may pass through relay servers. When a user mail request is generated, the senderSMTP establishes a two-way transmission channel to the intermediate or ultimate destination-SMTP. SMTP commands are then sent between the two ends. Once a transmission channel is established, a lock-step negotiation of the transmission and identification of the recipient or recipients is carried out, and the mail data sent, with a terminating sequence to indicate the end. When successfully received, the recipient sends an OK reply. See electronic mail, email, RFC 821. Simple Multicast Routing Protocol SMRP. A routing protocol from Apple Computing, Inc. which is used for AppleTalk network data from applications such as their QuickTime Conference, which in turn is used for videoconferencing, electronic whiteboarding, etc. Simple Network Management Protocol SNMP. SNMP evolved from, but is not backwardly compatible with, the Simple Gateway Monitoring Protocol (SGMP). Essentially, SNMP communicates management information between network management stations and the agents in the network elements (NEs). SNMP was designed for TCP/IP-based network environments and manages nodes on the Internet. SNMP was originally designed as an interim solution with the intention that it follow generally along Open Systems Interconnection (OSI) guidelines.

Over time, they were found more different than originally envisioned. Along with MIB and SMI, SNMP has been designated by the IAM as a full Standard Protocol with “recommended” status. The SNMP Extensions working group was formed to evaluate and further develop the SNMP definition, with the mandate of retaining its simplicity. See RFC 1157. Simple Raster Graphics Package SRGP. A lowlevel graphics package which incorporates features from a variety of graphics systems (such as GKS and PHIGS standards, The X Window System, Apple QuickDraw). SGRP typically functions as an intermediate layer between the applications program and the display device. Simple Security and Authentication Layer A Network Working Group-proposed standard for providing a quick method of negotiating an authentication mechanism, even if the client has minimal knowledge of the system. See RFC 2222. Simple Server Redundancy Protocol SSRP. A network protocol which provides resiliency for LANE services on ATM-based local area networks (LANs). SIMULA object-oriented programming language designed by O. Dahl and K. Hygaard at the Norwegian Computing Centre between 1962 and 1967. It was intended for discrete event simulation, but gradually became a general-purpose programming language. SIMULA was one of the early languages incorporating object-oriented concepts. A number of versions of SIMULA have been developed over the years, with compilers for specific systems such as Control Data Corporation systems as well as IBM 360/370 and UNIVAC computers. The Association of SIMULA Users (ASU), formally established in 1973, supports the development and use of the language and is one of the earlier computer users groups. simultaneous voice/data SVD. A number of analog and digital techniques and standards which permit limited use of simultaneous voice and data through regular phone lines with computer voice/ data modems. These might be considered medium level applications, since they do not support full realtime videoconferencing, but they allow whiteboarding and switching between voice and data as needed (alternate voice/data [AVD]). SVD is accomplished through multiplexing. In analog SVD, voice is multiplexed with data in digital SVD; data and digitally compressed voice are multiplexed into a digital data stream. The ITU-T has established standards, draft standards, and specifications related to SVD. These are periodically reviewed and updated to reflect improvements in modem technology. V.61 has been specified for 14,400 bps standard for analog SVD, and V.70 for 28,800/33,600 bps for digital SVD. simulator A software program, or software/hardware combination that models, reconstructs, or mimics an environment or situation, which may be real or imagined. Simulators are used in many areas of scientific research to enact scenarios; to test, confirm, or investigate hypotheses; to compare or contrast the

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effects of various changes to a system; or to monitor the evolution of a system. Simulators are also popular in the entertainment industry. Flight simulators have been developed into interactive, environmental video games with helmets, moving seats, and more, to provide a strong emotional/intellectual/tactile experience. Virtual reality simulators go a step farther, creating 3D effects which appear to inhabit the space around the user, sometimes so convincingly that the user will duck to get out of the way of a virtual image. Sinclair ZX81 The successor to the ZX80, the ZX81 personal computer was introduced in spring 1982 and sold for under $200 (without monitor; it could be hooked up to a television set). It sported 8 kbytes of extended BASIC, math functions to 8 decimal places, a built-in printer interface, 1 kbyte of memory expandable to 16 kbytes, and a 32-column x 24-line display. It was also available as a kit for under $100. sine wave A fundamental waveform present in almost all vibratory motion, which can be represented as a sine curve with periodic oscillations in which the amplitude of displacement at each point in the wave is proportional to the sine of the phase angle of its displacement. In telecommunications, the sine wave is important in many representations, but especially in alternating current (AC) circuitry and in representing sound. See oscilloscope. sine galvanometer An early current-detecting instrument in which the coil is rotated until the reading needle again registers zero. This type is subject to interference from the Earth’s magnetic field. See galvanometer. SINGARS Single Channel Ground and Airborne Radio Systems. A tactical radio system. See Enhanced Trivial FTP. single line repeater A mechanism for allowing twoway communication on a single line by permitting the transmission to be alternately broken in one direction in order to initiate or resume communication in the other direction. This is accomplished by an additional holding coil on each relay which can open or close independent of whether the main circuit is open. See half-duplex. single mode optical fiber A single mode fiber optic transmissions cable has a relatively thin core acting as a waveguide such that light is reflected and propagated at a consistent angle. A thinner core has advantages and disadvantages over multimode fiber. Signals cannot be sent at a variety of angles, but distortion is minimized and transmissions can occur over longer cable runs. Thus, where multimode fiber in data network installations is limited to about 2 km, single-mode fiber can transmit to about 15 km. For other types of transmissions, longer distances are possible, sometimes up to 200 km. Signals are usually transmitted through single-mode cables with laser diodes, in order to get the precise alignment needed for the fine filaments, and received at the other end with a photodiode detector. This detector translates the signals back into electrical impulses. See multimode optical fiber.

single sideband Transmissions created by manipulating frequencies that are selected from one side of the modulation envelope of a transmission wave to recreate the original baseband transmission. Much of the credit for the development of single sideband technology, which is essential to frequency division multiplexing, belongs to John R. Carson, a mathematician with AT&T, and later Bell Laboratories, who mathematically demonstrated the relationship between the information in the sideband signals and the original baseband. Sideband frequencies were not originally used because of problems with noise. Later, as technology improved and the demand for airspace grew, sideband transmissions became more interesting, and Carson demonstrated in 1915 that one sideband could be suppressed from the transmission and the other could even be transmitted without the carrier wave. Due to its predictable characteristics, the original baseband wave could then be mathematically rebuilt at the receiving end. In a sense, this was a type of “wave compression” accomplished by removing extraneous and redundant information. The significant advantages included lower power requirements for the transmission and a narrower wave overall (i.e., requiring less bandwidth), leaving more room for other transmissions. See frequency division multiplexing. single sign-on SSO. A network security and management strategy to help reduce the number of passwords needed to access a variety of software and hardware resources on a network. single slot Architecture for coin-operated devices that uses one slot for the various denominations of acceptable coins. Thus, the coins are processed by the mechanism after they are inserted by the user, rather than the user selecting an appropriate slot. These are becoming more prevalent and are now common in coin-operated phone installations. Single UNIX Specification Developed within the Common Applications Environment by the X/Open Company, the Single UNIX Specification is a collection of documents which includes interface definitions, interfaces, headers, commands, utilities, networking services, and X/Open Curses. This specification is distinct from the AT&T licensed sourcecode commercial product and is intended as a single stable UNIX specification for which portable applications can be built. It provides vendors a means to provide a “branded” product and assumes voluntary conformation to the specification. Basic components within the Specification are shown in the Single UNIX Specification chart. See Unix, UNIX. single use batteries Batteries which are not intended to be recharged after the power is drained, such as common alkaline batteries. There are, in fact, rechargers in the $20 to $30 range that can safely recharge these “nonrechargeable” batteries up to about six or eight times. It saves money and is easier on the environment as there are toxic substances in batteries, especially the older ones. Batteries should be recycled rather than thrown in the trash to reduce environmental contamination.

single wire circuit A transmission path used in early telegraph lines and still used for telephone service in some rural areas. The single wire circuit relied on the conductive characteristics of the Earth to ground the circuit and complete the return path. single-frequency signaling, SF signaling A telephony signaling system in which transmission is through a single designated frequency such as 2600 Hz in the U.S. and 2280 Hz in the U.K. SF signaling tends to be used in certain microwave transmissions and in two- or four-line wired networks. SF signaling is an in-band signaling scheme in that the signaling is transmitted in the same band or channel as the data or voice communications. When a phone system is on-hook, the designated signaling frequency is transmitted; when it is off-hook, the frequency is interrupted. Variations in signals can be produced within a single frequency by varying the level of the tones (as expressed in decibels - dB). In the U.S., a high level of -8 dB and a low level of -20 dB are standard as these are levels that can be readily recognized by the electronics in a phone receiver. sink 1. A device to drain energy from a system. Heat sinks are common on devices or components which run hot and need to be cooled for safety and to maintain operating temperatures. 2. A point where energy from a number of sources is directed, and then drained away. 3. A point in a communications system where information is directed. Sioussat, Helen J. Sioussat was the Director of the Talks and Public Affairs Department of CBS radio from 1937 to 1958. Her extensive correspondence with many of the radio and television broadcast pioneers has been preserved in the Library of American Broadcasting at the University of Maryland Libraries. See Broadcast Pioneers Library. SIPP Simple Internet Protocol Plus. One of three

candidate protocol proposals eventually blended into IPv6 by the Internet Engineering Task Force (IETF). SIR See substrate-incident recording. SIS Standardiseringen i Sverige. The Swedish standards institute located in Stockholm. SIT See Simple Internet Transition. SITA See Société Internationale de Télé–communications Aéronautiques. site license A legal arrangement granting specific use or distribution permission of a copyright product to a specified location, firm, or other entity. A site license is a common method for specifying and controlling software use and distribution within a firm, particularly if the firm wishes to install the software on a network for access by multiple users or on several user machines within the organization. Typically, software companies will offer site licenses with the first copy and installation of the product priced at one level, and discount subsequent installations. This is common in educational institutions. For example, the first copy might cost $1000 and permit installation on up to five machines, with subsequent installations, in groups of five, at $200 each. Network licenses typically specify how many users may simultaneously access the software, and the software itself may monitor and control access. Distribution of any sort, other than as specified by the license, in most cases is a criminal offense. See piracy. SKAM An acronym used in reliabiliy and risk management circles for skills, knowledge, access, and motive that describes the elements usually present when individuals or groups seek to compromise private and public networks and computer systems for malicious or unauthorized purposes. See Network Reliability and Interoperability Council. skew n. 1. In computer imaging, a function which allows a selected area to be stretched through one

Single UNIX Specification – Components Components

Notes

XPG4 System Calls and Libraries

Internationalized, covering POSIX.1 and POSIX.2 callable interfaces, the ISO C library and Multibyte Support Extension addendum, the Single UNIX Specification extension including STREAMS, the Shared Memory calls, application internationalization interfaces, and other application interfaces.

XPG4 Commands and Utilities V2

Covering the POSIX.2 Shell and Utilities and a large number of additional commands and development utilities.

XPG4 Internationalized Terminal Interfaces

Including the new extensions to support color and multibyte characters.

XPG4 C Language XPG4 Sockets XPG4 Transport Interfaces (XTI)

See sockets.

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plane at an angle, e.g., a square skewed to form a diamond. 2. In statistics, the distortion from an expected or true value. 3. In parallel data transmissions, the deviation in arrival of data from each individual transmission path. skin 1. Outer protective layer. A skin is often used to isolate conductive materials and/or to provide insulation and, sometimes, identification through the use of colored or marked skins. skin antenna An antenna used on aircraft, in which a region of the metal craft is delineated and isolated on its edges by insulating materials. skin effect In electricity, a situation in which the current tends to pass through the outer portions, rather than through the core of a conductor. This is due to the magnetic field that arises in the wire which prevents penetration to the core of the wire. It may increase the effective resistance in long wires and interfere with transmissions in the high frequencies used in broadcast transmissions. skinning Stripping an outer protective layer. This is commonly done with wires to expose the conductive material within in order to make a connection. skip distance The distance traveled by a reflected radio wave from the transmitter to the point at which it reaches the Earth’s surface or the receiving antenna. This distance is affected by the frequency of the wave, the angle at which it passes into the ionosphere, and various atmospheric characteristics and conditions. See ionospheric wave, radio. skip selection In computer software applications, a selection that halts the current process, or lets it finish in the background, and allows the user to continue to the next menu or activity without waiting. In automated voice or tone systems, especially menudriven touchtone phones, a key press that allows continuing to the next selection, menu, or local phone number without waiting for completion of the current message. skip zone See zone of silence. SKIPJACK The name of a symmetric encryption algorithm which is the basis of the Escrowed Encryption Standard (EES) incorporated into the Clipper chip. SKIPJACK can be used to encrypt a TELNET stream. It has also been described for use in conjunction with FTP Security Extensions and Key Exchange Algorithm (KEA) to provide for mutual authentication and the establishment of data encryption keys. See Clipper chip, RFC 2773, RFC 2951. skunkworks colloq. A facility in which clandestine or time-pressured activities take place in an environment which is closed off to increase security. Government operations, sensitive research, and hightechnology design often operate in environments that are without sunlight or adequate ventilation, and in which the participants are working long hours (without much free time for personal hygiene). One of the most famous skunkworks was a Lockheed-Martin research “lab” established by Clarence “Kelly” Johnson in a small desert facility scraped together from salvaged materials. It was a tight, intense, jet aircraft research and engineering operation dubbed the Skonk Works after an Al Capp cartoon

moonshine operation, while its official name became the Advanced Development Projects (ADP) division. Later the name was changed to The Skunk Works and the lab was moved to a location northeast of Los Angeles, California. The term is more than an amusing historical name; it is also at the heart of some of the significant disputes about domain names on the Internet. Lockheed owns the service mark for The Skunk Works and initiated lawsuits in the mid-1990s against Network Solutions, Inc. for registering variations of the name on the behalf of parties other than Lockheed. It was decided at the time that a domain registrar supplies a service rather than a product and that NSI was thus not liable for contributory infringement against the mark. sky maps Charts of the electromagnetic radiation in the radio frequencies emanating through space and around Earth. Much pioneer work in this area was conducted in the 1930s and 1940s by Grote Reber, an amateur radio operator, using a home-built 32-foot parabolic antenna. Cosmic frequencies can sometimes be detected when the ionosphere is temporarily affected by the burn of a spacecraft or deliberate seeding with elements such as barium. The phrase is also generically used to describe images of the sky as humans see it looking up from Earth with or without telescopes. Some interesting utilities on the Web now enable users to enter a location and date/time to calculate and display a sky map that can be printed or downloaded. John Walker provides access to “Your Sky” free on his Fourmilab site. See radio astronomy. http://www.fourmilab.to/ sky wave See ionospheric wave. SkyBridge A medium Earth orbit (MEO) satellite system from Alcatel providing commercial satellitebased networking solutions to service providers. SkyBridge was established in 1997. In March 2001, SkyBridge announced that it would also be implementing broadband communications services through geostationary satellites. SkyCell Communications Limited An Indian cellular services provider incorporated in 1992. It is the first Indian cellular company to receive companywide ISO 9001 certification. SKYCELL An American Mobile Satellite Corporation (AMSC) satellite telephony communications service providing coverage for the North American continent and nearby islands, catering to mobile workforces, traveling executives, and government agencies. The company also offers a continent-wide regional dispatch service providing digital broadcast capabilities to up to 10,000 mobile users. Skynet A U.S. domestic communications satellite service purchased in 1997 from AT&T by LORAL Space & Communications, Ltd. Skynet originated in the Echo satellite and Project Telstar efforts in the 1960s. Telstar 5 was launched 2 months after LORAL’s acquisition and positioned at 97° west. Soon after, Satmex was merged into the firm, forming the LORAL Global Alliance. Orion Network Systems, Inc. was acquired in spring 1998. Telstar 6 was

launched in March 1999 at 93° west; Telstar 7 was launched in September 1999 at 129° west. It has been called the most powerful communications satellite in Telstar history and has been joined by further satellites later named Telstar 10 and 12. Skynet provides news, television broadcasting, distance learning, videoconferencing, and other data transmission services to about 85% of the populated regions of the world. SL Symbol for left-hand slant polarization (ITU). SL Mail A commercial SMTP and POP3 mail server daemon for Windows NT 4.0 from Seattle Lab, Inc. slamming A reprehensible trade practice in which a long-distance supplier switches a person’s long-distance service without his or her explicit informed consent. In the early 1990s, some companies did this by phoning potential subscribers and having them verify their name and address over the phone and then signing them up without actually asking for consent. Since that time, more stringent customer consent is required before a change in the service can be initiated, and the customer usually must initiate the request, or the company making the change must obtain written authorization or outside verification. SLAR See side-looking airborne radar. slave 1. A subsidiary structure, system, process, or device which takes direction or data from a master. Many computer peripherals are slave devices. 2. In programming, slave processes are sometimes used to gather and report information to a master controlling process. 3. In communications circuits, slave consoles, subsidiary switching centers, and substations are often used to supply low-density populations or workstations some distance from the main controller or switching center. slave server In distributed networks using domain name systems, a slave is an authoritative server, identified in the name server’s register, which retrieves zones using zone transfer. See stealth server. SLC See simple line code. sleep mode, power save mode Since portable appliances typically run on batteries and batteries wear out and must be replaced or recharged, vendors have come up with ways to extend the time between replacement or recharge. One solution is to provide a manual or automatic sleep mode in which the appliance is put on a standby setting which uses less power until it is needed again. This is very common on laptop computers. Since screen displays, modems, and hard drives require more power, but may not be needed while the user is talking or waiting, the laptop will often power down into sleep mode until the user touches a key or moves the mouse. slide contact A small sliding ball or tab attached to a thin rod which acts as a contact mechanism on a tuning coil. Tuning coils were used in early radio sets to select a frequency. A radio might come with several tuning coils for selecting various frequencies, as desired. See tuning coil. SLIP See Serial Line Interface Protocol. SLM System Load Module. slot 1. In programming, a time or data “opening” into

which other processes or data can be inserted. 2. A physical opening for connectors or wires/cables which is typically narrow and rectangular. The slots on the back of a computer allow external connection access to peripheral cards such as serial, graphics, or network interface cards (NICs). See slot types. 3. In building structures, an opening that may be built into a wall or floor in order to enable cables to be fed through the building. slot types Most computers and switching stations have slots into which electronics peripheral cards can be inserted. In order for third-party suppliers to be able to develop options for consumers, a number of standards have been adopted for the shape and electrical configuration of these slots. Most of these slots are long, narrow-edge card configurations, with two to six slots in the typical desktop computer. Many computers will accommodate two different card formats. The software drivers for the cards inserted into these slots are sometimes supplied on diskettes, to be loaded on the system, and are sometimes supplied in hardware, on chips on the actual card. Some of the more common card slot types include PCI, ISA, ESA, ZORRO, and PCMCIA. Slotted ALOHA See ALOHA. slotting In setting up a network, the assignment of a circuit to available channel capacity. slow scan television, slow scan TV SSTV. A type of black and white TV signal which can function within a narrow spectrum, similar to single-sideband transmissions for voice. SSTV has been used since the late 1950s by amateur television and radio operators to send series of images over radio frequencies. SSTV can be viewed on a television set with a scan converter or on a computer monitor with the appropriate interface. In the U.S., SSTV uses frequencies ranging from about 3.845 to 145.5 MHz to transmit a series of images which can be captured through a dedicated system or through a computer linkup. Interface circuits for setting this up are in the hobbyist price range. Hicolor mode can provide color images up to 320 x 240 in thousands of colors. Even higher resolution 640 x 480 24-bit images (millions of colors) can be transmitted, but they take 7 or 8 minutes, compared to low-resolution black and white images that take only 7 or 8 seconds. Radio broadcasting is regulated throughout the world; those interested in SSTV technology will have to be licensed, usually for voice grade channels, by local regulatory authorities. A related technology is amateur TV (ATV) which refers to fast scan amateur television. See amateur television. SLP See Service Location Protocol. SLR 1. send loudness rating. 2. single lens reflex. Small Computer System Interface SCSI (pron. scuzzi). A standardized interface specification which provides a means for the central processing unit (CPU) and main circuitry on the motherboard to communicate with computer devices that are interfaced to the system. This requires standardization of

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electrical circuitry and data protocols because peripheral devices are manufactured by many different companies. One of the most common of these formats is SCSI, which is widely used to interconnect hard drives, scanners, cartridge drives, digitizers, CD-ROM drives, and more. The SCSI standard is approved by the American National Standards Institute (ANSI), and several enhanced versions have appeared (variously called SCSI-2, extended SCSI, SCSI-3, wide-SCSI, etc.) SCSI typically consists of a SCSI controller on a motherboard or a peripheral card, which is terminated and usually designated as zero or six, depending upon the system and one or more peripheral devices, set to SCSI ID number zero through five or one through six, depending upon which one is reserved for the motherboard, and terminated at the end of the last device. The devices can be hooked up endto-end, that is, daisy-chained. Each SCSI controller can chain up to seven devices, with the motherboard or main controller counting as one. The cable for SCSI devices is either a 50-pin edge connector or a 25-pin D connector (or a hybrid cable with an edge connector at one end and pin connector at the other). SCSI-3 cables are wider. Only one device can be assigned to each SCSI ID. Conflicts or lack of termination will cause failure to recognize a device or spurious errors. Many systems expect CD-ROM devices to be set to ID 3, although there is no inherent reason why ID 3 has to be assigned to only this type of device. Scanners often default to SCSI ID 4. The ID number will determine the priority setting for loading the device, thus boot disks are usually assigned a number closest to the number of the controller. In other words, if the controller on a motherboard is zero, then the boot hard drive should probably be set to one and a relatively low-use tape drive to five or six. SCSI ID settings are sometimes on the outside of the device, with a thumb-turn switch or DIP switch, and sometimes on the inside, with DIP switches or jumpers. Termination is accomplished either by placing a physical terminator in one of the cable connection slots, by setting DIP switches, or by setting jumpers inside the device. Automatic termination is available on some devices, which means that if the device senses that it is the last device in the chain, it will terminate automatically. These types of automatic terminators are sometimes specific to the slot. There will be two slots on the back of most SCSI devices so that they can be chained. Take care to follow instructions for which one to connect if the device is last in the chain and intended to terminate automatically. Most SCSI devices can only work with cables up to about 6 feet in length, and 3 feet or shorter is generally recommended. Newer Fibre Channel Standard technologies can support longer connection lengths, allowing SCSI devices to be centralized in an operations room or wiring closet. SCSI controllers are standard in many consumer and workstation computer systems, including Macintosh,

Amiga, server-level IBM-licensed desktop computers, NeXT, Sun, SGI, some HP systems, and DEC. Most of these systems include an internal SCSI controller (for up to six hard drives and internal CDROM drives, etc.) and an external SCSI controller (for up to six scanner, printer, external CD-ROM, external hard drive devices, etc.). Thus, a total of 12 devices can easily be daisy-chained to these systems without any modifications to the operating system or the hardware, other than perhaps adding a software device driver and cabling. In the author’s experience, SCSI is a good format. The inexpensive 8year-old Motorola 68040-based computer used for the illustrations for this dictionary has two SCSI connectors (internal and external) with eight SCSI/SCSI2 devices attached (scanner, tape drive, cartridge drive, six-disc CD-ROM drive, and four different kinds of hard drives). These are chained to the two controllers and worked together the first time they were connected without any compatibility problems. SCSI drives are incorporated in mirroring and redundancy combination working drive/backup systems such as redundant array of inexpensive disks (RAID) systems. These drives can be conveniently hotswapped in and out of the system if a drive fails and needs to be replaced, with the information rebuilt by the controller and software when the new drive is installed. For consumer desktop Intel-based, IBM-licensed computers that come standard with IDE drives, a SCSI controller card can be added to the system to accommodate SCSI devices. However, on this type of system, it is important to determine whether appropriate device drivers are available for the peripheral, that there is no contention with the IDE drive, and also that any appropriate IRQ issues are settled.

Two common varieties of SCSI hard disk drives showing the various connectors, components, and jumpers for setting the SCSI ID number.

Small Scale Experimental Machine Nicknamed “Baby,” this historic computer was developed in the mid-1940s, based upon tube memory, a form of randomly accessible data stored in a Williams-Kilburn cathode-ray tube. Baby was a binary small-endian system that supported 32-bit words and a main random access storage capability of 32 words, which could be extended to 8192 words. It used several tubes for different functions, including a storage

register that is still used in modern computers, the “accumulator,” a couple of instruction tubes, and a tube for displaying the contents of the other tubes. A simple keyboard was used to set the bit sequences. The project was undertaken by T. Kilburn and G. Tootill with equipment support from the Telecommunications Research Establishment (TRE). The system was initially used in 1948 for mathematical calculations that were laborious to execute by hand. See Williams-Kilburn tube, Manchester Mark I. small vocabulary In speech recognition, it has been found that software can be designed to recognize a variety of voices, without special training of the system, if the total vocabulary of the recognition is kept small. These small vocabulary systems work well in specific environments such as stock buy/sell systems. While definitions of small vary, recent systems of this type typically recognize 200 or fewer words. Smallhouse, Charles “Chuck” An amateur radio enthusiast who contributed substantially to the first three OSCAR satellites’ design and construction. See OSCAR. Smalltalk An object-oriented computer exploration and development language developed through the Xerox Corporation in the 1970s. It was evaluated by four Xerox-selected companies in 1980, before being broadly distributed. By the mid-1980s, commercial versions of Smalltalk-80 were being released for a variety of platforms including IBM licensed personal computers and Apple II systems. Smalltalk has been favored by developers working in object-oriented programming environments and artificial intelligence applications. See Palo Alto Research Center. SMAP See Service Management Access Point. SMART Self-Monitoring, Analysis, and Reporting Technology. A preventive system implemented in data protection schemes such as RAID which uses predictive failure analysis to anticipate possible failures. Impending problems are communicated to the controller, which signals a warning so that faulty drives may be examined or replaced prior to any failure which might occur. See redundant array of inexpensive disks. Smart Card A compact, thin card with embedded data. It may contain a microprocessor, memory, or both. It typically resembles a plastic credit card. Earlier Smart Cards incorporated a magnetic strip, but more recent cards may include a set of contacts embedded in the card. The essential concept of the Smart Card was patented in 1974 by K. Arimura in Japan and R. Moreno in Europe. In the 1980s and 1990s, Smart Cards came into common use for many types of financial transactions, mobile communications devices, long-distance phone services, and authorized entry systems. The common standard for Smart Cards is in the ISO 7816 series. A number of financial agencies have agreed upon a common specification for communications between Smart Cards and Smart Card readers, similar to the serial communication that occurs between computers and computer peripherals. This makes it possible to exchange virtually any type of data between readers and cards and increases the

possibility of programmable universal cards for the convenience of users. The downside of universal cards is that, if they are stolen, a great deal of information may be in the wrong hands. However, various encryption and other security measures are being developed to help protect Smart Card users against theft. There are various ways to categorize Smart Cards. Some require contact with a sensor and some are read without direct physical contact. A contact sensor can consist of a reader with a slot or a sensing surface upon which the card is placed. Slot sensors generally require that the card be swiped across the surface to register the information. Basically the card is being scanned for information. Contactless cards typically incorporate tiny wireless transmitters and may include an antenna to increase the transmission range of the signal. There are also hybrid cards. For example, a wireless transmitter may be included for opening entranceways at a worksite while a second contact surface may be used to transmit more detailed information about the person holding the card when it is swiped through a card reader. The cards can also be categorized on the basis of the types of data contained on the card (information or algorithms) and whether they are reprogrammable (write once, read many (WORM) or rewritable). Since a Smart Card is somewhat like a tiny floppy disk or a very tiny computer, the range of uses to which it can be applied is exceptionally broad. It could not only facilitate telephone access for travelers, but could potentially keep track of where and when the calls were made. This information is valuable for corporations logging sales transactions, for example, and keeping records for the taxation department. A Smart Card could also help present and track prescriptions, employee purchases, medical histories, allergy shots, pet vaccination histories, automobile histories, and much more. Smart Card application interfaces have been introduced by a number of developers and a lot of interest in programming Smart Cards with Sun’s Java language arose in the late 1990s. It is likely that Smart Cards will become a ubiquitous part of daily life, replacing many of the paper notepads and “dumb” cards now used by consumers and professionals. Smart Card Industry Association SCIA. A trade association supporting and promoting the development, utilization, and understanding of Smart Card technologies. http://www.scia.org/ SMASH Project A project dedicated to developing mass storage devices for multimedia applications for home use. This is intended to promote commercial offerings of video services to the home, with part of the goal of SMASH to provide a labeling algorithm system in the storage system to provide vendor copy protection. Thus, data on the storage device can be set so that it can only be stored or copied once. SMASH seeks to develop realtime labeling methods for compressed video. Common schemes for this include spatial or discrete cosine transform (DCT). The SMASH Project also introduces two new realtime labeling techniques that can be used in conjunction

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with MPEG-1 or MPEG-2 format video information. See watermark. SMAS Switched Maintenance Access System. A legacy network system from Anritsu Company. The older systems (e.g., cross bar access systems) are gradually being updated or phased out. SMATV Satellite Master Antenna Television. A satellite communications distribution system designed to send transmissions to hotels, motels, apartments, etc. Since these are sent mainly to commercial establishments, they are often used as marketing leaders or as pay-per-view revenue-generators. SMB See Server Message Block protocol. SMB Project A project for preserving the history of the Server Message Block (SMB) protocol while primary materials are still available. The first definition of NetBIOS was released by IBM in a Technical Reference in 1984. By the late 1980s, SMB File Sharing Protocol extensions were being published by Microsoft. http://samba.org/ SMDS See Switched Multi-Megabit Digital Service. SME 1. Security Management Entity. 2. Small- and medium-sized enterprises. smear 1. Descriptive term for a television signal display distortion in which the image is blurred and appears stretched in the horizontal direction. 2. Lowlevel frequency distortion in an audio signal. 3. In digital imagery, distortion of details resulting from sampling frequencies or compression algorithm compromises, so transitions which normally would be sharp and crisp in the original image exhibit blurring or smear. SMI See Structure of Management Information. S/MIME Secure Multipurpose Internet Mail Extension. An IETF working group (inherited from the S/ MIME Consortium) Internet messaging standard for the transmission of secure network communications. Unlike PGP/MIME, S/MIME public keys are distributed via X.509 digital certificates. S/MIME can support 128-bit encryption, although not all implementations will use the full 128 bits. See PGP/MIME. smoke signal An early form of distance communications signal code that involved burning materials that produced a quantity of thick smoke at a high vantage point, and controlling the smoke with a blanket used to alternately suppress and liberate the puffs of smoke. Extensively employed by native North American plains dwellers, and later adapted by some of the early white settlers during times of conflict. SMPTE See Society of Motion Picture and Television Engineers. SMPTE Registration Authority SMPTE RA. A format and specification authority for technologies related to the motion picture and television industries. For example, the SMPTE RA is approved by IEC and ISO for the registration of MPEG-related format identifiers. See Society of Motion Picture and Television Engineers. SMPTE time code A standard developed by the Society of Motion Picture and Television Engineers which provides synchronization for information recorded on audio and visual video tapes. SMPTE time

code digitally encodes hours, minutes, seconds, and frames. SMPTE time code is recorded onto audio tracks and video tracks as follows: in audio as Longitudinal time code (LTC); in video as Vertical interleave time code (VITC). A time code word consists of 80 bits (zero or one) per video frame, with 2400 bits per second corresponding to 30 frames per second for North American TV. In Europe, 2000 bits per second corresponds to the standard of 25 frames per second. See drop frame, Society of Motion Picture and Television Engineers. SMR See Specialized Mobile Radio. SMRP See Simple Multicast Routing Protocol. SMS 1. See Service Management System. 2. See Short Message Service. SMS/800 A centralized interactive computer system dedicated to coordinating network services related to toll-free 800/876/etc. numbers. These are managed in a central database-equipped mainframe computer from IBM that updates locally deployed databases. Access is through dialup, Internet, and dedicated connections with various security systems in place to restrict access to authorized users. The SMS/800 system supports a 24-hour-a-day, 7-day-a-week public service. Within the SMS/800 system, a Responsible Organization (Resp Org) is an entity authorized to manage and administer a toll-free number customer using the SMS/800 system. Bell Operating Companies (BOCs) administer the SMS/800 system under the 800 Service Management System Functions Tariff. The SMS/800 system tracks the availability of all toll-free numbers and permits Resp Orgs to access the database to search for available numbers and to change the status of existing numbers. The North American Numbering Plan (NANP) Administrator issues instructions to carriers for making toll-free numbers available or unavailable. Resp Orgs are assigned a logon ID code from a BOC and must meet certain certification requirements. Logon ID requests are processed by the SMS/800 Management Team in New Jersey. Numbers are obtained by Resp Orgs from a common pool, with specific 800 number requests honored based upon availability on a first-come, first-served basis at the time the request is received in the SMS/ 800 Reservation Queue. Specific numbers may be reserved for a potential subscriber for up to 45 calendar days. If the period expires, the number is designated a spare. A Resp Org may reserve up to 2000 numbers, or up to 7.5% of the total available numbers, whichever is greater. Certain numbers are reserved for special purposes (e.g., hearing impaired) and are considered Closed. Resp Orgs are limited to a maximum of up to 3% of available numbers that are reserved at any given time. Resp Orgs must be willing and able to provide troubleshooting assistance and maintenance personnel. There is a customer record administration charge for each toll-free number assigned or reserved.

Hoarding of toll-free numbers by Resp Orgs is expressly forbidden within the Federal Communications Commission (FCC) Tariff guidelines. Acquiring more numbers than are intended for immediate use by a subscriber, or the sale of a toll-free number for an additional fee, contravenes the FCC’s responsibility to promote the fair allocation and orderly use of toll-free numbers. The SMS/800 Software Support organization publishes the Service Management System (SMS)/800 Mechanized Generic Interface Specification (SR4592 - Feb. 2001). See 800. http://www.sms800.com SMS/800 history The SMS/800 system originated in 1967, when AT&T introduced an inward Wide Area Telecommunications Service (INWATS) for business subscribers who wanted to purchase bulk calling to enable customers to reach them from a wide geographic region. In 1981, computerization made it practical to introduce a centralized database for managing national services such as 800 numbers and to assign parameters to specific numbers. This, in turn, made it possible to make the service more flexible and powerful. At about the same time, smaller companies and competing phone carriers were computerizing their customer databases. When the Judge Greene divestiture proceedings led to the breakup of the Bell System in 1984, 800 services were required to be opened up to competitors. This necessitated the development of more sophisticated software to handle the management of databases from Bell Operating Companies (BOCs) and independent competing carriers. Number portability soon became an issue, with so many competing phone carriers now offering 800 services. In 1991, the Federal Communications Commission (FCC) mandated that 800 numbers must be able to be moved among carriers according to the carrier selection of the subscriber. By the mid-1990s, 800-number designations were running out, due to the increasing demand. As a result, additional prefixes were released, to be assigned as the need arose. See SMS/800. SMS/800 Management Team A team of administrators, consisting of a representative from each of the regional Bell Operating Companies (RBOCs), responsible for SMS/800 services. The team is headquartered in New Jersey. SMS/800 Mechanized Generic Interface MGI. A means to interface with the SMS/800 centralized tollfree number database. The MGI facilitates the transfer of number and customer record administration between the SMS/800 and Responsible Organization (Resp Org) computer system over a network connection. It is a two-way interface delivered over a fivelayer protocol model. The transport service is supported over the physical, packet, and link layers for error-free communication. The user program layer (UPL) supports specific applications messages. Before active status on the SMS/800 system is granted, the MGI must be put through four test phases to confirm data communications integrity per specific field and laboratory testing requirements. A testing logon ID is assigned for the test period of

about 4 months. Once access is authorized, an active login ID code is assigned. See SMS/800. SMTP See Simple Mail Transfer Protocol. SNA See Systems Network Architecture. SNA Control Protocol SNACP. A protocol which handles the configuration and enable/disable functions at the ends of a point-to-point link. Subdivided into two protocols that independently negotiate SNA with or without LLC 802.2. Similar to Link Control Protocol. See See RFC 2043. SNACP See SNA Control Protocol. SNAFU An acronym for “situation normal—all fouled up” originating in World War II, or perhaps earlier, this expression hasn’t lost its currency and is frequently heard in industries struggling to implement, use, and maintain constantly changing technology. snail mail slang A tongue-in-cheek reference to physical messages (letters) being delivered very slowly (at a snail’s pace) by the postal service, in contrast to electronic mail, which is often received within minutes of being sent. See email. snake A cabling aid consisting of a flexible, long, thin cord of metal or plastic used to feed wire and cable through conduit or through structures (ceilings, walls, attics, etc.) where space is tight, or access is limited. See birdie. SNAP See SubNetwork Access Protocol. snap-hook A loop-shaped connector with a normally closed hook that can be opened to add objects to the hook with the hook snapping closed automatically after insertion. Snap hooks may be locking or nonlocking. Rock climbers are familiar with a number of types of snap hooks and similar hooks are used by workers who climb utility poles or towers to do installations or maintenance/repair. Snap hooks are also handy for slinging wire bundles and hanging up equipment that needs to be securely held. Contrast with J hook. sneak currents Low-level undesired currents which seep into circuits and may, if continued long enough, cause damage. Sneak currents are those which do not cause immediate harm and are not sufficient to trigger safety mechanisms such as normal fuses and breakers. Sneak currents can result from causes such as worn sheaths and insulators, incorrect wiring, temporary contact due to settling, etc. See sneak fuse. sneak fuse A special low-level current detection fuse specifically designed to trigger if sneak currents are detected. See sneak currents. SNI See Subscriber Network Interface. sniffer 1. colloq. nose. 2. A synthetic or electronic substitute for a nose, such as a chemical testing kit used for drug detection and identification by the U.S. Customs service. 3. A utility for peeling or ferreting out information, such as particular statistics from a log file. 4. A network traffic monitoring tool used for diagnostics and sometimes unauthorized snooping. A sniffer is a useful system administration tool for monitoring and logging peak traffic times, network load, and possible problems. This information can help an administrator tune a system to operate

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efficiently. See packet sniffer, Sniffer. 5. A radio direction-finding tool for locating radio transmitters. See Ultra sniffer. 6. A detective or investigative journalist who sniffs out (investigates) information as desired by clients or editors. Sniffer A registered trademark of Network General Corporation. The term “sniffer” has been used for decades in the search and rescue and law enforcement communities to refer to working dogs that are trained to sniff out fugitives, lost individuals, or chemical substances. The term has also historically been used in the radio community to refer to receiving devices that locate the source of radio signals. These direction finders help to trace signals emanating from sources such as wildlife radio collars or radio listening devices (bugs). With the advent of computer sniffers, Network General Corporation has trademarked the term in the context of software utilities and network analyzers and the firm endeavors to protect this registered trademark. The author has included other generic and commercial uses of the term “sniffer” in this dictionary to help readers understand the different senses in which the word has been used historically and is now used in the telecommunications industry while, at the same time, calling attention to the property rights of Network General. See Sniffer Network Analyzer. Sniffer Network Analyzer A commercial product for analyzing local area network (LAN) traffic, first introduced in 1988 by Network General Corporation. The software provides a log of traffic, a suite of alarms, and various statistics. The corporation specializes in fault and performance management solutions for enterprise networks. Sniffer Technologies A commercial vendor of wireless monitors and network traffic analyzers and reporting products, including Sniffer Distributed, Sniffer Wireless, Sniffer Optical, and others. sniffing jargon In computer networks, the process of looking at network data for the purposes of testing or diagnosis or for unauthorized purposes. Because the Internet as a whole is a shared system, rather than a switched system (though switched portions exist), it is relatively easy to breach a system with software and hardware tools provided for network testing and administration. One type of scouting sniffer for clandestine use captures the first few hundred bytes of every remote session or file download/upload, so that the unauthorized snoop can scan the sessions for interesting information that might suggest a closer look. Sniffit A testing and maintenance tool for a variety of platforms that was distributed in a preview version at HIP ‘97 by B. Claerhout. Beta v. 0.3.7 was released online in 1998. SNMP See Simple Network Management Protocol. snoop A testing and maintenance software tool for Solaris that enables the user to capture and inspect each packet in packet-based network traffic. It uses both the network packet filter and streams buffer modules for packet capture and displays them as received or logs them to a file. It is similar to tcpdump and related to etherfind (SunOS). The snoop utility

can be used to tune network variables, to detect retransmissions, duplicate acknowledgments, and other aspects of the network configuration. snooper, snooperscope, night scope A device designed to enhance night vision by sending out and intercepting an infrared beam. The incoming beam is interpreted into an image that shows objects not visible to the human eye. snow An undesired aberration in a broadcast or display of a video image in which there are many randomly distributed speckles, often white. Snow can result from transmission problems, such as a weak or drifting signal, or from display device problems, as in a cathode-ray tube (CRT). SNVT (pron. snivit) See standard network variable type. Société Internationale de Télécommunications Aéronautiques SITA. An international airline reservations and telegraphic transmissions service backbone network established in 1983. Society for the History of Technology SHOT. An interdisciplinary organization dedicated to fostering and promoting an interest in the development of technology and how it affects society and culture, and to promoting scholarly study of related documents and artifacts. Members include individuals, professionals, museums, scientists, and librarians. The organization was formed in 1958 and is headquartered in the Department of History of Science, Medicine, and Technology at Johns Hopkins University. Society of Broadcast Engineers, Inc. SBE. A nonprofit organization providing publications, workshops, a certification program, and liaison with important regulatory agencies such as the Federal Communications Commission (FCC) in order to promote education, standards, and professional competency in the broadcast engineering industry. The SBE was founded in 1963 and has since grown to over 100 chapters in the U.S. and abroad. It publishes the quarterly journal The SBE SIGNAL. http://www.sbe.org/ Society of Cable Telecommunications Engineers Inc. SCTE. A U.S. national nonprofit professional organization founded in 1969. The society includes over 13,000 members from around the world, representing a broad spectrum of cable professionals. The society provides education, certification, and standards development. http://www.scte.org/ Society of Motion Picture and Television Engineers SMPTE. An international organization originally founded in 1916 as the Society of Motion Picture Engineers. The T was added in 1950 to encompass the emergence of the television industry. The society includes over 8500 members in 72 countries, including engineers, technical directors, and production/post-production professionals dedicated to advancing the theory and application of motion-picture technologies. SMPTE contributes to standards development, encourages consensus-based recommended practices (RPs), and industry engineering guidelines (EGs). In 1957, the society was awarded an Oscar for its contributions to the advancement of the motion picture industry. It has also received three Emmy awards

for various recording and video systems and standards. SMPTE is best known for developing SMPTE time code methods, which are used for video editing. When video tape began to be widely used for recording and editing, a way was needed to synchronize edits, to locate specific places on the tape, and to dub sound to match the video sequences. SMPTE began in 1969 to develop a standard for digitally encoding time information in terms of hours, minutes, seconds, and frames onto audio or video tape. See MIDI time code, SMPTE time code. http://www.smpte.org/ socket 1. A means of providing unique identification to which or from which information is transmitted on a network. RFC 147 specifies a socket as a 32-bit number; even sockets identify receiving sockets, odd sockets identify sending sockets. Each socket is identified with a process running at a known host. SOCKS An access and security technology designed to provide a framework for TCP and UDP client/ server applications to conveniently, transparently, and securely utilize and traverse a network firewall. There have been a number of versions of SOCKS, with RFC 1928 representing version 5. Version 5 adds UDP and authentication capabilities, and extends addressing to accommodate the future needs of IPv6. The protocol fits between the application layer and the transport layer and does not provide ICMP message-forwarding services. Traversing a firewall securely depends upon the various authentication and encapsulation methods selected and used in the negotiation between the SOCKS client and server. See firewall, gateway, proxy, RFC 1928. sodium vapor lamp A lamp that glows a warm golden color, from the passage of electricity through metallic vapors in a cylinder encased in a glass tube. Sodium vapor lamps have been used as street and bridge lamps. See mercury vapor lamp. soft copy A stored image, document, or file which is recorded on a medium which must be accessed with some type of technology in order to be viewed, manipulated, or displayed. Soft copies commonly exist on hard drives, floppy diskettes, tapes, CDs, and other magnetic or optical media. A hard copy is readable by looking directly at the medium on which it is transcribed, as on a piece of paper, cardboard, stone, or parchment. soft transfer A term for an electronic monetary transaction which precedes the actual exchange of funds between individuals or banking institutions. A paper check is a type of soft transfer. It is a monetary transaction which is not finalized until the money is withdrawn from the bank. Similarly, online, many monetary transactions which are soft transferred and later “hard transferred” from the actual bank or other financial institution, such as a credit union. SoftCard An early commercial product from Microsoft, from an idea suggested by cofounder Paul Allen. The SoftCard was an internal peripheral card equipped with a Z80 processor, which ran CP/M-80 from Digital Research. This card, when installed in an Apple II computer, allowed its user to install and

run CP/M-compatible applications programs. softlifting A term that became prevalent on the Internet and in trade magazines, when commercial Web browsers became widespread, although it had previously been mentioned somewhat in the context of other types of applications. Softlifting is a process of having a piece of software gather information that is stored on a person’s computer or gathering information about the computer configuration, and reporting that information back to the manufacturer. The reporting is usually without the knowledge of the user, and often happens when the user dials up to a public network or registers his or her software on the vendor’s bulletin board system. This is considered by the consumer and Internet communities as a reprehensible, blatantly unethical activity, and developers who attempt this covert information-gathering put themselves at risk of substantial criticism and possible legal reprisals. SoftSource Corporation/Catarra A Colorado- and Bellingham-based firm that has developed a nextgeneration wireless mobile Personal Digital Assistant (PDA) macrobrowser that works transparently with the World Wide Web. This product may define the future of mobile wireless Web browsing. Recognizing the improved capabilities of newer PDA devices, the developers, Scott Sherman, Mike McMullen, Dan Suslo, and Steve Work, created an application engine and server technology compatible with HTML, that is not dependent upon specialized subsets (e.g., Wireless Application Protocol) or PDA languages characteristic of other microbrowsers. See PDA macrobrowser for an illustration. See PDA microbrowser, Wireless Application Protocol. software Computer instructions stored on a medium which is reasonably portable and accessible by users. Actually, the distinction between hardware and software is much less clear than many people realize. It may seem reasonable to designate everything inside the computer as hardware and everything that holds information that can be inserted into external storage read/write devices as software, but that’s not really the best distinction. Floppy disks and computer chips are tightly integrated hardware/software combinations whether external or internal, so the matter is really one of accessibility coupled with structure. Since computer instructions stored on disks are easily read, written, and moved, they are thought of as software. Since computer instructions on computer chips are not easily read or written and not easy for a lay person to access or move, they are considered part of the hardware. The lowest level software functions are programmed into the computer chips themselves. At the hardware operations level, this software acts to start up the system, test it, bootstrap the device drivers to come online, and initiate the operating system to accept user input and output, and to otherwise communicate with the central processor. Some of these operating instructions may be read, in turn, from hard drives, CD-ROMs, cartridges, or other storage media. High level software interacts with the user through application programs.

S

Software is created with a variety of programming, editing, debugging, compiling, interpreting, and linking tools in a great assortment of languages, which are general purpose or optimized for specific types of programming. See programming. Software & Information Industry Association SIIA. A trade organization representing companies that create, distribute, and facilitate the use of information in print and digital formats. Evolved from an organization originally founded in 1968, SIIA was established through a merger of the Software Publishers Association and the Information Industry Association, in 1999. SIIA promotes the information industry, represents its members in government policy and regulatory affairs, and provides a business development support network for top executives in the field. SIIA is based in Washington, D.C. http://www.siia.net/ Software Engineering Research Network SERN. An engineering and research joint venture of the Department of Computer Science and the Department of Electrical and Computer Engineering at the University of Calgary, Alberta. It is sponsored by the government of Alberta, the University of Calgary, Motorola, Computing Devices, and Northern Telecom. Software Publishers Association SPA. See Software & Information Industry Association. Sol A very early microcomputer descended from the Altair and based on the Altair bus (S-100 bus). solar cell In the 1940s, Bell Telephone Laboratories developed a storage cell from thin strips of silicon which had the characteristic of developing a charge in the presence of light. Since the silicon is not directly depleted in this process, solar cells are not subject to the limited life spans of traditional wet and dry cells. Solar cells have since been developed and refined in many ways and are used in many aspects of electronics. See photovoltaic. Solaris A popular 32-bit operating system from Sun Microsystems that is commercially distributed, as is their SunOS operating system and, more recently, OpenStep. Solaris is multiprocessing, multithreaded, and network-friendly (using NFS), based on an open systems architecture. Many large Internet Services Providers, university systems, and enterprise local area networks (LANs) run on Solaris. Solaris is available for various Sun SPARC, Intel-based, and Motorola-based systems. solenoid A long, cylindrical, current-carrying coil with properties similar to a bar magnet, into which an iron bar will be drawn when current is applied to the coil. Solenoids are commonly used in circuit breakers which have replaced traditional fuses. See electromagnet. Sömmering, Samuel Thomas von (1755-1830) A Prussian anatomist and inventor, Sömmering was one of the earliest inventors of telegraphic technology. Based on the work of F. Salvà, he developed an electrochemical wire telegraph which signaled letters and numbers through the application of current from a voltaic pile to a specific wire such that it created bubbles in an acid bath at the receiving end.

Each wire corresponded to a character, with the wires and frame at each end looking very much like a threaded loom. This invention, which was demonstrated to the Academy of Science in Germany in 1809, predated Wheatstone and Morse technologies by three decades. Sömmering improved upon Salvà’s design by extending the transmission range of the device and later collaborated with Schilling, who made some significant contributions to early electromagnetic telegraphy. See Salvà i Campillo, Francesc; Schilling, Pavel; Steinheil, Karl August. sonar Sonar is currently considered to be the acronym for sound navigation and ranging (other phrases have been suggested). It is essentially a technology for generating and directing sound signals with the intent of analyzing the returning echoes to determine information about the size, shape, and relative distance of any objects encountered by the outgoing sound waves. Sound requires a medium in which to travel. It is, in fact, a disturbance of a medium and, thus, sonar is most commonly used for probing elastic media such as water and, to a lesser extent, air. Sonar cannot be used in space, where the lack of air and moisture or other sufficiently dense and elastic media prevents the transmission of sound. See sonar, history. sonar, history Sound and sound echoes are phenomena that can be directly sensed by humans through hearing and through tactile vibrations, so interest in sound technologies originated earlier than many other sensing technologies. Isaac Newton (16471727) made important contributions to our understanding of sound when he studied the transmission of sound through various media and noted that sound speed was related to the density and compressibility of the medium that was disturbed. He published his pressure theories of sound in 1686 and used his observations to calculate the speed of sound through air. In 1706, John Hodgson, a scientific lecturer and associate of Francis Hauksbee the Elder and Isaac Newton, reported on experiments with gun shots and suggested that the uniformity of the speed of travel of sound could be exploited to determine the distance of ships at sea and land objects, a concept central to sonar. One of the earliest known sonar devices was Daniel Colloden’s bell, which was lowered into Lake Geneva in 1822. When the bell was rung, a sensor on another vessel vibrated in response to the sound echoes, providing Colloden with a means to fairly accurately calculate the speed of sound in water. Modern sonar instruments owe much to the discovery of the piezoelectric effect by Pierre and Jacques Curie in 1880. The discovery led to the development of acoustical detection devices much more sensitive than Colloden’s early sound sensor. At the April 1885 meeting of the National Academy of Sciences, Alexander Graham Bell is reported to have presented two sound-related papers, one on his invention of the audiometer, the other on a basic sonar device. Della Torre, with whom Bell collaborated on the soundsensing experiment, presented the possibility of using sound echoes to detect a vessel at sea in the fog

(searchlights were common at the time, but not very useful in fog). Torre and Bell had used a gun and a receiving trumpet to obtain echoes from passing vessels, according to their size, up to a distance of about a mile. By the early 1900s, both sonar and early radar were being developed to prevent collisions at sea; the technologies share many general principles and terms. The sinking of the Titanic in 1912 increased the study and commercial development of hydrophones, water microphones that could be used to detect sound waves. These were quickly adapted for use on submarines for military reconnaissance during World War I and World War II. Early sonar devices operated in frequency bands that were audible to human operators. However, as electronic transmitters and sensing devices evolved, sonar increasingly used ultrasound frequencies inaudible to humans. See sonar. SONET Synchronous Optical Network. SONET is a set of ANSI telecommunications standards which specify a modular family of rates and formats for synchronous optical networks. SONET provides a standard operating environment for managing high bandwidth services, and incorporates multiplexing, service mappings, and standardized interfaces, so commercial vendors can develop interconnecting technologies. SONET has been adopted by the ITU-T as the basis for the Synchronous Digital Hierarchy (SDH)

transport system, and is a subset of this system. SONET is based on STS-1 which is suitable for T3, and SDH is based on STM-1, suitable for E4 transmissions. Communication between nodes, to permit control, provisioning, administration, and security, is accomplished through the Synchronous Transport Signal (STS) transmitting at a line rate of 51.84 Mbps. The STS comprises payload information and signaling and protocol overhead. Since the two ends of a SONET transmission may vary in format and speed, data are converted to the STS format, transmitted, and, when received, converted into the appropriate user format. OAM&P is integrated into SONET. See detailed information under the following SONET listings. SONET ANSI standards A number of important American National Standards of Committee T1 related to SONET are available from ANSI and described in the form of abstracts on the Web. See ANSI Standards Related to SONET chart. SONET frame The frame length is 8000 fps or 125 µsec. SONET uses Synchronous Transport Signal level 1 (STS-1) as its basic signal rate of 51.84 Mbps. SONET frames are organized in a row by column structure totaling 810 bytes. Transport overhead is contained in the first three columns and is subdivided to include section and line overhead. The remaining columns, from four to 90, are used for the Synchronous Payload Envelope (SPE).

ANSII Standards Related to SONET – Examples ANSI Standard

Title

Subtitle

T1.105-1995

Synchronous Optical Network

Basic Description including Multiplex Structure, Rates, and Formats

T1.105.01-1995

Synchronous Optical Network

Automatic Protection

T1.105.02-1995

Synchronous Optical Network

Payload Mappings

T1.105.03-1995

Synchronous Optical Network

Jitter at Network Interfaces

T1.105.03a-1995

Synchronous Optical Network

Jitter at Network Interfaces - DS1 Jitter

T1.105.04-1995

Synchronous Optical Network

Data Communication Channel Protocol and Architectures

T1.105.05-1994

Synchronous Optical Network

Tandem Connection Maintenance

T1.105.06-1996

Synchronous Optical Network

Physical Layer Specifications

T1.105.07-1996

Synchronous Optical Network

Sub-STS-1 Interface Rates and Formats

T1.105.09-1996

Synchronous Optical Network

Network Element Timing and Synchronization

T1.119-1994

Synchronous Optical Network

Operations, Administration, Maintenance, and Provisioning - Communications

T1.119.01-1995

Synchronous Optical Network

OAM&P Communications Protection Switching Fragment

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The STS-N frame consists of frame-aligned, byteinterleaved N STS-1 signals. The STS-Nc frame consists of concatenated STS-1 signals to form a multiplexed, switched signal that can be transported together. This is done to accommodate broadband services such as ISDN. Following is an overview of some of the bit rate speeds for the Synchronous Transport Signal levels and how they compare to European equivalents. This chart only indicates bit rates; the frame formatting for each system differs even further. U.S.

Europe

Bit rate

STS-1 STS-3 STS-12 STS-24 STS-48 STS-192

— STM-1 STM-4 STM-8 STM-16 STM-64

51.84 Mbps 155.52 Mbps 622.08 Mbps 1244.16 Mbps 2488.32 Mbps 9953.28 Mbps

SONET multiplexing SONET signals can be multiplexed to make efficient use of network capacity. There are a number of ways to accomplish this, as shown in the SONET Multiplexing Techniques chart. SONET optical interface layers SONET includes a hierarchy of interface layers. Each one builds on the previous; from high to low, they are path layer, line layer, section layer, and photonic layer. Individual layers communicate to peers on the same layer and to adjacent layers above and below. SONET path overhead In SONET, path overhead is transported with the payload until the signal is demultiplexed at the receiving end. The path overhead supports four classes: Class

Functions

Notes

Class A Payload independent functions Required by all payload types Class B Mapping dependent functions Required by some payload types

SONET Interoperability Forum SIF. An organization devoted to identifying and suggesting solutions to SONET interoperability issues, founded in 1994. Various workgroups work on topics such as remote login implementations and user requirements, interoperability with specific systems (e.g., TARP), architecture requirements, information models, access protocols and more. The SIF findings and recommendations are published as SIF Approved Documents. Here is a small selection to give an idea of the scope of the documents. Most are available online; some can be obtained in paper format upon request. Number SIF-007-1996

Focus

Title

Graphical User Interface Design Principles for the Development of OAM Graphical User Interfaces SIF-009-1197 Remote Login NE-NE Remote Login Implementation Requirements Specification SIF-020-1998 Testing IS to IS Abstract Test Suite SIF-023-1998 Information Modeling Network View Model for Connection Management and Fault Management NSIF-031-1999 Architecture Architectures for an IP-Based DCN NSIF-038-2000 Security NSIF Requirements for a Centralized Security Server

Class C Application-specific functions Class D Reserved for future use

SONET path terminating element PTE. The PTE is an element which multiplexes and demultiplexes the Synchronous Transport Signal (STS) payload and processes the path overhead as needed to originate or access it. If necessary, the PTE can also modify or terminate it. See SONET, Synchronous Transport Signal. SONET timing In SONET networking, synchronization is accomplished by referencing a high accuracy clock and information from its slaves, so synchronization characters between equipment nodes are not used. Due to the high data rates carried by SONET, it is important to maintain clock accuracy. The three major timing modes supported are external timing based on a clock, generated free run/holdover timing from an internal clock, and OC-N signal line timing. SOP standard operating procedure. sound Radiant mechanical energy produced by vibration, which requires a physical medium for its transmission (such as air), and is detected by hearing, accomplished through physical sound-detection, perception, and interpretation by the nervous system. Compared to light and heat, sound waves move very slowly. Human sound perception through hearing covers a frequency range from about 20 Hz to about 20 kHz, although lower, and sometimes higher frequencies are felt, though not heard, through vibrations in the body. Other creatures perceive broader, narrower, or more specific frequencies, and sound is a ubiquitous means of species communication. Enough is known about the nature of sound waves to record, reproduce, and modify them, and to propagate them over great distances. Humans can project unamplified voice through the air for a few dozen or

SONET Multiplexing Techniques Technique

Type of interleaving

Notes

Interleaving

Interlaces individual bytes.

Reduces overhead at receiving end.

Single-stage interleaving

Direct byte interleaving.

STS-N signal created directly.

Two-stage interleaving

Direct byte interleaving.

Accommodates European ITU-T rate.

hundred yards, depending upon atmospheric conditions. Whale songs will resonate for thousands of miles through water, although whale communication distances have been drastically reduced by interference from industrial shipping noise. sound spectrograph An instrument for measuring the structure of speech and displaying it visually, developed in the early 1940s by Bell Laboratory researchers. This opened the door to more objective, quantitative measures of speech, information that is of interest not only to speech therapists, physicians, and educators, but also to developers of communications technologies. sounder A sound amplification device incorporated into a communications receiver, usually a telegraph receiver, to make the code clicks audible to a human operator. Sounders were invented when it was noticed that telegraph operators had learned to interpret Morse code clicks and transcribe them manually faster than a paper tape could print the messages. A mainline sounder was an adaptation that allowed variable adjustments without a relay. See resonator. SP stream protocol. See byte-stream protocol. space division multiple access SDMA. One of two common optical multiplexing techniques which utilizes an angle diversity receiver, that is, multiple receiving elements receiving from different directional angles. See wavelength-division multiple access. space-charge field In electronics, an electric field created outside the physical surface of a conductor or semiconductor.

space-to-mark transition, S-M transition In telegraphy, the momentary change when the system reverses polarity, or changes from an open to a closed circuit. At this point, a small amount of delay must be taken into consideration, which can be plotted on a timing wave. The reciprocal is the mark-to-space transition. Spaceway A commercial constellation of geostationary communications satellites from Hughes Communications. Spaceway was formed from the merger of the Hughes Galaxy Satellite Services and the PanAmSat Corporation. Hughes Electronics is a subsidiary of General Motors Corporation. Spaceway is intended to be a global broadband communications system with service planned for 2003. spade lug, spade tip A small, flat, notched (somewhat U-shaped) conductive connector attached to the end of a conductive wire in order to easily secure it to an electrical terminal by sliding the end around the mounting screw and applying pressure via a bolt, or by soldering. Spade lugs are still common inside small residential phone wire junction boxes, but in large installations, punchdown blocks and modular components are more prevalent. See lug. spaghetti code jargon Software code that is disorganized and logically tangled. Code often turns into spaghetti code because it can be difficult to solve a problem and create an efficient design until more aspects of the concept are explored and known. Consequently, half-way through a project, many programmers exhort, “Time for a rewrite!” The code

SONET Interface Layers Layer

Peer

Notes

Path

Services and path overhead mapping

Transport services between path terminating equipment (PTE). Mapping signals to line layer format.

Line

SPE and line mapping

Transport of path layer payload and overhead across physical medium. Synchronization and multiplexing.

Section

STS-N and section overhead mapping

Transport of STS-N across physical medium.

Photonic

Optical conversion

Transport of data across physical medium.

Conversion between STS and OC signals.

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may have become bulky, obscure, too hard to follow or maintain to be practical, or it may use slow, inefficient routines where better ones have been discovered or developed along the way. Spaghetti code often develops when software is created by committee or individual programmers in the project are intent on following personal methods for its development that don’t mesh with the other portions of the code. It is often observed in the software industry that code tends to decrease in efficiency and elegance of design in proportion to additional people added to a project. spam slang A term widely used on the Internet to describe annoying, unsolicited, irrelevant, illegal, or worthless communications, usually in the form of email or public postings. It’s generally said that the word originated as a tongue-in-cheek reference to a Hormel meat product called Spam, which is frequently pilloried and satirized in the media. Whether or not that is the case, the spam on the Internet, especially in the form of unsolicited email bulk promotion of get-rich-quick schemes and sex sites, has become a big problem due to the intrusive way in which the spammers violate the space and privacy of recipients. Not as often acknowledged is the fact that spam causes substantial expense to ISPs, and general annoyance and expense to users who pay for email messages individually or for extra storage space for mail messages on their online accounts. Junk email creates ill will and a negative impression. It is unwise for legitimate businesses to send unsolicited commercial messages to email addresses, as many recipients of spam will boycott those businesses indefinitely. It is also unwise to send exaggerated and unsupported claims, as there are laws governing false advertising that will probably be more stringently enforced as the number of complaints to authorities increases. See spamming. spamming slang Posting or emailing irrelevant, annoying, illegal, or unsolicited opinions or promotional materials, sometimes through anonymous mailers or with false return email addresses. In 1997, many ISPs were forced to install anti-spamming software on their systems to stem the floodtide of these types of messages. Many ISPs will now also reject an email message which does not have a legitimate sending address in the mail header. On the USENET news server, also in 1997, many formerly useful discussion groups became worthless (especially business-oriented groups) due to the large volume of spam, and some recovered only by going to moderated status (a strain on the many volunteers who have to check all those messages before reposting them). See cross-posting, spam. SPAN Switched Port Analyzer. A Cisco Systems network switch feature for extending the monitoring capabilities of existing network analyzers into a switched Ethernet environment. SPAN takes the traffic at one switched segment and mirrors it onto a predefined SPAN port. A network analyzer which is attached to the SPAN port can monitor traffic on other compatible switched ports.

spanning tree algorithm STA. A standard technique described in IEEE 802.1 which is incorporated into bridges in computer networks. For example, in Fiber Distributed Data Interface networks, it is incorporated into bridges that connect the primary and secondary rings. The spanning tree logic can prevent duplicate bridging and allows the backup ring hub to handle bridging if the primary ring hub fails. See Fiber Distributed Data Interface, Token-Ring. Spanning Tree Protocol STR. A protocol based on IEEE 802.1d that provides resiliency through system and link redundancy that is especially suitable for virtual local area networks (VLANs). spark A brief, bright, heat discharge, often from electrical or friction sources. Sparks are generated by spark plugs to fire up an engine or by matches or lighters to fire up combustible substances such as wood, cardboard, or lighter fluid. Unintentional sparks may be dangerous and may occur as a result of incorrect electrical connections (shorts, crossed wires), inadequate insulation, or contact with unintended conductive substances such as water. spark coil A device incorporating an inductive magnetic core surrounded by helical windings of conductive materials used to generate a spark. The spark coil was typically used in conjunction with a condenser and vibrator (or interrupter) for telecommunications applications. Spark coils are still used to ignite internal combustion engines, but for many electronics applications, transformers began to replace spark coils in the early 1900s. See armature, coil, dynamo, induction, winding. spark gap The distance across which an electrical spark jumps between electrodes. Adjusting this gap affects the behavior of the spark. If the gap is too large, the spark may not jump the gap. SPARS code Society of Professional Audio Recording Studios. A three-letter code found in compact discs which indicates the analog or digital nature of a portion of the recording history. For example, ADD indicates that the original recording was analog, the mixing was digital, and the mastering stage was digital. See compact disc. Spartan A family of satellites designed for remote sensing. In 1997 an unsuccessful Spartan mission occurred when astronauts failed to turn on the satellite before releasing it into space. Initial efforts to retrieve the satellite were unsuccessful and it was manually retrieved later. In 1998, a 1 1/2-ton Spartan satellite was successfully used for capturing images of the Sun’s corona from space. Before the Spartan was retrieved by the crew of the Space Shuttle Discovery in November 1998, it had already beamed hundreds of images to ground controllers. One of the interesting aspects of the Spartan 207 multipurpose satellite was a 132pound Inflatable Antenna Experiment (IAE) that was deployed aboard the Space Shuttle Endeavor STS77 mission. The IAE, resembling a flat, stiff parachute when inflated, was developed by JPL and L’Garde, Inc. as part of NASA’s In-Space Technology Experiment Program.

The Spartan 201 satellite, one in a series of remotesensing meteorological satellites, as part of a prelaunch Crew Equipment Integration Test (CEIT) in the Kennedy Space Center. [NASA image.]

The Spartan 201 is held by the Space Shuttle Columbia’s Remote Manipulator System (RMS), December, 1997, over the Pacific Ocean. The RMS, designed in Canada, released the satellite into free flight. [NASA images.]

SPCAS See SPC Allocation Service. SPEC See Standard Performance Evaluation Corporation. Specialized Common Carrier decision A decision by the Federal Communications Commission (FCC) in 1971 to permit competition with AT&T in the provision of specialized voice and data services. Specialized Mobile Radio SMR. A well-established analog, trunked two-way radio dispatch system favored by commercially dispatched passenger and cargo fleets, public safety, and local services (e.g., taxi). SMR enables a group of radio communications users to share a common channel through a central station. Allocated frequencies are in the 800- and 900-MHz ranges.

In North America, more than two million users subscribed to SMR services, a number that was gradually increasing until bandwidth bottlenecks began to impact the service. In response, the Federal Communications Commission (FCC) made available additional radio spectrum frequencies in the 900-MHz range, in the mid-1990s, and above 860-MHz in 1997, thus opening the door for SMR services to compete with niche areas of the cellular market. With digital technology being adapted to SMR services, considerable changes took place. First, Motorola developed a system called the Motorola Integrated Radio System (MIRS) and, more recently, Enhanced Specialized Mobile Radio (ESMR) is catching on, which makes ESMR competitive in some areas with cellular services. While SMR spectrum is more limited than cellular, it can be used over a longer range. The upgrade to digital technology has greatly accelerated the increase in ESMR users in North America and Europe due to the improved quality of the sound and greater variety of services offered. See Enhanced Specialized Mobile Radio. Specification and Design Language SDL. An ITUT-defined language for the description and specification of the behavior of telecommunications systems. XDL is an extension of this language. spectral spreading See spread spectrum clocking. spectrograph An instrument for spreading light into its spectral components. By studying the brightness of the spectrum at each wavelength, it is possible to study the composition and characteristics of substances through their light-emitting properties and patterns. This is widely used by astronomers studying our solar system. spectroscopy A technique used by scientists to study the composition and/or characteristics of a substance based on its light-emitting properties. In astronomy, spectroscopy has enabled more detailed study of stars, beyond distance and brightness. spectrum In general, a continuous sequence or range of some property or radiant energy. Many phenomena are described in terms of their characteristics or position within the spectrum of radiant energy, including electromagnetic, radio, sound, visible light, specific colors, etc. See band allocations, radio, sound, visible spectrum. speech recognition The process of receiving, interpreting, and parsing spoken words. On computers, this is often accomplished with a microphone input device, an analog-to-digital peripheral card, and a software program that works independently or in conjunction with other programs such as word processors. It may also include noise-canceling features that help to separate the voice of the speaker from ambient room noise such as the hum of computers or low conversations in the distance. Speech recognition is distinct from voice recognition in that voice recognition is the processing of the particular characteristics of a specific voice so that it can be recognized, such as in a security identification

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system. Voice recognition does not involve making sense of the content of the message, as does speech recognition. Speech recognition systems typically require a minimum sampling rate of about 3000 samples per second in order to reliably recognize words. In many systems 8000 samples per second is used. Speech recognition can be used to dictate text, give commands, and send information over a communications system in digital or altered form. Since speech recognition is a complex process, most current systems are specialized to recognize a specific limited vocabulary as spoken by a number of speakers in a specified language or a general (or specific) vocabulary as spoken by one particular speaker. More sophisticated systems can recognize and react to sentences and grammatical structures. Many speech recognition programs have training algorithms (speaker adaptive algorithms) included so the software can gradually adapt to the idiosyncrasies of a particular speaker’s means of expression and pronunciation of certain words. In the mid-1990s, speech recognition computer software began to be reliable and inexpensive enough to interest small businesses and individual consumers, and its use will probably spread through a variety of applications, perhaps adding another means of input to standard software such as word processors and electronic mail programs. See phonemes, voice recognition. speech synthesis The reproduction of audible human communication, through the use of computers. There are many different ways to create synthesized voice. Sound samples of human voices uttering certain words, sounds, and syllables can be recorded as separate entities, stored digitally, and then combined and played back to create words and phrases. Other schemes, such as pure digital recreation of voice-like sounds are also available, but tend to have a distinctly mechanical quality to them. The naturalness of the sound of synthesized voice is highly variable. Just as a graphical rendering program in the hands of a good artist results in better pictures than in the hands of a nonartist, speech programming and re-creation done by a person with a good ear for sounds yield better results than when done by someone without a sense of the rhythm, timbre, and pitch of human voice communications. Much can still be done, within the capabilities of the current technology, to improve speech synthesis. The most famous synthesized voice in the world is probably that of Stephen Hawking, world acclaimed physicist who talks indirectly through words and phrases programmed into a computer keyboard installed on his wheelchair. When Mr. Hawking is finished composing the message, it is replayed to the listener through a speech synthesizer. Synthesized voices are used in multimedia applications, on storybook CD-ROMs, in automated telephone mail order and banking systems, etc. See phoneme, speech recognition, voice recognition. Speech Technology and Research Laboratory STAR. A division of SRI International which engages

in world-class research in speech technology using engineers, linguists, and computer scientists. Technology developed in the STAR lab is fed to Nuance Communications for commercial development for telephony applications. Of particular interest to researchers is natural speech recognition (without the usual training to recognize a particular individual’s voice) that can provide automated phone services or voice-based securities trading. Other areas of research include text-to-speech translation, visual information systems development, and digital encoding of audio signals. speed dialing A means of keying in a shorter code to represent a longer one in order to speed up the dialing of long phone numbers. See abbreviated dialing. SPF 1. shortest path first. 2. See stateful packet filtering. SPHERE System A microcomputer system from SPHERE Corporation that was sold as a complete unit with a black and white CRT display, keyboard, 4 kilobytes of memory, serial port, and realtime clock. It was capable of running an extended BASIC compiler. A color CRT display was even available as an option. It was shipping in the fall of 1975, before the Tandy TRS-80 and Apple computers. The Utah company ran full-page ads in Popular Electronics offering the system for only $860, or $350 for just the logic board, yet for reasons unknown, the system didn’t catch on. See Altair, LNW-80.

The SPHERE came as an assembled unit, the first microcomputer to come standard with a monitor and keyboard, or it could be purchased as a kit; either was under $900 in 1975.

SPHIGS Simple PHIGS. See PHIGS. SPI 1. Security Parameters Index. 2. Service Provider Interface. SPID See Service Profile Identifier. SPIE The International Society for Optical Engineering. SPIE is a nonprofit professional society in Bellingham, Washington, dedicated to advancing research, engineering, and applications in optics, photonics, imaging, and electronics. SPIE produces educational publications, sponsors conferences and

workshops, and now also provides Web resources in cooperation with the Institute of Physics (IOP). http://www.SPIE.org/ http://optics.org/ SPINS See Security Protocols for Sensor Networks. SPIRITS A network architecture that supports SPIRITS services originating in the Public Switched Telephone Network (PSTN) interacting with the Internet. In simple terms, it is an architecture to support popular telephone services over Internet phone connections, such as Internet-based Caller ID, Call Forwarding, etc. The SPIRITS architecture was submitted as an Informational RFC by Slutsman et al. in June 2001. Implementation of SPIRITS services requires an Internet Protocol (IP) host installed with SPIRITS-supporting software and identification (e.g., PINs) for communicating with other SPIRITS servers. Once a host is SPIRITS-enabled, a user may connect to the Internet and register a service session and optionally specify the session duration. The SPIRITS architecture consists of a number of service control, service switching, client, server, and gateway functions as well as a number of interfaces as follows: Interface

Notes

Interface A

A conduit for PINT requests/responses. Supports service session subscription, registration, and activation of a SPIRITS service. Notifies the subscriber of incoming calls and call information and submits a subscriber’s choice of call disposition to the SPIRITS gateway. Client/gateway communication. The gateway may, in turn, communicate with the SPIRITS server or may act as a virtual server, terminating requests without relaying them. SCF to client communication, sending parameters associated with the applicable IN triggers. The SCF translates user requests into corresponding actions. PINT to SCF requests.

Interface B

Interface C

Interface D

Interface E

See PINT, RFC 2995, RFC 3136. splashing When using competitive operator services for long-distance calls, if the caller places a call from San Francisco to Portland and the alternate service is based in Los Angeles, the call is said to be splashed if the billing is determined by the distance from Los Angeles to Portland. See Operator Service Provider. splice v. 1. To unite or combine separate lines, usually by weaving together the individual strands. 2. In electrical splices, care is usually taken to match the data lines so as not to cross one type of data channel

with another, and bare wires are generally covered with an insulator such as a cap, electrical tape, or plastic shrink sheath to prevent short circuits or shock. splitting A ubiquitous function in computing in which data or other transmitted information is broken up into streams, channels, chunks, or other units to facilitate processing or transmission or to conserve resources. Splitting is usually used in a context where the data will be reassembled or rejoined when it reaches its intended destination or is needed by some application. See joining for a detailed explanation. SPNE signal processing network equipment. spoofing 1. Deceiving, covering up the identity of, impersonating, or otherwise conveying an impression of being something else. 2. A means of gaining unauthorized access to a premises or system by deceit, impersonation, or other misrepresentation. spoofing, facsimile Facsimile devices, especially the desktop models, have not traditionally been speedy machines and many are designed to time out if no data is received for a while (in order not to tie up phone lines). With the advent of faxing over faster packet-based network connections, facsimile delays can lead to time-out problems in the connection that would interfere with the function of the fax machine. Spoofing is a means to extend the tolerance for these delays so that the fax can finish with the machine disconnecting. By padding and other methods, delays and packet “jitter” can be smoothed over to spoof a realtime voice-line connection. A number of vendors have access server technologies that take into account the needs of both store-and-forward and realtime facsimile protocols (ITU-T T.37, T.38). Fax spoofing may eventually become unnecessary as fax machines are gradually replaced by printers with direct connections to the Internet that can print a variety of file formats (raster, Adobe PostScript, PDF, etc.). This solution not only is much faster, but also enables the printing of perfect copies as opposed to low-resolution fax copies. It would also eliminate the problem of people feeding pages into their fax machines upside-down (resulting in blank pages at the receiving end). spoofing, network In network traffic routing, a means of rerouting, or otherwise changing the destination of a transmission by mimicking the destination through responses, signals, or other identification. Spoofing has legitimate purposes, such as testing and modeling, or overcoming problems of latency in slower devices, but often the spoofing is intended to gain unauthorized access to a system or to impersonate a system and send substituted information. Reports of malicious spoofing on the Internet began to emerge in the mid-1990s. Spoofing can be set up at the beginning of a session or can be inserted into a session after it has been established. The first method may be harder to detect, while the second may be a means to eavesdrop on information the source system thinks it is sending to the original destination, which is now the spoofed destination. In general, the spoofing is carried out by impersonating a trusted destination IP address. The

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spoof can sometimes be detected if the IP address is found to originate on the local system rather than on an external system. Spoofing occurs for many reasons. It can enable a user to intercept programs or information that may not otherwise be accessible or it can be used to send bogus responses to requests from the originating system. It can also be set up to compromise the ability of a system to carry out its normal functions. A denial of service attack is one in which a service (e.g., a Web server for a stock quote or online auction system) is made unavailable to normal users. By setting up a loop that ties up or floods the system, for example through a half-open connection that overflows, denial of service can be achieved. This doesn’t usually compromise the information on the attacked system, but may harm it by denying legitimate users access to the service. The host system may not be aware of the problem until customers begin to complain. Since the mid- and late-1990s, various dynamic routing techniques and packet traffic monitors have aided in preventing and detecting spoofing. See Computer Emergency Response Team, Computer Incident Advisory Capability. spoofing, Web site This is a subset of network spoofing that specifically spoofs or impersonates a Web site at another location. A vulnerability exists within browser software supporting HTML frames prevalent in the late 1990s. Subsequent versions of browsers have been updated to help prevent this type of spoofing (e.g., Netscape Communicator 4.51). Web site spoofing is usually a malicious activity intended to mislead, inconvenience, or harm. A Web site can be spoofed to make a site look bad (e.g., maligning a commercial site) by inserting insulting, poorly designed, or shocking images or text into an otherwise normal-looking site. Spoofing can also be similar to the Trojan Horse concept wherein something desirable appears to be offered (but not given) to the user in order to gain entrance to a location or information repository. The user may think he or she is getting a free product sample, for example, when the spoofed site is actually capturing names and mailing addresses (in fact this type of fraud can be carried out on a nonspoofed site, as well). Not all Web site spoofs exploit browser vulnerabilities. Some of them rely upon human trust and error. One type of Web spoof impersonates the layout and functions of another Web site and may or may not spoof the original IP address or domain name (Web sites are sufficiently high in information content that an IP address or domain name change may not be noticed by the user). For example, in summer 2000, someone spoofed the login page for the PayPal online financial system, which enables users to conduct online monetary transactions through user accounts. The Web page was designed to clandestinely capture names and passwords. The perpetrators then sent out bulk email that looked like a legitimate PayPal notification with a clickable Web address embedded in the email

message. However, the embedded URL didn’t link to www.paypal.com, it linked to www.paypaI.com with a capital “i” rather than a lowercase “l”. People couldn’t easily see the deliberate misspelling and anyone who linked to the site and tried to log on gave away his or her login name and password. This could then be used to access the real PayPal account to enable the perpetrators to transfer funds. Fortunately, the fraud was discovered quickly, before significant harm was done. This kind of spoofing has a good chance of landing the perpetrators in jail. spool v. An acronym for “simultaneous peripheral operations on line,” a means of running scanners, printers, plotters, video capture systems, or other peripherals while other computing tasks are ongoing. In earlier nonmultitasking computer systems the acronym was misleading, since spooling was a way of saving information in a file so it could run as a batch job later, rather than as a simultaneous process. Spooling as we know it now more accurately reflects the acronym. It is a technique for improving efficiency by accommodating the different operating speeds of a number of types of peripherals and processes by scheduling and optimizing the exchange of handshakes and data transmission. Spooling is especially popular for creating files that will be printed as a background task or sometime later (e.g., overnight, when printers aren’t so busy, or when the computer isn’t engaged in CPU-intensive functions). On multitasking systems, it is not necessary to wait for a print, plot, or other peripheral job to finish to continue word processing or drawing, but it may slow current processes. Thus, the system may schedule the printing job to run while the user is away from the keyboard or engaged in computing tasks requiring less processing power. The resource management software routines can be designed to sense when resources are available and carry out the print job. On single-tasking or task-switching systems, however, with peripherals that don’t support a queuing system, wait time can be a problem while a file is processed or printed. For example, plotters tend to print rather slowly. If the user must wait for 25 minutes while a plot is created, productivity is lost. By sending the plot to a software spooling process (or a hardware spooling buffer) and plotting it at a convenient time, the user can continue working uninterrupted. spread spectrum A technique used with radio-frequency-generating systems to spread the emitted wavelengths over more than one frequency, in either predefined or random patterns (or a combination of these). In telecommunications, spread spectrum is generally divided into frequency hops, a system developed over 50 years ago by Hedy Lamarr, and direct sequencing, which utilizes the noise-like characteristics of pseudorandom sequences to control a phase modulator. At the sending end, specific types of noise are incorporated into the signal, which is spread over a wider frequency range. At the receiving end, a lower bandwidth version of the original signal is recovered. Spread spectrum is used for a number of reasons: it can reduce overall interference with other radio

signals, can be more difficult to detect, intercept, or decode, and more difficult to jam, thus providing several types of security not possible with single-frequency transmissions. There are tradeoffs when using spread spectrum. More bandwidth than normal is required to transmit the signal. Spread spectrum broadcasts are not only used in covert or private communications, but are now also used as a means to optimize increasingly limited broadcast space due to increased demand. In the United States, unlicensed spread spectrum transmitters are permitted to broadcast within specified frequency ranges. As an example, the 900-MHz cordless telephones and a number of wireless local area networks (LANs) operate in the unlicensed spread spectrum frequencies. Pseudonoise, or direct sequence spread spectrum, is a technique used in local area wireless networks (LAWNs). Redundant data bits called chips are incorporated into the transmissions and the receiver must have knowledge of the spreading code to remove the added chips and decipher the incoming message. The insertion of chips provides a means to provide more frequencies within a given area, with a tradeoff in speed. The throughput of this type of system is about 2 to 8 MHz. The Federal Communications Commission (FCC) regulates the amount of time that may be spent on any one channel. For example, in the ISM band of 902 to 928 MHz, the frequency hop on a particular channel must not exceed 0.4 seconds once every 20 seconds. Similarly, in the 2.4- to 2.484-GHz range, the interval is not more than once every 30 seconds. Recommendations are also being drafted by the IEEE. See frequency hopping, spread spectrum clocking. spread spectrum clocking In electronics, many components emit radiation. The smaller and more tightly these components are bundled, the more likely there is to be undesirable electromagnetic interference (EMI) from neighboring parts. This is especially true in precision very large-scale integration (VLSI) electronic components generating high clock frequencies. Spread spectrum clocking is a means of spreading the spectral emissions generated by the clock signals to reduce the overall EMI. This is often done through frequency modulation (FM). See spread spectrum. spreading loss In a beam of radiant energy, loss associated with the geometrical spread of the energy as distinct from absorption and scattering. Thus, the peak power level that emanates from the energy source is reduced as the energy propagates outward. It is also known as energy spreading loss (ESL). To better understand this, imagine the light from a flashlight beam gradually spreading as it travels away from the source. When the beam hits the upheld palm of a friend standing several feet away, the strength or power of the light is lower than if the palm is in front of the light a few inches away. The rest of the light will spread around the palm, passing it by, even if no absorption or other type of loss occurs. Acoustic energy, like electromagnetic energy, exhibits

spreading loss, because it radiates outward, which makes spreading loss an important consideration in sonar technologies as well. When spreading loss occurs in energy forms traveling through the air, it may be termed free air loss. Spreading loss can vary as frequencies vary and as frequency compositions vary. For example, spreading loss in a coherent beam of laser light is far less than the spreading loss in a beam from a flashlight. Spreading loss becomes greater as the distance from the source increases (e.g., a radar echo traveling towards a target will exhibit spreading loss not only on the way to the target but also on the way back). It is especially important to account for spreading loss in very remote sensors, such as satellite imaging systems. Range-spreading loss associated with satellite imaging sensor data may be compensated for, based upon distance, incident angle, and known characteristics of the sensing medium. Some commercial satellite image products are routinely processed for rangespreading loss (e.g., synthetic-aperture radar products). In fiber optic transmissions, spreading loss is reduced or mitigated in a variety of ways, including reducing the number of components and installing active relays. Spreading loss in a number of media can also be compensated for by redirecting the spread energy back into the main beam. See absorption, attenuation, scatter. spreadsheet A columnar ledger sheet used for listing items and, often, financial information. The advantage of electronic spreadsheets is that they can be configured to dynamically change cells which are related to information in other columns (such as calculations, totals, etc.), if the information in the original column is changed. This is extremely convenient for testing budget scenarios, for example. Electronic spreadsheets are great time savers and tend to be much less prone to arithmetic errors than hand-calculated equivalents. Sprint A well-known telecommunications services company, Sprint was one of the early companies to make dialup access to nationwide ISPs affordable, in the early 1990s. Sprint began as a small telephone company in Abilene, Kansas, founded by Cleyson L. Brown, in 1899. The Brown Telephone Company provided an alternative to the Bell system and grew and was reorganized as United Utilities. By the 1950s, it was the second-largest non-Bell company in the U.S. In 1972, the name was changed to United Telecommunications. By the late 1970s, the company began installing fiber optic links and soon after established UNINET, then the third largest commercial packet data network in the world. In the mid-1980s, Sprint became known for its long-distance services. Sprint established the first coast-to-coast, national fiber optic data and telephone system as Sprint International after which United Telecommunications became Sprint Corporation, in 1992. In 1995, Sprint moved into the mobile market by acquiring wireless licenses for 29 major trading

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areas auctioned by the Federal Communications Commission (FCC). In 1998, Sprint introduced ION, simultaneous voice, video, and data services over existing connections. There was an unsuccessful attempt to merge Sprint and WorldCom, a merger that did not receive U.S. government approval. Thus, Sprint focused its efforts upon building Sprint PCS into a major wireless services vendor. SPS See Standard Positioning Service. spud bar A tool somewhat resembling a cross between a pry bar and a long-handled, short-bladed spade. The handles may be D-shaped or ball-shaped and the blades may be replaceable. These are useful for breaking up tough soil clots for installing utility poles in areas where it is not practical or possible to bring in mechanized diggers (they’re also handy for scraping asphalt lumps and old roofing or siding materials and for making holes in thinner patches of ice). SPUD small planned unit development. spur 1. A foot spike worn by line workers to improve contact and traction when manually climbing utility poles to carry out maintenance, testing, or repair. 2. A tributary or offshoot from a main line, as in a railroad track or communications spur line. Spur lines may run to the end of a cul de sac, a pier, or other terminal point where there is an obstruction or no further need for the line to continue. Sputnik I The world’s first artificial satellite, launched by the Russian Federation on 4 October 1957, studied the ionosphere and heralded the space age. It transmitted in a frequency range just above global frequencies for standard time signals, so that those listening in, which included Earth stations all over the world and a large number of amateur enthusiasts, would be able to monitor and report the status of the satellite. The project was announced in print by the Russian Federation several months before its launch so that results of communications from the satellite could be reported. See Radio. Sputnik 2 The world’s first successful launch and retrieval of a living creature, Laika, a dog, was carried out by the Russian Federation in Sputnik 2 on 3 November 1957. This craft also studied space radiation and used a slow-scan TV camera to relay images to the ground. SQL Structured Query Language. A widely used, structured data sublanguage coding system for querying database information (e.g., Oracle). Most professional database programs support SQL-format files or can import/export SQL instructions. SQL emerged from technical descriptions of relational databases documented by computing professionals such as E.F. Codd. Based upon this model, IBM developed SEQUEL, the forerunner to SQL. In 1979, Relational Software, Inc. introduced a commercial implementation of SQL that became integral to the Oracle database program. The company later became Oracle Corporation. SQL has been supported and standardized by a number of prominent organizations, including ANSI and

IS/IEC. Embedded SQL comprises SQL statements within a procedural programming language as well as certain extensions to standard SQL statements. Square A data-securing block cipher system developed by Joan Daemen and Vincent Rijmen. Paulo Barreto and George Barwood developed a fast implementation of the algorithm for the Pentium II that can be downloaded from the Web. Square was used as the basis for the development of Rijndael, an important system used by the U.S. government. See Rijndael. SR Symbol for left-hand slant polarization (ITU). SRA See system reliability architecture. SRAPI Speech recognition API. A speech recognition and translation applications programming interface (API) developed by the SRAPI Committee, a Utah nonprofit corporation consisting of some wellknown vendors of various audio and multimedia products. http://www.srapi.com/ SRGP See Simple Raster Graphics Package. SS7 See Signaling System 7. SSAC13 Signaling System Alternating Current No. 13. A British automatic 1VF signaling system for transmitting supervisory telephone signals between private branch exchanges (PBXs) in the 2280-Hz frequency. Using the two-wire section of a transmission path, signals may be sent in one direction or the other (but not both at the same time), although some implementations use four wires for two-way signaling. SSAC15 Signaling System Alternating Current No. 15. A British private telephone line signaling system designed to operate in the 2280-Hz frequency. Each line has two transmitting lines and two receiving lines such that it is suitable for setting up a wide-area network (WAN) with two or more private branch exchanges (PBXs) and the appropriate wiring and interface cards. BTNR 181 is the British Telecom Signal Systems SSAC15 standards description. SSB See single sideband. SSCS See Service Specific Convergence Sublayer. SSCOP See Service-Specific Cornnection-Oriented Protocol. SSCP 1. See Service Switching and Control Point. 2. See System Services Control Point. SSD 1. Secret Service Division. 2. Service Selection Dashboard (Cisco Systems). 3. shared secret data. Encryption information shared between negotiating systems for purposes of security. In mobile communications environments, SSD is divided into authentication procedures (SSD-A) and privacy/confidentiality (SSD-B) with SSD information shared between a user mobile handset and an Authentication Center (AC) and sometimes also a Visitor Location Register (VLR). SSD is documented in ANSI-41. SSEC See Selective Sequence Control Computer. SSL See Secure Socket Layer. SSO single sign-on. SSP See Service Switching Point. SSRP See Simple Server Redundancy Protocol. SSTO Single-Stage to Orbit. SSTV See slow scan television. ST 1. See Scheduled Transfer. 2. signaling terminal.

3. straight-tipped. 4. systems test. ST2+ A connection-oriented, routable, multicastcapable Internet protocol for providing native ATM circuits for applications that require bandwidth guarantees and Quality of Service (QoS). ST2+ is an updated version of STII (ST2), specified in 1996, which has an Internet Protocol V.5 (IPv5) designation. See ST2+/UNI, RFC 1946. ST2+/UNI Stream Protocol Version 2+. An evolutionary descendent of STII and a version of a previous ST2+ providing native ATM support for ST2+, this version of ST2+ was specified for UNI 3.1 in 1998. ST2+ is an ATM-based, connection-oriented Internet protocol for communication among ST2+ agents. The protocol is designed to extend UNI 3.1/ 4.0 signaling functions, to reduce certain signaling limitations, and to manage resources more efficiently in ATM and non-ATM networks. The protocol specifies the interaction between ST2+ and ATM on three planes that correspond to the ITU-T B-ISDN Protocol Reference Model: Plane

Notes

user

Specifies encapsulation of the ST2+ DATA PDU into the AAL-5 PDU Specifies the Null FlowSpect, Controlled-Load Service FlowSpec, and the Guaranteed Service FlowSpec mapping for UNI 3.1 traffic Specifies encapsulation of the ST2+ SCMP PDU into the AAL-5 PDU, the relationship between ST2+ SCMP and PVC management (for ST2+ data), and the interaction between ST2+ SCMP and UNI 3.1 signaling

management

control

See byte-stream protocol, STII, RFC 2383. STII, ST2 Stream Protocol Version 2. A connectionoriented Internet protocol which brings together SCMP (for signaling and control) and ST (streaming protocol). A connection must be set up between sender and receiver before datagrams are transmitted, and flow quality is accomplished through datagram scheduling by the routers. In contrast, a great deal of Internet traffic is connection-oriented, in that the receiving system doesn’t have to be determined to be online before a transmission is sent. ST2 has an IPv5 designation. See ST2+, RFC 1819. STA 1. See spanning tree algorithm. 2. Science and Technology Agency. Japan’s organization to support research and development, and to plan and coordinate national science and technology. Founded in 1956. stand alone, stand-alone, standalone A system or device providing a self-contained service or function, independent of other major components. See turnkey system.

standard cell A fragile, special-purpose cell providing very small amounts of electrical current (1.019V) for short periods. standard network variable type SNVT (pron. snivit) A common variables framework element designed to support interoperability. The term is especially associated with the LONWorks control automation system, though it is applicable in a general sense to other types of network devices where predefined network variables have been associated with various units within the system (e.g., degrees, meters, volts, etc.). Standard Performance Evaluation Corporation SPEC. A nonprofit organization supporing the establishment and maintenance of standardized, relevant benchmark computer performance evaluation tools that can be applied to various high-performance systems. http://www.specbench.org/ Standard Positioning Service SPS. One of the precise location data signals transmitted from Global Positioning System (GPS) satellites. This signal is available without charge for private and commercial use and is not encrypted. It provides information about the functioning of the satellite and its approximate location. Combined with information from three or four other satellites, the user can pinpoint a location with horizontal and vertical accuracies up to about 100 m and 340 nsec of time, depending upon the quality and accuracy of the receiving equipment. See Global Positioning System, Precise Positioning Service. Standards Australia International, Ltd. SAI. An Australian standards organization with strong international activities focused on supporting businessto-business services based on knowledge sharing. The organization was established in 1922 as the Australian Commonwealth Engineering Standards Association and became the Standards Association of Australia (SAA) in 1988. Other changes were made, and the organization was incorporated as Standards Australia International in 1999. SAI generates revenues through normal business activities and government-funded contributions to the national interest. It makes innovative use of the Web to develop and distribute intellectual property. Through a large number of technical committees, a staff of almost 300, and thousands of voluntary experts, SAI maintains over 6000 standards. Standards Council of Canada SCC. The Standards Council of Canada is a Federal Crown corporation responsible for promoting efficient and effective voluntary standards in Canada for the health, welfare, and economy of Canada. The SCC works in cooperation with, and manages, the National Standards System. The SCC coordinates input from the SCC to the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). See Canadian Standards Association, Telecommunications Standards Advisory Council of Canada. http://www.scc.ca/ standards reference model A communications framework for describing and classifying information processing standards by the Institute of Electrical and

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Electronics Engineers, Inc. (IEEE). Within the reference model, general sets of requirements are developed. The reference model divides standards into two categories: Interface Type

Notes

application program Standards which influence application portability by describing and defining interoperability between applications software and the computer operating system. Consideration is given to systems, communications, information, and humancomputer interactions. platform external Standards which influence system portability and interoperability, that is, the behavior of information processes which interact with their external environment. Data portability and user interfaces are important considerations.

Conformance to these standardization concepts provides a framework for vendors to develop and distribute products and services compatible with those of other vendors, and provides users with some assurance that products purchased from different vendors will work together. standby processor A spare or secondary processor in a computer system, which is ready to take over if there are problems with the first, or if extra computing power is needed on an irregular basis. The standby processor is usually a hot standby device, that is, it can come online without turning the system off or interrupting its functioning to a substantial degree. Sometimes the second processor is not idle, but is used for less intensive computing operations, while still remaining ready if it needs to come online as a substitute for the main processor. In some cases, the standby processor does low-level maintenance work on updating its databases and file structures, so that if the primary processor goes offline, the file information is known by the standby processor. Standby processors are most commonly used in highend systems that require a high degree of reliability. Examples would include medical or navigational applications where people’s lives might be in danger if there were a processor failure. standby time 1. A power-saving feature built into many consumer electronics. Camcorders, calculators, laptop computers, and various other devices that rely on limited battery power will often have timing mechanisms that monitor idle time, that is, time during which the device receives no input from the user. When the idle time expires, the device is powered down or put in a minimal power-consuming mode, in order to save battery life. 2. The amount of time a fully charged battery-powered unit can remain on

before the battery runs out. This applies to many devices, including cell phones, cordless phones, shortrange radios, laptop computers, etc. Standby time is often used as a marketing statistic to characterize a system and generally refers to idle time, rather than time during which the item is used. The use time (or talk time on a cell phone) is typically less if many features are used. standing wave A phrase which is used to describe physical relationships and movements in real life as well as diagrammatic representations on display systems such as computers and oscilloscopes. Very large standing wave patterns are described by astronomers when talking about the movement, relationships, and symmetry of galaxies. standing wave ratio SWR. A diagnostic measurement of a standing wave which is commonly used in transmitter and transmission line testing and maintenance. When cables are affected by moisture, wear, and loose connections, an impedance mismatch may occur which can be detected through the amplitude ratio of a standing wave. The transmitted wave is used as the signal source for measurement by an inline SWR meter. Stanford Artificial Intelligence Laboratory SAIL. This research laboratory is the source of many pioneer ideas and developments in artificial intelligence and general concepts related to computers. SAIL contributed to the development of the LISP programming language. The SAIL facility also developed the SAIL programming language, an ALGOL-like language created in the early 1970s. The SAIL facility was closed down in 1990. Stanley, William An inventor who created the first practical alternating current generator, after it was pioneered by Elihu Thomson. Thus, the first Stanley alternating current (AC) distribution system came into being in 1885, 3 years after Thomas Edison opened the first direct current (DC) power utility company. In conjunction with Elihu Thomson and Sebastian de Ferranti, Stanley also developed the transformer. See Alexanderson alternator. STAR TAP The Science, Technology, and Research Transit Access Point. This is a persistent communications infrastructure project funded largely by the National Science Foundation to facilitate the operation and interconnection of advanced international networking systems. It supports applications, performance measurement, and technology evaluation, and facilitates the flow of network traffic to international collaborators. The project is managed at the University of Illinois Electronic Visualization Laboratory. See STAR TAP International Advisory Committee. http://startap.net/ STAR TAP International Advisory Committee A committee of international member groups connected to STAR TAP or interested in joining STAR TAP which oversees STAR TAP policies and operations. Members are affiliated with a wide variety of organizations including CERN, SURFnet, TransPAC, iCAIR, and Euro-Link. See STAR TAP. star topology A common type of network topology in which remote systems and nodes are connected

point-to-point to a central system, and not to one another. Unlike some topologies with redundant connections, if the central system on a star network fails, the entire network is unable to intercommunicate. One advantage is that problems are easier to isolate, another is centralized administration and security. A star system provides the option of physically isolating the server from unauthorized access. Star topologies are used in many phone and data networks. See hub, topology. Stark effect An effect observed and described by Johannes Stark, in 1913, following several years of research into Doppler effects in rays . He observed the application of an electric field could induce the splitting of spectral lines when he was studying the spectrum of hydrogen. Further investigation indicated that the spectra decomposed into several components, some of which were linearly polarized through the influence of a strong electric field and that this effect could be observed in substances other than hydrogen. Thus, at the atomic level, it appeared that the influence of an electrical field produced different results from that of a magnetic field. See Zeeman effect. Stark, Johannes (1874-1957) A German researcher who studied the influence of electrical fields on spectral lines. Stark was awarded the Nobel Prize in physics in 1919 for his discovery of the Doppler

effect in certain rays and of the distortion properties of an electrical field on spectral lines. See Stark effect. start pulse In a start-stop teletypewriter system, a mechanism to release the receiving line relay and permit the receiving arm to move. start-stop synchronization A method developed by Howard L. Krum for use with permutation code telegraph systems. stateful packet filtering SPF. Packet filtering is a security and traffic management technique used in packet-based networks to selectively control network traffic based on information contained in packet headers. Many routers are equipped to support packet filtering. Dynamic packet filtering is a means of dynamically handling the traffic management after a stream of packets has passed through, to minimize the number of security gaps that might be left open by static packet filtering. Stateful packet filtering is a form of dynamic packet filtering that applies protocol-specific filtering rules and monitors state and context information associated with a network session. This may, in some cases, improve security (or appear to improve security), while still having some limitations and drawbacks associated with direct connections to internal hosts and no direct user authentication. See spoofing. static n. 1. In radio transceivers or phone systems,

discharging rods conducting rods with brushes collecting forks revolving glass plates drive wheel Leyden jar

This excellent example of a static generating machine mounted on a base with Leyden jar condensors on either side is on exhibit in the American Radio Museum.

discharging rods revolving glass plates Leyden jar

This schematic diagram shows the basic components of a static generator which functions essentially the same as the one shown in the photo above. A Leyden jar is positioned at each side, with the revolving plates in the center. The discharge rods are shown across the top.

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static (also called atmospheric) is noise resulting from weather phenomena and related atmospheric electrical charges. Proper grounding can help reduce static interference. See interference, noise. static declaration In programming, a static property, as might be associated with a variable, is one which is established prior to execution of a program. static electricity An electrical charge at rest, familiar to many people as static electricity. Static electricity associated with rubbing amber (amber in Greek is elektron) was known to the Greeks by at least 600 B.C. when Thales recorded that a “fossilized vegetable rosin” (amber), when rubbed with silk, acquired the property to attract very light objects to itself. See mutual capacitance. static generator An early experimental device used to investigate static electricity and its effects. Static generators still are valuable as educational tools. See static, Van de Graaf generator. static object A software term for an unchanging or uneditable object in an application or document. Images are often embedded as static objects in word processed documents, and can only be edited by locating the source document, changing it in the original context, and updating the static location (or reinserting it into the document as a static or dynamic object). Contrast with linked object. static RAM SRAM. A type of fast electronic random access memory chip which is often used in computers in conjunction with dynamic RAM (DRAM) as they have different characteristics. Unlike DRAM chips, SRAMs do not need to be refreshed while in operation, thus providing fast access. As with many other types of memory chips, they require power to retain their information. See dynamic RAM. static route A data transmissions path that is fixed and stored in a table or other form of database in a network router or high-end switcher (the distinction between routers and switchers is not as great as it used to be). Static routing is often faster than dynamic routing, but is not suitable for all types of installations. Static routing works well in small systems or those in which the routes are fixed and known, whereas dynamic routing is suitable for large, changing, distributed networks. station A phone, computer, or other telecommunications device service office, console, or workstation. station battery A battery used in early telephone switching stations which commonly provided 48V direct current (DC). station clock A centralized timing clock which provides a local reference for broadcast or other telecommunications functions carried on at that station. Timing information may be actively transmitted from the station clock to other equipment. In broadcast stations in North America, the idiosyncrasies of black and white TV caused discrepancies in playback speeds of different media, even though they might use the same time-code basis. Thus, the playing time of a broadcast may be considered compensated when it has to be adjusted to match the station clock. In networks, internal clocks and station clocks are

used to provide timing information. In very precise timing situations, such as in astronomical observatories, cesium-beam station clocks may be used for timing purposes. stationnaires French semaphore operators in the late 1700s and 1800s. STE 1. See Section Terminating Equipment. 2. Station Terminal Equipment. 3. Spanning Tree Explorer. steady mark condition With multiple telegraph keys arranged in series, when not sending, an operator would close a switch to short the key contacts in order to leave the series unbroken. It puts the idle line into a steady mark condition. stealth Secretive or furtive action or application. In computing, stealth products or processes intended to be active without detection, such as a viewing portal or recording system that allows people or processes to be monitored without their knowledge. Accounting, audit, or job performance applications are sometimes run in stealth mode. System operators often run stealth processes to monitor regular or unauthorized activities on computer networks or individual machines. Hackers use stealth measures to break into computer systems or to investigate processes or switching systems. stealth server In distributed networks using domain name systems, a stealth server is similar to a slave server in that it is an authoritative server, but differs in that it is not identified in the name server’s register and thus would be visible to other servers only if explicitly known by a static identifier. See slave server. Stearns, Joseph B. (?-1895) An American inventor who designed and built Norumbega castle in 1886 near Penobscot Bay, Maine. He invented important aspects of duplex telegraphy that were patented in 1872 (U.S. #126,847 and #132,933). Stearns’ system was initially used on the Franklin Telegraph Company lines and later on the Western Union lines. He sold the rights to duplex telegraphy to Western Union. Thomas Edison later extended the concept to create a quadruplex system in which two communications could be sent in two directions at the same time. There are some brief references that a J. Fisher may have introduced duplex telegraphy even earlier, but the author was unable to find any solid documentation to confirm this. Documents such as Stearns’ Western Union membership cards and the Stearns patents of 1872 to 1874 (and reissued patents of 1880 to 1882) are in the Western Union Telegraph Company Collection, 1848-1963. See Frischen, Carl; Gintl, Julius; duplex telegraphy. Steinheil, Karl (Carl) August von (1801-1870) An astronomer and inventor (and associate of Gauss) who experimented with an Earth conductivity method to send wireless communications over distance in the 1830s. Steinheil was born in Elsass, but settled in Munich, Germany. With Gauss, he proposed the use of rail lines as a conduit for returning electrical signals. Steinheil developed a magnetic recording telegraph that marked high and low dots on a ribbon of paper (very similar in concept to Vail’s

code used on the Morse telegraph a few years later). In 1836, he contributed to the development of standards for measurement. In 1839, he pioneered electric clocks and reported some of his telegraphic discoveries in Annals of Electricity, Magnetism, and Chemistry. Ten years later he was involved in the organization of telegraphic communications in Austria. He is also known for inventing optical technologies. See conductivity method. See Sömmering, Samuel Thomas. Steinmetz, Charles Proteus (1865-1923) A German-born American electrical engineer acknowledged for his genius in the investigations of lightning, alternating current phenomena, magnetism, and other discoveries which led to the development of safer power distribution systems and better motors, generators, and electrical appliances. step bolt A bolt or large rivet or smaller bolt or rivet supporting a rung, intended to assist a climber in finding footing while climbing, as in a high-voltage line supporting tower. As towers age, the bolts tend to rust or even disappear altogether, causing risk to the climber, unless the bolts are maintained and replaced when needed. Tower maintenance workers are cautioned to place their gloved hands on the side supporting structures rather than on the step bolts, in case of a slip or fall. step-by-step switch An early electromechanical automatic telephone switching system developed in 1920 and quickly favored by independents. It used rotating blades for setting switching connections. In competition with this, AT&T developed the first commercial panel switch in 1921. This type of switch was widely used until the mid-1970s, when crossbar switches superseded most panel switches and many step-by-step switches. Step-by-step switches must be modified to support touchtone dialing. See Callender switch, crossbar switch, Lorimer switch, panel switch. stepdown transformer A power transformer that provides voltage conversion from a higher to a lower level. This type of system is commonly seen on utility poles carrying primary power to secondary power users and individual drop points. Stibitz Complex Number Calculator The first relay calculator, released in 1939, developed at Bell Laboratories. Stibitz, George R. (1904-1995) An American mathematician and researcher at Bell Telephone Laboratories who developed relay arithmetic devices in the mid-1930s. Stibitz began to study binary circuits and the various applications of binary systems. This led to Stibitz’s subsequent development, in collaboration with Samuel B. Williams, of an electromagnetic relay calculator, the Complex Number Calculator, which could manipulate complex numbers. By 1940, this machine had become the Bell Labs Model 1 and was incorporated into the telephone network in such a way that it could be remotely accessed, setting an early precedence for future network systems. Stibitz thereafter served as a consultant to the U.S. Office of Scientific Research and Development. Stibitz’ continued interest in calculating machines and

computers led to the awarding of a patent for a computing system that was a forerunner of modern digital computers, in February 1954 (U.S. #2,668,661). In 1997, the American Computer Museum launched an annual award to honor living pioneers of the computer and information age and named it in honor of George R. Stibitz. STL 1. Standard Telegraph Level. 2. Studio-toTransmitter Link. stock ticker A type of early stock reporting machine, somewhat resembling an anniversary clock with mechanical parts within a glass globe on a round base. This machine used a paper tape and telegraphic line hookup to provide fast reporting of stock activities with alphanumeric characters. In many ways the stock ticking machine is the ancestor to asynchronous telecommunications. Stoke’s shift A loss of energy during an excited state of an electron where internal forces bring the excited electron to the first level singlet. In observations of fluorescence, the difference between the peak excitation wavelengths and the emission wavelengths. The concept of the Stoke’s shift is important in a number of fields related to telecommunications, including spectroscopy. In fiber optics, it applies to shifts that occur in doped in-fiber amplification technologies that help overcome signal loss through attenuation. See Stoke’s theorem.

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Stepdown transformers are common components of utility poles carrying primary power between substations (upper) and secondary power for residential/ small business subscribers (lower). Here the connections are shown between the higher-voltage conductors on the crossarms to the three transformers attached with brackets to the pole to the conducting line for the secondary power fed via connecting lines to the adjacent buildings. [Classic Concepts photo.]

Stoke’s theorem A theorem pertaining to vector calculus that describes a relationship between surface integrals over an open, spatially oriented three-dimensional surface and closed line integrals along the contour bounding the surface. It enables surface integrals to be mathematically reduced to line integrals and vice versa. This is useful for analyzing vector fields in electromagnetics. It is related to Green’s theorem, which provides relationships between closed path line integrals and plane integrals for curves lying in a two-dimensional plane. Stoll, Clifford (1950- ) Author of A Cuckoo’s Egg (1989), an account of computer espionage by foreign infiltrators as experienced by Stoll, who was determined to track down the source of a tiny, but puzzling accounting error, and found much more. This account of remote hacking was only the tip of the iceberg in terms of what was subsequently learned about computer penetration into unauthorized systems, computer theft, and fraud and thus has become a classic nonfiction techie thriller. In his second book Silicon Snake Oil, Stoll takes a step back and looks at the pros and cons of digital technologies and how they have affected our world. Stoner, Don (ca. 1932-1999) An American electronics experimenter and amateur radio enthusiast who, in 1957, suggested the amateur construction of a relay satellite capable of two-way communications. This idea was in advance of its time, preceding the widespread use of electronic transistors and the construction of government two-way communications satellites, and inspired the development of the OSCAR satellites. Stoner wrote about his ideas for amateur radio space research in QST in 1961. In 1971, along with Pierre Goral, Stoner formed Stoner-Goral Communications (SGC) to sell radio equipment, 70% of which is not exported outside the U.S. Stoner retired in 1989 but continued to pursue the advancement of amateur radio until his death. He was editor for a time of CQ magazine and founder and head, for a time, of the National Amateur Radio Association. His call sign was W6TNS. storage area network SAN. A somewhat catchall descriptive phrase for new models for handling large amounts of data stored on a variety of types of media, accessed by a variety of remote users on a network. The model of a single hard drive and floppy drive on a dedicated workstation is impractical for heterogenous, high-capacity storage; high-demand storage needs on evolving local area and distributed public networks. A SAN is a general effort to efficiently organize, administer, and evolve storage solutions for heterogenous network environments. This more general concept is distinct from network access storage (NAS), which implies the consolidation of network storage resources. SAN is a broader concept, encompassing many different types of solutions for handling storage devices and data-need dynamics. SAN is also used as a more narrowly defined term by commercial vendors to describe storage devices specifically optimized for use on distributed networks. See network-attached storage.

storage cell, accumulator A secondary source of electricity, since it does not provide power immediately, but rather is charged up and then used. Car batteries are typically lead-acid storage cells that derive their power from a generator when the car is running, then store the power for later starting of the vehicle or operation of its electrical system when the motor is not running. See solar cell.

This zinc-lead storage battery was introduced by the United States Battery Company in 1900. It featured high voltage in a small size. The amalgamated coiled plate is zinc, fitting within a glass container. The lead is formed into suspended spongy, superposed peroxide plates. [Scientific American, April 7, 1900.]

store-and-forward A technique for temporarily holding information until the conditions are right for transmitting the data to the receiver. This method is very common on data networks, where a router, local network, or individual machine may be offline or down. The data may be held indefinitely and transmitted when conditions are right (the right time, when traffic is lower, when the recipient is online, etc.), or may be bounced back to the sender after a certain interval or number of tries. It may even be abandoned, depending upon its nature and priority level. store-and-forward repeaters Transmission devices that store and forward information when conditions are favorable. In radio receiving and transmitting stations, both Earth and satellite stations, the conditions for transmitting a received signal may not be optimal right away, due to weather, political unrest, high traffic levels, or the movement of a satellite out of transmissions range. The message is thus not sent until conditions improve or the satellite comes into a favorable position in orbit. Storey, G. J. A scientist who first used the term electron, in 1891, to specifically describe an electric charge. Storrer insulator A type of early utility pole insulator patented by L. W. Storrer in 1906, and first shipped by the Brookfield Glass Company in 1909.

See insulator, utility pole. STP 1. shielded twisted pair. 2. See Signal Transfer Point. See Signaling System 7. 3. Spanning Tree Protocol. STPC 6800 An early Motorola MC6800-based computer kit from Southwest Technical Products Corporation. It featured 2048 bytes of static memory, a serial interface, case, and cover. The STPC was available in the fall of 1975, and sold for $450 without a monitor or keyboard. See Altair 680, SPHERE System. strain insulator, link strain insulator A historic utility pole insulator that French inventor C. Priestley submitted for a patent in 1910. The Ohio Brass company acquired the rights and the patent was granted in 1912. It was in production, with variations, for about 30 years. This is also known as a hog or pork liver insulator due to the brown or tan coloring and the blobby dimpled saddle shape that allowed the conductive line to be fed through a channel connecting the dimples. The dimple channel configuration provided some protection in case the insulator broke, as it could still hold the cable. See saucer insulator, suspension insulator. strand A single long thread of uninsulated wire. When two or more of these strands are combined or twisted around one another in the same bundle, it is called stranded wire. Wire is stranded for a number of reasons; it can make it more flexible and it may alter the electrical characteristics of the wire for some particular purpose. StrataCom A commercial supplier of ATM-related telephone networking products, particularly Frame Relay switching systems and network management control software based on open, standards-based interfaces for integrating with other vendors’ products. Stream Control Transmission Protocol SCTP. A reliable network transport protocol designed to transport public switched telephone network (PSTN) signaling messages over Internet Protocol (IP) networks. SCTP was submitted as a Standards Track RFC by Stewart et al. in October 2000. SCTP operates over connectionless packet networks such as IP. It is modeled as a layer between the SCTP user application and a connectionless packet network service in the context of an association between two SCTP endpoints. See RFC 2960. stream protocol See byte-stream protocol. street price The price paid for a product after shopping around, as opposed to suggested list or suggested retail, the price the wholesaler or manufacturer has designated for the product, which is usually higher due to dealer discounts. The suggested list price is often imprinted on the product packaging and overlaid with a lower dealer price. The street price may equal the dealer’s price or may be a commonly negotiated price that is discounted even further. In other words, through discounts, volume deals, and competitive pricing, dealers often offer a street price much lower than the list price. The street price may also be higher than list price. For example, a ticket for a popular rock concert sold by street hawkers an hour before showtime may have a street

price that is two to ten times the original ticket price (the “scalped” price). stringed insulators Electrical insulating objects mounted in multiples in order to increase the spacing distance to what is needed between a conducting line and its supporting structure. Higher voltage lines mounted overhead on utility poles or high voltage towers tend to require a longer string of insulators that can be directed away from the pole or cross arm. The insulators are commonly strung in single rows or in a “V” configuration. Depending upon their configuration and the number of strings, it may be difficult to access and maintain stringed wires from cherry picker (bucket) maintenance vehicles. Climbers manually scaling utility poles with strung insulators must also be careful not to move within the minimum air distance (MAD) arcing zone, which is especially tight in V configurations. The arcing zone is related to the length of the insulating string. See suspension insulator. stringing The process of running wire or cable, especially as applied to stringing utility wires along outdoor utility poles. stringing block See stringing roller. stringing rope A narrow-gauge rope used to help string lines through narrow walls, conduits, or stringing rollers. It is also called a pilot rope or pulling rope. The end of the line to be installed will be attached to the stringing rope and then pulled through the narrow channel. For example,when threading a line up through the narrow vertical space in a wall from one floor to another, the stringing rope may be passed down from above, the line attached, and then the stringing rope pulled up again to feed or pilot the line through the wall or through a conduit pipe installed in the wall. If the stringing rope is used for above-ground utility line installation, the rope is used to pull conductive line through stringing rollers, over the track provided by the stringing sheaves that are the main part of the roller assembly. See stringing roller, stringing sock. stringing roller A device with a rolling indented wheel attachment called a sheave that facilitates stringing wires and cables by enabling the pulled cable to run smoothly along the track supplied by the rotating roller. Stringing rollers also often have various types of hooks or eye sockets for mounting or attachment. Stringing rollers are commonly designed so that they can be mounted on utility pole crossarms or on vertical or horizontal insulators. Stringing rollers for outdoor use are typically made of materials that resist corrosion such as stainless steel and aluminum alloys. They may also have neoprene liners. When attached to crossarms or insulators on outdoor utility poles, a stringing roller may require an additional crossarm or insulator adaptor. A universal stringing roller is a multipurpose roller designed with a number of fittings and adaptors for mounting it in various positions on various types of supports. This type of roller may also need an additional adapter when mounted on crossarms. A universal roller makes it possible to purchase mass quantities, even if they are used for

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different types of lines and mounting surfaces. A distribution roller is a type of stringing roller intended to support multiple conductors. The roller is wider than a single stringing roller, with two or more side-by-side grooves to keep the conducting lines separated from one another as they pass over the roller. The distribution roller aids in managing multiple line support with a minimum of equipment and space. A boom truck roller is a specialized type of stringing roller for temporary lifting and support of hot (electrically live) lines during maintenance, repair, or rearrangement. It can be mounted on a crossarm or insulated boom, as needed, and removed after the work is complete. Stringing rollers are also called stringing blocks (as in block and tackle). They are generally sold with load ratings to support different types and gauges of wires and cables. There are occupational regulations on the stringing of conductive lines. For example, under OSHA regulations, if a conductor or pulling line is pulled by an automated device, the lineworker is not permitted to be directly under the roller or on the crossarm, except as is necessary to guide a stringing sock through the stringing roller’s sheave. See sheave. stringing sock A device used with a stringing rope to enable it to attach to and pull multiple conductive lines through piloting by a single stringing line. It is sometimes also called a stringing board, depending upon its design. stringing tool A tool designed to enable a single utility pole lineworker to transfer the conductive line from a stringing roller to a clamp (preferably onehanded) in such a way that the roller doesn’t have to be removed. See stringing roller. stripped insulator A conductive line insulator, as on a utility pole or tower, that has had the protrusions broken off, usually the outer skirt. This may happen as a result of aging, lightning strikes, or vandalism (e.g., target practice). stripping, image assembly In traditional page layout and printing, the process of positioning page composites, in the form of negatives or positives, on a flat in preparation for creating the printing plate. strobe n. 1. High speed intermittent illumination. 2. Older term for an electronic flash. 3. In asynchronous communication, input of parallel data to a register or counter. 4. A momentary intensified sweep of a beam on, for instance, a scope. 5. On a computer bus, strobe lines indicate when data are being transferred. Stromberg-Carlson Telephone Manufacturing Company Founded in 1894 by Alfred Stromberg and Androv Carlson, who took advantage of the opportunity created by the expiration of the Bell patents to establish a competing phone company. Within 20 years, Stromberg-Carlson had become a leading independent telephone company. After acquisition by the Home Telephone Company, it moved to New York in 1904. During World War I, the company supplied communications equipment to the military.

The company subsequently introduced new materials into telephone construction, including Bakelite, a type of hard plastic. Around this time, the company was involved in consumer radio products and broadcasting, as well. It was FRC-licensed out of Rochester, New York, to operate station WHAM .

A June 1894 patent illustration for the StrombergCarlson telephone switch.

A number of innovators in telephone technology worked for the company in the 1930s and 1940s, notably Andrew W. Vincent, who left in 1946 to develop an improved dial telephone system. As television technology evolved, the company provided consumer TV sets, many of which are now collector’s items. In 1955, Stromberg-Carlson was merged into General Dynamics, a major defense contractor and, in 1984, was acquired by Comdial Corporation, which remains committed to telecommunications products. Stroud, William A Canadian printer and inventor who developed new ways to print entire projects as a single run through a printing press, rather than as separate sections, as had been done prior to this time. His work resulted in a new type of belt press and he unveiled the Stroud, Bridgeman press in 1959. Strowger, Almon B. An American mortician and

inventor who created the first commercial automatic telephone switching system, a step-by-step switch patented in 1889, and dial-switch patented in 1891. This system allowed a subscriber to dial-connect a local call without going through a human operator. The first Strowger exchange was established in Indiana in 1892. Strowger cofounded Automatic Electric in 1901, the largest telephone equipment manufacturer servicing Bell’s competitors, the independent telephone companies. This was a successful fit, since Bell was creating its own switching technology, such as the panel switch, in competition with Strowger’s technology; also, the Strowger switch was somewhat unmanageable in large installations, a limitation that was only a minor problem when the majority of Automatic Electric’s customer base was small independent telephone companies. See Callender, Romaine; Lorimer, George and James; Strowger switch. Strowger switch The first automatic telephone switch put into commercial service, in Indiana, patented in 1889 by Almon B. Strowger. Thus, direct dialing was born, and a human switchboard operator was no longer needed for connecting local calls. This also promoted a small revolution in phone design, since now dials were needed for callers to dial their own calls. The Strowger technology was further developed and put into service by the Automatic Electric company, cofounded by Strowger and directed by Alexander E. Keith. Surprisingly, the Bell system did not adopt the Strowger system until 20 years after its introduction. See Callender switch, Lorimer switch, panel switch, step-by-step switch.

A Stromberg-Carlson Receiver marketed to those who appreciated high-quality sound reproduction in the 1920s. By shielding radio frequency circuits in a process called “rejectivity,” Stromberg-Carlson promised listeners higher sound fidelity. [Talking Machine World, 1926; copyright expired by date.]

Structure of Management Information A standard for object naming and describing mechanisms for the purpose of network management. See RFC 1155.

STS See shared tenant services. STSK Scandinavian Committee for Satellite Telecommunications. STU Secure Telephone Unit. A telephone designed to include cryptographic protection for voice, data, and fax transmissions. STU-3 Secure Telephone Unit 3. A secure telephone unit used for government communications. See STU. stump cam See cam, stump. STUN serial tunnel. Sturgeon, William Credited with producing the first electromagnet in 1823. SU subscriber unit. The device or system at the end of a circuit. This may be a phone, handset, or computer terminal. Submarine Telegraph Company A pioneer London-based underwater cable-laying firm known for some of the earliest marine telegraph cable installations. It was descended from the English Channel Submarine Telegraph Company founded by the brothers Brett in 1847. Using lead to weigh down the cable, an initial cable was installed between England and France in August 1850. However, cable capacitance was not fully understood at the time and the transmission was poor and of little use. In addition to this, the problem of boat anchors in the relatively shallow strait resulted in the cable being severed. The company reformed into the Submarine Telegraph Company and a new deadline for connecting France to the British Isles was established. In September 1851, the company laid a functional underwater cable between Dover, England, and Calais, France. Over the next decade, it installed additional cables, totaling almost 900 miles of communications links. The success of these historic cable installations was based in part upon the use of guttapercha as an insulating material for preventing salt water corrosion to sealed transmission lines. In 1863, Cyrus Field, the promoter for the first successful transatlantic cable, contacted the company regarding the duration of their cables, to which John W. Brett responded with details as to their duration, extent, and locations. See Field, Cyrus West. Subnetwork Access Protocol SNAP. An evolution of the Logical Link Control (LLC) method, with backward compatibility with Ethernet, which facilitates communication of entities at a given network layer. SNAP was developed by IEEE to support multiple-standard, public and private Network Layer protocols. SNAP expanded 8-bit SAP space to 40bit (5 byte) protocol ID, and uses the first 5 bytes in the LLC Protocol Data Unit (PDU). SNAP supports more upper-layer protocols than previous methods. It also allows Ethernet protocol type numbers to be used in IEEE 802 frames, to provide easy translation between Ethernet and IEEE 802 frames. subscriber loop The circuit between the telephone company’s central office and the subscriber station. In earlier times, the subscriber station extended all the way to the phone, but more recently this demarcation point has been changed to the service box outside or inside the premises to which the interior wiring usually attaches. It’s still possible to get

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service right to the telephone; it just costs more. Subscriber Network Interface SNI. One of the two interface ports of XA-SMDS systems used to connect an end user to the SMDS network. The other interface is the Intercarrier Interface (ICI). See Exchange Access SMDS. substation A facility or piece of equipment that offers less in some way than a main station within a network of stations. In other words, it may have a smaller physical size, lower capacity, fewer units, a smaller staff, lower priority, etc. In electrical facilities, a substation is a high-voltage electrical switching facility used to supply lines, circuits, and generators within a larger system. The substation may serve a local community, act as a relay station, and convert voltages from one level to another or from one type to another (e.g., AC to DC). Electrical substations are common in the industrial landscape. They usually have high fences, safety standoffs, and signs to warn the public of the dangers of injury or death from electrical shocks. In multiple phone systems, a substation is a phone console that is subordinate to the main console. It typically has more limited buttons, features, or callout capabilities than the main console. In cases where the substation has the same capabilities as the main console, the distinction is based more on where the call is initially directed (to the main console), with the substation only receiving the call when it has been redirected from the main console or another substation.

substrate-incident recording SIR. A recording mechanism used in standard magneto-optical recording in which a transparent substrate is laid down over the recording layer. The laser light aimed at the recorded layer when it is being read passes through the substrate. The substrate helps protect the recording layer from fingers, abrasions, oxidation, dust, etc. that would interfere with the recorded data. This substrate makes it possible for media like CDs to be picked up and moved around, in contrast to hard drives, in which the recording surface cannot be touched or moved without damaging the media. The substrate coating on optical discs has some disadvantages as well. Because the laser light must pass through an extra layer, there is a limit to the size, at the lower end of the scale, which can be used, thus limiting the resolution of the disc in terms of data density per unit area. Contrast with air-incident recording. See overcoat-incident recording. SUMAC SuperHIPPI Media Access Controller. See HIPPI-6400. Sun Microsystems Computer Company SMCC. A California hardware and software manufacturer established in 1982, Sun’s computer systems are commonly found in higher educational institutions, scientific research and medical imaging applications, and as servers for local area networks (LANs) in corporations, educational institutions, and Internet Services Provider (ISP) premises. Many of Sun’s products are aimed at telecommunications applications for voice and data. The company’s products cover a wide range from desktop systems to high-end re-

This historic schematic diagram shows the layout of a basic telephone common battery system with two subscriber lines in contact with one another through a manually operated cordboard switchboard.

search and supercomputing systems. The SunOS and Solaris operating systems are well known. In 1996, Sun acquired Integrated Micro Products (IMP), including their fault-tolerant computer specifically targeted to the telecommunications industry, and Cray Research’s high-end server system. Sun’s JavaSoft is the developer of the well-known Java object-oriented, platform-independent, general purpose programming language. JavaSoft collaborated with Lucent Technologies to develop a Java telephony application programming interface as part of a series of Java Media APIs to provide an open framework for Java applications development. Sun Microsystems Inc. and Motorola Inc.’s Multimedia Group joined forces to develop products for cable operators to deliver high-speed data communications and Internet access to the home through Motorola’s CyberSURFR™ cable modem. Sun’s XTL Teleservices for Solaris is a set of telephony software services and open application programming interfaces that extend Solaris LIVE, an integrated multimedia environment. SunXTL A teleservices product delivery vehicle developed by Sun Microsystems, known as Sun XTL Teleservices Platform for Solaris. SunXTL provides Teleservices development support for applications intended to run on personal workstations. The types of teleservices which can be implemented with this technology include integrated voice mail, answering machine, automated dialing, faxing, etc. Because these are generated within the computing environment, they can be integrated with input and output from word processors, address books, databases, and spreadsheets. SunXTL is a foundation library for telecommunications-related applications, which includes call control functions, data stream access methods, and data flow control. SunXTL API A SunXTL Teleservices object-oriented applications programming interface which facilitates development of personal desktop applications with C++, including on-screen phone graphical user interfaces, remote workstation access, personal voice mail, etc. for telephony hardware peripherals. SunXTL Call Objects The SunXTL API provides developers with C++ XtlCall objects to control various aspects of a telephone call, including querying the call state and the numbers associated with the call, the call’s current status, and its data type or media class. It can also request a change in call state. The XtlCall objects also have callback methods for the asynchronous notification of state changes. SunXTL Provider Configuration Database The SunXTL Teleservices configuration database is a repository for installed providers. The database provides information on each provider and how to invoke it, and lists its characteristics and capabilities. The database describes telephony resources such as available bandwidth, number of available lines, types of voice services available, etc. A graphical user interface (GUI) tool xtltool is provided for browsing and editing the Provider Configuration Database. SunXTL Provider Interface A SunXTL Teleservices

open interface providing third-party developers and Independent Hardware Vendors (IHVs) with a way to use the Provider library to ensure compatibility and compliance with basic system protocols. This message set can be extended with user-specific features. The provider interface fits between the server and/or datastream multiplexer and the various drivers. SunXTL Provider Library A SunXTL Teleservices library which works with the Provider Interface to keep the Provider information distinct from system services. The library provides interfaces to various data streams and services, including the Provider database and various server functions. SunXTL Server The SunXTL Teleservices server provides administration, message passing, and security to networked personal workstations running SunXTL Teleservices applications. SunXTL System Services The SunXTL Teleservices System Services provide an intermediary between the application view of a call object and the provider’s implementation of the call. Interprocess message passing, object identification and creation, call ownership, and security are handled by the server. Super DLTtape SDLT. A tape data format developed by the Quantum DLTtape Group that provides reliable high-capacity storage at good transfer rates. The format is competitive with the linear tape-open (LTO) format. Search and data rate speeds are similar, with LTO slightly faster and SDLT with slightly higher capacity (currently about 10% more). SDLT is based upon magneto-resistive heads densely packed into clusters that are joined in an advanced thin-film medium, resulting in higher capacity and faster transfer rates than traditional magneto-resistive technologies. Advanced Metal Powder (AMP) materials enable small, smoothly coated particles with higher densities to be packed into the medium. In addition to the physical properties of the technology, SDLT uses partial response/maximum likelihood (PRML) data-handling techniques, further increasing capacity and performance. Developers have mapped out four generations of SDLT technology with predicted capacities of more than a terabyte of data on a single cartridge: Generation 1 SDLT drives backward-readcompatible with existing DLT products, released in March 2000 and fourth quarter 2001 supporting capacities of 110 and 160 Gbytes at transfer rates of 11 and 16 MBps. Ultra2 and Ultra 160 SCSI, LVD, and HVD interface support. Generation 2 SDLT 640 planned for release in 2003, with backward-read capability, increased capacity, and Ultra320 SCSI and Fibre Channel interface support. Planned capacity of 3200 GBytes at 32 MBps. Generation 3 SDLT 1280 planned for release in 2005, with backward-read capability and the intention to support emerging or prevalent interfaces at the time of release. Planned capacity of 640 GBytes at 50+ MBps.

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Generation 4 SDLT 2400 planned for release in 2006, with backward-read capability and support for prevalent or emerging technologies at time of release. Planned capacity of 1.2 TBytes at 100+ MBps Given the dramatic increases in hard drive capacity in 2001, backup technologies such as tape cartridges have become especially important. See Advanced Metal Powder, linear tape-open, partial response/ maximum likelihood. super group In analog voice phone systems, a hierarchy for multiplexing has been established as a series of standardized increments. See voice group for chart. super server A high end server which consists of a number of computers networked together with communications links that are as fast, nearly as fast, or faster than the processing speed of any one individual computer, so the collection functions as a fast, integrated, distributed, unified entity. With very fast transmissions media and protocols like HIPPI and SuperHIPPI, the distinction between individual machines becomes less critical, and the processing algorithms for carrying out the tasks are more crucial to the concept of the system as an organism. A super server can also be a single machine with multiple CPUs, set up to function together to handle higherend processing requests at faster speeds, or of greater complexity than might be achieved with a typical one-CPU system. A number of interesting distributed processing supercomputing applications have been configured at several U.S. research labs using Linux on personal computers communicating through fast network links. Super Speed Calling A telephony subscriber option, which is essentially the same as Speed Calling in that it allows an abbreviated set of characters to be dialed to invoke a longer number. The distinction is more of a marketing distinction to describe enhanced systems where a name can be entered, which is easier to remember, rather than just a number (usually four digits or characters). See abbreviated dialing. Super Video See S-Video. super video graphics array SVGA. A graphics standard common on IBM and licensed third-party computers, supporting a variety of palettes and resolutions, including 800 x 600; 1,024 x 768; 1,280 x 1,024; 1,600 x 1,200; 1,024 x 768 (16 or 256 colors). See video graphics array. supercomputing A term applied to high-end computing applications provided on the best hardware/ software available at any particular state of the technology. Supercomputers originated sometime in the 1950s, when the viability of computers as a commercial item became apparent. Some of the earliest supercomputers were designed by IBM and shipped in the early 1960s. The supercomputers of 30 years ago had fewer capabilities and were slower than many handheld calculators of today, (they were also much larger in physical size). The definition of supercomputing is

thus a relative one, since most desktop computer systems now are faster and more powerful than mainframes running multiuser networks in many universities and colleges 15 years ago. Supercomputers tend to be characterized by faster (or multiple) CPUs, wider data buses, faster network links, and larger, faster-access storage devices than those available as consumer products. They also may be run with more sophisticated distributed processing algorithms, although writing parallel applications is an art and much research and discovery is yet to be done in this field. Supercomputers tend to be used in scientific research and military applications. superframe In its generic sense, superframe is used to describe a period in time during which a specified number of downstream and upstream frames are transmitted. Thus, the transmission time of a superframe will be related to the bit rate. The concept of the superframe is used in the context of frame timing and alignment. SuperFrame standard SF. A 1969 improvement to the original 1962 DS-1 standard for a frame format for 1.544 Mbps transmissions (2.048 in Europe with 30 channels) which improves the signal-to-noise ratio and combines 12 frames into one SuperFrame. Frames 6 and 12 are used for robbed-bit signaling. This has since been superseded by Extended SuperFrame, which provides increased error detection and removes the need to take down an entire line for servicing. See Extended SuperFrame. superheterodyne receiver An early improvement in radio receivers designed to be more sensitive than radio frequency receivers of the time. The superheterodyne receiver incorporated a signal detector working in conjunction with a local oscillator to mix the signals, producing an intermediate frequency which was then amplified and passed on to a second detector, and from there to the earpiece. The superheterodyne circuit was invented by the “Father of FM,” Edwin Howard Armstrong. See heterodyne. SuperHIPPI See HIPPI-6400. SuperHouse A trademark of BellSouth, to signify a house designed with information services resources built in (conduit, wiring, etc.) to support computing and Internet applications. This is often also referred to as a “smart house” and, in fact, SmartHouse has been trademarked by the National Society of Home Builders. SuperJANET See JANET. superparamagnetic Phenomena which contribute to magnetization and signal decay of magnetically recorded information over time, thus limiting the useful lifespan of magnetic recording media. The density of recording information is related to the superparamagnetic effects as well, resulting in a practical superparamagnetic limit. Studies for arranging magnetic data in particle array systems to study superparamagnetic effects to develop practical schemes and optimize recording density are being carried out at the IBM Research labs. superpose 1. To place or lay over, with or without contact with that which is overlaid. 2. To overlay

upon another such that all like parts of the overlay coincide with the overlaid. superposition principle A principle which can be applied to networked electrical circuits to solve current values in individual branches of the network. See Kirchoff’s laws. Supersparrow A wide area Web server load-balancing system (LBS) distributed as open-source software under a GNU Public License. Supersparrow, based on Border Gateway Protocol (BGP), was developed by Simon Horman and initially released in December 2000. Supersparrow aids in distributing Web access to available servers on the Internet. In many circumstances, users are given the option to select mirror sites that include the same content stored on servers that may be faster or geographically closer to the user. Mirror sites are an especially welcome option to high-traffic primary sites. However, users have traditionally had to select a static mirror site manually from a list of Web links. It’s time-consuming to read the lists and stats and sometimes difficult to determine the most promising option. Often some of the links are unavailable or the addresses out of date. Supersparrow aims to effectively automate the process of utilizing mirror sites using BGP to determine an efficient data path (least-cost path). BGP was selected because it has information on efficient paths to points on the Internet and provides for failure recovery. Unlike the Linux Virtual Server (LVS), Supersparrow does not require a single contact point for incoming traffic. Supersparrow is compatible with VA Linux servers and can accommodate connections to Apache Web servers. See load-balancing system. superstation A television broadcast station whose signal reaches a very wide audience by being retransmitted beyond what would be possible by standard airwaves. The extended viewing area is often reached by a satellite transmission further extended through cable. supertrunk A high-end data transmissions cable system which carries multiple high-bandwidth services such as several video channels. support The provision of additional products, peripherals, or technical expertise to support a customer system or service. In the software industry, technical support for installing and using the software is routinely provided free, or for a fee, from the developer. A small amount of support may also be available from the dealer, depending upon the complexity of the system. Peripheral support for computing products includes repair and replacement of accelerators, upgrade chips, memory expansion interfaces or chips, graphics display controllers, and hard drive controllers. surf colloq. A common term for riding a wave, a technology, a trend, or other force or medium. Crowd-surfing happens at rock concerts when someone is thrown across the top of the crowd and carried hand-to-hand above people’s heads. Traditional wave surfing is catching a large ocean or river wave

with a surfboard, and riding it as far (and well) as can be accomplished. Channel surfing describes a television watcher who uses a remote control device to skim programs from channel to channel, particularly during commercials. This is done with the hope of finding better programming (or as thumb exercises for couch potatoes). Surfing the Net means to travel, in the virtual sense, through the myriad resources and sites on the Internet, especially through the Web, a graphical interface to the Internet. See browser, Internet, World Wide Web. surface-array recording SAR. A process for accessing both sides of an optical disc simultaneously through independent read-write heads on both sides of the disc. By using simultaneous access by the readwrite heads, rather than one or the other at one time, companies like Maxoptix (which has trademarked Surface Array Recording) have realized almost double the transfer rate and disc capacity of previous products. Thus, unlike some previous optical media devices (laserdisc players), users need not flip over the media to read the second side. See air-incident recording, overcoat-incident recording, substrate-incident recording. surge Large, sudden changes in a circuit current or voltage. See burst. surge protector, surge suppressor A device that conditions or filters an electrical current to provide a constant level of power. It is placed where it can provide protection to subsequent devices or components in the system. Ground lines are sometimes used to drain off the surge. Surge protectors may be built into a building’s electrical system to drain off surges from voltage spikes or lightning strikes. For computer systems, a surge protector resembles a fat extension cord and can provide protection from power fluctuations which might damage the electronics. Some limited protection from lightning storms may be possible with a surge protector, but a direct hit will likely damage a simple consumer surge protector and the system to which it is connected. Surge protectors are generally a good idea, especially with laptops which get plugged into a lot of circuits of dubious nature (motel sockets, ferryboat sockets, etc.). suspension insulator A type of high-voltage utility pole insulator patented by F. Locke in 1905. The suspension insulator was supported out and away from the pole or crossarm with wires rather than mounted on the top of the pole or on a crossbar. Sometimes more than one suspension insulator was mounted on a single pole. Historic Locke insulators were rigid fixtures screwed to a porcelain disc. Locke used eye hooks in a later 1910 patent. Locke’s ideas were refined and improved over the years and suspension insulators became an important means to increasing the level of power that could be transmitted across overhead utility poles. There were problems, however; suspension insulators with ceramic or cement cap-and-pin designs were heavy and high maintenance; they tended to deteriorate quickly. Thus, later suspension insulators were simpler, all-metal designs (though still relatively heavy), consisting of a series of spaced

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insulating rings protected by larger arcing rings to protect from electrical surges (e.g., lightning strikes). See strain insulator. sustainable cell rate SCR. In ATM networking, the upper measure of a computed average rate of cell transmission over time. See the Appendix for expanded explanations of ATM. SUT 1. System Under Test. See ATM. 2. Service User Table. A telephone use authorization term. Sutton, Clifford A Canadian film maker attributed with creating the first commercial motion picture in the early 1900s. See motion pictures. SVC See switched virtual connection. SVD simultaneous voice and data. SVGA See Super Video Graphics Array. SVHS, Super VHS, Superior Video Home System A video recording and playback standard introduced in 1987 by JVC for the high-end consumer (prosumer) markets. The format was intended to be less expensive than commercial systems but significantly better quality than the VHS format widespread at the time. SVHS is downwardly compatible with VHS. VHS tapes can be recorded on SVHS systems, but not the reverse, as the image signal differs (audio is handled in the same way as VHS). The SVHS tapes have holes in them to enable record/playback equipment to recognize the cassette as SVHS. SVHS more nearly represents the resolution of television broadcast signals and thus retains the clarity of the image far better than VHS. With a higher initial resolution, SVHS is also more suitable for video editing as each generation tends to lose detail when it is copied. At the time SVHS was introduced, consumer VHS decks were in the $199 to $600 range, whereas SVHS sold in the $500 to $2000 range, a little expensive for the average consumer, but attractive to those with professional aspirations and limited budgets. SVHS is a 1/2-in. tape format that was less expensive than the 3/4-in. formats that dominated the commercial industry at the time of its release and SVHS gradually found a niche, especially with videophiles using desktop video systems such as the NewTek/ Amiga Video Toaster. One of the most popular workhorse SVHS systems for many years was the Panasonic AG1960 and its time-base-correcting (TBC) successor, the AG1970, both of which are still widely used. By 2000, the cost of consumer SVHS decks had dropped to below $200, with TBC-equipped versions selling for under $500. At this point the format became very popular for desktop video and multimedia editing for the Web. Hi-8mm/8mm camcorders that have recently become popular usually have S-Video output ports. See Hi-8mm, S-Video. SVHS-C, Super VHS-Compact A compact (small format) version of SVHS designed to be used in portable devices such as camcorders. The image quality is higher than VHS, but the tape recording times are shorter than a standard cassette. In general, SVHS-C began to be overshadowed by Sony-developed Hi-8mm formats offering the benefits of small

size, high quality, and longer tape recording times. Nevertheless, JVC continues to support and improve upon the SVHS-C product line, introducing digital options such as time-lapse and still shots. Standard 45-minute VHS-C can be used in JVC SVHS-C units. See SVHS. SWAC Standards Western Automatic Computer. A historic large-scale computer, undertaken by the U.S. National Bureau of Standards for its internal use, in the 1940s. It was developed for installation on the West Coast. A similar system was built at the same time for the East Coast. Swiss army knife An indispensable geek tool for anyone who happens to need a screwdriver, pair of scissors, or corkscrew to open up a hard drive, CD-ROM, pizza box, etc. switch n. 1. A mechanical or electrical device that breaks or completes a path in a circuit, or changes the path. See switcher. 2. An electronic circuit designed to carry out a logic operation. New switches have capabilities that were once found only in routers, and some can do switching at the application level (fourth layer). 3. In software, a means to direct a routine; a branch. switch hook See hook switch.

A historic airport switchboard in Washington, D.C., as it looked in 1941. [Library of Congress FSA-OWI collection photo by Jack Delano.]

switchboard In its most general sense, any device into which a number of incoming and outgoing circuits are routed, where the routing of the individual circuit connections can be changed manually, mechanically, or electronically. Human-operated telephone cordboards are probably the most picturesque of the various historic switching boards. The earliest ones required that a foot pedal be pumped to generate the power to ring the

subscriber’s phone. A manual telephone cordboard was often built into a wall, and was hand-connected with simple jacks and cables. In early telephone history, young men were hired to staff switchboards, as women were not permitted to work in most clerical positions, but the arrangement had problems. Some of the male employees were rude to callers, chewed tobacco while talking, and used excessive profanity. As a result, in the mid-1880s, women were hired, and eventually replaced men entirely until the late 1970s when a few male operators re-entered the field. Most male and female switchboard operators are now being replaced by automated switchboard systems with voice recognition and touchtone menu dialing functions. The large panels of switch connections in early cordboards and switchboards have been replaced by multiline phone consoles in many businesses, although some large phone installations or central switching services still have wall panels. Even here, human receptionists are becoming rare, with many small businesses adopting computer voicemail services instead. See Coy switchboard.

area networks, and videoconferencing. This service is gradually being superseded by ISDN services. See DS-0.

A 1961 Bell Telephone long distance switchboard located in Ottawa, Canada. [National Archives of Canada National Film Board of Canada image by Chris Lund.]

This historic cordboard shows the jacks and receptacles which were manually connected. Indicator lights helped operators keep track of calls in progress.

switchboard cable This has two meanings. It was originally a patch cable used in old manual cordboard telephone systems to patch two circuits together to create the end-to-end connection for a phone call. Now that manual switchboards have been replaced by automated switching systems, the switchboard cable is considered to be the one which connects a central office switchboard with an associated automated system, such as a computer. Switched 56 The name of a 56-Kbps switched network voice/data service provided by some local telephone companies which allows calls among several points through one-pair or two-pair copper wires. Switched 56 can be used for voice, file transfers, Internet access, facsimiles, connections to other local

Switched Multi-Megabit Digital Service SMDS. A high-speed wide area networking (WAN), connectionless, packet-switched cell relay transport service based on IEEE 802.6, offered by telephone service providers. It provides capabilities to interconnect LANs (Ethernet, Token-Ring, etc.) and WANs through public switched telephone networks (PSTNs). SMDS can be integrated with transmission technologies such as ISDN, DS-x, and Frame Relay with associated bandwidths ranging from 56 or 64 kbps to 34 Mbps or more. It works with asynchronous, synchronous, and isochronous data and can be used over optical fiber. It can provide congestion control to protocols such as Frame Relay, which don’t have congestion control as an intrinsic part of their specification or implementation. See cyclic reservation multiple access. switched virtual connection, switched virtual circuit SVC. A generic term for a logical communications connection. In ATM systems, there are two types of SVCs: switched virtual path connection (SVPC) and switched virtual channel connection (SVCC). SVC provides on-demand connections between communicating end systems. Using signaling software, the Virtual Path Identifier/Virtual Channel Identifier (VPI/VCI) information will be dynamically allocated to the participating end systems. Switched Voice Service SVS. The standard service offered with FTS2000. See FTS2000. switcher An audio/video component that provides easy reconfiguration of several circuits. In a sense, the button on the receiver that enables selecting

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CD, phono, or tape is a switcher, although the meaning is more often ascribed to a separate component with a number of connectors, inputs, and outputs. See A/B switchbox, switch. switching The three types of switching commonly used in telecommunications networks include message switching, circuit switching, and packet switching. Message switching is a system where the entire message is relayed, intact, through a variety of nodes or service points, from the sender to the recipient. Circuit switching is commonly used in end-to-end direct communications, as in telephone connections. Packet switching involves the segmentation, routing, and reassembly of communications so different parts of the messages may be transmitted at different times and through different routes. While this may not sound very efficient, it is an excellent way to manage data in a large, dynamic, distributed environment, and provides many possibilities for data sharing, representation, authentication, and filtering as desired. The Internet is built on packet switching concepts. See circuit switching, packet switching. switching simulation The simulation on a computer, usually with graphical output, of the circuitry and operations of a switching system. Hayward and Bader did early computer simulations of telephone switching networks in 1955. SWR See standing wave ratio. SXGA super-extended graphics array. symbol A character, icon, or other agreed-on abbreviated representation, useful in representing objects, quantities, languages, arithmetic and logic operations, rules, layout schemes, qualities, sounds, ideas, and others. Examples of symbols include street signs, logos, musical notes, electronics diagram elements, computer buttons and icons, words, punctuation marks, and arithmetic operators. symbolic Representative of something else, or of some greater meaning, usually in an abbreviated form. See symbol. symbolic code A computer code which represents programs in source language, with symbolic names and addresses, in contrast to machine code, which has hardware-specific names and addresses. Use of mnemonic symbols in higher level languages aids in programming and debugging, and symbolic names and addresses can be used to increase portability to other platforms. See assembly language. symbolic debugger An essential software programming and debugging tool used to control and monitor the application under development. A debugger allows you to step through execution of the code, set breakpoints and temporary branches, determine and change the contents of variables, and view the design and functionality of software-in-progress. A symbolic debugger eases the task of finding code segments (many current software applications have tens of thousands and even hundreds of thousands of lines of code) by jumping to a symbol, such as a label name, so that cryptic assembly listings don’t have to be searched. symbolic language A computer programming

language that uses mnemonic symbols, rather than machine code or actual hardware names and addresses, in order to make the process of creating the code more comfortable for humans and easier to read and debug. See symbolic code. symbolic logic A written symbol language developed to express logical and mathematical concepts and arguments in a way that is more specific to itself and less ambiguous than natural human languages. sync advancer A video component for resolving horizontal and burst phase signals for multiple camera signals with different characteristics due to cabling. In video, where signal pulse timing is important for combing signals, pulse discrepancies can arise from simple things like cables of uneven lengths, sometimes even resulting in delays that must be resolved before further processing the signals. sync separator A video device for taking a composite video input and deriving the characteristics of the signal (such as composite sync, vertical sync, horizontal sync, back porch, field, ID) so that the signal can be processed to synchronize with other video components. For example, a synch separator can be used to provide loop-through viewing from a camera to a monitor while synching the camera feed to another component. The sync separator provides the pulses required by other components and may or may not be genlockable. Different models are available for positive-going or positive-going video (or both). See genlock, negative-going video. synchronize 1. To cause to occur at the same instant in time. 2. To precisely match two waves or two functions. 3. To assess the characteristics of an input signal and process it to conform to characteristics expected by a receiving link/component. 4. To assess the characteristics of two or more input signals and process them to conform to timing, pulse, or other characteristics in order to form a single signal or multiple signals with compatible characteristics. synchronous Signals with the same timing reference and the same frequency. See isochronous, asynchronous. Synchronous Data Link Control SDLC. In IBM Systems Network Architecture (SNA) systems, SDLC is a bit-oriented, link-level protocol that provides a means of moving data between Network Addressable Units (NAUs). The Data Link Control layer lies between the higher layers and the Physical Control layer and communications links, and passes information through. SDLC is a subset of the High-level Data Link Control (HDLC) protocol. SDLC is packet-oriented, with each frame comprising a header, information, and trailer. It transparently provides flow control, multipoint addressing, error detection, and multimessage capabilities. See Systems Network Architecture. Synchronous Digital Hierarchy SDH. A fiber optics transmission technology for efficient transport of digital signals. Different versions of SDH are defined; those used within North America and Japan and those used in Europe and elsewhere.

The North American version of this general technology is called SONET and is standardized by the American National Standards Institute (ANSI). SDH standards are coordinated by the International Telecommunications Union (ITU-T) and published primarily as G Series Recommendations documents. See G Series Recommendations, SONET. Synchronous Optical Network See SONET. Syncom 3 The first geostationary satellite, designed for telecommunications use, launched on 19 August 1964 by the United States.

The Syncom IV-4 communications satellite as it is released from the payload bay of the Space Shuttle Discovery. The Syncom IV-4 was deployed from the Shuttle with a disc toss motion in August 1985. [NASA image]

syntax 1. The rules of structure or grammar for a language, natural or computer. 2. In programming, the words and symbols valid within the structure and scope of a computer language. Debuggers and compilers will provide a general syntax error alert to the developer when they encounter unrecognized words/ symbols or, sometimes, word/symbol positions or combinations. (They will flag spelling errors as syntax errors, for example.) syntax error An error in a programming statement which indicates an unrecognized word, symbol, or structure. Syntax errors are usually flagged and displayed by debuggers and compilers so that the error can be corrected. See syntax. synthesized voice A mechanically or electronically generated speaking system. Synthesized voices are now used on phone systems, computers, and certain public address systems. The voice may be constructed from recordings of natural human voices, pieced together electronically from sound samples, or may be entirely synthetic. See speech synthesis. Syslog Protocol A Berkeley Software Distribution (BSD) protocol that provides service options related to the propagation of event messages over a network; Syslog Protocol has now been ported to other operating systems as well. The protocol was submitted as an Information RFC by C. Lonvick in August 2001.

Syslog messages may have varying content in varying format, since they originate on a number of types of platforms. Syslog services originate, are relayed, and are received in device, relay, or collector modes. A sender transmits a message without knowledge of whether the next leg is a relay or recipient. A collector may also be a relay and may selectively collect or relay multiple messages. A relay may alter the format of a message, but it is generally not recommended unless it is unable to discern the proper implementation of the format, in which case it should modify it. Messages are transported over User Datagram Protocol (UDP) using port 514 and are usually received over port 514. See RFC 3164. sysop system operator. The sysop, or systems administrator, sometimes also called the super user, due to his or her higher access privileges and power over other accounts on a system. The system operator is a technical expert with high security privileges, managing a bulletin board system or computer network. On small systems, like BBSs, these tasks may be performed by one person. On medium-sized systems, sometimes assisting sysops are assigned intermediary privileges, between those of the super user and regular system users. Larger systems often split the installation, security, administration, file management, diagnostic, and tuning responsibilities of a network among a number of system operators, or may even have an entire facility devoted to the administration of the network. system disk A disk which includes “boot” information, that is, low-level operating information, from which a computer system can be started. This may be a floppy drive, hard disk, CD-ROM, or other disk with system files somewhat transparent to the user. Without certain system files, a computer cannot configure itself to recognize peripherals, available memory, monitor types, etc. See bootstrap, operating system. system integrator A commercial vendor offering a variety of network design and implementation services according to the configuration needs of various customers. system reliability architecture SRA. Systems designed as fault tolerant and reliable, and which function even while undergoing maintenance checks and procedures. SRA implies systems which incorporate redundancy, the ability to hot swap components, fast recovery from power failures, and online upgrading of software. System Services Control Point SSCP. A point in a network host system within the Virtual Telecommunications Access Method (VTAM) that initiates host applications, so that they can be associated with dependent logical units (LUs) and connections initiated and terminated. SNA systems use the SSCP to set up terminal sessions and, more recently, to link with sessions with other systems such as Unix, for example. In SNA, one SSCP in the domain handles this type of interoperability. It consists of software in the host processor for handling connections to the Network Control Program (NCP) which, in turn, manages data

S

link protocols and routing functions. The SSCP initiates sessions by issuing an Activate Physical Unit (ACTPU) command and subsequent Activate Logical Unit (ACTLU) commands. The SSCP communicates between SLUs and the host application. If the necessary resources are not available, an error command to the SLU is issued to prevent or abort establishment of a session. Systems Network Architecture SNA. One of the first significant layered architectures, introduced in 1974 by IBM Corporation. Layered architectures like SNA were developed when computers became smaller and less expensive, resulting in an increase in mass production and a greater variety of hardware configurations and operating systems. Thus, interconnectivity and specialization challenges were posed and new markets opened up. Layered architectures were a practical way to resolve these needs. Systems Network Architecture (SNA) provides a cohesive way for users to communicate between systems for transmitting and receiving, by specifying the operating relationships of various components of the different systems. To achieve this, various communications peripherals, i.e., adapters, modems, data encryption devices, etc. are designed to be consistent with the implementation of the SNA specification. SNA came out of the mainframe environment and thus was designed as a star topology host environment for supporting multiple terminals. However, more recent additions make it possible to support multihost, multidomain networks with peer-to-peer distributed computing topologies, as well. SNA shares many common overall concepts with the Open Systems Interconnection (OSI) hierarchically layered network model, which evolved at about the

same time. Both are seven-layer models, arranged from the physical and data link layers at the lower end to presentation and transaction (application) layers at the higher end. While the two systems are not directly compatible, there is now some SNA support for OSI protocols to improve interoperability. In brief, the layers described for SNA from high level to low level include: Layer

Functions

transaction services

application program functions for application intercommunication

presentation services content of data messages is defined data flow control

traffic flow and logical data grouping between two end users

transmission control retransmission and error recovery, flow control, end-toend acknowledgments path control

data routing, parallel transmission over multiple links, segmentation and reassembly of data packets

data link control

transmissions, retransmissions across a link

physical

the physical media over which data are transported

See System Services Control Point, Token-Ring.

T 1. symb. tera- 2. abbrev. terminal. 3. abbrev. tip (as in tip and ring). 4. abbrev. trunk. T connector A generic name for many types of cable connectors shaped roughly like the letter “T.” This is a common shape for splitters, Ethernet cabling, certain types of terminators, and adaptors. The purpose of a T connector is similar to that of a Y connector: to join two inputs into one or to split one input into two. T interface In ISDN, a number of reference points have been specified as R, S, T, and U interfaces. To establish ISDN services, the telephone company typically has to install a number of devices to create the all-digital circuit connection necessary to send and receive digital voice and data transmissions. The T interface is the point between the phone company’s switching device that serves the subscriber and the subscriber’s building wiring. Thus, the T interface is the point between the central office switch and the user’s phone connection. See ISDN interfaces for a diagram and relationships. T Series Recommendations A series of ITU-T recommendations providing guidelines for terminals for telematic services. These guidelines are available as publications from the ITU-T for purchase on the Net. Since ITU-T specifications and recommendations are widely followed by vendors in the telecommunications industry, those wanting to maximize interoperability with other systems need to be aware of the information disseminated by the IUT-T. A full list of general categories is listed in Appendix C and specific series topics are listed under individual entries in this dictionary, e.g., S Series Recommendations. See T Series Recommendations chart. T1, T-1 A communications system that can be carried over ordinary twin cable pairs, or fiber optic, that provides significant speed and bandwidth improvements over earlier technologies. The T1 time division multiplexing (TDM) pulse code modulation (PCM) system is capable of carrying multiple simultaneous conversations (24 over twin cable pairs), and began to be incorporated into central office trunk switching technologies in the 1960s with more significant, widespread implementation to subscribers in 1982. T1 digital communications represented a significant

T

change over existing analog communications systems. Pulse code modulation (PCM) was pioneered in the 1940s and 1950s, but it was not until the early 1960s that some practical success was achieved. It was then implemented on T1 lines developed in the late 1950s by AT&T. Proponents wanted the improved transmissions technologies to be compatible with existing switching systems, potentially saving billions of dollars by using, rather than replacing, central office switching circuitry. The capacity of T1 was originally stated as 1.544 Mbps (U.S., Canada, Japan), although European ITU-T standard implementations are faster, 2.048 Mbps, and upper limits tend to change as more efficient techniques are incorporated to improve the throughput of a system as a whole. It is a low loss transmissions system when delivered over fiber optic cable, but is subject to crosstalk in long metal wire installations. While high-capacity 22-gauge is preferable for T1 transmissions, the system is not limited to this and can work with a number of paper or plastic insulated cable pairs, or staggered twist cable in use in telephone systems for decades. A single cable can handle up to almost 5000 channels. Due to its cost, T1 is still primarily used in large installations, phone trunks, government installations, campus backbones, and medium and large enterprise networks, but installation and usage costs are still dropping and T1 may soon be accessible to small businesses, as well. See T carrier. T120 A designation for magnetic tape storage that represents up to a maximum number of minutes of video recording at regular play speeds (as opposed to extra play), in this case 120 minutes. T-Bone A freely distributable Java-based distributed network broadcasting system which permits interconnection of JavaBeans on different systems. It can be used for remote monitoring and control, push channels on the Internet, stock ticking feeds, and online discussions. See Java, JavaBeans. T-carrier The generic term for T-1, T-2, etc. communications technologies standardized for highspeed data transmissions in North America. It served as the basis for the European E-carrier and the Japanese J-carrier systems, which are similar in concept,

T

ITU-T T Series Recommendations General, Classifications T.0 T.1 T.2 T.3 T.4 T.6 T.80 T.121 T.300 T.400

Classification of facsimile terminals for document transmission over the public networks Standardization of phototelegraph apparatus Standardization of Group 1 facsimile apparatus for document transmission Standardization of Group 2 facsimile apparatus for document transmission Standardization of Group 3 facsimile terminals for document transmission Facsimile coding schemes and coding control functions for Group 4 facsimile apparatus Common components for image compression and communication – basic principles Generic application template General principles of telematic interworking Introduction to document architecture, transfer and manipulation

Standardized Test Charts, Images T.20 Standardized test chart for facsimile transmissions T.21 Standardized test charts for document facsimile transmissions T.22 Standardized test charts for document facsimile transmissions T.23 Standardized colour test chart for document facsimile transmissions T.24 Standardized digitized image set Multipoint Transmissions T.122 Multipoint communication service – service definition T.125 Multipoint communication service protocol specification T.126 Multipoint still image and annotation protocol T.127 Multipoint binary file transfer protocol T.128 Multipoint application sharing Security T.36 Security capabilities for use with Group 3 facsimile terminals Character Sets, Encodings, Imaging T.50 International Reference Alphabet (IRA) (Formerly International Alphabet No. 5 or IA5) – Information tech. – 7-bit coded character set for information interchange

T.51 Latin-based coded character sets for telematic services T.52 Non-Latin coded character sets for telematic services T.53 Character coded control functions for telematic services T.61 Character repertoire and coded character sets for the international teletex service T.351 Imaging process of character information on facsimile apparatus Terminal Characteristics T.561 Terminal characteristics for mixed mode of operation MM T.562 Terminal characteristics for teletex processable mode PM.1 T.563 Terminal characteristics for Group 4 facsimile apparatus T.571 Terminal characteristics for the telematic file transfer within the teletex service Proced., Routing, Miscellaneous T.10 Document facsimile transmissions on leased telephone-type circuits T.10bis Document facsimile transmissions in the general switched telephone network T.11 Phototelegraph transmissions on telephone-type circuit T.12 Range of phototelegraph transmissions on a telephone-type circuit T.15 Phototelegraph transmission over combined radio and metallic circuits T.30 Proced. for document facsimile transmission in the general switched telephone network T.31 Asynchronous facsimile DCE control – Service Class 1 T.32 Asynchronous facsimile DCE control – Service Class 2 T.33 Facsimile routing utilizing the subaddress T.35 Procedure for the allocation of ITU-T defined codes for nonstandard facilities T.37 Proced. for the transfer of facsimile data via store-and-forward on the Internet T.38 Proced. for real-time Group 3 facsimile communication over IP networks T.39 Application profiles for simultaneous voice and facsimile terminals T.42 Continuous-tone colour representation method for facsimile T.43 Colour and grayscale image representations using lossless coding scheme for facsimile T.44 Mixed raster content (MRC) T.45 Run-length colour encoding T.60 Terminal equipment for use in the teletex service

T.62

Control procedure for teletex and Group 4 facsimile services T.62bis Control procedure for teletex and G4 facsimile services based on recommendations X.215 and X.225 T.63 Provisions for verification of teletex terminal compliance T.64 Conformance testing proced. for the teletex recommendations T.65 Applicability of telematic protocols and terminal characteristics to computerized communication terminals (CCTs) T.66 Facsimile code points for use with recommendations V.8 and V.8 bis T.70 Network-independent basic transport service for the telematic services T.71 Link access protocol balanced (LAPB) extended for half-duplex physical level facility T.85 Application profile for recommendation T.82 – progressive bi-level image compression (JBIG coding scheme) for facsimile apparatus T.86 Information tech. – digital compression and coding of continuous-tone still images: registration of JPEG Profiles, SPIFF Profiles, SPIFF Tags, SPIFF Color Spaces, APPn Markers, SPIFF Compression types and Registration Authorities (REGAUT) T.87 Information Tech. – lossless and nearlossless compression of continuous-tone still images – Baseline T.88 Information tech. – coded representation of picture and audio information – lossy/ lossless coding of bi-level images T.89 Application profiles for recommendation T.88 – lossy/lossless coding of bi-level images (JBIG2) for facsimile T.90 Characteristics and protocols for terminals for telematic services in ISDN T.100 International information exchange for interactive videotex T.101 International interworking for videotex services T.102 Syntax-based videotex end-to-end protocols for the circuit mode ISDN T.103 Syntax-based videotex end-to-end protocols for the packet mode ISDN T.104 Packet mode access for syntax-based videotex via PSTN T.105 Syntax-based videotex application layer protocol T.106 Framework of videotex terminal protocols T.107 Enhanced human-machine interface for videotex and other retrieval services (VEMMI)

T.120 Data protocols for multimedia conferencing T.Imp120 Implementors’ Guide for SG 16 recommendations T.123 Network-specific data protocol stacks for multimedia conferencing T.124 Generic conference control T.134 Text chat application entity T.135 User-to-reservation system transactions within T.120 conferences T.136 Remote device control application protocol T.137 Virtual meeting room management – services and protocol T.140 Protocol for multimedia application text conversation T.150 Telewriting terminal equipment T.170 Framework of the T.170-Series recommendations T.171 Protocols for interactive audiovisual services: coded representation of multimedia and hypermedia objects T.172 MHEG-5 – support for base-level interactive applications T.173 MHEG-3 script interchange representation T.174 Application programming interface (API) for MHEG-1 T.175 Application programming interface (API) for MHEG-5 T.176 Application programming interface (API) for Digital Storage Media Command and Control (DSM-CC) T.180 Homogenous access mechanism to communication services T.190 Cooperative document handling (CDH) – framework and basic services T.191 Cooperative document handling (CDH) – joint synchronous editing (point-topoint) T.192 Cooperative Document Handling – complex services: Joint synchronous editing and joint document presentation/viewing T.200 Programmable communication interface for terminal equipment connected to ISDN T.330 Telematic access to interpersonal messaging system T.390 Teletex requirements for interworking with the telex service T.501 Document application profile MM for the interchange of formatted mixed mode documents T.502 Document application profile PM-11 for the interchange of simple structure, character content documents in processable and formatted forms

T

ITU-T T Series Recommendations, contd.

Information Tech., IT ODA

format: abstract interface for the manipulation of ODA documents T.414 Information tech. – Open Document Architecture (ODA) and interchange format: document profile T.415 Information tech. – Open Document Architecture (ODA) and interchange format: open Document Interchange Format (ODIF) T.416 Information tech. – Open Document Architecture (ODA) and interchange format: character content architectures T.417 Information tech. – Open Document Architecture (ODA) and interchange format: raster graphics content architectures T.418 Information tech. – Open Document Architecture (ODA) and interchange format: geometric graphics content architecture T.419 Information tech. – Open Document Architecture (ODA) and interchange format: audio content architectures T.421 Information tech. – Open Document Architecture (ODA) and interchange format: tabular structures and tabular layout T.422 Information tech. – Open Document Architecture (ODA) and interchange format – identification of document fragments T.424 Information tech. – Open Document Architecture (ODA) and interchange format: temporal relationships and nonlinear structures Document Transfer & Manipulation (DTAM)

T.81

T.431

Proced., Routing, Miscellaneous, contd. T.503 T.504 T.505

T.506

T.510 T.521 T.522 T.523 T.541 T.564 T.611

T.82 T.83 T.84 T.411

T.412 T.413

A document application profile for the interchange of Group 4 facsimile documents Document application profile for videotex interworking Document application profile PM-26 for the interchange of enhanced structure, mixed content documents in processable and formatted forms Document application profile PM-36 for the interchange of extended document structures and mixed content documents in processable and formatted forms General overview of the T.510-Series Recommendations Communication application profile BT0 for document bulk transfer based on the session service Communication application profile BT1 for document bulk transfer Communication application profile DM-1 for videotex interworking Operational application profile for videotex interworking Gateway characteristics for videotex interworking Programming Communication Interface (PCI) APPLI/COM for facsimile Group 3, facsimile Group 4, teletex, telex, E-mail and file transfer services

Information tech. – digital compression and coding of continuous-tone still images – requirements and guidelines Information tech. – coded representation of picture and audio information – progressive bi-level image compression Information tech. – digital compression and coding of continuous-tone still images: compliance testing Information tech. – digital compression and coding of continuous-tone still images: extensions Information tech. – Open Document Architecture (ODA) and interchange format: introduction and general principles Information tech. – Open Document Architecture (ODA) and interchange format: document structures Information tech. – Open Document Architecture (ODA) and interchange

T.432 T.433 T.434 T.435

T.436

T.441

Document Transfer And Manipulation (DTAM) – services and protocols – introduction and general principles Document Transfer And Manipulation (DTAM) – services and protocols – service definition Document Transfer And Manipulation (DTAM) – services and protocols – protocol specification Binary file transfer format for the telematic services Document Transfer And Manipulation (DTAM) – services and protocols – abstract service definition and proced. for confirmed document manipulation Document Transfer And Manipulation (DTAM) – services and protocols – protocol specifications for confirmed document manipulation Document Transfer And Manipulation (DTAM) – operational structure

but somewhat different in implementation details. Tcarrier systems are a generalized technology suitable for the transmission of voice, data, facsimile, multimedia audio and visual information over one system. See T1. See T- Carrier Transmission Systems Overview chart. T-CCS Transparent Common Channel Signaling. See Common Channel Signaling. T/R transmit/receive. TAB See tone above band. table Collection of ordered data, often stored in arrays or printed in columnar form. tablet Hardware peripheral input device, usually rectangular, with an associated mouse or stylus. Graphics tablets are frequently used with engineering and CAD/CAM software. TABS Telemetry Asynchronous Block Serial Protocol. A medium-fast AT&T network protocol. Tabulating Machine Company Herman Hollerith, who developed Hollerith punch cards to store census data from the 1890 U.S. census, founded the Tabulating Machine Company in 1896 to market his products. Eventually, the company was sold out to the Computer-Tabulating-Recording company, which, in turn, became International Business Machines (IBM) in the 1920s. TACD Telephone Area Code Directory. TACS Total Access Control/Communications System. A first-generation, analog cellular FM-based radio system introduced in the United Kingdom by Cellnet and Vodaphone in the early 1980s. It is similar to the U.S. AMPS system. TACS used frequency shift keying (FSK) signaling with each TACS call assigned to a different frequency through frequency division multiple access (FDMA). There are now a number of variations of the original TACS system, including Extended TACS (ETACS) which used additional frequencies, International TACS (ITACS), International Extended TACS (IETACS), Narrowband TACS (NTACS), and Japan TACS (JTACS). Tag Distribution Protocol TDB. A Cisco network protocol for building routing databases for the han-

dling of tagged datagrams that are accessed by tag switches and tag edge routers. The tag bindings established by routers are communicated to neighboring routers through TDB. See tag switching. Tag Image File Format See TIFF. tag switching A Cisco proprietary data link layer/ network layer routing/switching architecture intended to provide performance and scalability through existing network infrastructures. Tag switching is a method of using tag edge routers and assigning software tags to each IP datagram in a sequence in order to identify router paths. In order to reduce the time needed for each router to send datagrams across the network, the tag edge routers append a special string of bits, called the tag, to the datagrams before they are transmitted across the backbone. The tag provides routing information to other routers (tag switches) so that they are freed from table lookups and processing. The tag does not stand for a specific path through the network but rather represents a general class of forwarding. Tag switching is similar to IP switching, except that nonstandard tag bits are appended. See IP switching, label switching, Tag Distribution Protocol. TAI See International Atomic Time. tail circuit A final segment in a connection between a central switching location and the subscriber. Talbot, William Henry Fox (1800-1877) An English experimenter who developed a salt and silver nitrate photographic paper print process in the early 1930s. Photos up to this time had been printed on ceramic and silver-plated copper. Talbot was able to produce photographic silhouettes that he called sciagraphs, by embedding light-sensitive chemicals in the paper and exposing parts of the paper to light. He further realized that an image created on a glass plate could be replicated many times in the same manner, a variation on the concept of steel engravings that constituted an early type of manual photocopying process. The Fox Talbot Museum of Photography in the U.K. is named in his honor and a project is underway to develop a searchable archive

T-Carrier Transmissions Systems Overview Type

Signal DS-0

Bandwidth 64

Typical cable

Notes

Originally developed for digital voice, also used for data communications. European E1 standard is similar.

Kbps

T1

DS-1

1.544 Mbps

19, 22, or 24 gauge

T1C

DS-1C

3.152 Mbps

19, 22, or 24 gauge pairs

T2

DS-2

6.312 Mbps

low capacitance

T3

DS-3

44.736 Mbps

fiber optic or microwave

T4

DS-4

274.760 Mbps

fiber optic or microwave

High-speed, high bandwidth applications.

T

of the ca. 10,000 letters that make up Henry F. Talbot’s correspondence. See Daguerré, L.J.M. talking battery In early telephone central offices, a 24- or 48-V battery used for supplying the power for a phone conversation. Later, starting around 1893, these were replaced by common batteries at the central office which, in turn, supplied a “talking” battery to each subscriber. See battery. tandem Two, dual, pair. Acting together, in conjunction with, partnership. Tandem Connection TC. Tandem connections, that is, paired or redundant connections, are used at the discretion of network carriers, and software with TC are mostly interoffice network applications rather than general public subscriber network applications. In SONET, the Tandem Connection layer is optional. Tandem Connection Overhead TCO. In SONET, an optional overhead layer between the Line and Path layers as defined in ANSI T1.105. The layer deals with the reliable network transport of Path layer payload and its associated overhead. TANE The Telephone Association of New England. A regional association providing information, education, and support to its membership. http://www.tane.org/ Tandy Color Computer TRS-80C, “CoCo.” A Tandy Corporation computer introduced in spring, 1981, aimed at the home market, following up on the TRS-80 Models I and II, that targeted business users. Called CoCo for short by most of its users, the computer featured a Motorola 6809E microprocessor, 4 Kbytes of RAM expandable to 64, color graphics (256 x 192), two joystick ports, a cassette interface, and an RS-232 serial interface, for a list price of $399. One of the more interesting pieces of software running on the CoCo was OS-9, a realtime, multitasking operating system. Considering the home user price of the CoCo and the fact that multitasking didn’t become mainstream on personal computers until the Commodore Amiga was released in 1985, it’s a tribute to programmers that they had a multitasking OS running on the CoCo. tangent galvanometer An early current-detecting instrument employing a card to record the degree of deflection. This type of galvanometer is subject to interference from the Earth’s magnetic field. See galvanometer. TAO Project TAO is part of the Satori project being carried out at Washington University and being developed by the Distributed Object Computing group, funded partly by the DARPA Quorum program. It is a high-performance, realtime Object Requester Broker (ORB) designed to provide end-toend network quality of service (QoS) guarantees to applications by integrating CORBA middleware with operating system input/output subsystems, communications protocols, and network interfaces. TAO is freely distributable to researchers and developers within ACE copyright restrictions. See CORBA. tape recorder A serial data recording instrument, commonly used for music, dictation, talking books, and computer data backup, which is descended from

the Danish inventor Valdemar Poulsen’s telegraphone patented in 1890. The telegraphone was initially used for write-once/read-many dictation recordings. Through various improvements by different contributors, the magnetic tape recorder was developed in the early 1930s. One of the important related inventions was contributed by Fritz Pfleumer of Germany, who patented a way of applying magnetic powder to paper or film. By the late 1940s, experimenters were scrambling to find a way to record video images on tape, and the early systems were demonstrated by the mid1950s. Tape recorders were used experimentally to record live music concerts between 1936 and 1948, and the music recording industry boomed. By the 1960s, audio tapes were common in homes, businesses, and automobiles. See telegraphone. TAPI See Telephony Application Programming Interface. tariff Scheduled rate or charge between a carrier and its subscribers, usually published, and sometimes regulated by government agencies. TAS Telecommunication Authority of Singapore. TAXI Transparent Asynchronous Transmitter/Receiver Interface. Taylor, A.H. A member of the U.S. Naval Research Laboratory who observed in 1922 that a radio echo from a steamer could potentially be used to locate a vessel. This observation was not put into practical use until some years later. See radar. TBOP See Transparent Bit Oriented Protocol. Tc See Committed Rate Measurement Interval. TCAP See Transaction Capability Application Part. TCI Telecommunications, Inc. TCIF Telecommunications Industry Forum. TCM trellis code modulation. See trellis coding. TCO See Tandem Connection Overhead. TCP/IP Transmission Control Protocol/Internet Protocol. An internetworking transmissions protocol combination developed in the 1970s on the ARPANET to enable the intercommunication of various types of computers across wide area networks (WANs). It was widely adapted by educational institutions by the 1980s and by corporations by the 1990s. Although it appeared for a time that Open Systems Interconnection might overtake TCP/IP, it has now become an international standard which has been implemented on most microcomputers since the mid-1990s. TDM See time division multiplexing. TDMA See time division multiple access. TDRSS Tracking and Data Relay Satellite System. TDS See Terrestrial Digital Service. TDU 1. tape drive unit. 2. See Topology Database Update. te wave transverse electric wave. Team OS/2 A strong, independent, international support and advocacy group for IBM’s OS/2 (Operating System/2). It provides education, demonstrations, resources, Web links, and other services for OS/2

users and the general community. OS/2 users have a strong enthusiasm for this operating system, and many members independently advocate that it is superior to other commercial Intel-based personal computer operating systems. However, the official position of Team OS/2 is that OS/2 is strong enough to stand on its own merits without comparisons to other systems. Team OS/2 was founded by Dave Whittle shortly before the release of OS/2 version 2. The Team OS/2 Web site has further information on the formation and goals of the organization, and lists of other OS/2-related links on the Web. See OS/2. http://www.teamos2.org/ Technical and Office Protocols TOP. A protocol development effort to support the needs of engineering and office environments. TOP was initiated by Boeing, and is now part of the Manufacturing Automation Protocol/Technical and Office Protocols (MAP/TOP) users’ group. TOP was designed to conform to the Open Systems Interconnection (OSI) model. Technical Reference Model TRM. A common framework and vocabulary for creating and communicating digital information services infrastructures, components, and their relationships in order to facilitate the development of systems that can intercommunicate. Various prominent bodies, including the American National Standards Institute (ANSI), the International Telecommunication Unions (ITU), the Institute of Electrical and Electronics Engineers (IEEE), the International Organization for Standardization (ISO), and others have made efforts to provide basic frameworks for the development of consistent, interoperable, multiplatform environments, thus providing flexibility in the choice of platform while still maintaining a means to exchange data. The TRM essentially consists of three main entities, the Application Programming entity, the Application Platform entity, and the External Environment. Further, there are two interfaces, thus comprising five basic aspects. Providing a data link between the Application Programming and Application Platform entities is the Applications Programming Interface. Between the Application Platform entity and the External Environment is the External Environment Interface. See Applications Programming Interface, External Environment Interface. Technical Specification TS. In the Internet Standards Process, a TS is any formal description of a convention, format, procedure, protocol, or service. The description may be complete in itself, or may contain references to other specifications. Certain conventions guide the general format of a TS, and a statement of scope and intent for use is required, but a TS does not specify its application within the context of the Internet; this is defined in an Applicability Statement. See Applicability Statement. Technology Policy Working Group TPWG. A working group within the Committee on Applications and Technology founded in the mid-1990s. The TPWG addresses broadbased, overlapping technology issues related to interoperability and scalability of new telecommunications and information

services. The group fosters partnership and cooperation between industry and government agencies. TEI See Terminal Endpoint Identifier. telautograph A type of early telegraph machine invented in the late 1800s, which could transmit handwriting over short distances. The earliest models used a pen writing a continuous line, and did not leave breaks between letters or words. Subsequent improvements were made by E. Gray, F. Ritchie, and others, which allowed the pen to be lifted off the paper when desired. These devices were used for several decades. Modern versions of the telautograph, using electronics, are now known as telewriters, and have only recently been superseded by facsimile machines. Telco, TelCo Abbreviation for telephone company, a local or regional telephone carrier. telebusiness The British counterpart of telemarketing, teleresearch, and telesales. telecom abbrev. telecommunications. Telecom Developers A telephony industry trade show, the forerunner to the Computer Telephony Conference and Exposition, held regularly in the spring. Telecom Information Exchange Services TIES. A service of the International Telecommunication Union (ITU) which provides member resources and access to the ITU Terminology database (TERMITE). See TERMITE. Telecom Services Association of Japan TELESA. A nonprofit organization of member companies engaged in providing Internet-related services. The group has established a consortium to conduct field trials of electronic commerce systems in cross-border contexts and is responsible for initiating the Integrated Next Generation of Electronic Commerce Environment Project (INGECEP) which is carried out in cooperation with APEC. See Integrated Next Generation of Electronic Commerce Environment Project. Telecommunication Standardization Advisory Group TSAG. A division of the International Telecommunications Union which interprets global standardization concepts and goals into practical implementations. telecommunications 1. Meaningful wired/cabled or wireless transmission and receipt of signals over distance. 2. Broadcast, telegraph, phone, and computer network communications, frequently with a giveand-take quality or by choice of the receiving party, carried through a variety of media, including wires, fibers, air, etc. 3. The term is sometimes used to indicate a broader scope of communications telephony, to include video, for example (although telephony’s meaning is not quite as narrow as thought by some). 4. This is defined in the Telecommunications Act of 1996, and published by the Federal Communications Commission (FCC), as follows: “... the transmission, between or among points specified by the user, of information of the user’s choosing, without change in the form or content of the information as sent and received.”

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See Federal Communications Commission, Post Roads Act, Telecommunications Act of 1996. Telecommunications Act of 1996 This is the first substantial overhaul of telecommunications regulations since 1934, signed into law by President Clinton on 8 February 1996. The goal and intent of the law is to enable open access to the communications business and to permit any business to compete with any other telecommunications business. The chief impact of this act is on phone and broadcast services. Regulatory responsibility is largely shifted away from state courts and regulatory agencies to the Federal Communications Commission (FCC), but much of the administrative workload remains with the state authorities. Some of the changes include the lifting of some longstanding restrictions, with the Regional Bell Operating Companies (RBOCs) now permitted to provide interstate long distance services. Telephone companies can now provide cable television services and cable companies can now provide local telephone services. The FCC and individual states are responsible for implementing the terms, and the FCC has published an implementation schedule for this important act regarding the various issues of interconnection, universal service, access, assignment of broadcast licenses, etc. See Above 890 decision, Commercial Space Launch Act of 1984, Communications Act of 1934, Federal Communications Commission. Telecommunications and Customer Service Foundation TCSF. A Canadian-based association formed to promote excellence in customer service in the telecommunications industry. Telecommunications and Information Infrastructure Assistance A U.S. Department of Commerce grant program established in 1994 to assist local government and nonprofit organizations in funding projects which contribute to the design and development of the national information infrastructure (NII). Telecommunications and IP Harmonization Over Networks TIPHON. An ETSI working group that came about as the result of the shift from traditional analog telephony to digital telephony and the desire of vendors to offer voice services over digital networks such as the Internet. Project TIPHON addresses issues of market demand and service compatibility and transmission over network boundaries. The ETSI trademarked TIPHON group works jointly with the International Multimedia Teleconferencing Consortium (IMTC) to organize interoperability plugtests, opportunities for vendors to test their products with those of other developers in the context of Internet Protocol (IP) telephony. See Voice over IP. Telecommunications Association, Latvia A Latvian trade organization fostering the development of telecommunications technologies and products, the liberalization of the telecommunications business sphere, and the adjustment of regulations in Latvia to further growth and development in the field. In February 2001, the association admitted the IP

Telephony Association with the view of improving progress in the standardization and regulation of the Latvian communications sector. telecommunications bonding backbone TBB. See telecommunications main grounding busbar. telecommunications broker An entity (person or business) which assists in negotiating contracts for communications services on the part of a user, or one which purchases specialized or bulk telecommunications services with the intent of reselling these services to consumers, sometimes at discount rates. See broker. telecommunications carrier This is defined in the Telecommunications Act of 1996 and published by the Federal Communications Commission (FCC), as: “... any provider of telecommunications services, except that such term does not include aggregators of telecommunications services (as defined in section 226). A telecommunications carrier shall be treated as a common carrier under this Act only to the extent that it is engaged in providing telecommunications services, except that the Commission shall determine whether the provision of fixed and mobile satellite service shall be treated as common carriage.” See Federal Communications Commission, Telecommunications Act of 1996, telecommunications carrier duties. telecommunications carrier duties The Federal Communications Commission (FCC) stipulates a number of duties in the Telecommunications Act of 1996 as follows: “Each telecommunications carrier has the duty— ‘(1) to interconnect directly or indirectly with the facilities and equipment of other telecommunications carriers; and ‘(2) not to install network features, functions, or capabilities that do not comply with the guidelines and standards established pursuant to section 255 or 256.” telecommunications closet A wiring panel or room or other centralized, secured or separated administrations center for equipment junctions and/or demarcation points. Larger systems may have a series of panels, punchdown blocks, racks, or other furnishings to secure and organize the wiring system. See telecommunications main grounding busbar, wiring closet. Telecommunications Development Bureau BDT. An agency established as a result of the Plenipotentiary Conference in Nice, France in 1989 to set up technical assistance in developing countries for coordinating, standardizing, and regulating telecommunications in third-world countries. France is the location for many regulatory and standardization bodies. BDT activities began in 1990. Telecommunications Electric Service Priority TESP. A governmental restoration initiative that promotes voluntary inclusion of telecommunications

facilities considered critical to national security and emergency preparedness (NS/EP) in existing electric utility emergency priority restoration systems. TESP is administered by the U.S. Office of Priority Telecommunications (OPT) at the National Communications System (NCS) in cooperation with the U.S. Department of Energy (DoE), state governments, and utility services. TESP promotes the voluntary modification of existing electric utility emergency priority power restoration systems to include telecommunications facilities that may be critical to NS/EP. See National Communications System. telecommunications equipment This is defined in the Telecommunications Act of 1996, and published by the Federal Communications Commission (FCC), as: “... equipment, other than customer premises equipment, used by a carrier to provide telecommunications services, and includes software integral to such equipment (including upgrades).” See Federal Communications Commission, Telecommunications Act of 1996. telecommunications facilities The integrated structures and equipment which enable telecommunications to be conducted and managed. This may include secure rooms for servers or patch bays, consoles, PBX systems, satellites, telephones, facsimile machines, modems, wires and cable, video cameras, radio transceivers, etc. telecommunications grounding busbar TGB. See telecommunications main grounding busbar. Telecommunications Industry Association TIA. TIA began in 1924 as a small group of communications suppliers. Later, the group became a committee of the U.S. Independent Telephone Association (USTSA). This group split off from the USTSA in 1979 to become a separate, affiliated association, and TIA was formed in 1988 through a merger of USTSA and the Information and Telecommunications Technologies Group of EIA A national trade organization representing about 1000 member companies which provide communications and information technology products, materials, and services, TIA provides a forum for discussing industry information and issues, organizes industry trade conventions, and serves as a voice for manufacturers and suppliers of communications products for matters of public policy and international commerce. http://www.tiaonline.org/ Telecommunications Information Network Architecture TINA. A common architecture for building and managing communications services developed by the Telecommunications Information Network Architecture Consortium in the early 1990s. This architecture logically separates the physical infrastructure and the applications from the need to communicate directly with each another. Control and management functions are integrated and can be placed on the network independent of geography through a single Distributed Processing Environment (DPE). See Telecommunications Information Network

Architecture Consortium. Telecommunications Information Network Architecture Consortium TINA-C. An international association of over 40 telecommunications operators and manufacturers who first came together at a TINA Workshop in 1990 and formed the consortium to cooperatively define a common architecture (TINA) to be promoted as a global standard for building and managing telecommunications services. This work draws heavily on the work of other organizations and standards bodies in order to take advantage of ongoing studies and developments, to expedite the progress of the TINA project, and to promote the harmonious cooperation of various groups with similar goals. http://www.tinac.com. telecommunications lines Physical lines, usually metal wire or fiber optic cable, over which communications are transmitted, usually by electrical impulses or light. Contrast to wireless communications. telecommunications main grounding busbar TMGB. An important component of a telecommunications electronic grounding system that extends the building grounding electrode system for a telecommunications network infrastructure. Typically there is one per building, located in an accessible communications closet. It is the central attachment point for a telecommunications bonding backbone (TBB) with one or more telecommunications grounding busbars (TGBs). A TMGB is fabricated to facilitate low-resistance contact between lugs and busbars. It should be directly bonded to the electrical service ground and to a TGB which, in turn, connects to a permanent metallic structural element of the building. The TMGB should never be bonded to a secondary electrical conduit or pipe, as this may result in different ground potentials between the TMGB and the communications equipment grounding. If multiple closets exist in the same building, the TGBs should be bonded to one another and to the TMGB through approved insulated wires to form a telecommunications bonding backbone (TBB). The TMGB resembles a metal cribbage board in that it has pairs of holes punched (all the way) through a thin rectangular board and is supported by brackets and insulators with noncorrosive fasteners. The holes are drilled according to recognized size and spacing standards (e.g., NEMA). It is made of a conductive material such as copper, and may be plated with another metal such as nickel. TMGBs are generally designed to conform to ANSI/ TIA/EIA-607 specifications and BICSI recommendations and come in a variety of widths and lengths. Once installed, TMGBs should be labeled with warnings not to remove the structure or disconnect any of its components. Telecommunications Management Network TMN. A global network management model for Network Elements (NE) and Operation System (OS) and the interconnections between them. Global standardization provides greater incentives for common interface development. Discussions of O&M aspects

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of intelligent transmission terminals began, and TMN was first formally defined in 1988, with the recommendation for M.3010 (Principles for TMN) published in 1989, in addition to others over the next three years. OSI Management, originating in ISO, was adopted as a framework for TMN to provide transaction-oriented capabilities for operations, administration, maintenance, and provisioning (OAM&P). Elements of a TMN interface consist of various definitions, models, and profiles, including architectural definition of TMN entities, OAM&P functionality, management application and information models, resource information models, communication protocols, conformance requirements, and profiles. Telecommunications Policy, Office of OTP A government agency, established in 1970 as an Executive Office of the President during Richard M. Nixon’s administration. The OTP evolved from the 1968 President’s Task Force on Telecommunications Policy. Clay T. (Tom) Whitehead was the first OTP Director. Some of the staff were taken from the earlier Office of Telecommunications Management (OTM). The OTP was rolled into the U.S. National Telecommunications and Information Administration in 1978 resulting from reorganization. Telecommunications Policy, President’s Task Force on A significant milestone in telecommunications policy development which came about partly because of controversies regarding cable and long distance services. The Task Force was established in 1968 during the term of President Lyndon B. Johnson. Some of the important outcomes of Task Force research included the establishment of a government agency to deal with telecommunications policy and increased emphasis on competition and deregulation. Telecommunications Policy Research Conference TPRC An annual forum, first convened in 1972 as the OTP conference, for public and private sector scholars and decision-makers to discuss recent empirical and theoretical research and the needs of the telecommunications industry. See Telecommunications Policy, Office of. http://www.tprc.org/ Telecommunications Reform Act An act by the U.S. government opening up local and long distance markets to competition. The act included a highly controversial provision called the Communications Decency Act (CDA) which was, after a great deal of discussion and input from the Internet community, declared unconstitutional. The Reform Act significantly altered regulations of the telecommunications industry. Telecommunications Regulatory Email Grapevine TREG. An informal organization that carries on regular online discussions about real world issues associated with taking products and services through the various regulatory processes. This self-help group answers queries and shares experiences, archiving the information on the Web. telecommunications relay service A 24-hour telephone service to assist hearing impaired individuals

to intercommunicate and to communicate with hearing subscribers. This service may have a variety of telebraille, TTY, and voice options. In general, the subscriber calls a telephone agent, who intercepts the call, translates it, and relays it to the callee on behalf of the caller. The calls and call content are confidential. Telecommunications Research Establishment TRE. A once-secret facility at Malvern where communications research such as radar research was conducted during World War II. The TRE was established in 1940, evolving from the Ministry of Aircraft Production Research Establishment (MAPRE). Some of the early research in digital storage devices was carried out here towards the end of World War II. Many of the researchers at this facility made significant scientific achievements in a number of fields including radio astronomy. See Small Scale Experimental Machine. telecommunications service This is defined in the Telecommunications Act of 1996 and published by the Federal Communications Commission (FCC), as “... the offering of telecommunications for a fee directly to the public, or to such classes of users as to be effectively available directly to the public, regardless of the facilities used.” See Federal Communications Commission, Telecommunications Act of 1996. Telecommunications Service Priority TSP. A program of the Federal Communications Commission (FCC) for identifying and prioritizing telecommunications services that support national security and/ or emergency preparedness (NS/EP) missions. The TSP regulates, administers and operates priority restoration and provisioning of qualified NS/EP telecommunications services to support emergency readiness and response to local, national, or international events or crises that might harm Americans or their property. http://tsp.ncs.gov/ Telecommunication Standardization Bureau TSB. The TSB provides support for the standardization sector of the International Telecommunication Union (ITU-T). As such, it helps to coordinate the work of the ITU-T, provides secretarial services, assists in diffusing information, and ensures the publication of various references developed as a result of the work of the ITU-T. See International Telecommunication Union. Telecommunications Standards Advisory Council of Canada TSACC. A Canadian industry-government alliance formed in 1991 to develop strategies for Canadian and international standardization in information technology and telecommunications. Information on telecommunications technologies is provided on their Web site. http://www.tsacc.ic.gc.ca/ Telecommunications Technology Association TTA. Established by the Korean Ministry of Communication in 1988, beginning operations in 1992. http://www.tta.or.kr/ telecommuting Virtual commuting to the work site, that is, communicating through various telecommu-

nications methods instead of physically traveling to the work site. A number of factors have contributed to the increasing desire for, and availability of, telecommuting jobs: increasing congestion in cities causing higher housing costs and less availability of housing; increased traffic congestion; more families with two working parents who don’t want to leave children unattended; improved telecommunications services, with faster and better transmission, more hookup services through phone lines, and videoconferencing options. Telecommuting is not for everyone; many people prefer to work under direction or to work in close physical proximity to co-workers, but many work better undisturbed and will use the time saved by not commuting to produce a higher-quality product. There are also increasing numbers of businesses willing to provide telework options so that they can recruit highly skilled workers from diverse regions. See telework, virtual office. telecomputer, computerTV A TV broadcast system-computer integrated system that allows a user to control program selection or menu options for viewing, such as split screen for more than one show, digital effects, sound options, integration of TV and phone (e.g., on-screen Caller ID on the TV when the phone rings), email and Web access, shopping from home, etc. This is an example of the convergence of the computer and broadcast industries. Standards for ATM for the home are being promoted so that standardized commercial consumer systems can be developed which allow these many technologies to link and work together. See Broadband Residential, fiber to the home, Home Area Network, WebTV. teleconference A telephone conference where three or more participants share in a conversation. Conference call buttons or codes are available on some local multiline systems, and operators can set up conference calls across public lines for participants who are distant from one another. See videoconference. telecopier See facsimile machine. teledensity A measure of the number of telephone lines per 100 POPs (individual people) used to assess service distribution, economic compromises, revenues, etc. Teledesic A privately owned constellation of literally hundreds of satellites orbiting at 700 km (LEO) designed to provide switched broadband bidirectional network services, including Internet access, data, voice, videoconferencing, and interactive multimedia. It is designed to operate at up to 64 Mbps for downlink and up to 2 Mbps for uplink. The top transmissions speed is more than 2000 times faster than standard modems operating over wired phone lines. Connection is through small parabolic antennas. The Teledesic group approached the Federal Communications Commission (FCC) in 1994 for a 500MHz frequency allocation within the Ka-band for this service. In May 1998, Motorola Inc. joined the venture as the prime contractor, bringing in its Celestri technology,

along with Boeing Company and Matra Marconi Space, a European satellite manufacturer. Teledesic LLC is a McCaw/Gates company scheduled to begin launching in the early 2000s and to be in service by 2005. TeleDirectory A telephone directory service from British Telecom for personal computer users who have a frequent need for directory assistance services (e.g., five or more numbers per day) and wish to access the number online. Enquiries are billed on a pernumber basis. See BT Phonebase. Telefunken A German radio station founded in 1903 soon after Marconi’s wireless demonstrations in London, England, excited the imaginations of radio experimenters and future broadcasters. telegaming Gaming over a distance communications medium (telephone, computer network, postal service). Telegaming has been around for a long time. For centuries, people have played long distance chess and backgammon games by messenger and, more recently, by mail or phone. Currently it implies an unbroken connection, since that is now possible through computer networks and games like chess and go are routinely played on the Internet. Video arcade games are played on local networks, usually on an Ethernet link, although the term telegaming doesn’t apply as well to an activity in which the participants can see or hear one another in the same or next room. telegenic Having characteristics that appeal to television audiences, such as charisma, talent, humor, relevance (news), or other qualities favored by broadcast networks and viewing audiences. telegram Originally telegramme (France, 1793). A printed record of a telegraphic communication. Early telegraph signals were transcribed on paper tape as wiggly lines; later, audible signals were interpreted by human operators and written down by hand; and, finally, devices that could interpret the signals into text and impress them on paper as telegrams were devised. For decades the telegram was delivered into the hands of the intended receiver or at least brought to the doorstep. Courier services and facsimile machines are superseding telegram services. See telegraph system, teletypewriter. telegraph fire alarm That telegraph signals could be used to report fires through signal boxes was realized not long after the invention of the telegraph, and many of the larger communities installed this type of safety system by the early 1900s. The Boston Fire Alarm system was one of the first, following a published description of its feasibility by William F. Channing in 1845. Later, with the help of a telegraph engineer, Moses G. Farmer, Channing supervised the 1851 city funding and 1852 construction of the first fire alarm telegraph in the world. Originally based on manual crank boxes, painted black, the mechanisms were later changed to pull switches, and eventually dials. By 1881, the fire boxes were changed to red. telegraph history The telegraph was a system of equipment and coding that enabled communication over distance, originally through signal towers, and

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later by wires powered by high-intensity batteries. As with many technologies, the telegraph was invented in a number of places at about the same time, and many of the early models were never practically or commercially implemented. Lesage had created a frictional telegraph as early as 1774, and A. Ampère and P. Barlow proposed early designs as well. J. Munro reports that someone identified only as C.M. described an electric telegraph in Scots Magazine in February 1753 that suggested a multiwire system (similar to those later implemented by Campillo in Spain and Sömmering in Germany). Samuel T. von Sömmering created a 35-wire telegraph based upon electrochemical concepts which, in turn, was derived from the work of Francesc Salvà i Campillo in Spain, in 1795. One of the first practical commercial implementations of the telegraph was in 1837 by C. Wheatstone and W. Cooke in England. The telegraph in America owed much of its design and development to Samuel Morse and Alfred Vail. Morse’s original telegraph caveat (an intention to file a patent) described a mechanism with a horizontally moved key which made corresponding zigzag marks on a moving paper tape to represent numbers, which were then looked up to find the corresponding words in a reference dictionary prepared by Morse. Vail improved on the mechanics of the key, making it move up and down instead of side-to-side, thus forming dots and dashes with breaks in between on the paper. As this system was simpler and more direct than doing a dictionary lookup, it evolved into the system now known as Morse (Vail) code. Their telegraphic invention was demonstrated to the Presidency in 1838. Morse subsequently won funding from Congress to construct a telegraph long distance line, carried out the project with assistance from Ezra Cornell, and began to spread telegraphy throughout America in the mid-1800s. Both Wheatstone and Morse received advice and encouragement on the development of telegraphic instruments from Joseph Henry in the 1830s. Morse, unfortunately, didn’t duly credit Henry’s assistance. In its simplest form, the telegraph consists of a sender (a keying device), a receiver (with a sounder or printer), and a simple code for conveying characters. Early telegraph receiving machines used paper tapes to record messages (Morse’s telegraph created a wiggly line), but operators began to recognize the slightly audible incoming clicks and could copy messages faster than a paper tape could print them, so machines were soon equipped with sounders and resonators to amplify and direct these clicks. Not surprisingly, many inventors sought ways to translate the signals into letters that could be recorded directly, as in a telegram or teletype-style printout. One of the first to succeed was David Hughes, a schoolteacher, in 1856. In America, messages were sent by shutting current on and off, while in Britain, Wheatstone introduced polar keying, a means of using polarity to convey signals. The concept of polarity is still used today in high-speed data transmissions.

In 1866, M. Loomis demonstrated that signals could be sent from one airborne kite to another, when each was strung with fine copper wire of the same length, without direct physical contact. This later lead to his 1872 U.S. patent for a wireless improved telegraphic system, although it was some time before his discoveries were put into practical use. By the 1880s, scientific investigations and demonstrations had confirmed the viability of wired and wireless telegraphy. The end of the century then became a time of creative application of the concepts and evolutionary improvements in speed and practicality.

One of the early Bell telegraph patent documents. There were many inventors at the time independently making similar discoveries, and substantial competition to be the first to patent and commercialize the new communication technologies.

In 1895 and 1896, in Russia, A.S. Popow was conducting experiments with wireless telegraphy and succeeded in sending a shipboard message to his laboratory in St. Petersburg. Unfortunately, due to the secrecy surrounding Russian naval technology and inventions in general, Popow’s discoveries were not communicated to the rest of the world, and he did not receive credit for his early experiments. In the late 1800s, telautographs that could transcribe handwriting were created by a number of inventors including E. Gray and F. Ritchie. While these remained in use for a number of decades, they didn’t originally work over long transmission lines and were superseded by telewriters and, eventually, facsimile machines. In 1886, Amos Dolbear, a Tufts University scientist and writer, was awarded a patent for a wireless telegraph based on induction. In 1889, F.G. Creed invented a High Speed Automatic Printing Telegraph System. By 1898, his Creed Printer could transmit 60 words per minute and his technology was widely sold in many countries. He broadened his enterprise in 1923 by demonstrating marine wireless printed telegraphy, a system eventually used for marine safety.

Wireless telegraphy was of interest almost from the beginning of telegraphic history. In the early 1900s, V. Poulsen and P. Pedersen used an electric arc to generate high-frequency waves, setting the groundwork for wireless communications. Poulsen also developed the telegrafon, a historic electromagnetic tape recorder. Tape recorders were later used to develop dictation and telephone answering machines. The telegraph had a revolutionary impact on communications, changing forever the concept of distance. It networked the predominantly rural early settlers of North America and spurred the installation of the first transatlantic cable, providing instant (by 1800s standards) communication with Europe. Prior to the oceanic cable, messages typically took 2 months or longer to travel in ships from one continent to the other. News, business, warfare, and family contacts were dramatically affected by the availability of fast long distance communications. See Creed, Frederick George; heliotrope; Davy, Edward; Dolbear, Amos; Morse, Samuel F.B.; Popow, Aleksandr Stepanowitsch; Salvà i Campillo, Francesc; Sömmering, Samuel Thomas; Steinheil, Karl August; telegram; telegraph system; telephone; Wheatstone, Charles.

The original telegraph key was a fairly straightforward device for opening and closing a circuit at intervals that corresponded to the dots and dashes in Morse code. [American Radio Museum collection.]

telegraph key A mechanical switch on early telegraph systems that enabled a circuit to be opened and closed in order to generate transmissions through a signal such as Morse code. telegraph signals For telegraph signals through wires, two main methods were used: polar transmission, in which the polarity was changed to reverse the current; and neutral, or open/close transmission, in which open current (space) was interspersed with no current (mark). telegraph system An apparatus for sending and/or receiving information over distance, coded in some fashion, usually in Morse code dots and dashes. A basic telegraph circuit consists of a key to translate finger or other mechanical pressure into signals, a relay sensitive to the very small current that may be coming through the wire, and a receiving device which can express the message by means of audible tones, paper tape code, or printed letters. Telegraph systems have coexisted with, rather than been superseded by, telephone systems for a number of reasons, including the expense and time delays of

setting up long distance toll calls to some areas, and the importance, in some situations, of creating a written record in the form of a telegram. With electronic telephony advancing and facsimile machines proliferating, the telegraph is becoming more historically interesting than practical. See telegraph history; telegraph, needle.

The telegraph message delivery staff of the G.N.W. Telegraph Co. in Montreal, Canada, 1900. [National Archives of Canada.]

telegraph, needle A type of five-needle telegraph devised by Charles Wheatstone and put into service in England in 1837. Faulty equipment lead to the gradual realization, by telegraph operators, that two needles were sufficient and, eventually, only one needle and one dial were used to efficiently convey messages. The needle telegraph also represents the development of polar keying, which employed positive and negative voltages for indicating mark and space signals. See polar keying.

A telegraphic map of the United States published ca. 1870 which shows the Pony Express Mail & Telegraph Route (in spite of the fact that the Pony Express was very shortlived).

telegraph, printing Early telegraph papertape and manually operated sounding systems did not satisfy the needs of inventors and users who wanted quick, automated written messages. Thus, the development

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of printing telegraphs was of interest to many. One of the first successful systems was developed by A. Vail in 1837, employing a type wheel. Later D. Hughes developed a practical working type wheel system in 1855, which became established in Europe, but didn’t catch on well in America, where Morse systems were in use. Improvements to printing telegraphs continued and, in 1846, R.E. House developed a printer that printed telegraphically transmitted letters directly. Further improvements to House’s system resulted in a patent in 1852. In 1905, Donald Murray published “Setting Type by Telegraph” in the Journal of the Institute of Electrical Engineers and went on to improve telegraphy in a number of ways. The necessity of noise-free transmissions and technical expertise to maintain the equipment prevented printing telegraphs from coming into widespread use until decades later. See teletypewriter. telegraphese A terse, abbreviated mode of messaging (or speaking) which has the character of a telegram. Since telegrams were often charged by the letter or by the word, a compact style of communication emerged in order to keep the cost as low as practical. telegraphone, telegrafon This is not only a type of telegraph instrument, but more important, was an early electromagnetic tape recorder, designed in 1898 by Danish inventor Valdemar Poulsen. Poulsen succeeded in recording electronic waves on a thin wire of steel, and improved on the technology enough to receive a U.S. patent in 1890. This developed into

dictating machines sold through the American Telegraphone Company. See tape recorder.

The telegraphone spurred innovations not only in telegraphy, but also in sound recording.

TeleLink Project The full name is TeleLink Training For Europe Project. This is a European Community (EC), Euroform-funded project which seeks to promote and develop telework training opportunities and qualification guidelines. This includes qualification level certification (currently at the vocational level) for teleworkers and a system of TeleLink centers around Europe. See ADVANCE Project, telework. telemarketing The promotion of products and services through telephone calls to individual premises. There are various regulations governing when tele-

A historic Rowland page printing telegraph system which could translate electrical impulses from a keyboard into printed characters at the receiving station. [Scientific American, October 25, 1902.]

marketers may call, whom they may call (e.g., calls to a person at his or her place of business must be stopped if the callee requests it), and what they must say to identify themselves and their affiliations. There are also restrictions on where they may obtain names, and how they must dial the call. Many scams have been perpetrated through telemarketing schemes, and it is important for the callee to get sufficient information to ascertain that the offering is legitimate. If you don’t wish further calls from the source, you should request that your name be taken off their list. See war dialer

An automatic telegraph sender. The wheels shown at the top represented characters that could be selected and placed in order to spell out a message. This example is from the American Radio Museum collection.

telemarketing broadcasts The promotion of products and services through mass market advertising usually providing a 1-800 or 1-900 number for the interested buyer to call. Automated systems for taking the caller’s name and billing information through touchtone selections are becoming prevalent. telemedicine Medical information and services and medical education provided over distance through telephone, radio, facsimile, videoconferencing, and the Internet. Information such as medical imaging results can readily be transferred as data, since much of it is digital in nature. Teaching and other communications among medical professionals and their patients are possible through newer technologies. telemetry, telemetering The art and science of gathering information at one location, usually in terms of some quantity, and transmitting that information to another location for storage, analysis, or evaluation. Weather balloon data gathering and transmission through a radiosonde to a weather station for interpretation is one example of telemetry. The transmitting of information from space probes is another. Telemetry equipment is typically included on artificial satellites to aid in the control and orientation of the satellites. Teletext A commercial computer service offered by NBC, which was discontinued in 1985. Many of these early computer services came and went, but they are coming back in updated forms now that there is a large user base drawn to the Web.

telephone A communications apparatus designed primarily to convey human voice communications. In its simplest form, a telephone consists of a transistor that converts sound into electrical impulses, and a receiver, which converts them back again into sound. Additional technology is used to amplify and direct the communication between these two basic devices. The design of the telephone set has gone through five overlapping phases in its development. See the Telephone Development Phases chart. See telephone history. telephone amplifier A device to amplify sounds at the receiving end of a call. This can be incorporated into the handset, headset, or speakerphone, or may be an add-on to provide even more amplification for the hard of hearing. Most handset telephone amplifiers draw current from the phone line, but many speakerphones and add-on amplifiers require a separate power source. The amplifier is often adjustable through a dial or slider on the side of the phone. telephone answering machine An electronic or mechanical device for answering calls and often for recording them digitally or on tape. Telephone answering machines based on reel-to-reel mechanisms have been available since the early 1960s, but small cassette and digital answering machines did not become common until the late 1970s and early 1980s. Most households now have answering machines to respond to calls, take messages, or screen calls. Many of these will include information on the time and date of the call, and some will record the identity of the caller, if Caller ID is activated on the subscriber line. Computer voicemail applications can also be hooked to a phone line through a data/fax/voice modem to allow the software to function as a full-featured answering machine with multiple mailboxes. telephone answering service 1. A service offered by commercial vendors in which a human operator or voice-automated system will answer the subscriber’s phone line when it is call forwarded, or when the answering service number is called directly and forwards the message to the subscriber. This service is widely used by small businesses, freelancers, and real estate agents. Sometimes these services are combined with paging. 2. A service offered by local phone companies in which a human operator or voice-automated system will take calls and forward messages to the subscriber, or through which the subscriber can use a touchtone phone to retrieve messages. telephone central office See central office. telephone circuit An electrical connection consisting minimally of a transmitter, receiver, amplifier, and connecting wires, and more commonly comprising a system of two-way audio and signaling connections between local exchanges and subscriber lines and telephones. Telephone Company of Prince Edward Island A historic telephone exchange, incorporated in 1885, the year after the phone exchange was first established on the island.

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telephone exchange Switching center for telephone circuits. See central office, private branch exchange.

discovery, terming the sound “galvanic music.” Subsequently, a number of inventors advanced telegraphic and microphonic technologies leading up to the invention of the telephone. Belgian inventor Charles Bourseul described his idea for transmitting tones in 1854, but wasn’t able to implement a fully working version before Philip Reis and Alexander Graham Bell developed their own telephonic devices. Reis first demonstrated the transmission of tones through wire in Frankfurt in 1861. He reported in a letter that he could transmit words, but there is no direct way to verify the claim.

The earliest telephone looked more like a pinhole camera than current familiar desktop phones and mobile handset phones.

telephone history The telephone was a significant evolutionary development, occurring a few decades after the invention of the telegraph. While the telegraph revolutionized telecommunications by making communications over great distances possible, the telephone personalized it, and many inventors were excited by the potential of sending tones, or even voice, over phone lines. The use of tubes and strings to magnify sound and channel acoustic vibrations existed at least as early as the time of Robert Hooke, long before the development of modern telephones, but such devices, like the acoustic tubes demonstrated in 1682 by Dom Gauthey, were physically limited as to loudness and distance. It was not until electricity and magnetism were harnessed that amplified, long-distance modern telephony was possible. In the early 1800s, German inventor Philip Reis observed that a magnetized iron bar could be made to emit sound. In America, Charles Page made a similar

An innovative optic telephone, based on the stimulation through a diaphragm of a flame from an acetylene burner. The impulses were then further transmitted optically through a light-sensitive selenium cell and reflector. The optic telephone was developed by Ernst Ruhmer, and was used for long distance communications. [Scientific American, November 1, 1902.]

Around the time of Reis’s death, an American physicist, Elisha Gray, was making numerous experiments

Except for the very earliest experimental models, the essential mechanical design of the dial telephone hasn’t significantly changed in about 60 years, but a number of cosmetic updates have occurred over time.

in telegraphy and developed early concepts for harmonic telegraphy, the transmission of tones, and telephony. In the mid-1800s, Italian-born Antonia Meucci was successfully experimenting with wires attached to animal membranes to transfer sound through current, but news of his significant discoveries did not become widely known outside Cuba. When he later emigrated to the U.S., he filed a caveat for a patent, in December 1871, for a teletrofono.

Here Alexander Graham Bell demonstrates his telephone invention. The inset shows one of his early sketches of the invention, from the famous Bell notebooks. Bell achieved great financial success from commercializing his discoveries.

The better-known precursors to the telephone in America and later variations appear to have been

invented more-or-less independently by Elisha Gray and Alexander Graham Bell, but Bell filed his telephone patent (it was actually a precursor to the telephone, a harmonic telegraph) a few hours before Gray filed a caveat (intention to file within 3 months) in February 1876. The murky history of the invention of the telephone at this point stems in part from the fact that many innovations were being developed simultaneously and also because the inventors understood the great commercial potential of their devices. Hundreds of lawsuits were threatened and filed over the next few decades, although some claims were more amicably settled. For example, in January 1877, Bell wrote to Gray rescinding any previous accusations he may have made that Gray copied from Bell’s work. (In fact, both men may have copied from a third source, Antonia Meucci. It has been suggested, but not confirmed, that both Bell and Gray had access to Meucci’s teletrofono documents when they were in the hands of Western Union.) Emil Berliner was an inventor with a strong interest in music and the improvement of the quality of transmission of sound (which applied equally well to telephony). In April 1877, he filed a caveat for a patent for a telephone transmitter, three and a half months before Thomas Edison applied for a patent for a similar device. In a 1911 lecture on the origins of the membrane telephone, Bell described how he worked out the idea in discussions with his father while on a family visit in Canada in the summer of 1874, 2 years before it was successfully implemented. Bell and Watson reported that Bell first spoke intelligibly over wires in March 1876. The transmission succeeded by use of a liquid medium, something not mentioned in Bell’s

Overview of Telephone Development Phases Type

Time period

Notes

original invention

late 1800s

hand crank phones

late 1800s, early 1900s

dial phones

early 1900s to 1980s

touchtone phones

late 1970s to present

digital phones

early 1990s to present

Proof of concept, the first discernible, intelligible human voices can be heard over distances. Phones were large, to accommodate a battery, and had to be cranked to send a ringing current. Hand-crank phones were still in use in rural areas, including some of the San Juan Islands in the 1960s. Common batteries and automatic switching systems made it possible to create smaller, line-powered phones and rotary dials so the subscriber could direct dial a local call, and later, long-distance calls. Phones that sent tones rather than pulses through the line, which were interpreted according to pitch. This made automated menu-controlled systems possible. Interface speakers or headsets that attach directly to a computing device or desktop system as peripherals to enable the user to talk into a digitizing program which samples the sound and transmits it over public data networks.

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patent. This voice capability was not publicly demonstrated until some time later, which seems odd given the magnitude of the reported achievement. Ironically, Bell had been discouraged by investors from trying to make a talking telegraph and was prodded to concentrate on a harmonic telegraph instead. Gray had publicly demonstrated rudimentary telephone-related technology before the Bell patent was filed, and later successfully earned a number of telephone-related patents. He designed a telephone in the 1870s not unlike the second-generation switch-hook phones that employed separate ear and mouth pieces which came into use in later years.

the late 1920s and demonstrated the early technology to the Institute of Radio Engineers in 1956, but it was not until 1964 that a practical experimental system was completed and the Picturephone was exhibited cooperatively by Bell and the American Telephone and Telegraph Company (AT&T) at the New York World’s Fair. Currently many companies are scrambling to be the first to get a cheap, publicly accepted version of a picture telephone or as they are known now, audiographics systems, videophones, or videoconferencing systems. With the growth of the Internet and the drop in price of small video cameras, they began to be common computer peripherals in 2002.

A portion of a letter from Elisha Gray to Alexander Graham Bell on Western Electric stationery, announcing a lecture on the telephone as Gray had developed it. [Library of Congress Alexander Graham Bell Family Papers Collection, February 21, 1877.]

The first commercial telephone exchange was established in Connecticut, U.S., and became operational in 1878. It was followed the same year by the second commercial exchange in Ontario, Canada. The Bell patents formed the basis of the early Bell System in the United States, a company that has influenced the development of communications, and thus the course of history, in countless important ways. The Bell Telephone Company of Canada was incorporated in 1880. By this time, telephone technology began to spread to other nations outside Europe and North America. The first telephone exchange was established in Japan in 1890 in the Tokyo/Yokohama region. In 1926, automatic step-by-step switches were introduced in Japan. The most interesting evolutionary step in telephone technology, besides the growth of wireless communications, is probably the videophone, descended from early picture telephones such as the Picturephone. The Bell Labs were transmitting pictures in

A postcard from approximately 1920 commemorating the “Birthplace of the Telephone,” the top floor of 109 Court Street, Boston, Massachusetts. [Library of Congress Detroit Publishing Company Collection. Copyright expired by date.]

Another significant change in telephony has been the sending of voice over computer networks by means of a specialized handset attached to a computer. This permits the connection of long distance calls world round without any long distance toll fees. The technology threatens to dramatically change the established economic structure of the telephone system, and it is difficult to predict whether the same revenue-generating model that has worked for about 100 years will be viable in the future, given the current rate of change. In fact, some of the long distance carriers, worried by this threat to their survival, have lobbied for this type of transmission to be blocked. See Bell, Alexander Graham; Berliner, Emil;

Bourseul, Charles; Callender switch; Gray, Elisha; Meucci, Antonio; Reis, Philip. See telegraph history which has a common ancestry and additional details. telephone landline density A measure of the number of installed phone lines per 100 people. telephone pickup Any of several devices for connecting into an ongoing telephone conversation, usually for monitoring purposes. Telephone Pioneers of America TPA. A nonprofit organization founded in 1911, with chapters throughout the United States and Canada. Originally consisting of telephone pioneers with 25 years of service or more, with Theodore N. Vail as its first president, membership later opened up to a wider group, now numbering almost 100,000, as fewer pioneers remained from the original group. TPA engages in a number of community-oriented activities, with a particular focus on education. A somewhat analogous organization serving non-Bell employees is the Independent Pioneers. http://www.telephone-pioneers.org/ telephone receiver The portion of a handset, headset, or speakerphone which converts electrical impulses into sound. On a handset, the receiver is the part that you hold up to your ear. Inside a basic traditional receiver is a magnet, with coils wound around the poles connected in series and a light, thin, vibrating diaphragm mounted very close to the magnet poles. When current passes through the coils, the diaphragm vibrates, producing sound by moving the air next to it. Early receivers used a bar magnet, which later was replaced by a horseshoe magnet. See telephone transmitter. Telephone Relay Service A telephone service enabling handicapped individuals to communicate over telephones through third party interpreters. It is usually provided free of charge. telephone repeater An amplification device em-

ployed on telephone circuits to rebuild and maintain signals across distances, which otherwise would be subject to loss. telephone signaling Any device that indicates an incoming call, usually a bell, but may also be a light or moving indicator. telephone switchboard A centralized distribution point for managing telephone calls. Early switchboards consisted of a human operator answering calls, and plugging a large physical jack into the receptacle of the person to whom the call was being patched. The first commercial switchboard in North America went into operation in Connecticut in 1878. Switches were mechanized in the mid-1900s, although it was not uncommon for human switchboard operators to staff manual switchboards in rural areas and private branches until the 1950s. Although mechanical switching stations still exist, updated switchboards function electronically. telephone tag Colloquial phrase for two parties attempting to contact one another by phone, not reaching the other person, and leaving messages with an answering machine, operator, or voice mail system. Doing this back and forth a few times is telephone tag. telephone transmitter The portion of a handset, headset, or speakerphone which converts sound into electrical impulses. On a traditional handset, the receiver circuit connects to the part that you hold next to your mouth. Inside the mouthpiece is a movable diaphragm with an attached carbon electrode, behind which another carbon electrode is fastened securely inside the housing. Between the electrodes are carbon granules (it’s possible to build a simple phone transmitter using the core of a carbon pencil laid across two conducting surfaces connected to wires and a diaphragm). When a current is applied, resistance decreases, as a result of the carbon granules

A schematic for a historic semiautomatic telephone switching system (it still required a human operator to turn a spring-loaded knob to send the dial pulses through the wire). [Scientific American, October 11, 1902.]

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compressing more closely together. Thus the current increases and attracts the diaphragm more strongly. The diaphragm vibrates to produce an electrical impulse that corresponds to the movement of air caused by the speaker’s voice. An induction coil may also be used to increase the voltage to compensate for signal loss through the transmissions medium. See Blake transmitter, coherer, telephone, telephone receiver. telephone user interface TUI. The use of telephone equipment, usually a handset or headset or telephone line attached to a peripheral card, to interact with computer software. Instead of using a keyboard and mouse as the input devices, voice or touchtones over the handset or phone line are used to control the actions of the computer. For example, you may have a computer set up like an answering machine to answer calls, respond to callers, and log time, date, and caller messages. Then, from a remote location, you may call the line attached to the computer, and by speaking or pressing touchtone buttons, have the computer send back information about the calls or replay the calls. telephony The science and practice of transmitting audio communications over distance, that is, over a greater distance than these communications could be transmitted without technological aid. The term has broadened from audio communications to encompass a wide variety of media, typically now including visual communications that accompany sound communications (as in audiographics and videoconferencing), although it is preferred that the more general term telecommunication be used for audio/visual transmissions. Most telephony occurs over wires, but wireless services transmitted by radio waves and satellite links are increasing. Telephony, in its simplest sense, is not a high bandwidth application; each conversation requires only a narrow channel, but because of its continuous bidirectional nature, bandwidth needs increase as the number of simultaneous calls increases. Traditional telephony media, such as copper wires, are no longer strictly used for oral communications; they now service a large number of data transmission services such as Internet connectivity, facsimile transmission, and more. Due to increased demands for lines with greater speed and accuracy than are needed for simple voice transmissions, fiber and coaxial technologies are being used to upgrade data lines and, consequently, the phone lines. See HFC, telephone, telegraph. Telephony Application Interface TAPI. A standardized telephone interface developed by Microsoft and Intel Corporation for the creation of a variety of device-supporting software applications. TAPI can be used to create call control software for telephony devices for computerizing common functions and sought-after features. As an example, TAPI can be used to create a Caller ID-type function on a computer, with the computer answering a Caller ID-enabled phone line, assessing the Caller ID information, and perhaps relating it to a database of names or other information associated with the number and

logging the call or notifying the user of the call. Since not all phone systems are equipped with TAPI interfaces, there are now third parties, such as Ryan Technologies, that provide protocol conversion modules that enable TAPI-based applications to link through the module to the phone system. In 1999, Siemens extended the utility of TAPI by introducing a TAPI interface compatible with a national ISDN terminal. This, in conjunction with the Optiset phone, turns a computer into a powerful telephony terminal. See Telephony Services Application Programming Interface. Telephony Routing over IP TRIP. A policy-driven inter-administrative domain protocol for routing voice-over-Internet calls, developed by the IETF IP Telephony (iptel) working group. TRIP is independent of the signaling protocol used. It uses Border Gateway Protocol (BGP-4) to distribute routing information between administrative domains. It thus enables digital telephony calls to be routed between digital network domains and supports the exchange of routing information between providers, thus building up a forwarding information base. In August 2001, TRIP was published as an Internet Draft and, in September 2001, was submitted to the IESG for consideration as a proposed standard. TRIP may also be a part of future protocols for the propagation of routing information between gateways and their associated signaling servers (a process called gateway registration). Telephony Services Application Programming Interface TSAPI. A set of guidelines developed by a group of developers, including Novell, Inc. and AT&T, for interconnecting corporate telephone systems into the data network server in medium and large business networks. The specification describes the physical link that can be used to implement software-based call control from a private branch exchange (PBX) switch, for example, so that control is handled from the originating point in the local area telephone network. Thus, TAPI’s call tracking capabilities make it more powerful and suitable for enterprise environments than the more desktop-oriented Telephony Application Interface (TAPI). See Telephony Application Interface. telephoto, telephotography Visual information conveyed through conventional photographs or digital photographs from data received remotely. Journalists, geographers, navigators, and others use telephotos to send or receive visual information from remote sources through wired or wireless communications, and to print them in various resolutions through photographic, laser, or other means. Satellite photos of the Earth’s surface are extremely popular examples of telephotos. Many of the images now printed in national newspapers are telephotos sent through wireless modems by journalists using digital cameras and laptops. Teleport Communications Group TCG. At one time, a national competitive local telecommunications provider with fiber optic SONET networks in over 50 large markets, acquired in early 1998 by AT&T.

teleprinter 1. Teletypewriter. 2. A Western Union trade name for printing telegraph terminals. See telex. TelePrompt Project A European Community (EC) project funded by a consortium of academic and commercial groups designed to develop and further technology-based distance learning resources for European teleworkers. The term teleworking in Europe is roughly equivalent to the term telecommuting in North America. teleran An aerial navigational guidance system employing information received through television waves and radar transmitted to aircraft by ground stations. TELESA See Telecom Services Association of Japan. telesales A British term for telemarketing. See telemarketing. Teletype A name trademarked by Teletype Corporation for a variety of teleprinting devices used in communications. See teletypewriter. Teletype Corporation An early printing telegraph company, the Morkrum-Kleinschmidt Corporation, which was acquired in 1930 by the Bell System and renamed Teletype Corporation. teletypesetter A machine for remotely controlling typesetting machines. When these were originally

put into service, teletype machines relied on a fiveunit code that was insufficient to transmit all the characters needed by a similar teletypesetting machine. Thus, a six-unit signal code was developed for teletypesetters to increase the size of the character set from 32 to 64. teletypewriter TTY. A printing apparatus which, in its common form, resembles a typewriter on a pedestal with continuous feed or tractor feed paper so that it can print unattended. Sometimes it is used to send and receive signals over phone lines and for transmitting messages or computer data in text form. The teletypewriter superseded key and sound telegraph systems because it could operate unattended and achieve transmission speeds of 60 to 100 words per minute. The earliest teletype-style printers and start-stop synchronization methods were developed by Charles and Howard Krum. See Baudot code; Krum, Charles and Howard; telegraph, printing; Teletype; telex. teletypewriter code A five-unit code that employs elements of uniform length. Start and stop pulses are used to distinguish each character in the transmissions. See Baudot code. teletypewriter exchange service Any commercial service which provides teletypewriter communications sending and receiving services through a

Common Television Broadcast Formats Abbrev.

Name

Notes

NTSC

National Televisions Systems Committee

The North American standard since the 1950s. 525 vertical lines. NTSC uses negative video modulation and FM sound.

PAL

Phase Alternate Line

The predominant standard in the United Kingdom and parts of Western Europe since the early 1960s. 625 vertical lines. There are a number of variations of the PAL system, including PAL-B, PAL-H, PAL-M, etc. PAL uses negative video modulation and FM sound.

SECAM

Sequential Color and Memory

Developed in France and used in North Africa, Russia, and parts of Europe since the early 1960s. 625 vertical lines. There are a number of variations of the SECAM format, including SECAM-B, SECAM-H, etc.

HDTV

High Definition Television

Introduced in Japan and proposed as a global standard, but not readily adopted by American and other manufacturers, some of whom would prefer to enhance current standards rather than adopt a new one. 1125 vertical lines at 60 frames per second. HDTV is supported by some Internet push channels and can be viewed with an interface peripheral and a computer with a fast connection.

C-MAC

Multiplexed Analog Components

Developed in the U.K. and recommended by the EBU as a European standard.

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switching exchange. Similar in concept to a long distance telephone exchange. TWX is one such service of the Bell System, established in 1931, subsequently owned by AT&T. See Telex. television TV. A system of sending and receiving broadcast moving images (even if the object in the transmission isn’t moving), usually in conjunction with sound, although some closed-circuit television systems don’t include sound circuitry. Television broadcasts can be transmitted through air or over cables, with cable TV (CATV) increasing in popularity. Air transmissions are captured with a television antenna designed for a portion of the broadcast spectrum (although three-in-one antennas exist for UHF, VHF, and FM signals). At the receiving end, a television set (tuner and monitor combined), or a VCR tuner and monitor are typically used to display the broadcast. television broadcast band The various frequencies which are assigned and regulated for television broadcast transmissions. Due to the proliferation of programming and the increased availability of access through satellite transmissions, there is constant pressure to increase available frequencies and channels, and hundreds of programming channels are now available. See band allocations for a chart. television camera A lens-equipped, optical-sensing pickup device designed to capture moving images and transmit or pass them on to receiving, editing, and broadcast equipment. The type of signal generated by the camera varies according to the receiving or editing equipment, and varies from country to country. Television cameras have traditionally been expensive, large, heavy, analog, high-resolution apparatuses. This is all changing, with small handheld digital and analog personal cameras beginning to rival the quality of traditional TV cameras for only a fraction of the price. See NTSC, PAL, SECAM.

A tiny television camera, not much bigger than a human hand, designed in the days when television cameras were large and heavy. The technology was designed for the demanding task of space observation and very long-distance communications by the Marshall Space Flight Center. Similar cameras were quickly adapted for commercial telecommunications. [NASA/Marshall Space Flight Center image detail, date unknown.]

television history Television, perhaps more than any other of the major communications technologies, arose in fits and starts in the late 1800s with many geographically diverse announcements of success and few demonstrated working systems. One of the important discoveries in the history of television was the photoconductive characteristics of selenium, which responded to the amount of light hitting the surface. A French researcher, M. Senlacq, suggested in 1878 that selenium might be used to register the shapes of dark and light areas on documents. British researcher Shelford Bidwell was able to successfully transmit silhouettes by 1881, and the now famous German inventor, Paul Nipkow, after whom the Nipkow disc is named, patented an electromechanical television system in 1884. But the transmission of moving images and shades of gray in high enough resolutions to be practical eluded the early inventors. Although patents for television-related technologies began to appear in the late 1800s, it was not until the 1920s that television transmission and reception as we know it was demonstrated by inventors such as John L. Baird in the west and Kenjito Takayanagi in Asia. Baird’s first significant success was in 1926, the same year Tekayanagi transmitted Japanese script with a cathode-ray tube. In the U.S., a precocious 15-year-old, Philo T. Farnsworth, described an idea for a television to his schoolmates and reportedly showed a sketch to his teacher in 1922. In 1927 he succeeded in building a working model. Experimental television stations sprang up in the late 1920s and, by the mid-1930s, regular public broadcasting began to develop. In Europe, television images were being transmitted by 1931. Television sets were available by the late 1930s, but it was a while before the technology became cheap enough for home use. By the late 1940s, there were at least 20 broadcast stations in North America, with hundreds of hopefuls clamoring for the limited licenses. Black and white televisions came into widespread use in the 1950s in North America and color television was common about 15 years later. By the mid1980s, melon-sized portable televisions became inexpensive and wrist-sized consumer TVs had been developed. Commercial sponsorship provides much of the funding for television in North America, thus controlling, to some extent, the type of programming which is available, influenced by majority consumer demand or perceived viewer preferences. In many other countries, television is funded and controlled by local governments. The next major step in television broadcasting was the launching of communications satellites such as the Telstar 2 in 1962 which permitted intercontinental communication. Commercial application of satellite television broadcasting was pioneered by the Canadian Broadcasting Corporation through the ANIK satellite in 1972, followed in the late 1970s by Turner and the Public Broadcasting System (PBS) in the U.S.

In North America, satellite television broadcasts can now be received by consumers on small parabolic dishes that are served by monthly subscription services, with hundreds of potential stations available. Television is widely used for mass-media entertainment, education, distance monitoring, and local security monitoring. The influence of television on world culture is significant and substantial, with a preponderance of the programming originating in the United States. Thus, the role models depicted through television programming and advertising sponsors have a strong effect on viewers, and implicitly promote American values, styles of dress, and cultural priorities to all parts of the globe. See Baird, John Logie; Farnsworth, Philo T.; Nipkow, Paul Gottlieb; Nipkow disc; Takayanagi, Kenjito; television; television camera; Zworykin, Vladimir. television relay A station designed to pass on a television broadcast signal to the next station so the signal is protected from loss. The relayed signal is not intended for reception by viewers until it reaches the destination station. television signal The coding of images can be accomplished in a number of ways, and there are several standards, each of which is preferred in a different part of the world. Common formats related to the broadcast and display of moving image signals are shown in the Common Broadcast Formats chart. telework Work at home or at satellite locations made possible through computer and telecommunications technologies. In 1988, Jack M. Nilles proposed a broad definition of telework as “... all work-related substitutions of telecommunications and related information technologies for travel,” thus, employer/ employee interactions across distance through new technologies. This term is more common in Europe and is roughly equivalent to the term telecommuting in North America. See ADVANCE Project, European Community Telework Forum, TelePrompt Project. telex teleprinter exchange. Generic term for a communications service developed near the end of the second world war that uses teletypewriters to transmit through wire lines and automatic exchanges to produce a written message at the destination. In Europe, this technology used audio frequencies over phone lines. See Baudot code, Telex, Western Union. Telex A global message service established in the United States by Western Union in the early 1960s. This was competitive with AT&T’s TWX service. Telkes, Maria A physicist who did pioneer work in the development of solar energy in the early part of the 20th century. Solar energy has subsequently become an extremely important power source for orbiting communications satellites. Telnet Protocol A widely supported 8-bit, byte-oriented network protocol for remote terminal access, originating from the days of the ARPANET. Telnet allows the user to log on to another system through a TCP/IP network, and perform file functions and other activities. Telnet is spelled in lowercase when

used as a command to launch a remote utility that uses the Telnet Protocol. The form of the Telnet command is: telnet [IP_address|host_name][port] (with the command entered in lower case). A sample Telnet session looks like this: abiogen@mycomputer: /1.2GB/users/ abiogen $ telnet remotecomputer Trying 192.42.172.20... Connected to remotecomputer. Escape character is ‘^]’. NeXT Mach (remotecomputer) (ttyp0) login: myname Password: bash$ ls -la ... bash$ logout Connection closed by foreign host. abiogen@mycomputer: /1.2GB/users/ abiogen $ See RFC 318, RFC 854, RFC 855 to RFC 861 (various options).

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The Telstar 3-D satellite being put into Earth orbit from the payload bay of the Space Shuttle Discovery in the mid-1980s. [NASA/JSC image detail.]

TELSTAR 1 A historically significant low-altitude communications satellite that broadcast microwave transmissions and tracked satellites in the 1960s. This AT&T endeavor is claimed to be the first active communications satellite, launched 10 July 1962 by the United States, although some RCA engineers launched a transmissions satellite earlier. It is the first transponder-equipped satellite. Prior to this, satellites were passive transmitters, but the use of transponders for amplifying the signals was preferred from this time on, and some satellites now include as many

as ten transponders. The TELSTAR had some early problems that were fixed in 1962; it ceased functioning in 1963. By 1964, two more TELSTAR satellites had been successfully launched and TELSTAR 3-D was launched in the mid-1980s. tem wave transverse electromagnetic wave. template 1. A pattern, guide, table, or mold used to provide the basic configuration, format, or design for creating a new version, or multiple versions of a project with few or no changes. A template is intended to save time by automating the creation of new versions. A word processing template can be used to set up documents which are reissued frequently with only minor changes (e.g., form letters). Temporary Mobile Station Identifier TMSI. A dynamically assigned mobile station identifier (MSID). TENET See Texas Educational Network. tensile strength A descriptor for the greatest amount of longitudinal stress that can be borne by a particular material before it will rip apart. The units used to describe this property vary from industry to industry. It is an important factor in many manufacturing and industrial applications. tera- T. A prefix for an SI unit quantity of 1012, or 1,000,000,000,000. It’s a trillion, a very large quantity, but considering there are now hard drives with terabytes of storage space, it’s not as big as it used to be. It comes from the Greek root terat or teras meaning “monster.” See peta-, pico-. TERENA Trans-European Research and Education Networking Association. A European network evolving from the European Academic and Research Network (EARN) and the Réseaux Associés pour la Recherche Européenne (RARE). TERENA was established from the merger of these organizations in 1994 to promote and participate in the high quality international information infrastructures to benefit research and education. TERENA includes members from more than three dozen countries, as well as a number of high-profile computer developers/vendors, and the CERN and ACMWF international treaty organizations. TERENA has been responsible for BITNET support in Europe including data collection and the distribution of nodes and routing tables. See BITNET. terminal 1. An endpoint, extremity. 2. A conducting device, often a small metal post or receptacle, provided for facilitating a good electrical connection. 3. A device or system which provides remote access to a central computer. 4. An endpoint in a communications line, or one which can be, but is not necessarily, extended to other circuits. Terminal Adapter TA. A device available in various configurations from a number of vendors, which provides protocol adaptation and interfacing with an ISDN line. A TA enables a variety of consumer electronic products such as computers, fax machines, etc. to connect to the ISDN service. Terminal Endpoint Identifier TEI. An identifier for distinguishing between several different devices using the same ISDN transmission links. Values may

be dynamically assigned to TEIs ranging from 0 to 126. Fixed TEIs are assigned values between 0 and 63. The value of 127 is reserved for TEI broadcast, which aids in carrying out management functions. An ISDN device must be assigned at lease one unique TEI value, either by preassignment or dynamically, by the local exchange, as needed (sometimes called Auto TEI). The TEI Management Protocol is used to dynamically assign values in a request/response interaction. Dynamic allocation is usually used on point-to-multipoint links but may be used on point-to-point links terminating office In a transmission such as a phone call or telegraph message, the terminating office is the switching center which is the final one that connects directly to the subscriber line or other receiver of the communications. In Internet dialup communications, the local ISP would be considered the terminating office. TERMITE A terminology database which contains all terms appearing in printed glossaries of the International Telecommunication Union (ITU) since 1980, contributed by a variety of industry professionals, including technical editors and translators. English, French, Spanish, and Russian source terms are included. Access to the database is available through Telecom Information Exchange Services (TIES). ITU activities are now also being archived in this database. http://www.itu.int/search/wais/Termite/ Terrestrial Digital Service TDS. A commercial private digital data transmission service offered by MCI to subscribers over local exchange carrier (LEC) T1, DS-3 systems. Thus, customers would have fast transmission links to MCI Services. There was some debate over this service option through the Federal Communications Commission (FCC). TESC Technology Subcommittee. tesla A meter-kilogram-second unit of magnetic flux density equivalent to one weber per square meter. Named after Nikola Tesla. Tesla coil An air-core transformer for creating highvoltage discharges at very high frequencies. Tesla, Nikola (1856-1943) A Croatian-born American engineer and inventor who developed the alternating current induction motor, an essential part of alternating current distribution systems. Tesla began his research in Hungary, and then emigrated to the United States in 1884. In America, Nikola Tesla and Thomas Edison came into regular contact with one another, not always with happy consequences, and an enmity grew between the two men. When it was proposed in 1912 that the Nobel prize be awarded jointly to Edison and Tesla, Tesla eschewed any association with Edison, and the prize went to a Swedish scientist instead. Tesla’s inventive mind turned power generated devices into interesting applications such as aircraft power systems and robotic submarines. He earned more than 700 patents in his lifetime, even though many of his ideas and inventions were not patented. He was somewhat temperamental and eccentric. One of his most practical contributions was the adaptation

of alternating current into everyday applications. His colleague, George Westinghouse, further implemented many of Tesla’s ideas. The tesla unit of magnetic flux is named after him. TESP See Telecommunications Electric Service Priority. test board A switching panel used for making temporary connections in conjunction with the panel or equipment being tested. By diverting some of the signals through the test panel, problems can sometimes be more easily isolated or identified. A test clip can also be used for the purpose of making quick temporary connections. See breadboard, shunt. test jack A connecting hole in a circuit or panel for inserting a plug and cable for making temporary connections for testing and maintenance. Test jacks and plugs come in many shapes and sizes depending upon what type of circuit is tested. A telephone test set is a portable telephone handset that has clips for temporary attachments to a conducting line or test plugs for temporary attachments to a test jack in a test jack frame. test jack frame TJF. In private branch exchange (PBX) telephone systems, a frame for inserting test cables for maintenance and testing, usually mounted in or near the main PBX cabinet and terminating the cabinet connections. test pattern Any pattern generated for a particular transmission medium that indicates the integrity of the various characteristics of its signal, which may include resolution, signal strength, stability, linearity, contrast, brightness, colors, sound range and quality, etc. 2. In video editing, a series of bands of specific colors. 3. In television broadcasting and television set calibration and diagnosis, a pattern (known to some as the Indian head pattern) which includes particular lines and line widths, ellipses, tonal gradations, and numerical values that allow the diagnostician to determine problems and make adjustments. This test pattern was frequently used in the 1950s and 1960s by local stations as a visual signal to viewers to indicate that there was no programming currently in progress, although this use has greatly declined due to the multitude of programming now available. tetrode A four-element vacuum tube. The three-element tube, called a triode, was developed by Lee de Forest. This no doubt inspired experimenters to try other configurations. The four-element tube followed, consisting of a filament, plate, and two grids rather than one. The second grid, the tetrode or screen grid, was positioned between the first grid and the plate (anode). Texas Educational Network TENET. A Texas education communications infrastructure dedicated to fostering educational innovation and excellence among educators and students. TENET developed through the collaboration of the Department of Information Resources, the Texas Education Agency, and the University of Texas. TENET provides various resources, including publications, discussion forums, and professional development seminars and

facilities. http://www.tenet.edu/tenet-info/main.html TFT See thin film transistor. TFTP See Trivial File Transfer Protocol. TFTP Multicast Option A protocol option for the Trivial File Transfer Protocol (TFTP) to enable multiple clients to concurrently receive the same file through multicast packets to increase network efficiency. TFTP Multicast Option was submitted as an Experimental RFC by A. Emberson in February 1997. See Trivial File Transfer Protocol, RFC 2090. TH transmission header. In packet networking, a header that includes control information, and may be followed by a basic information unit (BIU) or segment. Used for network routing and flow. theremin An electronic musical instrument incorporating radio frequency oscillators in which two similar frequencies were combined to provide a lower, human-audible frequency. This was done by combining a reference frequency with a variable frequency. The theremin was played by interposing a hand to vary the capacitance between two projecting electrodes, thus controlling the pitch and volume. It was first constructed in 1920 and became popular in the late 1920s. The process of mixing signals of slightly different frequencies is called heterodyning and was incorporated into many radios over the next couple of decades. A transistor version of the theremin still exists, and Mystery Science Theater 3000 fans are familiar with its eerie sounds. It was named after its inventor Leon Theremin, who originally called his invention an “œtherphone.” See heterodyning, Theremin, Leon. Theremin, Leon (1896-1993) A Russian engineer and inventor who devised electronic musical instruments, most notably the “œtherphone” (theremin) while a student at the University of Petrograd. He traveled to America in 1927 to play a concert, and 2 years later licensed the Radio Corporation of America (RCA) to manufacture a “thereminvox.” While in the U.S., Theremin also experimented with multimedia concerts, combining light shows and dance with the theremin music, later returning to do research at the University of Moscow. See theremin. thermal noise Random noise arising from heat generated by the motion of charged particles. Thermal noise in electrical circuits is undesirable if it interferes with transmission. thermal circuit breaker A breaker mechanism that trips when heat generated by excessive current expands the conductor. See circuit breaker. thermal wax printing A printing process by which various colors of wax are heated, sprayed, and adhered on the printing medium where they subsequently cool to form the desired image. The colored wax is usually supplied in the form of a long continuous film roll with blocks of sequential colors (cyan, magenta, and yellow) or four colors (CMY and black). The block of each color covers the width and length of the printing area, usually about the size of the printed paper or slightly smaller. Paper is then passed through the printer in three or four passes,

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depending upon the number of colors, in close contact with the waxed surface, and tiny heated print filaments hammer a dot of color onto the paper. As the printout advances, the color wax film is advanced until all blocks of color have passed across the surface of the paper. The three- or four-color process combines to produce the effect of many intermediate colors. This is not as economical a means of printing as inkjet, since inkjet is an on-demand printing technology which ejects only as much ink as is needed, while thermal wax sheets feed through the same amount of film whether one dot is on the page or a million. Thermal wax printing has become a medium pricerange solution for desktop color printers. While the process is not as photographic as dye sublimation printing, it’s pretty good and costs about 70% less per printout. One of the advantages of thermal wax printers is that they can print on many different types of paper, even on very fine sheets of aluminum. Many other color print processes rely on specialized papers, sometimes very specialized high-gloss paper. See dye sublimation printing, inkjet printing. thermion An electrically charged particle (a positive or negative ion) emitted from a heat source. See thermoelectron. thermionic emission The emission of electrically charged particles under the influence of heat. Thermionic emissions are characteristic of hot cathoderay tubes. Cathodes without thermionic emissions are called cold cathodes. thermionic valve See vacuum tube. thermistor An electrical resistor comprising a semiconductor with a high, nonlinear temperature coefficient. The resistance of the semiconductor varies sufficiently in relation to the temperature to make it useful in a number of applications. See thermostat. thermocouple, thermal junction A device which measures temperature at the junction of a pair of joined wires employing dissimilar materials, with the difference in potential proportional to the temperature, determined by an instrument connected to the other ends of the wires. See potentiometer. thermocouple wire A wire used with a thermocouple which is made of iron or particular alloys calibrated to the appropriate specifications. thermodynamics The art and science of heat-related phenomena, their properties and relationships. thermoelectron An electron (negative thermion) emitted from a heat source. See thermion. thermography A printing process in which nondrying inks are treated to simulate a raised, engraved surface. After passing through the press, the ink is dusted with a compound which, after the excess is removed, is exposed to heat, causing it to fuse with the ink to form a raised surface. thermoplastic A material with industrial significance because it can be heated and reshaped and rehardened by cooling. It has various uses including insulating and information recording. Contrast with thermoset. thermoset A resin or plastic material which can be

shaped and cured, but once this has been done, cannot be reshaped and cured again, as with thermoplastic. Contrast with thermoplastic. thermostat 1. A sensing and regulating device triggered by temperature which is useful in turning machines on or off, for controlling fire safety devices such as alarms and sprinklers, and for regulating heating and cooling systems. 2. A device which regulates temperature, by measuring it and controlling heating equipment (or heating and cooling equipment) in order to maintain the temperature at the setting selected on the thermostat. This is usually accomplished by triggering the heating circuit when the temperature falls a certain amount below or above the desired setting. Thermostats that can be programmed for specific temperatures at scheduled times during the day are increasingly common. Temperature regulation (cooling) in large supercomputing implementations is important. See thermistor. THF See tremendously high frequency. thin In typography, a unit of measure related to type size indicating a distance equal to one-third or onequarter of an em space. Thus, a thin in a 12-point font is 4 or 3 points wide. See em, en, point size. thin film transistor TFT. A technology used in display devices which creates a correspondence between a transistor and pixel on the screen so that pixels can be independently controlled. Used in color (RGB) active matrix LCD panels. This technology has been applied to portable display projectors and similar devices. Thompson, Joseph John (1856-1940) An English experimenter who investigated electricity and X-rays. He was awarded a Nobel prize in physics in 1906 for gaseous conductivity of electricity. Thompson, Ken (1943- ) Principal developer, along with Dennis M. Ritchie, of the Unix operating system in 1969. It is quite a distinction considering its widespread use and utility. Unix has since evolved through extensive support by the programming community and exists in a variety of forms, although all bear similar features. Thompson also authored B, which was a predecessor to C. See Unix, UNIX. Thompson, William See Lord Kelvin. Thomson, Elihu Inventor of one of the first alternating current (AC) generators in 1878. At the time, the predominant form of power was direct current (DC). This was a significant achievement because it permitted the transmission of much higher voltages, necessary to cross some of the distances desired. Improvements to the concept were soon developed by William Stanley. Thomson also experimented, in 1892, with electric arcs. He collaborated with Sebastian de Ferranti and William Stanley in the development of the transformer. thread 1. In piping, a helical indentation used to match and secure separate sections. 2. Continuing element, theme, or train of thought. 3. In programming, a flexible process organization mechanism by which individual processes can use common resources, but continue to operate unimpeded by other threads, if needed, in order to improve program

efficiency or to increase simultaneous access to various system or applications resources. Common in object-oriented systems. thread, discussion In online newsgroups, a topic of conversation characterized by the same (or similar) subject line, and theme and direction of discussion. Threads are a very convenient way to follow one line of thought through the myriad opinions discussed in the general context of a newsgroup. Good newsreading software will organize threads into groups and subgroups much the same way computer directories (folders) are organized on the computer operating system. Thus, the user can selectively open and read, or close and ignore, a thread. three finger salute slang A descriptive phrase for rebooting the operating system (without powering down the system) with three designated keys held down simultaneously for MS-DOS/Intel-based IBMlicensed systems (Ctrl-Alt-Delete) and Amigas. throughput Production; output; nonredundant information or items of relevance moving through a system. Throughput is used in industrial and computing industries to describe the efficiency of a system or end-result of a communication (how much information got through). The measurement of throughput is quite specific to the system and information or objects being transferred, so there are few generalized standards for time intervals or total data against which to compare the throughput (end result). Nevertheless, relative measures of throughput, as compared to another manufacturer, another type of machine, or when processed in a different manner, can be very useful in tuning a production line system. Relative measures of data throughput in different parts of a network, or over different data protocols or operating systems, similarly can be used to improve the configuration and efficiency of a computer network. TI-99/4 A Texas Instruments home computer introduced early in 1980. It featured 16 Kbytes RAM, sound capabilities, 16-color graphics on a 13-inch color monitor, extended TI BASIC, and cartridgelike solid state program modules for a list price of $1150 U.S. TIA See Telecommunications Industry Association. TIB See tone in band. TIC See Token-Ring interface coupler. ticket In telecommunications, a record of a transaction or paid toll, fare, or fee. The ticket indicates either that the transaction has been confirmed and it’s OK to bill the client, or that the transaction and billing have both taken place (as in many credit card transactions). Tickets traditionally were on paper, but electronic tickets are becoming prevalent, with online transactions sometimes going directly through to the credit card company from the vendor without any slips or other paper confirmations. tickler In computer applications, a program designed to hibernate until a certain time or until certain events take place, and then become active to remind the user of something timely or important, such as appointments, anniversaries, events, etc. These

applications have variously been called ticklers, reminders, and naggers. tickler, electronic In electronics, a feedback or regeneration device consisting of two small coils connected in an electron tube, one to the anode (in series), the other to the grid-circuit. tie n. Fastener, electrical strap, bundler. A strip, usually of plastic or Velcro™, to hold wires away from one another, bundle them together, or fix them in place, sometimes to a post or other secure structure. tie line 1. In power systems, transmission lines that connect neighboring systems. 2. In telecommunications, a line for directly tying two telephone or telegraph connections together without going through a public switching center, often called a “dedicated” line. For example, the President might have a tie line connected directly to top advisors that doesn’t go through any outside switches or connections, to ensure security, reliability, and speed for the connection. In the days before telephone switching centers and central offices connected local telephone subscribers, tie lines were common. For example, in the 1800s, a dozen telephone or telegraph tie lines might be wired out of a single office to connect it with other local businesses. The streets were often cluttered with hundreds of lines running between windows and buildings and the utility poles holding the lines were complexly wired and difficult to maintain. Tie lines are still used for a variety of security and business-related purposes. They are especially useful in office complexes composed of several buildings that have a large volume of calls between the buildings. A tie line may be set up to connect directly simply by lifting the handset or pushing a button, as in a hot line. A tie trunk connects to telephone switching systems such as two private branch exchange (PBX) systems and may require dialing access code prefixes reserved for that purpose on a particular system or the system may be locally automated to interpret an extension number to be translated into a tie line call. With the evolution of voice over digital data networks, the concept of tie lines has been adapted to computer networking. Access concentrators can be used to consolidate separate voice and data lines used for communications within a company into a single network and voice over network communications can then replace traditional telephone tie lines. Thus, existing Frame Relay links used for data, for example, could also be used for voice communications, removing the need for dedicated phone lines. tie trunk A telephone (or telegraph) line directly connecting private branch exchanges (PBXs). See tie line. tie line control system In power distribution, a system for administering the amount of electrical energy purchased by a subscriber (usually an industrial complex) from a utility company. tie wrap A plastic, fabric, jute or other type of tie material used for holding together a bundle of cables for ease of placement or movement as a unit. Plastic

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tie wraps sometimes have a hook mechanism that catches and holds the tie when it is cinched tight. Velcro brand tie wraps are easy to unwrap and readjust, if needed. TIES 1. Telecom/Information Equipment and Services. A government-to-government program which provides U.S. and Russian support for the expansion of international commerce in high technology. This is a subgroup under the U.S.-Russia Business Development Committee (BDC). 2. See Telecom Information Exchange Services. TIFF Tag Image File Format. A very widely used platform- and application-independent, lossless, color, raster image file format that encodes the data as strips or bands. The TIFF format is used in faxes, image processing programs, scanned files, and many graphics creation programs. It is well supported by service bureaus and the printing and graphics design industries. Files are often identified by the .TIF or .tiff file extensions. Creation of the format took into consideration the needs of the desktop-publishing industry and other related graphics applications, with the goal of making image information broadly interchangeable. TIFF was created to be extensible so that it may accommodate future needs. TIFF has gone through a number of major revisions but, in general, fields are identified with unique tags so that various applications can elect to include or exclude particular fields depending upon their needs and capabilities. The core fields comprise Baseline TIFF. A TIFF file consists of three main parts: an image file header, a directory of fields, and the file data. Descriptions and definitions of baseline and extended fields are documented in the TIFF Technical Notes (TTN). An adaptation called TIFF-FX has been defined for facsimile applications. See facsimile, scanner, TIFF-FX, TWAIN. TIFF-FX A subset of TIFF adapted to generating documents with minimal, lossless grayscale and color attributes for use as facsimile messages. The format uses some of the Baseline TIFF fields in addition to extensions pertinent to facsimile transmissions. Since the format can be used over both traditional and host-based transmissions media, TIFF-FX is suitable as a downwardly compatible, standardized facsimile format for data network communications. Profile S (TIFF-S) is a subset of TIFF, related to TIFF-FX, that defines a minimal black-and-white format to enable fast easy transmission of simple facsimile documents. Profile F (TIFF-F) is a slightly extended version of Profile S that is still restricted to black-and-white transmissions. TIFF-F was originally introduced by Joe Campbell and a group of fax experts; then, in 1998, with increased interest in Internet faxing connectivity, it was formally described by the IETF Internet Fax Working Group. In essence, the image data to be faxed are compressed and inserted into a TIFF-FX file with the informational fields encoded with data specific to the image. The byte order is from least to most significant (an

important detail, since the full TIFF specification can be set to either big- or little-endian and conversion may be necessary before transmitting as a TIFF-FX variant). While the full TIFF specification is somewhat flexible in terms of the ordering and structure of fields, TIFF-FX recommends that multiple image file directories (IFDs) be organized as a linked list. The MIME Content Type for these files is image/tiff. The Application parameter is TIFF-REG (optional). See IFax device, image file directory, TIFF, RFC 2301, RFC 2306. TIIAP See Telecommunications and Information Infrastructure Assistance. tiling 1. In printing, a technique for printing a large image on pieces of paper that are small, relative to the size of the image. Commonly used for billboards, banners, and wall-sized murals. Most computer printers have options for tiling, in order to print large images on letter sized paper. 2. In digital image display, a visual artifact common to heavily compressed images which causes a blocky, mosaic-like appearance to otherwise smooth lines and transitions. See DCT, JPEG. TIMA See Interactive Media Alliance, The. TIME Time Protocol. A network date/time protocol submitted as an RFC in May 1983 by Postel and Harrenstien. TIME provides a site-independent, machine-readable date and time. The Time service provides the time in seconds since midnight January 1, 1900. This is useful for systems that do not have a built-in date/time clock and for systems that need to be coordinated to preserve or aid data integrity or process administration. TIME can be accessed through port 37 over Transmission Control Protocol (TCP) or over the User Datagram Protocol (UDP). See RFC 868. time code A system of encoding timing information on a recording medium, usually along with the information that is being stored. This technique is commonly used with audio/visual recordings that will later be edited, dubbed, or otherwise manipulated or played within strict time constraints. Time code is typically stored as hours, minutes, seconds, and frames. Time code was developed in the late 1960s when analog recording tapes became prevalent, in many cases replacing film. The system was developed because video tape lacked the sprockets which previously had been used on film to synchronize sound and images. In the 1990s, another transition was made from analog video tapes to digital recording technologies, and the time code techniques used for analog video and audio encountered certain problems when applied to digital recording technologies. See chase trigger, MIDI time code, reference clock, SMPTE time code. Time Division Multiple Access TDMA. A digital technology designed to overcome some limitations of analog cellular mobile communications. Time slot assignments allow several calls to occupy one bandwidth, thus increasing capacity for various wireless technologies. E-TDMA (Extended TDMA) provides

even more time slots. TDMA is widely supported by AT&T Wireless Services. It is similar to Code Division Multiple Access (CDMA). See Demand Assigned Multiple Access. There are a number of TDMA implementations, with three primary ones: European TDMA (GSM), Japanese TDMA (PHS/PDC), and North American TDMA (IS-136). See AMPS, DAMPS, cellular phone, time division multiplexing. time division multiplexing TDM. A technique for combining a number of signals into a single signal by allocating a time slot in the combined signal with a multiplexer. At the receiving end, a demultiplexer is used to separate the interleaved signal back into its original signals. Some of the early developments of this technique were accomplished by J.M.E. Baudot in the 1870s. In current usage, TDM allows a variety of types of communications, audio and video, to be transmitted at the same time in one interleaved signal. time signals From around the mid-1800s before time zones were established, to the present day, people have sought to devise ways to determine the time and synchronize their activities. The first time signals were drums or bells that were regularly sounded in local communities based upon the sun’s position. Later, in the 1860s, the U.S. Naval Observatory used the telegraph to transmit time signals, and soon Western Union was sending standard time signals, a tradition they continued for a century. Telegraph time signals were similar to current Coordinated Universal Time signals, in that audible clicks were used coming up to the hour, just as tones now signal the upcoming minute. See Coordinated Universal Time, Greenwich Mean Time. Time T An ITU-T designation for 2359 hours Coordinated Universal Time (UTC) on 31 December 1996. time-space processing Also called temporo-spatio processing, this is type of processing is used in applications and devices such as infrared motion detectors or radar systems which are using time and space as interrelated factors in their decision-making in terms of processing data or signaling an alarm condition. Time-space processing is also used in adaptive beam-forming antenna mechanisms. timing Configuration of a system so successive repetitions are controlled for the desired interval (which may be desired to be variable), or so certain events begin and/or end at designated times or according to certain events. Timing is important in magnetic storage mechanisms, motors, signal amplitude sequences in electronics, and broadcast equipment configurations. Timing is also important on networks, where, for example, video and audio signals may be sent separately or on separate lines, but have to be coordinated at the end to provide services like videoconferencing. Constant oscillators are often used in conjunction with very precise timing devices. See atomic clock, quartz, SMPTE time code. timing signal 1. A signal generated according to an accepted standard of time, usually for the purpose of providing a precise or objective baseline against

which to measure events. 2. A signal generated by measuring some repetitive event which is then compared to some standard or clock. 3. A signal simultaneously recorded with data to provide a measure or standard against which the data can be analyzed. 4. A regularly emitted signal against which other time-related events can be synchronized. TINA Telecommunications Information Networking Architecture. A networking telecommunications software architecture intended to be developed into a global standard. See Telecommunications Information Network Architecture Consortium. TINA-C See Telecommunications Information Network Architecture Consortium. tinned wire Wire that has been treated with tin to provide insulation and/or to facilitate soldering. Common on copper wire. tinsel A fine, very long thread or strip of metal sometimes wound around electrical conductors between the insulator and the main core or wire. Because of its properties, tinsel is used in cables that need to be tightly wound or very flexible (such as phone handset cords). tint Lighter or darker values of a particular color; hue. Tints are created by successive additions of white or black pigments, or by successively increasing or decreasing values of red, green, and blue (RGB) at the same time. Greater amounts of each color of RGB will produce lighter tints and lesser amounts will produce darker tints. tip 1. The line or connection attached to the positive side of a circuit or battery. 2. In two-wire telephone wiring, the tip is traditionally the green wire attached to the positive side of the circuit at the central switching office. The name originates from the configuration of a manual phone jack in an old telephone switchboard in which the large plug was divided into two sections, with an internal wire electrically connected to the tip of the plug, and another wire to the ring around the plug partway up the jack nearer the insulated cord. See ring, tip and ring. tip and ring Historically, the tip and ring designations derive from the configuration of a phone jack from a manual switchboard, called a cordboard. The tip was the positive circuit connected to the tip of the jack, and the ring was negative, located slightly away from the tip encircling the jack, sometimes called “sleeve.” Later the tip and ring became standardized to correspond with the green and red colorcoded wires traditionally used to install phone line services. Often telephone wire is composed of four wires with red, green, black, and yellow sleeves. Since dual lines have become more common in small businesses and in some homes, the black and yellow lines are used for tip and ring, respectively, for the second line. While these codes are standardized in North America, there are variations in other countries and in larger installations with multiple phone lines. tip jack, pup jack One of the simplest onnectors, a tip jack has a single, usually round, contact point plug that fits into a matching single-hole plug.

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TIPHON See Telecommunications and IP Harmonization Over Networks. TIRKS Trunk Inventory Record-Keeping System. A commercial product from Telcordia that aids in planning, inventorying, and assigning the telephony circuit order control and circuit provisioning of interoffice equipment and facility inventory. FEPS is a component of TIRKS that provides a range of automated software tools for planning and provisioning interoffice facilities and transmission equipment.

satellites developed by GSFC, built by RCA, and managed by the Environmental Science Services Administration (ESSA). It was followed by the TIROS Operational System (TOS), then by Improved TIROS (ITOS), and subsequently the NOAA satellites. The TIROS spacecraft included low-resolution television and infrared cameras. The TIROS craft 1 to 10 were launched between 1960 and 1965 into low Earth orbits. TIROS-N was launched in 1978. In general, they looked like cylindrical “mirror balls,” studded as they were with solar cells, and were about the size of an oil barrel sliced in half. Spiny leglike antenna protruding from the flat end of the cylinder gave them an insect-like look. TIROS systems provided the first meteorological data for weather forecasts that were received from space. Continuous coverage of the Earth’s surface began in 1962 and proved the feasibility of space data for meteorological research and forecasting.

An artist’s rendition of a TIROS-N/NOAA A-G Series remote-sensing satellite from the series that built upon the original TIROS satellites from the 1960s. TIROS-N satellites included updated design concepts, power cells, telemetry, and sensing devices, compared with the earlier series. [NASA image.]

Top: An artist’s conception of the TIROS 2 meteorological satellite illustrating the wide-angle and narrow-angle fields of view of the cameras intended to image Earth’s surface. This drawing was created in March 1960, prior to the launch. Bottom: A diagram illustrating the antennas, sensors, and solar cells in the TIROS 7 meteorological satellite, as envisioned in April 1961. [NOAA In Space Collection.]

TIROS Television Infrared Observation Satellite. A historic series of global polar-orbiting meteorological

TIROS N/NOAA Program A remote-sensing satellite program based on the TIROS satellite series that was initiated to improve upon the operational capabilities of the original TIROS numbered series from the 1960s and its successors in the 1970s. In contrast to the earlier barrel-shaped TIROS systems, the TIROS-N satellites were longer and more rectangular, and about three times larger. The systems were three-axes stabilized and Earth-oriented. Improvements in sensing technologies and solar power were incorporated into the later TIROS/N series which includes a number of successful and failed satellites beginning in 1978 and continuing into the late 1990s and present. ITROS-N satellites carried the Advanced Very High Resolution Radiometer (AVHRR) for day and night sea surface and cloudtop sensing. An atmospheric sounding system was also included, as well as a solar proton monitor to detect energetic particles from the Sun that might signal an upcoming solar storm.

Titanic, RMS The famous, ill-fated “unsinkable” ship that sank in 1912, with hundreds of lives lost, while crossing through ice fields north of Canada. The radio operator of the Titanic sent distress calls, but two of the closest ships didn’t receive the communications, as 24-hour watch programs and radio regulations had not yet been established (this changed after the sinking of the Titanic). Fortunately, however, some of the sea-goers were saved by the Carpathia, who came to their rescue after receiving the radio distress call. The sinking of the Republic, an earlier ocean-going ship, had a strong influence on legislation requiring wireless communications systems to be installed on ocean-going vessels. Due to the wireless distress calls, all but two of the hands on the Republic were saved. The sinking of the Titanic resulted in further legislation associated with keeping those communication lines open and monitored 24 hours a day. See the JASON project, MARECS, MARISAT. title Commercial product, usually shrinkwrapped. A term often applied to off-the-shelf entertainment and educational software products, especially multimedia CD-ROM programs. TJF See test jack frame. TL See tie line. TLD See top level domain. TLF See trunk link frame. TLP See transmission level point. TLS Protocol See Transport Layer Security Protocol. TLV type, length, value. An encoding approach used in Basic Encoding Rules for the information content of elements. TM 1. terminal multiplexer. 2. traffic management. A term associated with network transmission cell traffic flow, monitoring, and control. See cell rate. TMA Telecommunication Managers Association. See Communications Management Association. TMC traffic management center. TMGB See telecommunications main grounding busbar. TMN See Telecommunications Management Network. TMS 1000 A one-chip 4-bit microcomputer introduced by Texas Instruments in 1972. Arguably the second microcomputer ever released, following the release of the Intel MCS-4 chip set, it never gained popularity. TMSI See Temporary Mobile Station Identifier. TOGAF See The Open Group Architectural Framework. toggle Two-state process or switch. Flip-flop. An electrical current that alternates in intensity at two distinct levels, or which has two states: on or off. A traditional light switch is a type of toggle, unlike a dimmer switch which has many possible settings. In software applications, a button or icon that has two states or positions. In computer programming, a flag that is either set or not set, on or off. Toggles are very commonly used to keep track of settings.

token On a Token-Ring network, a status/priority information block used in coordination of traffic on the network. A token consists of a 24-bit frame that operates at the Media Access Control (MAC) level. It is continually passed around the ring in one direction and consists of a start delimiter (SD), an access control (AC) field, and an end delimiter (ED). Most of the information for controlling events is contained in the AC. It is further subdivided into a 3-bit priority field, a token bit (zero indicates it is a token), a monitor bit, and a 3-bit reservation field that lets the station get in the priority queue for future transmission of frames. A token is reissued after use by a station of the suitable priority, and continues on its way. See token-passing, Token-Ring frame, Token-Ring network. Token-Ring interface coupler TIC. A Token-Ring local area network (LAN) port that is typically installed on a computer peripheral network interface card (NIC). The TIC facilitates the connection of the computer to the local network. token latency In a token-passing scheme, the time it takes for the token to make it all the way around a token-passing local area network. See token-passing, Token-Ring. token-passing A process on a Token-Ring network by which status/priority tokens are used as a mechanism to coordinate traffic around the unidirectional ring. A token is a 24-bit frame that operates at the media access control (MAC) level. It consists of a start delimiter (SD), an access control (AC) field, and an end delimiter (ED). The token-passing continues around the ring where each station checks the priority before adding frames to the traffic on the ring. Once a token has been used, assuming the proper priority, it is sent out again by the transmitting station to continue its journey around the ring through each station, carrying out the same sequence of events, according to priority levels. Token-Ring frame A Token-Ring frame in the IEEE 802.5 specification consists of the components specified in the Token-Ring Basic Frame Components chart. Token-Ring Interface Processor TRIP. A Cisco Systems high-speed interface processor with two or four Token-Ring ports, which can be independently set to speeds of 4 or 16 Mbps. Token-Ring network TR network. A local area network developed by IBM in the mid-1980s, employing a star or ring topology, that is, with nodes connected directly to one central hub, or in a continuous loop not requiring termination. The token-passing is a scheme for data transmission between the stations which prevents collisions from different workstations sending messages at the same time. A workstation cannot transmit until it receives permission, that is, a token of the proper priority. The token is passed from station to station around the ring in one direction. At each station, the priority is checked before a frame is transmitted on the ring. Token-Ring uses a source routing system that moves information among stations based upon information in data packet headers, thus utilizing inexpensive

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bridges, a system different from Ethernet LANs. Speeds are up to about 16 Mbps, a limitation that has been addressed in High Speed Token-Ring, and throughput is about 60 or 70%, somewhat higher than Ethernet. Frames hold about 4000 bytes. Token-Ring LANs are sometimes combined with Ethernet LANs. They typically run over copper twisted-pair cables, although some are now implemented with fiber. Since IBM’s introduction, Token-Ring has been developed into a Media Access Control (MAC) level standard protocol by the IEEE (802.5). A Fiber Distributed Data Interface network employs various Token-Ring token-passing concepts using dual rings to provide redundancy and fault tolerance. See Ethernet, Fiber Distributed Data Interface, High Speed Token-Ring, ring topology, star topology, topology. TokenTalk An Apple Computer Macintosh-based implementation of a Token-Ring local area network. See AppleTalk, Token-Ring network. toll call Any call to a location outside the local service area, so called because it is billed at a rate above and beyond the local subscriber service. A long distance call. toll denial Denial of service outside the local service area. Toll denial may be part of a private exchange in order to limit calls to local calls, except as authorized. Toll denial may also be set up on an individual

subscriber line (e.g., a subscriber who is behind in payments on long distance charges), or a line in a college dorm, or other location where potential toll abuse or fraud may occur. It may still be possible to make toll calls by going through an operator or entering authorization codes. See toll diversion, toll restriction. toll saver A feature of answering machines and some computer software programs that lets you call into an answering machine from a long distance location and know whether there are any messages before the line is connected. The system is based upon the number of rings, usually four or two. With toll saver enabled, if there are no messages, the answering system will ring four times before answering. If there are messages, it will answer on two rings. That way, if the caller hears three rings, there are no messages, and he or she can hang up before the machine answers on the fourth ring and save the long distance charge. toll terminal A phone system set up only for long distance calls (toll calls). Toll terminals may be set up to expedite long distance calls, or to compartmentalize billing or reporting on long distance calls. A toll terminal may be in a secure location, accessible only to authorized toll callers. tone above band TAB. A form of linear broadcast signaling used in conjunction with single sideband

Token-Ring Basic Frame Components Abbrev. Item

Notes

SD

Starting Delimiter

Indicates the beginning of a frame.

AC

Access Control

Contains the Priority, Token, Monitor, and Reservation bits. In a frame, a workstation can only change the Reservation bits in the access control field. Only the active monitor can change the “M” bit, and only the workstation or device changes the Token bit.

FC

Frame Control

Indicates the type of frame: data frame or maintenance frame. A maintenance frame is used by the protocol to manage the ring.

DA

Destination Address

Physical or NIC address of the receiving workstation or device.

SA

Source Address

Physical or NIC address of the sending workstation or device.

Information

Layer control, routing control, and data.

FCS

Frame Check Sum

Error checking at the destination.

ED

Ending Delimiter

FS

Frame Status

Indicates the end of a frame. If one of multiple frames or the last frame in a transmission, it’s an I bit; if an error occurred, it’s an E bit. Indicates if a frame has been recognized and copied by the destination station.

suppressed modulation. In TAB, corrections are applied to the received signal, as needed, to produce recognized pilot tones above the frequency of an information signal (as opposed to its center), to correct the accompanying information signal. Transparent tone above band (TTAB) is the same essential idea except that the tone is explicitly chosen to be outside the hearing range audible to humans. See tone in band. tone dialing A system of audio tones called dual tone multifrequency (DTMF) used to generate distinct signals with which phone numbers and symbols can be transmitted. Frequencies are selected in such a way that dual tones are not harmonically related. Each tone is actually a combination of two tones, high and low, which are decoded when sent down the line to the switching office. The high tone is usually slightly louder than, or at least as loud as, the low tone. The tones range in frequency from about 697 to 1633 Hz. Two advantages of tone over pulse dialing are speed and flexibility. As direct dial long distance services became available, numbers became longer, and it takes a long time to dial a number on a pulse phone, partly because of the mechanical act of rotating the dial and partly because the dial has to return to the base position before dialing the next number. Touchtone systems also provide more options. With a combination of digital processing and touchtone signals, automated menu systems can be accessed through the phone. These are now widely used by banks, mail order houses, and others. See pulse dialing, DTMF, touchtone dialing. tone generator Any device or software application which generates tones. These may be at a particular frequency or may vary. Tones can be generated in the audible frequency range for humans, or higher ranges for electronic detection. See buzzer. tone in band TIB. A form of linear broadcasting modulation in which corrections are applied to the received signal, as needed, to produce recognized pilot tones at the center of a baseband information signal, thus making it possible to correct the accompanying information signal. Forward signal regeneration may be used to enhance TIB. Linear modulation techniques provide narrower channels than frequency modulation techniques, thus making it possible to increase the number of channels in a specified amount of space. By the mid-1980s, transparent tone in band (TTIB), which uses a tone frequency inaudible to the user, was being developed for use in mobile radio networks, for example, to help reduce fading loss. TTIB has become a standard in North America and Europe. See linear modulation, tone above band. tone probe A diagnostic device which is used to detect and amplify audio tones, usually in the 500 to 5000 Hz frequency range, although it depends on the application. Cable technicians use these to trace cable links, for example. The tip of the probe is unshielded in order to selectively position it to detect a signal. Filtering may be incorporated to eliminate noise. Some probes have earphone jacks so they can be used with stereo headphones. A tone probe may be used

in conjunction with a tone sender. sensitive probe tip on/off switch

LED indicator

Tone probes, such as this one from Fluke Engineering, are used for testing and diagnosing cable installations through use of an audible tone. The tip is a sensitive probe that activates a light-emitting diode. [Classic Concepts illustration; used with permission.]

tone receiver unit TRU. The electronics in a telephone receiver which detect and interpret touchtone codes. toolbar In computer graphical user interfaces, a type of selection menu that consists of buttons, usually iconized, grouped together. Commonly, toolbars consist of about 4 to 20 buttons grouped in one or two rows or columns. Toolbar buttons are often singleclicked to activate them, or double-clicked to expose more options. They are especially common in painting and drawing programs, or along the tops and bottoms of word processing or desktop publishing software. Toolbars may or may not be movable. TOP See Technical Office Protocol. top-down An organizing or processing hierarchy that distributes itself downward, usually in a branching pattern. Top-down often implies higher priority or more generalized functions or items at the top of the hierarchy. Thus, a top-down outline lists more important concepts first, a top-down personnel chart usually shows executive managers at the top, a topdown phone system starts with priority-listed agents, etc. Top Level Aggregate TLA. An IPv6 prefix and a coveted commodity to the Internet community, the proposed assignment of Top Level Aggregates to privileged companies caused controversy. To quell the objections, TLAs were significantly increased and TLA requirements were removed from the IPv6 specification. Many Internet developers are concerned with preventing the development of a VIP system on the Net. See IPv6, Next Level Aggregate. top level domain TLD. A hierarchical subset of the domain name system (DNS) which has been further subdivided into generic top level domains (gTLDs) and country code top level domains (ccTLDs). The

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distinction is administrative rather than functional; TLDs all theoretically have the same access and connectivity to the Internet. Within individual designations, some domain name extensions are open and some are restricted. For example, the popular .com designation used primarily for business entities is unrestricted, whereas the .gov designation is restricted for assignment to U.S. federal government agencies. Country code TLDs are open or restricted to varying degrees depending on the country maintaining the designation. Country code TLDs include .ca for Canada, .uk for the United Kingdom, .au for Australia, etc. By 1999, it was estimated that almost 100,000 domain names were being registered per month, with demand steadily increasing. See the Appendix for a list of domain name extensions. topology, network topology A schematic representation and configuration of the geometric and electrical connections and relationships of a network and its various routing components. Depending upon the number of servers, terminals, routers, and switches, a variety of possible configurations are practical, including token rings, stars, and others. See backbone, mesh topology, node, star topology. Topology Database Update TDU. The refreshing of interconnections and routing information within a network system to reflect the current connections. The Topology Database may have upper limits as to the number of nodes that can be specified to describe the system. In many systems, there are commands for querying the Topology Database parameters and logs as well as commands for setting the basic operating parameters. For example, the frequency of updates may be logged to help a system administrator determine if configuration parameters are optimally set. topology management In networks, the configuration, tracking, and management of connecting devices, particularly switches. The software used to manage them will often show graphical images of the various devices and their interconnections in the system. TOPS See Traffic Operator Position System. Torricelli, Evangelista (1608-1647) An Italian physicist and mathematician who invented the torricellian tube, now known as a mercury barometer. Barometers later became important in weather forecasting and in altitude-measuring instruments, particularly for aeronautics and ionospheric experimentation. The technology was also important in the evolutionary development of the vacuum tube, the basis for electronics for many decades until transistors and semiconductors were developed. ToS See Type of Service. total internal reflection In a light-guiding cable, the total reflection resulting when light rays guided through a waveguide (e.g., fiber optic filament) impact another material and are reflected back into the original waveguide. Total User Cell TUC. In ATM networking, a recurring count of the transmitted Cell Loss Ratio (CLR), stored in the TUC field. The information is useful in

assessing throughput. The CLR may be calculated using the Total User Cell (TUC) and the Total Received Cell (TRC) counts. touchscreen A specialized computer monitor which is activated by contact with a finger or pointing instrument. The idea was that it was more natural for people to point than to use a mouse of keyboard. Unfortunately, holding an arm up for any length of time is uncomfortable, so touchscreens haven’t become popular for extended or repetitive work. However, they are suitable for occasional input, as in kiosks and directory systems, and for some types of childhood education. Townes, Charles H. The Nobel Prize-winning scientist who co-invented the laser along with Arthur Schawlow, in 1958, while working at Bell Laboratories. See Capasso, Frederico; laser. TP 1. test point 2. transaction processing. 3. transport protocol. 4. twisted pair. TPA See Telephone Pioneers of America. TPDU See Transport Protocol Data Unit. TPEX twisted pair Ethernet transceiver. TPI tracks per inch. A measure of the density of a recording medium such as a phonograph record or formatted hard drive. The tracks may be physical (as in grooves) or virtual (as in a logical segmentation on a drive that varies according to the file standard and/or operating system). TPOS See Training, Planning & Operational Support. TPWG See Technology Policy Working Group.

Evangelista Torricelli contributed important inventions leading to the development of vacuum tubes, barometers, and altimeters. [Italian Postal Service, 1958, G. Savini, V. Nicastro.]

TQM total quality management. A management philosophy and means of putting it into action to develop and maintain quality principles in commerce, service, and manufacturing. Quality assurance and ISO-900x certification are two kinds of tools in the TQM arsenal. See ISO 9000. TR transmit/receive. traceroute A Unix shell utility written by Van Jacobson at Lawrence Berkeley Labs which seeks out and displays the path of a transmission packet as it travels from host to host, detailing the hops in the path. Traceroute sends an IP datagram to the destination host, then it iterates through each router, decrementing TTL, discarding the datagram, and sending back ICMP messages until the destination host is reached. Traceroute is extremely useful as a network diagnostic and optimizing tool and often used in conjunction with ping. See ping. The Traceroute Example inset below shows a sample of traceroute output showing the IP numbers, hops, and packets. trackball A hardware peripheral device which receives tactile directional input and transmits it to a computing device. The information transmitted is similar to that of a mouse or stylus, and is often used in conjunction with graphical user interfaces (GUIs). Unlike a mouse or stylus, a trackball is generally fixed in place, with physically separate buttons. Trackballs are common in video arcade games and on laptop keyboards to increase portability. See joystick, mouse. TRACON Terminal Radar Approach Control. An airfield navigation radar system designed to aid in landing approaches and takeoffs. In commercial airports, the TRACON is typically housed in the air traffic control tower (ATCT). The Federal Aviation Administration (FAA) has almost 200 of these radar approach facilities in the U.S. A TRACON control room may accommodate a number of operators and typically has backup generators to ensure air traffic safety in the event of power outages. As cities grow, the need to support increased and more complex air

traffic grows as well. To meet this need, the Federal Aviation Agency (FAA) has been working on projects to consolidate individual TRACONs into what is termed Large TRACONs. tractor feeder A sprocketed paper alignment device used mostly on impact printers. It provides more precise control of positioning than most roller feeders by preventing slippage. The tractor feed resembles a pair of short regular series of inverted cleats which fit through corresponding holes in tractor feed paper. Tractor feed mechanisms are especially useful for multipage documents (invoices, checks, etc.) on dot matrix printers. trade secret Information, data, process, or procedure which would lose its commercial value if revealed to outsiders. Nondisclosure agreements (NDAs), policy statements, and inservice training are mechanisms which restrict external communication of trade secrets. If trade secrets are not specifically identified by an employer, it may be more difficult to stop or prosecute an offender who has willfully or inadvertently revealed them. See patent, copyright, nondisclosure agreement, trademark. trademark A legal designation for the right of an association to the use of a mark in trade. It can consist of a word, phrase, or symbol sufficiently unique to be distinguished from others in the same general industry. Provided it is not already owned by another entity, a trademark becomes valid as soon as a company uses it in trade according to certain stipulations, provided the company continues using it. You cannot come up with a trademark idea, not use it, and claim it later if someone else uses it. Trademarks may be registered federally for a fee, although this is not required. The motivation for trademark registration is to provide prima facie evidence in the event of a legal dispute. Unregistered trademarks must be identified with a ™ symbol, and registered trademarks must be identified with an ® symbol. Policing of trademark violations is not a responsibility of the federal government or of the agency that registers a

Traceroute Example $ traceroute abiogenesis.com traceroute to abiogenesis.com (207.173.142.184), 30 hops max, 38 byte packets 1 chapman.nas.com (198.182.207.6) 322 ms 252 ms 251 ms 2 orthanc.nas.com (198.182.207.1) 251 ms 247 ms 275 ms 3 milo-s4.wa.com (204.57.232.1) 277 ms 257 ms 296 ms 4 dilbert-fe4-0.wa.com (192.135.191.254) 530 ms 303 ms 273 ms 5 dogbert-f4-0.nwnexus.net (206.63.0.254) 263 ms 282 ms 286 ms 6 borderx2-hssi2-0.Seattle.mci.net (204.70.203.117) 306 ms 277 ms 373 ms 7 core2-fddi-1.Seattle.mci.net (204.70.203.65) 288 ms 511 ms * 8 bordercore1.Denver.mci.net (166.48.92.1) 299 ms 323 ms 293 ms 9 electric-lightwave.Denver.mci.net (166.48.93.254) 294 ms 351 ms 313 ms 10 H3-0.1.scrlib01.eli.net (207.0.56.162) 329 ms 394 ms 591 ms 11 gw2-CALWEB-DOM.eli.net (208.131.46.46) 730 ms gw1-CALWEB-DOM.eli.net (208.131.46.30) 507 ms gw2-CALWEB-DOM.eli.net (208.131.46.46) 357 ms 12 abiogenesis.com (207.173.142.184) 362 ms 358 ms 350 ms

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trademark; it must be done by the company seeking to protect the trademark. Trade names are similar to trademarks and are registered at the state level. There can be more than one company using the same trade name, if the line of business is sufficiently different to prevent confusion. The Commerce Department’s large database of patent text and images, 800,000 trademarks and 300,000 pending registrations dating from the 1800s, has been gradually uploaded to the Web since 1998. See copyright, patent. http://www.supot.gov/ Traf-O-Data The first business partnership of Paul Allen and William R. Gates, founded around 1972, growing out of the business experiences of the less formally organized Lakeside Programming Group. Allen and Gates worked together on a variety of software projects including an automobile traffic flow system. At about the same time, they prototyped an early microcomputer based upon the recently released Intel 8008, with the participation of a hardware designer, Paul Gilbert. They made some tentative attempts to sell this early machine, but it didn’t work during an early demonstration. At about the time Gates graduated from high school, Allen encouraged him to join him to start a company to build and sell computers based upon the Intel 8080 chip set, but Gates wasn’t fired up about the idea of a hardware company, and his parents were encouraging him to continue his post-secondary education. The majority of Gates and Allen’s subsequent efforts were software-related, most significantly, a BASIC interpreter for the Altair, and a disk operating system for IBM, which resulted in the founding of Microsoft Corporation. The subsequent success of the company was due to sales of software, primarily operating systems and business applications, and Apple Computer became the small business success story in computer hardware. traffic A term often used on large communications systems to describe communications signals, data, cells, or packets which comprise the information and signaling associated with the transmissions. The term is sometimes also used to describe the overall flow and pattern of traffic in the context of the system it is on, as in traffic congestion, traffic flow, traffic monitoring, traffic engineering, traffic routing, etc. In telephony and various systems that are largely analog based, the term may be used to describe the flow of information in the context of calls, as in call attempts, call connects, call volume, etc. In digital systems, it is often used in a more specific sense to indicate numbers of packets or cells. See leaky bucket. traffic capacity A measure of the capability of a system to carry a certain maximum number of calls, cells, frames, or packets, depending on how capacity is measured or data carried on that particular system. The maximum capacity may not be a fixed number, as on systems where multiple channels may be aggregated to carry certain broad bandwidth types of information. On other systems, where one or two wires can carry one and only one communication, traffic capacity is more likely to be expressed as a

set amount. Traffic capacity is used in systems design and marketing to provide buyers a general guideline as to the capability of a system. For example, a rural phone switching system in a small community may only require a capacity of 20,000 call seconds (usually expressed in increments of hundred call seconds) per hour during peak calling times, providing a measure of whether a system can meet or exceed those needs. See traffic concentration. traffic concentration A measure of communications traffic that indicates how different peak traffic periods are compared to traffic on the whole. In telephony, the service day is usually broken down into hours for traffic monitoring to determine high and low traffic periods. Traffic concentration is typically expressed as a ratio of the traffic (number of calls) during the busiest hour to the total traffic during a 24-hour period. This may further be calculated over a period of weekdays, weekends, or 7-day weeks to provide statistical averages. traffic engineering In more traditional communications systems, traffic engineering is the estimation and application of the type, quantity, and configuration of devices and equipment required to meet the needs of a predicted number of users of the system being designed. Experience, trial and error, probability theory, similar system comparison, and insight are all brought into play in designing a system to meet current and predicted future needs. This system works quite well with traditional telephone switching systems and local area networks. As systems become more complex, however, and distributed digital data systems more prevalent, traffic engineering, once the initial equipment is set in place, becomes an even more esoteric process, with much of the configuration and selection carried out by computer software, not just through physical connections. Virtual networks are now laid over physical networks, resulting in several levels of traffic engineering. When these networks are interfaced with a global network like the Internet, then prediction of the number of potential users becomes more difficult and less important than incorporating flexibility and scalability into the system to handle unpredictable traffic loads and activities. At this level, traffic engineering becomes a collaborative activity between programmers and traffic engineers, with careful evaluation of data and message priorities – scheduling and incorporating deliberate delays, for example, so some types of traffic can be set to transmit during off-peak hours. On data networks, many traffic decisions are now built into the software on servers, gateways, routers, and some of the high-end switchers. traffic load The sum total of the traffic on a particular system or portion of a system, such as a specific trunk, leg, or hop, measured at a particular point in time, or during a particular specified range of time. traffic monitor A mechanism for keeping track of traffic on a system. On data networks, some of the software included for system administrators allow the monitoring of various processes, and typically

display them as sampled or realtime graphical charts. Thus, CPU usage, number of users, number of transmissions, level of traffic, etc. can be visually assessed, and statistics derived from computerized traffic and analysis can be stored and evaluated to make changes as needed. The results of the monitoring are sometimes directly incorporated into other software on the system which makes adjustments to priorities, number of users permitted online at one time, and other parameters that can be changed to increase or decrease the traffic to optimize use of the system. Sometimes traffic monitoring is a very simple mechanism. One of the simplest and most familiar applications is on modems, where little blinking lights give some indication of how much data are traveling through the modem, and when. If a user is downloading a large file from a Web site and those lights stop blinking, it’s possible that the connection has been dropped or there is a glitch in the system. In ATM systems, traffic monitoring is an essential aspect of preventing network congestions and bottlenecks, and some cells will be flagged as to their discharge eligibility. See cell rate, leaky bucket. Traffic Operator Position System TOPS. A system to support telephony operators from a toll switch, TOPS was developed by Northern Electric (later Northern Telecom) in the early 1970s, a time when manual cord-based operator terminals were poised to be gradually replaced by automatic stored-program switches. The historic TOPS-1 utilized an Intel 8008 CPU; the first TOPS office was installed in 1975 in Alaska. As computer technologies improved, TOPS was upgraded to faster, more versatile processors. traffic overflow A situation where demand exceeds capacity. When overflow occurs, the traffic is either routed to another trunk or leg, or it is rejected and a signal sent to the user in the form of a signal (like a fast busy) or a text message (as a broadcast on a computer system). In some data networks, particular packets may be discarded if there is traffic overflow, or they may be routed back to the sender. traffic path The physical or virtual pathway taken from the sender to the receiver. This may be fixed, as in direct wire communications and smaller data networks, or it may be flexible, as in switched systems and many larger data networks. On very small systems, where the setup is known and doesn’t often change, a fixed traffic path may be the fastest and most practical implementation. In dynamic data networks, the communication may not be quite as fast, but the system has an advantage in that it can tolerate and adjust to unpredictable changes. A path in a phone system usually passes from the subscriber to a demarcation point, usually a junction box between the internal and external wiring, through one or more switching centers which are connected with pathways called trunks, or sometimes through a wireless link during part or all of the transmission. In a digital computer network, the data may pass from the sender through various servers, gateways, switches, and routers; each section in the path is

called a hop or a leg, with the various terminal points generically called nodes. A data network transmission may also be wireless for part or all of the path. traffic policing In ATM networking, a mechanism which detects and controls cell traffic according to specified parameters. See cell rate. traffic recorder A means to record traffic on a specified transmissions channel in order to monitor capacity, load, efficiency, etc. It may or may not be paired with software that helps analyze the traffic. traffic reporting In networks, information on traffic flow gathered and organized by external analyzing devices or internal monitor agents. This information about packet volume, distribution, collisions, and errors may be reported in the form of tables, ASCII graphs and charts, or images, and is essential for configuration, tuning, and troubleshooting. traffic shaping In ATM networking, a mechanism which shapes or modifies bursty traffic characteristics in order to create the desired traffic. See cell rate. train v. To instruct, teach, indoctrinate, or drill. Training is an important component of any computing system that must recognize input beyond point and click or keyboard instructions. In pen computing, handwriting must be interpreted into commands, and it is usually necessary to train the system, by successive trials and feedback, to recognize an individual’s style of writing. Some camcorders have eye-controlled systems which need to be trained to track the direction of focus of the user’s eye. In voice recognition systems, software is trained to recognize an individual’s mode of speaking. OCR systems can be trained to improve recognition of unfamiliar or unusual character sets. While software training systems are not perfect, they have evolved to the point where they do much useful work, and improvements in technology and software algorithms indicate that some day natural methods of computer input may supersede keyboard and mouse entry for many applications. training An automatic feature of some hardware and software systems to evaluate the characteristics of incoming signals (timing, delay, etc.) or information (handwriting, voice, etc.) and improve performance or recognition through successive adjustments and feedback. See artificial intelligence, expert system, robotics. Training, Planning & Operational Support TPOS. A support function within the Operations Division of the National Communications System (NCS). TPOS coordinates telecommunications operational planning among NCS elements, provides educational seminars, cooperates with other federal and regional organizations, and participates in the Regional Interagency Steering Committee (RISC) meetings. See National Communications System. transaction 1. An agreement, or exchange of information or goods, between two or more parties or entities. 2. A business transaction, which may be subject to various recording requirements (contracts, taxation, audit records, etc.). 3. An entry into a database or spreadsheet.

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transaction, network Any of a number of situations in which information or signals are exchanged, passed on, recorded, or evaluated. Examples of network transactions include protocol determinations and conversions, security-level evaluation and processing, routing, transmission between nodes, error processing, etc. Transaction Capability Application Part TCAP. In the SONET specification, there are several chapters regarding the function, formats, and definitions for TCAP provided in the ANSI T1.114-1996 document. Transaction Team A group with the Office of General Counsel that coordinates the Federal Communication Commission’s (FCC’s) review of applications for major transactions and changes. The Team was announced in January 2000 as a response to an unprecedented number of significant mergers in the telecommunications industry and was tasked with streamlining the review process while still safeguarding the public’s interests. transaction tracking A system of recording each instance of a transaction and, sometimes, the actual transaction or its outcome. In database or spreadsheet applications, for example, each transaction may be recorded as entered, in order to prevent loss of data due to a series of transactions not having been saved at regular intervals. This type of live recording of transactions frees the user from worrying about “saves” and ensures that, under most fault situations, no more than the most recent entry may be lost. See ticket. transatlantic cable A communications link across the Atlantic Ocean incorporating a bundle of wires or, more recently optical fibers, within a tough, corrosion-resistant insulating protective sleeve. The cable is laid along the ocean bottom in regions and at depths where the likelihood of severing by boat anchors is less. Maintenance of oceanic cables is a complicated business, so much emphasis is put on building and installing them correctly in the first place. The invention of the telegraphy in the 1800s provided a strong motivation for laying a cable to bridge the communication gap between North America and Europe. Since postal messages could take from several weeks to several months to traverse the Atlantic, there was a potential goldmine in the provision of cable services. Samuel Morse was one of the more prominent inventors who suggested the feasibility of a cable between North America and Europe. Only three decades elapsed between the development of the first commercially practical telegraphs in England and America and the laying of the first working oceanic cable. The first attempts did not succeed, however, due to problems with installation, insulation, and capacitance over long distances, but improvements in insulation, and trial and error experience, resulted in eventual success. The first working transatlantic cable was installed in August 1858, initiated by F.N. Gisborne’s efforts to interlink maritime Canada, and financed and promoted by Cyrus W. Field. A more permanent installation was realized by Field and his associates in July

1866. An additional link was established between Ireland and Canada, in 1894. Cables to other continents and through other oceans followed as the technology improved. In the 1870s and 1880s, companies were formed to lay cables to South America and Africa. With increasing demands for high-speed wideband communications links for data communications, transatlantic cables are more important than ever; the old wire cables are being replaced by fiber optic cables and new cables are being installed to link regions not previously interlinked. See British Indian Submarine Telegraph Company; Field, Cyrus West; Gisborne, Frederic Newton; gutta-percha; Pender, John; Submarine Telegraph Company.

Prime Minister Richard Bennett (with cabinet members) speaking over a transatlantic telephone to George Perley at the British Empire Trade Fair at Buenos Aires, Argentina, in March 1931. [National Archives of Canada National Film Board image.]

Transcontinental Cable A generic euphemism for the U.S. Defense communications system stretching from Washington, D.C. to California and Florida during and after World War II. It was called this because of the labeling of the dig warning signs located in fields and near garden shed-like repeater stations positioned every few miles along the cable routes across the country. See L CXR. transceiver Device which transmits and receives within a single unit, often sharing circuitry to reduce size and weight. See transmitter, receiver. transcontinental telegraph The first American transcontinental telegraph line was initiated by Hiram Sibley, with encouragement from Ezra Cornell, in the mid-1800s. Sibley, the founder of what was to become Western Union, made a reasonable estimate that it would take 2 years and about $1 million to complete the project. The telegraph line had a significant impact on the new Pony Express service, which had been in operation for less than 2 years when it shut down in October 1861, after inducements to stay in service at least until the telegraph line was completed.

Not surprisingly, problems other than weather plagued the construction of the line. Buffalo discovered that telegraph poles made good scratching posts, sometimes bringing down the poles in their enthusiasm. Native Americans sometimes made off with the wires because the lines stretched through their treaty lands; within days or hours, exquisitely woven copper wire bracelets would appear in local trading markets. Remarkably, despite the great distance, harsh conditions, and the small size of the work crew (only about 50 line workers), the transcontinental telegraph was completed in October 1861. It had taken only 4 months at a fraction of the projected cost, one of the most stunning achievements in western engineering.

A transceiver can transmit and receive signals (though not always on the same frequencies). This tiny radio and intermediate frequency transceiver was developed for the U.S. space program in the early 1990s. [NASA/GRC image archived in 1994.]

transducer A general term for a device which converts one form of energy to another, a process used throughout communications. When sound waves from a telephone conversation come in contact with a telephone mouthpiece diaphragm, the diaphragm causes small polished carbon granules to cohere and the energy is converted to electrical impulses that are transmitted along the phone line. When the mechanical movements of a phonograph stylus are turned into electrical impulses, and then, at the speaker, converted again to audible sound waves, the signal has gone through (at least) two transducers. transformer An electrical device for changing the qualities of a current by mutual induction. Transformers did not come into wide use until the early 1900s, gradually superseding spark coils for providing power for communications and electronic

components. They were similar to spark coils in that they had a core surrounded by conductive windings. However, the core used soft iron sheets rather than a bar. Like a spark coil, two sets of windings, one within the other, were commonly used. The core could be closed or open. Transformers required alternating current and direct current was still prevalent at that time, but the use of alternating current allowed the elimination of a vibrator, as the natural alternations of the current caused inductive discharge. This was more compact and practical than a spark coil. Since many modern electronic appliances (modems, printers, answering machines, model trains) have electrical requirements different from that which comes out of a household socket (110 or 220 AC), the power cord may be equipped with a transformer which modifies the current to the needs of the device being powered (9 or 12V is common). It is important to use the correct transformer; if the voltage is too high, it will likely blow the components. Transient Mobile Unit A mobile communications term for a unit that communicates through a foreign base station. transistor A small device developed in the late 1940s which provided a means to amplify signals with very low power consumption and very little heat. The importance of the transistor to the development and evolution of electronics cannot be overstated. A new world of tiny components opened up, including portable radios, hearing aids, computers, satellites, and much more. See transistor history. transistor history The invention of the transistor in 1947 is widely attributed to William Shockley, John Bardeen, and Walter H. Brattain of Bell Laboratories, although Ralph Brown is sometimes also mentioned. Starting in 1951, when they began to be commercially produced, transistors replaced large, power-hungry, cumbersome vacuum tubes, enabling electronics to be smaller and less expensive, and to run cooler and faster. (There are still some high-frequency applications where the use of vacuum tubes is practical.) The development of the transistor was foreshadowed by the 1926 patent application of Julius Edgar Lilenfeld, who had devised a way to control the flow of current in a solid conducting body by establishing a third potential between the two terminals. Later, in the 1970s, many types of transistors were succeeded by semiconductors. See de Forest, Lee; Kilby, Jack St. Clair; Pickard, Greenleaf. transistor radio A radio developed in the 1950s, based on small semiconductor transistors instead of larger electron tubes. The smaller size and power consumption of transistors made it possible to design handheld portable radios, which became popular and widespread in the early 1960s. Portable radios were not new, since the early crystal detector sets required no outside power and could be carried around in a small case. However, practical, amplified, battery-driven portable radios did not become widespread until the development of small, low-cost transistor components.

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The historic patent for the transistor, an invention which dramatically changed electronics. [U.S. patent document, public domain.]

transistor-transistor logic TTL. A logic circuit design similar to diode transistor logic (DTL), but with multiple emitter transistors. Sometimes called multiemitter transistor logic. transit In network communications, if a provider wants to send data to a destination but does not have the needed routing information, the provider may arrange temporary, permanent, fee or no-fee access (transit) to the destination through a second provider that has the necessary information or access. See peering. transliterate To spell or represent the characters of one alphabet in the closest possible corresponding characters of another alphabet. Transliteration does not imply translation of the actual meaning of words composed of those characters. Western European languages transliterate reasonably well. It is harder to transliterate between Cyrillic and Roman characters, and is decidedly a challenge to transliterate between pictographic or symbolic alphabets, such as Asian languages and sequential, phonetic alphabets such as western European languages. The difficulties in transliteration on computing systems have led to many alternate keyboards, character mappings, and input systems. See Unicode.

transmission The sending of information through electrical signals. It is very common for information to be added to a signal through various forms of signal modulation, often with a carrier wave. See carrier wave, modulation. Transmission Control Protocol TCP. A widely used Internet and local area network (LAN) connectionoriented, packet-switching transmission protocol descended from previous DARPA editions. Together with Internet Protocol, the TCIP/IP combination is a means for the transport of host-to-host information over layer-oriented network architectures. See Internet Protocol, RFC 793. transmission level point TLP. In installation, testing, and maintenance, a point in a conducting line at which the transmission level is measured according to whatever types of signals are sent through the conductor. In telephony, for example, the power level of a voice communication through an alternating current (AC) conductor may be measured in terms of decibels relative to a reference point. transmission medium Any material through which transmission is facilitated either due to its inherent characteristics or through inherent characteristics enhanced by technology. Common transmission media include air, light, wire, coaxial cable, fiber optics, etc. Broadcast transmissions primarily are sent through air, fiber, and coaxial cable. Computer transmissions are typically sent through copper wire or coaxial cable, although the use of fiber is increasing. Various media vary greatly in the amount of information (bandwidth) they can carry at any one time. See individual media for more detailed information. transmitter 1. That which transmits or sends through some means such as chemical, optical, or electrical signals. 2. A device that sends out a signal, such as a transmitting antenna, telegraph instrument, or modem. A transmitter may also include various mechanisms to amplify, compress, modulate, or encode a signal. See telephone transmitter. transparent A transparent technology is one in which the inner workings are not apparent to the user. For example, in computer operating systems with graphical user interfaces, the user sees the applications through point-and-click icons, text windows, and resizable gadgets and dialogs. The conversion of the information into operating instructions, the device drivers, queuing mechanisms, buffers, priority and security mechanisms, and binary arithmetic are essentially in the background, and thus invisible or transparent during typical interactions. Transparent Bit-Oriented Protocol A protocol based on Bit Oriented Protocol (BOP) implemented on a number of Motorola communications products. TBOP is an access port type that accepts BOP frames and turns them into X.25 packets for transmission across a Frame Relay or X.25 network. It then depacketizes them for delivery to an end user device. Thus, BOP is used to transparently pass network information among devices with different protocols. TBOP will pass aborted and damaged frames as well. See Bit Oriented Protocol.

transparent tone in band TTIB. See tone in band. transponder, radio In radio communications, a transceiver that transmits information automatically, on receipt of an appropriate interrogation signal. transponder, satellite In satellite broadcasting, a device which receives and retransmits electromagnetic signals. Broadcast satellites employ this technology with multiple transponders. With compression, the capacity of a transponder can be significantly increased. Transport A, Transport B See broadcast data trigger. Transport Protocol Data Unit TPDU. In the Open Systems Interconnect (OSI) layered network model, the transport layer organizes data into a TPDU, that is, a packet that has had transport layer data added. Similarly, the session layer organizes data into Session Protocol Data Units (SPDUs). The TPDU contains the Transport Service Access Point (TSAP) address and the user’s data (payload). See Protocol Data Unit. Transport Layer Security Protocol TLS Protocol. A client/server-supporting protocol for securing network communications over the Internet. TLS is intended to deter eavesdropping, tampering, or forging of messages. It was submitted as a Standards Track RFC by Dierks and Allen in January 1999. The TLS Protocol is primarily intended to provide privacy and data integrity between two communicating applications. It is composed of the TLS Record and TLS Handshake protocols. The TLS Record Protocol is layered over a reliable transport protocol and provides connection security in terms of privacy and reliability through encapsulation of higher level protocols. The TLS Handshake Protocol enables authentication of the client/server relationship and the negotiation of an encryption algorithm and cryptographic keys prior to data transmission. See RFC 2246. Transport Service Data Unit TSDU. In the Open Systems Interconnect (OSI) model, an item of information passed by the network transport user to the transport provider. In the Transport Protocol Data Unit structure, all the data of the TSDU comprise the User Data. In the ISO-SP protocol, up to four session protocol data units together may comprise the TSDU. transportable cellular phone A transportable phone consisting of a handset, antenna, and battery, usually bundled together in a carrying bag (sometimes known as “bag phones”). It’s a little heavier than a self-contained, handheld cellular phone. This type of phone can operate on up to 3 W of power. It can be operated independently of a car battery and is typically used for field work that requires a phone with greater mobility and, sometimes, a larger antenna and longer life battery. It may include fax and modem features, and may be used in conjunction with a laptop. Journalists, scientists, and business people who need something a little more full-featured than a simple handset system use transportable systems. trap To confine, narrow in on, circumscribe, or surround, especially with the implication that the

object, person, or function cannot subsequently escape. trap door A hidden device or software mechanism that causes a naive user to “fall” into an application, environment, or system, while assuming it is a legitimate user account. The user then tries to access normal applications, for example, leaving a trail of activities that can be logged, so that the trap door programmer can later search the log for usernames, passwords, or other information that can be used to penetrate an account. Since the user may begin to notice that the environment is not quite the same as normal, a trap door program may “inadvertently” crash or log out the user (or, on a network, say the system is going down and advise the user to log out) in order to escape detection. The next time the user logs on to the genuine account, everything is normal. See back door, Trojan horse, virus. trapping In printing, a technique for assuring that adjacent inks meet, or slightly overlap so there won’t be an undesirable, paper-colored gap between the inks if the registration of the press is slightly off. When a user creates desktop publishing page layouts intended for printing at high resolutions, settings must usually be adjusted to maximize trapping to ensure the quality of the final product. Typically, small, light-colored objects like fonts are trapped (slightly overlapped) over dark ones, so that the detail in the small objects is not lost. See choking. traveling user TU. In a Secure Data Network System (SDNS), a traveling user is one who is visiting a Message Security Protocol-equipped (MSPequipped) facility other than the usual one where the user reads and sends messages. In networks in general, a TU is someone who may interconnect or interact with a network from a variety of facilities while traveling. This type of network access is increasing as mobile systems become more prevalent. traveling-wave tube TWT. A tube in which a stream of electrons interacts in a more-or-less synchronized manner with a directed electromagnetic wave so energy transfers from the stream to the wave. The basic aspects of a TWT include an electron gun for producing a high-density electron beam, a microwave circuit supporting a traveling electromagnetic wave through which the beam travels, and a collector to collect what is left of the electron beam that passed through the microwave slow-wave circuit. Amplification is attained through proximity of the electron beam to the traveling electromagnetic wave housed within a structure designed to propagate the wave. TWTs evolved from magnetron microwave-generating tubes, emerging during the latter part of World War II. The TWT was designed by inventor Rudolf Kompfner, and later improved by Kompfner and John R. Pierce at Bell Telephone Laboratories. The Hughes Aircraft Company subsequently became a significant developer of military and commercial TWTs. The TWT was originally developed to support emerging radar technologies and is now also an important component in communications satellites and missile-seeking circuits. See cavity magnetron, magnetron.

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TRE See Telecommunications Research Establishment. tree structure A common structure in computer programming and file organization. A tree branches from a main trunk to its various branches, just as the roots successively branch into subdivisions as you move away from the main trunk. Data branching structures are found in various database data storage schemes, file directory structures, fractal images, and more. Physical branching structures are found in network topologies; for example, branches may come off a backbone and branch further in individual local area networks (LANs). Physical branching also occurs in phone circuits, with a main switching station supplying local private branches, which further subdivide to service individual lines within the local branch. Programmers use various types of tree structures including binary trees, B trees, B* trees, etc. TREG See Telecommunications Regulatory Email Grapevine. trellis coding A source coding technique used in a variety of contexts, from high-speed modems to MPEG decoding, to produce a sequence of bits from an incoming stream that conforms to certain desired characteristics. TRL transistor-resistor logic. Also called resistortransistor logic (RTL). Varying numbers and types of transistors and resistors combined in a circuit to comprise and control the logical operations of which the circuit is capable. TRIBES Tri-Band Earth Station. A commercial satellite tracking station from California Microwave, Inc. (CMI), operating on C-, X-, and Ku-Band frequencies, aimed at government applications. TRIBES-Lite is a downsized version. triboelectricity Electricity generated by friction, as in a bicycle wheel-mounted generator that becomes charged when the wheel is spun and rubs against the generator contact surface. Triboelectricity can also be generated by rubbing a balloon on a person’s hair, enabling the balloon to magnetically be attached to walls or other surfaces until the electricity dissipates again. See mutual capacitance, static electricity. tributary Secondary, or subsidiary peripheral, signal or process. Subsidiary peripherals receive their control data from servers or devices higher up in a hierarchical network. Subsidiaries may be aggregated to create a combination medium or signal. See tree structure. triode An electron tube with three primary elements: an electron-emitting cathode, an electron-attracting anode, and a grid superimposed so that it can be used to control the flow of electrons. The invention of the triode by Lee de Forest, who named his commercial triode the Audion, is one of the most significant developments in the history of electronics. Prior to the addition of the third element, it was not possible to control the electron flow to any useful degree. See Audion. TRIP 1. See Telephony Routing Over IP. 2. See Token-Ring Interface Processor. Trivial File Transfer Protocol TFTP. A simplified,

lock-step client/server version of File Transfer Protocol (FTP) for reading and writing files over networks. TFTP was originally developed to work with diskless workstations but has since been applied to other applications. TFTP is easily implemented over Internet Protocol (IP) and provides only the most basic file transfer features. It is encapsulated in UDP (standard over port 69) rather than TCP. A multicast option suggests a way to use multicast packets to allow multiple clients to concurrently receive the same file. See Enhanced Trivial FTP, Simple File Transfer Protocol, RFC 1350, RFC 2090. trn A versatile, full-screen news reading program developed by Wayne Davison as a superset of rn, written by Larry Wall. This incarnation adds threads through a hierarchical database. Trojan horse A computer program that appears to be one thing, like a gift or incentive, but actually hides something more malicious or invasive, such as a virus or other program that can infect a host system and potentially change or damage it. The name comes from the Trojan War during which Troy was penetrated by the gift of a great wooden horse. Once inside the fortress, soldiers swarmed from the horse to do battle with the surprised recipients. Thus, a Trojan horse program is a program disguised as something desirable or benign, a pirate program, computer game, popular utility, appealing Web site, etc., in order to attract users. If the Trojan horse is an executable masquerading as a game, for example, running it unleashes its ability to change or take over a system. Unlike the Battle of Troy, however, the victim may not realize his or her system has been invaded. The computer version of a Trojan horse can be much stealthier than its historical counterpart while surveilling or damaging a system. Trojan horse programs are actually a particular type of masquerade program, by virtue of the fact that they offer something free or otherwise appealing. One example of a Trojan horse program is a frontend that looks like a normal interface, but is really a visually or functionally identical layer on top of or instead of the interface that leads to something desired or appealing. It is designed to capture information to be used later for penetration of the system. For example, a programmer might create software that looks like a popular Web site or a network login prompt and then circulate information to entice people to use it. The user sits down at the terminal, registers for the service or types in an existing name and password, and gets an error message (from the Trojan horse) that the password was entered incorrectly, try again, or that displays something appealing and masks the fact that the username/password has been captured. The user sees a normal login prompt without being aware of the deception, types the password again, and logs in successfully or simply continues to browse the site if the password prompt was fake. The writer of the Trojan horse has grabbed a name and password, with a low chance of detection by the user, and may now be able to access the user’s account by means that are difficult to detect as unauthorized access.

An Internet masquerade program was distributed in bulk email messages in summer 2001, when PayPal online banking services were becoming popular. The businesslike innocent-looking email message had an embedded link to a fake PayPal Web site called paypaI instead of paypal. The difference is that it used a capital “i” instead of an “l” (el), something few people would notice. When users tried to log on to the fake PayPal account with their usernames and passwords, the information was captured so that their real PayPal bank accounts could be accessed by the people who designed the masquerade. Fortunately, the ruse was discovered and reported quickly, but this example illustrates the potential for harming a large base of computer-naive Internet users. See back door, trap door, virus. troposphere The lower layer of Earth’s atmosphere, which contains clouds and most of the air, varying from a height of about 10,000 m at the poles to about 18,000 m at the equator. In radio transmissions, some frequencies can be bounced off the troposphere, that is, bent back to earth through super-refraction. See ionosphere, tropospheric scatter, tropospheric scatter transmission, tropospheric wave. tropospheric scatter The dispersion and propagation of waves resulting from the varied and discontinuous physical properties of the troposphere. This can be predicted and controlled sufficiently to be useful in communications. See tropospheric scatter transmission. tropospheric scatter transmission A method of electromagnetic wave propagation, employing frequency modulation, that exploits the irregular propagation properties of the troposphere. Tropospheric scatter transmission is a way to propagate, for example, microwave transmissions for thousands of miles, in segments up to about 500 miles per hop. tropospheric wave The troposphere includes a diversity of moisture, heat, and other properties which can result in electromagnetic waves that undergo abrupt changes sufficient to create tropospheric waves distinguishable from the original tropospheric scatter transmission waves. trouble unit A systems diagnostic or descriptive measure to indicate the expected performance of a circuit over a given period of time. TRS See Telephone Relay Service. TRS-80 computer A mass market microcomputer series introduced by Tandy/Radio Shack in the mid1970s, at one time said to have 80% of the microcomputer market share. It ran quite effectively at 1.8 MHz with 4 Kbytes (not Mbytes) of RAM. It was in the same computing generation as the first Apple computer and the Commodore Pet. The TRS-80 featured the Z80 chip, a monochrome screen, built-in BASIC programming language, and ran a variety of applications including Scripsit and Electric Pencil word processing, VisiCalc spreadsheet, and the Scott Adams adventure game series. For telecommunications, it could be equipped with an internal PC board that interfaced with the old suction-cup style acoustic modems, and later with direct-connect modems, to dial into local BBSs and

forerunners to the Internet. Leo Cristofferson and David Lien contributed highquality educational recreations for the TRS-80, and Louis Rosenfelder wrote one of the best books on BASIC applications programming. A TRS-80 enhanced clone series called the LNW-80 designed by a California company called LNW Research never got the market share it deserved. It featured a faster CPU, higher memory capacity, and color screen and was arguably superior to the TRS-80 and the Apple computer. The TRS-80 series ran quite a variety of operating systems, including TRS-DOS, LDOS, CP/M, and others. (Consumers may not realize that they aren’t tied to one operating system; a variety of OSs can run on current hardware platforms, just as they did on far more limited systems in the 1970s.) Various TRS-80s were shipped over the next decade, the most well-known being the TRS-80 Model I and the Model III, and the historic laptop, the TRS-80 Model 100, which caught the attention of journalists and traveling sales reps in the early 1980s and was still used by some of them 16 years later! In spite of its strong start, good distribution, and commercial success, the TRS-80 series did not survive the introduction of IBM computers to the marketplace. While Radio Shack computers were targeted at both business and personal users, business users were nevertheless conservative and slow to adopt the new technology. They wanted warranties, assurances, service contracts, and familiarity with the company providing the equipment. Despite the high price and very limited capabilities of the early IBM computers, the IBM name and service guarantees made them the computers of choice, especially with Apple targeting the education and home markets. The Tandy series of computers continued under the Tandy name, but their visibility had dropped substantially by the late 1980s, and Intel-based machines cornered most of the business market by then. See Altair, Apple computer. TRU See tone receiver unit. true bearing A bearing given with relation to geographic north (north as it is shown on a globe), rather than magnetic north (the north to which the northseeking end of a compass needle points). true north The Earth’s geographic north. See magnetic north. TrueType A system of widely used scalable vectorformat fonts developed by Microsoft Incorporated. See vector fonts. truncation 1. Cutting or chopping off at an end, sometimes abruptly. 2. The quick or abrupt termination of an operation or process. 3. The removal of characters from the end of a word or numeral, as in reducing a four-decimal numeral to two decimals without altering the numerals remaining (i.e., not rounding). Truncation applies to either the leading or trailing end, but more often than not, the part truncated tends to be the trailing end. trunk A communications link between two switches or distribution points. A generic term that applies to

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many technologies, but is most often used in connection with telephone and network lines. Trunks can be set up to be bidirectional (left to right to left) or unidirectional (right to left or left to right). See path, route. trunk carrier In the past, this has referred to any telephone voice network trunk connection. It is now also more specifically associated with the digitally multiplexed carrier systems used for digitized voice and data in North America, Europe, and Japan. The T-carrier system (for Trunk-carrier) in North America was the first of the X-carrier systems to be established, with Europe and Japan quickly adopting versions of it called the E-carrier and J-carrier systems, respectively. In general concept and format, these systems are similar. In actual implementation, some important differences preclude direct compatibility. The Trunk Carrier Implementations chart illustrates the similarities and differences in terms of data rates and number of voice/data channels available in the three systems. See E-carrier, J-carrier, T-carrier. trunk exchange Hierarchically, a higher-level, specialized telephone exchange facility dedicated to interconnecting trunk lines (which, in turn, connect telephone services users and carriers). The concept of a telephone trunk appears to date back to sometime around the 1890s. In the earliest manually operated switchboard systems, two operators were used to set up a trunk relay in which one would answer the calls coming from outside the exchange and the second would then connect the call to the appropriate local subscriber. In some of the historic telephone exchange diagrams, the first operator was designated “A” with the second designated “B” to illustrate the steps involved. Outgoing calls from the local exchange would go to Operator B and be passed on to Operator A to be connected to a line outside the local area. trunk group A group of trunks sharing essentially the same electrical characteristics and often the same physical characteristics connecting to the same switching endpoints or connections. Multiple trunks

are common in areas where one trunk would not be sufficient to carry the traffic. If the main trunk is busy, traffic may be manually or automatically switched to the next one in the group, and so on. See trunk hunting. trunk hunting A call management system that seeks an available communications trunk over which to route a call. Economy is achieved by hunting the most frequently used trunks first. See hunting. trunk link frame TLF. In a crossbar telephone switching center there would be a frame supporting the links where subscriber telephone lines connected into the central office (CO) and a frame supporting the wires connecting to other switching offices. The lines connecting to other switching centers were terminated on the trunk link frames. The subscriber’s line could thus be connected to another subscriber in the same local service area or to one of the trunk link circuits leading out of the service area on the trunk link frame connected to the appropriate remote office. TS 1. See Technical Specification. 2. transmission scheme. TSACC See Telecommunications Standards Advisory Council of Canada. TSAG See Telecommunication Standardization Advisory Group. TSAP See Transport Service Access Point. TSAPI See Telephony Services Application Programming Interface. TSAPI Service Provider TSP. A software driver that enables a TSAPI device to be adapted to a vendor’s private branch exchange (PBX) system. The TSP may be used in conjunction with other computer telephony integration (CTI) products, but is the minimum essential software that links the systems. See Telephony Services Application Programming Interface. TSB See Telecommunication Standardization Bureau. TSDU See Transport Service Data Unit. TSO time share operation.

Trunk Carrier Implementations for Voice/Data Lines Desig.

J-1 Mbps

-0

.064

1

64 Kbps

1

.064

1

-1

1.544

24

1.544

24

2.048

30

-1C

3.152

48

3.152

48

-2

6.312

96

3.152

48

8.448

120

-3

32.064

480

6.312

96

34.368

480

-3C

97.728

1440

44.736

672

-4

397.200

5760

274.176

4032

139.268

1920

565.148

7680

-5

J-1 Chan.

T-1 Mbps

T-1 Chan.

E-1 Mbps

E-1 Chan.

TSP 1. See Telecommunications Service Priority. 2. See TSAPI Service Provider. TSR tag-switching router. See tag switching. TSRM Telecommunication Standards Reference Manual. TTA See Telecommunications Technology Association. TTAB transparent tone above band. See tone above band. TTC See Telecommunications Technology Committee. TTIB transparent tone in band. See tone in band. TTL See transistor-transistor logic. TTS text-to-speech. A type of speech synthesizer. TTY service Teletype service. Depending upon the area, this is a teletype service made available to those with hearing impairments, at a price commensurate with that paid by regular telephone subscribers. The program is supported through the combined fees paid by all subscribers in a region. Eligibility for the service is usually determined by local health services agencies. TU See traveling user. TUANZ Telecommunications Users Association of New Zealand. TUBA TCP and UDP with Bigger Address. One of three candidate protocol proposals eventually blended into IPv6 by the Internet Engineering Task Force (IETF). See IPv6. TUC 1. total user calls. An accounting/administrative count of the total number of calls made per a specified period. 2. See Total User Cells. TUG Telecommunication User Group. TUI See telephone user interface. tumbling A type of cell phone fraud that involves successively switching the electronic serial number for each call too quickly for the cell operator to detect the user. tungsten A heavy metallic element with properties similar to chromium and molybdenum used in electrical installations, filaments, and contact points, and for hardening alloys. tuning To adjust to resonate at a particular wavelength, as setting an instrument to a specific pitch or setting a radio antenna or tuner to receive a particular frequency of radiant energy. See tuning coil. tuning coil A winding coil specifically configured to pick up certain frequencies of radiant energy, particularly radio waves. Early tuning coils consisted of nothing more complicated than a coil of fine conductive wire wound around a wooden or rubber core, with the coil in circuit with a connecting pin or pins. Tuning coils for consumer sets tended to range from the size of a sewing spool to about the size of a human hand. Often they were stored like thread in banks or rows on little wooden shelves, so that the appropriate frequency coil could quickly be selected and inserted in a connector on the radio. The wire on each coil would be slightly different, to pull in a different frequency range, with different thicknesses and spacing between successive windings.

Sometimes a small sliding tab or knob attached to a bar would be placed along the edge of the winding, in order to make contact with a specific portion of the winding to provide further fine control. This was called a slide contact. Other tuning coils used a type of intricate basket weaving in various patterns supported by a slender frame in such a way that a lot of wire could be wound into a small space and no cylindrical spool used. See basket winding, coil.

Historic radio tuning coils resemble large spools. They often came in sets, designed for different frequencies, and could plug into the circuit by means of two or more prongs.

Since tuning coils could be purchased in sets, they often included a base to keep the coils in order and protected from damage. These excellent examples are from the American Radio Museum collection.

tunnel n. 1. A hollow tube, conduit, or passageway through an obstruction. 2. In software, an intermediary program that provides a temporary relay between connections without interpreting or otherwise changing the content of the communication. A tunnel often provides a temporary portal for passing data through a system such as a proxy, and ceases to exist when the ends of the connection are closed. tunneling 1. Encapsulating a network transmission in an IP packet for secure transmission over a network. See virtual private network. 2. To temporarily reroute a network transmission packet in order to utilize routers which would not normally be able to route the transmission to the original destination due to not having the needed destination entry. TUR Traffic Usage Recorder. Turing, Alan Mathison (1912-1954) A British mathematician who traveled to Princeton in 1936, where he studied as a graduate student, and wrote On Computable Numbers ... He proposed some provocative ideas in ordinal logics and created a cipher machine while at Princeton, but Turing is best remembered

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for his description of a hypothetical device which could handle logical operations and manipulate symbols on infinite paper tape. This Universal Turing Machine is described as a finite state machine due to the finite set of instructions from which individual actions were derived. This provided the roots for thinking about computers in terms of algorithms and equations, and for positing devices that could be used for all possible tasks. Many of the conceptual roots of computer science, particularly general purpose machines and reusable code, were developed through his research. See Turing machine. Turing machine A hypothetical model devised by Alan M. Turing, which could handle logical operations and manipulate symbols on infinite paper tape. This Turing machine is described as a finite state machine due to the finite set of instructions from which individual actions were derived at that point. Many extrapolations from and implementations of these basic concepts have contributed to the development of computing devices. See Turing test. Turing test In 1950, Alan Turing published “Computing Machinery and Intelligence” in Mind, a philosophical journal. In it much of his thinking of the last few years was put into print, providing an effective inspiration to many future scientists and providing some of the concepts that developed into the field of artificial intelligence (AI). The Turing test was a provocative assertion that computers would, in the succeeding 50 years, be able to pass for a human under certain test conditions. Imaginative efforts to support this prediction have led to a wide variety of interesting programs, and prizes are offered for innovative software that can pass the Turing test. turnaround time The time of a transaction, especially one that passes from one hand to others and back, as in sending something to another department or external service bureau. For example, the turnaround time for printing a brochure may be 2 weeks from the time it leaves the hands of the in-house layout production staff until it returns, printed and folded, in boxes of 500 each. 2. In network transmissions, the time it takes to send a transmission and receive an acknowledgment that the transmission was received, or can continue. 3. In detecting or pinging another system, the time it takes for the signal to reach the other system, and report back statistics on the connection. The phrase turnaround time is sometimes applied loosely to the time it takes for a human to send out a signal and receive an acknowledgment, and sometimes more precisely to the number of clock cycles or actual measured time it takes for the signal to leave the sending site, reach the receiving site, and report back to the sending site, used for system diagnostics and tuning. Or even more specifically, in handshaking or half-duplex applications, turnaround time is the interval that occurs when the system switches to communication in the other direction. In terms of half-duplex satellite phone conversations, this turnaround time is perceived as a blip, lag, or break in the line by the callers, and, if it is long, can be quite distracting to the conversation. See hysteresis.

turnkey system A self-contained system that can be purchased, installed, or relocated as a unit or as a package. Turnkey systems typically arise from two situations: 1. The technology is complex and the vendor combines options in such a way that the system meets a need but need not be configured or technically understood by the user. The user simply purchases it, turns it on, and uses it. For example, many video outlets bundled Video Toaster systems as turnkey solutions for desktop video applications. 2. Many options are available for configuring a system, and the vendor best knows how to combine and configure the individual components to meet the needs of the purchaser. Private branch telephone systems and multiline telephone systems with lots of options are often bundled and purchased this way. turnstile antenna An antenna comprising two dipole antennas perpendicular to one another with axes intersecting at their midpoints. turntable 1. A round, rotating platter, frequently with a central shaft or outer rim to hold objects in place, commonly used for playing audio and visual media, especially vinyl phonograph records. 2. A round, rotatable, platelike surface designed to give easy access to objects placed on it by turning. A Lazy Susan. Turntables are used in loading platforms, cupboards, microwave ovens, and Chinese food restaurant tables.

The Hillis/Papert turtle was a delightful, educational, interactive, hands-on teaching tool for helping children learn the essential characteristics and relationships of programming concepts by translating them into movement.

turtle The common name for a programmable turtleshaped robot designed by William D. Hillis, a graduate student at MIT. Hillis’ work arose from the writings and development of the LOGO programming language by Seymour Papert at the MIT Artificial Intelligence Laboratory in the 1960s. LOGO was a LISP-like language intended for robot control. A great deal of excitement was inspired by Papert and Hillis’ inventions when microcomputers became available to schools and homes. Finally, there was a mechanism for teaching LOGO and downloading the programs to the little turtles commercially introduced

in 1978. The Terrapin Turtle was acknowledged by many to be an excellent educational resource for teaching robotics, guidance, artificial intelligence, computer programming, and much more, in a fun, interactive context. TVM See time-varying media. Simplified images of four types of cables commonly used in telephony, video, and data cabling.

UTP

}

water-resistant sheath

copper wire conducting pairs

color-coded insulation

} blue blue/white } orange orange/white } green green/white } brown brown/whhite

CAT5 water-resistant sheath

secondary conductor insulating layer

COAXIAL cladding

copper wire conducting core

individual fibers or fiber bundles core

FIBER Top: A basic unshielded twisted-pair (UTP) cable; two-wire and four-wire UTP cables are especially common in telephone wiring (the copper pairs are entwined within the sheath). Shielded twisted pair (STP) looks similar, but has an insulating shield under the water-resistant sheath. The outer sheath is not necessary for all types of wiring, but is commonly used. Middle: Category 5 unshielded twisted-pair (UTP) cable suitable for the higher demands of data cables. Pairs are typically identified by color schemes that include a solid color and a paired striped wire of the same color. For applications such as Ethernet, the wires are usually attached to an RJ-45 connector that resembles a fat phone cable connector. Lower Middle: Coaxial cable, so-called because two conductors are housed within the covering, separated by an insulating layer to reduce crosstalk and to prevent short circuits that would occur if the two conducting layers touched. This is commonly used for video transmissions. Bottom: Fiber optic cable based upon light-guiding filaments rather than electricity-conducting wire. This is commonly used for fast digital data communications. The three top cables use copper for the central conducting core.

TVRO television receive-only TWAIN An image-oriented communications protocol standard widely used in computer scanning devices and digital cameras (which are, in essence, portable scanners). Most high-end graphics programs can handle TWAIN-compliant devices, as can many optical character recognition systems. TWAIN is supported and promoted by a number of graphics industry vendors, including Eastman Kodak, HewlettPackard, UMAX, Adobe Systems, and others. See Tag Image File Format. tweak freak A technical user who is exaggeratedly interested in the inner workings, whys, and wherefores of the tiniest technical details in a system. This characteristic is an asset when diagnostics and fine-tuning are needed, and a liability in general social situations. twinning Systems configured in parallel to create redundancy, or alternate means of access or transmission. Twinning is sometimes done to install a new system while an old one is still used, or to provide a backup in the case of emergencies. In newer technologies, twinning can provide backups or transition systems until the old system is little used or phased out, such as twinning word processors with typewriters or physical facsimile machines with software facsimile programs. twist length Also called lay length, this is the distance from one twist to the next in a twisted-pair conducting cable. For example, a cable with a lay length of 4 inches will correspond to three twists per foot or 3 TPF. In electrical-conducting wires, the twist length is kept as short as possible and helps to electromagnetically couple the cable while reducing crosstalk. In light-conducting fiber optic cables, the twist serves a physical bundling purpose rather than an electrical coupling purpose. Helical twisting together of the tiny fiber optic filaments facilitates the installation of the cable and provides added strength. See twistedpair cable, twists per foot. twisted-pair cable Twin strands or cores of intertwined, insulated copper wire, a wire type used for many decades in the telephone industry. The twists are organized to help reduce interference in wires that are kept as close to inhabiting the same physical space as is possible. Thicker cables tend to provide cleaner transmissions, at a higher cost. Unshielded twisted pair (UTP) is commonly sold as four pairs of 24-gauge wire. Shielded twisted pair (STP) is commonly used in applications where there may be interference from other nearby electrical sources. Although the theoretic data transmission limit of twisted pair has been underestimated many times, and improved with new ideas and data protocol schemes, it is generally accepted that their practical capacity under normal operations is about 56 kbps. Twisted pair is now also commonly used in Ethernet LAN connections. Twisted-pair cable is sold commercially in several grades of transmission performance. See category of performance. See twists per foot.

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twists per foot TPF. A measure of the number of twists (helical intertwinings) per foot length in a pair of wires called twisted-pair wiring cable. The density of the twists per length affects the bulk and flexibility of the cable and the degree of electromagnetic emanations associated with the wire when it is used as an electrical conductor. Increased twisting generally increases the transmissions length. Uneven twists are generally used to reduce interference along the line from crosstalk and external sources. There are industry standards for the number of twists per foot. For example, for Category 1 and Category 3 plenum and PVC for cables for regular applications, there are at least two TPF. Category 3 cables for telephony applications typically have 3 TPF with a gauge of 22 to 24 AWG. Cat 5 cable, suitable for the higher demands of fast data communications, may range from 8 to 36 TPF. The number of twists depends upon wire gauge, data transfer rates supported, and the number of twisted pairs included in a bundle. High-quality cables usually have evenly spaced twists that do not overlap. Different twist lengths in bundled cables can further aid in minimizing crosstalk. American Wire Gauge (AWG) #18 cable has 5 TPF. See twist length. two electrode vacuum tube A historically important, but ultimately not very useful early vacuum tube. The two-electrode tube consisted of a simple filament (cathode) and an electron-attracting plate (anode). With no controlling mechanism, it wasn’t of much practical use, but it was a history-making invention in the sense that it led to the three-element tube with a controlling grid that subsequently opened the door to the entire electronics industry. See Audion; de Forest, Lee. two tone keying A means of using two tones, one for mark and one for space, to modulate a telegraph signal so as to create two channels transmitting in the same direction. two-phase coding A means of increasing data transmissions by splitting the signal into two orthogonal channels, one which is in phase and one which is a quadrature signal. They are then transmitted simultaneously with this 90 degree phase offset, each operating at half the data rate of the originating signal. Thus, a signal might be transmitted at the same data rate in half the bandwidth, but for the trade-off of converting it from a baseband signal to a passband signal when splitting it into two channels. The increased potential for noise, when two signals are transmitted simultaneously is also a consideration. two-way trunk A network trunk which operates in both directions. In the case of telephone service trunk lines, it refers to one which can be seized from either end of the connection, as opposed to one-way trunks, which may be set up to send only or receive only. TWS two-way simultaneous. A mode in which a router optimizes communications over a full-duplex serial line. TWT See traveling-wave tube.

TWX Teletype-Writer Exchange. A Bell system printing telegraph service which could operate over the existing long distance network, established in the 1930s. In 1970, Western Union purchased the TWX service from AT&T and merged it into its own Telex service. See Western Union. Twyman-Green interferometer See interferometer. Tx, TX transmit. TxD transmit data. A data channel, typically used in serial communications, which is an output for DTE devices and input for DCE devices. See DTR, DSR, RTS, RxD, RS-232. TYMNET A historic, commercial, X.25-based data network access service descended from the ARPANET. TYMNET became available in 1974, not long after Telenet was offered, at dialup-line speeds of 300 baud! The service was offering faster data rates (1200-baud) within a few years. By the mid-1980s 2400-baud service was offered, with 9600-baud following in the late 1980s. This is pretty slow compared to current T1, ISDN, DSL, and cable modem standards, but 9600 was pretty ripping in the 1980s. TYMNET grew and internationalized, with nodes assigned regionally, which may not seem impressive to current Internet users, but in those days, regional nodes made it possible, in some countries, to dial TYMNET as a local call from anywhere in the region. It was a pretty exciting development at the time and a foreshadowing of global network access. A large number of companies eventually offered timeshare or database information services over TYMNET, including Compuserve, Cybershare, the European Space Agency (ESA), Dow Jones, Dun and Bradstreet, Xerox Computer Services, and many more. TYMNET could be accessed in a number of ways, including through Datapac links. With the advent of the Internet, TYMNET has been all but forgotten, but it holds an important place in the growth of shared computing resources and access to computers by the general public. Type 1/Type 2/Type x card A standardized, compact data card commonly used for modems, memory, and other plugin accessories for computers, digital cameras, and more. See PCMCIA card, PCMCIA standards. Type 1/Type3 font The designations for the most commonly used PostScript-format ASCII or binary outline (vector) font format first released by Adobe Systems in the mid-1980s. The character shapes for symbols in the fonts are defined in PostScript so that they can be printed from the vector description to the best possible resolution possible on a PostScriptcompatible output device such as an Apple LaserWriter or high-end printer’s image-setting machine. In simple terms, this means they look good if they are printed small and they still look good when they are printed billboard size, because the shapes are mathematically derived rather than being scaled up, as with bitmapped raster images. To support kerning, spacing, and other aspects important in layout not directly contained in the font files, there are supporting Adobe Font Metric (AFM)

files. These are simple ASCII files that, in general, are freely distributable to add functionality to the proprietary PostScript fonts. Type 1 and Type 3 fonts are not just character shapes, they are expressions created with a programming language, which means the characters can be swirled and manipulated and set across curved surfaces in a way that regular fonts cannot. In theory, PostScript fonts could even be animated. Type 3 fonts have some additional capabilities for special effects. PostScript Type 1 fonts are largely responsible for the desktop publishing revolution that occurred in the mid-1980s when Macintosh computers and PostScript-capable LaserWriter printers were paired up with desktop publishing software. Before 1984, typesetting machines costs hundreds of thousands of dollars and the general public couldn’t do much better than searching out a proportional typewriter (a special kind of typewriter not generally available) for typesetting their own books and documents on a budget. With desktop publishing and PostScript fonts it suddenly became possible to create beautiful documents with professional quality fonts (even at 4 points in size) that rivaled those of professional printing systems. Hinting is a process of fine adjustments to the font shapes in PostScript fonts to make them look better than what might be expected at low resolutions such as 300 dots per inch. Other beta and specialized releases of PostScript Type x fonts for applications support the printing of TrueType fonts on a PostScript-enabled device. See PostScript. type bar A bar, typically made of metal, installed in an impact printer such as a line or page printer, which is embossed with the printable characters and used to impress the characters onto the printing medium, usually through a carbon ribbon. A similar concept is used on pressure label makers, which use dialable characters to select a line of characters which are then impressed upon the printing medium. Type of Service ToS. Type of Service is both a generic concept in networking and a specific parameter related to Internet Protocol communications. It describes and determines various networking parameters related to speed, security, format, etc. As with many types of network services, there may be tradeoffs between speed, flexibility, and security, depending upon how ToS is specified at any particular time or on specific types of networks. ToS is now mandated by the Requirements for Internet Hosts specifications described in the various relevant Requests for Comments (RFC) documents. At the present time, support for ToS is somewhat uneven and there are known problems on some prevalent systems. In Internet Protocol (IP), a byte in the IP header supports Type of Service information. The byte is divided into the precedence field, the TOS field, and a reserved bit, only one of which may be set at a time. It is recommended that routers be cognizant of the ToS value for a route in the routing table. If the routing

protocol does not support ToS header settings, the ToS must be assigned the default value of zero (0). Physical Link Security Type of Service was described as an RFC by D. Eastlake in May 1993. It was submitted as an experimental protocol providing a ToS to request maximum physical link security in addition to existing types of services in the Internet Protocol (IP) Suite. This ToS requests protection against surreptitious observation by agents labeled as outside the traffic. When transporting SNA network traffic over TCP/ IP networks, there are issues with preserving the SNA Class of Service (CoS) parameters. Cisco addressed this issue by developing a data-link switching enhancement (DLSw+) to improve response time and the effective use of bandwidth while supporting SNA Type of Service (ToS) over TCP/IP to ensure preservation of SNA CoS traffic parameters and aid networks in prioritizing SNA traffic. Programmers have created tables and software utilities to streamline the processing of ToS settings. For example, iptables allows a table to be constructed with predetermined values that can be matched to the datagrams being processed. Thus, only those with matching patterns are processed. Masking utilities are available for accomplishing a similar task, but with more power and flexibility. In NIKHEF ping code, TOS bits can be set to enable the user to set priorities for the ping query. Settings are between 0 and 255. See RFC 1455, 1812. typeahead 1. A capability of systems to store or buffer commands entered by the user, so that they can be executed after the current instructions have been completed. For example, a fast typist using a slow word processor system might be able to type faster than the word processor can display the characters on a screen. Typeahead allows the characters to be stored and displayed as the display system catches up with the faster processing system. 2. Better phone menu systems using touchtones have a typeahead capability which allows a user to type further menu selections before the current instructions have been completed. typeface, typestyle, type family A collection of character sets with an overall aesthetic relationship, which may include a number of styles (bold, oblique, italic, condensed, display, etc.) and sizes. For example, Helvetica and Times are common typefaces. Typefaces are commonly used in printing, and computer printers are capable of rendering a wide variety of fonts. See font, PostScript, TrueType. typesetting and composition The art and process of laying out a page with type in order to transcribe information into written form and to present it visually so that the composition enhances the reader’s ability to understand and appreciate the information. In most cases, the type is then transferred to a printing press for the creation of multiple impressions. The selection of type, its organization, visual relationships, and aesthetics are all considered toward these ends.

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The automation of typesetting began in the late 1800s when the ability to provide electricity and control machines and the flow of information made it possible to create typesetting machines. Early typesetters, also called type-compositors, that were developed around the late 1880s were of two types: those which

employed movable type and those in which the type materials were cast line-by-line in mold-beds of assembled matrices. Each of these types of machines was operated through keyboards, like those of typewriters, thus removing the traditional hands-on positioning of type.

U interface In ISDN, a number of reference points have been specified as R, S, T, U, and V interfaces. To establish ISDN services, the telephone company typically has to install a number of wirelines and devices to create the all-digital circuit connection necessary to send and receive digital voice and data transmissions. The U interface is a full-duplex link that works over a single pair (2-wire) cable. It interfaces a line terminating switch in the telephone switching office with a small interface device called a Network Termination device (NT1 or NT2) at the customer premises. In the U.S., the NT1 converts the 2-wire U interface into a 4-wire S/T interface which, in turn, can support multiple devices in a single bus loop configuration, such as a telephone, computer, or facsimile machine. Alternately, in parts of Europe, the NT2 interfaces with an S interface. See ISDN interfaces for a diagram. U reference point A demarcation point in ISDN services installed in North America, where the local loop connects with the NT1 device. See U interface. See ISDN interfaces for a diagram. U Series Recommendations A series of ITU-T recommendations providing guidelines for telegraph switching. These guidelines are available as publications from the ITU-T for purchase on the Net. Since ITU-T specifications and recommendations are widely followed by vendors in the telecommunications industry, those wanting to maximize interoperability with other systems need to be aware of the information disseminated by the ITU-T. A full list of general categories is in Appendix C and specific series topics are listed under individual entries in this dictionary, e.g., T Series Recommendations. See U Series Recommendations. U-C user-central. In ADSL, the standardized interface between the twisted-pair local loop to the subscriber premises and the plain old telephone service (POTS) splitter on the network (usually the central office) side of the link. U-C2 is a less-standard interface between the POTS splitter and the ATU-C (network ADSL Transmission Unit). While functionally similar, the U-C is distinguished from the U-R interface due to the asymmetry of the link. See U-R. U-DSL The U interface in a Digital Subscriber Loop (DSL) system.

U

ITU-T U Series Recommendations Recom.

Description

U.1 (03/93)

Signaling conditions to be applied in the international telex service Standardization of dials and dial pulse generators for the international telex service Arrangements in switching equipment to minimize the effects of false calling signals Exchange of information regarding signals destined to be used over international circuits concerned with switched teleprinter networks Requirements to be met by regenerative repeaters in international connections Prevention of fraudulent transit traffic in the fully automatic international telex service Numbering schemes for automatic switching networks

U.2 (11/88)

U.3 (11/88)

U.4 (11/88)

U.5 (11/88)

U.6 (11/88)

U.7 (03/93)

U-law A pulse code modulation (PCM) coding and companding data ITU-T standard used in audio systems on computer multimedia peripheral cards. This takes some of the load of specialized applications off the central processing unit (CPU). It is often implemented in addition to A-law companding and is suitable for compression of voice communications. Note, this is technically µ-law, but many keyboards don’t support the Mu (µ) character and so it is alternately written as Mu-law or U-law. In fact, it’s even sometimes written M-law since the Greek symbol for uppercase µ is M. See A-law, Mu-law. U-plane In ATM networking, as it applies to Broadband-ISDN reference model, the U-plane is the user plane, a higher-level plane including all of the ATM

U

Sampling of UL Standards Related to Telecommunications UL No.

Descriptions of UL Numbers from Underwriters Laboratory

UL 1409

Low-Voltage Video Products Without Cathode-Ray-Tube Displays: Antenna signal amplifiers, CATV adapters and digital converters, channel balancers and processors, distribution amplifiers, commercial TV cameras, disc players, electronic viewfinders, internal distribution amplifiers, laser disc players, modulators, picture tube degaussers, power packs, power supply-battery chargers, satellite receivers, satellite receiver dish controllers, single-channel converters, teletext and television decoders, television descramblers, tuner adapters and power supplies, UHF amplifiers, tuners, and converters, VHF amplifiers and tuners, video printers, video-production, -processing, -receiving, and -recording equipment, and video tape recorders.

UL 1418

Cathode-Ray Tubes: Bonded frame, laminated, prestressed picture tubes (CRT), rebuilt picture tubes, picture tubes for business equipment, dental, and medical equipment.

UL 1410

Television Receivers and High-Voltage Video Products: Household and commercial television receivers and monitors, and health care facility television equipment.

UL 1412

Fusing Resistors and Temperature-Limited Resistors for Radio- and Television-Type Appliances: For use in appliances that do not involve potentials greater than 2500V peak.

UL 1414

Across-the-Line, Antenna-Coupling, and Line-by-Pass Capacitors for Radio- and Television-Type Appliances: For nominal 125- and 250-V, 50- to 60-Hz circuits, includes double protection capacitors rated 1.0 B5F maximum.

UL 1419

Professional Video and Audio Equipment: Video tape recorders, audio/video editing equipment, audio/video receiving and processing equipment, signal transmission equipment, television cameras, video digitizers, video monitors, metering equipment, and similar equipment.

UL 1492

Audio-Video Products and Accessories: Audio and video products intended for use on supply circuits. Audio products and accessories intended for household use and involved with the reproduction or processing of audio signals. Video products that are intended for household or commercial use, that receive signals in ways such as off the air, through a CATV/MATV cable system, from a video-recorded medium, and from image-producing units. Auxiliary products and accessories intended for use with audio or video products wherein the auxiliary and accessory products are separate and do not perform the desired function, but are used in addition to or as a supplement to products mentioned above. Cellular telephones and similar transceiving devices used on a vehicle, boat, or the like, where the telephone interconnects to the telephone network through a radio transmitter and receiver. Portable audio or video products of the types described above that are intended for use with a vehicular, marine, or any other battery circuit as the power supply means.

UL 6500

Audio/Video and Musical Instrument Apparatus for Household, Commercial, and Similar General Use: This standard applies to the following apparatus that is to be connected to the supply mains, either directly or indirectly, intended for domestic and commercial and similar general indoor use and not subject to dripping or splashing: radio receiving apparatus for sound or vision; amplifiers; independent load transducers and source transducers; motor-driven apparatus which comprise one or more of the above-mentioned apparatus or can be used only in combination with one or more of them, such as radio-gramophones and tape recorders; other apparatus obviously provided to be used in combination with the above-mentioned apparatus,

Sampling of UL Standards Related to Telecommunications, cont. UL No.

Descriptions of UL Numbers from Underwriters Laboratory

such as antenna amplifiers, supply apparatus and cable-connected remote control devices; battery eliminators; electronic musical instruments; electronic accessories such as rhythm generators, self-contained tone generators, music tuners and the like for use with electronic or nonelectronic musical instruments; video apparatus intended for entertainment purposes in health-care facility locations; cellular telephones and similar transceiving devices used on a vehicle, boat, or similar location where the telephone interconnects to the telephone network through a radio transmitter and receiver; portable audio or video apparatus intended for use with a vehicle, marine, or any other battery circuit as the power supply means. UL 1685

Vertical-Tray Fire-Propagation and Smoke-Release Test for Electrical and OpticalFiber Cables: Limits for each fire test to make the tests equally acceptable for the purpose of quantifying the smoke. The cable manufacturer is to specify, for testing each “-LS” (limited-smoke) cable construction, either the UL vertical-tray flame exposure or the FT4/IEEE 1202 type of flame exposure. The same test need not be specified for all constructions.

UL 1577

Optical Isolators: Optically isolated switches and insulation systems, photocouplers.

UL 1651

Optical Fiber Cable: Single and multiple optical-fiber cables for control, signaling, and communications as described in Article 770 and other applicable parts of the National Electrical Code.

UL 1690

Data-Processing Cable: Electrical cables consisting of one or more current-carrying copper, aluminum, or copper-clad aluminum conductors with or without either or both (1) grounding conductor(s) and (2) one or more optical-fiber members, all under an overall jacket. These electrical and composite electrical/optical-fiber cables are intended for use under the raised floor of a computer room (optical and electrical functions associated in the case of a hybrid cable) in accordance with Article 645 and other applicable parts of the National Electrical Code.

UL 2024

Optical Fiber Cable Raceway: Covers the following types of optical fiber cable raceways and fittings designed for use with optical fiber cables in accordance with Article 770 of the National Electrical Code: Plenum. Evaluated for installation in ducts, plenums, or other spaces used for environmental air in accordance with the National Electrical Code as well as general purpose applications; Riser. Evaluated for installation in risers in accordance with the National Electrical Code as well as general purpose applications; General Use. Evaluated for general purpose applications only.

UL 1459

Telephone Equipment: Cordless telephones, key systems private branch exchange equipment, telephone answering devices, dialers, and telephone sets.

UL 1863

Communication Circuit Accessories: Telecommunications equipment such as jack and plug assemblies, quick connect assemblies, telephone wall plates, cross connect enclosures, network interfaces, and connector boxes.

UL 1950

Practical Application Guidelines On-Line Service (PAGOS): A reference service providing information for understanding and applying the requirements of UL Standards for Safety. Of interest is the UL 1950 Standard for Safety of Information Technology Equipment, Including Electrical Business Equipment.

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layers, which bears user application information. It sits adjacent to the C-plane (control plane) and shares physical and ATM layers with the C-plane. The Mplane (management plane) enables the transfer of information between the C- and U-planes. In ATM networking as it applies to Frame Relay bearer services, the U-plane parameters, such as throughput, maximum frame size, etc., are negotiated through the C-plane. Synchronization and coordination between the U-plane and C-plane are described in ITU-T Recommendation Q.923. See the Appendix for more detailed information on ATM. U-Plane A concept for an Undersea Plane, a deepdiving submarine that handled buoyance by “flying” through the water, that was developed by Karl Heinz Lipshutz in the late 1920s. The idea received little notice until the early 1990s. U-R user-remote. In ADSL, the standardized interface between the twisted-pair local loop to the subscriber premises and the plain old telephone service (POTS) splitter on the premises. U-R2 is a less standardized interface between the POTS splitter and the ATU-R (premises ADSL Transmission Unit). While functionally similar, the U-R interface is distinguished from the U-C interface due to the asymmetry of the link. See U-C. U.K. Education & Research Networking Association UKERNA. The trading name for the JNT Association, which has managed the development and operation of the Joint Academic Network (JANET), since 1994, under agreement with the Joint Information Systems Committee (JISC) of the U.K. Higher and Further Education Funding Councils. Thus, UKERNA has responsibility for the education and

research communities’ networking programs in the U.K. It further researches and develops advanced electronic communications facilities. See JANET. UA See User Agent. UAC User Agent client. See User Agent. UART See universal asynchronous receiver-transmitter. UAS User Agent server. See User Agent. UASs unavailable seconds. A measure of duration, in seconds, during which a service or entity is not available. UAT See user acceptance testing, user application testing. UAV unpiloted/unstaffed aerial vehicle. UAWG See Universal ADSL Working Group. UBR See unspecified bit rate. UCA See Utility Communications Architecture. UCC See Uniform Commercial Code. UCF See UNIX Computing Forum. UCITA See Uniform Computer Information Transactions Act. UCM 1. universal controller module. 2. See Universal Call Model. Uda, Shintaro A designer of the Yagi-Uda antenna, a sensitive, directional antenna which worked in the higher frequency ranges and became the model for thousands of antennas that came later and are still in use. See Yagi-Uda antenna. UDI unrestricted digital information. UDLC See Universal Digital Loop Carrier. UDP See User Datagram Protocol. UECT See Universal Encoding Conversion Technology.

UL Conformity Assessment Services Related to Telecommunications Service

Brief description

Listing Service

A UL Listing Mark indicates that representative samples have been tested and evaluated according to nationally recognized safety standards.

Classification Service

A UL Classification mark indicates that products have been evaluated for certain properties under specified conditions.

Component Recognition

A service for factory-installed components in complete products.

Certificate Service

A service for completely installed systems.

Field Engineering Service

A service for installed products without UL Listing Marks or UL Classification Marks.

Testing Environ. Products

Evaluation of innovative environmentally friendly products.

LAN Cable Performance

Safety evaluations and evaluation of LAN cable according to industry performance specifications, including TIA/EIA standards.

Energy Efficiency

Electrical appliances are certified according to U.S. or Canadian standards for energy efficiency through the UL Energy Verification.

SDS Verification Testing

Verification of input/output products to Honeywell’s Smart Distributed System (SDS) for compatibility of components to an industrial control communications network.

UFO 1. See UHF Follow-On. 2. unidentified flying object. UHF See ultra high frequency. UHF Follow-On, Ultra-High Frequency FollowOn UFO. A U.S. Naval, Air Force, and Command communications satellite constellation intended to supersede the aging FLTSAT and LEASAT satellite systems. The system is designed to provide interim Global Broadcast Service (GBS), EHF, and Ka-band transmissions. UFO provides more modern capabilities and more secure communications than the older satellite communications systems. Increased channel capacity is available with Demand Assigned Multiple Access (DAMA) technology. UFO is intended to provide global coverage of four significant geographic areas, including the U.S. and three major oceans. See FLTSAT. UHTTP See Unidirectional Hypertext Transfer Protocol. UI 1. Unix International. A consortium of computer software and hardware vendors promoting the development and implementation of Unix, and of related and other open software standards. See Unix, UNIX. 2. See user interface. uk.telecom An online USENET newsgroup established in August 1991 to discuss topics related to telecommunications in the U.K.. Topics include services, prices, technical specifications, equipment functioning and options, ISDN, and the various telephone carriers providing services. UKERNA See U.K. Education & Research Networking Association. UL See Underwriters Laboratories Inc. ULP See upper layer protocol. Ultra Sniffer A kit-based, handheld radio communications receiver designed to facilitate radio direction finding, especially for “fox hunts,” during which hobbyists get together to try to find a hidden transmitter. This unit, from VK3TJN/VK3XAJ, is a little larger than a deck of cards. It is attached to a 2-m center beam with three elements attached in the center at 90° from the center beam. The unit is designed to overcome some of the limitations of other radio direction finders in terms of overcoming interference and selective tuning without increasing complexity (and knobs). See fox, sniffer. ultraviolet Electromagnetic radiation with shorter wavelengths, between the violet part of the visible spectrum and X-rays. Although it cannot be seen by humans, ultraviolet radiation is of commercial significance because it can degrade many types of materials and pigments. Commercially, it is used in a variety of lamps, such as arc lamps, and can be used to remove data from erasable/programmable computer chips. In astronomy, ultraviolet sensing devices use ultraviolet radiation focused through a spectrograph to study the characteristics of celestial objects. Telescopes and some satellites are equipped with this capability. The Hubble Space Telescope and the International Ultraviolet Explorer satellite enable study of objects using ultraviolet light near the visible

spectrum. The Johns Hopkins Ultraviolet Telescope extends the range to the far ultraviolet, that is, the region further from the visible spectrum. See infrared. ultra-high frequency UHF. A designation for a range within the radio frequency spectrum commonly used for broadcast communications, which ranges from 300 to 3000 MHz. ultra-high frequency (UHF) antenna A category of antennas which are designed to take advantage of the particular characteristics of ultra high frequency (UHF) waves. Because of the wavelength differences between UHF and very high frequency (VHF) waves and the relationship of the rods on the antenna to the length of the wave, it is possible to make UHF antennas relatively small, with more branching elements compared to VHF antennas. However, as UHF television broadcast signals are generally weaker than those from VHF, there is a greater potential for loss, and they must be designed and installed with greater care to be effective. See antenna, combination antennas, VHF antennas. UMA See upper memory area. umbrella antenna An antenna that resembles an umbrella in that the lines extend out and down from a central pole. UML See Unified Modeling Language. UMP1X The USOC code for telephony-related maintenance plan, tier 1, per line. UMSP See Unified Memory Space Protocol. UMTS See Universal Mobile Telecommunications Systems. unattended call A situation that occurs when, for example, an automatic dialing system dials a line, then tries to pass the call to the first available human agent, but no agent is available. Consequently, the call is abandoned. This type of calling occurs in the telemarketing industry and the call is terminated in order not to irritate a potential customer. Unattended calls are also used by collection agencies and the system hangs up if no agent is available or if the call is answered by an answering machine, thus not impinging on the agent’s time. unattended systems Devices or systems which function without a human operator or without significant human attention except for installation and routine maintenance and upgrades. Unattended systems have become prevalent since the late 1970s, when computer automation became inexpensive enough to incorporate into a wide variety of components and machines. Computer bulletin board systems were some of the first information-rich systems to function 24 hours a day, and phone systems now are frequently automated with menu selections and voice mail options. Recently, faxback systems allow users to request product information or technical support in the form of fax documents. The system logs the phone call, gets the customer’s document selections from a list of options, then dials back the user’s fax machine and transmits the requested documents. Unattended systems generally function 24 hours per day at a significant cost savings over human operators. Many businesses are willing to give up personalized

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service in favor of the economy offered by automated systems. See Auto Attendant. unbalanced line A transmission line with two conductors (such as coax or a telephone circuit) with unequal voltages with respect to the ground. In phone circuits, this is generally an undesirable condition. unblanking The portion of the sweep in a cathoderay tube (CRT) where the beam is turned on, with pulses from the generator. See blanking. unbundled Products or services which are sold separately. For example, a company may release a graphics card/monitor combination as a package deal, and later unbundle the items, that is, allow them to be sold separately in order to clear the products, get a higher return, or respond to market demand for one product over the other. Contrast with bundled. Unbundled Network Elements UNE. Telephone network services that are sold or leased through competitive local exchange carriers (CLECs) as unbundled services from an incumbent local exchange carrier (ILEC). These physical and functional services, when broken down (unbundled) into discrete components, make it possible for them to be mixed and matched into a variety of new services that may be optionally resold or leased to endusers by a variety of providers. UNEs came about as a result of the competition-supporting provisions of the Telecommunications Act of 1996. UNEs include such aspects as local loops, switches, information (databased) services, etc. The UNE model and Congressional decisions regarding UNE were controversial. In 1997, AT&T responded to a Circuit Court decision that defeated key provisions of the Federal Communications Commission’s (FCC’s) rules on UNEs. AT&T’s

position was that the rulings could open the door to competitive restructuring of existing services and monopolization of new services by competing providers, but at a higher cost, which would not result in the desired competitive benefits to users. Unbundled Network Elements – Platform In telephony parlance, UNE-Platform (UNE-P) services are combinations of Unbundled Network Elements (UNEs) that provide finished (end-to-end) services to Competitive Local Exchange Carriers (CLECs) that are functionally equivalent to retail service offerings. UNE-P products are intended only for resale to endusers, not for the use of carriers themselves. Examples of UNE-P services include plain old telephone service (POTS), public access line (PAL), ISDN Pri and Bri, digital switched service (DSS), and Centrex services. UNC See Universal Naming Convention. Underwriters Laboratories, Inc. UL. UL is a notfor-profit organization established in 1894, which provides conformity, safety, and quality assessment services and publications to a variety of organizations, including manufacturers. In addition, UL provides educational materials, input to international safety systems, and assistance to various regional authorities. UL publishes a catalog of its standards and the standards themselves in print, on microfilm, CD-ROM, and diskettes. The UL also sponsors a UL Standards Electronic BBS (accessed directly, or through the Web). The majority of the UL published standards have been approved as American National Standards by the American National Standards Institute (ANSI). UL has a number of publications of interest to professionals in the communications industry,

UL Listing Marks Related to Telecommunications Listing Mark

Brief description

UL Listing Mark

Commonly seen, and indicates that samples of the product conform to UL safety requirements according to UL published standards for safety.

C-UL Listing Mark

Canadian market products evaluated according to Canadian safety requirements.

Classification Mark

Products evaluated for specific properties under specified conditions. These usually consist of industrial and building materials and equipment.

C-UL Classification Mark

Classification Mark products intended for the Canadian market.

Recognized Component Mark

Specific to components used in products sold as complete units, and thus not usually seen from the outside. There is also a Canadian version.

International emc-Mark

Products which conform to electromagnetic compatibility requirements of Europe and/or U.S. and/or Japan and/or Australia.

Field Evaluated Product Mark

A product which is evaluated in the field rather than in a laboratory.

Facility Registration Mark

A facility which has passed UL quality assurance standards, specifically ISO 9000-series and ISO 14001 (environmental).

including WireTalk for the wire and cable industry. http://www.ul.com/about/wtalk/index.html UL provides ISO 9000 standards quality registration through its accredited RvA, Registrar Accreditation Board (RAB) and other international quality affiliations. It provides information on new international environmental management standards through ISO 14001. http://www.ul.com/ The full UL catalog is available on the Web, but the UL Standards chart shows some telecommunications-related UL Standards which may be of interest and which provide an idea of the types of use and safety issues concerned. Underwriters Laboratory Inc. assessment The UL provides a number of conformity assessment services for product certification. These include listing, classification, field engineering, and various types of safety and performance testing. The UL Conformity Assessment services chart shows some of the services relevant to telecommunications. Underwriters Laboratory Inc. Mark UL Mark. UL provides a number of listing marks to indicate that products or systems have been evaluated by UL and conform to certain specifications. Those shown in the UL Listing Marks chart are relevant to telecommunications. UNE See Unbundled Network Elements. unerase A system command or feature of a software application that permits the user to restore files that have been erased from a hard drive or similar hard storage device. Note, if other disk write activities have taken place, it may not be possible to unerase the files. Subsequent writes may overwrite portions of the data or the file pointers indicating where the data are stored. In most cases, if you accidentally delete a file, you must unerase it before doing anything else. UNI User Network Interface, User-to-Network Interface. As specified by the ATM Forum, an ATM network switch which interfaces user equipment to private or public ATM network equipment, or connects between Customer Premises Equipment (CPE) and public network equipment. See PMP, PCR, OCD, SCR. unicast A type of Internet Protocol (IP) address identifier for a set of interfaces. Unicast transmits a single Protocol Data Unit (PDU) to a single destination (unlike multicast, where it may go to multiple destinations). The format of the ATM subinterface unicast command is: atm smds-address . See anycast, IPv6 addressing, multicast. Unicode A character-encoding standard designed to support text-encoding in data files. Unicode, Inc. was originally a collaboration between Apple and Xerox, who produced the original specification. They were later joined by Adobe, Aldus, Borland, IBM, Microsoft, NeXT, Novell, Sun, and others. Unicode has been rolled in with an ISO specification to become a subset of ISO 10646. Unicode is loosely based upon the widely supported ASCII standard, but in a greatly extended form to support major world languages, such as those not represented with Roman characters,

including Cyrillic, Greek, Arabic, Hebrew, Japanese Kana, Chinese bopomofo, Korean hangul, and others. Symbols, punctuation marks, mathematical symbols, and technical symbols are also supported. Unicode uses a 16-bit character set, supporting over 65,000 characters. Each character is assigned a unique 16-bit value. No special modes or control or escape sequences are needed. Unicode comprises the first 65,536 code points of the ISO 10646 standard; the rest are reserved for future use. See Unicode Consortium. Unicode Consortium A nonprofit association founded in 1991 to promote and support the acceptance and implementation of the Unicode characterencoding standard. The Consortium publishes a pamphlet on the Unicode specification. The Unicode Technical Committee, descended from Unicode, Inc., now functions as part of the Consortium to actively maintain the standard. See Unicode. unidirectional Moving, responding, or transmitting in one direction, or in only one direction at a time. Unidirectional Hypertext Transfer Protocol UHTP. A robust, unidirectional IP multicasting resource transfer protocol suitable for one-way broadcasting over the Internet or over the television vertical blanking interval. The protocol allows many viewers to simultaneously access the broadcast site. See broadcast data trigger. unified memory architecture A system on which the video display drivers are integrated into the motherboard, and system random access memory (RAM) is used to buffer graphics displays, rather than having them as separate systems. Some systems use this very effectively, providing graphics coprocessor chips, and allowing greater video graphics memory and more control over memory for programmers, applications, and users. On other systems, this type of integration slows down the graphics rendering and overloads the CPU. This is not the fault of the concept, but rather a result of how it is implemented. Unified Memory Space Protocol UMSP. A connection-oriented network protocol corresponding to the session and presentation layers of the Open Systems Interconnect (OSI) model. UMSP was submitted as an Experimental RFC by A. Bogdanov in December 2000. UMSP uses transport layer service for reliable delivery (with acknowledgment data). UMSP creates a network environment for organizing 128-bit address space distributed among Internet nodes. The protocol defines connections management algorithms and network primitive formats; it does not control local node memory. Connection parameters may be set in a number of ways and systems with high protection levels may be configured without restricting application functionality. See RFC 3018. unified messaging See integrated messaging. Unified Modeling Language UML. A widely used modeling language for specifying, constructing, visualizing, and documenting the artifacts of software systems. UML is intended to streamline and simplify

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the process of software design. It is a product of the Object Management Group. See Object Constraint Library, Object Management Group. Unified User Interface UUI. In the Envisat satellite data communications services, the UUI is a single interface to User Service Facilities that enables users to access Envisat data services from any station or access node using a standard Web browser. The UUI interprets the browser commands to the service functions in the Envisat-1 Payload Data Segment (PDS). Uniform Commercial Code UCC. An adopted code for conveying, clarifying, and permitting commercial activities within the provisions of the UCC Act as they apply to commerce within the 50 U.S. states and some of its territories. The Act sets forth the terms and conditions for commercial policies and activities described within the Act, concepts applicable to law, including actions, contracts, and remedies related to commercial endeavors and disputes. The UCC does not strictly dictate the terms of contracts and agreements between parties, but it helps to provide guidelines and default terms that provide a measure of consistency and security for those conducting commercial transactions. The Permanent Editorial Board for the Uniform Commercial Code provides oversight and permission for the distribution of UCC information. The Board publishes reports and drafts related to UCC. See Uniform Computer Information Transactions Act. Uniform Computer Information Transactions Act UCITA. This was formerly an Article of the Uniform Commercial Code. However, with the growth and prevalence of concerns specific to computing, it was felt that there was a need for a separate, related Act. This became especially true when a large amount of electronic commerce began to flow across the Internet. UCITA is a uniform commercial code for software licensing and other computer information-related transactions adopted by the National Conference of Commissioners on Uniform State Laws in

July 1999. See Uniform Commercial Code. http://www.ucitaonline.com/ uniform line A line which has essentially identical electrical characteristics throughout the transmission path. Uniform Resource Agent URA. An architecture for an agent system to provide Internet information access and management. Encapsulation of protocolspecific actions enables the addressing of high-level Internet activities. It is a structured mechanism for abstracting characteristics of desired information and distancing access processes from the client. The URA system was submitted as an experimental RFC by Daigle et al. in October 1996. See RFC 2016. Uniform Resource Characteristic URC. A data format for including meta-information, information outside the resources in question, for the identification and location of these resources on the Internet. See Uniform Resource Identifier. When URCs were proposed, in the mid-1990s, it was suggested that they be used in conjunction with Uniform Resource Names (URNs) instead of URLS, to remove location dependencies. Uniform Resource Identifier URI. A means to identify resources on the Internet. Because of the size and structure of the Internet, these resources may exist in one or more locations concurrently or may at times not be available at all. The syntax and encoding of the names and addresses of objects has been gradually developed since 1990, with URIs used to manage registered protocols or name spaces. A URI uses network protocols to express an address which maps onto an access algorithm. This is important because the Internet functions with many different protocols for the transmission and sharing of data. In most cases, the data can be converted to accommodate diverse formats. However, some types of information are impractical to convert, such as names and addresses of resources. By creating a type of object that can be labeled for recognition and retrieval and a name space in which

Common Uniform Resource Locator (URL) Schemes Scheme

Name

Type

ftp

File Transfer Protocol

Files and directories

http

Hypertext Transfer Protocol

Internet resources, Web pages

gopher

Gopher Protocol

File directories in Gopherspace

mailto

Electronic mail address

Internet electronic mail address

news

USENET news

Newsgroups and individual articles

nntp

USENET news using NNTP access

Alternate means of accessing news

telnet

Reference to interactive sessions

Interactive telnet remote logon sessions

wais

Wide Area Information Servers

WAIS databases, searches, documents

file

Host-specific file names

Accessible files from various hosts

prospero

Prospero Directory Service

Resources on the Prospero service

these objects can reside, access and use of this information can be facilitated. A Uniform Resource Locator is an example of a URI. One of the more interesting developments on the Internet has been the establishment of broadcasting channels over which video and audio radio and television programming can be viewed through Web browsers and various other specialized software programs. This has necessitated the definition and organization of URIs appropriate for digital broadcasts. See Uniform Resource Characteristic, Uniform Resource Locator, Uniform Resource Name, RFC 1630, 1736, 1737, 2396, 2838. Uniform Resource Locator URL. A compact string representation for a resource available on the Internet. URLs have been in use since 1990 as Universal Resource Identifiers in WWW. A URL is a means to locate resources, by providing an abstract identification of its location. Generally, a URL follows this format: <scheme>:<scheme-specific-part>

Examples: http://www.abiogenesis.com/telecomdict ftp://www.peanut.org/

Scheme names consist of a sequence of lowercase characters from a to z, numerals 0 to 9 and the characters “+” (plus), “.” (period), and “-” (hyphen). It is recommended that upper case be treated as lower case in resolving a URL. A number of specific schemes for particular protocols are standardized or commonly used and there is a process for registering new ones. Common schemes (typed in lower case when used in a URL) are shown in the Common Schemes chart. See RFC 1630, 1738, 1808, 2396. Uniform Resource Name URN. Similar in concept to Uniform Resource Locators as a means to identify a resource or unit of information on the Internet, but intended to manage an object space of names expected to have a longer shelf life. URNs provide a globally unique means of identifying information about a resource or access to the resource itself. Functional specifications for URNs were proposed by Sollins and Masinter and presented as a Request for Comments in 1994. See Uniform Resource Characteristics, Uniform Resource Identifier, RFC 1737. Uniform Resource Name Namespace for Object Identifiers URN Namespace for OIDs. On the Internet, an Object Identifier is a tree of nodes, syntactically described as a series of delimited digits. For example, the Internet OID is 1.3.6.1. The OID namespace specifies how an Object Identifier (ASN.1) is encoded as a Uniform Resource Identifier. The ISO/IEC Joint Technical Committee is the declared registrant of the namespace. The scheme was originally submitted by M. Mealling as an Informational RFC, in November 2000, and updated in February 2001. See RFC 3061 which obsoletes RFC 3001.

Uniform Resource Name Namespace for Public Identifiers URN Namespace for PIDs. A namespace designed to enable Public Identifiers to be expressed in Uniform Resource Identifier (URI) syntax. Within XML, a public identifier is a simple string and, historically, public identifiers are not legal URIs in the context of the Web. The URN namespace enables public identifiers to be encoded in URNs in a reliable, comparable way through introduction of a formal public identifier namespace (publicid). The URN namespace scheme was submitted as an Informational RFC by Walsh et al. in August 2001. See RFC 3151. uniformity The capability of a broadcast or other communications medium to deliver a steady and consistent signal within the desired range. uninterruptible power supply UPS. A safety and steady-service device which protects equipment and data by guaranteeing a sufficient and steady source of electrical power in the event that other power sources are interrupted or lost. UPS systems may take their current from an alternating power supply while the system is up, store charges from this source, and then switch to an alternate source, such as a direct current storage battery or separate alternate current generator in the event of power disruptions to the normal supply. UPSs are used on computers, phones, lighting systems, and in emergency centers. Power outages can create severe problems on computer systems, particularly to network servers, queues, backup file systems, and applications which are reading or writing to storage media at the time of a power outage. UPS systems can prevent loss of files in the process of being saved and prevent possible corruption to the medium on which they are being written. unipolar Having only one pole, direction, or polarity. unique user identifier UUI. An administrative function for uniquely recognizing or storing data on behalf of an individual user. This may be a name, number, symbol, token, or biometric equivalent, depending upon the system. A username is a type of UUI commonly used to enable access to restricted computer systems. UUIs are used in association with thousands of different types of secured systems and services. The New Zealand Customs Service, for example, uses a UUI system to register users and to administer their EDI clients using the Customs Computerized Entry Processing System. United States Electric Illuminating Company A month after Thomas Edison’s famous Pearl Street electrical company began providing power for incandescent lighting, this competing company became South Carolina’s first central power station in 1882. United States Geological Survey USGS. The USGS carries out fundamental and applied research in geological surveying, cartographic data collection, storage, search, retrieval, and manipulation. It is responsible for assessing natural ecological events, energy, land, water, and mineral researches. The USGS conducts the National Mapping Program, and publishes

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thousands of reports and maps each year. United States Telephone Association, United States Telecom Association USTA. An organization founded in the 1800s which promotes the well-being of the industry, and provides technical and standards assistance, discussion forums, and publications for its members. USTA represents more than 1200 local exchange carriers (LECs). USTA provides representation before Congress and various regulatory bodies, training courses, technical bulletins, conferences, and media relations. USTA arose from the National Telephone Association, established in 1897. This organizational strength provided a voice for independents in the dominant Bell marketplace. The National Telephone Association later became the United States Independent Telephone Association (USITA). The Kingsbury Commitment, an important step toward cooperation between Bell and the Independents, entered into in 1913, may have averted government takeover of the telephone industry arising from charges of the monopolistic control exerted by Bell at that time. After the mid-1980s divestiture of AT&T, USITA became the United States Telephone Association (USTA) and it is now known as the United States Telecom Association to reflect the broader technology base of local exchange carriers (LECs). http://www.usta.org/ United Telephone Company A historic phone company founded in 1898 by Cleyson L. Brown in Abilene, Kansas, and later expanded to other communities. It operated there until 1966, and then moved to Shawnee Mission, Kansas, where it forms the local division of Sprint Corporation. See Museum of Independent Telephony. UNIVAC Universal Automatic Computer. A historic, large, general-purpose electronic computing system in active use in the 1950s, descended from the ENIAC. It was designed and built in the mid-1940s by the Eckert-Mauchly Electronic Control Corporation, but taken over before its completion by Remington-Rand. UNIVAC was advertised as the UNIVAC File-Computer “electronic brain” by Remington Rand Univac, a Division of Sperry Rand Corporation. UNIVAC was the first significant commercial nonmilitary computing system, available for a little more than $1 million. In general, the UNIVAC consisted of a blackboardsized control console with lots of buttons and switches mounted on a solid old metal office desk with a scopelike display in a separate housing to one side. Banks of spinning tape reels would line the walls facing the main console. A mercury delay line, incorporating a long tube of mercury, was installed inside the computer housing as a memory device. There were a number of input/output modes, including magnetic tape, and various peripherals, such as printers, taking up additional floor space. The clock speed of a UNIVAC wasn’t much different from the personal computers first introduced in the mid-1970s and it took a great deal of care and expertise to get the system up and running and to maintain the

vacuum tube-based hardware. X-1 was the programming language used. In spring, 1951, the U.S. Census Bureau acquired an 8-ton UNIVAC system. In 1952, the UNIVAC was used to (correctly) predict the presidential election returns but the results were not made public until after the election. Due to the media exposure, UNIVAC became so well known that the name became a generic term for large computing devices. There is an original UNIVAC in the Smithsonian museum. See ENIAC. Universal ADSL Working Group UAWG. A commercial consortium formed to promote an easy-todeploy, fast version of Digital Subscriber Line (xDSL) based on ANSI T1.413. Since traditional ADSL installations require a splitter to be wired to the subscribers’ premises and a custom modem installed in their computer, there have been a number of initiatives to simplify the installation process and, hence, the cost, and to allow the subscribers a choice of modem hardware. See G.lite. universal asynchronous receiver-transmitter UART. UART chips and UART circuitry perform a conversion function within a computer. When a computer software program generates data that travels from the computer to the serial card in a peripheral slot, or through a serial device to an external modem, the parallel data generated by the computer are converted by the UART into serial data that are then transmitted through the modem. The same process occurs in reverse at the receiving end. This is not the same process as is performed by a pair of connected modems, which modulate and demodulate a signal, convert it from digital to analog to transmit through the phone line and from analog to digital when received. The UART does its job before the modulation/demodulation process occurs in the modem. A UART chip may be in the computer, or in the modem itself. Universal Call Model UCM. In telecommunications SS7 routing, an extension of the Basic Call Model associated with Intelligent Networks (INs). The UCM provides mediation between the Originating Call Model (OCM) and the Terminating Call Model (TCM). The UCM receives responses from an initial address message (IAM) and its associated calling line ID, whereupon the UCM activates seizure of the originating channel. It then puts out a request for analysis of the A- and B-number and route and, when the information is received, looks up the dialed number in a dialing base for routing. During the call, the UCM maintains routing and bearer circuit status. In systems using PRI ISDN, the UCM is bypassed. Also called line concentration module. See Intelligent Networks Call Model, Virtual Switch Controller. Universal Digital Loop Carrier UDLC. Digital public switched network (PSN) carrier systems comprising a central office (CO) terminal near the switching system, a remote terminal at the customer’s premises, and a digital transmission link connecting the two. Functional criteria for digital loop carrier systems are described in Bellcore TR-NWT-000057.

Digital switching streamlined the system, enabling central office terminals to be integrated into the digital switch. UDLCs were introduced in North America in the early 1970s. Connections to analog interfaces are through twisted-pair copper wires, as are those between the remote terminal and the network interfaces. Universal Encoding Conversion Technology UECT. A Digital Equipment Corporation (DEC) proprietary software system for converting documents to and from Unicode. UECT has been incorporated into the AltaVista search engine, one of the significant search tools on the Web from Digital Equipment Corporation. universal mailbox A centralized computer point of access for a variety of types of messages, including email, digitally encoded voice messages, facsimiles, etc., so the user can look at one listing to determine what to read and when to read it and to simplify the filing and cross-management of document databases. See integrated messaging. Universal Mobile Telecommunications Systems UMTS. In conjunction with general packet radio service (GPRS), UMTS is considered to encompass next-generation wireless telecommunications technologies. UMTS is a broadband, packet-based data transmissions technology base supported in Europe and also potentially in Japan and other Asian countries. It is not directly compatible with emerging American mobile standards. UMTS technologies are characterized by high mobility and flexibility in terms of available data rates and are considered suitable for the basis of a wireless Internet with global roaming capabilities. Since wireless data technologies have lagged somewhat over the years from a lack of support and interoperability, UMTS standards were developed to improve the situation and encourage market support for UMTS deployment. UMTS standards were developed by two groups comprising prominent telecommunications vendors. Trials of UMTS were carried out by Nortel Networks and British Telecom (BT) in 1999. In 2000, ETSI finalized the first series of 3GPP specifications into the UMTS standard. The UMTS first series specifies a wide variety of services, including radio access, functions for applications development, multimedia messaging, and much more. The Release 99 first series enables developers to move ahead with the rollout of 3G services. As a result of standardization, companies such as Nortel Networks have entered into agreements with developers to create 3G wireless dual-mode modems supporting the UMTS standard. Universal Mobile Telecommunications Systems Initiatives UMTS Initiatives. Third-generation mobile telephony research and deployment efforts that are being carried out by a number of companies in a variety of regions, but particularly in Western Europe. UMTS initiatives seek to support and foster the establishment of broadbased UMTS standard-

based wireless communications systems: In May 2000, Lucent announced an initiative to create a Bell Laboratories Research & Development Centre to partner with Italian universities to enable startup businesses and researchers to test ideas and products related to UMTS integration an implementation. In November 2000, the German Bundestag (Parliament) approved UMTS funding for education and research to promote future development of UMTS technologies. In September 2001, Eropolitan Vodafone announced costs for their UMTS initiative in Sweden and a collaboration agreement with the Vodaphone Group. Universal Naming Convention UNC. 1. In general, a convention for logically mapping a name to a process or device such that its explicit file path or routing path is transparent to the user. The UNC can be used to set up a virtual network with various printers, storage devices, scanners, etc. linked in as resources regardless of where they may be located on the network. 2. In terms of file storage, a convention for identifying a shared file on a computer network without explicitly identifying its storage location to the user. This increases ease of access and transparency to users who shouldn’t have to worry about the location of a file on a virtual storage system (which may be a device on another machine a few feet or a few thousand miles away) except as desired. Universal Payment Preamble UPP. An electronic commerce payment mechanism developed by JEPI, based on work by Don Eastlake. The mechanism was described through an RFC document including several examples in August 1996 as to its relationship between the HTTP Payment Extension Protocol (PEP). UPP provides a uniform vocabulary for a uniform syntax and naming options common to payment systems. Common parameters could be specified within PEP-specified header fields and in paymentsystem-specific headers. See JEPI, Payment Extension Protocol. universal payphone A payphone with a wide scope of payment options including coin, calling card, credit card, collect, etc. Universal Serial Bus USB. An open serial data bus standard developed by a consortium of prominent computer products and telecommunications services providers in the mid-1990s. It allows peripherals to be attached to a computer through a single peripheral attached to the motherboard, with other devices chaining or attached in a star topology. Commercial USBs are designed to support many devices, sometimes up to 64 (the host computer is considered a device). A USB will sometimes also provide additional power to devices that might require it. One of the basic goals of USB development was ease of use. It was intended for personal computer users to be able to easily attach and detach external computer peripherals without a lot of technical expertise. Thus, characteristics such as hot swapping and the capability

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to attach multiple devices were desirable design goals. Through a process of enumeration, peripherals are assigned unique addresses for managing runtime data transmissions and transactions. The Human Interface Device (HID) Class is a USB Core-compliant aspect of USB intended for user input devices that require relatively slow data rates (1.5 MBytes/sec) compared to high-speed storage access, audio/visual, or networking transmissions (12 MBytes/sec). HIDs include keyboards, mice, joysticks, graphics tablets, etc. Traditionally the USB HID Class is connected to the computer through a wire, but interest in wireless versions is strong and implementations are being suggested. The format is rapidly gaining popularity and many personal computers now come with USB ports built in. Older computers with PCI slots can be adapted for use with USB through peripheral cards. It is common for a peripheral card to have two USB ports. With the success of USB 1.1, work continued on USB 2.0 to give it even better performance characteristics. It is estimated that higher data rates of more than 400 MBytes/sec may be possible without substantial hardware changes (with the exception of hubs) through the use of microframes. Transmission speeds for a variety of attached devices would be individually negotiated, providing backward compatibility and flexibility in device data rates. Universal Service Order Code USOC. An identification system for tariff services and equipment introduced in the 1970s by AT&T, and later adopted by the Federal Communications Commission (FCC). Since divestiture, the code is even less universal than before, with individual Bell operating companies developing billing systems somewhat independently of one another. Universal Time See Coordinated Universal Time. Universal Transverse Mercator projection UTM. A map projection technique which preserves angular relationships and scale. UTMs are used in many planimetric and topographic maps. A UTM consists of a series of identical projections, each 6° of longitude oriented to a meridian, taken from around the world’s mid-latitudes. Universal Unique Identifier UUID. A unique identifier originating from the Network Computing System (NCS) and the Open Software Foundation (OSF) distributed computing environment. In February 1998, Leach and Salz defined the format of UUIDs guaranteed or extremely likely to be different from all UUIDs generated until the year 3400 A.D., depending upon the mechanism chosen for generating the UUID. In a data communications equipment (DCE) transmissions cell, it is a broadly unique 128-bit identifier assigned to an object. The UUID is typically used in global contexts where it is a challenge to assign a guaranteed unique ID. Thus, a combination of data are combined to produce the UUID, which may include time stamps, random quantities (or seeds for random quantities), and the hardware address of the originating network device, etc.

In the context of Universal Resource Identifier (URI) schemes on the Internet, a UUID enables network resources to be uniquely named without regard to location; they are thus not tied to a physical root namespace. These are also known as Globally Unique Identifiers (GUIDs). UUIDs are useful in that they need not be assigned and administered by a centralized authority (beyond node identifiers), as are domain names. They also have potential as transaction IDs, a property of particular interest to e-commerce transactions. In Unix applications, the Uuid class provides a means for creating and converting Uuid objects to support network UUIDs. Universal Wireless Communications UWC. A wireless communications collaborative program initiated by wireless operators and vendors in 1995. The program is built on the TIA IS-136 Time Division Multiple Access (TDMA) radio frequency standards, along with IS-41 Wireless Intelligent Network (WIN) standards. Universal Wireless Communications Consortium UWCC. A Washington State LLC, established to support carriers and vendors of IS-136 TDMA/IS41 WIN standards. The UWCC sponsors a number of working forums, including the Global TDMA Forum (GTF), the Global WIN Forum (GWF), and the Global Operators Forum (GOF). See Universal Wireless Communications. http://www.uwcc.org/ Unix A widespread, powerful operating system, originally developed in 1969 by Ken Thompson at AT&T Bell Laboratories. The trademarked version of Unix is spelled all in caps as UNIX, whereas Unix spelled in upper and lower case is used generically in the computer industry to refer to the many freely distributable flavors of Unix that have been implemented by different groups. UNIX has gone through a number of hands, from AT&T, to Novell Inc., to the X/Open Company Limited. See UNIX. UNIX UNIX is a powerful, widespread, cross-platform, Internet-friendly, multitasking, multiuser operating system. When spelled in all capitals, UNIX is a registered trademark, licensed exclusively through the X/Open Company Limited. See Single UNIX Specification, Unix. UNIX Computing Forum UCF. A comments and feedback forum through the Santa Cruz Operation, Inc. (SCO), which provides UNIX server operating systems and related products. Unlicensed Personal Communications Services, Unlicensed PCS UPCS. A number of low-range communications systems can be used without broadcast licensing. These are commonly used for applications such as cordless phones, intercoms, monitors, etc. Some are incorporated into short-range wireless local area network (LAN) data and phone systems. Specific frequency ranges have been assigned to UPCS services by the Federal Communications System (FCC). UPCS are permitted within the 1890 to 1930 MHz frequency ranges and are further subdivided for use with asynchronous (1910 to 1920 MHz) and isochronous (1890 to 1910 and 1920 to 1930 MHz) communications. See band allocations.

unlisted phone number A service requiring a fee, in which a phone listing is not published in printed directories or available through directory assistance. Some carriers also provide unpublished service, which is excluded from printed directories, but may be listed with directory assistance, as a partial privacy measure. People pay to prevent their numbers from being listed for a variety of reasons: to avoid crank calls, undesired telephone solicitations, harassment from ex-spouses, etc. Some carriers make it possible for callers to leave a message for an unlisted number, which the caller may or may not return at his or her option. This is useful for emergency calls. See unpublished phone number. unmatched call A call that does not have a corresponding match in a Service User Table (SUT). Call matching is a way of determining whether the call is authorized and should be permitted to ring through. If there is no match to the destination number in any of the relevant lookup tables, such as the Authorization Code Table (ACT) or Calling Card Table, the card will likely be rejected or may be redirected to someone in authority. unpublished phone number A service, usually requiring a fee, in which a phone listing is not published in printed directories, but may or may not (depending upon the carrier) be available through directory assistance. Thus, if listed with directory assistance, it is a midway solution between a listed and an unlisted number. Some people choose unpublished phone numbers to avoid crank calls and undesired telephone solicitations. Some carriers will subscribers to exclude addresses from a published listing, without charging extra. For further privacy, see unlisted phone number. unshielded Unprotected from emitting or receiving electromagnetic interference or broadcast signal interference. Most cables are shielded with plastic and/ or metal foil, but since this increases the weight and cost of the cable, there are still circumstances where low shielded or unshielded cables are used. In video applications, well-shielded cables are recommended. Monitors should be shielded to protect users from radiation exposure, and computers shielded to prevent interference with nearby broadcast devices, such as radios. Improper or insufficient shielding may result in Federal Communications Commission (FCC) rejection in the manufacture of new products. unshielded twisted-pair UTP. A very common type of cable consisting of one or more pairs of twisted copper wires bound together. UTP is frequently used for phone wire installations intended to carry faster data rates. Unsolicited Commercial Electronic Mail Act of 2001. A bill proposed by Rep. Heather Wilson in February 2001 to protect Internet users and providers from unsolicited and unwanted electronic mail. Between 1995 and the present, the volume and frequency of unsolicited electronic mail, also known as “spam,” rose dramatically, resulting in significant load to service providers along with lost productivity and undesired costs to users who had to filter out the messages and sift through them to locate legitimate

mail. Because the cost to the sender of sending email is often insignificant, “junk” email is a far greater problem than junk postal mail. The cost of sending out a million junk postal solicitations is typically more than $30,000, providing an economic deterrent to excessive mailings. In contrast, the cost of sending out a million email messages may only cost pennies to the sender but may result in significant forwarding, storing, and filtering costs to service providers and recipients, especially when junk email file sizes increased due to added images and HTML-format tags. Junk email is now widely used to promote fraudulent money-making schemes, off-shore sheltering of illegal gains, young teen pornography, black market pharmaceuticals, and gray market consumer items. For these reasons, it is felt by many that stronger legislative constraints on unsolicited electronic mail should be put in place to protect recipients and providers from bearing the cost and inconvenience of these solicitations. unspecified bit rate UBR. An unguaranteed ATM networking service type in which the network makes a best-effort attempt to meet the sender’s bandwidth requirements. See available bit rate, cell rate. unsupervised transfer, blind transfer A phone call transfer in which the recipient is not advised as to the identity of the caller. This is common on automated systems in which the caller can select an extension by way of the keypad on a touchtone phone. unused A product which may have been opened, or taken home and returned, but which has not been used. It may have slight abrasions and, if sold, may carry a warranty that differs from a new warranty. UPC Usage Parameter Control. A network mechanism for monitoring and controlling traffic and guaranteeing service for legitimate uses. See traffic policing, traffic shaping. UPCS See Unlicensed Personal Communications Services, Unlicensed PCS. UPGRADE An ACTS project intended to increase the capacity of the existing single fiber European Communications network to higher bit rates over existing hardware to serve the needs of future communications. Capacity will in part be increased with new modulators, switches, and semiconductor laser amplifiers. Various European networks (Deutsche Telekom, 1998 EXPO in Spain, etc.) are involved in testing the systems. Test results and components from the project will be used to update single fiber links to ca. 1300-nm wavelength. See BLISS, BROADBAND, and WOTAN. uplink In broadcast communications, the uplink is the leg from an Earth station to a satellite. From the satellite back to the Earth is a downlink. The distinction is made partly because of the different technologies used in satellite and Earth stations, but also because uplink and downlink services can often be purchased separately. upload, send, transfer To transmit a broadcast or transfer data from the current device to another one, usually at a different location or desk. Computer data are often uploaded from a personal computer to the

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Internet or to a mainframe. Information from a laptop may be uploaded to a desk computer. Telecommunications software, Web browsers, and FTP are common ways in which people upload files. Broadcasts may be uploaded to a satellite link. See upstream. Contrast with download.

The uplink is the transmissions path from the Earth to the satellite, which is often at a different frequency from the downlink in order to reduce interference between incoming and outgoing signals.

UPP See Universal Payment Preamble. upper layer protocol ULP. In hierarchical network models, a protocol that operates at a higher level of the model, which usually consists of application and user transactional functions. In the Open Systems Interconnection (OSI) reference model, ULP more specifically refers to protocols in any of the layers higher than the layer currently being referenced, although colloquially it often means the next higher layer. upper memory area UMA. A section of memory on Intel-based IBM and licensed third-party computers commonly used to buffer video data which can be accessed and read by a video graphics display card. upstream Generally, the transmission going in a direction away from the reference point. Thus, the stream of data from a personal computer to a mainframe would be considered upstream. Sometimes the designation implies from a smaller or less powerful system to a larger or more powerful system, so its use is not completely standardized. In cable networks, the transmission from the transmitting station to the cable television headend is the upstream direction. See upload. Contrast with downstream. uptime An uninterrupted interval during which a system or process has been in active service. The active, functional time between failure or maintenance periods. Contrast with downtime. upwardly compatible A device or program intended to work with later upgrades or revisions. Upwardly compatible may also mean compatible with a larger or more complex version. For example, a handheld device bar code device may be designed to be upwardly compatible with a desktop computer. Upward

compatibility in terms of later versions is much more difficult to achieve than downward compatibility, since future changes or improvements cannot always be anticipated. Contrast with downwardly compatible. URA See Uniform Resource Agent. URI See Uniform Resource Identifier, URL, URN, RFC 1630, RFC 1738, RFC 1808. URL See Uniform Resource Locators. See RFC 1738. URM user request manager. URN Uniform Resource Name. See RFC 1737. U.S. West One of the regional companies created when AT&T was divested in the mid-1980s, comprising Mountain Telephone, Pacific Northwest Bell, Northwestern Bell, and other related firms servicing the “Fourth Corner.” USB See Universal Serial Bus. USDC U.S. Digital Cellular. A telephone standard which uses frequency division multiple access (FDMA) and time division multiple access (TDMA) techniques in the 824 to 894 MHz range. USDLA United States Distance Learning Association. See distance learning. USDN U.S. ISDN services. See ISDN. used A term describing a product that has been opened and used, with no implications as to the quality, age, or remaining useful life of the product. Used equipment is generally represented as being in working condition, as far as is known. See certified, fair, like new, refurbished. USENET Created in late 1979, shortly after the release of a Unix V7 which supported UUCP, USENET is an important communications medium best known for its more than 35,000 public newsgroups. USENET was developed by Tom Truscott and Jim Ellis at Duke University, and Steve Bellovin at the University of North Carolina. The first two-site installation was described in January 1980, at the Usenix conference and, after modifications by Steve Daniel and Tom Truscott, it became known as A News. As soon as it caught on, A News volume began to steadily increase. In 1981 Mark Horton, from UC Berkeley, and Matt Glickman enhanced the software to better handle the increasing volume of information. This 1982 version was known as B News. Two years later, administration of the software was taken over by Rick Adams from the Center for Seismic Studies. Moderated groups capability was added, in addition to compression, a new naming structure, and control messages. A rewrite by Geoff Collyer and Henry Spencer of the University of Toronto was released as C News in 1987. In 1992, Rich Salz released InterNetNews (INN), a program optimized for NNTP hosts, but with support for UUCP. INN was designed for socket-oriented Unix hosts. Enhancements and bug fixes to INN were released by David Barr, beginning in 1995. Maintenance of INN was taken over by the Internet Software Consortium. UUCP gave way to TCP/IP, and TCP/IP’s greater

compatibility across platforms was a means to provide wider access to newsgroups. The Network News Transfer Protocol (NNTP) was also developed and, in 1986, a means to use this for news articles was released. For more information, see the “USENET Software: History and Sources FAQ” on the Internet. See FidoNet, newsgroup, RFC 822/RFC1123, RFC 977, RFC 1036, RFC 1153. user Sometimes called end user. Although often used to indicate a nontechnical consumer of a product or service, a user also generically refers to anyone interacting with that product or service, as opposed to developing or distributing it. user acceptance testing, user application testing UAT. The testing of a product by actual users (those who fit the profile of potential buyers or users) in conditions similar to what the use environment would be in order to ensure acceptance of the product and sufficient design ergonomics and explanation (menus, manuals, etc.) for the operator to be able to use the product without significant intervention or assistance. UAT occurs when the product is considered to be finished and in good working order (bug-free). This is an extremely important aspect of product development, as many entrepreneurs have “surefire” ideas not readily appreciated or desired by users (e.g., potato-flavored ice; yes, someone actually tried it). This can also be referred to as delta testing or enduser testing. See beta testing, gamma testing. user account An account assigned for a specific individual on a computer network or on a multiuser machine. A user account is a security system configured by the system administrator. The sophistication

of the security can range from a simple name prompt at the time of login, to name and password logins at various levels of access, and different protections attached to directories, processes, and programs. User Agent UA. A network service used by clients to find available services on behalf of the user. See Directory Agent, Service Agent, Service Location Protocol. User Datagram Protocol UDP. An IETF-recommended protocol for the Internet which provides a datagram mode for Internet Protocol-based (IPbased) packet-switched network communications. UDP is primarily used with the Internet Name Server and Trivial File Transfer. The format of UDP header is shown in the User Datagram Protocol Header chart. For more details about UDP, see See RFC 768. user event In programming, a type of input event which is signaled through an input device such as a mouse, joystick, keyboard, or touchscreen, and interpreted into a response by the operating system or applications program. User events typically include button, window, or menu selections/adjustments and movement of icons, windows, or objects. The most challenging types of user events tend to occur in fast action video games and realtime graphics input processing. User Glossary Working Group UGWG. A group within the User Services Area of the Internet Engineering Task Force (IETF) which has created an Internet Users’ Glossary. See RFC 1392. user group, user’s group, users’ group An organization of users of a particular product or service. A support group. With the introduction of computers, society took a technological leap that was difficult

User Datagram Protocol (UDP) Header Format 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +----------------+---------------+---------------+--------------+ | Source | Destination | | Port | Port | +----------------+---------------+---------------+--------------+ | | | | Length | Checksum | +----------------+---------------+---------------+--------------+ | | Data octets ... +----------------------------------------/ - - -

Source Port

Optional. Indicates sending port. The default port for replies, zero if not used.

Destination Port

Related to specified Internet destination address.

Length

User datagram length in octets, including the header and data. The minimum is eight.

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for any one individual to understand or bridge. In order to facilitate the use and understanding of complex systems, programming languages, and technologies, many users’ groups sprang to life, beginning in the mid-1950s, to provide mutual support and assistance in sharing information and meeting technological challenges. The proliferation of users’ groups is important not only for the support they provided to members, but also because this venue provided a forum for computer hobbyists, amateur radio groups, and many other amateur and professional enthusiasts to brainstorm ideas and contribute to the developing fields. The development of computer technology was no longer in the hands of large educational institutions and corporations. Individuals and small companies, particularly in the 1970s, had a window of opportunity during which they were able to make highly significant contributions to the development of the industry. user interface UI. The communications link through which a person interacts with a machine. On computers, the UI, in its broadest sense, includes the various symbolic text, images, sound, and other sensory cues and gadgets presented to the user, with which the user interacts. This is commonly done through peripheral devices such as touchscreens, keyboards, mice, joysticks, microphones, data gloves, and others not yet invented. It is considered the highest layer of the computer system structure, with the machine instructions for physical operations comprising the lowest layer. The user interface is the single most important aspect of computing and should never be undervalued. Computers were designed to serve the needs of people; if people are forced to adopt unhealthy or uncomfortable habits to interact with computers, or if computers take time away from people rather than freeing them from repetitive tasks or drudgery, then human needs are not adequately served by the technology. User interfaces and software applications should be designed with the goal that the purpose of the technology is to improve the quality of life. The design of user interfaces is an art. It demands common sense, a knowledge of ergonomics, psychology, philosophy, electronics, aesthetics, and a large dose of sympathy for a broad range of users. As such, user interfaces have developed in fits and starts, with many software programs providing very poor support for users, forcing the user to conform to the idiosyncrasies of the machine (or the programmer who wrote the software), rather than the other way around. See user interface history. user interface history The earliest telecommunications interfaces consisted of physical semaphores (smoke, flags, and arms) and telegraph keys sending coded messages that needed to be decoded and transcribed when received. The received message was usually presented as a long paper tape inscribed with wiggly lines, dots and dashes, or punched holes. Computers up until the 1950s used a similar model. This kind of user interface wasn’t very friendly, so inventors, even in the earliest days of telecommuni-

cations technology, sought ways to encode the alphabet, so that letters could be directly sent and received (eventually resulting in teletypewriters) without the operators doing the translation. But the basic methods prevailed for decades, mainly because they could be used anywhere, with the simplest of equipment. Telegraph key codes are still a requirement of attaining amateur radio licenses. With the development of personal computers, user interfaces took a leap. The Altair microcomputer, sold originally as a hobby kit in 1984, had no monitor, mouse, or keyboard. It was programmed by means of flipping little dip switches; if you made a mistake, you had to start again. Yet within 2 years modern microcomputers, inspired partly by high-end systems with better resources than the Altair, came into being in the form of the TRS-80 and Apple computer, and keyboards and monitors became standard. Almost every change since then has been an evolutionary refinement or logical addition rather than a revolutionary change. Even the lifelike and startling three-dimensional virtual reality world represents, for the most part, an evolutionary development, albeit an exciting one. Early computer user interfaces consisted primarily of monochrome screens displaying limited text, often with no lowercase letters, and large rectangular graphic blocks. While ingenious computing pioneers wrung astonishing surprises from this primitive technology, it was obvious that improvements were needed in order for a computer to be more fun, versatile, and consumer-friendly. User-to-User Indicator UUI. In ATM network Adaptation Layer 2 (AAL2), a 5-bit indicator in a 3octet-header CPS packet that follows the length indicator (LI) and precedes the header error control (HEC). Initially the PPT and UUI were separate fields, but were merged in the mid-1990s into one field, sometimes called the CPS-UUI field. The UUI field enables upper layers (users) to somewhat transparently convey parameters, for example. UserID User Identification. A unique computer account designation used to gain access to a secure or monitored system. A UserID is frequently paired with a password for system access. Historically many systems accepted only eight characters for the UserID and, for backward compatibility, this limitation persists on many systems today. On networks using the most common mail systems, the UserID typically forms the first part of an email address. USGS See United States Geological Survey. USITA Formerly United States Independent Telephone Association. See United States Telephone Association. USKA Union Schweizerischer KurzwellenAmateure Union (Union of Swiss Shortwave Amateurs). A member organization that is associated with the International Amateur Radio Union. http://www.uska.ch/ USOC See Universal Service Order Code. USOP User Service Order Profile. USP1X The USOC code for telephony-related maintenance plan, standard, level 1, per line/circuit, UNI.

USTA See United States Telephone Association. UT1 A time reference based on Earth’s axis rotation. It is related to Coordinated Universal Time in that UTC was set to synchronize with UT1 at 0000 hours on January 1, 1958. UTAM Since some of the frequencies used by incumbent carriers have now been designated for USDC services (1890 to 1930 MHz), companies are changing their operating equipment and software to operate instead in the 2.0 GHz microwave C-band. UTAM Inc. is an open industry resource for assisting in frequency relocation. See band allocations. UTC See Coordinated Universal Time. UTDR Universal Trunk Data Record. Utility Communications Architecture UCA. A comprehensive suite of communications protocols based upon open systems for use by electric utilities providers/maintainers. UCA began at the Electric Power Research Institute (EPRI), in 1988. UCA is a flexible, scalable architecture that can control various types of devices ranging from small local devices to those in major installations and control centers. UCA Version 2 has been developed to support the communication needs of Energy Management Systems, Supervisory Control and Data Acquisition Systems, Intelligent Electronic Devices, Remote Terminal Units, and others. The standardization effort is intended to help utilities providers to intercommunicate through a variety of physical media, to reduce installation, operations, and migration costs, and to achieve secure communications through standard mechanisms. UCA documents are being assessed by an IEEE Standards Coordinating Committee for review as potential IEEE standards. Utility Communications Architecture Forum UCA Forum. A group dedicated to promoting UCA and assisting individuals and companies in understanding, utilizing, and furthering this technology. http://www.ucaforum.org/ utility pole A sturdy tall pole installed in the ground (or on the ground in mountainous areas, supported by rocks and guy wires). The pole is used to support utility wires for power and telecommunications and may have crossbars and insulators. Utility poles are raised with the aid of long poles with spikes on the end called pike poles, or with industrial machines designed for the job. Most poles are made from logs, although some areas have metal poles; at one time in history, it was thought that metal poles would soon replace all the wooden poles, a prediction that didn’t hold true. In some areas, especially avalanche areas, it was necessary to reinstall poles once or twice a year, a costly, time-consuming business, so various alternatives were tried, including laying the wire along the ground. Unfortunately, rodents like to chew through the wires, causing almost as much interruption to service as the avalanches. Transmissions in inclement regions are now often sent with microwave transceiving systems rather than with wires, a solution which requires less maintenance. See joint pole for more details and diagrams.

A typical utility pole with crossarms bearing primary power lines, ceramic insulators, transformers in cylindrical containers, secondary power lines, and local power drops to nearby residences and businesses.

UTM See Universal Transverse Mercator Projection. UTP See unshielded twisted-pair. UTR Universal Tone Receiver. UTS Universal Telephone Service. UUCP UNIX-to-UNIX Copy. UUCP was a basic networking system developed in the mid-1970s by AT&T Bell Laboratories; it was distributed with UNIX in 1977. UUCP was quickly adopted by many educational and research institutions for disseminating mail. Two years later USENET, the global public news forum, was established using UUCP. As UUCP spread and became an important medium for computer connectivity, it was ported to many other computer architectures. In 1997, UUCP mail routing was taken over by the UUCP Project. By the mid-1980s national networks in other countries were being set up with UUCP, establishing it as an important catalyst for intercommunications and the development of distributed networks. Due to its increasing importance, formats for the transmission of electronic mail through UUCP were then standardized for mixed computer environments along lines developed by ARPA. In 1987, UUNET was founded to provide commercial UUCP and USENET access. See BITNET, Unix, UNIX, USENET, UUCP Project, UUNET, RFC 822, RFC 920, RFC 976. UUCP Map A logical map describing the interconnections between intercommunicating UUCP-capable systems. A UUCP Map Entry is issued when a host is registered on the UUCP system. The main routing information in UUCP-base networks is related to the UUCP Map and is contained in a pathalias database. Thus, for a message from

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mysite.org to be delivered to yoursite the path might be expressed as mysite.org site1!site2!midsite3!yoursite!%s

Because exclamation marks are traditionally used to separate the nodes, this is commonly called a “bang path” and veterans of the early email days can remember typing bang paths into their email TO: headers. In the early 1980s, the UUCP Map was still small enough to be represented on a single page, with systems such as ucbvax, menlo70, decvax, and chico representing familiar interlinks to those who were using the system at the time. From this point, UUCP grew and spread to the point where static connections/routing maps were no longer practical in the way they were in the early UUCP days. By the 1990s, map updates generally came from domain registrations rather than from manually submitted registrations. By 2001, it was announced that UUCP Maps would likely be replaced with XML for future registrations. There are sites on the Web that enable the UUCP Map to be queried for a specific entry. For example, a search for ucbvax lists the Internet mail routing entry as cs.purdue.edu!ucbvax!%s and the UUNET mail routing entry as decwrl.dec.com!decvax!purdue!ucbvax!%s The UUCP Map can also provide information about site administrators. In Europe, UUCP Map entries are available through the backbone “netdir” service. UUCP Project A project initiated in the early 1980s to enable the exchange of electronic mail among communicating sites using the UUCP store-and-forward transport system. The UUCP Mapping Project endeavored to create a single worldwide database of systems interconnected through UUCP, in addition to the determination of optimum data paths between

systems. In 1997, the UUCP mail routing for UUNET site, created by Eric Ziegast, was turned over to the UUCP Project currently coordinated by Stan Barber. See UUCP. http://www.uucp.org/ UUI 1. See Unified User Interface. 2. See unique user identifier. 3. See User-to-User Indicator. UUID See Universal Unique Identifier. UUNET A Unix-based network provider and backbone (long-haul network). UUNET provides Internet name serving, connectivity, MX forwarding, and news feeds. The formation of UUNET was probably due in part to the Acceptable Use Policy (AUP) focus on research and education enforced by the National Science Foundation’s NSFNET. This stimulated commercial establishment of computer networks. In the 1980s, UUCP over long-distance dialup lines was the primary means by which providers, institutions, and individuals received their messages. However, Internet connectivity has become ubiquitous and the situation has changed. In the 1990s, UUNET is the only remaining significant network that uses UUCP transport for USENET messages. UUNET Canada, Inc. is located in Toronto; UUNET Technologies Inc. is located in Virginia. URN See Uniform Resource Name. UV See ultraviolet. UWB ultra wideband. UWC See Universal Wireless Communications. UWCC See Universal Wireless Communications Consortium. UXTxx The USOC code for telephony-related surcharges for emergency reporting services. The xx designates the region. For example, UXTMN refers to UXT services for Minnesota.

v 1. symb. volt. See volt. V 1. symb. vacuum tube. See Audion, electron tube, vacuum tube. 2. symb. voltmeter. V & H Coordinates, V H Coordinates Vertical & Horizontal grid coordinates. Imaginary coordinate points on a virtual grid used to determine straightline mileage between two specified points, with each exchange’s location represented by a pair of V & H coordinates. This is used for various products and services charged on a distance or mileage basis, as are long distance calls. The V & H system is based upon a ‘flattened Earth’ system from a Donald Elliptical Projection, developed by Jay Donald of AT&T in the mid-1950s. The basic idea is to create a triangular distance calculation over a flattened surface. V & H Tape Vertical and Horizontal Coordinates Tape. A recorded tape provided primarily to assist with billing, it includes NXX types, major and minor V & H coordinates (latitude- and longitude-like regional designations), LATA Codes, and other information related to long distance accounting and service areas. It is made available for purchase through Bellcore. V drive In analog video, a periodic signal related to the vertical component of a frame that is constructed with sequential, repeating line scans. In standard systems, the V drives sends a pulse so that the electron gun returns from the bottom right corner of the video frame to the top left corner (during the vertical blanking interval) in order in position for imaging the next frame (or half-frame in an interlaced system). The relationship between horizontal sync and vertical sync is such that the pulses can be combined on a single wire. Together they comprise a composite video signal. A composite signal can be represented as Csync-red-green-blue and transmitted over four wires. Many computer monitors use a five-wire RGBHV system in which the H and V represent horizontal and vertical sync pulse components. See H drive, negative-going video. V interface In ISDN, a number of reference points have been specified as R, S, T, U, and V interfaces. To establish ISDN services, the telephone company typically has to install a number of devices to create the all-digital circuit connection necessary to send

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and receive digital voice and data transmissions. The V interface is the reference point between the telephone switching office’s exchange terminal switch and the line terminal switch. Thus, one side connects to the public telephone exchange and the other connects through the U interface to the subscriber’s network termination (NTx) device. See ISDN interfaces for a diagram. V Series Recommendations A set of ITU-T recommendations providing guidelines for interconnecting networks and network devices. These are widely implemented in computer modems. The V Series specifications are available as publications from the ITU-T for purchase, and a few may be downloadable from the Net. Some of the related general categories and specific V category recommendations of particular interest are listed here. See also I, Q, and X Series Recommendations. The chart on the following pages includes a number of V Series Recommendations of particular interest. Note that while a larger number often denotes a more recent standard, there are exceptions, and the categories are intermingled resulting in the number schemes series being interleaved. V5 A telephony standard adopted by the European Telecommunications Standard Institute (ETSI) for use in digital local exchanges in Europe, Australia, South America, and the Far East. Exchanges around the world are gradually being upgraded to V5. V-band A frequency band commonly used in radar applications. See the band allocations listing for a chart and details of frequencies. V.Fast A vendor-developed format which was brought out while the ITU-T standards bodies were developing the V.34 protocol. V.Fast is similar to V.34, but not the same, and consequently some V.Fast modems are not compatible with V.34, while others are hybrid and support both. See V Series Recommendations listing under V.34. VAC See vehicle access control. vaccine A whimsical name for a virus protection program that resides on a computer and signals the user if anomalies or known viruses are present, and allows the virus to be disabled or deleted. As quickly as virus detectors and vaccines are written and disseminated, virus creators come up with new ways to

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ITU-T V Series Recommendations General V.21

A 1984 dialup modem standard supporting data rates up to 300 bps. Most modems in the late 1970s and early 1980s were acoustical couplers, with direct connect modems just beginning to catch on in the mid-1980s.

V.22

A 1988 dialup modem standard supporting data rates up to 1200 bps with fallback to 600 bps. It is interesting to note that in the 1980s, many technical people insisted it was impossible to support speeds faster than 1200 bps over standard phone lines, and that this was probably the fastest speed at which modems would ever transmit data.

V.22 bis

A 1988 update to the V.22 standard supporting data rates up to 2400 bps through frequency division techniques, with link negotiation fallback to 1200 bps, and fallback to V.22.

V.23

Dialup modems supporting data rates up to 1200 bps with fallback to 600 bps and a 75bps back channel or reverse channel.

V.26

A 1984 standard for modem supporting data rates up to 2400 bps on four-wire leased telephone lines.

V.26 bis

A 1984 update to V.26 supporting 2400 and 1200 bps over public phone dialup lines.

V.26 ter

A 1988 update to V.26 and V.26 bis that supports both echo cancellation (public phone lines), and point-to-point two-wire leased phone lines.

V.27

A 1988 standard for modem data rates up to 4800 bps with manual equalizer for use with leased telephone lines.

V.27 bis

A 1984 update to V.27 that supports data rates of 4800 and 2400 bps with automatic equalizer for use with leased telephone lines.

V.27 ter

A 1984 update to V.27 and V.27 bis that supports data rates of 4800 and 2400 bps over public phone dialup lines.

V.29

A 1988 standard for modem data rates of 9600 bps for four-wire leased telephone lines.

V.32

A standard for public dialup and two-wire leased line modems with rates up to 9600 bps with fallback to 48,800 bps. This standard was approved in 1984. When modems incorporating V.32 were first introduced in the late 1980s, it was not unusual for a single modem to cost between $600 and $2,000. Modems of this speed can now be found for $10, as they have been superseded by much faster data rates of 33,600 bps. Many of the V.32 modems were dual-standard modems that supported V.32 in addition to various proprietary protocols from individual manufacturers. See V.32 bis.

V.32 bis

A 1991 standard for public dialup and two-wire leased line modems that supports rates up to 14,400 bps with fallback to 12,000, 9600, 7200, and 4800 bps. Like V.32, a number of these modems are dual-standard modems with proprietary protocols included, and they are generally all backward compatible with V.32. Many of them support MNP-2 to MNP-4 error control and MNP-5 data compression, in addition to V.42/V.42 bis error control and data compression.

V.32 ter

An update to V.32 bis designed by AT&T that supports data rates up to 19,200, and fallback to 16,800 and V.32 bis. This format is freely distributable and has become a de facto standard. The corresponding ITU-T approved format for 19,200 is V.34.

General, cont. V.33

A 1988 standard for modem data rates of 14,400 bps for four-wire leased telephone lines.

V.34

A 1996 standard for dialup modems and fax/modems with rates up to 33,600 bps in full duplex, and up to 28,800 bps in half duplex for facsimile transmissions. (These are sometimes also called VFast, or VFC, but those are actually slightly different interim protocols developed by vendors who were anxious, in the mid-1990s, to get products to market while the work on the V.34 standard was being completed. Some modems became V.34/ VFast hybrids.) V.34 modems are designed to adapt to the line by probing the connection and adjusting according to quality and capacity. They interact with the telephone circuit through handshaking. Optional control data can be sent through an auxiliary signaling channel. V.34 modems are not as subject to noise as earlier modems, due to the implementation of multidimensional trellis coding.

V.34 bis

A 1996 standard that supports the higher data rates of 56,000 bps and 31,200 bps.

Digital Modems, Digital/Analog Hybrids, Wideband, & Parallel Transmission Modems V.19

A 1984 standard for modems for parallel data transmission over telephone signaling frequencies.

V.36

A 1988 standard for wideband synchronous transmission modems using 60 to 108 kilohertz group band circuits.

V.37

A 1988 standard for wideband synchronous transmission modems for signaling rates higher than 72,000 bps, using 60 to 108 kilohertz group band circuits.

V.38

A 1996 standard for wideband data circuit-terminating equipment for rates of 48,000, 56,000, and 64,000 bps for use on digital point-to-point leased circuits.

V.70

A 1986 standard for digital simultaneous voice and data (DSVD) modems in which a data transmission and a digitally encoded voice transmission can be sent at the same time over a single dialup phone line. DSVD are typically downward compatible with standard dialup modems based on more recent high-speed technologies (e.g., V.34). This type of technology lends itself well to teleconferencing applications, and a number of vendors have incorporated V.70 to this end.

V.75

A 1996 standard for digital simultaneous voice/data (DSVD) transmission terminal control procedures. See V.70.

V.76

A 1996 standard for multiplexing using V.42 LAPM-based procedures. V.76 multiplexing has been incorporated into V.70 systems, although it is not limited to V.70.

V.80

A standard for the application interface for communications through data terminal equipment (DTE) of a synchronous H.324 bit stream, such as video, for asynchronous transmission over public switched telephone networks. V.80 works in conjunction with a number of other related technologies and standards. H.324 is an ITU-T approved standard that provides the foundation for combining video, voice, and data communications on a single analog phone line using a 28,800 bps data rate connection. This opens the door to a variety of practical, reasonably priced stand-alone and computer-based videoconferencing products that display up to 15 video frames per second. H.263 and G.723 are video and voice compression schemes used in H.324.

V.90

A 1998 standard for digital to/from digital or digital to/from analog connections, supporting download data rates up to 56,000 bps with upload data rates up to 33,600. During development it was known as V.pcm and some vendors call it PCM. This standard reflects the gradual conversion of data communications to digital format. This standard has its own Web site at http://www.v90.com/

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ITU-T V Series Recommendations, cont. Half-Duplex Modem ITU-T-Recommended Transmission Standards V.17

A two-wire scheme for facsimile machines and fax/modems used in conjunction with extended Group 3 facsimile standards for image transfer at rates of 12,000 bps and 14,400 bps.

V.27

A modulation scheme for dialup facsimile machines and fax/modems used in conjunction with Group 3 facsimile standards for image transfer at rates of 2400 bps and 4800 bps.

V.29

A modulation scheme for dialup facsimile machines and fax/modems used in conjunction with Group 3 facsimile standards for image transfer at rates of 7200 bps and 9600 bps.

ISDN- and Digital Communications-Related V.100

A 1984 standard for interconnection between public data networks (PDNs) and public switched telephone networks (PSTN).

V.110

A 1996 standard for ISDN support of data terminal equipment (DTE) with V-series interfaces. Listed also as I series 463.

V.120

A 1996 standard for ISDN support of data terminal equipment (DTE) with V-series interfaces with provision for statistical multiplexing. Listed also as I series 465.

V.130

A 1995 standard for an ISDN terminal adaptor framework.

V.230

A 1988 specification for a general data communication interface layer 1.

Error Control and Data Compression Protocols V.41

A 1972 code-independent error control standard.

V.42

A 1996 error control standard that greatly enhances the functioning of modems over standard phone lines. Phone lines tend to be noisy, slow, and somewhat unreliable for high speed data communications. In the past, if there were errors on the line, modems would react by exhibiting line noise, losing the connection, or aborting the current operation. With new error control capabilities built in, some of these problems are overcome through filtering and selective retransmission. V.42 includes two error control protocols for dialup modems. These are link access procedures for modems (LAP-M) and Microcom Networking Protocol (MNP-4), such that connections with a variety of modems are supported. V.42 uses a filtering process somewhat like the error correction schemes incorporated into a number of file transfer protocols, such as XModem and ZModem.

V.42 bis

A 1990 standard for data circuit terminating equipment (DCE).

Miscellaneous Modem/Transmission/Network-Related Standards and Protocols V.7

A 1988 guide to terms concerning data communications over telephone networks.

V.8

A 1994 guide to procedures for starting sessions of data transmissions and setting up connections parameters over general switched telephone networks.

V.8 bis

A 1996 guide to procedures for the identification and selection of common modes of operation between data circuit-terminating equipment (DCE) and between data terminal equipment (DTE) over general switched telephone networks, and on leased point-to-point telephone-type circuits.

V.18

Interoperability guidelines for communications services for the hearing impaired.

V.24

A 1996 set of definitions for interchange circuits between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) that specifies the characteristics of interfaces, including pinout circuitry. This is similar to the RS-232 specifications.

V.25

A 1996 standard for dialup automatic answering equipment and automatic calling equipment.

V.25 bis

A 1996 command set designed for synchronous communications through serial ports and connections.

V.54

A modem diagnostics standard implemented in high speed modems.

create mischief or outright destruction on people’s computer systems. With the Internet foreshadowing a not-too-distant day when every computer is linked to the net, perhaps 24 hours per day, more opportunities for vandalism exist, and education about virus detection and protection needs to be made known to the computing public. vacuum An enclosed space in which the gases are at pressures below atmospheric pressure. Since many vacuums are actually near-vacuums, categories of vacuums from low to ultrahigh, depending upon the pressure, have been described. The discovery and creation of vacuums have aided scientists in making important discoveries and provide environments in which various phenomena take place, or fail to take place, due to the absence of gases. For example, a filament in a bulb can burn much longer in a vacuum. vacuum column In some magnetic tape drivers, there may be a vacuum mechanism to control the tape loop. This provides a lower air pressure ‘suction’ next to the tape and the drive mechanism. vacuum gauge An instrument for measuring the degree of vacuum in an enclosed space. There are a number of types of vacuum gauges, including manometers, ionization gauges, and thermal conductivity gauges.

Vacuum tubes fulfilled thousands of roles in electronics for over fifty years, before the invention of the transistor and modern semiconductor technologies. Even now they are appropriate for certain high-frequency applications. The most significant step in the evolution of vacuum tubes was the triode, which included a controlling grid to harness electron energy. These excellent historic examples are from the American Radio Museum collection.

vacuum tube A ubiquitous, essential, and versatile electron tube that was common until about the mid1960s, after which it was superseded by various early

electronic transistors, and later more sophisticated semiconductor technologies. The vacuum tube in its basic form consists of an electron-emitting filament (cathode) and a metal plate (anode) to which the electrons are attracted. Various types of control grids might be interposed between the cathode and the anode (or in other locations), with the whole thing sealed in a glass vacuum tube to control the internal environment and to prolong the life of the filament. The first vacuum tubes adapted for radio broadcasting equipment were developed in the early 1900s. While most small vacuum tubes have passed out of use, cathode ray tubes (CRTs) are still widely used in television sets and desktop computer monitors. There are still situations in which vacuum tubes can be a better solution than the solid-state components now commonly used in electronics. For high powerlevel, high-frequency applications, vacuum tubes are sometimes more efficient and still merit consideration. See cathode ray tube, electron tube. vacuum tube amplifier An important development stemming from Lee de Forest’s invention of the Audion, developed by Harry DeForest. The vacuum tube amplifier was incorporated into telephone repeating units, which extended communications distances. VAD See voice activity detection. Vail, Alfred (1807-1859) An American scientist and inventor, and associate of Samuel Morse, from whom Morse adapted a number of ideas related to the building of telegraph systems. Vail was very mechanically apt and continued over the years to make technical improvements to the technology. In 1837 Vail made an agreement with Morse to turn over the rights for his inventions in return for a share of the commercial rights. In 1848, due to the mounting workload, and the lack of sufficient appreciation and compensation, Vail decided to terminate this relationship with Morse. Morse code may be one of Vail’s biggest contributions. When Morse was designing a system for coding messages, he initially created a complex numeral-letter relationship that required a timeconsuming dictionary lookup to decode the words. Vail apparently came up with the simpler system, after altering the mechanics of a telegraph instrument so it moved vertically rather than horizontally, to allow the instrument to leave spaces (thus yielding dots and dashes) when recording a message. See Morse code, telegraph history. Vail, Theodore N. (1845-1920) Theodore Vail was from the same Vail family that had a close association with Samuel Morse at the time of his invention of the telegraph, and Vail learned telegraph code from the elder Morse. Vail became a telegraph operator, and later devoted most of his life to the management and promotion of universal telephone services. Vail became company general manager of the first Bell company in 1878 in Boston. He was the first president of the Telephone Pioneers of America and a cofounder of Junior Achievement Inc. (1919). He was instrumental in continually expanding the

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company’s offices and services, and directed the building of the first transcontinental telephone line, completed in 1914 and officially opened in 1915. After what has been regarded as a brilliant career, where he maintained his commitment to quality and service, Vail resigned in 1887 due to his disgust at the narrowly commercial vision of the Bell financiers. In 1907, he was induced to return to AT&T as president, at a time when Bell was rapidly buying independents. Bell also purchased Western Union stock, and installed Vail as president of what had once been Bell’s chief rival. With the death of J. P. Morgan in 1913, Vail voluntarily took steps to reduce AT&T’s monopolistic buyouts and control of the long distance networks, in order that reorganization could be done from the inside rather than being imposed by regulatory authorities. Vail retired as president in 1919. See Kingsbury agreement. value In imagery, the relation of a color to white or black, or levels of gray. Sometimes called lightness. In color, the intensity of the color. value-added Services offered, usually for a fee, in addition to standard product or subscriber services. Options. VAN value added network. Van Allen radiation belt A region of space surrounding Earth in which there is high-intensity particle radiation which is sufficiently destructive that it is avoided for communications satellite orbits. This region is roughly between the low Earth orbit (LEO), starting at about 1000 kilometers, and medium Earth orbit (MEO). It is named after James A. Van Allen. Van de Graaff generator A device for creating electrostatic effects by charging insulated electrodes to high energy potentials. Van de Graaff generators are popular exhibits in science museums. They typically are configured as melon-sized metallic spheres atop a central pole, and visitors can place their hands on the globe and watch their hair stand on end. It is named after Robert J. Van de Graaff, an American physicist of the early 1900s. van Musschenbroek, Peiter (1692-1761) A Dutch educator and experimenter who created the Leyden jar condenser (named after the region) in 1745, independently of other inventors, including E. G. von Kleist. It was a simple but practical capacitor, and effective enough to harm to a person not careful in its handling. Van Musschenbroek also described a way to carry out experiments with the jar so that a person would not be mortally shocked. Many subsequent experimenters, including Benjamin Franklin, devised variations on the basic Leyden jar. vaporware A derogatory term for software that has been announced prior to completion, or prior to distribution. The negative aspects of the term stem from two sources, truth in advertising and the fact that many announced software products never hit the shelves. Because the software industry is new and confusing to a great portion of the public, unsupported product announcements have not been as strongly condemned and regulated as in other indus-

tries, a situation which may change as the buying public becomes more familiar with the new technologies and tired of unsubstantiated promises. variable bandwidth Bandwidth that can be tailored, usually on an on-demand basis, to the capacity needs of the current transmissions. The ability to adjust capacity allows the system to more efficiently allocate resources and provides a mechanism for setting up accounting systems that bill on an as-used basis. variable bit rate VBR. A data transmission commonly represented by irregular groups of bits or cell payloads, followed by unused bits or payloads. VBR traffic is generated by most media other than voice. In an ATM environment, a VBR service can be realtime or non-realtime, and is guaranteed sufficient bandwidth and quality of service (QoS). See cell rate for a chart. variometer An instrument for measuring magnetic declinations, particularly of the Earth. See declination. Varian, Russell H. (1899-1959) An American inventor, Varian worked in the physics laboratories at Stanford and, in 1948, cofounded Varian Associates with his brother Sigurd and Edward L. Ginzton. He served as the President and a Board member until his death. He was awarded numerous patents related to thermionic tubes, magnetic resonance, and various radar technologies. Varian was a member of several prominent engineering organizations and a Director of the West Coast Electronic Manufacturer’s Association. He was a Sierra Club Committee member and acquired land to further conservation efforts connected with the Sierra Club. He and his wife Dorothy set the groundwork for Castle Rock to become a state park in 1968. Varian had an early introduction to television technology through Philo Farnsworth and became wellknown for the co-development, with Sigurd Varian and William Hansen, of the Klystron tube technology that is used to this day in broadcast TV. This important invention in the late 1930s enabled the generation of ultra-high frequency radio waves (microwaves) and supported the evolution of radar and communications technologies. See Klystron. Varian, Sigurd F. (1901-1961) An American engineer and commercial pilot, Sigurd shared in many collaborative inventions and business ventures with his brother Russell. He helped cofound Varian Associates and invented a number of types of practical devices, including pumps, filters, heaters, and a precision high-speed drill press. His interest in navigation was a good match for his co-invention of the Klystron, an electron tube to generate ultra-high frequency radio waves (microwaves) that could be used to improve navigation through radio direction-finding technologies. See Klystron. Varian Associates, Inc. A pioneering microwave technologies development firm, founded by the Varian brothers (Russell and Sigurd) and Edward Ginzton in 1948 in San Carlos, California. Dorothy Varian, Russell’s wife, was also active in the founding, development, and operations of the company,

and served as the treasurer until 1951. Varian Associates built upon the Klystron tube invented by the Varian brothers and William Hansen and developed further by Ginzton, Marvin Chodorow, and others. Varian Associates and the Sperry Gyroscope Company’s lab contributed to important developments in radar sensing, navigation, and microwave communications technologies over the following decades. Varian was also instrumental in creating some of the components important in chemical spectroscopy and medical imaging. Varian, Inc. was spun off from Varian Associates in 1999 to focus on life sciences and health care products. Varian Associates was the first company to move into the Stanford Industrial Park, in 1953, the heart of the emerging Silicon Valley. There were a number of divisions within the firm, including the Microwave Power Tube Division and the Electron Devices Group, which separated from Varian Associates to become Communications and Power Industries (CPI) of Palo Alto, California. The Microwave Power Tube Division of CPI continues the tradition of developing and improving klystron technology. See Ginzton, Edward; Klystron; Varian, Russell and Sigurd. Varley loop test A type of diagnostic procedure which uses resistance through a bridge to locate a fault in a length of circuit. Variable resistance is connected in series with the resistance of the broken or defective line. It is similar to the Murray loop test, but with a third wire, and more commonly used. See Murray loop test; Wheatstone bridge. Varley, Cromwell Fleetwood A British researcher and technician who investigated ionization, and was involved in early Atlantic telegraph cable installation. He was hired by Western Union to evaluate the telegraph system in the U.S. Varley standardized many of the lines, systems, and diagnostic techniques. The Varley loop test is named after him. See Wheatstone, Charles. VAX Virtual Access Extension. A series of minicomputers from Digital Equipment Corporation (DEC) that was developed in the mid-1970s as the successor to the DEC PDP-x series. The VAX computer system was released in 1977 with 32-bit computer capabilities compared to the 18- or 16-bit systems characteristic of the PDP- line. The VAX 11/780 was popular in educational institutions around the world, often replacing or being added to the still-popular PDP-11 machines. Both dumb and smart remote terminals (ADS, Gigi, Tektronix, Ramtek, and others) could be readily interfaced with the VAX to support one or two hundred users at a time. The VAX 11/750 followed, along with several other models, including the MicroVAX. The early VAX machines were generally running VMS as the operating systems, but Unix also became a popular VAX option over time. See PDP-. VBE VESA BIOS extensions. A high-resolution VESA BIOS standard that can be implemented in hardware or software to provide control of video graphics displays on a computer, typically an Intel-

based International Business Machines (IBM) or third-party licensed computer. vBNS very high speed Backbone Network Service. A research network established in 1995 by the National Science Foundation. VBR See variable bit rate. VBX Visual BASIC Extension. VC virtual connection, virtual circuit. A generic term for a logical communications medium established on request. A connection typically includes a concatenation of channels forming an end-to-end path. A circuit refers to transmission in both directions. Three types of VCs include permanent (PVC), smart/soft permanent (SPVC), and switched (SVC). In an ATM environment, data to be transmitted by a VC is segmented into 53 octet quantities called cells. This consists of 5 octets of header, and 48 octets of data. VCC virtual channel connection. A generic term to describe a logical connection. In an ATM environment, a virtual channel refers to the unidirectional transport of ATM cells associated by a common unique identifier value. Virtual circuits (VCs) can be combined to form a virtual channel. VCI Virtual Channel Identifier. A value in the header of each ATM connection cell which identifies that connection. See VC, VCC, virtual channel. VCL Visual Component Library. A library used for applications development for Borland Delphi products. VCSEL See vertical cavity surface-emitting laser. vector Any quantity having both magnitude and direction. vector display A cathode ray tube (CRT) vector display is one in which the sweep of a beam follows a vector (line or stroke) and illuminates (and refreshes) the specific part of the display that is needed to render the desired colors and shapes. In other words, the beam doesn’t follow the sawtooth scan characteristic of raster displays. This is in contrast to a television screen, in which a beam constantly sweeps the screen to form a frame in which the beam travels across the entire display area on a constant, repetitive basis. In a vector monitor, a vector generator takes the coordinates supplied by the processor and converts them into analog voltages that are used to control the direction of the beam as it excites the phosphors coated on the inside of the CRT. Vector graphics appear very ‘crisp’ and clean, but refreshing large areas or the entire screen is generally slow and impractical for many applications. Vector monitors were prevalent during the 1960s and ’70s, but have largely been replaced by mass market raster monitors. Tempest was an early video game that employed vector graphics, whereas Space Invaders used raster graphics. vector font A set of textual characters or symbols defined by vector algorithms (usually lines, spline curves, and arcs) rather than by relative positioning of dots within a grid (raster or bitmap font). A vector font looks smooth and appealing at almost any size,

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except very tiny sizes, and displays at the highest resolution available to the output device on which it is being displayed or printed. In general, the higher the resolution, the smoother the lines and more attractive the overall look of the font. Contrast with raster font. vector quantization See quantization, vector. vehicle access control VAC. Control of various devices related to transport vehicles. Examples include garage doors, access gates, and other types of barriers that may be encountered and opened with a device in the vehicle, such as a radio-controlled remote control. Newer VACs often include security features and frequency programming for customizing the frequency emitted by the devices (this is handy in storage facilities where many doors are close together). The frequencies available for these types of devices vary, depending upon the country. Vendor’s ISDN Association See ISDN associations. verifying punch A punch card perforator that also verifies the punches to each card to see that the perforations are correct, automatically replacing those that are defective. Veronica Named tongue-in-cheek for a comic-book character reference to a related tool that queries FTP sites named Archie. What Veronica does for Gopher information is similar to what Archie does for FTP sites. Veronica is an Internet keyword query tool that searches Gopher sites, sometimes called Gopherspace, and typically displays the results of the search in the format of a Gopher menu. Users are linked transparently to the source, and may not see the location of the source unless they explicitly ask. Veronica was introduced in 1992 by S. Foster and F. Barrie of the University of Nevada (Reno). Computer programmers love to come up with acronyms, and Veronica is no exception. It’s a stretch, but it has been said that Veronica stands for Very Easy Rodent-Oriented Netwide Index to Computerized Archives. See Archie, Anarchie, Gopher, Jughead, WAIS. Versatile Interface Processor VIP. A Cisco Systems commercial router interface card that provides multilayer switching. versorium A device for detecting electrical properties of various materials, invented by William Gilbert in the late 1500s. The versorium resembles a compass needle in that it is a horizontal movable needle balanced on a small support stem, but differs in that the needle itself is not made of magnetic material, like lodestone, but rather of wood or a nonmagnetic metal. Gilbert used this sensitive device for evaluating attractive properties of different materials when altered by rubbing. Descendants of this instrument are now called electroscopes. See Gilbert, William. vertical-cavity surface-emitting laser VCSEL. (pron. vixel) In general, traditional lasers emit light from the edges of the structure, and the laser cavity runs along the horizontal length of the device. VCSELs differ in several important ways. The light is emitted from the surface rather than from the

edges, the laser cavity is vertical rather than horizontal, and the beam is narrower. Otherwise, the general operating principles are similar to regular lasers. VCSELs were first reported in the mid-1960s, by Melngailis, who coauthored many articles related to optics, especially infrared technologies, between 1965 and 1969 and has coinvented semiconductorbased optical wave guide devices since that time. The commercial implementations of VCSELs are fairly recent, however. It was not until the late 1970s, in Japan, that wavelengths suitable for telecommunications applications began to be generated with VCSEL technology. Room temperature VCSELs began to be developed by the mid-1980s and practical laser devices based upon VCSELs were beginning to emerge in the early 1990s. This is a cross-section of a VCSEL-based surfaceemitting semiconductor laser as designed by N. Ueki of Fuji Xerox Company and submitted Aug. 1998 for a U.S. patent (#6,320,893). The device features a stable transverse mode, reduced threshold current, and higher output than previous semiconductor laser embodiments.

10 11 7

8

{

6

5 4 3 2

} 12

1

The component is fabricated in layers. Layer (1) is the substrate supporting the lower reflective layer (2). The reflective layer bounces light back up into the central quantum well region through an undoped spacer layer (3). Between the lower and upper reflective layers is the quantum well active layer (4) composed of an undoped quantum well layer and a barrier layer. Above this is another spacer layer and the optical confinement layer (6). The thickness from the bottom of the lower spacer layer (3) to the top of the upper spacer layer (5) is an integral multiple of the oscillation wavelength divided by the refractive index. This physical/mathematical relationship fosters a standing wave between the reflective surfaces such that the antinode of maximum light intensity occurs at the quantum well active layer.

In VCSELs, light is emitted from the surface through the sandwiching of reflective mirrors around the laser cavity. Metallic mirrors were not found to be very effective but distributed Bragg reflectors are effective in reflecting a high percentage of the reflected light to be guided back toward the laser cavity. The positioning and quantity of quantum wells can be used to control the optical properties associated with VCSEL devices. One big advantage of surface-emitted laser light is

that the component can be tested before it is stamped out of the fabrication materials, in contrast to edgeemitting lasers that must be stamped out before the emissions can be tested. This represents a significant time/materials/cost savings. They are also more efficient in terms of the amount of light that is emitted in relation to the power drawn from the circuit. In addition to this, the light beam is narrower and rounder than that from regular edge-emitting lasers. This is significant in terms of the suitability of VCSELs for fiber optic networks. If you get more light for the same amount of power and the beam fits into a smaller space, it becomes eminently suitable for use with tiny optical fiber waveguides. Because they are surface-emitting, whole new classes of circuits can be constructed with VCSELs. They can be mounted on printed circuit boards or other suitable substrates, or can be mounted directly on other semiconductor chips (e.g., for optical detection systems), depending upon their function. They can also be organized into arrays.

An example of an optical neural network implemented with a VCSEL array that is spaced apart from a mask that is, in turn, spaced apart from an array of optical detectors with the same configuration of rows/ columns as the laser array. This implementation was proposed by R. Webb of British Telecom, in a June 1998 patent application for a telecommunications switch (U.S. Patent # 6,307,854).

Commercial and experimental VCSELs have been developed for a number of uses. There are now laser diodes in the 780 nanometer infrared range. VCSEL array optical ‘neural’ networks have been proposed. Edge-emitting lasers still have some important advantages, however. Currently, their maximum optical power is higher than that of VCSELs, and the wavelengths emitted are more suitable for optical fiber transmissions. VCSELs currently are suitable for very short distances, but some development needs to occur before they can be used in place of edge-

emitting lasers for longer transmission lines. See laser, quantum cascade laser. Vertical Service Code VSC. In telephony, subscriber-dialed codes that provide access to features and services provided by various carriers as part of value-added telecommunications services. Examples include Call Forwarding, Call Trace, Automatic Callback, and others. These services are invoked by typing in a number or ‘star code’ (a number prefixed by an asterisk). The Industry Numbering Committee has developed guidelines for the assignment of VSCs. Care must be taken, when requesting VSCs for new services, that the number does not conflict with codes established in other regions within the North American Numbering Plan (NANP) purview. Examples of some of the more commonly available VSC assignments are listed in the VSC Assignment Examples chart. The North American Numbering Plan Administration (NANPA) publishes a more complete list. http://www.nanpa.com/ vertigo A perception by an individual that the environment is moving around the individual, or the individual is moving in relation to the environment when no such physical motion actually exists. For example, watching a big-screen movie with realistic action may cause a viewer to feel as though he is moving, when in fact he is sitting still in a theater seat. The brain’s misinterpretation of motion as it relates to body position causes a dizzy-like feeling and may cause or exacerbate motion sickness. It can even make a person feel like he or she is falling. Illness, nervous tension, or migraines can make vertigo more acute. (Vertigo is often confused with the dizziness that occurs when blood supply to the brain is reduced.) Sensitive individuals may experience vertigo after long periods of watching text scroll by on a computer. Since a fairly significant proportion of the population experiences vertigo at one time or another, developers of multimedia products, especially those involving moving platforms, headsets, and other motion-controlling or body-worn devices need to take this into consideration when designing and testing their systems. Games developers have discovered that a certain number of people become ‘seasick’ from playing fast action video games. See burnout, carpal tunnel syndrome. Very High Density Cable Interconnect VHDCI. A type of compact computer peripheral connection cable that enables multiple 68-pin SCSI connectors to be connected to a computer backplate. See P connector. very high frequency VHF. Electromagnetic waves in the approximate range of 50 to 300 MHz, part of which is allocated for amateur use (50 to 54 MHz and 144 to 146 MHz) with some regional variations. very large scale integration VLSI. In the semiconductor industry, VLSIs are integrated circuits (ICs) that combine hundreds of thousands of logic and/or memory elements into one very small chip. This type of circuitry revolutionized the cost and manufacture of computers. VLSI has enabled the manufacture of

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palm-sized computers more powerful than roomsized computers from a few decades ago, which were dependent on vacuum tubes and wires for their circuitry. Very Small Aperture Terminal VSAT. Very small commercial terminals for two-way satellite transmissions in the United States, and one-way communications in countries with restrictions. VSATs are generally organized in a star topology, with the Earth station acting as a central node in the network. This Earth station operates with a large satellite dish and a commercial quality transceiver. In some VSAT implementations, the signal from the transmitting Earth station to the satellite is amplified and redirected to a hub Earth station. Since all transmissions pass through this hub, two hops are needed for intercommunication between satellites. (This results in a bounce pattern known as an M hop.) Some newer configurations, modulation techniques, and amplification systems are included onboard the satellite, so that an interim hop to a hub is not required.

VSAT systems are appropriate for centralized business and institutional networks. Commercial VSATs typically communicate in the C- and Ku-band frequencies. very short reach VSR. Connections spanning a short distance with the implication that it has fairly high bandwidth characteristics or needs. Thus, the term is being widely used in the fiber optics networking industry to describe short distances that require highquality, fast connections without overengineering the components or making the cost prohibitive. Due to the demand for this type of technology, the Optical Internetworking Forum has defined a set of four implementation agreements for very short reach (VSR) intra-office interfaces using the OC-192 format and data rate. Short reaches remove the pressure to transmit data serially; parallel cables are practical for VSR connections. This can be implemented with multiple wavelengths over a single fiber or with multiple fibers (or both). Cisco Systems has been a leading company work-

Vertical Service Code (VSC) Assignment Examples Number Name

Notes

*51

Who Called?

*57

Customer Originated Trace

*60

Selective Call Rejection

*61, *81

Distinctive Ringing/Call Wait. Activate/Deact.

*66, *86

Automatic Callback, Activate/Deactivate

*70

Cancel Call Waiting

*72, *73

Call Forwarding, Activate/Deactivate

*77, *87

Anonymous Call Reject., Activate/Deactivate

Provides the subscriber with the directory number and date/time of unanswered calls. This is similar in function to Caller ID devices that log incoming calls and date-/timestamp them. Provides the recipient of a harassing or threatening call with the ability to request a trace of the last call received. Enables the subscriber to reject incoming calls from a selection of calling parties. Enables the subscriber to have incoming calls from a select list of calling parties identified using a ringing sound that is distinctive and recognizable. Enables a subscriber to automatically have a call placed to the last number dialed when that number becomes available (no longer busy). Enables the subscriber to cancel call waiting. There are several different types of Call Waiting services, including regular, deluxe, and selective Call Waiting. Enables the subscriber to control the redirection of calls to another number/station. This is handy if you are expecting an important call and are planning to be at another location. Enables the subscriber to set up the rejection of calls from callers who are using anonymous dialing (those that don’t show up on Caller ID services).

ing with vendors to create functional, standardized OIF-approved SONET/SDH interfaces optimized for VSR interconnections for routes, switches, and dense wavelength division multiplexing (DWDM). See Very Short Reach Interfaces chart. VESA See Video Electronics Standards Association. VF access voice frequency access. VFast See V.Fast, V Series Recommendations. VFC Version Fast Class. A vendor-developed interim format for modem-based serial communications, which was commercially implemented while the ITU-T was working out the V.Fast standard. See V.Fast, V Series Recommendations. VGA See Video Graphics Array. vgrep visual grep. A variant of a very powerful, useful Unix command. See grep. VHDCI See P connector. VHF See very high frequency. VHF antennas A category of antennas designed to take advantage of the particular characteristics of very high frequency (VHF) waves. Because of the wavelength differences between VHF and ultra high frequency (UHF) waves, and the relationship of the rods on the antenna to the length of the wave, VHF antennas tend to be larger and more varied in their shapes than UHF antennas, and can be installed with less precision and still be relatively effective. They are not as broad, however, as a single UHF antenna can cover the entire UHF band, but a VHF antenna is usually optimized for a particular range or specific stations. See antenna, combination antenna, fan dipole antenna, UHF antenna. VHS Video Home Systems. A widely used video format developed by JVC that is compatible with millions of home user systems. VHS and Beta formats were released at about the same time. Beta was acknowledged as being superior, but was also a bit

more expensive, so VHS won the marketing wars. It is slowly being superseded by S-VHS, 8mm, and Hi-8mm formats, in addition to a number of digital formats, including DVD. S-VHS systems are downwardly compatible with VHS tapes, that is, you can play a VHS tape in an S-VHS system (but not the other way around). VIA See Virtual Interface Architecture. Vibroplex Trade name of a type of semi-automatic telegraph key introduced in the later 1800s, more commonly called a bug key. This particular type of bug key was patented in 1904 by Horace G. Martin. By using a vibrating point for automatically generating dots and dashes, it relieved telegraph operators from physical and mental strain. video capture board See frame grabber.

This common style of rooftop antenna is designed primarily for capturing VHF television broadcast frequencies. The length and orientation of the reflectors and directors, and the general orientation of the entire structure will influence the strength of the signal that is apprehended along the length of the structure and transferred through the feedline (75-ohm coaxial cable) to the television tuner.

Very Short Reach Interfaces Spec.

Gbps

Meters

Notes

VSR-1

1.25

ca. 300

Similar to Gigabit Ethernet multimode fiber (MMF) technology. A full duplex link based upon twelve parallel 850-nm bidirectional VCSEL channels running over two 12-fiber ribbons. One fiber carries CRC error correction, one carries parity information, and the remaining 10 are for data. The lasers and photodetectors can be built in arrays.

ca. 600

Based upon ITU G.691, a serial 1310-nm single-mode fiber interface. Compatible with existing central office (CO) fiber links. Based upon uncooled Fabry-Perot lasers (rather than VCSELs) or those with similar optical characteristics.

VSR-2

VSR-3

2.5

ca. 300

A full duplex bidirectional link based upon twelve 850-nm VCSELs and multimode ribbon fiber technology. Four fibers transmit and four are unused. The lasers and photodetectors can be built in arrays.

VSR-4

10

ca. 85/300

A full duplex serial link over two multimode fibers based upon 850-nm VCSELs.

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video chipset A logic circuit in a computing device that handles the processing, and sometimes acceleration, for video graphics display. Various means of configuring this circuit, and integrating it with the system, control the speed, resolution, and palette set of the display. Video Dial Tone VDT. The name for on-demand consumer video programming services provided through the existing public phone copper wire infrastructure. This includes services such as movies-ondemand, videoconferencing, interactive programming, financial services, and interactive shopping. Until recently, the concept was feasible, but the communications rates through telephone lines were just too slow. With faster data-rate technologies such as DSL, phone lines are now seen as a viable delivery infrastructure for these types of services and may compete with cable services for the growing market. See Open Video Systems. Video Electronics Standards Association VESA. An industry standards body established in 1990 that develops various peripheral standards for Intel-based microcomputers. This organization is responsible for defining Super VGA (SVGA) and the VESA local bus for peripheral device interfaces with personal computers. See super video graphics array, VESA VL. video floppy A 2-in. digital image storage floppy released in the mid-1980s to hold video images of 360 lines of resolution. Various methods are now used to store digitized images, including flash memory, 3.5-in. floppies, and various proprietary cards. Video Graphics Array VGA. A graphics standard common on Intel-based International Business Machines (IBM) and licensed third party computers, supporting 640 x 480 (16 colors) and 320 x 200 (256 colors). It has been superseded by super video graphics array (SVGA). See super video graphics array. video switcher A generic phrase for a wide variety of types of passive routing boxes for video signals. Home systems sometimes have simple switchers to select between a VCR and a laserdisc player. Professional switchers may have banks of connectors, sliders, and settings.

This simple consumer switcher provides switching for composite video and audio inputs and outputs through standard RCA receptacles. It can switch between four different devices.

video tape A magnetic recording medium resembling common audio tape designed to store both

images and sound. The most common formats for video tape are VHS, S-VHS, S-VHSc (compact S-VHS), Beta, 8mm, and Hi-8mm. S-VHS and Hi-8mm are sufficiently good for many professional applications, although higher quality formats are preferred for commercial broadcast quality tapes. Many tapes can store audio in two places, intermixed with the images or on a separate track along the side of the tape, for high fidelity recordings that come close to the quality of CD. Recording times range from 20 minutes to several hours depending upon the type of tape and the quality settings. All television programming used to be live. The performances were saved only in the minds of those who watched them. Then, in the mid-1950s, taped broadcasts became practical and the live aspect of television changed forever. Broadcasts could now be archived, played as reruns, broadcast during convenient times for a specific timezone, or sent overseas to other markets. Station managers could re-air programs without providing royalties to the actors, thus reducing costs (actors weren’t happy about this). A whole series could be shot in a period of weeks and then aired over a period of months, freeing up the actors and production staff to work on the next project. VHS-taped entertainment has been widely available through video rental stores since the early 1990s. In the 1980s, less expensive camcorders (camera/ recording combinations) were utilized by consumers to tape special events, weddings, birthdays, graduations, and amateur movies. By the mid-1990s digital camcorders began to appear and, by the late 1990s, the price dropped to the point where they became consumer items, with film use declining. video tape recorder, video cassette recorder VTR, VCR. A recording and playback device specifically designed to record simultaneous motion images and sound. The input is usually through video patch cords from microphones and cameras for live recording, or from camcorders and CDs, phonographs, and tapes for re-recording or editing. VCRs have been common consumer items since the mid-1980s; prior to that, they were generally used in the television and video editing industries. One of the earliest patent applications for a video tape recorder was submitted in 1927. One of the early ‘portable’ video tape recorders, based on new transistor technology, looked just like a large reel to reel audio recorder. It was introduced by Ampex in 1963. This large desktop model weighed about the same as a medium-large TV set, but was nevertheless only one-twentieth the size of previous floor-standing models. It used a single-head helical scanning mechanism and could record 64 minutes of programming on standard 8" reels. VCRs are much smaller now, and use convenient cassettes rather than reels. They have also been improved to support high fidelity sound and higher resolution images. video-on-demand VoD. A commercial interactive video system in which the user can request a specific video to be played at a particular time, unlike traditional TV programming where the station

determines which programs are to be broadcast, and when. A number of these programs have been tried in various regions with mixed success. It’s difficult to institute a pay service in competition with hundreds of ‘free’ channels on TV, which are primarily financed by advertising sponsors. The most successful video-on-demand systems appear to be those installed in motels and hotels that cater to business people attending professional conferences. Thus, one could say tongue-in-cheek that success depends in part on what the market will bare. See audio-on-demand, services-on-demand. videoconferencing The transmission of coordinated motion images and sound through computer networks. This is an exciting area with many systems vying for the front row seat. Technologies to transmit speech and images have been around since AT&T’s Picturephone system, which was developed many years before it was introduced to the public in the 1970s. However, full motion video as found in videoconferencing, or still frame video and sound as found in audiographics, didn’t reach practical speeds and consumer price ranges until the mid-1990s. Even then, they were mostly of interest to educational institutions and corporations. By 1997, however, consumer systems were beginning to be practical, especially with the proliferation of tiny monochrome and color video cameras similar to those found in security systems. See audiographics. vidicon A television with a photoconducting pickup sensor. VidModem A patented signal-processing technology from Objective Communications Inc. that can accommodate simultaneous two-way video, voice, and data over standard copper wires. VidModem uses FM signals and compression to transmit a 24 MHz FM signal through the 20 MHz bandwidth that is supported on phone lines. Vines A commercial virtual network based on Unix system V, from Banyan Systems. VIP See virtual IP. Virtual Interface Architecture VIA. An association of vendors who seek to describe and promote a generic systems-area network in order to facilitate the development of software for various X86- and RISCbased computers and their interconnections. VIA was established in 1996 as a small vendor consortium, and has grown to over 50 companies. See Scheduled Transfer. virtual IP, virtual Internet Protocol VIP. A function that enables the creation of logically separated switched IP workgroups across the switch ports of a Cisco switch running Virtual Networking Services (VNS) software. virtual LAN virtual local area network. A local area network in which the internal mapping is organized other than on the geography (physical relationship) of the stations. This allows the system to be segmented into manageable groups. Network software is used to administrate bandwidth and load, and to maintain a correspondence between the virtual LAN and the physical LAN. Newer versions of software

will even allow configuration and connections to be established through software with graphical user interfaces that display the equipment itself as graphic images, with lines to indicate the various interconnections. See local area network. virtual office A company or department loosely connected physically, but is communications-linked through various business telecommunications options such as cellular phones, videoconferencing systems, satellite modems, the Internet, etc. Some of the participants may be working at home or traveling. Some corporations mistakenly consider the ‘virtual office’ to be a new concept, but publishers and their associated writers have successfully employed this business model for decades. See telecommuting, telework. virtual path connection VPC. A path connection established on ATM networks along with an associated quality of service (QoS) category that defines traffic performance parameters. virtual private network VPN. A secure encrypted connection across a public network that enables organizations to utilize a public network as a virtual, private communications tool. Through a process called tunneling, the packet is encapsulated and transmitted. A VPN is a cost-saving measure for businesses that don’t want the expense of setting up an internally funded secure network, and yet desire interconnectivity between remote branches and departments accessible through the relatively inexpensive services of an ISP. VPNs provide a cost-effective alternative to laying cables, leasing lines, or subscribing to frame relay services. The disadvantage to VPNs over public networks is the response time. virtual reality VR. A phrase to describe electronically generated environments that interact with human senses to provide the illusion of the “real world” or to provide a fantasy world experience that cannot be achieved in the real world. Sensory headsets, goggles, helmets, implants, gloves, shoes, body suits, computers, monitors, chambers, and a whole host of visual/tactile/auditory two- and three-dimensional inputs are used to create virtual reality worlds. See Virtual Reality Modeling Language. Virtual Reality Modeling Language VRML (pron. ver-mul). VRML was originally released in 1994 by Tony Parisi and Mark Pesce. Initially dubbed Virtual Reality markup language by Dave Raggett, VRML is a file-format standard, built in part from the Open Inventor File Format, which was made freely distributable later in 1994 by Silicon Graphics, Inc. VRML provides a means for creating 3D multimedia and shareable virtual environments. Its inventors describe it as a 3D Web browser. It can be used in geographical, architectural, and industrial modeling; simulations; education; and games. In August 1996, when the version 2.0 specification of VRML was released, JPEG and PNG were specified as the two image formats required for conformance with the specification. VRML plug-ins are available for a number of browsers. The files tend to be very large, but there are

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unique opportunities, too, like taking a virtual ride on Mars Pathfinder, for example, an experience that’s worth the download time. VRML 97 was approved in January 1997 as International Standard ISO/IEC 14772-1. See Joint Photographics Group Experts, Portable Network Graphics, virtual reality, VRML. Virtual Switch Controller VSC. A type of soft switch characteristic of telephony networks that separate the switching layer from the call control layer, enabling a higher degree of interoperability among various protocols and controller systems. The VSC directs calls across multiservice packet infrastructures when combined with industry-standard protocols and interfaces rather than proprietary systems. VSCs can be implemented over newer signal systems such as SS7. Some implementations are also called Media Gateway Controllers (MGC). See Virtual Switch Controller chart on previous page. Virtual Tributary VT. In SONET networking, a sub-STS-1 signal designed for switching and transporting data. A VT Group (VTG) is defined as 12 columns, which can be formed by interleaved multiplexing, and a group may contain only one type of VT. VTs operate in two modes: locked and floating. The VT types are as follows: VT Signal

Rate

VT-1.5 1.728 Mbps

Digital Signal

Rate

DS-1

1.544 Mbps

VT-2

2.304 Mbps

CEPT-1

2.048 Mbps

VT-3

3.456 Mbps

DS-1C

3.152 Mbps

VT-6

6.912 Mbps

DS-2

6.312 Mbps

Virtual Trunking Protocol VTP. A virtual local area network (VLAN) autoconfiguration protocol from Cisco Systems. VTP is a Layer 2 messaging protocol that enables centralized VLAN switch configuration changes (additions, deletions, name changes, etc.), with the changes communicated automatically to all other switches in the network. virus A virus is computer code that is designed to be functionally similar to a biological virus in the sense that it uses its host to spread itself through a system. Just as a biological virus exploits the characteristics of its host to survive and replicate, a computer virus is designed to exploit the characteristics of a computer system and the activities of its users to survive and replicate. There are a number of subcategories of viruses, which may be organized according to how they are spread or how they affect a system. One major category is a computer worm, a virus that doesn’t specifically require a host file (although it still needs a host) in order to replicate. A virus insidiously takes advantage of normal computer functions to spread itself, just as biological viruses take advantage of normal biological functions. A virus may be associated with or attached to a process, file, or pattern of user activities (e.g., file

management functions). John von Neumann was one of the first theoreticians to delve at depth into the analogies between computing and self-reproducing biological systems, formulating a basis for biological analogies for computer viruses. Fred Cohen carried on this theoretical tradition in the early-1980s with research and a number of academic publications specifically related to computer viruses. Cohen is credited with the coining of the term in relation to computer algorithms. Cohen’s formal definition of a virus has been disputed at length, as it specifically refers to a program that modifies other programs “by modifying them ... to include a (possibly evolved) copy of itself.” While this definition describes some aspects of viruses, it is somewhat more narrow and noninclusive than more recent definitions of computer viruses. The creation and spread of viruses have some legitimate research and testing applications. Unfortunately, there are malicious uses as well and these are the ones that make the news. Since a virus is often intrusively or surreptitiously introduced into a system, the spread occurs without operator knowledge and consent and may not be immediately detected by users. Although the person inserting a virus may or may not intend explicit harm to the infected system, the recipient is almost always inconvenienced and suffers from a sense of invasion of both security and privacy. Users may also incur losses of time and money unanticipated by the person introducing the virus, especially now that systems are interconnected through the Internet and viruses can quickly spread to large segments of the population. Sometimes a virus contains bugs (programming errors) that cause damage unanticipated by the programmer. On personal computers in the 1970s and early 1980s, viruses were frequently spread through the sharing of files on floppy disks. Now viruses are most often picked up by uninformed users through network file downloads, which may include email with file attachments, but which most often is through downloads of public domain and shareware programs from bulletin board systems and the Internet. Reputable download sites will usually check uploads for viruses before making them publicly available, but not all site administrators have the time or in-depth knowledge to check every file. More recently, viruses have been spread through bulk mailings of email attachments to users who know how to send and receive email but otherwise have little knowledge of computer technology. In keeping with the general tone of humor in the computer community, many viruses have names. In fact, sometimes the name itself is the inspiration for the development of a virus or simply a joke about a proposed virus, e.g., the Paul Revere virus, for example, warns you of an impending attack to your system, once if by LAN, twice if by C/:, etc. There are thousands of viruses and dozens that are particularly virulent or significant in various ways. There isn’t room to list all of them, but here are a few examples of viruses and specialized viruses called ‘worms,’ to give a basic understanding of their

scope and common means by which they are spread. Adore Worm A network worm exploiting vulnerabilities in Linux machines, the Adore Worm uses random Class B subnet hosts as a pathway for downloading a portion of itself from an Asian Web server. The worm is stored on the local infected machine and executed through start.sh. It then moves and replaces /bin/ps and / sbin/klogd with files that allow entrance to the system and begins transmitting sensitive data to a number of email addresses, subsequently removing itself from the system (and restoring original files) through a cron daemon (timer program) in order to reduce the chance of detection. Linux vendors became aware of the worm and took steps to reduce the vulnerability of Linux software. APost An example of a typical email attachment virus targeted at the Microsoft Windows OS, detected September 2001. APost is an uncompressed executable file which, when run, displays an Urgent! Open dialog box. When the user clicks the dialog button, an error message is displayed, APost checks for a README.EXE file, creates one if absent (on drive root directories, including network drives), then adds a subkey to the user’s autostartup key with a path for the APost file. It thus starts each time Windows is loaded and then connects to Microsoft Outlook, grabs the mail server login/password information and replicates itself to the email addresses listed in the address book. Once APost has invaded another machine, the original email host is deleted to obscure its origin. Windows-host email viruses are not uncommon; the Sircam, Mawanella, Magistr, and VBSWG.X all spread through the execution of email-attached files. It is best never to run email executables from questionable sources. (There are even a small number of email viruses that don’t require an executable to be run in order to invade a host machine, so beware of unsolicited email.) AutoStart 9805 The first widespread, significant malicious worm to infect Macintosh computers, detected in 1998, AutoStart 9805 caused unexplained disk activity at regular intervals. This worm is limited to PowerPCs/compatibles running MacOS with active QuickTime applications (with QuickTime CD-ROM AutoPlay enabled). The worm “eats” its way through data, with different variants of the worm targeting different types of files, replacing the data with garbage so that it is not recoverable. Fortunately, the specificity of the worm prevents widespread damage, but the nonrecoverability of data may be disastrous for those infected. ExcelMacro/Laroux Considered to be the first real Microsoft Excel macro widely distributed as a virus, Laroux was discovered in 1996. Once a system is infected with this Visual Basic for Applications (VBA) program, Laroux becomes active when Excel is run and it will infect workbooks as they are accessed or newly created. While not as malicious as some viruses, this one is common and causes mischief and inconve-

nience by replicating itself. Internet Worm A self-reproducing program released onto the Internet in 1988, the Internet Worm affected about 10% of the hosts on the Internet by exploiting a Sendmail weakness. This is one of the more famous worms for a number of reasons. It spread very rapidly, caused more harm than was anticipated by the programmer, R. T. Morris, Jr., and was one of the first to gain broad media attention. The law and network administrators are not tolerant of potentially destructive activities on the Net, and this instance and its originator were not treated lightly. ILOVEYOU A “love letter” Visual BASIC script (VBScript) worm that spreads through email in the manner of a chain letter. The worm uses Microsoft Outlook to spread itself through email; it further overwrites VBScript and may spread using a mIRC client. When executed, the program copies itself to a Windows OS system directory and to the Windows directory, adding itself to the system registry so that it becomes active if the system is restarted. It adds keys to the registry and replaces the Internet Explorer home page with a link to an executable file. If downloaded, the file is added to the registry as well. The executable portion of the code is downloaded from the Internet and functions as a Trojan Horse to attempt to steal a password and modifies the system so that it becomes active each time Windows is started. The Trojan registers a new window class, creates a hidden window and quietly remains resident. After a startup and a certain timer status, it emails them to a specified address, presumably the author’s. The program sets itself up to replicate over an IRC channel if the user joins IRC and uses Microsoft Outlook to mass mail itself once to any people listed in the address book with the subject of ILOVEYOU. Melissa A rapidly spreading virus that became global within a short time and was discovered in spring 1999. Melissa proliferates through email. When infected, Melissa inserts comments into user documents based upon the television series “The Simpsons.” Melissa is also capable of sending out information from a user’s computer, information that might be sensitive in nature. The virus was apparently initially propagated through the alt.sex discussion group in Trojan Horse manner, that is, it was contained in a file that was purported to have the passwords for Xrated Web sites. Users who downloaded the document and opened it in Microsoft Word made it possible for a macro to execute, sending the file called LIST.DOC to people listed in the user’s email address book. Other Word-format documents can be infected as well, contributing to the quick spread of the virus, and may slow down a system if large email attachments are mailed through a Word email client without the direct knowledge of the sender with the infected system. There has been at least one variant of Melissa discovered.

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Virus attacks deserve serious attention. In an information-based culture, economic and social damage from a virus can be as significant as theft or destruction of important documents in a file cabinet. In fact, they have a greater potential for harm since the Internet doesn’t just reach into one file cabinet, but into millions, spread throughout the globe and further can disrupt not just the files but the information exchange mechanisms themselves. Viruses can have life or death consequences if inserted into transportation or health service computer systems. Damage from viruses varies, depending upon the nature of the virus and how it is spread. Common problems include corrupted files, interruptions by messages or questions requiring an answer, slowed transmission or processing times, and deleted or filled up storage. Because of their potential to disrupt work and financial transactions, many organizations have been established to deal with the issue of viruses (in addition to those focused on general computer security). Here is a small sampling. • In 1990, the Japanese Ministry of International Trade and Industry took steps to prevent the spread of viruses in Japan and initiated the management of Computer Virus Incident Reports through the Information-Technology Promotion Agency Security Center (IPA/ISEC). • The European Institute for Computer AntiVirus Research brings together the resources of universities, industry, security professionals, government, and the media to unite against efforts at writing and distributing malicious computer software. http://www.eicar.org/ • The U.S. Department of Energy (DOE) supports the Computer Incident Advisory Capability (CIAC) and an information site for reports of virus-related hoaxes. http:hoaxbusters.ciac.org/ There are about two dozen significant virus-specific discussion groups on the Internet. Of particular interest are the moderated USENET group comp.virus and email discussion list Virus-L. See back door, back porch, logic bomb, Trojan horse, worm, WildList Organization International, and entries prepended by virus. virus, hoax A report of a computer virus that doesn’t actually exist. Virus hoaxes are unfortunately somewhat common. They can cause mental anguish, work stoppage, and loss of productivity without the perpetrator actually writing and distributing a virus. The Good Times virus warning, initiated in 1994, is an example of a virus hoax that was still circulating several years later. virus, wild A virus that is extant in the general computer community. A wild virus is one that has the potential to do harm and infect systems because it has been “let loose” to replicate indiscriminately or according to a pattern established by the person programming the virus. Many viruses are developed for academic research or testing purposes and are not distributed into the computing community outside the laboratory or research environment. See virus.

Virus Bulletin A commercial, international U.K.based publication providing information and assistance with virus prevention, recognition, and handling. The Bulletin provides news information on security-related conferences as well as hosting an annual conference. Virus Catalog, Computer (CVC) This is considered one of the better technical sources of information on computer viruses for a variety of platforms, published by the Virus Test Center in Hamburg, Germany. virus checker, antivirus software A computer program that searches and, in some cases, disables viruses on a computer system or network. Virus checkers are a means to detect the undesired contamination or spread of computer viruses before they reduce productivity or harm a system. Computer viruses have been around almost as long as cost-effective computers, but it was the late-1980s before virus checkers became widely available and it took a few years of experimentation for them to become really effective. The virus checker itself should be obtained from a reputable source, since a virus checking program is a good place to hide a virus. Most virus checkers will bring up a dialog box or other alarm warning if a potential virus is detected. They may provide options enabling the user to deal with the virus in a number of ways. It should be remembered that a virus checker is only one aspect of computer security and that security from a network standpoint requires many more sophisticated tools and techniques than a standalone computer to remain secure and optimally functional. In general, virus checkers seek out anomalous patterns or disk access activities. They also typically include a database of viruses with known characteristics that are explicitly sought and identified. A computer running a virus checker is sometimes said to be ‘inoculated’ against viruses. Since inoculations are generally effective, but not perfect, it’s a reasonable analogy. Checkers can be initiated at computer startup and, now that most computers are multitasking, will often run as background tasks. It is usually a good idea to disable virus checkers when system maintenance, new installations, and reconfiguration options are run so that the virus checker doesn’t interfere with the process or display an alarm when the maintenance is being carried out. It’s also important to remember to restart the virus checker. Many institutional computers are installed with virus checkers as a matter of policy. These have become quite sophisticated and can detect and sometimes disable many different types of viruses. However, each time a new application, a new processor, or a new mode of operations is introduced into a computer system, it brings with it the potential to create a new type of virus that exploits the evolving technology. Like biological viruses, there will never be a ‘perfect’ virus checker that can anticipate or detect every type of virus. Virus checkers also have disadvantages. They can slow the system or interfere with system extensions, and it takes diligence and time on the part of the user to install, configure, and man-

age the virus checker itself. In most cases, the management involved in using virus checkers is considered good insurance against the massive damage that can occur from a virus that wipes out or corrupts important or sensitive information. In the absence of virus checkers, file backups and redundancy of live files are two strategies for reducing loss from virus attacks. Self-contained systems also help but are almost impractical in the trend toward a global computing environment. To help prevent the infection and spread of viruses, back up your data, investigate the available virus checkers, download only from reputable sites, and never open email or execute email attachments from questionable sources. See virus. visible spectrum The region of light waves perceived by humans as color, ranging from approximately 380 to 700 nanometers, or 3800 to 7000 angstroms. Technology cannot reproduce all of the colors of the visible spectrum, but humans cannot always distinguish between very closely related colors either. For practical purposes, the approximately 17 million colors displayed on better quality computer monitors and the approximately 10 million colors that can be printed with pigments on a press are sufficient for most personal and commercial needs. Outside the visible spectrum are the infrared and ultraviolet wavelengths. VisiCalc Visible Calculator. A historic early computer spreadsheet program, introduced in 1979, which was developed by Dan Bricklin and Bob Frankston for the Apple computer. VISIT Video A Macintosh- and IBM-licensed PCbased videoconferencing system from Northern Telecom Inc. that supports video, whiteboarding, and file transfers over Switched 56 or ISDN. An extra transmissions line is needed for audio. See Cameo Personal Video System, Connect 918, MacMICA, IRIS, ShareView 3000. Visual BASIC A basic Microsoft Windows programming application development product with a graphical user programming interface from Microsoft Corporation. Suitable for prototyping, although extensive use of dynamic linked libraries (DLL) may be needed for extensive applications development. visual ringer A small lamp on a phone console, usually a light-emitting diode (LED), which lights up when the phone rings. This is convenient in a noisy environment or for those who are hearing impaired. It is also common on multiline phones, to indicate which of the multiple lines are currently ringing. vitreous electricity A term coined by Dufay to denote the type of electrostatic charge produced on glass when rubbed with silk. Benjamin Franklin later proposed positive, a term that superseded vitreous. See electrostatic, resinous electricity. VLAN See virtual LAN. VLS Protocol The Virtual LAN Link State protocol developed by Cabletron Systems, Inc. is part of the InterSwitch Message Protocol (ISMP) providing interswitch communication between network switches running Cabletron’s SecureFast Virtual

LAN (SFVLAN). VLSP is used to determine and maintain a fully connected mesh topology map of the switch fabric. Within the switches are identical databases describing the topology maintained. Switches from which calls originate use this topology database to determine a routing path over which a call can be connected. VLSP supports equal-cost multipath routing and recalculates routes quickly with a minimum of routing protocol traffic. See RFC 2642. VLSI See very large scale integration. VMI V Series Modem Interface. A standard software front end and software layer that provides an entry and exit point to modem functions implemented through a variety of modem standards, for DSP Software Engineering modem products. VNS virtual network system, virtual network service. vocoder voice coder. A late 1930s invention that provided a means for analyzing the pitch and energy content of speech waves. This technology led to the development of a device designed to transmit speech over distance without the waveform. The transmission was expressed at the receiving end with a synthetic speaking machine. This general concept has evolved into linear predictive encoders. VoATM See Voice over ATM. VoFR voice over frame relay. See Frame Relay, voice over. voice activity detection VAD. A capability of digital voice communications systems to distinguish between information, such as speech, and the silences in between the speech elements. Typically, voice conversations consist of only about 40% talking, with the rest being pauses, silence, or low-level background noise. By transmitting information only when it is meaningful and filtering out the silent moments, it is possible to create a significant savings in the amount of data that needs to be transmitted. See silence suppression. voice-activated system A system such as a computer, phone, door, etc. that responds to the sound of a voice, which might be any voice or a specific voice. Voice-activated systems are calibrated to separate out the patterns and frequencies common to human voices from general background noise or other sounds. Technically, there’s no reason why it couldn’t also be configured to recognize the bark of a dog. This should not be confused with a speech-recognition system that recognizes actual words, not just a general or particular voice. Sometimes the two are combined. Voice File Interchange Protocol VFIP. A voice file interchange format proposed in 1986 when the ARPANET was still predominant. VFIP was designed to facilitate the interchange of speech files among different computer systems. The specification defined a header for describing voice data that includes a DTMF mask, information about duration and recording rate, and the encoding format. There was no requirement for the header to be explicitly attached to the file containing the speech data. See Network Voice Protocol, Voice Profile for Internet Mail, RFC 978.

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voice grade channel A transmission circuit sufficiently fast (usually up to about 56 Kbps) and suitable for transmitting clear voice conversations within frequencies between 300 and 3300 Hz. It is not typically suitable for other faster, higher bandwidth uses. Voice is a relatively low bandwidth application and does fine over copper wires, but others such as data transfer and video images require more. voice group In analog voice phone systems, a hierarchy for multiplexing has been established as a series of standardized increments. These are organized as follows: Group

Composition Number of Name Voice Channels

group supergroup

12 voice channels 5 groups

60 voice channels

mastergroup 10 supergroups

600 voice channels

jumbo group 6 mastergroups

3600 voice channels

voice over ATM VoATM. A growing area of interest, voice over ATM involves the digital transmission of voice conversations (which traditionally have been carried over analog phone lines) over asynchronous transfer mode (ATM) networks. Typically this involves taking a synchronous voice signal, segmenting it into cells, each with its own header, and interleaving the cells into the network with cells from other sources, eventually delivering the cell packets to their destination where they are converted back into a synchronous data stream. Since various queuing delays on the network will affect the transmission of the cells, the receiving buffer must have timing capabilities to organize the arriving cells so as to not leave gaps in the synchronous output signal. Delays of greater than 50 milliseconds of the conversation roundtrip must be avoided in order to prevent echo on the line. ATM networks make use of echo cancellers to reduce echo delay problems. Delays of greater than 250 milliseconds must also be avoided, as they result in perceptual discomfort on the part of the participants in the conversation. In order to maximize bandwidth over a public network, in which thousands of phone conversations coexist, compression techniques are commonly used to reduce transmission time and resources. See echo canceller, jitter, silence suppression, voice activity detection. voice over frame relay VOFR. See frame relay, voice over. voice over IP VoIP. Voice over IP involves digitizing conversations and other human vocalizations so they can be transmitted over data networks. This usually involves compression of the sound, as voice applications tend to be somewhat bandwidth intensive (though not as much as music and other types of sounds). Commercial VoIP offerings usually include

familiar phone services like Caller ID, and newer ones like follow-me services that allow forwarding to cell phones or pagers. Some systems are designed to use the public switched telephone network as a fallback if there are problems with transmission over the data network. Voice over IP Forum VoIPF. A group within the International Multimedia Teleconferencing Consortium (IMTC) that promotes and recommends voice over Internet Protocol (IP) technologies. See voice over IP. voice over networks There are now a variety of ways in which wide bandwidth data networks can be used to send telephone voice calls. The call can be initiated through a regular phone line that connects to a private or public network, or through a computer voice system hooked directly to a network. Thus, Internet Service Providers (ISPs) are emerging as collaborators and competitors with traditional copper line phone service carriers. voice over packet VoP. Devices capable of encoding voice signals for transmission over digital packet data networks. These devices typically support ITUT G Series Recommendations (e.g., G.729a) and may also have echo cancellers, fax and modem support, and voice-band signaling support features. VoP devices are useful for packetized cable telephone, Voice over IP (VoIP), and DSL access. Voice Profile for Internet Mail VPIM. An experimental profile submitted by G. Vaudreuil in February 1996 to define a digital computer-based voice messaging mechanism. Now known as VPIM, version 1, it was based upon the Audio Message Interchange Specification (AMIS), which facilitates message interchange among voice mail messaging on systems from different vendors. VPIM differs from AMIS in that it is a digital specification based on common internetworking protocols. The VPIM took into consideration common limitations of voice messaging platforms as they were implemented at the time. In September 1998, VPIM, version 2 was submitted as a Standards Track protocol by G. Vaudreuil and G. Parsons. It represents contributions by the VPIM Work Group of the Electronic Messaging Association (EMA). Significant changes to the original experimental specification were made based upon demonstrations at two EMA conferences in the mid1990s. VPIM is a profile for using MIME and ESMTP protocols for digital voice messaging services. It specifies a restricted set of Internet multimedia messaging protocols for the provision of a minimum common set of features for internetworking among different voice processing servers. See Audio Messaging Interchange Specification, Network Voice Protocol, Voice File Interchange Protocol, RFC 1911 (VPIM, version 1), RFC 2421 (VPIM, version 2). Voice with the Smile One of the many colloquial names given to the early female telephone operators. Others include Hello Girls, Central, and Call Girls. voicemail A type of data communication in which a

voice message is digitally recorded, usually through a small microphone interfaced with a computer, and sent through an email or voicemail client as an attachment or message. In order to hear the message, the receiver must have the capability to replay the message on the destination system. This is usually done either directly through the voicemail client or, if sent as an email attachment, it can be played with a separate player utility that is compatible with the type of sound file in which the message is stored. voicemail, electronic A system for intercepting an incoming phone call, playing a prerecorded digital message, and recording a message left by the caller. Many voice mail systems support multiple messages, multiple mailboxes, and menu hierarchies accessed through touchtones entered from the caller’s phone keypad, and may also allow a facsimile message to be transmitted manually, since many voice modems and voicemail systems support data and facsimile communications as well. Voice mail systems are not used just as fancy answering machines; they are also employed in faxback systems, technical support systems, and for providing product information and purchase options to callers. Because electronic voice mail applications are digital, they can be programmed to provide a wide variety of services, according to the needs and imagination of the programmer and user. volt (Symbol v or e for voltage) A SI unit of electrical potential. When a difference of electrical potential occurs between materials or portions of materials where there is a pathway between them, electrons seek a direction of flow which balances that potential. A volt is a unit of electromotive force (EMF) equal to that needed to produce a one ampere current through a one ohm resistance. In any given circuit, voltage, current, and resistance are related, so any one of those values can be computed if the other two are known. The unit is named after Alessandro Volta. See ampere, ohm, Ohm’s law, resistance. Volta, Conte Alessandro Giuseppe Antonio Anastasi (1745-1827) A physicist who pursued many of the ideas proposed by Luigi Galvani by studying the varying electrical properties of different materials. He questioned Galvani’s explanation of ‘animal electricity’ and proposed that the reaction of the muscle to stimulation of a nerve was due to unequal temperatures, and set up more rigorous experiments to determine what was happening. He showed how electricity could be generated by chemical action, which became known as galvanic electricity. This was the forerunner of the electrolytic cell. In 1800 he described his invention of the voltaic pile. Volta devised a condensing electroscope to respond to very sensitive charges and, with it, was able to demonstrate contact charges (though some were actually chemical interactions). The volt, a unit of electromotive force, is named after him. See Faraday, Michael; volt; voltaic pile. voltaic pile Alessandro Volta developed a system of layers of metal plates and paper or briny cloth that exhibited a difference in potential between the top

and bottom, which could be varied with the materials used and the number and organization of the layers. Volta attributed this difference to ‘contact’ electricity, though we now know that chemical factors play a role. Volta later modified the pile design to create what he called a crown of cups. The metal plates were placed in separate cups containing liquid, some distance apart. The plates were the poles or electrodes. Each cup is now known as a voltaic cell and a pair is known as a voltaic battery.

Two historic voltaic piles show the alternating layers of materials piled within supporting rods.

voltmeter, voltameter A galvanometer or other instrument such as an ammeter, connected in series with a resistor, calibrated to indicate electric pressure from electromotive force, or voltage differences in potential at different points of an electrical circuit. The voltmeter is connected in parallel across the circuit being tested and must have a higher resistance than that of the circuit being measured. In the past, sometimes also called a coulomb-meter or coulometer. See volt. von Bunsen, Robert Wilhelm A German chemist in the 1800s who did numerous experiments with wet cells and made improvements on the early inventions. von Guericke, Otto (1600s) An early experimenter who devised a machine that amplified and demonstrated the properties of negative and positive electromagnetic forces. Von Guericke used a spinning large sphere, molded out of sulphur, to investigate theories related to the spinning and magnetism of the Earth. He noted also that holding certain substances up to the sphere would produce a spark. He discovered basic principles of air pumps and demonstrated characteristics of vacuums with his Magdeburg hemispheres in 1663. A university in Magdeburg, Germany is named after him.

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von Kleist, Ewald Christian (1715-1759) A German physicist who discovered in 1745 that an electrical charge could be held in a glass vial with a nail or piece of brass wire inserted. A similar jar was developed independently by P. van Musschenbroek, known as the Leyden jar. See Leyden jar. von Neumann, Janos (Johann “John”) (19031957) A Hungarian-born American mathematician who developed novel and influential theories in advanced mathematics, game theory, and quantum mechanics. He was fluent in several languages, gregarious, and considered brilliant even by the elite scientists he worked with on the Manhattan nuclear bomb project. He produced a body of work in the mid-1900s that significantly influenced the design and evolution of computing machinery, including practical implementation ideas, conditional control, self-modifying code, program storage, and much more. Von Neumann collaborated with Mauchly and Eckert on the EDVAC computer project. See EDVAC.

Many of von Neumann’s contributions to game theory have applications and consequences for practical applications outside the realm of pure mathematics. These can be applied in the design and operation of ‘thinking’ machines.

von Neumann machine A classification of computing systems, based on the work of John von Neumann that includes single-instruction, singledata computation, which requires the repeated access and fetching of instructions and data. VoP See voice over packet. VOR VHF omnidirectional range. VP virtual path. A generic term to describe a logical connection consisting of combined virtual channels. In an ATM environment, it refers to the unidirectional transport of ATM cells belonging to virtual channels with the same endpoints, associated by a common identifier value. Related abbreviations include VPCI (Virtual Path Connection Identifier), VPI (Virtual Path identifier), VPL (Virtual Path Link), and VPT (Virtual Path Terminator). See virtual path connection, virtual private network.

VPC See virtual path connection. VPN See virtual private network. VQ vector quantization. VRAM Video RAM. Memory chips designed to enhance graphics display. Bisynchronous input/output. Related is SVRAM, Synchronous VRAM which reads only in or out at one time. See WRAM. VRML Virtual Reality Modeling Language. A programming language for developing 3D interactive image environments. This is a popular goal of video gaming and simulation developers. VRML allows you to create a sequence of images that can be presented in a World Wide Web environment in combination with a VRML client/browser. There are standalone and Web browser-compatible VRML clients available from several vendors. See Virtual Reality Modeling Language for historical background. VRML Review Board VRB. Originally the VRML Architecture Group (VAG), founded in 1995, the VRML Review Board participates in and oversees Virtual Reality Modeling Language development, documentation, and formal specifications. http:// vag.vrml.org/ VSAT See Very Small Aperture Terminal. VSC 1. See Vertical Service Code. 2. See Virtual Switch Controller. VSR See Very Short Reach. VSX Verification Suite for X/open. See X Windows System. VT-100 A data terminal, and terminal emulator, originally developed by Digital Equipment Corporation (DEC), which has become an industry standard and is widely used in telecommunications. The VT-100 emulation setting in telecommunications programs works with almost any remote system and is probably the one to select if you get strange characters or formatting in your software. Web browsers are quickly overtaking VT-100 as a front-end to online sessions, but VT-100 is still a valuable standby when connecting to remote systems in text mode. For the most part, it has been superseded by VT-220 and other newer standards, but it is still a good fallback if compatibility is a problem. VTAM Virtual Telecommunications Access Method. A data communications access method used in International Business Machines’ (IBM’s) Systems Network Architecture (SNA). See Systems Network Architecture. VTP See Virtual Trunking Protocol. VTS Vehicular Technology Society. Vulcan Street plant The historic location of the world’s first hydroelectric central power supplier. It provided direct current, as did many of the early power stations. The use of direct current vs. alternating current was a subject of hot debate in the early days of power stations, with Thomas Edison supporting direct current against strong opposition by Nikola Tesla and Westinghouse, who felt alternating current was a better choice. Alternating current first gained a foothold in Europe, where the high cost of batteries spurred inventors to look for other solutions. See Mill Creek plant.

W 1. abbrev. wait. In the Hayes modem command set, W is a dial string modifier that directs the sequence of events to wait for the dial tone before continuing with any further operations. 2. abbrev. watt. See watt. 3. The USOC FCC code for wall mount jack. 4. abbrev. white (as in B & W TV). 5. abbrev. wideband, which is now often used as a prefix with other telecommunications names and abbreviations. 6. abbrev. wide as in wide area network (WAN). 7. symb. work. 8. abbrev. World and Wide and Web (and other ‘W’ words) simultaneously when used with a number modifier, for example, W3. This shorthand format is a reference to mathematical notation. W-CDMA abbrev. wideband Code Division Multiple Access. See Code Division Multiple Access. W-DCS See wideband digital cross-connect system. W2XBS The Radio Corporation of America’s (RCA’s) first television broadcasting station, located in the city that was the preeminent hotbed of broadcasting for decades, New York. W2XBS was established in 1928 and gave the popular cartoon character “Felix the Cat” the exposure that made him a ‘star.’ In 1931 a W2XBS transmitter was installed on the Empire State Building. In May 1939, W2XBS became a significant pioneer in sports and cultural broadcasts. In May 1939, it broadcast the first televised baseball game. Then, in February 1940, it was the first to provide television coverage of ice hockey, basketball, and a number of other athletic events. In March 1940, it broadcast the first opera presentation on TV. W3 See World Wide Web. W3C See World Wide Web Consortium. WAAS See Wide Area Augmentation System. WABI See Windows Application Binary Interface. WABIserver See Windows Application Binary Interface server. WACK wait (with) acknowledgment. A signal sent by a transmissions receiving station indicating that there needs to be a wait or delay before transmitting a positive acknowledgment (ACK). For example, the receiver may acknowledge receipt of the last block of transmitted data but not be ready to receive more data, a common situation with network printing devices or data relays or routers.

W WACS See White Alice Communications System. Wade insulator A very early blown glass, unthreaded telegraph pole insulator. The historic Wade insulators from the mid-1800s were secured onto their wood brackets with flaps of rough burlap. They resembled inverted medicine bottles with straight sides and were protected with bullet-shaped wood covers. See insulator, utility pole. wafer A fine thin disk, usually cut from a larger piece of the substance. Many materials are cut into wafers including semiconductor materials, quartz crystals, and synthetic gems used in optical systems. Silicon is one of the most common materials used in semiconductors. Many electronic chips are layers of wafers and photovoltaic panels are arrays of wafers. Since many wafers used in electronics and other industries are extremely thin, production methods are very specialized. A traditional metal saw is not appropriate, especially since the part cut away and lost by the saw blade, the kerf, would be larger than the width of the wafer itself. WAG Wireless Application Group. See WAP Forum. WAIS See Wide Area Information Server. Wait on Busy U.K. term for a Call Waiting type of optional subscriber service in which a caller encountering a busy signal can wait on the line until the call in progress is over and be automatically connected. walkaway An individual who leaves a process without completing it. This is an important concept in programming and many aspects of telecommunications. Operators, software developers, and hardware manufacturers must anticipate possible walkaways and decide when to turn off a system or time out an abandoned process. • On ATMs, a user may walk off and forget to take the bank card. Some machines will beep loudly to alert the user before she or he is out of earshot. Some are programmed to recall and hold the card if it is not removed in a specified amount of time. • On computing systems, processes are often timed out and the user may be logged off after a certain period of inactivity. This is particularly important if there are limited logins available or limited IP numbers assigned to Internet connections that must be shared among many users.

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• In telephone networks, a user might walk away without hanging up the line. In this case, the phone signaling system may detect the inactivity and send the message “If you’d like to make a call, please hang up ...” If this fails to get attention, it may be followed by a loud intermittent raucous buzzing sound. • On information kiosks or computerized library card catalog systems, users often leave the information system in various states that are confusing to a new user accessing the terminal. The software may be programmed to return to the main menu after a period of inactivity. wait state In computer programming and processing, a time during which the processor waits. This may be explicitly established or may be dependent upon other events. Wait states are introduced for many reasons, for timing, synchronization, to reduce power demands, etc. They are especially prevalent in systems where there is a disparity between the processing or data transfer speeds of various interconnected components. The wait state can help manage these discrepancies by ‘slowing down’ the faster components relative to others. Wake-on-LAN An IBM system for enabling centralized network systems to ‘wake up’ or power on remote workstations. This is useful for remotely updating software, logging files, and uploading or downloading messages or other files. walk time Propagation delay in a Token-Ring network. Walk time plus service time combines to form scan time, the mean interval between the arrival of tokens at any given station. walk-through A process of being presented or going through the basic physical, visual, or functional aspects of a product or process. Thus, a sales rep might walk through a new program with a potential buyer, or a development team might internally evaluate a product or process once it has begun to come together. Use a hyphen when it’s a noun, and a space when it’s a verb. wall outlet A wall-based electrical or fiber connection point for various devices designed for easy connections, often positioned above the baseboard or at shoulder height. Some devices are semipermanently wired into wall outlet (e.g., wall phone), but many wall outlets are designed for the modular, temporary installation of electrical cords, transmission cords (e.g., extension phone), and other connections. wall telephone A telephone designed to mount on a wall at a comfortable height for the user. Wall phones were common until the 1960s when they began to be superseded by smaller, portable, plugin “extension” phones. Wall phones are still used in premises where theft might be a problem (restaurants, pay phone booths, etc.). Wall, Larry Software author of rn, a popular newsreading system, and Perl, a significant interpreted scripting language widely used on the Internet. Larry Wall has also authored several bestselling programming books, most notably books on the Perl programming language. See Perl.

A depression-era Northern Electric wall telephone that used a crank and external bells (top) for the ringer. The wooden flap opened up to provide access to the crank mechanism and wiring. [Classic Concepts photo; used with permission.]

wallpaper A colloquial term for background patterns in a screen display. Computer desktop backgrounds can often be configured into wallpaper-like patterns through utilities bundled with the operating system or with shareware or commercial software available for this purpose. It is useful not only for setting the aesthetic tone and light levels of a display, but also helps the user distinguish active windows from background icons and helps identify user environment on a system that is being used by different people. Apple, Apollo, and Sun computers all had selectable or configurable wallpaper backgrounds by the mid1980s and it’s likely that the Alto, the imaginative Xerox predecessor to the Apple had them before personal computers were available. WAN See Wide Area Network. WANMC See Wide Area Network Management Center.

wander Timing deviation or drift. In networking, especially high speed networks in which synchronization is important, wander and jitter can contribute to signal degradation. Physical factors such as connectors, regenerators, or temperature variants can contribute to wander due to propagation delay. Over longer distances, this effect can become magnified, with the pulse position gradually shifting. In SONET networks, wander has a more specific meaning; it consists of a phase variation tracked and passed on by a phase-locked loop. This is managed by tracking the incoming signal and passing it through a filter, to extract timing data. Wang Global A firm that formed an alliance with Microsoft to provide local area network (LAN) services. Wang Global was merged into Getronics NV,

a Netherlands information technology (IT) services firm, in 1999. WAP Wireless Application Protocol. See WAP Forum, Wireless Application Protocol. WAP Forum, WAP Application Protocol Forum Ltd. An industry trade association representing members from all sectors of the mobile communications industry supporting the Wireless Access Protocol (WAP). The Forum is focused on developing and promoting interoperable, securable wireless network technologies and standards and in supporting their deployment and utilization. WAP pursues these goals through the establishment of Charters that are handled by Specification Working Groups (SWG) and Expert Working Groups (EWG). Groups are represented in the WAP Forum Groups Summary chart.

WAP Forum Groups Summary Subgroup WAP Architecture

Established Working Group Aug. 2000

Description

SWG

The development of wireless architecture to provide a framework for specifications built around Wireless Application Protocol (WAP). This is an ongoing project requiring consistency, completeness, and conformance to WAP specifications. Open to all members. Wireless Application Group (WAG)

Jan. 2001

SWG

Responsible for specifying WAP application technologies, including application enablement features such as programming interfaces, content formats, and user agents (UAs) to enable data services on handheld devices. WAG will be active as long as specifications and their maintenance are required and is chartered to cooperate with various standards bodies and specification groups. Although one of the more recent Working Groups, much of the effort within the WAP Working Groups has concentrated on this group. Open to representatives of member companies. Wireless Protocols Group (WPG)

SWG

A Charter was not available online as of July 2001, but the group is responsible for handling specific protocols related to WAP, such as the Next Generation (G3) wireless services. Open to member companies. Wireless Interoperability Group (WIG)

SWG

As of July 2001, there was no publicly listed Charter for this group. Wireless Telephony Applications (WTA) Feb. 2001

SWG

Responsible for defining a framework for making simple, secure, extensible mobile network services accessible through WAP services. It further assists the WAE group in defining a WAE architecture that enables a single WAP application-level architectural model. Open to member companies. Wireless Security Group (WSG)

Feb. 2001

SWG

Responsible for specifying WAP security protocols and services as well as interaction with entities that serve security purposes. Open to member companies. Multimedia Expert Group (MMEG)

Mar. 2001

TWG

A coordination and information-sharing group responsible for defining requirements, use cases, and/or recommendations focusing on mobile multimedia applications and services and for positioning WAP as the preferred platform for developing wireless multimedia services. Subgroups concentrate on specific technologies such as Smart Cards (SCEG), telematics, wireless developers, and others. Open to member company representatives and multimedia communications experts.

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The WAP Forum has also initiated a developer registration and content verification program and a WAP certification program for manufacturers to apply for certification testing for compliance to the WAP protocol suite. See Wireless Access Protocol. http://www.wapforum.org/ WAP Security Toolkit WST. A suite of security mechanisms to support security aspects of the Wireless Applications Protocol developed by the WAP Forum for wireless portable devices. See WAP Forum, Wireless Transport Layer Security. WAR See Wireless Application Reader. war dialer An automated dialing system that sequentially dials a new number for each succeeding call, sometimes taken from a computer database. War dialers are used by those dialing to a large number of phone-access BBS systems, by collection agencies, telemarketers, and teleresearchers. There are restrictions in some areas on the use of war dialers for commercial solicitations. war room A strategy and decision-making facility, often related to critical big business or government activities. The war room may be a closed, secure environment with no equipment other than perhaps tables and chairs, or it may include sophisticated electronics for monitoring and communications. The U.S. Department of Defense opened a new war room in the Pentagon in 1969. It was equipped with a variety of high technology systems, including closed-circuit television, teletype communications, and various data processing systems and has since been updated to reflect the evolution in technology. War rooms are also common to specific command centers and are often interlinked. For a lighthearted introduction to war rooms, the Hawk Films/Kubrick/Peter Sellers movie Dr. Strangelove is a classic parody of war room activities. See skunkworks. warble tone A tone resembling a bird’s warble in that it fluctuates in tone periodically, sometimes quickly. Because people tend to notice fluctuating tones more readily than steady sounds, warble tones are often used as signal tones, as on public address systems. A warble tone is usually one of the options included with multitone generators, which also feature sirens, steady tones, and timed pulses for various public or employee alert needs. Warble tones are used diagnostically in conjunction with an integrating detector device to measure crosstalk in a transmissions line. WARC See World Administrative Radio Conference. warm boot Restarting a system without powering it off. On a computer, this is often accomplished by selecting a ‘restart’ menu item or using a designated combination of keyboard keys. On a computer, a warm boot typically resets most of the operating system and basic hardware configuration parameters, but may not go through the entire repertoire of hardware systems test sequences that may be stored in ROM. See reboot. warranty A promise on the part of a manufacturer,

retailer, or service provider that the goods or services provided will meet stated terms of manufacturing quality, use, or lifespan. Most warranties are limited to manufacturing defects, and refunds, replacements, or damages up to the original price or replacement price of the product. Terms of warranties in the computer industry tend to be about three months, although longer warranties on equipment are now beginning to be honored, ranging from one to five years. Few warranties will cover abuse, loss, or damage from natural disasters. Washington Internet Project A communications project with a portal on the Web providing news, views, discussion groups, an index of regulatory proceedings, and other communications venues for the discussion of significant Internet issues related to federal and state governments. It is also known as CyberTelecom. http://www.cybertelecom.org/ WASI Wide Area Service Identifier. watch, watchpoint A means of monitoring program functioning, usually within a software debugger, while the application is being executed. Watch commands are often used in conjunction with trace and break commands and watchpoints are set much the same way as tracepoints. water bore A device that uses a highly pressurized jet of water to bore holes intended for the insertion of underground conduit and cabling. watermark In the paper printing industry, a symbol or shape embedded in the paper, which is usually so subtle that it is seen only if the paper is held up to the light or held up to particular frequencies of light. The watermark is typically paler or more transparent than the surrounding medium. Watermarks are often used as identification signatures on quality papers and as identification security marks on currency, bonds, stocks, etc. The term has been used analogously in computer applications to indicate a subtle background image that is inserted behind the active layer on a computer screen, that is, behind a text document, Web page, or other application. In addition, the term is being used to describe a type of copy protection or data security mechanism in which a label is inserted into the data to identify it, without interfering with the quality of the presentation of the data. See SMASH Project. WATM Wireless ATM. A number of initiatives are under way to provide better support for wireless services over asynchronous transfer mode (ATM) networks. One of the proposals is for a Radio Access Layer (RAL) by the Olivetti Research Laboratory, which has developed a prototype wireless ATM local area network (LAN). See Research in Advanced Communications in Europe. WATS Wide Area Telephony Service, Wide Area Telecommunications Service. A discounted long-distance service. This service originated from AT&T, but the name became generic and is now broadly used. WATS services can be incoming, outgoing, or both; WATS lines can be installed with incoming and outgoing services handled over the same

line (although this may limit the service). As with many discount services, the savings are dependent upon the pattern of usage. If WATS lines are used more often and longer, the savings may be negligible or nullified.

during World War II. He rejoined IBM in 1946 and became Vice President and a member of the Board. In 1956, he succeeded his father as Chief Executive Officer (CEO). Following a heart illness, Watson stepped down from the position of CEO in 1971, but remained as Chairman of the Executive Committee until he retired in 1985.

Thomas A. Watson, approximately 1914 or 1915. [Library of Congress American Memory Collection.]

Watson, Thomas A. (1854-1934) A multitalented machinist and famed assistant to Alexander Graham Bell, Watson filed for a telephone patent for a twobell ringer in 1878. He also designed the Watson board, a very early and not entirely practical, telephone switchboard. By 1901 he was operating the largest shipyard in the nation, but was replaced as head of the company and left the firm to pursue geology. With encouragement by Bell, he subsequently studied voice (Bell was a superior orator) and became an actor and playwright. Watson, Thomas J., Sr. (1874-1956) Watson joined the Computing-Tabulating-Recording Company in 1914 and became President the following year. In 1924, the Computing-Tabulating-Recording Company became International Business Machines (IBM), a significant firm in computing history. After four decades at the helm, he passed the position on to his son, Thomas J. Watson, Jr. (1914- ) who also “inherited” a number of coveted board positions in the business community. See Hollerith, Herman; International Business Machines. Watson, Thomas J., Jr. (1914-1993) The son of business magnet, Thomas J. Watson, Sr., Watson was granted a degree at Brown University. According to his biography, he was not very academically inclined and got his degree with help from scholarship donations by his father. Watson, Jr., became a sales representative for IBM and then took time away from the company to serve in the U.S. Army Air Corps

A historic communication from Thomas A. Watson to A. Graham Bell on Bell Telephone Company stationery, dated October 1877 in which Watson describes the “perfect success” of the telephone in the U.S., with “almost 2200 being in use at the present time.” Watson further describes the central office system in Boston as having “100 stations connected with it and will have 3 times as many in as many months.” [Library of Congress American Memory Collection.]

W Watson, Research Center Thomas J. The Thomas J. Watson Research Center is headquarters for the IBM Research Division, with eight laboratories worldwide. Historically, the lab is descended from the Watson Scientific Computing Laboratory that was opened in February 1945 by Thomas J. Watson, Sr. and Nicolas Murray Butler, President of Columbia University. The IBM/Columbia facility was expanded in 1953 and ceased operations in 1970. A new lab, also named after the longtime President of IBM, was established by IBM in 1961. This center focuses on physical, mathematical, and computer sciences; technology; semiconductors; and information services. Watson, William (1715-1789) An English experimenter who demonstrated in 1746 that electrical current could be sent through a wire about 3 kilometers long, using the Earth as a return conductor, a

technique later applied in many technologies including early two-way telegraph systems. watt W. An absolute meter-kilogram-second (MKS) unit to describe electrical power that is equal to the amount of work done at the rate of one absolute joule per second. Described a different way, a watt is the electrical power expended when 1 ampere of direct current (DC) passes through a resistance of 1 ohm. For large units of power, the kilowatt (1000 watts) is typically used. See Ohm’s law; power, electrical; Watt, James. Watt, James (1736-1819) A Scottish inventor who pioneered the steam engine, after whom the watt is named. WATTC See World Administrative Telegraph and Telephone Conference. wattmeter An instrument for measuring electrical power in watts. The wattmeter is similar to a dynamometer, which measures force or power in that it employs a moving coil and a field coil; however, the windings on the coils differ from the dynamometer. See dynamometer. wave A periodically oscillating or undulating process, or physical or electromagnetic phenomenon. WAVE A commercial product from MPR Teltech Ltd. which permits the simultaneous realtime connection of up to eight different sites through ATM switches for broadcast TV quality videoconferencing. wave audio See waveform audio. wave division multiplexing WDM. A means of using separate channels grouped around distinct wavelengths to increase the capacity of a fiber optic transmission system. Proposed methods for multiple wave division are known as dense wave division multiplexing (DWDM). wave filter A device, as a transducer, which separates out waves on the basis of frequency. Some loss occurs during this process, depending upon the method used and the characteristics of the wave. See wave trap. wave length See wavelength. wave packet A short burst or pulse of waves. wave trap A device usually placed between the receiver and the incoming waves that excludes unwanted waves, especially undesired frequencies or interference waves. Like the receiver itself, a wave trap is often tunable to optimize control over incoming waves. See wave filter. waveform The shape, or spatial characteristics, of an electromagnetic wave. 2. A graphical representation of the spatial characteristics of an electromagnetic wave, as on a scope or 2D or 3D coordinate system illustration or modem. Waveforms are typically graphed according to amplitude across time. Waveforms with certain recognizable shapes, when graphed, have been given names to distinguish them from one another. waveform audio A digital representation of sound waves, often created by sampling through a pulse code modulation (PCM) technique. Waveform

editing on microcomputers became well supported in the mid-1980s. The early Macintosh supported audio waveforms, and many pioneer computer musicians used Macintosh music sequencing and editing software to create electronic music compositions. The Atari ST was released with a basic midi device built in and the Amiga in 1985 came with built-in multiple channel 8-bit stereo sound. By the late 1980s, 16-bit third-party sound cards were available for most of these computers. Todd Rundgren, musician, composer, and multimedia designer, began using Macintoshes and Amigas to create digital sound videos and CDs in the mid and late 1980s. There are many file formats for storing sound waves, and sound files can be played from Web pages on the Internet with browsers that support sound (assuming the computer has a sound card; most types of computers came with built-in sound cards by 1986). The .wav extension is commonly used to designate audio files of a particular format on the Internet. waveform editor An applications program on a computer, or specialized electronic device, which allows the user to display, evaluate, and alter the characteristics of a wave. A computer display often uses a graphics system to represent the wave, as in traditional oscilloscopes. The dials on the simulated computer scope are often represented as buttons on the screen or may be input from a joystick or specialized peripheral. Waveform editors are used to alter the characteristics of music patches, voice, or speech files. Adjustments can alter the volume, tone, harmonics, echo, and other characteristics, and when converted to digital form on the computer, the adjusted files can be stored and replayed later, or cut and pasted to create songs or speeches. Digital sound editing with a waveform editor can be combined with digital video sequences to synchronize the sound and video and to “put words into people’s mouths.” See waveform audio. waveform monitor An oscilloscope or oscilloscopelike computer applications program that surveys an input signal and displays its characteristics on a screen. Typically there are dials or graphical user interface gadgets and buttons to adjust the displayed wave. waveguide A device for confining and channeling the propagation of electromagnetic waves, often through a hollow round tube, hollow rectangular tube, coaxial cable, or fiber optic cable. The interior environment of the waveguide will vary with the type of wave being channeled, since it must allow sufficient room relative to the characteristics of the wave so as not to change or diminish the signal. Thus, waveguides are more practical for high frequency waves such as microwaves. waveguide dispersion The process by which an electromagnetic wave becomes distorted as it passes through a waveguide. Since the dimensions and shape of a waveguide interact with the phase and velocity characteristics of a wave, the waveguide’s

geometric properties may cause dispersion of the guided signal. waveguide laser A gas laser that incorporates a tube as a waveguide to channel the direction of the laser beam. waveguide lens A device used with microwaves, in which the waveguide elements act as lenses to produce the required wave phase changes through refraction. waveguide phase shifter A device that takes the phase of the incoming waves and adjusts them in terms of their output current or voltage. waveguide propagation A type of long-range communication that makes use of the atmospheric waveguiding channels that arise between the ionospheric D region and the Earth’s surface. See ionospheric sublayers. waveguide scattering Scattering of an electromagnetic wave that occurs due to the geometric characteristics of the waveguide structure, as in an antenna or fiber optic cable, not due to the materials of which the waveguide is constructed. WaveLAN A commercial IEEE 802.11-compliant wireless local area network (LAN) system. WaveLAN was originally introduced in North America by AT&T in 1990 and 1995 and in Australia and New Zealand by Lucent Technologies in 1998. The system has been installed in more than 50 countries overall. Without extension antennas, the system has a range of up to about 400 meters. Early versions of WaveLAN used 915 MHz, while newer WaveLANs use 2.4 GHz direct sequence spread spectrum (DSSS) technology and are designed to co-exist with standardized 10-MBps DSSS technologies. wavelength The distance, when measured from any point on a wave, to the corresponding point in the phase of the next wave in a related type or series of waves, such as sound or light waves. A wave’s length is sometimes described in units of distance and sometimes in terms of the time it takes, from the phase of a wave to the corresponding phase of the next related wave, to travel through the same point. Waves can differ dramatically in length, as can be seen, for example, from the various categories of designated radio bands, which range from a single millimeter (EHF band) to tens of kilometers (VLF band) when expressed in distance, or from 30 to 10 kHz when expressed in frequency or cycles per second. See band. Wavelength-Agile Optical Transport and Access Network See WOTAN. wavelength division multiple access WDMA. One of two common optical multiplexing techniques in which each transmitter transmits at different wavelengths within a narrow spectrum, and the receiver extracts the desired wavelengths with a bandpass optical filter. See space-division multiple access. wavelength division multiplexing WDM. A means of multiplexing different wavelengths through the same strand of fiber to greatly increase the capacity

of data transmission over fiber optic cables. Optical signals at different frequencies do not interfere with one another. The technology permits a substantial amount of data to travel over even one strand, and when the strands are bundled, it permits transmission in the terabits per second range, ample for high bandwidth applications like video, data, and simultaneous voice. See frequency division multiplexing. wavelength shifter A device or process that takes an incoming series of waves and shifts their frequencies so the outgoing waves are related to the incoming waves, but in a different range. It is very common in satellite communications for the incoming signals to be shifted so they don’t interfere with subsequent outgoing signals. In photocells, wavelengths may be shifted by means of compounds so that the length of the outgoing waves is related but greater. wavelet analysis Wavelet analysis involves looking at time and frequency. A prototype function (analyzing wavelet or mother wavelet) is used as a starting point for dilations and translations by creating a highfrequency reference and a low-frequency reference, which are analyzed, in turn, for aspects of time and frequency. See wavelet theory. wavelet filter compression An analysis low/highpass filter technique used in wavelet compression by selective quantization in which images are decomposed into frequency bands. Wavelet encoding combined with vector quantization (VQ) has been shown to be a good means of compressing image data, and several schemes for accomplishing this have been developed. See wavelet. wavelet packets Calculated linear combinations of wavelets that retain many of the properties of the parent wavelets from which they are derived. wavelet theory A set of mathematical concepts and techniques related to the representation and manipulation of oscillating wave forms according to scale. Wavelet analysis provides a means to use approximating functions contained within finite domains and are well-suited to representing data with sharp discontinuities. Wavelet theories and algorithms are being applied to audio and image compression with some practical and interesting results. When wavelet concepts are used in image compression, they share some characteristics with discrete cosine transform (DCT), although the functions used are more complex than cosines. Wavelet compression is sometimes used in conjunction with other methods, such as vector quantization, to provide low-loss, high-compression ratios. They have also been used in turbulence studies, human vision, radar systems, astronomy research, and fractal imaging. Wavelets are used in conjunction with, and sometimes instead of, Fourier transform methods, depending upon the application. Unlike Fourier transforms, wavelet transforms are not limited to sines and cosines, and can comprise an infinite set. See discrete cosine transform, Fourier transform, wavelet transform. wavelet transform, discrete wavelet transform DWT. A linear mathematical technique that is a

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subset of wavelet packet transform. DWT is used to generate a data structure with segments of various lengths. In a sense, a transform is a means of rotating a function so it can be visualized and analyzed with a different set of tools, those tools being not only mathematical algorithms, in this case localized frequency wavelet functions, but also conceptual models. To simplify calculations, the DWT is factored into a product with a few sparse matrixes using selfsimilarity. Wavelet transforms differ from Fourier transforms in that they are localized in space, and an infinite possible number of basis functions can be applied to them, unlike Fourier transforms which use only sines and cosines, but they also share some common basic properties. See Fourier transform, wavelet, wavelet packets, wavelet theory. wavelet types Due to the variety of possible types of wavelet transforms, some wavelets have been grouped into families, on the basis of vanishing moments, and subclasses, on the basis of the number of coefficients and level of iteration. Many more await development and discovery. The Daubechies wavelet family has a fractal structure. Others are Symmlet, Coiflet, and the simpler Haar family, often used to introduce wavelets in educational contexts. wax master An original physical master intended as a prototype for making one or more copies, usually with a more durable material. Since wax is easily shaped, stretched, changed, and otherwise manipulated, it is a good medium for creating prototypes of production parts. Wax is used to design jewelry, sculpture, certain types of audio recordings, prototype components, and more. Once sufficient copies of the original are made, the wax is sometimes reused for other projects. way station An intermediate office in a communications line. An intermediate phone in a way circuit, one which is not the main console. way wire, way circuit A party line circuit that connects a number of subsidiary stations to a main switching or relay station. See party line. WBC wideband channel. WBEM See Web-Based Enterprise Management. WCAV Web Clipping Application Viewer. See Web Clipping application. WCP 1. See Web Clipping proxy. 2. See Wireless Certificate Profile. 3. wireless communications platform/product. 4. See wireless communications protocol. WDL Windows Driver Library. WDM See wave division multiplexing. WDMA See wavelength-division multiple access. WDP 1. See Wireless Datagram Protocol. 2. Work/ Workforce Development Program. wearable public key infrastructure WPKI. A public key infrastructure and accompanying applications described by Muller and Smart in June 2000 for use with the Bristol University Cyberjacket. It is a lowcomputational-overhead system for providing authentic records of meetings and conversations and

a password system where the user doesn’t have to remember passwords to facilitate wearable computing. Web colloq. See World Wide Web. Web address See Uniform Resource Locator. Web browser A display and hypertext client used as a front-end to Web-related services on the Internet. For a fuller explanation, see browser, Web. Web Clipping application WCA. A software application technique used by Palm Computing to provide the capability to utilize a small Web site or related type of database on a wireless Palm PDA device. These have also been called Palm Query applications (PQAs). A WCA is a form of application partitioning in the sense that part of the application is on the device and part of the information is presumably being accessed from a remote proxy server that connects, for example, to a remote Web site on the Internet. This approach is intended to reduce download times and to provide a solution for Web access with appliances with limited resources (as with wireless handheld devices). A Web clipping application uses a subset of HTML (hence the term clipping) to create basic forms, graphics, and hyperlinks, which is then compiled with the Web Clipping/Query Application Builder (WCAB or QAB). The application runs inside the Web Clipping Application Viewer WCAV. Web Clipping can be used to implement a number of types of microbrowsers. See microbrowser, Web Clipping proxy. Web Clipping proxy WCP. Web clipping proxy servers provide an environment for accessing Webtype information via Web Clipping applications. The application connects with the WCP through a wireless connection, makes a request that is handled through the Internet by the WCP and sent as a compressed product back to the wireless device and Web Clipping app. It may also be used for simulating and testing Palm OS Web Clipping applications. See Web Clipping application. Web hosting A service in which Internet Service Providers (ISPs) enable a business or individual to store Web pages on the ISP’s computer system, instead of on the user’s computer. Since an ISP’s machines are typically connected to the Internet all the time and since a certain amount of Web server setup is needed to make a Web site function properly, it is very practical to have the ISP manage the administration of the Web server. The design, management, and updates of the individual Web page are left up to the user or can be handled by the ISP for a fee. An ISP can also arrange for the registration of a domain name for the Web site, with the user paying the fee to the ISP, who passes it on to the registration authority, or with the user paying the registration authority directly and the ISP handling the setup of the necessary computer configuration. See domain name. Web master See Webmaster. Web search engine The World Wide Web is an enormous repository of information and it changes

all the time, so there’s no practical way to find a particular page without a little help. Enterprising programmers quickly realized that tools were needed to make it easier to locate information on the Web. As a result, they developed ‘search engines,’ which are application programs in Web format designed to facilitate the location and retrieval of information according to user-specified parameters or categories. Most search engines provide a text window for the user to type in a keyword, after which the user clicks a “Search” button, resulting in the display of a listing of relevant Web pages to which the user can jump by clicking on the highlighted hypertext link. It is not unusual for a search keyword to result in hundreds, thousands, or even millions of ‘hits,’ that is, pages that include the specified keyword. It’s obviously not practical to try to visit several thousand sites, so most search engines allow the user to narrow the search by adding more keywords and providing operators such as AND and OR to focus the search. This can reduce the resulting hits to a more manageable number. Search engines also provide means for businesses and individuals to get their Web pages listed so others can find them. There is usually a button at the top or bottom of the page for this purpose. There are thousands of search engines on the Web. Many sites have their own local search facilities, but there are also a dozen or so very prominent Web search tools that are commonly used. The applications listed in the appendix all perform general searches of the Web, with the exception of DejaNews (now part of Google Groups), which searches newsgroups. Many also have ‘specialties’ to set them apart from the others. Note that these search engines catalog millions of pages and they are not necessarily up to date. The best search engines seem to have a lag of about three weeks to three months from the time a site is submitted until it is added to the database. See the appendix for a list of major search engines. Web server A client/server model system on a multiuser network that serves requests for HTML-based Web pages that are part of the World Wide Web. A Web browser is a type of client software that communicates with the server through HyperText Transfer Protocol (HTTP), and displays the information received from the server in the form of a Web page containing a variety of text, graphics, and sound. Most Internet Services Providers have Web servers. See HyperText Transfer Protocol, server, World Wide Web. Web Service Provider WSP. A commercial provider of computer network access to the World Wide Web or to a local Web-based network. Most, although not all, Internet Service Providers (ISPs) provide Web access and often include it in their monthly subscription cost. They may or may not provide a diskette with a Web client, called a browser. If not, Web browsers are widely available for download, or through friends, as many of them are freely distributable or shareware. Some service providers use proprietary servers and the user can only use the

browser provided for this service; others allow users to select the browsers of their choice. See Web browser, Web server. Web site On the World Wide Web, which is a mechanism for viewing many portions of the Internet, there are businesses and individuals who have organized data files in such a way as to provide a virtual community, storefront, library, educational resource, or other form of informational/educational/entertainment source for the public or authorized users. When a Web user accesses the site with a computer program called a browser, she or he is presented with various communications media (text, graphics, sound, etc.) available on the site. A Web site is comprised of a series of related files, managed by a client/server Web system that serves the Web files, most of which are called Web pages, to processes that request them over the network. These files typically consist of text and graphics organized into hypertext relational links through a markup language called HTML. There may also be sound, forms, Sun Microsystems Java applets, and various scripts that provide additional functionality to the basic HTML layouts. Web sites are as varied as the people who design them. To mention just a few, there are commercial sites promoting products and services; scheduling sites providing listings of television, radio, and other broadcast venues; weather sites enabling lookup of weather conditions almost anywhere in the world; educational sites through which distance education is becoming more and more available; personal sites journalizing the day-to-day activities of individuals; genealogical sites detailing family histories; and chat sites in which opinions are readily offered and debated. See World Wide Web. Web streaming A capability of a Web browser through addition of a plugin, or which is incorporated directly into more recent browsers, that allows audio or video playback as the data is transmitted to the browser. In older browsers, if the user clicked on a sound or video file, the browser downloaded the sound or video to the local computer from where it was played after the download. More recently, through Web streaming utilities, the audio or video is played as it is received in ‘realtime,’ albeit sometimes at a lower quality level and with variations due to the connection speed to the Internet. A number of commercial plugins and applications are available to take advantage of Web streaming, ranging from $20 to over $3000. A freely distributable version, called RealVideo, is available from Progressive Networks. Web TV See WebTV. Web-Based Enterprise Management WBEM. A distributed management system based on Web technology. WBEM uses a midlevel manager approach, employing HTTP and Web browsers, to provide access to management data and reporting mechanisms. There have been a number of efforts to standardize distributed management, with mixed results so far. WBEM is supported by HMMS, an open standard

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of the Desktop Management Task Force, and the HyperMedia Management Schema (HMMS) under the aegis of the Internet Engineering Task Force (IETF). WBEM provides a means to extend the system through HMMS and utilizes HyperMedia management Protocol (HMMP) to link HMMS to run over HTTP. Weblock colloq. The slowdown that may occur when trying to access extremely popular sites on the World Wide Web. The Web version of a traffic gridlock, where everything temporarily slows to a halt. Webcast, Netcast A broadcast using the World Wide Web as the communications medium. While traditional Web browsing involves clicking on desired pages, text, and images, and thus ‘pulling’ the information to the user, Webcasting involves a method of “pushing” the information at the user in the sense that the user’s screen is continuously updated without the user having to click the screen or manually request an update (like watching television). Since early browsers did not inherently function this way, it was usually necessary for the consumer to first download additional software to his or her computer. Subsequent browsers, such as Netscape Netcaster, directly incorporate the push capabilities and can be used in conjunction with Channel Finder, a directory of Webcasting channels. Webcasting is a significant development. It means the advent of digital TV through a computer, with access to a multitude of “channels” on the Internet. When this catches on, TV will probably never be the same, particularly since very specialized information, such as stock and finance channels, art and music channels, etc. can be made available through the Web without the major sponsorship that is necessary to participate on the big broadcast television networks. HDTV-quality push reception can be accessed with a TV set interfaced with a computer peripheral. See Intercast. WebCrawler One of the significant commercial search engines on the Internet, known for its quick simplicity and very cute little spider mascot. Web Crawler was one of the earlier search engines on the Net. http://www.webcrawler.com/ Webhelp Inc. Enhanced 411 A telephone Directory Assistance service that provides enhanced information services, including movie information, driving instructions, etc. The service is answered by the local carrier, compressed into a digital audio file, routed through a message gateway to an offshore agent who answers the information request. The caller can elect to receive the return information in a number of ways, including hanging up and waiting for a callback or Web-enabled phone message. The company’s goal is to make the world of Web information accessible through the telephone. Webmaster A professional who is responsible for a World Wide Web site. A Webmaster’s duties typically include coding, installation, and maintenance of the site and may also include page layout, content

decisions, and the production of graphics and text. Many individuals have responded to the demand for Webmasters by learning a little bit of layout and HTML and hiring themselves out as professionals, with mixed results. Proper creation, presentation, and maintenance of a good site, especially a commercially viable site, involve a large number of professional skills including marketing knowhow; writing, editing and proofreading; graphics design and production; Web statistics monitoring, analysis, and reporting. Choose your Webmaster carefully. In fact, you may do best to team up a user-interface and CGIsavvy programmer with a market-savvy artist and writer. HTML skills alone are not sufficient to create good database, point-of-purchase, or shopping cart software, and these may be essential to a business presence on the Web. WebNFS Web Network File System. A proposed specification for a client/server protocol as an extension to recent versions of the Network File System (NFS). NFS is an RPC-based, platform/transport independent protocol and WebNFS is intended to provide semantic extensions to NFS. It helps make file handles faster and easier to obtain, and may improve transit of firewalls and system scalability. WebNFS clients assume the availability of a WebNFS server registered on port 2049. See Network File System, RFC 1094, RFC 2054, RFC 2055. Website Meta Language WML. An extensible, freely distributed offline HTML-generation toolkit for use by Web designers creating Web sites on Unix systems. WML is written in ANSI C and Perl 5. It is distributed under the GNU General Public License (GPLv2) and may be used free of charge in educational and commercial environments. Webspace Derived from cyberspace, Webspace refers to the Web environment, the sum total of the hardware, software, people, transmissions, and interactions that comprises the World Wide Web community. WebTV A simple consumer-oriented Web access device that uses a TV as the display. It was purchased in August 1997 from the California-based WebTV company by Microsoft Corporation. Sony Electronics, Philips Consumer Electronics, and others have products based on the WebTV technology. Webzine An electronic publication available on the Web, either free or through subscription. Webzines may be pure electronic publications or may be electronic versions of printed publications, with or without enhancements possible on the Web. Many of the major publications are providing back issues of print publications as Webzines in order to attract readers to both the print and Web versions. With electronic access increasing and trees declining, this type of publishing may, in time, supersede many print publications. Currently, it is difficult for small Webzines to be profitable. There is so much free content on the Web, people are reluctant to pay, and there are as yet no really easy pay systems for handling very small electronic transactions; though this situation could dramatically change. See e-zine.

WECO See Western Electric Company. Wehnelt interrupter A type of early electronic apparatus used in laboratories to provide interruptions ranging from 100 to 1000 per second. The positive side of a circuit was connected to a platinum electrode conducting through a well-insulated primary winding coil. This, in turn, was connected to a lead plate in a dilute solution of sulphuric acid. A tube for circulating water was included to provide cooling. WELL, The The Whole Earth ‘Lectronic Link. This Web site is somewhat like a bohemian meeting ground for intellectuals and artists. Established in 1985 by Stewart Brand and Larry Brilliant, the WELL’s discussion community patrons include many artists, educators, writers, and high-level technical professionals. http://www.well.com/ West Coast Computer Faire A historic meeting place for computer hobbyists, many of them pioneers in the microcomputer field. Established in 1978 by Jim Warren, it was then the largest computer show in the world. West Ford satellites A set of satellites launched by the United States beginning in 1961. The pioneering West Ford project launched surfaces into orbit that contained millions of slender copper dipoles to provide a reflective “blanket” around Earth. The first launch attempt was unsuccessful due to a failed ejection, but the second launch, in 1963, demonstrated that communication could be achieved, at least with high-powered ground stations. At that time, concerns were expressed over side effects from certain types of satellites and space debris, and since the feasibility of active relays was successfully demonstrated, the project was discontinued. See ECHO satellites. WESTAR The name of a family of Western Union communications satellites, WESTAR I was the first U.S. domestic communications satellite, launched in 1972. A WESTAR satellite was launched with the Challenger space shuttle mission in February 1984. Unfortunately, the Payload Assist Modules (PAMs) didn’t function correctly; the WESTAR was launched into a lower orbit than had been planned, and it had to be retrieved by the shuttle Discovery some months later. Western Electric Company WECO. Originally established as the Gray & Barton company in 1869 by Elisha Gray and Enos Barton. In 1872 it became known as Western Electric Company and, in thirty years, grew to be one of the world’s largest manufacturers. The Graybar Electric Company, Inc. was spun off from WECO in 1925 and is still doing business as an employee-owned distributor of telecommunications products. In 1881, Western Electric Manufacturing Company became Western Electric and acquired exclusive rights to manufacture and provide Bell Equipment. In 1915, Western Electric took over Western Electric Company of Illinois and, in 1925, Western Electric Research laboratories were consolidated with part of AT&T’s engineering department to form Bell Telephone Laboratories, Inc.

See Gray, Elisha; Gray & Barton; telephone history. Western Union, Western Union Telegraph Company Western Union was originally organized as the New York and Mississippi Valley Printing Telegraph Company in 1851 by Hiram Sibley, and named Western Union Telegraph Company in 1956 by his business associate Ezra Cornell (cofounder of Cornell University), when it merged with Cornell’s New York & Western Union Telegraph Company. Cornell was the largest shareholder for over fifteen years. Western Union installed the first North American transcontinental line in 1861. Sibley traveled to Russia and was offered an opportunity to purchase Alaska on behalf of Western Union, but turned it down, passing on the information and the historic opportunity to the U.S. Government. In 1868, Western Union hired C. F. Varley to evaluate the U.S. telegraph system with the result that he introduced many standards for coordinating the various lines and systems. Western Union acquired the rights to new technology, called duplex telegraphy, in the early 1870s. This enabled two messages to be sent concurrently, one in each direction, over the same wire. In 1873, Western Union entered the international market by a takeover of the International Ocean Telegraph Company. In 1877, Western Union went into competition with the Bell system, acquiring patents or licensing rights from Edison, Gray, and others, and forming the American Speaking Telephone Company. As Western Union had thousands of miles of telegraph cable strung across the country, this posed a very real challenge to the Bell system, and they reacted with a patent infringement lawsuit that was upheld two years later in the Supreme Court. Western Union had a short alliance with the Bell system from 1908, when AT&T gained control of the company, to 1913, when it voluntarily sold it off again to forestall government breakup of the company. In 1943, the Postal Telegraph Company, founded in 1881, was merged into Western Union. In 1950, Samuel Morse’s original telegraph instrument was presented by Western Union to the Smithsonian Institution. Other versions of the Morse telegraph are replicas. In 1970, Western Union acquired TWX (from AT&T) and merged it with its own Telex system. Western Union International was acquired by MCI International in 1982. In the mid-1980s, the world was changing rapidly. Communication through the Internet was catching on, overnight couriers were in heavy competition with the telegraph industry, and divestiture changed the competitive atmosphere of the phone industry. As a result of this and other changes, the 138-year reign of the Western Union Telegraph Company came to an end in 1989. See Western Union Telegraph Company Collection. Western Union Telegraph Company Collection This extensive historical collection was presented by

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the Western Union Telegraph Company to the National Museum of American History as a gift in 1971. It consists primarily of manuscripts, telegraphs, and photographs previously housed in the Western Union Museum. A tremendous amount of telegraph history is contained in these archives. See Western Union. Western Union Telegraph Museum A historic repository of Western Union documents and photographs established in 1912 by in-house engineer H. W. Drake. By 1930, the collection had its own room at Western Union and historical instruments were being added until the late 1960s, when the materials were warehoused. In 1971, the collection was transferred to the National Museum of American History, then called the National Museum of History and Technology. See Western Union.

The Westinghouse Electric Plant radio assembly line in Hamilton, Ontario, March 1947. [National Archives of Canada National Film Board collection, photo by Bud Glunz]

Assembly workers putting together radios at the Westinghouse Electrical Plant in 1947. [National Archives of Canada National Film Board collection, photo by Bud Glunz.]

Westinghouse, George (1846-1914) An American inventor who pioneered many aspects of alternating current (AC) power, generators, and the railway air brake (1868). He also made practical applications

from ideas derived from or shared with Nikola Tesla, and had more than one disagreement with Thomas Edison. His light and power system was used in the 1893 Chicago World’s Fair, the same year he won the historic contract to develop alternating hydroelectric current from the Niagara Falls. WestNet One of several National Science Foundation funded regional TCP/IP networks, WestNet is located in Salt Lake City and serves the states of Arizona, Colorado, New Mexico, Utah, and Wyoming. wet cell A basic electricity-providing apparatus employing a positive and negative terminal, each separately in contact with a liquid electrolyte medium (battery acid is an electrolyte). Wet cells are inconvenient in that the electrolyte tends to evaporate and may spill, so other types of cells have been devised, chief among these, the dry cell, available since the early 1900s. A type of wet cell called an air cell became widely used in phone applications. See air cell, Bunsen cell, dry cell. wetting Adhering a uniform, smooth film of solder to a surface, usually a base metal. wetting agent 1. A substance which, when applied to a surface, prevents it from repelling wetting liquids to enhance the adhesion of liquids to the surface. 2. An agent that facilitates the smooth, even spread of liquid over a surface. WFS See Woodstock File Server. WFWG Windows For Workgroups. See Windows. WGDTB Working Group on Digital Television Broadcasting. WGIH Working Group on Information Highway. A working group of the TSACC. WGS World Geodetic System. A very extensive geologic data set, updated every decade or so to take advantage of improved data that can be acquired with improved technologies. Wheatstone, Charles (1802-1875) An English physicist who researched acoustics and invented the concertina. He also experimented with electromagnetic and solar clocks, and developed a speaking machine based on earlier work by W. Kempelen. Like Samuel Morse, he received encouragement and assistance from Joseph Henry, and invented a telegraph that predates the one designed by Morse. In collaboration with W. F. Cooke, Wheatstone’s telegraph was operating in 1837 and he may have received information and assistance from an earlier telegraph inventor, Francis Ronalds. In 1840, Wheatstone proposed an underwater cable between England and France. The Wheatstone bridge that bears his name was developed by Samuel Christie and described by Wheatstone in 1843. See Cooke, William Fothergill; polar keying; Ronalds, Francis; telegraph, needle. Wheatstone bridge, resistance bridge A device employing a galvanometer and a group of interconnected resistors for measuring resistance against a comparative standard. This tool can be used for determining faults in a length of wire, so the entire wire doesn’t have to be dug up or pulled out. By

creating a balanced bridge through various loop tests, the approximate location of the fault point can be determined. The Wheatstone bridge was developed by Samuel Christie. It is named after Charles Wheatstone because he described it in print in 1843 and often mentioned it in his lectures. See megger. Wheler, Granville An English experimenter who collaborated with Stephen Gray in discovering conductors and nonconductors, and demonstrated in the late 1720s that an electrical charge could be conducted through a thread of more than 600 feet in length. In fact, it was found it could be conducted simultaneously over multiple threads. See Gray, Stephen. Whetstone When microprocessors were slow and rudimentary in design, and operating systems and software applications were limited, it was easier to run a few tests to evaluate and compare the relative speeds of various systems. Thus, a number of benchmark tests were devised to measure performance. The Whetstone test was developed in the 1970s by B. Wichmann with an Algol 60 compiler. It is named after the English town where it originated. The Whetstone monitored the number of floating point operations that could be carried out by a process in one second. Floating point operations (flops) are common in processor-intensive computing applications such as graphics and scientific work. See benchmark, Dhrystone, Rhealstone. Whirlwind A historic, large-scale computing machine developed at MIT in the late 1940s and early 1950s. It is credited as being the first realtime-processing digital computer. It is also significant for incorporating random access memory in a matrix core memory. White Alice Communications System WACS. A historic communications system installed by AT&T and Western Electric. About two dozen of the stations were installed across the state of Alaska, with the White Alice station located on Pillar Mountain in Kodiak. WACS operated from the mid 1950s until 1979 and was dismantled in 1997. It went through a number of hands during its history, including the U.S. Army and RCA. The system used 5-story-high curved rectangular vertical dishes supported with billboard-style scaffolding. Stations intercommunicated through tropospheric scattering White Book 1. Any book in the set of 1992 ITU-T recommendations. 2. A document that specifies MPEG video and audio file structure, coding, and indexing. Up to 74 minutes of full-motion video can be recorded on a disc. White Book discs can be played on standalone video CD and DVD players and on suitably equipped computer systems. The format was introduced in the early 1990s by JVC, Philips, and other major vendors. See MPEG, Red Book. white noise Human-audible signals that consist of a spectrum of frequencies more-or-less evenly distributed across the range so that no one tone predominates, as in background noise. White noise is sometimes used to create ambience in sound systems and it is used in audio experiments. white pages 1. In most English-speaking countries,

the directory portion of residential, or residential and business listings, in the local telephone directory. 2. On the Internet, directories of individuals’ physical and electronic addresses usually accessible to the public through the World Wide Web. Web white pages can be searched through keywords and are more flexible and powerful than standard printed phone listings. You don’t have to be using the Internet to be listed in these directories; many are compiled from telephone listings and other public sources of information. See ego surfing, yellow pages. white paper Colloq. A technical document, usually describing research, experimental results, or details of a technology. White papers and Request for Comments documents are two of the primary communications venues used by developers of communications technologies to present and disseminate information about their theories, inventions, and operational observations. White Paper The popular name for a paper titled A Statement of Policy on the Management of Internet Names and Addresses that was issued by the U.S. Department of Commerce’s National Telecommunications and Information Administration (NTIA) in June 1998. This document supported a prior Green Paper call for the establishment of a not-for-profit entity to coordinate Internet domain name administration. This was an important step in the direction of privatizing the domain name registration system while still acknowledging the rights of national governments to coordinate their own country code TLDs. This led to the formation of the Internet Corporation for Assigned Names and Numbers (ICANN). See Green Paper, top level domain. white room, clean room A controlled environment in which dust, smoke, bacteria, and moisture are eliminated or regulated in order to reduce interference with and contamination of the functioning of the environment. Controlled environments are used in component production, research labs, medical facilities, etc. white transmission 1. In an amplitude-modulated transmission of an image, a black transmission means that the greatest divergence in amplitude in the signal represents the black tones, and the narrowest divergence represents the lightest tones (or no tone at all). In white transmission, the opposite is true. 2. In a frequency-modulated transmission, a black transmission means that the lowest frequency corresponds to black and the highest frequency corresponds to white, or no tone, and in a white transmission the opposite relationship is used. The concept applies to image scanners, facsimile machines, photocopiers, etc. whiteboarding Communicating through means of text and graphics drawn on an erasable wall board or large sheets of paper. See whiteboarding, electronic. whiteboarding, electronic 1. An electronic software application in which input from various keyboards and pointers is displayed or projected on a large white screen that resembles an erasable whiteboard. 2. A dedicated computer network display system that

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enables remote two-way communication of ideas through text and graphics. 3. The conceptual analog of a whiteboard communication, carried over a computer-based videoconferencing system. The author first saw this demonstrated by SGI with a videoconferenced paint program at a trade show around 1991, in which both participants, in different locations, contributed to the same illustration and text while another window simultaneously showed their faces as they talked to one another. As it was demonstrated, the whiteboarding concept was very broad and could conceivably include collaborative use of any type of software application by two or more participants. This is a powerful concept that goes several steps beyond mere conversation on a videoconferencing system and shows great promise. See audiographics, telecommuting, videoconferencing, whiteboarding. Whittaker, Edmund Taylor (1873-1956) A British mathematician and professor, Whittaker made important contributions to mathematical theory and the instruction of mathematics. Whittaker served as the secretary of the Royal Astronomical Society from 1901 to 1906. In 1905 he was elected as a Fellow of the London Royal Society and, in 1906, he became the Astronomer Royal for Ireland and accepted a position as an astronomy professor at the University of Dublin. In 1912 he moved to Edinburgh and worked as a professor there until 1946. Whittaker is known for his work in numerical analysis and applied mathematics as it relates to astronomy. In the context of communications, Whittaker developed a mathematical framework for later sampling theories that led to the implementation of pulse code modulation in digital recording. The Sir Edmund Whittaker Memorial Prize is awarded for published works of high merit in mathematics or mathematical physics. See pulse code modulation, sampling theory. whois An Internet username directory service application that responds to a name query by accessing a central database and returning a listing of users found to match the name or a portion of the name. Whois is based on the WhoIs Protocol (NICNAME) which is an elective proposed Draft Standard of the IETF. See finger, rwhois, RFC 812, RFC 954. wicking The process of drawing a liquid out of a substance or along a path. Wicking occurs when solder runs along a wire or up underneath an insulating sheath. Diapers and hiking socks are designed to wick moisture away from the skin to prevent irritation. Oil lamps draw oil up through the wick as they burn. Wide Area Augmentation System LAAS. A Global Positioning System (GPS) augmentation system intended to provide safer, more reliable satellitebased navigation services for aviation. WAAS provides geographically expansive en route and nonprecision approach navigation data which is further used in conjunction with the more precise Local Area Augmentation System (LAAS) in specific locations. WAAS meets Category I aviation

requirements and encompasses most of North America through approximately 25 ground reference stations. Information is broadcast through GPS frequencies (1575.42 MHz) to onboard aircraft receivers, improving GPS accuracy to about 7 meters. Further details are available through the Federal Aviation Administration (FAA). See Local Area Augmentation System. http://gps.faa.gov/ wide area differential GPS WDGPS. An implementation of the Global Positioning System (GPS) that includes a network of reference stations that act as data collection sites to receive and preprocess GPS satellite signals. The information is forwarded to a central processing hub that creates correction vectors for each satellite, including clock corrections. WDGPS systems can provide more accurate local positioning information for a variety of industries, including surveying and navigation, particularly aviation, where precise positioning for takeoffs and landings is important. See differential GPS, local differential GPS, Global Positioning Service. Wide Area Information Server WAIS. Developed in the early 1990s by Brewster Kahle, WAIS is a powerful search and retrieval system widely used on databases on the Internet. The WAIS URL scheme designates WAIS databases, searches, and individual documents available from a WAIS database. WAIS can be accessed on the Web through the following URL schemes: WAIS database wais://:<port>/

Specific WAIS search wais://:<port>/?<search>

Specific WAIS document wais://:<port>//<wtype>/<wpath>

There are freely distributable and commercial versions of WAIS available. With the burgeoning information on the Net, WAIS is a tool of some significance. See RFC 1625. Wide Area Information Server gateway WAIS gateway. A computer used as a “go-between” between incompatible networks or applications to translate WAIS data. wide area network WAN. Unlike LANs, which tend to be directly cabled and thus limited in scope, Wide Area Networks can connect users over broad geographical regions through the use of long-distance transmission technologies, such as telephone and satellite services. WANs are often used to connect LANs with a variety of architectures and protocols. A WAN accomplishes the transmission of various formats through routers or, alternately, through bridges, that are protocol independent in order to connect WANs and LANs. See bridge, Local Area Network, router. Wide Area Network Management Center WANMC. There are a number of centers in different organizations operating under this general department title. This is a central facility that administrates,

configures, and operates various aspects of wide area networks (WANs) depending upon the needs of the firm and the degree of centralization. Wide Area Telephone Services See WATS. wide band channel WBC. In FDDI-II isochronous networks, WBC is the circuit-switching capability. Any bandwidth not allocated to WBCs can be used for other data, such as statistical information about data traffic. See Fiber Distributed Data Interface. wide characters Character codes consisting of two bytes (16 bits), rather than the traditional one byte (8 bits), in order to accommodate a much larger number of characters from different languages. See Unicode. wide open receiver A receiver that is receiving a range of frequencies simultaneously. CB radios and various emergency systems are sometimes set to receive a range of transmissions at one time. wideband 1. A band wider than that which is necessary for transmitting voice, sometimes called medium-capacity band, in the 64-Kbps to 1.5-Mbps range. 2. A range between narrowband and broadband, typically between about 1.5 Mbps and 45 Mbps. 3. A band with a broad range of frequencies, often multiplexed. See broadband, narrowband. wideband digital cross-connect system W-DCS. A digital cross-connect system that accepts a variety of optical signals and is used to terminate SONET and DS-3 signals. In other systems, it may also crossconnect DS-3/DS-1. W-DCS can be used as a network management mechanism. Switching is carried out at the VT level. See broadband digital cross-connect system. wideband modem A modem designed with a bandwidth (frequency spectrum) capability greater than that of common consumer modems designed to work over basic voice channels. widescreen TV A home theater TV set that supports and can display a video transmission with a 16:9 horizontal to vertical picture ratio, as is found in movie theatres. These are the same proportions supported by letter-boxed laserdiscs and videos, those in which none of the original movie imagery is cut off of the sides when it is displayed. The 16:9 ratio is also supported by some of the better consumer camcorders. Widrow, Bernard An American electrical engineer, professor, and pioneer in the field of adaptive signal processing, systems that learn and adapt their behavior through interactions with their environments. Adaptive signal processing relates to neural networks and has practical applications in high speed networking over traditional wirelines, for example. Widrow was a historical early contributor to the theory of adaptive antennas. He coauthored “Adaptive switching circuits” in 1960. He was awarded the IEEE Alexander Graham Bell Medal in 1986, the IEEE Neural Networks Pioneer Medal in 1991, and the Benjamin Franklin Medal in Electrical Engineering in 2001. Wiener, Norbert (1894-1964) An American mathematician who collaborated with Arturo Rosenblueth and a group of scientists from various disciplines in

developing many fundamental concepts of artificial intelligence. He authored Cybernetics: or, Control and Communication in the Animal and the Machine in 1948 and updated it in 1961 to include ideas about self-reproducing machines and self-organizing systems. He also contributed to the fields of stochastic processes and quantum theory. See neural network. WIG Wireless Interoperability Group. See WAP Forum. wild virus See virus, wild. wildcard A symbol which takes the place of and represents a series of characters, or an unknown quantity or any quantity, usually in a numeric or alphanumeric context. For example, the asterisk (*) is a wildcard character frequently used in computing applications, especially file management, for representing unknown characters or any characters. Thus, the UNIX shell command rm myfile.* would remove any filename in the current directory beginning with “myfile.” and ending in any extension (or no extension). WildList Organization International WOI. An authoritative industry inventory of viruses that are a considered to be a threat to computers in general use, i.e., those “in the wild.” To put it another way, it lists viruses that spread as a result of normal computer use by a wide general audience, as opposed to those that are developed, tested, and used in labs. Like so many aspects of the computer industry, the WildList started as a freely distributable list developed by Joe Wells in his garage and has grown, with the help of volunteers, to be an important resource for research and testing of antivirus software. See virus. http://www.wildlist.org/ WiLL See wireless local loop listing Williams-Kilburn tube A historic cathode-ray tubebased system used to store information electronically for use with computing machines. The system was developed near the end of World War II by F. Williams and T. Kilburn who were associated with the Telecommunications Research Establishment (TRE) in Malvern. The cathode-ray beam was used to display dots and dashes on the surface of the tube representing the binary values. Unlike modern cathoderay tubes with streamlined housings, the WilliamsKilburn tube (also known as the Williams tube) had a boxy industrial look, like a large metal toilet paper roll with a display surface at one end under which were a few small button-shaped dials. The Williams-Kilburn tube became an important component in the subsequent design of the Small Scale Experimental Machine, a historic computer with randomly accessible program instructions and data stored in “tube memory.” It was also incorporated into the later IBM 701. See Small Scale Experimental Machine. Willis Graham Act of 1921 An act that not only recognized AT&T’s monopoly in the phone industry, but legitimized it as well. However, 28 years later, the U.S. federal government filed antitrust proceedings against both AT&T and Western Electric. This long process was not settled until 1956 with a consent decree. See Modified Final Judgment.

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WIM WAP Identity Module. See WAP Forum, Wireless Application Protocol. WIN See Wireless Intelligent Network. Win-OS/2 Microsoft and International Business Machines (IBM) were originally collaborating on an operating system for IBM’s microcomputers which IBM released as OS/2, but at some point during the project, Microsoft stepped back and began concentrating on developing their own Windows products. The windowing component of OS/2 and a number of the basic concepts were incorporated into Microsoft’s Windows product line. WIN95 See Windows 95. Winchester disk A random access hard disk drive marketed in 1980 by Shugart Associates, founded by Alan Shugart, formerly of International Business Machines (IBM). Considering that computer users were predominantly using cassette and reel-to-reel tapes to sequentially write and read data up until this time, the hard disk drive was an important improvement as a computer peripheral and is still one of the foremost storage media. winding n. 1. A conductive path, coupled inductively to a magnetic core or cell, usually made of metal wire. Helical coil windings are used in simple armatures, inductors, and transformers. 2. A structure to enhance the transmitting or receiving of electromagnetic waves. A type of compact antenna

1

2

mechanism. Various types of windings can be found around small spool-like cores in old radio sets. These were used for frequency selection, employing different thicknesses of wire and winding patterns. Depending upon the purpose of the winding, the wire may be left open or may be sealed in paraffin, rubber, or some other protective material. Winding can be somewhat tedious and exacting. For this reason, windings are sometimes done in sections and winding machines may be used to create the coil. Since the amount of wire that is wound is sometimes critical, the spool on which the wire is wound may be weighed before and after the winding, to check that the desired amount has been used. Boiling the coil in linseed oil was one of the techniques used in early fabrication to drive out moisture and provide a tight insulating layer. Paraffin and rubber were sometimes also used. See basket winding, coil. winding machine Any machine improvised or designed to facilitate wire windings around various cores for the creation of armatures, antennas, frequency tuners, spark coils, and other apparatus that utilize wire windings. Evenly wrapped, tight windings are important in many electronic applications and tedious to wind by hand. Thus, a spinning bobbin, lathe, or specialized winding machine is now typically used to increase speed and precision.

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Three types of armature windings are shown here: (1) evolute-wound, (2) barrel-wound, and (3) bastard-wound (a variation on barrel-wound is also shown bottom right). [Cyclopeda of Applied Electricity, 1908.]

This schematic shows one type of ring armature, a wave-wound armature connected in series. The spacing of the wire windings is called ‘pitch.’ [Cyclopeda of Applied Electricity, Chicago American School of Correspondence, 1908.]

This is the armature from a Westinghouse generator. It is a bastard barrel winding, a type of winding whose end connections are inward and cylindrical, thus shortening the length of the armature parallel to the shaft compared with barrel winding.

Historic Basic Armature Winding Types Type

Characteristics

ring

The two common types are spiral wound (single closed helix) and series-connected wave-wound (see the preceding diagram).

drum

The two common types are lap and wave, which are similar on bipolar machines, but different on multipolar machines.

wave

The winding passes along the conductor to the back of the armature once through each conductor.

multiplex Two or more independent windings on a single armature. These are more commonly used on generators intended to supply large currents with small voltages.

window 1. An opening, entrance, time interval, or opportunity. 2. An opening or transparent material that permits light to penetrate, or permits a viewer to see beyond the structure in which the window is installed. 3. A graphical user interface structure developed at Xerox PARC in the 1970s and incorporated into the Alto computer. It first came into widespread use on Macintosh computers in 1984 (it was used also on the Apple Lisa in 1983, but the Lisa never caught on). It contains a group of related information or functions. Most computer interfaces now use similar conventions for sizing, scrolling, opening, closing, and iconizing a window. See graphical user interface. 4. In networking, an opportunity, space, or transmissions lull during which information can be sent, processed, or otherwise efficiently handled. System tuning, capacity monitoring, and flow control are all ways of taking advantage of windows. windowing A description for a means of organizing and interacting with graphical user interface (GUI) structures called windows. A window is essentially a portal into a portion of the computer’s data, visually represented within a bounded entity that can usually be moved around, sized, iconized, or placed in priority overlapping with other windows. There are text windows, graphics windows, sound “windows,” and others. When they are moved about a computer screen in order to make them comprehensible and easily accessible, popped to the front, or pushed to the back to bring a relevant window to the front, it’s called windowing. Windows A Microsoft Corporation graphical operating environment that works in conjunction with Microsoft’s text-oriented MS-DOS (Microsoft Disk Operating System), primarily on Intel platforms, although a number of Windows emulators for other

systems are available and recent versions exist for handheld devices. Windows is descended from user interface concepts developed in the 1970s at the Xerox PARC research lab that were first widely incorporated into microcomputers by Apple Computers, Inc. in the early 1980s. Apple shipped the Lisa computer with a graphical user interface in 1983, shortly before the announcement of Windows 1.0, which didn’t actually ship until late in 1985. Current versions of Microsoft Windows use essentially the same basic concepts as their Xerox-inspired predecessors, including icon and gadget point-and-click interaction, sizable windows, visually accessed directory structures, and window overlap priority for the active window. The following Windows-related entries describe some of the history and development of the various versions in more detail. Windows - early versions Originally called Interface Manager, the first version of Windows was developed between 1981 and 1985. Windows 1.0 was officially announced in 1983, not long after the release of Apple’s Lisa computer, although it was not commercially distributed until two years later, beginning late in 1985, around the same time the Atari ST and Amiga 1000 shipped with full graphical user interfaces (followed by the Apple IIGS). While these competitors never unseated MS-DOS/Windows as the prevalent operating system, they did give consumers and developers food for comparison and many of the ideas pioneered on the competitive machines were incorporated into later versions of Windows. In addition, the distribution of the Amiga in 1985 provoked a storm of discussion about whether operating systems should be multitasking. Despite the controversy, other platforms gradually began adapting task-switching as an early step toward multitasking. Thus, in 1987, when Microsoft released Windows 2.0, it incorporated some of these ideas, including the capability to open more than one application at a time and to overlap windows. Graphical elements were not yet significant, as on the Macintosh, Amiga, or Atari operating systems. Windows 2.0 was renamed Windows/286 when Windows/386 was released later the same year. The early versions Windows were limited to 640 Kbytes of address space and “16-color” palettes (which were actually eight colors plus the same eight displayed at half intensity). Windows 3.0/3.1 Windows was greatly enhanced and overhauled between 1987 and 1990 to provide an improved user interface, the capability to support more than 16 colors (8 + 8 at half intensity), and memory addressing beyond 640 Kbytes. The result was released as Windows 3.0. Two years later, in 1992, Windows 3.1 shipped with significant enhancements over 3.0, with scalable fonts, object linking and embedding, and better multimedia capabilities (Multimedia Windows was absorbed into this product). Windows 3.1 became a widely distributed version of the Microsoft graphical user operating environment, popular in the mid-1990s.

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Windows 3.11 was released as a free upgrade in 1994 to correct some of the networking functions of Windows 3.1. Windows 3.1 has, for the most part, been superseded by Windows 95, 98, 2000, and ME, although a sizeable number of corporations continued using it for many years after the release of Windows 95. Windows for Pen Computing 3.1 Although not well known, this version of Windows, specifically designed for pen computers requiring handwriting recognition for the execution of commands, shipped in the spring of 1992. Windows for Workgroups 3.1 This version of Windows, designed for integrated networking and sharing of resources, shipped in 1992, the same year as Windows 3.1. It should be noted that the Macintosh operating system provided file sharing network support off-the-shelf eight years earlier, so Workgroups was not a forerunner in microcomputer networking, but it was a welcome enhancement to corporate users running Windows systems and included network mail capabilities. Windows for Workgroups 3.11 was enhanced with a number of features, the most important being the addition of 32-bit file access. Windows 95 Windows 95 was the highly promoted successor to Windows 3.1 and, to some extent, also succeeded Windows for Workgroups. Windows 95 first shipped in the summer of 1995. It did not have the robustness, multiprocessor support, or security features of Windows NT, but it was less expensive, and thus became a popular consumer and small business alternative to the more powerful Windows NT operating system. Windows 95 differed from earlier versions in three important ways. It relegated DOS to secondary status, incorporated multitasking, and fully implemented graphics icons and menus. Thus, it followed the example of the Lisa and Macintosh line of computers (1983) and the Amiga and Atari computers (1985) in embracing the graphical interface ideas pioneered by Xerox PARC researchers in the 1970s. All major desktop computers now had graphical interfaces and most of them have multitasking or, at least, task-switching operating systems. Windows 95 was a strong commercial success and was still being used on many systems six years after its release. Windows 98 The successor to Windows 95, released in June 1998. This version was significant in that it was the first to directly incorporate network browsing into its structure, an important trend and step toward integration with the Internet. The Net was growing as an important economic and communications force at the time 98 was released and Microsoft was seeking ways to facilitate Internet access through its operating system. Windows 98 shipped with Internet Explorer, one of the popular Web browsers competing with Netscape Navigator and OmniWeb. This integration of OS and browser software was a point of contention with other software manufacturers, as it was felt that this could lead to a stifling of competition through

monopolistic practices. While Microsoft continued to ship Windows 98, the Justice Department investigated various allegations against the company, proceedings that continued for several years while Windows came out in new versions. The controversy became even more heated in 2002 when AOL/ Time-Warner, who had acquired Netscape, challenged Microsoft’s continued efforts to incorporate Internet Explorer into its OS. Windows NT Windows New Technology. A 32-bit multitasking, multithreaded, networking operating system first released in 1993, Windows NT shares many basic features and user interface concepts with Windows 95, but it is more polished, more reliable, more secure, and includes symmetric multiprocessor support. Bill Gates has publicly stated that Windows NT originated as “OS/2 3.0,” with development work beginning in 1987 based upon the IBM/Microsoft collaboration to develop OS/2, with D. Cutler heading the evolution into Windows NT since 1989. Windows NT is favored in development environments, server applications, and corporate networks. Windows NT was designed to run on processors other than just the Intel chips, providing portability to other platforms not well supported by earlier versions of Windows, except in the form of thirdparty emulators. It was offered in workstation and server versions. Windows NT Advanced Server NTAS. An extended version of Windows NT specifically aimed at server applications. Windows CE Released in 1996, CE was aimed at the growing numbers of handheld computing devices and had a look and feel similar to the desktop Windows systems. Version 3 was released in 2000 along with applications development tools for programmers to build embedded device applications. Windows 2000 Released early in 2000, this product was in many ways a bridge between Windows 98 and Windows NT. Support for small business networks, encryption, Internet access, and the many other features that users were now demanding were being incorporated into Microsoft operating systems by this time. Windows ME Windows Millenium Edition, released fall 2000. Windows ME was aimed as an economical option for home users. It includes some of the multimedia capabilities that were becoming popular and stronger support for Internet accessibility. It is essentially an upgrade to previous consumer versions of Windows and is not directly competitive with the more powerful Windows NT line. Windows Application Binary Interface WABI. Windows Application Binary Interface. Software from Sun Microsystems that enables Microsoft Windows applications to run on the Solaris desktop system. Thus users can have access to the large library of software available for the Windows operating environment and can run them, along with Solaris applications, on computers installed with Solaris. Windows Application Binary Interface server WABIserver. A Microsoft Windows application

server providing integrated Windows/Solaris options to SPARCstation users running Sun Microsystems’ Solaris, Solaris Intel, or an X terminal system. Windows Internet Name Service WINS. A name resolution client/server application that resolves the internal names applied to networked Windows computers to corresponding Internet Protocol (IP) addresses. Windows Open Services Architecture WOSA. A Microsoft Corporation distributed, semi-open, client/ server-based architecture first announced in 1992. WOSA is built on a three-level model consisting of service providers, applications programming interfaces for each category of services, and the applications themselves. While the service provider interface (SPI) level is essentially open, the applications programming interfaces (APIs) and service provider interfaces (SPIs) are proprietary to Microsoft. There are a variety of WOSA elements including: Type

Notes

Messaging API (MAPI) Provides electronic messaging access, including a variety of services such as voice mail, electronic mail, facsimile transmissions, etc. Address databases are supported by Extended MAPI. Speech API (SAPI) Provides a means for a speech engine to run on a Windows client or server, thus enabling a telephony application, for example, to utilize speech capabilities. Telephony API (TAPI) Telephony support for Windows NT systems to enable use of voice, data, and video over existing networks. The API provides generic means for connecting between multiple machines and accessing media streams being transmitted among them. TAPI supports standards-based H.323 conferencing and IP multicast conferencing.

The Open Group Architectural Framework (TOGAF) has information and opinions on WOSA and WOSA-related open architectures at the following Web site: http://www.opengroup.org/public/arch/wosa.htm WINF See Wireless Information Networks Forum, Inc. wink In telephony, a handshaking signal indicating the transition between on-hook and off-hook states. A wink signal can indicate that the central office is ready to receive the dialed number. A wink is a fairly generic type of signal that can be used in many contexts and can be created in a number of ways, depending upon the type of communications protocol and whether the line is analog or digital. In an analog system, the wink can be indicated by a change

or interruption in tone or a change in polarity. On a digital line, a wink may be indicated with signaling bits. WINS See Windows Internet Name Service. Winsock Windows sockets. Winsock provides a standardized applications programming interface (API) for Windows- and OS/2-equipped computers to interact with the Internet. It originated at an Interop conference discussion group in 1991. Winsock 2 is a further development effort of the Winsock Standard Group. In addition to the capabilities of the original version, Winsock 2 incorporates multiprotocol and multicast capabilities, quality of service (QoS), and a layered provider architecture. Microsoft’s Windows Open Services Architecture (WOSA) incorporates Winsock into its APIs. Winsocks were designed on the same concepts as UNIX-based Berkeley sockets, with extensions to accommodate Windows-specific functions; programming them is somewhat similar to programming Berkeley sockets. Winsock functions by means of a dynamic link library file called winsock.dll that comes in 16-bit and 32-bit versions, and is loaded into memory. The .dll file format is compatible with Windows 3.x and newer versions. Winsock 32-bit drivers are included with Windows 95 and Windows NT. There are also variations in the .dll files to provide compatibility with various TCP/IP stacks. In a sense, the .dll provides a communications layer between the TCP/IP stack and the Winsock applications programs developed to communicate through the sockets. Winsock Standard Group An organization of network software developers and vendors, established in the fall of 1991 that meets several times a year to enhance, refine, and extend the Winsock specifications. Winsock 2 specifications were developed and published by this group. Wintel systems Windows and Intel. A term that refers to Intel hardware-based computers running Microsoft Windows operating software. WIP See Women Inventors Project. WIPO See World Intellectual Property Organization. Wire Center A physical facility of a telecommunications provider, to which outside subscriber lines lead. wire concentrator Any wire path or conduit that serves to bring together a number of wires running roughly through the same installation path. wire pair Two separate conductors following the same transmissions path in close proximity to one another. It is called twisted pair when the wires are twisted around one another in order to reduce noise. Copper twisted-pair wire is very common in the telephone industry. wire speed The raw speed at which data bits are transmitted over wire. This is not the same as the amount of information that can be transmitted. Various factors will hinder the transmission when all the devices and wires are interconnected, including noise, interference, connection devices, etc. Conversely, a variety of compression and multiplexing

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techniques can be applied to the data to increase the informational-carrying capacity of a wire. wire stripper A tool that quickly removes the protective sheath from wires so they can be easily attached to mounting posts or to one another to make good electrical contact. Punchdown tools for installing telephone line often include a wire stripping blade. wire tap See wiretap. wireless A system that performs a function, or transmits information fully or predominantly, without wires. An older term for a radio set, since radio signals were intercepted as waves. Now the term is used more broadly for telecommunications technologies that work without wires, including cellular phones, intercoms, and video security systems that work over FM frequencies. WIRELESS The largest annual wireless industry trade show, sponsored by the Cellular Telecommunications Industry Association (CTIA). Wireless Access Controller WAC. A central point in a private branch or public switched network that provides a communications link to a host network or base station. Wireless systems require constant monitoring of signal strength and administration of user registration, hand-off, and roaming provided by the WAC so the user is not aware of the changing connections. Wireless Application Protocol WAP. A wireless telephony network protocol specification developed by a group of wireless vendors, including Ericsson, Motorola, Nokia and Unwired Planet (Phone.com, now OpenWave.com), in 1998. The technology was designed to work with a variety of industry mobile standards and handsets worldwide to facilitate widespread commercial distribution. It is intended to be operable with CDMA, TDMA/D-AMPS, GSM, DECT, as well as a number of dedicated mobile standards, including CPDP, Mobitex, iDEN, and Data TAC. WAP further supports FLEX and ReFLEX paging standards. See WAP Forum. Wireless Application Reader WAR. A Wireless Application Protocol (WAP) browser developed by Digital Mobility Limited, announced in March 2001. The browser is intended for use on Java-enabled phones and personal digital assistants (PDAs). It was developed for the J2ME Mobile Information Device Profile (MIDP) type of Java. wireless cable Wireless cable doesn’t utilize physical cables or, at least, is not predominantly based on wired connections, but is named that way to provide marketing familiarity for subscribers who are used to associating ‘cable services’ with television broadcast services. Thus, wireless cable refers to television broadcast services and, to some extent, interactive TV services delivered through the airwaves without physical cables (usually through microwave transmissions). Wireless Certificate Profile WCP. One of the wireless security projects of the WAP Forum, also called WAP Certificate Profile, based on work done within the IETF’s PKIX working group. Given the limited

resources of most handheld wireless devices, WCP is a reduced-footprint, reduced-processing security mechanism for identifying the holder of a public key, providing a means to bind the key to the appropriate user. It is intended that the WCPs work interchangeably with other X.509 certificates for maximum compatibility with the current Internet infrastructure. In general, WCPs are based on the Internet Certificate Profile. See WAP Forum. wireless communications protocol WCP. A transmission protocol specifically designed to accommodate wireless technologies. Wireless Consortium WC. An association and longterm independent facility established in 1996 through the University of New Hampshire’s InterOperability lab. It represents the cooperative interests of wireless products and services vendors wishing to develop and test IEEE 802-11-conformant products. Wireless Data Forum WDF. Formerly the Cellular Digital Packet Data Forum, the WDF is a nonprofit organization established to promote the acceptance and development of wireless data products and services, particularly those employing the Commercial Mobile Radio Services (CMRS) spectrum assigned by the Federal Communications Commission (FCC). This consensus-building organization holds its meetings in a variety of locations around North America. http://www.wirelessdata.org/ Wireless Datagram Protocol WDP. A protocol of the WAP Forum associated with the Wireless Application Protocol. The WDP was specified as version 14 in May 1999. WDP is one of two transport layer protocols defined as the Wireless Transaction Protocol (WTP) and the Wireless Datagram Protocol (WDP). WDP is a general datagram service. Hierarchically, the WDP layer operates above the data-capable bearer services, offering service to the upper layer protocol. It does not include an authentication mechanism. See Wireless Session Protocol. wireless dongle In general, a dongle is a communications-influencing device that restricts access, provides security or copy protection, or otherwise limits the communications that pass through it. It is often attached to a serial or other communications port between the computer communications interface card and external devices. Thus, a wireless dongle is a wireless transmitting and/or receiving device that is attached to equipment that is either wired or wireless. In recent years, the term dongle has been more loosely used to describe a host that is interfaced with multiple wireless devices, thus mirroring the hierarchy of the interface device that it is being used to supplement. Thus, the dongle is described as an interface device to aid in adapting wired device protocols and hardware to wireless operations. However, it is preferable to call this type of device a wireless adaptor rather than a wireless dongle, or the specific security or limiting aspect that has long been ascribed to the term dongle becomes confused. Wireless Information Networks Forum, Inc. WINF, WINForum. A trade association of manufacturers of unlicensed communication systems,

including personal communications services (PCS). WINForum works with the Federal Communications Commission (FCC) in the allocation of spectrum with the Unlicensed National Information Infrastructure (U-NII). See band allocations. Wireless Intelligent Network WIN. International Standard IS-41. Actual implementation of this standard is typically done in conjunction with time division multiple access (TDMA) technology. WIN is a network of realtime databases and transaction processing systems supporting the processing of the messages in a wireless transmission and manages roaming. See time division multiple access technology. Wireless LAN Interoperability Forum WLI Forum. A trade organization of wireless product and service organizations established to promote and support the growth of wireless LAN. The WLI Forum has developed and published an open interface specification for interoperability not intended to conflict with IEEE 802.11. The specification is based upon the RangeLAN2 radio frequency wireless LAN technology developed by Proxim, Inc. in 1994. It uses a multichannel spread spectrum frequency hopping architecture in the 2.4 GHz range at a data rate of 1.6 Mbps per channel. Wireless LAN Research Laboratory WLRL. A research laboratory established through the Center for Wireless Information Network Studies at the Worcester Polytechnic Institute (WPI) in Massachusetts. The lab serves as a center for the development, specification, and testing of hardware and software performance, compatibility, and interoperability. wireless local area network WLAN. A data network connected through radio wave and/or infrared transmissions rather than through cables and wires. Inter-building connections may be through line-of-site microwave connections. The IEEE is working on standards for wireless LANs through the IEEE 802.11 Working Group. The basic structure of the standard specifies three physical layers (two for radio, one for infrared) and one Media Access Control (MAC) sublayer to provide authentication, association, integration, and distribution services. Two configurations for wireless stations have been generalized as independent (directly

communicating stations) and infrastructure (communicating through inter-access points). There are a number of campuses that have wireless LANs, and the technology is gradually being adapted by corporations. There are advantages to both wired and wireless communications. Signals can be kept separate more easily in wired communications, but wireless is sometimes the only practical means for individuals or groups on the move to keep in communication with the network. There will probably be many situations where hybrid systems serve the greatest needs. See air interface, HIPERLAN, InterAccess Point Protocol, local area wireless network. wireless local area network physical layer WLAN physical layer. There are three physical layer (PHY) specifications for the IEEE 802.11 wireless local area network, two for radio and one for infrared transmissions. The radio PHYs specify spread spectrum frequency hopping and the direct sequence spread spectrum. The infrared PHY uses pulse position modulation with 16 positions. wireless local loop 1. WLL. A local telecommunications services distribution system that uses low power radio waves instead of wires. This is particularly cost effective in rugged terrain or sparsely populated areas, where it is not practical to lay cables. Wireless services may also be easier to install in some areas from a legislative/jurisdictional point of view with regard to Federal Communications Commission (FCC) licensing to local carriers. 2. WiLL. A Motorola, Inc. fixed wireless system designed to provide an alternative to traditional landline systems. WiLL systems are provided in two configurations: as public switched telephone network direct connect (PSTN-based) or as mobile telephone switching office/mobile switching center (MTSO/MSC-based) networks. The WiLL System Controller (WiSC) provides performance monitoring and radio channel control functions. Wireless Markup Language WML. A tag-based browsing language, similar to HTML, but specifically intended to be used on wireless handheld devices that have smaller screen sizes and more limited resources (memory, processing speeds, display characteristics, etc.) than desktop or laptop computerbased communications systems. WML evolved from

Wireless Local Area Network Physical Layers Type radio

Scheme

Modulation

spread spectrum/

Gaussian frequency shift keying

frequency hopping

Notes 1 Mbps with 2-level GFSK 2 Mbps with 4-level GFSK

radio

spread spectrum/

differential binary phase shift

1 Mbps

direct sequence

differential quadrature phase

2 Mbps

infrared

--

pulse position modulation

1 Mbps with 16 PPM 2 Mbps with 4 PPM

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HDML (Handheld Device Markup Language), which was developed in the mid-1990s by Unwired Planet (which became Phone.com and then Openwave). WML is XML-compliant and is now part of the WAP standard. Because WML servers and devices do not directly use HTML and other standard Web protocols, it is necessary to implement specialized security features in conjunction with WML if security is required. See HTML, WAP Forum. wireless packet switching A means of sending data over wireless networks similar in concept to packet switched wired networks. Like wired packet transmissions, a communication is subdivided into small data packages called packets. The packets are routed over the network, sometimes different portions of the message taking different routes, and reassembled at the receiving end. Routing will vary depending upon the current load on the routing stations, and the distance and number of ‘hops’ over which the message is transmitted. The message may even travel over wires for part of its journey. There are a variety of protocols for accomplishing this. See packet switching. Wireless Priority Services WPS. Under the umbrella of the WPS, there have been a number of wireless communications priority services established for cellular, PCS, and enhanced satellite communications in order to support the needs of national security and emergency preparedness (NS/EP). In Executive Order 12472, responsibility was assigned for conducting technical studies and assessing research and development programs to identify resources and approaches to assist U.S. authorities in fulfilling security and emergency-related telecommunications needs. See National Communications System, Priority Access Service. wireless public key infrastructure WPKI. A mechanism for adding security features to wireless communications through public key encryption and management techniques. WPKI is expected to enable more secure banking as well as more secure transmission of sensitive corporate and government data through wireless devices. There are many ways to implement WPKI through mobile devices but, in general, trusted registry agents are expected to generate and verify digital signatures while others will likely maintain digital signature directories to facilitate encounters and transactions. Secure servers operating over private or Internet links will handle and record the content and/or steps in a transaction to give it some of the legal force and protections of traditional transactions. In March 2001, Baltimore Technologies, AU-System, and Gemplus announced an advanced security and authentication digital signature technology for General Packet Radio Services (GPRS) networks through Ericsson handheld devices. For this system, the digital certificates are issued by network operators and content providers and are stored on the mobile devices using Subscriber Wireless Identity Module (S/WIM), a type of chip card. See public key encryption, wearable public key infrastructure.

Wireless Server Certificate WSC. An administrative and operational mechanism for implementing server-side security for microbrowser-equipped wireless devices conforming with Wireless Transport Layer Security (WTLS). There are two defined formats for WTLS certificates. • X.509 optional, similar to certificates used in Secure Sockets Layer security • WTLS mini-certificates mandatory, similar to X.509 but with a reduce-resource footprint adapted to the needs of small wireless devices (e.g., Personal Digital Assistants) Service providers seeking to secure a WAP server must purchase a Server Certificate from a Certificate Authority (CA) (examples include VeriSign, Baltimore, MobileTrust), by submitting a Certificate Signing Request (CSR). The issued certificate will have an encryption/decryption key-pair. The registration cost is approximately $900 per year depending upon whether it is an initial or short-term certificate. New short-term certificates that change every day or two may be available, reducing the probably of security breaches. Some companies provide shortterm trial certificates at no cost to help a provider become familiar with the process. The Certificate authenticates the WAP server-to-client wireless devices and then provides a transmission channel. Certificate issuers typically will provide third-party verification services associated with the Server Certificate. Note that the WAP microbrowser system works through proxy servers, so it is the gateway that handles the certificate. See WML Script Sign Text, Wireless Transport Layer Security. wireless service provider An authorized wireless communications supplier, usually providing cellular phone and paging services. Wireless Specialty Apparatus Company WSA. A pioneer radio parts manufacturer founded in 1906 by Greenleaf Whittier Pickard and Philip Farnsworth (who provided legal counsel to the company). By the mid-1940s, WSA had become one of the largest radio engineering manufacturers in the world, but it is chiefly remembered for its production of rugged, well-constructed radio wave crystal detectors in the early part of the century. Later, in conjunction with a number of other significant manufacturers (GE, Westinghouse, AT&T, etc.), WSA made an agreement for Radio Corporation of America (RCA) to be an exclusive distributor of radio receiving sets. WSA equipment is now found in many radio collections around the world and a number of the WSArelated legal documents (including patents) are part of the George H. Clark Radioana Collection now in the Archives Center of the National Museum of American History. wireless switching center WSC. A terminal center for switching wireless communications with other trunks or service. It’s not uncommon for wireless centers to interface with public switched telephone networks (PSTNs) and various landline facilities in order to route a call that originated as a wireless call through traditional routes. This makes use of the best

features of the various technologies, extends the range, and improves the transmissions clarity of wireless-originated calls. Wireless Session Protocol WSP. A session layer protocol family within the WAP architecture, approved in July 2001 by the WAP Forum. WSP provides the upper-level application layer of WAP with a consistent interface for session services, including a connection-mode service and a connectionless service. WSP services are currently best suited for network browsing applications. They provide HTTP 1.1 functionality and support for data push functions. They are optimized for low-bandwidth bearer networks with relatively long latency characteristics. See WAP Forum. Wireless Subscriber-Automatic Number Identification WS-ANI. A system for identifying the callback number (Mobile Directory Number) for wireless mobile phones. This is important in the context of 911 emergency calls from a mobile phone user, whose location will change. The callback number is used in the event of a 911 caller being cut off (or hanging up); it enables the operator to recontact the person in distress. Due to the importance of this service, fault-tolerant, redundant computer systems are provided to Public Safety Answering Points (PSAPs). In the BellSouth WS-ANI system, for example, wireless carriers interface with the SCC Communications Corporation Automatic Location Identification (ALI) data centers that manage the BellSouth information and services for the E911 system. Through BellSouth interfaces, wireless carriers use out-of-band data connections between the switching network and the ALI database. Physical connectivity is through ports with synchronous DB-25 connections supporting either RS-232 or V.35 electrical interfaces. They are configured as Data Terminal Equipment (DTE) devices. See Automatic Number Identification, PseudoAutomatic Number Identification. Wireless Transaction Protocol WTP. A light weight transaction-oriented protocol within the WAP architecture that provides the services necessary for interactive request/response (browsing) applications. During a session, the client requests information from a fixed or mobile server and the server responds, completing the transaction. WTP is intended to reliably deliver transactions while balancing reliability levels required for the application. WTP runs on top of a datagram service and may run on top of a security service. WTP is suitable for ‘thin’ clients wireless datagram networks. See WAP Forum. Wireless Transport Layer Security WTLS. A WAP Forum wireless protocol to enhance privacy, data integrity, and authentication for wireless transmissions. WTLS uses a client/server approach implemented at the security layer of the Wireless Application Protocol (WAP). It is similar to Transport Layer Security (TLS) and Secure Socket Layer (SSL) protocols with adjustments for the specialized characteristics of portable wireless devices. Unfortunately, these adjustments may make it vulnerable in some ways to data recovery, forgery, and datagram

truncation attacks, issues that need to be resolved because it is expected WTLS may be incorporated into large numbers of consumer communications devices. See WAP Forum, Wireless Server Certificate. wireless telephone service A variety of forms of wireless voice transmissions have been around for decades, but not in significant numbers, or they had significant limitations such as distance. The service now primarily means cellular telephone transmissions which first became established in 1983 in the U.S. Almost half the wireless systems in use were purchased to be used in emergency situations and the rest are divided among business and personal users. wireline 1. Communications circuits that are comprised of physical wires and cables, usually copper twisted pairs as in traditional telegraph and telephone lines, or fiber optic. 2. In cellular communications, not all aspects of the transmission are necessarily carried through wireless radio waves. Sometimes the system interfaces with a wired system for part of the transmission. A wireline cellular license granted to the local telephone company from the Federal Communications Commission (FCC) is designated as a B Block. It provides permission to operate at FCCspecified frequencies. wiretap n. A covert listening device or system of devices and procedures associated with a communications circuit (usually voice) for the purpose of eavesdropping and/or recording transmissions (conversations). The device need not necessarily be physically attached to the line being tapped; some devices can sense electrical emanations without directly touching the electrical conduit. Others can silently dial a phone and listen in to room noises even if the phone appears to be ‘on hook.’ Other than high level encryption through a digital line, there are no surefire ways to prevent unauthorized wire taps, especially on wire-based analog connections. Strictly regulated, wire taps require legal authorization and are permitted only in specific, carefully evaluated circumstances, usually by law enforcement officials. Wiretapping is much more difficult over secured digital lines, especially if they are being communicated over fiber optic cables which cannot be physically ‘tapped’ from outside in the same way as wirelines. See Anti-Terrorism Act of 2001, bug, trace. wiring closet In medium- and larger-sized wiring installations, whether for phone, computer networks, or other services, a wiring closet will often be designated on the premises as a central administrative and physical connections facility. This provides consolidated access to equipment and connections, and makes it possible to restrict access to unauthorized users. This is typically the location at which wires enter the premises from external sources or from the building distribution system, and may or may not be the demarcation point for the services, depending upon the type of service and the particular contract. Several wiring closets on a premises or campus may be cross connected. wiring grid The wiring architecture of a department, section, or building. This may be illustrated with a

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diagram of locations, connections, and circuits. The wiring grid may be monitored on a computer system, with consoles for determining and configuring routes and pathways and for diagnostic testing. WITS Wireless Interface Telephone System. Wizard 1. An elite professional, as a programmer, who appears to perform miracles with his or her solutions to problems, or ability to troubleshoot or configure a system. 2. A shortcut computer software applications helper that may consist of hotkeys or other means to quickly perform often-repeated tasks. Some programming Wizards are user-scriptable. 3. A computer software applications informational helper that may pop up in a particular context or be requested by the user. WLAN See local area wireless network and wireless local area network. WLANA An organization established to promote awareness and acceptance of wireless local area network technologies (also called local area wireless networks (LAWN)). WLANA provides education and support for the technology through standards committees and other venues. WLI Forum See Wireless LAN Interoperability Forum. WLL See Wireless Local Loop. WLRL See Wireless LAN Research Laboratory. WML 1. See Website Meta Language. 2. See Wireless Markup Language. WML Script Sign Text A function within the client/server Wireless Transport Layer Security (WTLS) Certificate system that enables WTLS servers to verify digital signatures. These signatures are stored with Certificate Authorities (CAs) rather than on the reduced-resource wireless devices, thus not hindering the size of the certificate. Client certificates are issued in the same manner as server certificates, through a certificate-issuing service. See Wireless Transport Layer Security. wobbled groove recording A recording technology for magneto-optical media. The region of the disc for user data storage has a series of irregular grooves, with the data stored in the groove. The wobbling of the groove is created based on a continuous sinusoidal deviation of the track from an average center line. Wobbled groove technology has the advantage of resistance to tiny defects. It is used in the production of DVD-RAM discs. See land/groove recording, wobbled land/groove recording. wobbled land/groove recording A high-density recording technology for magneto-optical media described in the mid-1990s and introduced commercially by Hitachi in 1998. Wobbled land/groove recording is the chosen format for DVD-RAM rewritable storage media. Wobbled land/groove recording takes advantage of the high-density recording features of land groove recording and the resistance to tiny defects of wobbled groove recording. Thus, data is recorded on both the upper surface (the land) and in the grooves enabling up to 2.6 GBytes per side. The address information is stored in the pit. Land and groove

tracks alternate with each revolution of the disc to form a continuous spiral track. This enables large data streams (e.g., video animations) to be recorded in a long, continuous spiral. To promote compatibility with existing DVD formats, the modulation and error-correction schemes for this recording format have been kept the same. The format has been supported by the DVD Forum for DVD-RAM discs. See land/groove recording, wobbled groove recording. WOM write-only memory. WOMBAT waste of money, brains, and time. One of the wittier of the acronyms seen in email and online public forums on the Internet. Women Inventors Project WIP. A Canadian project that highlights women who have contributed to technology in a variety of industries. The results of a collaboration of this project with the Canadian National Museum of Science and Technology is available as an educational traveling exhibit for loan periods of 6 to 8 weeks. Woodstock A Web-based stock trading game that makes use of actual NYSE and NASDAQ market information (updated every 30 minutes). It runs on the Windows CE operating system. Woodstock File Server A simple, shared file server with a limited command set that clients use to communicate over a network with the server. The system responds to page-level requests as though it were a remote disc, as opposed to a connection. The client program is responsible for implementing the directory system, stream, etc. WFS utilizes connectionless protocols and atomic commands. It was developed in 1979 by Xerox Palo Alto Research Center (PARC). WORA write once run anywhere. A slogan usually used in context with Java, the portable programming language from Sun Microsystems, but which can apply to any software designed to be portable, that is, platform- and/or application-independent. word In computer programming, a contiguous group of a specified number of bits (basic information units) constituting an information entity transferred or processed as a unit. The length of a word varies from system to system, with smaller systems usually processing a word as 8 bits, and larger systems as 32 bits. Some supercomputing systems handle a word as 64 bits. Commonly, a word is a multiple of 8 bits, as a byte is 8 bits, and is a basic unit of information between a byte and a longword. The lack of standardization results from the fact that systems continue to become more powerful, with CPUs and buses handling larger and larger information units at a time; larger systems typically lead smaller systems in this evolution. In networking, the term octet is often used to mean eight bits in order to prevent the ambiguity associated with byte and word. word spotting In speech recognition, the selective recognition of a predetermined sound. This can be used to glean specific information or to filter extraneous noise or information. Word spotting is

demonstrated in Star Trek episodes on the turbolift, where turbolift commands are recognized, but general conversation is ignored. The same concept applies to automated door and phone systems, and software programs configured to recognize only relevant material. words per minute WPM. A description of the speed of a communication over time. Commonly used to measure speed in typing, printing, code sending, and some data communications. work order WO. A widely used administrative tool, especially in the trades, to request and record work to be done. Usually in the form of a document, a work order may be assigned a number and/or a priority, and provides a sequential record of the people, parts, and procedures involved in carrying out a requested job. Work orders help track customer requests, work and completion cycles, and sometimes include details as to who did the job and how. The work order may also include billing information or may be used as a reference for creating a separate invoice. work station See workstation. workflow The sequence and path of work in an organization, environment, or department. Workflow management is especially important in production line settings where actions must take place in a particular order and location to keep the line up and running. In service-oriented environments, it refers to the efficient deployment of staff and resources, timed, allocated, and adjusted to process calls and requests as they come in. The term workflow applies in computer technology to the sequence and path of data transport and its management. workgroup Individuals within an organization who share certain tools, software applications, or tasks, typically on a network. Priority and access levels within a specified workgroup are often similar. A person may belong to more than one workgroup, and workgroup access to resources may overlap from one group to another. Software companies have been targeting as workgroups people within an organization who share communications or applications needs without necessarily being in the same department or physical location. Workgroup applications include electronic mail, word processors, spreadsheets, scheduling programs, and others. workgroup manager A supervisory individual who has authority to assign login, priority, and security parameters to individual computer network users organized into workgroups. The manager may use a software utility to set up the system, or may pass on information about the organizational structure to the system administrator, who then sets up the computer configuration. workload 1. The maximum or effective capacity or capability of an employee or system to handle work tasks, usually within a given time period or with regard to deadlines. 2. In networks, workload may be measured by the number of transmissions or the quantity of information that can be processed within a specified interval. workstation In telecommunications, a networked or networkable computer that fits somewhere between

the low-end consumer market and the high-end computing market (scientific research, military, high-end medical imaging). Some people refer to all microcomputers as workstations; some refer only to microcomputers with enhanced processors, storage, and memory as workstations; and some refer to microcomputers with decent processing speed and robust operating systems suitable for professional work as workstations. In general, the least and most expensive computers are not called workstations. World Administrative Radio Conference. WARC. A global space telecommunications conference that convened regularly. Founded in June 1971 by the ITU to review regulations relating to radio astronomy and extraterrestrial communication. At the 1979 general conference, significant access to bands between 1 and 10 GHz was provided for amateur radio satellite programs, bandwidths that the operators had previously been restricted from using. World Administrative Telegraph and Telephone Conference WATTC. A body formed as a result of a resolution at the 1982 Plenipotentiary Conference of the International Telecommunication Union (ITU). It was scheduled to convene in 1988 to consider proposals for a new regulatory framework to handle new situations in the field of telecommunication services. IN 1984, the CCITT resolved to set up a Preparatory Committee (PC) in preparation for WATTC-88 to prepare the draft text of the new Regulations to be submitted to the CCITT Plenary Assembly. The purpose and scope of the Regulations were to establish general principles for the provision, underlying transport, administration, and operation of international telecommunication services offered to the public (including legal and governmental bodies). World Association of Community Radio Broadcasters AMARC. An international nongovernmental organization promoting global cooperation that serves community radio broadcasting in more than 100 countries. AMARC dates back to meetings in Canada and other countries in the early 1980s and the formation of the International Solidarity Network in the early 1990s. These efforts culminated in the official founding of the organization at the 2nd World Assembly in 1996. AMARC seeks to support diversity and friendship, to support women’s efforts in the field of community broadcasting, and to promote solidarity, cooperation, cultural identity, and independence of all peoples through community programming. See Community Broadcasters Association. World Congress on Insulator Technologies An annual trade conference on industrial and research aspects of insulators. Examples of some of the topics include performance assessment in various environments, design and reliability of different types of insulators, field handling, and materials used in new generation insulators and their operating performance. World DAB Forum See Digital Audio Broadcasting Forum. World Intellectual Property Organization WIPO. A Geneva-based global organization comprising over 160 member countries that promotes, supports, and

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educates about intellectual property protection through international treaties. Recently, WIPO has been actively involved in the debate over domain name assignments and jurisdictions. See Digital Millennium Copyright Act. http://www.wipo.org/ and http://www.wipo.int/ World Internetworking Alliance WIA. A coalition of parties working to develop an international, independent, autonomous Internet institution within which diverse bodies can work in a cooperative effort toward creating an open, robust, competitive marketplace. http://www.wia.org/ World Numbering Zone See World Zone. World Radiocommunication Conference WRC. A month-long, international assembly administrated by a number of committees and working groups to deal with important matters of spectrum allocations and other technical matters related to global radio communications. The conference is convened every two or three years as the official forum for revisions to the international Radio Regulations. One of the important outcomes from WRC-2000 was support for global wireless systems (especially 3G) that facilitated commercial implementations of wireless technologies. World Report on the Development of Telecommunications Information and economic reports on global telecommunications developments. This is a publication of the International Telecommunications Union (ITU). World Telecommunication Policy Forum WTPF. An organization established as a result of the Kyoto Plenipotentiary Conference wherein members can discuss matters of telecommunication policy and regulation, and provide reports and opinions to the ITU. The first meeting was in 1996, with a discussion theme of global mobile personal communications by satellite (GMPCS). World Telecommunications Advisory Council WTAC. A global private and public sectors organization established in 1992 that studies telecommunications implementations and advises the SecretaryGeneral of the ITU on matters of policy and strategy. Originally composed of top level managers, the organization now also includes consultants, government officials, and entrepreneurs. The WTAC has provided a number of publications and sponsorships, including a booklet entitled “Telecommunications: Visions of the Future,” WorldTel sponsorship, and a global mobile personal communication systems (GMPCS) symposium. World Wide Web Web, WWW, W3. The W3 was first proposed in March 1989 by Tim Berners-Lee (CERN), who created the first Web software a few months later which he publicly introduced in 1991. The Web is the single most significant implementation on the Internet and has spurred global access and acceptance not only by technical professionals, but by computer novices and laypersons. In a sense, it constitutes a simple graphical user environment for the Web (it is actually much more than that, but that is how 80% of new users first perceive it) and, as such, its use will probably greatly change and grow

in future revisions of Web browsers, especially now that Netscape, the primary browser, is freely distributable with source code. A browser actually gives a thin window on the Web, as it consists of more than just a browser front-end. It is built on a set of protocols and conventions that make access and transfer of information widely available. The first international WWW conference was held in 1993. See browser, HTML.

A portion of the CRC Press ‘storefront’ on the World Wide Web, as viewed with the Netscape Web browser. The Web ‘address’ for this site is expressed in the browser as http://www.crcpress.com/. In this manner, the WWW acts as client/server resource topology that supports Web browsers as a graphical front-end to many millions of resources on the Internet. This makes it relatively easy for those without much experience with computers to surf the Web. The Web is probably one of the most significant landmark developments in commerce that has occurred in the history of human transactions, in addition to its significant impact on communications and social evolution. Before the development of the Web, the Internet was used primarily by military and research organizations and a small percentage of technically inclined individuals. It now reaches more than 60 million people worldwide and the number is rapidly growing.

World Wide Web Conference Committee, International World Wide Web Conference Committee IW3C2. Founded in 1994 by NCSA and CERN, the IW3C2 was incorporated as a nonprofit Swiss Confederation association in 1996. IW3C2 organizes international telecommunications conferences focusing on the World Wide Web, and makes the information resulting from these conferences open to the widest possible audience. IW2C2 promotes and

assists in the global evolution of the Web through a broadbased international body. Currently, the IW3C2 selects one academic institution per year to host the IW3C2 conferences. http://www.iw3c2.org/ World Wide Web Consortium WWWC, W3C. An industry consortium of more than 150 organizations, founded in 1994 to promote the development and use of common standards for the evolution of the World Wide Web (WWW). The W3C develops and maintains information repositories for programmers and users, reference code for implementation of recommended standards, prototypes, and sample applications. http://www.w3.org/ World Zone, World Numbering Zone Geographic divisions devised to facilitate the global linking of national telephone services, a system developed in the 1960s. Country codes of one to three digits in length were assigned to specified regions. As examples, World Zone 1 represents most of North America and some Caribbean countries, 2 is Africa, 3 and 4 represent parts of Europe. In an international long-distance call, the country code is the first part of the phone number dialed. worm A computer program that replicates itself through host systems without the specific need to attach itself to a file. Since a virus is a self-replicating program that requires a host file, a worm program can be seen as a ‘standalone’ variation of a virus or can be considered a separate category. Here it is treated as a specific type of virus. The worm may be self-replicating within the host system or may be controlled from a remote site or sites in such a way that it is not wholly dependent upon specific resources in the computer system it has infected. This is a less common and sometimes more sophisticated program than many of the computer viruses that are attached to downloaded files and email messages. A worm ‘worms’ its way through a network much as a biological worm wiggles its way through soil or wood, creating a trail of holes and tunnels that have been compared to the intermittent ‘holes’ that occur in file storage space or running processes on a system on which there is a worm program. A worm may also be combined with other types of invasive ‘organisms’ such as Trojan horses (e.g., a worm may be a conduit for spreading and implanting an accompanying Trojan horse program). See Computer Emergency Response Team, Trojan horse, worm. See virus for further details and specific examples. WORM write once read many, write once read multiple. Although this commonly refers to optical storage media that are not as readily written as magnetic media, it generically means any storage medium that is typically written (easily) only once, and is usually read, or can be read, many times by the user. Most CD-ROMs fit into this category, although read/write optical systems are coming down in price to the point where they may become consumer items. Kodak PhotoCD discs demonstrate that consumer products on CDs can be written in several sessions. See compact disc.

WORM-ARQ WORM - Auto Repeat Request. ARQ is a means to achieve reliability in network transmissions by using an error detection scheme in conjunction with a block retransmission scheme for blocks found to have errors. WORM-ARQ is a technology developed by Nippon Telephone and Telegraph (NTT) DoCoMo for frame-based broadband network transmissions. Depending upon the transmission’s quality, WORM-ARQ will switch, as needed, between Selective Repeat (SR) and GoBack-N (GBN) systems to maintain stability at high efficiency levels. WOSA See Windows Open Services Architecture. WOTAN Wavelength-Agile Optical Transport and Access Network. An ACTS project for developing and providing a managed, end-to-end optical communications system for public communications networks. WOTAN investigates and tests a mix of optical and electronic combinations for switching and networking to determine an optimum mix for building an integrated, upwardly flexible system based on wavelength agility and distributed wavelength routing and switching. Project participants include a number of U.K. and continental European companies, universities, and labs. Test systems are established in cooperation with BT Laboratories and their East Anglia Network test bed. See BLISS, BROADBANDLOOP, and UPGRADE. wow An undesirable undulating audio distortion from various causes including uneven rotation of a turntable or tape reel. Wozniak, Stephen (Woz) (1950- ) Steve Wozniak was a shy, inventive child, given to tinkering with electronics and entering projects in science fairs. When he first became friends with Steve Jobs, neither one realized they would soon be making history and millions of dollars. Wozniak was constantly working on hardware projects in his parents’ home and was naturally drawn to the hobbyists who began to meet and talk shop at the Homebrew Computer Club. Together with Bill Fernandez in 1971, Steve Wozniak built a simple computer from cobbled together parts called the Cream Soda Computer. From 1973 to 1976, Wozniak worked in electronics at Hewlett-Packard. After meeting John Draper, Woz began to collaborate with Steve Jobs in developing blue boxes, phone devices that provided unauthorized access to long-distance services. After this ran its course, he was inspired by the homebrew members and a Popular Electronics feature of the Altair computer kit to develop the Apple I computer. This lead to formation of Apple Computer in 1976, a change of operations to Steve’s home, and the subsequent creation of the historic Apple II computer. Wozniak’s engineering feat consisted not only of building one of the first microcomputers, but of doing it with elegance and flair by substantially reducing the number of chips needed to perform various functions in the computer. Meanwhile Jobs sought out marketing and venture capital experts, and added a crucial link that had been missed by other electronics

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buffs building small computers and computer kits: The Apple II (Apple ][) succeeded in part because it was the first easy-to-use, fun computer (despite the fact that they first considered marketing to businesses), and the Apple turned out to be a great tool for schools and home users. Thereafter they put their focus on education, a direction that appealed to the humanitarian spirit in both of them. Wozniak stayed with Apple Computer until 1985 when he left to form a wireless electronics company called CL-9 (Cloud Nine). Through all his ventures, he has participated in many educational and philanthropic activities. He is the founder and current president of Unuson Corporation in which he enjoys his time playing and teaching guitar. WPG Wireless Protocols Group. See WAP Forum. WPS See Wireless Priority Services. WPKI 1. See wearable public key infrastructure. 2. See wireless public key infrastructure. WRAM Windows Random Access Memory. A type of memory similar to VRAM (virtual RAM), but faster and less expensive; it is commonly used to enhance graphics performance. WRAM offers bisynchronous input/output. See VRAM. wrap A redundancy mechanism used in International Business Machines (IBM) Token-Ring local area networks (LANs). Token-Ring cabling is set up with two trunks, one for normal use and one for a backup. If something happens to the main trunk, a disconnected TCU connection creates a signal that causes the path to ‘wrap’ onto the backup trunk in order to maintain the interconnections through the ring. See Fiber Distributed Data Interface. wrap connector A diagnostic tool that interconnects cables or controllers to verify the circuit. wrap plug A diagnostic device which, when plugged into a computer port, causes the data to be looped around back to the port. wrap test A diagnostic test in which a signal is looped back through a device, usually to see if the input signal and the output signal match. wraparound 1. In word processing, the automatic wrapping of text onto the next line, when it reaches the end of the line, which may be an indent, margin, window, or screen. This is similar to the line feed and carriage return on a typewriter. 2. A circumstance where visual or textual information goes off the edge of the display device, usually the bottom or righthand side, and the information that would be clipped off by the edge is ‘wrapped around’ to the opposite side. For example, if a window drops off the bottom of a computer monitor, the bottom part may be displayed at the top of the monitor. Display wraparounds are usually undesired and are a result of programming bugs. However, there are circumstances where wraparound enhances the perception of a bigger screen, such as graphical scenes in which a landscape is intentionally wrapped, usually from side to side, to give the illusion of an infinite landscape. WRC See World Radiocommunication Conference. write To record data, as to a storage device, such as RAM, a hard drive, or a floppy drive. Many

computer data storage media use a means of rearranging magnetic particles in order to form patterns that are subsequently recognized and interpreted by software. Since this can be done many times, these media can be reused. There are also media which can only be written once. See WORM, write protect. write head A storage write mechanism that is designed to put data on the writable medium, which may be tape, a diskette, an optical disk, a vinyl record, etc. Write heads are sometimes separate from read heads, and are sometimes incorporated into combined read/write heads. write protection A device or method for protecting a medium from accidentally being overwritten with other data or erased. Most computer diskettes and audio and video tapes have simple physical write protect mechanisms that usually involve covering up a small hole with a label or a plastic tab. This allows the drive or tape mechanism to recognize that it should not alter the diskette or tape if the user accidentally tries to save something to the diskette (or erase it) or record on the tape. With computer storage media, software write protect methods exist as well. WRS Worldwide Reference System. A global indexing scheme designed for Landsat. WRT An abbreviation for “with respect to” used in memos and online communications. See FYI. WS-ANI See Wireless Subscriber-Automatic Number Identification. WSA See Wireless Specialty Apparatus Company. WSC See wireless switching center. WSG Wireless Security Group. See WAP Forum. WSP Wireless Service Provider. WST See WAP Security Toolkit. WTA Wireless Telephony Applications. See WAP Forum. WTAC See World Telecommunications Advisory Council. WTB Wireless Telecommunications Bureau. An organization of the Federal Communications Commission (FCC). WTLS See Wireless Transport Layer Security. WTO World Trade Organisation. An international organization established in 1994. As the Internet has become a significant vehicle for domestic and international commerce, the WTO has become involved in discussions about electronic commerce and in the debate regarding intellectual property and domain name registration. The functioning of the WTO has been scrutinized by critics who are concerned about ensuring that there is adequate accountability built into the function and makeup of the organization. WTPF See World Telecommunication Policy Forum. WWV A U.S. Government National Institute of Standards and Technology (NIST) radio facility providing time and frequency standard voice announcements at a variety of high frequency (HF) broadcast wavelengths. WWVH operates 24 hours a day, 7 days a week from a radio station in Colorado. The time is announced by a male voice based on a

24-hour clock at the Greenwich meridian and thus must be converted to local time by adjusting for the distance to Greenwich in time zones. WWYH broadcasts on 5, 10, and 15 MHz at 10,000 watts and on 2.5 MHz and 20 MHz at 2500 watts using individual transmitters for each frequency. WWV uses five half-wave vertical antennas, each connected to a transmitter through rigid coaxial lines, mounted on half-wavelength tall towers (ca. 7.5 to 60 meters depending upon wavelength). Modulation is double-sideband amplitude modulation (AM). See WWVB, WWYH. WWVB A U.S. Government National Institute of Standards and Technology (NIST) radio facility providing time and frequency standards broadcast at 60 kHz with 50 kW of power from Fort Collins, Colorado. WWVH operates 24 hours a day, 7 days a week. Unlike WWV and WWYH, this is not a voice announcement service, but rather a reference based on a stable radio frequency transmission that can be traced to the national standard. At WWVB, a time code is synchronized with the carrier for continuous broadcast at a rate of 1 bps using pulse-width modulation. The time code bits are produced by reducing and restoring carrier power, thus creating a low/high binary system that is used to represent decimal numbers. In this manner, the time code conveys the current year, day, hour, minute, and second along with flags that indicate Daylight Savings Time (DST) and leap year/leap second status. WWVB uses two top-loaded dipole antennas utilizing four towers in a diamond configuration with capacitance cables suspended between the towers. Commercially available clocks and wristwatches that derive their time from NIST-based WWVB broadcasts can be used within the continental U.S. There are also software clients that enable Internet-connected computer users to synchronize their computer time with NIST time. This type of capability will become increasingly important as auction sites, stock sites, and other types of time-sensitive electronic commerce services become more widely used. See binary coded decimal, WWV, WWYH. WWVH A U.S. Government National Institute of Standards and Technology (NIST) radio facility providing time and frequency standard voice announcements at a variety of high frequency (HF) broadcast wavelengths. WWVH operates 24 hours a day, 7 days a week from a radio station in Hawaii. The service includes time announcements, standard time intervals, time frequencies, time corrections, BCD time code, and various weather and Global Positioning System (GPS) reports. The time is kept within 1 microsecond of Coordinated Universal Time (UTC), but will become delayed as it propagates out from the source. In other words, there is lag time (travel time) from the radio station to the receiver that is dependent upon distance and atmospheric conditions. There can be delays up to 10 or 40 milliseconds, depending upon whether the user is listening through a radio receiver or a telephone receiver. The time is announced by a female voice (“At the

tone the time will be ...”) based on a 24-hour clock at the Greenwich meridian and thus must be converted to local time by adjusting for the distance to Greenwich in time zones. Since 1964, the female voice has been that of Jane Barbe, whose recorded messages are used on millions of telephone and timerelated products. WWYH broadcasts on 5, 10, and 15 MHz at 10,000 watts and on 2.5 MHz at 5000 watts using individual transmitters for each frequency. The 5-, 10-, and 15-MHz frequencies use phased-array vertical dipole antennas (driven 90° out of phase), whereas the 2.5-MHz frequency uses half-wave vertical antennas. Modulation is double-sideband amplitude modulation (AM). See Barbe, Jane; WWV; WWVB. WWW See World Wide Web. WWWC See World Wide Web Consortium. WYGIWYD (pron. wiggy-wid) An abbreviation for “what you got is what you deserve.” In other words, if you made a bad decision, you should accept the consequences. WYGIWYD applies to mistakes, impulsive decisions, bad purchases, etc., but also to situations where managers direct employees to use the wrong tools for the job, such as requiring one type of software or computer system when another is more suitable for the job (it’s like telling a carpenter to use a screwdriver rather than a hammer to drive in nails). WYPFIWYG (pron. wip-fee-wig) An abbreviation for “what you pay for is what you get.” It applies as much in computer technology as anywhere else. If you buy a cheap system, you may pay more later for adding extra memory, sound cards, graphics cards, hard drive controllers, CD-ROM drives, etc. The same applies to network server software. A cheap system may cost substantially more in the long run in terms of administrative time, productivity, and lost access due to downtime. WYSIWYG (pron. wiz-ee-wig) An abbreviation for “what you see is what you get.” A desktop publishing term that refers to a computer display of a document or image that looks on the screen the way it would look on the intended output device, usually a printer. The term became prevalent when desktop publishing programs on the Macintosh could be printed on Adobe PostScript-capable printers, beginning in the mid-1980s. Up to this time, dot matrix printers were prevalent and no matter how nice it looked on the screen, it rarely looked that spiffy on the dot matrix printout (especially on the ubiquitous 9-pin printers). Display PostScript, as was incorporated into the NeXTStep screen display, comes close to WYSIWYG, since many high-end printers and publishing programs use PostScript. Most professionallevel desktop publishing software programs now provide a good measure of WYSIWYG, especially if the system is run with a high resolution display (e.g., 1024 x 768 or better) and scalable fonts. Some word processing programs provide WYSIWYG capabilities, but many do not (kerning, leading, and even page breaks may change when

W

printed). WYSIWYG capability depends partly on having the system correctly configured. If the fonts on the computer are not available on the printer or are not downloaded to the printer, there will be substitutions (often Courier). Obviously, a 72- or 75-dots per inch (dpi) computer display cannot visually match a 1200-dpi printout and, in fact, the fonts used for the screen display are often optimized for the

monitor, separate from printer fonts. In some ways, WYSIWYG on low-priced consumer systems is really more of a goal than a reality at present; in the meantime, good software, fonts, and a little imagination and familiarity with the various types of output can provide good results even without a WYSIWYG system. WZ1 World Zone 1. See World Zone.

X, x 1. symb. an unknown, situational, derivable, or arbitrary quantity. Commonly used in mathematics and software programming, written both lower- and uppercase, and often italicized as in 4 + x = 10. The symbol is also often used in product identification to indicate a family of products, e.g., xDSL for the family of Digital Subscriber Line services. 2. abbrev. cross. 3. abbrev. exchange. 4. abbrev. external. 5. abbrev. trans- (prefix). 5. The USOC Federal Communications Commission (FCC) code for complex multiline or series jack. 6. colloq. See X Window System. X axis, x axis A common convention for coordinate systems (e.g., Cartesian coordinates) is to designate the horizontal axis as the X axis. When graphing processes that may occur over time, the X axis is often used for the time variable. X Consortium A group that continued the development and management of the X Window System, now part of the Open Group. See X Window System. X cut A type of cut used with piezoelectric crystals. Crystals are used in radio wave detection and timing applications, and their piezoelectric properties are partly determined by their shape and size. An X cut creates a crystal plate with the plane perpendicular to the crystal’s X axis. See crystal, detector, quartz, piezoelectric, X-ray goniometer, Y cut, Y bar. X Files A highly popular evening UFO-paranormalFBI-spoof television drama series starring Gillian Anderson and David Duchovny. It’s mentioned here because some of the episodes featured interesting telecommunications technologies and because some of the more imaginative episodes hinted at future technologies that have yet to be devised. Science fiction themes have often been the forerunners of viable technologies that are invented years or decades later. The show was popular with techie gurus. X Protocol A low-level client/server standard communications protocol that handles window manipulation routines for the graphical user interface (GUI) X Window Systems. See X Window System. X Series Recommendations A set of ITU-T recommendations providing guidelines for interconnecting networks and network devices. These are available as publications from the ITU-T for purchase and a

X

few may be downloadable from the Net. This is a large category; some of the X Series Recommendations of particular interest are listed in the following charts, organized into three categories. See Appendix C for a general list of the different categories. See also individual listings under G, I, Q, and V Series Recommendations. X Window System, The X Window System, X Windows, X, X.11 Hardware-independent foundation software for the development of graphical user interfaces (GUIs) based upon a client/server model. The X Window System is a nonproprietary, distributed, multitasking, network-transparent protocol that has been implemented on many different Unix-based systems. Originally used as a graphics display protocol for text-based UNIX platforms, developers are recognizing and exploiting its ability to enable popular OSs to run on a UNIX workstation or, conversely, to run UNIX applications on popular hardware platforms, and to run applications from within Web browsers. Development tools such as Motif facilitate the quick design of X GUIs. The X Protocol is an X Windows System client/ server protocol and the X server is a client/server process that controls a display device on The X Window System. X Windows code for noncommercial purposes is freely downloadable from The Open Group Web site. As of version X11R6.4, commercial users must pay a license fee, which will be used by The Open Group to continue support for these development efforts. See Athena project. http://www.opengroup.org/ X Window System 11 Release 6.x (X11R6.x) A substantial initiative by The Open Group to enable the X Window System to be used to create and access interactive World Wide Web applications through the X Window System and a downloadable plugin. Applications linked to the Web using X11R6.x can be found, accessed, and executed with the same Web browsing utilities used to access current static HTML documents. This may become a very significant means of networking through the Internet. See X Window System. X Window System history X was originally developed by Robert Scheifler and Ron Newman from the Massachusetts Institute of Technology (MIT) and

X

ITU-T X Series Recommendations Prevalent Formats X.25

Definitions of the procedures for exchanging data between user devices (DTEs) and network nodes in a public switched packet data network (PSPDN) in order to provide a common interface across a variety of systems. X.25 is a layered packet transmissions protocol commonly used in wide area networks (WANs). A version of X.25 specifically designed for packet radio has been developed as AX.25.

X.400 An international ISO/ITU-T series of standards for electronic messaging architecture for the exchange of data between computer systems. X.400 was published by the ITU-T in 1984. The standard was jointly rewritten by ISO and ITU-T in 1988. X.400 does not stipulate the formatting of data. It provides guidelines for internetworking various messaging systems, addressing individual messages, and describing message contents. Within X.400 there are also substandards and recommendations to X.400, some of which are: X.402 describes the overall architecture; X.420 describes email transfer; X.435 defines the electronic movement of Electronic Data Interchange (EDI); and X.440 describes voice messaging. See Electronic Data Interchange. X.445 Asynchronous Protocol Specification (APS). A commercially promoted multiple media client/server extension of the X.400 standard that facilitates the exchange of digital data over public phone networks rather than X.25 standard leased lines. X.500 A directory service protocol for building distributed global directories. It was developed in response to a need to design directories that would not experience the same problems and bottlenecks that were developing with many of the large databases being accessed by thousands or millions of users on the Internet. X.500 employs decentralized maintenance, searching capabilities for complex queries, homogenous global namespace, and a structured standards-based information framework.

Recommendations of Particular Interest X.1

International user classes of service in, and categories of access to, public data networks and integrated services digital networks (ISDNs). Includes information on access to leased or switched circuits by data terminal equipment (DTEs) in various modes, access by facsimile terminals, and access to Frame Relay systems. X.6 Multicast service definition. Service definitions and capabilities of a multicast service providing a common model for the description of service elements. Interface specifications and protocol elements are not specified by X.6. X.31 Support of packet mode terminal equipment by an ISDN. Service and signaling procedures definitions operated at the S/T-reference point of an ISDN for subscribing packet mode terminal equipment and terminal adapter functionalities to support existing X.25 terminals at the Rreference point of the ISDN. X.75 Packet-switched signaling system between public networks providing data transmission services. A description of packet-switching signaling systems among public data networks. X.76 Network-to-network interface between public data networks providing the Frame Relay data transmission service. A description of interface interconnections between Frame Relay networks and public data networks. Layer, data transfer, and signaling information are provided. X.77 Internetworking between PSPDNs via B-ISDN. Definitions of procedures for internetworking that include reference configurations, protocol stacks, and signaling procedures. X.121 International number plan for public data networks. A description of the design, characteristics, and applications of the numbering plan for public data networks. The International Number Plan was developed to facilitate the linking of public data networks with the

worldwide system. It describes country identification (assigned by the ITU-T), regional/local network identification, and a mechanism for integrating with other numbering plans. Guidance for efficient allocation of numbers is included, along with eligibility criteria and procedures. See Data Network Identification Codes. X.122 Numbering plan interworking for E.164 and X.121 number plans. Information on interworking with other numbering plans. Brief Listing of Further X Series Examples X.2

International data transmission services and optional user facilities in public data networks and ISDNs. X.3 defines a set of parameters used for regulating basic functions such as terminal characteristics, flow control, and data forwarding. X.3 Packet assembly/disassembly facility (PAD) in a public data network. X.4 General structure of signals of international alphabet No.5 code for character-oriented data transmission over public data networks. X.5 Facsimile Packet Assembly/Disassembly facility (FPAD) in a public data network. X.7 Technical characteristics of data transmission services. X.8 Multiaspect pad (MAP) framework and service definition. X.10 Categories of access for data terminal equipment (DTE) to public data transmission services. X.20 Interface between data terminal equipment (DTE) and data circuitterminating equipment (DCE) for startstop transmission services on public data networks. X.20 bis Use on public data networks of data terminal equipment (DTE) designed for interfacing to asynchronous duplex V Series modems. X.21 Interface between data terminal equipment and data circuit-terminating equipment for synchronous operation on public data networks. A digital signaling interface that includes specifications for physical interface elements, character alignment, and data transfer.

X.21 bis Use on public data networks of data terminal equipment (DTE) designed for interfacing to synchronous V-series modems. X.22 Multiplex DTE/DCE interface for user classes 3-6. X.24 List of definitions for interchange circuits between data terminal equipment (DTE) and data circuitterminating equipment (DCE) on public data networks. X.25 Interface between Data Terminal Equipment (DTE) and Data Circuitterminating Equipment (DCE) for terminals operating in the packet mode and connected to public data networks by a dedicated circuit. X.28 DTE/DCE interface for a start-stop mode data terminal equipment accessing the packet assembly/disassembly facility (PAD) in a public data network situated in the same country. X.29 Procedures for the exchange of control information and user data between a packet assembly/disassembly (PAD) facility and a packet mode DTE or another PAD. X.30 Support of X.21-, X.21 bis-, and X.20 bis-based data terminal equipment (DTEs) by an integrated services digital network (ISDN). X.32 Interface between Data Terminal Equipment (DTE) and Data Circuitterminating Equipment (DCE) for terminals operating in the packet mode and accessing a packet-switched public data network through a public network. X.33 Access to packet-switched data transmission services via Frame Relaying data transmission services. X.34 Access to packet-switched data transmission services via B-ISDN. X.35 Interface between a PSPDN and a private PSDN based upon X.25 procedures and enhancements to define a gateway function provided in the PSPDN. X.36 Interface between data terminal equipment (DTE) and data circuitterminating equipment (DCE) for public data networks providing Frame Relay data transmission service by a dedicated circuit.

X

X Series Recommendations, cont. Brief Listing of Further Examples, cont. Encapsulation in X.25 packets of various protocols including Frame Relay. X.38 G3 facsimile equipment/DCE interface for G3 facsimile equipment accessing the Facsimile Packet Assembly/Disassembly facility (FPAD) in a public data network situated in the same country. X.39 Procedures for the exchange of control information and user data between a Facsimile Packet Assembly/Disassembly (FPAD) facility and a packet mode Data Terminal Equipment (DTE) or another FPAD. X.42 Procedures and methods for accessing a Public Data Network from a DTE operating under control of a generalized polling protocol. X.45 Interface between Data Terminal Equipment (DTE) and Data Circuitterminating Equipment (DCE) for terminals operating in the packet mode and connected to public data networks, designed for efficiency at higher speeds. X.48 Procedures for the provision of a basic multicast service for Data Terminal Equipment (DTEs) using 25. X.49 Procedures for the provision of an extended multicast service for Data Terminal Equipment (DTEs) using 25. X.50 Fundamental parameters of a multiplexing scheme for the international interface between synchronous data networks. X.50 bis Fundamental parameters of a 48-kbps user data signaling rate transmission scheme for the international interface between synchronous data networks. X.51 Fundamental parameters of a multiplexing scheme for the international interface between synchronous data networks using a 10-bit envelope structure. X.51 bis Fundamental parameters of a 48-kbps user data signaling rate transmission scheme for the international interface between synchronous data networks using a 10-bit envelope structure.

X.52

Method of encoding anisochronous signals into a synchronous user bearer.

X.53

Numbering of channels on international multiplex links at 64 kbps.

X.54

Allocation of channels on international multiplex links at 64 kbps.

X.55

Interface between synchronous data networks using a 6 + 2 envelope structure and single channel per carrier (SCPC) satellite channels.

X.56

Interface between synchronous data networks using an 8 + 2 envelope structure and single channel per carrier (SCPC) satellite channels.

X.57

Method of transmitting a single lowerspeed data channel on a 64 kbps data stream.

X.58

Fundamental parameters of a multiplexing scheme for the international interface between synchronous nonswitched data networks using no envelope structure.

X.60

Common channel signaling for circuit switched data applications.

X.61

Signaling System No. 7 – data user part.

X.70

Terminal and transit control signaling system for start-stop services on international circuits between anisochronous data networks.

X.71

Decentralized terminal and transit control signaling system on international circuits between synchronous data networks.

X.80

Interworking of interexchange signaling systems for circuit-switched data services.

X.81

Interworking between an ISDN circuit-switched and a circuitswitched public data network (CSPDN).

X.82

Detailed arrangements for interworking between CSPDNs and PSPDNs based on Recommendation T.70.

X.92

Hypothetical reference connections for public synchronous data networks.

X.37

Brief Listing of Further Examples, cont. X.96

Call progress signals in public data networks.

X.110

International routing principles and routing plan for public data networks.

X.115

Definition of address translation capability in public data networks.

X.116

Address translation registration and resolution protocol.

X.123

Mapping between escape codes and TOA/NPI for E.164/X.121 numbering plan interworking during the transition period.

X.130

X.131

X.134

Call processing delays in public data networks when providing international synchronous circuitswitched data services. Call blocking in public data networks when providing international synchronous circuit-switched data services. Portion boundaries and packet-layer reference events: Basis for defining packet-switched performance parameters.

X.135

Speed of service (delay and throughput) performance values for public data networks when providing international packet-switched services.

X.136

Accuracy and dependability performance values for public data networks when providing international packet-switched services.

X.137

Availability performance values for public data networks when providing international packet-switched services.

X.138

Measurement of performance values for public data networks when providing international packetswitched services.

X.139

Echo, drop, generator, and test DTEs for measurement of performance values in public data networks when providing international packetswitched services.

X.140

General quality of service parameters for communication via public data networks.

X.141

General principles for the detection and correction of errors in public data networks.

X.144

User information transfer performance parameters for data networks providing international Frame Relay PVC service.

X.145

Performance for data networks providing international Frame Relay SVC service.

X.150

Principles of maintenance testing for public data networks using data terminal equipment (DTE) and data circuit-terminating equipment (DCE) test loops.

X.160

Architecture for customer network management service for public data networks.

X.161

Definition of customer network management services for public data networks.

X.162

Definition of management information for customer network management service for public data networks to be used with the CNMc interface.

X.163

Definition of management information for customer network management service for public data networks to be used with the CNMe interface.

X.180

Administrative arrangements for international closed user groups (CUGs).

X.181

Administrative arrangements for the provision of international permanent virtual circuits (PVCs).

X

Jim Gettys of Digital Equipment Corporation (DEC) to provide a user interface for the Athena Project. It has been further developed by The X Consortium and is now trademarked and managed by The Open Group. See Athena project, X Window System. X Window System User Interface Toolkit XUI. A suite of utilities that facilitates the implementation of user interfaces for hardware platforms installed with the X Window System. See X Protocol, X Window System. X9 standards An important set of standards defined by the American National Standards Institute (ANSI) for the financial industry. The X9 standards cover such aspects as personal identification number (PIN) management, electronic transfer of funds, transaction processing, security mechanisms. A brief summary of some of the X9 security-related standards includes Title

Description

X9.9

U.S. wholesale banking standard for transaction authentication.

X9.17

Financial Institution Key Management standard for wholesale transactions. Defines protocols for the transfer of encryption keys using symmetric techniques.

X9.30

U.S. standards for digital signatures based upon the Digital Signature Algorithm (DSA) using the SHA-1 hash algorithm.

X9.31

U.S. standards for digital signatures based upon the RSA algorithm based upon the MDC-2 hash algorithm.

X9.57

Certificate management encryption schemes.

X9.42

A draft standard for key agreement based upon the Diffie-Hellman algorithm.

X9.44

A draft standard for key transport based upon the RSA algorithm.

See RSA Security Inc. X.25 A widely implemented, significant, connectionoriented, packet-based communications protocol used in local and wide area networks. The protocol was developed in the mid-1970s, when analog networking over noisy copper connections was optimized for voice rather than data communications. It helped to fulfill a growing need for a common language to interconnect local area networks that often used proprietary network protocols and for error mechanisms that could overcome the problems associated with marginal connections. In 1976, the CCITT (now the ITU) recommended X.25 for international data exchange. It was approved and subsequently revised every 4 years or so.

In general, X.25 is a three-layer model that includes a physical level, a link level, and a packet level that are, in turn, associated with the lower physical, data, and network layers of the hierarchical Open Systems Interconnect (OSI) model.

Basic Overview of X.25 Levels Name

Level #

Description

Physical 1 The electromechanical, procedural, and functional interfaces between the data terminal equipment (DTE) and the data circuit-terminating equipment (DCE). This level is specified by ITU-T X and V Series Recommendations that apply to modems and interchange circuits (e.g., X.21). Link

2 Also called the frame level, the link level ensures reliable data transfer between the DTE and the DCE in an efficient, timely manner. It synchronizes transmitter/receiver interactions, and detects and handles errors. A number of link access protocols may be implemented at the link level.

Packet

3 Also called the network level, the packet level creates the network data “chunks” with appropriate control/ error information and user data payload. Various virtual circuit (VC) and datagram services are handled at this level.

Data is formatted into X-25 data packets by ‘packetizing’ the data into smaller ‘chunks’ and adding the appropriate protocol information into the header of each packet. Error mechanisms are also included to enable retransmission if packets are lost, to provide a mechanism for reliable transfer. X-10 Protocol A protocol for sending radio frequencies (RF) signals over power line carriers (PLCs). In other words, a radio frequency-emitting device can be plugged into a wall socket and the protocol will enable device control signals to be sent through the wiring (over the alternating current power curve) to compatible devices set to the same settings as the controlling devices. Lately, wireless X-10-compatible transmitters are being added to commercial catalogs, with transmission ranges of up to about 100 feet. The X-10 Protocol and compatible components were introduced in the late 1970s and since the 1990s, when electronic devices significantly dropped in price, have become very popular for configuring home and small office automation systems. The basic X-10 categories of components are

transmitters, receivers, and controllers (which are transmitters with extra features). The controllers can be AC-outlet devices that intercept and relay signals or can be infrared or radio signal-based remote controls. The transmitters are a variety of motion detectors and audio or video transmitters, and the receivers are responding devices such as outlet controllers (for turning on lamps, appliances, or VCRs) or chimes. Together the various types of components can be interfaced through wireless signals and building wiring to control lamps, motion detectors, chimes, video cameras, and infrared devices through standalone controllers or computer software serial links. X-10 systems are relatively easy to install, although it can take some time to work out code correspondences and individual unit setup parameters if many components are used. It is also important to make sure batteries are fresh and components are turned on (some have on/off switches) if they are being used in a security system. In fact, with X-10 systems, redundancy is sometimes a good idea. There are computer interfaces and utility software packages for controlling X-10 systems and these offer much more power and flexibility than noncomputer systems, including testing, scheduling, macro scripts, and much more. The trend in X-10 components has been to become smaller and more streamlined (e.g., socket rocket light bulb controllers are now smaller than earlier designs). There are also new varieties of small, color, wireless transmitting video cameras that can be installed to cycle through in series with a remote control especially designed for this purpose. This is an important protocol in terms of its potential for data communications in ‘smart houses,’ that is, houses with a high degree of automation built in. There is the potential to design X-10-controllable motors that could be used to pull curtains, lower viewing screens, tip the dog food box over the bowl, lower the boat onto the floor in the garage, spin the mobile over the baby’s crib at varying speeds, and much more. As far as commercial products go, we’ve only seen the tip of the iceberg so far. See CEBus, LONWORKS. X-10 Power Line Analyzer A commercial tool for helping to install and troubleshoot X-10 systems. It is a handheld device that plugs into a standard 110 AC outlet or can be connected with jumper leads. The two-line text LCD display indicates status. It’s simpler to use and more appropriate than an oscilloscope for most X-10 needs. It enables signal quality and interference to be assessed, both of which may cause problems with the reliable functioning of X-10 components. See X-10 Protocol. X-band An assigned spectrum in the microwave frequencies of approximately 8 to 12 GHz with wavelengths of just a few centimeters. X-band signals are not significantly hindered by the Earth’s atmosphere unless a lot of moisture (e.g., rain) is present. X-band frequencies are used by military satellites and deepspace vehicles. See band allocations for a chart of assigned frequencies.

X-Bone A system designed to facilitate and automate the rapid deployment and management of multiple overlay networks. X-Bone is an overlay technology combined with teleconferencing-style coordination and management tools. X-Bone provides a virtual networking infrastructure that is configurable. While X-Bone is intended to be implemented with networks running more advanced systems, such as IPv6, some of the automatic tunneling services can be deployed to a limited extent on IPv4 systems. See 6bone, Mbone, overlay network, X-Bone xd. X-Bone xd An X-Bone directory tool for performing a number of tasks including the coordination of resource sharing at the local site, the support of local daemons through authentication, configuration, and creation of IP-encapsulation tunnels between daemons, and the provision of a user interface and API for users or programs wishing to manually parameterize and override overlays. See X-Bone. X-dimension of recorded spot In facsimile transmissions, a means of describing variation density in terms of the minimum density. The largest centerto-center space between recorded spots is measured in the direction of the recorded line. This can also be assessed perpendicular to the recorded line as the Y-dimension of a recorded spot. The same principles can be applied to assess the scanning spot. X-ray A radiant energy within the spectrum of high energy, invisible, ionizing electromagnetic radiation that ranges about 0.08 nm in wavelength, between ultraviolet light and gamma rays. X-rays were somewhat naively and irresponsibly used in early radio signal experiments, and for extended imaging inside objects and humans. These practices are now used with great care due to the damaging influence of Xrays on living cells. X-rays are used in many medical, industrial, and fabrication applications. See Xray goniometer; Roentgen, Wilhelm Konrad. X-ray goniometer An instrument for determining the position of the axes in a quartz crystal. X-rays are aimed at the atomic planes of the crystal and the reflected rays are evaluated. Since crystals are physically manipulated to alter their oscillating properties and often cut in very thin slices, it is important to know the orientation of the crystalline structure before cutting. See quartz, X cut, Y cut. X-ray spectrometer An instrument that is used, by means of reflected rays and evaluation of the resulting diffraction angles, to study the characteristics and composition of materials, including crystals. See Xray goniometer. X/Open A global, independent organization of computer manufacturers founded in 1984. X/Open seeks to promote an open, multivendor Common Applications Environment (CAE) to enhance application portability. This is a good concept, as it allows software developed by different vendors to run on a variety of platforms, leaving the choice of equipment up to the individual purchaser. See Common Applications Environment, Open Systems Interconnection. X/Open Federated Naming A naming mechanism from the X/Open group for developers to access

X

network naming services and to provide integration with industry-accepted naming services such as X.500, Domain Name Service (DNS), DCE, and others. X/Open Portability Guide XPG. A guide documenting the X/Open common applications environment system. XA extended architecture. XA-SMDS See Exchange Access SMDS. Xanadu, Project Xanadu A unified interconnected document storage/access/retrieval/publishing environment. Designed over a period of decades, Nelson, the author, has entitled this a docuverse. The Xanadu scheme is a write-once/keep-always system with a hypertext-like file structure. XAPIA X.400 Application Program Interface Association. See X Series Recommendations. Xaw The Athena Widget set. A set of widgets distributed with the X Window System, which began as Project Athena. See Athena, X Window System. Xbar abbrev. crossbar. XBase, Xbase A generic designation for applications that read and/or write dBase-compatible files. XC abbrev. cross connect. XCA extended communication adapter. Xcoral A multiwindow text editor for the X Window System, that can be used in conjunction with a mouse. XCVR abbrev. transceiver. xd See X-Bone xd. XDF extended distance feature. XDL An object-oriented extension to the ITU-T-defined Specification and Design Language (SDL) for telecommunications systems. See Specification and Design Language. XDMA Xing Distributed Media Architecture. A commercial streaming media architecture for delivery of live and on-demand audio-video from Xing Technology Corporation. It is built around standards such as TCP/IP and MPEG, and supports multicasting to multiple simultaneous users over local area networks (LANs) and wide area networks (WANs). XDMA can be implemented over ISDN networks for services such as news and distance learning. XDMCP X Display Manager Control Protocol. A protocol used to communicate between X terminals and UNIX workstations. XDR See External Data Representation. xDSL Generic term for a variety of digital subscriber line technologies, which include ADSL, EDSL, and HDSL. See digital subscriber line and individual listings for further information. XENIX A Unix implementation best known as being from the Santa Cruz Operation, Inc. (SCO), it was originally codeveloped by International Business Machines (IBM) and Microsoft as XENIX-11 for Intel machines. Microsoft had licensed UNIX from Bell Laboratories and developed it into XENIX for Digital Equipment’s PDP-11, the predecessor to the VAX line. XENIX-11 was popular on the 80286/ 80386 line in the late 1980s. SCO is now marketing

UnixWare 7. xerographic printer A printer that uses the same basic electrostatic mechanisms and techniques as a xerographic copier. The information is imaged onto a drum with lasers, the printing medium is passed across the drum and picks up the dry transfer toner, which then fuses the toner to the printing medium. See laser printer Xerox Corporation One of the first companies to see the commercial benefits of new photocopying technology developed by Carlson in the early 1940s. When still a relatively new, small company, Xerox took a chance on the new photocopying invention that had been passed up by other companies. Xerox is now known throughout the world for its technology, especially in the replication industry, and many people refer to all photocopies as “xeroxes.” See photocopy for further information and an illustration of Carlson’s patent. Xerox Network Services XNS. A multilayer, distributed file network architecture developed by the Xerox Corporation which is somewhat similar to TCP/IP. Unlike many networks from other vendors, XNS permits a user to use files and devices from a remote machine as if they were on a local machine. XNS functions compatibly with the third and fourth layers of the Open Systems Interconnection model (OSI). Xerox PARC Xerox Corporation’s Palo Alto Research Center. This research center provided enormous impetus to early computer companies and software developers (e.g., Apple Computer Inc., Microsoft Incorporated), especially those developing object-oriented systems and graphical user interfaces (GUIs). PARC researchers invented mice and various laser printing technologies, developed Smalltalk; they generated one good idea after another throughout the 1970s and early 1980s, yet surprisingly few of these were commercially implemented or marketed through Xerox. Charles Simonyi, one of the early founding members of PARC, was the demonstrator of the Alto, a pioneer desktop computer that inspired many of those fortunate enough to see it in the early days. Later, Simonyi was hired by Microsoft to move the company into graphical applications. XFN See X/Open Federated Naming. XFR abbrev. transfer. XFS X11 File System. XGA 1. See extended graphics adapter. 2. See extended graphics array. XID exchange identification. In data networking, XIDs are request and response packets exchanged prior to communications between a router and a network host. XID is used for device discovery, address conflict, resolution, and sniffing. The XID packet includes the parameters of the serial device, and a connection can only be negotiated if this configuration is recognized by the host. XIP abbrev. execute in place. A means to access memory and execute code on PCMCIA cards without having to load them into system memory first. See PCMCIA.

XIWT See Cross-Industry Working Team. Xlib X Library. A program interface for the X Windows System. Xmission abbrev. transmission. Xmit abbrev. transmit. XML See Extensible Markup Language. XModem A widely used error-correcting file transfer data transmissions protocol developed by Ward Christensen in the late 1970s. XModem utilizes 128byte packets, so files of various lengths will be padded to adjust the packet length and may be longer than the original file. The filename is not sent with the transmission. YModem, a successor to XModem, with support for longer data packets and file attributes, was developed by Chuck Forsberg. XModem is often used with computer modems to transfer files to and from bulletin board systems over traditional phone lines. XModem is not fast, but it has error correction and it’s reasonably reliable. It’s well supported, an important consideration since both ends of the connection have to agree on a protocol. Many service bureaus use XModem for file transfers, however, check if they have ZModem, which is faster and capable of restarting an interrupted transmission from where it left off. See Kermit, YModem, ZModem. XModem-1K, XModem-K A variant of XModem that manages data in 1K (1024-byte) packets. See XModem. XModem-CRC XModem with 16-bit cyclic redundancy checking (CRC) error detection mechanisms, instead of checksum. XModem-CRC can communicate with XModem versions that use checksum for error correction. XMP X/Open Management Protocol. XMS See Extended Memory Specification. XMT abbrev. transmit. XMTR abbrev. transmitter. XNMS MlCOM’s commercial IBM-licensed Intelbased desktop computer packet data network (PDN) network management system software. XNS See Xerox Network Services. XO abbrev. crystal oscillator. See crystal detector, quartz. XON/XOFF transmission on/transmission off. Common flow control signals used between two communicating devices or software programs, typically through modems. Since many transmissions media are inherently slow, there may be a delay between receiving a block of data and resuming transmissions. XON/XOFF signals allow the communicators to signal when to stop sending data and when to resume, in order to prevent loss or corruption. XON/XOFF is also known as software flow control. In newer high-speed modems, flow control may be handled by hardware, often in conjunction with specific types of cables. Flow control signals are not limited to modem communications. If a user is working on a terminal that understands XON/XOFF commands, usually signified by Ctrl-S (stop) and Ctrl-Q (resume), then it is possible to suspend a listing or other activity and

resume when it is convenient. This is a common way of preventing a screenful of text information from scrolling by so fast that it cannot be read in text windows that lack scroll bars for back-referencing. Xover abbrev. crossover. XPAD external packet assembler/disassembler. XPG See X/Open Portability Guide. XPM Extended Peripheral Module. Xponder transponder. Xpress Transport Protocol XTP. A flexible, highperformance commercial multicast protocol to support a wide variety of applications from wide area networks (WANs) to multimedia and realtime embedded systems. It was developed by an international group of representatives from academia, industry, and the government from 1987 to the early 1990s and was described by Strayer et al. in the early 1990s. It has been adopted as part of MIL-STD-2204 (Survivable Adaptable Fiber Optic Embedded Network). XTP brings together the functionality of UDP, TCP, and TP4, in addition to transport multicast, group management, Quality of Service (QoS) negotiation capabilities, rate and burst control, and error and flow control mechanisms. It is designed to operate over any network or datalink layer or may be implemented directly over an ATM AAL. It can run in parallel with other transport protocols and thus can increase functionality without giving up interoperability. It is expressly intended to separate the communication paradigm from error control policies. The protocol sparked interest in the development of a public domain version at Sandia National Laboratories. This protocol is distinct from the lightweight eXpress Transfer Protocol that was originally developed by Protocol Engines, Inc. See multicast, XTP Forum. XRB transmit reference burst. xref abbrev. cross reference. XRemote A serial transmission protocol for the X Window System. XRF Extended Recovery Facility. XSG X.25 Service Group. XSI X/Open System Interface Specification. XSMP X Session Manager Protocol. XT 1. abbrev. crosstalk. 2. See IBM Personal Computer XT. Xtal 1. abbrev. crystal. Xtal Set Society A society founded in 1991 for building and experimenting with radio electronics, particularly crystal radio sets. Xtalk abbrev. crosstalk. xterm A popular terminal emulator for the X Window System has been ported to several other operating systems. Xterm lets you have more than one terminal window active at a time through a single modem, each with its own input/output process running independently of the others. In other words, you can be reading Internet newsgroups in one window, interacting in an Internet Relay Chat (IRC) channel in another, and downloading binary files in a third at the same time, which is very convenient.

X

XTI X/Open Transport Interface. See X Window System. XTL See SunXTL. XTL API See SunXTL. XTL Provider Interface See SunXTL. XTL Provider Library See SunXTL. XTP 1. See eXpress Transfer Protocol. 2. See Xpress Transport Protocol. XTP Forum A nonprofit group promoting the development and distribution of Xpress Transport Protocol (XTP). A number of significant vendors, including Apple Computer, Hughes Aircraft, Lockheed Martin, Northrop-Grumman, Philips Research, and Silicon Graphics are involved in this effort, in collaboration with XTP Forum Research Affiliates from universities and military labs around the world. See Xpress Transport Protocol. XUI See X User Interface Toolkit. XWA The callsign issued to a historically significant Canadian radio station, it stood for X-perimental Wireless Apparatus. XWA was issued its first experi-

mental license by the Department of Naval Service, in 1918, following about 3 years of discussion (and presumably some preliminary experiments). The first general broadcast licence was issued in September 1919 to XWA as part of the Marconi Wireless Telegraph Company. Broadcasts apparently began in December 1919. The pioneer broadcasts were primarily musical and, since few consumer radios existed at the time, the listeners were amateur radio enthusiasts. In May 1920, XWA aired its first regularly scheduled broadcast and the radio industry evolved quickly, with XWA becoming station CFCF in November 1920. See CFCF, radio history. XWindows, XWS See X Window System. XXXX A designation for the last four digits in a telephone number, usually used when the numbers are not yet known (or assigned). It represents any number between 0 and 9. XY cut A means of angle-cutting a piezoelectric crystal so its electrical characteristics are between those of an X cut and a Y cut. See quartz, X-ray goniometer, X cut, Y cut.

Telecommunications THE

I L L U S T R AT E D D I C T I O N A R Y

Appendixes A. Telecommunications Timeline B. Asynchronous Transfer Mode (ATM) Information C. ITU-T Series Recommendations D. List of World Wide Web Search Engines E. List of Internet Domain Name Extensions F. List of Request for Comments (RFC) Documents G. Bibliography H. Acronyms and Abbreviations I.

Area Codes (North American Numbering Plan)

J. Dial Equiv., Radio Alphabet, International Morse Code, Metric Prefixes/Values K. ASCII Character and Control Codes

Telecommunications Timeline Essential Concepts and Early Engineering

~2970 B.C. The great step pyramids are designed and engineered in Egypt, possibly by Imhotep. ~1650 B.C. Ahmose transcribes Egyptian mathematics which include fractions. ~670 B.C. Thales engages in abstract and deductive mathematics and investigates magnetism. ~500 B.C. Pythagoras and the Pythagoreans make important contributions to mathematics and the study of sound frequency relationships. ~260 B.C. Archimedes establishes many important, basic principles of physics. ~800 The concept of zero is used in mathematics in Asia. 1200s Fibonacci authors Liber Abaci (Book of the Abacus) in which he promotes the use of Arabic numerals and positional notation. 1400s Gutenberg develops movable type, thus ringing in the age of mass-produced books and the publishing industry. Copernicus studies celestial movements and relationships, and develops concepts that challenge accepted notions of the Earth in the cosmos. 15/1600s Galileo makes important observations of the laws of physics, especially of gravity and bodies in motion. 1600s Robert Boyle studies physical properties and the compression of air, resulting in Boyle’s law, sometimes called Marriotte’s law due to parallel studies in France. late 1600s Sir Isaac Newton makes important observations about basic physical laws, now widely known as Newtonian physics or classical physics. These highly significant discoveries form the basis of modern physics. 1676 Ole (Olaf) Røhmer calculates the velocity of light as a constant 227,000 kilometers/second. 1724 Daniel Fahrenheit reports his new temperature scale to the Royal Society. 1900 Max Planck states quantum theory. 1905 Albert Einstein publishes a paper on the special theory of relativity. Physics and Basic Electronics Technology

1738

Bernoulli writes on the relationship of pressure and the velocity of fluids, now known as Bernoulli’s principle, used in vacuum technology. mid-1700s Benjamin Franklin conducts numerous experiments with electricity, inspires other scientists, and coins many terms associated with the emerging science. 1700s Luigi Galvani studies electromagnetism and its effects in living tissue. 1775 Alessandro Volta invents the electrophorus, the basis of subsequent electrical condensers, replacing the Leyden jar. 1800 Alessandro Volta invents the voltaic pile, a pioneer wet cell. 1800s Ritter discovers ultraviolet light. 1807 J. B. J. Fourier announces Fourier’s theorem, which forms the basis for Fourier transforms, now widely used as analytical tools in mathematics. Humphry Davy uses battery power to separate out and discover potassium and, about a decade later, invents an arc lamp (arc lamps were also invented by others). 1819 H. C. Ørsted demonstrates the relationship of electricity and magnetism. 1820 A. M. Ampère studies the mathematical characteristics of electromagnetism and announces the right-hand rule. 1826 J. N. Niepce develops a primitive type of photography. 1829 L. J. Daguerré develops one of the first permanent photographs - the daguerréotype. 1832 Michael Faraday publishes Faraday’s laws of electrolysis. 1877 The microphone is invented by David Hughes. 1878 The first telephone exchange is established in London. 1879 American Telephone & Telegraph is founded based on the technology in the Bell patents, later to be known as AT&T.

1891 1904

1910 1911 1915 1920 1921 1927 1928 1957 1972

Almon B. Strowger invents the automatic telephone switching system so subscribers can dial the desired number, rather than calling a human operator. Fleming releases the two-element Fleming tube, which leads to de Forest’s development of the three-element tube. Lee de Forest invents the Audion leading to the evolution of three or more element vacuum tubes that revolutionize the electronics industry. R. A. Fessenden broadcasts the first voice and music broadcasts, using an Alexanderson alternator to supply the power. The Computing-Tabulating-Recording Company is founded, later to become International Business Machines (IBM). Wireless communications are established between the United States and Japan. The Radio Corporation of America (RCA) is founded. The historic KDKA radio station begins broadcasting, having moved out of Frank Conrad’s garage. John Logie Baird carries out pioneer television broadcasting experiments. Scheduled television broadcasts are begun by station WGY in New York state. Bell Laboratories develops pioneer color television technologies. The Russian Sputnik communications satellite is launched into orbit. The Canadian ANIK satellite becomes the first domestic television broadcast communications satellite.

Communications Applications

1774 1795 1836 1837 1838 1843 1848 1856 1858 1861

1866

1872 1874 1876 1878 1886 1880 1889 1895/96 1920s

Lesage created the frictional telegraph. F. Salvà i Campillo describes a system for an electric telegraph, which he constructed in 1804 by incorporating Alessandro Volta’s ca. 1800 invention of the voltaic pile. C. Wheatstone and W. Cooke’s first practical implementation of the telegraph. Samuel Morse received approval and funding from the U.S. Congress to build a Washington, D.C. to Baltimore telegraph line. Samuel Morse and Alfred Vail demonstrate a telegraph to the President. Samuel Morse transmits historic “What God has wrought?” message which launches the age of the practical, commercial telegraph. The laying of the first transatlantic telegraph cable. It only lasted a few days. David Hughes translates telegraph signals into letters. Introduction of the Pony Express. The first transcontinental telegraph line is built in a record four months. At the line’s completion in October, the Pony Express ceased operations. P. Reis demonstrates the transmission of tones through wire. The laying of the first successful installation of a transatlantic telegraph cable. This revolutionizes communications. Previously, sea voyages of two or three months were necessary to ‘transmit’ overseas messages. A. Loomis demonstrates essential basics of wireless radio wave transmissions. Loomis patents wireless telegraphic technology. James Clerk-Maxwell publishes an important paper on electromagnetic wave theories. Elisha Gray submits a caveat to the U.S. patent office after Alexander Graham Bell submits a patent for the ‘harmonic telegraph,’ the precursor to the telephone. Bell reports having spoken intelligibly over wires to his assistant, Watson. Public telephones make their commercial debut in Connecticut. A. Dolbear receives a patent for induction-based wireless telegraphy. Bell Telephone is incorporated in Canada. The Creed high-speed automatic telegraph system is developed. A. S. Popow demonstrates wireless telegraphy from ship to shore in Russia. Bell Laboratories begins transmitting picture phone images. Various types of facsimile transmissions are implemented by different inventors.

Communications Applications, cont.

1947 1956 1967 1969 1980 1983 1989 1990

Bell Laboratories scientists invent the transistor. Bell demonstrates Picturephone technology to the Institute of Radio Engineers. The concept and design of the ARPANET are born. The ARPANET is put into operation. T. Berners-Lee develops Enquire hyptertext system. The ARPANET is split into Milnet and ARPANET, the precursor to the Internet. T. Berners-Lee develops a Web browser. The ARPANET is officially discontinued, because it has evolved into the Internet.

Tabulating Machines, Computers, and Microcomputers B.C.

1600s 1623 1642 1673 1674 1786 1822 1834 1853 1928 1930 1936 1937 1937 1943 1946 1949 1951 1971 1972 1973 1974 1975 1976 1980 1983 1985 1995

In many parts of the world, from the Americas to Asia, counting systems arise. The Native Americans use grains, Eastern cultures use sand, clay, counting sticks, and beads, eventually evolving many different forms of the abacus. By this time, in Western Europe, the slide rule as we know it is being used, evolving from a number of different sliding tabulating systems. Wilhelm Schickard invents the first calculating machine. Blaise Pascal independently invents a different type of calculating machine. René Grillet develops a general adding machine. Leibnitz develops a calculating machine. J. H. Muller publishes ideas for automatic ‘difference engines.’ Charles Babbage develops important historic models for ‘different engines.’ Charles Babbage develops the concept of an ‘analytical engine.’ Technology has not yet developed to the point where his ideas can be fully carried out, but the design concepts are sound. The Scheutzes undertake the construction of an automatic ‘different engine.’ Punch card equipment is put into use for storing information from calculators in Germany. V. Bush’s idea for a difference analyzer is constructed at the Massachusetts Institute of Technology (MIT). Konrad Zuse applies for a patent for ‘mechanical memory.’ John Atanasoff conceives the Atanasoff-Berry Computer (ABC). Howard Aiken teams up with IBM to produce the Harvard Mark 1, which became operational six years later. The ENIAC project is initiated and is partly operational a year later and fully operational by 1945. Eckert and Mauchly form the Electronic Control Company. Edmund C. Berkeley authors Giant Brains or Machines that Think describing the construction of a ‘personal computer.’ He designed and built Simon, GENIAC, and many robots. The UNIVAC is put into service at the U.S. Census Bureau. The Kenbak-1 desktop computer is advertised in the September issue of Scientific American. Bill Gates and Paul Allen partner for various business ventures, forming Traf-O-Data, which eventually evolves into Microsoft Corporation. The Alto ‘minicomputer’ blazed trails at Xerox PARC. It later served as inspiration to Apple Computer and Microsoft, who eventually incorporated the graphical interface ideas into the Macintosh and Windows lines of products. The Altair 8800 is released and subsequently featured in the January 1975 issue of Popular Electronics. The Altair 680 Motorola MC6800 computer is released. Radio Shack ships the TRS-80 Model I. Apple Computer is formed by Steven Jobs and Stephen Wozniak. International Business Machines releases its Personal Computer line of products. The Apple Lisa, forerunner of the Macintosh line that came out a year later, is released. The Atari ST and Amiga 1000 computers equipped with sound and graphics are released. Jean-Louis Gassé’s team releases the Be Operating System and computer.

Asynchronous Transfer Mode (ATM) Information asynchronous transfer mode ATM. ATM is a highly significant protocol due to its flexibility and widespread use for Internet connectivity. It is a highspeed, cell-based, connection-oriented, packet transmission protocol for handling data with varying burst and bit rates. ATM evolved from standardization efforts by the CCITT (now the ITU-T) for broadband ISDN (B-ISDN) in the mid-1980s. It was originally related to Synchronous Digital Hierarchy (SDH) standards. ATM allows integration of local area network (LAN) and wide area network (WAN) environments under a single protocol, with reduced encapsulation. It does not require a specific physical transport, and thus can be integrated with current physical networks. It provides virtual connection (VC) switching and multiplexing for broadband ISDN, to enable the uniform transmission of voice, data, video and other multimedia communications. Two methods for carrying multiprotocol connectionless traffic over ATM are routed and bridged Protocol Data Units (PDUs). Routed PDUs allow the multiplexing of multiple protocols over a single ATM virtual circuit through LLC Encapsulation. Bridged PDUs carry out implicit higher-layer protocol multiplexing through virtual circuits (VCs). ATM employs fixed-length cells consisting of an information field and a header. The information field is transparent through the transmission. The U.S. and Japan proposed the use of 64-byte cells, and Europe proposed 32-byte cells. As a consequence of the dis-

crepancy, 48-byte cells are favored by many as a compromise. Charts and simplified diagrams on the following pages show an ATM system through user input and reception of a variety of media, including voice, video, and data. The data are inserted and extracted by the ATM adaptation layer (AAL) into a logical package called a payload which makes up part of the ATM cell. The ATM layer, in turn, adds or removes a five-byte header to this payload, and the physical layer converts the information into the appropriate format for transmission, which may extend over large areas and pass through other networks switches and routers. The physical layer is comprised of two sublayers, the physical medium (PM) sublayer and the transmission convergence (TC) sublayer. See dic– tionary entries for Ethernet, frame relay, HIPPI, TCP/ IP. ATM cell The ATM cell is the basic unit of information transmitted through an ATM network. An ATM cell has a fixed length of 53 bytes, consisting of a 48-byte payload (the information being transmitted) and a 5-byte header (addressing information). Interpretation of the signals from different types of media into a fixed length unit of data makes it possible to accommodate different types of transmissions over one type of network. There are a number of important traffic flow control, congestion management, and error-related concepts related to ATM, including those listed in the ATM Cell Rate Concepts chart shown on page 1038.

ATM Cell Header and Payload Format ||<Payload>| +----------+---------+-----------------+--------------------+----/----+ |VCI Label | control | header checksum | option. adaptation | payload | | 3 bytes | 1 byte | 1 byte | layer 4 bytes | 44 or 48| +----------+---------+-----------------+--------------------+----/----+

ATM Cell at the User Network Interface (UNI) Item

Abbrev.

Num. bits Notes

cell loss priority

CLP

1 bit

Cell loss priority of ‘1’ is subject to discard, without violating agreed upon quality of service (QoS). If CLP is ‘0,’ resources are allocated.

generic flow control

GFC

4 bits

Point-to-point and point-to-multipoint. The field appears at the user network interface.

ATM adaptation layer AAL. In ATM, a set of ITU-T-recommended, service-dependent layer types interface the user to the ATM layer. The AAL is the top of three layers in the ATM protocol reference model. Higher layer services are translated through one or more ATM cells. AAL0 to AAL5 perform a variety of connection, synchronization, segmentation,

Layer Name

Abbrev.

ATM adaptation layer 0

AAL0

ATM adaptation layer 1 ATM adaptation layer 2 ATM adaptation layer 3/4 ATM adaptation layer 5

ATM adaptation layer 6

and assembly functions for adapting different classes of applications to ATM. Within the AAL, information is mapped between the PDUs and ATM cells. Upon creation of a virtual connection (VC), a specific AAL is associated with that connection. See the following diagrams for the relationships of the adaptation layers to the ATM format.

Description

A layer implementation intended to provide a direct connection between the user and the ATM. It is limited in that it provides no service guarantee mechanisms. It is recent and rarely used, except in proprietary, standalone systems. Nevertheless, some standard commercial drivers support AAL0. AAL1 A constant rate service level. It is useful for time-sensitive applications such as voice, video, and circuit emulation. AAL2 A variable rate service. It is rarely used. AAL3/4 A variable rate service. It is the most comprehensive of the adaptation layers, and was originally specified as separate AAL3 and AAL4 for connectionless and connection communications. AAL5 A variable rate service similar to AAL3/4. It is sometimes called SEAL for Simple and Efficient Adaptation Layer. It is widely used, especially in TCP/IP implementations. This is a nonassured service, and retransmission must be accomplished by higher-level protocols. It specifies a packet with a maximum size of 64K minus 1 octets. AAL6 A recent addition, designed to accommodate demand for some of the recent multimedia, high-bandwidth applications.

For further information related to ATM adaptation layers, see RFC 1483, RFC 1577, RFC 1626.

ATM models Because of the great variety of needs in the networking community, many types and implementations of ATM networks have been developed. Information on some of the more common and emerging models is

shown in the ATM Models chart. For further details on specific models, see dictionary entries under ATM Transition Model, Classical IP Model, Conventional Model, Integrated Model, Peer Model.

ATM Models and Test Systems of Interest Model

Notes

Classical IP over ATM

A model for enabling compatible, interoperable implementations for transmitting IP datagrams and ATM address Resolution Protocol (ATMARP) requests and replies over ATM adaptation layer 5 (AAL5). LLC/SNAP encapsulation of IP packets. IP address resolution to ATM addresses via an ATMARP service within the LIS. One IP subnet is used for many hosts and routers. Each virtual connection (VC) directly connects two IP members within the same LIST. TCP/IP applications. See RFC 1577.

IP Broadcast over ATM

An IP multicast service in development by the IP over ATM Working Group for supporting Internet Protocol (IP) broadcast transmissions as a special case of multicast. See RFC 2022, RFC 2226.

IP Multicast over ATM MLIS

Internet Protocol (IP) multicasting over Multicast Logical IP Subnetwork (MLIS) using ATM multicast routers. A model developed to work over the Mbone, an emerging multicasting internetwork. It is designed for compatibility with multicast routing protocols such as RFC 1112 and RFC 1075.

LANE

Local Area Network (LAN) Emulation. Protocol-independent applications aid in the transition from legacy internetworks to ATM.

Native ATM API

ATM-specific applications which take advantage of its quality of service (QoS) capabilities.

Test Model

Notes

ATM over DS3

An experimental testbed network called XUNET II running at 45 Mbps to connect FDDI networks at eight sites across the continental U.S. from coast to coast. Internet Protocol routers at each site forward packets between connected local area networks (LANs) and long-distance DS3 links. The production version transmits IP datagrams over a PVC mesh fabric, with a single virtual circuit (VC) between each pair of routers.

Multicube

An approach to the implementation of IP Multicast over ATM proposed by Schulzrinne et al. Multicube is a project to develop, test, and validate an ATM-based multipoint infrastructure for supporting CSCW applications. The majority of the multicast applications of endusers involved in the project are Internet Protocol (IP) based.

ATM Cell Rate Concepts At its heart, ATM is concerned with moving and directing traffic; cells must be directed (and sometimes even discarded) such that signals, priority levels, and data are effectively transmitted and balanced with respect to the needs at hand. There is no single best way to ‘tune’ a network. The settings will vary, depending upon the system, the time of day, the quan-

tity and priority levels of users, and many more subtle factors that are not necessarily known in advance. Thus, there have been a number of basic cell rate concepts defined for system installers and administrators to assess and ‘tweak’ their systems for optimum information flow without loss. Some of the more important concepts are summarized here.

ATM Cell Rate Concepts Abbrev. Name

Notes

ACR

allowed cell rate

A traffic management parameter dynamically managed by congestion control mechanisms. ACR varies between the minimum cell rate (MCR) and the peak cell rate (PCR).

CCR

current cell rate

Aids in the calculation of ER and may not be changed by the network elements (NEs). CCR is set by the source to the available cell rate (ACR) when generating a forward RM-cell.

CDF

cutoff decrease factor

Controls the decrease in the allowed cell rate (ACR) associated with the cell rate margin (CRM).

CIV

cell interarrival variation

Changes in arrival times of cells nearing the receiver. If the cells are carrying information that must be synchronized, as in constant bit rate (CBR) traffic, then latency and other delays that cause interarrival variation can interfere with the output.

GCRA

generic cell rate algorithm

A conformance enforcing algorithm that evaluates arriving cells. See leaky bucket.

ICR

initial cell rate

A traffic flow available bit rate (ABR) service parameter. The ICR is the rate at which the source should be sending the data.

MCR

minimum cell rate

Available bit rate (ABR) service traffic descriptor. The MCR is the transmission rate in cells per second at which the source may always send.

PCR

peak cell rate

The PCR is the transmission rate in cells per second which may never be exceeded. It characterizes the constant bit rate (CBR).

RDF

rate decrease factor

An available bit rate (ABR) flow control service parameter that controls the decrease in the transmission rate of cells when it is needed. See cell rate.

SCR

sustainable cell rate

The upper measure of a computed average rate of cell transmission over time.

UBR

unspecified bit rate

An unguaranteed service type in which the network makes a best efforts attempt to meet bandwidth requirements.

VBR

variable bit rate

The type of irregular traffic generated by most non-voice media. Guaranteed sufficient bandwidth and QoS.

International Telegraph Union (ITU-T) Recommendations Over the decades since its inception, the ITU has been developing international guidelines to promote compatibility and interoperability of communications systems, from the original telegraph to modern mobile communications systems. These guidelines are available as publications from the ITU-T for purchase over the Internet and many in the A Series are downloadable without charge from the Web. Since ITU-T specifications and recommendations are widely followed by vendors in the telecommunications industry, those wanting to maximize interoperability with other systems need to be aware of the information disseminated by the ITU-T. The list below describes the general overall categories and specific series topics are listed under individual entries in this dictionary, e.g., B Series Recommendations. Note that some series topics include only a few documents, while others, such as the G Series Recommendations, include many hundreds of documents and thus some sections may be summarized, or described with examples. Note also that the author has taken time to categorize many of the documents, which can sometimes be difficult to locate in a numerical-only list, to aid the reader in finding the appropriate document and understanding the depth and breadth of the publications.

ITU-T Recommendations General Categories Series A

Organization of the work of the ITU-T

Series B

Means of expression: definitions, symbols, classification

Series C

General telecommunications statistics

Series D

General tariff priniciples

Series E

Overall network operation, telephone service, service operation, and human factors

Series F

Telecommunication services other than telephone

Series G

Transmission systems and media, digital systems and networks

Series H

Audiovisual and multimedia systems

Series I

Integrated Services Digital Networks (ISDN)

Series J

Transmission of sound program and other multimedia signals

Series K

Protection against interference

Series L

Construction, installation, and protection of cables and other elements of outside plant

Series M TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile, and leased circuits Series N

Maintenance: international sound program and television transmission circuits

Series O

Specifications of measuring equipment

Series P

Telephone transmission quality, telephone installations, local line networks

Series Q

Switching and signaling

Series R

Telgraph transmission

Series S

Telegraph services terminal equipment

Series T

Terminals for telematic services

Series U

Telegraph switching

Series V

Data communication over the telephone network

Series X

Data networks and open system communication

Series Y

Global information infrastructure and Internet protocol aspects

Series Z

Programming languages

World Wide Web Major Search Engines Name

AltaVista

URL (Web Address)

Notes

http://www.altavista.com/

Extensive searching, advanced search parameters, priority ranking. First introduced by Digital Equipment in 1995. c|net Search http://www.search.com/ Perhaps best known for its large repository of software updates, shareware, and public domain software, c|net also provides a Web search engine that displays a short list and enables users to look at further selections, if desired. DejaNews http://www.dejanews.com/ A huge archive of the posts to various USENET newsgroups. A remarkable record of public con(now http://groups.google.com/) versations online, searchable by keywords or author. This has now been acquired by Google. DogPile http://www.dogpile.com/ Looking for a short, targeted list of hits? Try this search engine. It also includes category searches and stores. Excite http://www.excite.com/ General search, weather, stocks. Google http://www.google.com/ Fast, extensive, with a lovely simple, uncluttered interface. Also lists USENET group postings as Google Groups (acquired from DejaNews). i-Explorer http://www.i-explorer.com/ Search in popular, general interest categories. InfoSeek http://infoseek.go.com/ Web pages, newsgroups, and individuals. InfoSpace http://www.infospace.com/ Personal and business listings, maps, etc. Inktomi http://inktomi.berkeley.edu/ Fast distributed searchable database from the University of California at Berkeley. LinkStar http://www.linkstar.com/ Business directory search. Lycos http://www.lycos.com/ General searching, maps, and personal names from Carnegie Mellon University. Magellan http://www.mckinley.com/ Sites reviewed and rated by the McKinley Group, Inc. Sleuth http://www.isleuth.com/ The Internet Sleuth searches over 3,000 Internet databases. Selections can be found through general categories. (This may now be defunct.) Starting Point http://www.stpt.com/ Searches the Web and other Internet resources (selectable), includes advanced search capabilities. Switchboard http://www.switchboard.com/ Personal and business listings of names, addresses, and email addresses. Webcrawler http://www.webcrawler.com/ Quick, to-the-point listings. Yahoo http://www.yahoo.com/ An extensive service that includes a search engine and hundreds of topics organized under categories of interest. For further information from the publisher: For further information from the author:

http://www.crcpress.com/ http://www.4-sightmedia.com/

Internet Domain Name Extensions North America and Generic International .us .um .gov .mil .arpa .ca .mx .int

United States U.S., not commonly used United States Outlying islands U.S. government Local, state, and federal government agencies U.S. military Military agencies, bases ARPANET Advanced Projects Research Agency Canada United Mexican States international

.com .biz .pro .info .net .org .edu .museum .aero

commercial business professional information network organization education museums aeronautics

Central and South America .ag .ar .aw .bb .bz .bm .bo .br .cl .co .cr .cu .dm .do .ec .sw .fk .tf .gd .gp .gt .gy .gf .ht .hn .jm .mq .ms .ni .pa .py .pe .pr .kn .lc .vc

Antigua, Barbuda Argentine Republic Aruba Barbados Belize Bermuda Bolivia Brazil Chile Colombia Costa Rica Cuba Dominica Dominican Republic Ecuador El Salvador Falkland Islands (Malvinas) French Southern Territories Grenada Guadeloupe Guatemala Guyana Guyana (French) Haiti Honduras Jamaica Martinique Montserrat Nicaragua Panama Paraguay Peru Puerto Rico St. Kitts, Nevas St. Lucia St. Vincent, Grenadines

General business, services, suppliers Retail business, malls, electronic storefronts Doctors, lawyers, consultants, home care nurses, realtors, vets, carpenters Noninstitutional educational, informational Net related. Nonprofit, not-for-profit, charitable Schools, colleges, universities, other educational facilities Public and private repositories in many disciplines Airlines, aeronautical suppliers, contractors .gs .pm .sr .uy .ve

So. Georgia, So. Sandwich Islands St. Pierre, Miquelon Suriname Uruguay Venezuela

United Kingdom, Europe .gb .ie .im .uk

Great Britain Ireland Isle of Man United Kingdom

.al .ad .at .by .be .ba .bg .hr .cy .cz .dk .ee .fo .fi .de

Albania Andorra Austria Belarus Belgium Bosnia, Herzegovina Bulgaria Croatia Cyprus Czech Republic Denmark Estonia Faroe Islands Finland Federal Republic of Germany France France Germany Gibraltar Greece Greenland (Denmark) Guernsey Hungary

.fr .fx .de .gi .gr .gl .gg .hu

.is .it .je .lv .li

Iceland Italian Republic Jersey Latvia Liechtenstein, Principality of .lt Lithuania .lu Luxembourg, Grand Duchy of .mk Macedonia .mt Malta .md Moldova .mc Monaco .nl Netherlands .no Norway .pt Portuguese Republic .ro Romania .sm San Marino (Italy) .sk Slovakia .si Slovenia .es Spain .se Sweden .ch Switzerland .ua Ukraine .va Vatican City State .yu Yugoslavia Middle East .bh .ir .iq .il .jo .kw .lb .sa .tr .ae

Bahrain Iran Iraq Israel Hashemite Kingdom of Jordon Kuwait Lebanon Saudi Arabia Turkey United Arab Emirates

Internet Domain Name Extensions, cont. Eastern Europe, Middle Asia .af .al .am .az .bg .by .hr .ee .kz .kg .lv .lt .md .pl .ro .ru .rw .sk .si .tj .tm .ua .us

Afghanistan Albania Armenia Azerbaidjan Bulgaria Bielorussia Croatia Estonia Kazakhstan Kirgistan Latvia Lithuania Moldavia Poland Romania Russian Federation Rwanda Slovakia Slovenia Tadjikistan Turkmenistan Ukraine Union of Soviet Socialist Republics .uz Uzbekistan Mediterranean, Caribbean

.an .aw .cy .mt .lc Africa

Antilles (Netherlands) Aruba Cypress Malta Saint Lucia

.dz .ao .bj .bw .bv .bf .bi .cm .cw .cf

Algeria Angola Benin Botswana Bouvet Island Burkina Faso Burundi Cameroon Cape Verde Central African Republic Chad Comoros Congo Congo Republic Cote D’Ivoire Djibouti Egypt, Arab Republic of Equatorial Guinea Eritrea Ethiopia Gabon Gambia Ghana

.td .km .cd .cg .ci .dj .eg .gq .er .et .ga .gm .gh

.gn Guinea .gw Guinea Bissau .ci Ivory Coast .ke Kenya .ls Lesotho .lr Liberia .ly Libya .mg Madagascar .mr Mauritania .mw Malawi .ml Mali .mu Mauritius .yt Mayotte .ma Morocco .mz Mozambique .na Namibia .ne Niger .ng Nigeria .re Reunion .sn Senegal .sc Seychelles .sl Sierra Leone .so Somalia .za South Africa .sh St. Helena .sd Sudan .sz Swaziland .tz Tanzania .tg Togo .tn Tunisia .ug Uganda .eh Western Sahara .zr Zaire .zm Zambia .zw Zimbabwe Asia, South Pacific, Antarctic .bd .io .in .bt .kh .hk .jp .kp .kr .la .mo .my .mn .np .pk .cn .sg .kr .Ik

Bangladesh British Indian Ocean Territories India Bhutan Cambodia Hong Kong (Xianggang) Japan Korea (North) Korea (South) Laos Macau Malaysia Mongolia Nepal Pakistan People’s Republic of China Singapore South Korea Sri Lanka

.tw .th .to .vn

Taiwan Thailand Tonga Vietnam

.am .au .bn .ck .fj .gu .id .my .mh .fm .nz .nf .pw .pg .ph .pn .pf .ws .sb .tk .tv .wf

American Samoa Australia Brunei Cook Islands Fiji Guam Indonesia Malaysia Marshall Islands Micronesia New Zealand Norfolk Island Palau Papua (New Guinea) Philippines Pitcairn Islands Polynesia (French) Samoa Solomon Islands Tokelau Tuvalu Wallace, Futuna Islands

.pg

Antarctica

West Indies, Antilles .ai .ag .bb .bm .bs .ky .cu .dm .do .gd .gp .ht .jm .mq .pr .lc tc.

Anguilla Antigua and Barbuda Barbados Bermuda Bahamas Cayman Islands Cuba Dominica Dominican Republic Grenada Guadeloupe (French) Haiti Jamaica Martinique (French) Puerto Rico (U.S.) Saint Lucia Turks, Caicos Islands

.tt .vg .vi

Trinidad and Tobago Virgin Islands (British) Virgin Islands (U.S.)

Miscellaneous .aq .nt

Antarctica Neutral Zone

Request for Comments (RFC) Documents Request for Comments (RFC) documents are an essential resource for understanding the implementation, structure, format, and evolution of the Internet. There are over 3,000 of these documents and, unfortunately, not sufficient space here to list abstracts or even the titles of all the RFCs. Nevertheless, the following quick lookup summarizes some of the most important aspects and is a useful reference even if it only hits the highlights. The reader is encouraged to consult the many excellent RFC repositories on the Internet archived in various formats including ASCII, editable PostScript, Adobe PDF, and HTML. The RFCs themselves include references to related documents of interest. In addition to www.w3c.org, (for Web info) and www.rfc.net, some good Net archives of interest include http://www.armware.dk/RFC

Searchable, nicely formatted, forward and backward references

http://www.faqs.org/rfcs/

Searchable and shows authors, dates, and references in search results

http://www.nexor.com/index-rfc.htm

Searchable from a selection of archives, includes Perl 5 expressions and Title/Author/Keyword searching

http://www.cis.ohio-state.edu/cs/Services/rfc/index.html

Categorizations and lists and links to RFCs of particular interest

General RFC 1358 RFC 1796 RFC 1920 RFC 1925 RFC 1935 RFC 1941 RFC 1958 RFC 1999 RFC 2000 RFC 2014 RFC 2026 RFC 2028 RFC 2031 RFC 2125 RFC 2223 RFC 2360 RFC 2799 RFC 3000 RFC 3160

Charter of the Internet Architecture Board (IAB) Not all RFCs are Standards INTERNET OFFICIAL PROTOCOL STANDARDS The Twelve Networking Truths What is the Internet, Anyway? Frequently Asked Questions for Schools Architectural Principles of the Internet Request for Comments Summary RFC Numbers 1900-1999 INTERNET OFFICIAL PROTOCOL STANDARDS IRTF Research Group Guidelines and Procedures The Internet Standards Process - Revision 3 The Organizations Involved in the IETF Standards Process IETF-ISOC Relationship A Primer on Internet and TCP/IP Tools and Utilities Instructions to RFC Authors Guide for Internet Standards Writers Request for Comments Summary RFC Numbers 2700-2799 INTERNET OFFICIAL PROTOCOL STANDARDS The Tao of IETF - A Novice’s Guide to the Internet Engineering Task Force

Domain Name System (DNS) RFC 1995 RFC 1996 RFC 2219 RFC 2230 RFC 2845 RFC 2874 RFC 2929 RFC 2930 RFC 2964

Incremental Zone Transfer in DNS A Mechanism for Prompt Notification of Zone Changes (DNS) Use of DNS Aliases for Network Services Key Exchange Delegation Record for the DNS Secret Key Transaction Authentication for DNS (TSIG) DNS Extensions to Support IPv6 Address Aggregation and Renumbering Domain Name System (DNS) IANA Considerations Secret Key Establishment for DNS (TKEY RR) DNS Extensions to Network Address Translators (DNS_ALG)

Domain Names, Routing, Mail Routing, and Miscellaneous RFC 896 RFC 974 RFC 1032 RFC 1033 RFC 1034 RFC 1035 RFC 1072 RFC 1112 RFC 1122 RFC 1123 RFC 1144 RFC 1155 RFC 1212 RFC 1213 RFC 1451 RFC 1850 RFC 1321 RFC 1323 RFC 1386 RFC 1441 RFC 1452 RFC 1519 RFC 1583 RFC 1591 RFC 1630 RFC 1700 RFC 1737 RFC 1738 RFC 1808 RFC 1876 RFC 1900 RFC 1940 RFC 1956 RFC 1812 RFC 1911 RFC 1917 RFC 1918 RFC 1919 RFC 1985 RFC 2065 RFC 2136 RFC 2240 RFC 2538 RFC 2540 RFC 2673 RFC 2874 RFC 2929 RFC 3007

Congestion Control in IP/TCP Internetworks Mail Routing and the Domain System Domain Administrator’s Guide Domain Administrator’s Operations Guide Domain Names - Concepts and Facilities Domain Names - Implementation and Specification TCP Extensions for Long-Delay Paths Host Extensions for IP Multicasting Requirements for Internet Hosts - Communication Layers Requirements for Internet Hosts - Application and Support Compressing TCP/IP Headers for Low-Speed Serial Links Structure and Identification of Management Information for TCP/IP-Based Internets Concise MIB Definitions Management Information Base for Network Management of TCP/IP-Based Internets: MIB-II Manager to Manager Management Information Base OSPF Version 2 Management Information Base The MD5 Message-Digest Algorithm TCP Extensions for High Performance The U.S. Domain Introduction to Version 2 of the Internet-Standard Network Management Framework Coexistence between Version 1 and Version 2 of the Internet-Standard Network Management Framework Classless Inter-Domain Routing (CIDR): An Address Assignment and Aggregation Strategy OSPF Version 2 Domain Name System Structure and Delegation Universal Resource Identifiers in WWW: A Unifying Syntax for the Expression of Names and Addresses of Objects on the Network as used in the World-Wide Web Assigned Numbers Functional Requirements for Uniform Resource Names Uniform Resource Locators (URL) Relative Uniform Resource Locators A Means for Expressing Location Information in the Domain Name System Renumbering Needs Work Source Demand Routing: Packet Format and Forwarding Specification (Version 1) Registration in the MIL Domain Requirements for IP Version 4 Routers Voice Profile for Internet Mail An Appeal to the Internet Community to Return Unused IP Networks (Prefixes) to the IANA Address Allocation for Private Internets Classical versus Transparent IP Proxies SMTP Service Extension for Remote Message Queue Starting Domain Name System Security Extensions Dynamic Updates in the DOmain Name System (DNS UPDATE) A Legal Basis for Domain Name Allocation Storing Certificates in the Domain Name System (DNS) Detached Domain Name System (DNS) Information Binary Labels in the Domain Name System DNS Extensons to Support IPv6 Address Aggregation and Renumbering Domain Name System (DNS) IANA Considerations Secure Domain Name System (DNS) Dynamic Update

Sampling of Various Protocols RFC 793 RFC 768 RFC 791 RFC 792 RFC 793 RFC 821 RFC 826 RFC 896 RFC 903 RFC 916 RFC 951 RFC 959 RFC 977 RFC 1058 RFC 1301 RFC 1350 RFC 1661 RFC 1813 RFC 1831 RFC 1934 RFC 1987 RFC 1986 RFC 2165 RFC 2167 RFC 2246 RFC 2251 RFC 2326 RFC 2371 RFC 2408 RFC 2463 RFC 2543 RFC 2565 RFC 2566 RFC 2616 RFC 2637 RFC 2642 RFC 2705 RFC 2812 RFC 2813 RFC 2821 RFC 2878 RFC 2960 RFC 3010 RFC 3015 RFC 3018

Transmission Control Protocol (TCP) User Datagram Protocol (UDP) Internet Protocol (IP) Internet Control Message Protocol (ICMP) Transmission Control Protocol (TCP) Simple Mail Transfer Protocol (SMTP) Ethernet Address Resolution Protocol ISO Transport Protocol Reverse Address Resolution Protocol Reliable Asynchronous Transfer Protocol (RATP) Bootstrap Protocol (BOOTP) File Transfer Protocol (FTP) Network News Transfer Protocol (NNTP) Routing Information Protocol Multicast Transport Protocol The TFTP Protocol (Revision 2) The Point-to-Point Protocol (PPP) NFS Version 3 Protocol Specification RPC: Remote Procedure Call Protocol Specification Version 2 Ascend’s Multilink Protocol Plus (MP+) Ipsilon’s General Switch Management Protocol Specification Version 1.1 Experiments with a Simple File Transfer Protocol for Radio Links using Enhanced Trivial File Transfer Protocol (ETFTP) Service Location Protocol Referral Whois (RWhois Protocol V1.5) The TLS Protocol Version 1.0 Lightweight Directory Access Protocol (V3) Real Time Streaming Protocol (RTSP) Transaction Internet Protocol Version 3.0 Internet Security Assoication and Key Management Protocol (ISAKMP) Internet Control Message Protocol (ICMPv6) for IPv6 SIP: Session Initiation Protocol Internet Printing Protocol/1.0: Encoding and Transport Internet Printing Protocol/1.0: Model and Semantics HyperText Transfer Protocol - HTTP 1.1 Point-to-Point Tunneling Protocol Cabletron’s VLS Protocol Specification Media Gateway Control Protocol (MGCP) Version 1.0 Internet Relay Chat: Client Protocol Internet Relay Chat: Server Protocol Simple Mail Transfer Protocol PPP Bridging Control Protocol (BCP) Stream Control Transmission Protocol NFS Version 4 Protocol Megaco Protocol Version 1.0 Unified Memory Space Protocol Specification

Compression Protocols RFC 1950 RFC 1951 RFC 1952 RFC 1962 RFC 1967 RFC 1974 RFC 1977 RFC 1978 RFC 1993 RFC 2118 RFC 3173 RFC 2395 RFC 3173

ZLIB Compressed Data Format Specification Version 3.3 DEFLATE Compressed Data Format Specification Version 1.3 GZIP File Format Specification Version 4.3 The PPP Compression Control Protocol (CCP) PPP LZS-DCP Compression Protocol (LZS-DCP) PPP Stac LZS Compression Protocol PPP BSD Compression Protocol PPP Predictor Compression Protocol PPP Gandalf FZA Compression Protocol Microsoft Point-to-Point Compression (MPPC) Protocol IP Payload Compression Protocol (IPComp) [Obsoletes 2393] IP Payload Compression Using LZS IP Payload Compression Protocol (IPComp)

Telnet RFC 854 RFC 855 RFC 856 RFC 857 RFC 858 RFC 859 RFC 860 RFC 861 RFC 1053 RFC 1184 RFC 2217 RFC 2840 RFC 2877 RFC 2941

Telnet Protocol Specification Telnet Option Specifications Telnet Binary Transmission Telnet Echo Option Telnet Suppress Go Ahead option Telnet Status Option Telnet Timing Mark Option Telnet Extended Options: List Option Telnet X.3 PAD Option Telnet Linemode Option Telnet Com Port Control Option Telnet KERMIT Option 5250 Telnet Enhancements Telnet Authentication Option

SNMP RFC 1157 RFC 1351 RFC 1445 RFC 1446 RFC 1447 RFC 1901 RFC 1902 RFC 1903 RFC 1904 RFC 1905 RFC 1906 RFC 1907 RFC 2263 RFC 2271 RFC 2573

A Simple Network Management Protocol (SNMP) SNMP Administrative Model Administrative Model for Version 2 of the Simple Network Management Protocol (SNMPv2) Security Protocols for Version 2 of the Simple Network Management Protocol (SNMPv2) Party MIB for Version 2 of the Simple Network Management Protocol (SNMPv2) Introduction to Community-Based SNMPv2 Structure of Management Information for Version 2 of the SNMPv2 Working Group Textual Conventions for Version 2 of the Simple Network Management Protocol Conformance Statements for Version 2 of the Simple Network Management Protocol Protocol Operations for Version 2 of the Simple Network Management Protocol Transport Mappings for Version 2 of the Simple Network Management Protocol Management Information Base for Version 2 of the Simple Network Management Protocol SNMPv3 Applications An Architecture for Describing SNMP Management Frameworks SNMP Applications

PPP RFC 1172 RFC 1332 RFC 1334 RFC 1661 RFC 1841 RFC 1877 RFC 1915 RFC 1962 RFC 1963 RFC 1967 RFC 1968 RFC 1969 RFC 1973 RFC 1975 RFC 1976 RFC 1979 RFC 1989 RFC 1990 RFC 1993 RFC 1994 RFC 2363 RFC 2364 RFC 2716 RFC 2823 RFC 2878

Point-to-Point Protocol (PPP) initial configuration options The PPP Internet Protocol Control Protocol (IPCP) PPP Authentication Protocols The Point-to-Point Protocol (PPP) PPP Network Control Protocol for LAN Extension PPP Internet Protocol Control Protocol Extensions for Name Server Addresses Variance for The PPP Connection Control Protocol and The PPP Encryption Control Protocol The PPP Compression Control Protocol (CCP) PPP Serial Data Transport Protocol (SDTP) PPP LZS-DCP Compression Protocol (LZS-DCP) The PPP Encryption Control Protocol (ECP) The PPP DES Encryption Protocol (DESE) PPP in Frame Relay PPP Magnalink Variable Resource Compression PPP for Data Compression in Data Circuit-Terminating Equipment (DCE) PPP Deflate Protocol PPP Link Quality Monitoring The PPP Multilink Protocol [Obsoletes RFC 1717] PPP Gandalf FZA Compression Protocol PPP Challenge Handshake Authentication Protocol (CHAP) PPP over FUNI PPP over AAL5 PPP EAP TLS Authentication Protocol PPP over Simple Data Link (SDL) Using SONET/SDH with ATM-Like Framing PPP Bridging Control Protocol (BCP)

BGP, BGP-4 RFC 1163 Border Gateway Protocol RFC 1657 Definitions of Managed Objects for the Fourth Version of the Border Gateway Protocol (BGP-4) Using SMIv2 RFC 1771 A Border Gateway Protocol 4 (BGP-4) RFC 1772 Application of the Border Gateway Protocol in the Internet RFC 1773 Experience with the BGP-4 Protocol RFC 1774 BGP-4 Protocol Analysis RFC 1965 Autonomous System Confederations for BGP RFC 1966 BGP Route Reflection - An Alternative to Full Mesh IBGP RFC 1997 BGP Communities Attribute RFC 1998 An Application of the BGP Community Attribute in Multi-home Routing RFC 2283 Multiprotocol Extensions for BGP-4 RFC 2439 BGTP Route Flap Damping RFC 2545 Use of BGP-4 Multiprotocol Extensions for IPv6 Inter-Domain Routing RFC 2796 BGP Route Reflection - An Alternative to Full Mesh IBGP [Updates 1966] RFC 2842 Capabilities Advertisement with BGP-4 RFC 2918 Route Refresh Capability for BGP-4 RFC 3065 Autonomous System Confederations for BGP

POP RFC 1725 RFC 1939 RFC 1957 RFC 1833 RFC 2384 RFC 2449

Post Office Protocol Version 3 Post Office Protocol Version 3 Some Observations on Implementations of the Post Office Protocol (POP3) Binding Protocols for ONC RPC Version 2 POP URL Scheme POP3 Extension Mechanism

Whois RFC 1835 RFC 1913 RFC 1914 RFC 2167

Architecture of the Whois++ Service Architecture of the Whois++ Index Service How to Interact with a Whois++ Mesh Referral Whois (RWhois) Protocol V1.5

Format and Transmission Standards RFC 822 RFC 850 RFC 894 RFC 1042 RFC 1832 RFC 1922 RFC 1947

Standard for the Format of ARPA Internet Text Messages Standard for Interchange of USENET Messages Standard for the Transmission of IP Datagrams over Ethernet Networks Standard for the Transmission of IP Datagrams over IEEE 802 Networks XDR: External Data Representation Standard Chinese Character Encoding for Internet Messages Greek Character Encoding for Electronic Mail Messages

MIME RFC 1521 MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies RFC 1522 MIME (Multipurpose Internet Mail Extensions) Part Two: Message Header Extensions for Non-ASCII Text RFC 1927 Suggested Additional MIME Types for Associating Documents IPv6 (IPNG) RFC 1902 Structure of Management Information for Version 2 of the Simple Network Management Protocol RFC 1903 Textual Conventions for Version 2 of the Simple Network Management Protocol RFC 1904 Conformance Statements for Version 2 of the Simple Network Management Protocol RFC 1905 Protocol Operations for Version 2 of the Simple Network Management Protocol RFC 1906 Transport Mappings for Version 2 of the Simple Network Management Protocol RFC 1907 Management Information Base for Version 2 of the Simple Network Management Protocol RFC 1924 A Compact Representation of IPv6 Addresses RFC 1933 Transition Mechanisms for IPv6 Hosts and Routers RFC 1955 New Scheme for Internet Routing and Addressing (ENCAPS) for IPNG RFC 1970 Neighbor Discovery for IP Version 6 (IPv6) RFC 1971 IPv6 Stateless Address Autoconfiguration RFC 1972 A Method for the Transmission of IPv6 Packets over Ethernet Networks RFC 1981 Path MTU Discovery for IP version 6SNMPv2

IP General RFC 1919 RFC 1932 RFC 1954 RFC 2002 RFC 2764 RFC 3168

Classical versus Transparent IP Proxies IP over ATM: A Framework Document Transmission of Flow Labeled IPv4 on ATM Data Links Ipsilon Version 1.0 IP Mobility Support A Framework for IP-Based Virtual Private Networks The Addition of Explicit Congestion Notification (ECN) to IP

HTTP/HTML RFC 1866 RFC 1942 RFC 1945 RFC 1980 RFC 2145 RFC 2227 RFC 2295 RFC 2557 RFC 2616 RFC 2617 RFC 2660 RFC 2770 RFC 2818 RFC 2965

HyperText Markup Language - 2.0 HTML Tables Hypertext Transfer Protocol—HTTP/1.0 A Proposed Extension to HTML: Client-Side Image Maps Use and Interpretation of HTTP Version Numbers Simple Hit-Metering and Usage-Limiting for HTTP Transparent Content Negotiation in HTTP MIME Encapsulation of Aggregate Documents, such as HTML (MHTML) Hypertext Transfer Protocol - HTTP/1.1 HTTP Authentication: Basic and Digest Access Authentication The Secure HyperText Transfer Protocol An HTTP Extension Framework HTTP over TLS HTTP State Management Mechanism

ATM RFC 1483 RFC 1680 RFC 1755 RFC 1932 RFC 1946 RFC 2022 RFC 2098 RFC 2225 RFC 2226 RFC 2331 RFC 2364 RFC 2379 RFC 2380 RFC 2492 RFC 2512 RFC 2514 RFC 2515 RFC 2684 RFC 2761 RFC 2844

Multiprotocol Encapsulation over ATM Adaptation Layer 5 IPng Support for ATM Services ATM Signaling Support for IP over ATM IP over ATM: A Framework Document Native ATM Support for ST2+ Support for Multicast over UNI 3.0/3.1-based ATM Networks Toshiba’s Router Architecture Extensions for ATM: Overview Classical IP and ARP over ATM IP Broadcast over ATM Networks ATM Signaling Support for IP over ATM - UNI Signaling 4.0 Update PPP over AAL5 RSVP over ATM Implementation Guidelines RSVP over ATM Implementation Requirements IPv6 over ATM Networks Accounting Information for ATM Networks Definitions of Textual Conventions and OBJECT-IDENTITIES for ATM Management Definitions of Managed Objects for ATM Management Multiprotocol Encapsulation over ATM Adaptation Layer 5 Terminology for ATM Benchmarking OSPF over ATM and Proxy-PAR

Security, Encryption, Authentication RFC 1421 Privacy Enhancement for Internet Electronic Mail: Part I: Message Encryption and Authentication Procedures RFC 1422 Privacy Enhancement for Internet Electronic Mail: Part II: Certificate-Based Key Management RFC 1423 Privacy Enhancement for Internet Electronic Mail: Part III: Algorithms, Modes, and Identifiers RFC 1424 Privacy Enhancement for Internet Electronic Mail: Part IV: Key Certification and Related Services RFC 1455 Physical Link Security Type of Service RFC 1507 DASS - Distributed Authentication Security Service RFC 1510 The Kerberos Network Authentication Service (V5) RFC 1511 Common Authentication Technology Overview RFC 1675 Security Concerns for IPng RFC 1750 Randomness Recommendations for Security RFC 1826 IP Authentication Header RFC 1847 Security Multiparts for MIME: Multipart/Signed and Multipart/Encrypted RFC 1848 MIME Object Security Services RFC 1858 Security Considerations for IP Fragment Filtering RFC 1929 Username/Password Authentication for SOCKS V5 RFC 1938 A One-Time Password System RFC 1948 Defending Against Sequence Number Attacks RFC 1961 GSS-API Authentication Method for SOCKS Version 5 RFC 1964 The Kerberos Version 5 GSS-API Mechanism RFC 1968 The PPP Encryption Control Protocol (ECP) RFC 1969 The PPP DES Encryption Protocol (DESE) RFC 1984 IAB and IESG Statement on Cryptographic Technology and the Internet RFC 1991 PGP Message Exchange Formats RFC 2015 MIME Security with Pretty Good Privacy (PGP) RFC 2058 Remote Authentication Dial-In User Service (RADIUS) RFC 2082 RIP-2 MD5 Authentication RFC 2084 Considerations for Web Transaction Security RFC 2246 The TLS Protocol Version 1.0 RFC 2323 IETF Identification and Security Guidelines RFC 2406 IP Encapsulating Security Payload (ESP) RFC 2411 IP Security Document Roadmap RFC 2437 PKCS #1: RSA Cryptography Specifications Version 2.0 RFC 2480 Gateways and MIME Security Multiparts RFC 2539 Storage of Diffie-Hellman Keys in the Domain Name System (DNS) RFC 2541 DNS Security Operational Considerations RFC 2554 SMTP Service Extension for Authentication RFC 2577 FTP Security Considerations RFC 2617 HTTP Authentication: Basic and Digest Access Authentication RFC 2627 Key Management for Multicast: Issues and Architectures RFC 2659 Security Extensions for HTML RFC 2660 The Secure HyperText Transfer Protocol RFC 2695 Authentication Mechanisms for ONC RPC RFC 2709 Security Model with Tunnel-Mode IPsec for NAT Domains RFC 2712 Addition of Kerberos Cipher Suites to Transport Layer Security (TLS) RFC 2755 Security Negotiation for WebNFS RFC 2773 Encryption using KEA and SKIPJACK RFC 2876 Use of the KEA and SKIPJACK Algorithms in CMS

RFC 2898 RFC 2951 RFC 3008 RFC 3039 RFC 3156

PKCS #5: Password-Based Cryptography Specification Version 2.0 TELNET Authentication Using KEA and SKIPJACK Domain Name System Security (DNSSEC) Signing Authority Internet X.509 Public Key Infrastructure Qualified Certificates Profile MIME Security with OpenPGP

Frame Relay RFC 1586 RFC 1973 RFC 2115 RFC 2427 RFC 2590 RFC 2954 RFC 3034

Guidelines for Running OSPF over Frame Relay Networks PPP in Frame Relay Management Information Base for Frame Relay DTEs Using SMIv2 Multiprotocol Interconnect over Frame Relay Transmission of IPv6 Packets over Frame Relay Networks Specification Definitions of Managed Objects for Frame Relay Service Use of Label Switching on Frame Relay Networks Specification

Datagrams and Subnets RFC 919 RFC 922 RFC 948 RFC 950 RFC 1103 RFC 1134

Broadcasting Internet Datagrams Broadcasting Internet Datagrams in the Presence of Subnets Two Methods for the Transmission of IP Datagrams over IEEE 802.3 Networks Internet Standard Subnetting Procedure Proposed Standard for the Transmission of IP Datagrams over FDDI Networks Point-to-Point Protocol: A Proposal for Multi-Protocol Transmission of Datagrams over Pointto-Point

LDAP RFC 1823 RFC 1959 RFC 1960 RFC 2251 RFC 2255 RFC 2829 RFC 2849 RFC 2927

The LDAP Application Program Interface An LDAP URL Format A String Representation of LDAP Search Filters Lightweight Directory Access Protocol (v3) The LDAP URL Format Authentication Methods for LDAP The LDAP Data Interchange Format (LDIF) - Technical Specification MIME Directory Profile for LDAP Schema

Bibliography Author’s Note: Much of the content of this reference is derived from my own educational and consulting activities and daily (and frequently nightly) use of telecommunications technologies since the late 1970s, but it should be noted that I also consulted many historic texts, inventors’ notebooks, and hundreds of pre1900s journals, searching out credible and original sources on the evolution of the telecommunications industry. I am indebted to radio pioneers who recorded not only their knowledge, but their excitement and wonder at the birth of a new era and I would like to thank historians who search tirelessly for the truth about the origins of the early discoveries for I found, in the course of my research, that the threads of invention are not so clear and clean as they are depicted by most writers. I strove in this reference, wherever possible, to give the originators of the new technologies credit where it was due. Morse was far from the first to invent telegraphic technology (see telegraph history) and Bell may have popularized the telephone, but there were many previously uncredited and brilliant forerunners, most notably Antonio Meucci and some Rhode Island scientists associated with Stone Bank whose story is still not fully known. Meucci is finally given the attention he deserves in this reference and the author is trying to find out more about the Rhode Island group who apparently developed technology for Bell that was never fully credited. Books of Historical and General Interest

Asimov, Isaac; Asimov’s Biographical Encyclopedia of Science and Technology, Doubleday & Company, Inc., 1964. Baylin, Frank; Gale, B.; Long, R.; Home Satellite TV Installation and Troubleshooting Manual, Baylin Publications, 1997. Berkeley, Edmund C., Giant Brains or Machines That Think, John Wiley & Sons, Inc., 1949. Coe, Lewis; The Telegraph: A History of Morse’s Invention and Its Predecessors in the United States, McFarland & Company, Inc., 1993. Crocker, Francis B.; Esty, William; Cyclopedia of Applied Electricity: Volume II, American School of Correspondence, 1908. Crocker, Francis B.; Esty, William; Cyclopedia of Applied Electricity: Volume IV, American School of Correspondence, 1908. Dibner, Bern; The Atlantic Cable, Blaisdell Publishing Company, 1964. Dyson, George B.; Darwin Among the Machines: Evolution of Global Intelligence, Addison-Wesley Publishing Company, Inc, 1997. Evans, Alvis J.; Antennas: Selection and Installation, Tandy Corporation, 1989. Everitt, W. L., Editor; Fundamentals of Radio, Prentice-Hall, Inc., 1943. Fike, John L.; Friend, George E.; Understanding Telephone Electronics, Tandy Corporation, 1983. Fisher, David E.; Fisher, Marshall Jon; Tube: The Invention of Television, Counterpoint, 1996. Foley; van Dam; Feiner; Hughes; Computer Graphics: Principles and Practice, AddisonWesley Publishing Company, 1996. Graham, Frank D.; Audels Radiomans Guide [sic], Theo. Audel & Co., 1935. Heyn, Ernest V.; Fire of Genius: Inventors of the Past Century, Anchor Press/Doubleday, 1976. Hodge, Winston William; Interactive Television: A Comprehensive Guide for Multimedia Technologists, McGraw-Hill, Inc., 1995. Horowitz, Paul; Hill, Winnfield; The Art of Electronics, Cambridge University Press, 1994.

Jordan, Nelson, Osterbrock, Pumphrey, Smeby, Everitt; Fundamentals of RADIO, PrenticeHall, Inc., 1943. Kloeffler, Royce G.; Sitz, Earl L.; Basic Theory in Electrical Engineering, The Macmillan Company, 1955. Laughter, Victor H.; Operator’s Wireless Telegraph and Telephone Hand-Book, Frederick J. Drake & Co., 1909. Long, Mark; The Down to Earth Guide to Satellite TV, Quantum Publishing, Inc., 1985. Mabon, Prescott C.; Mission Communications: The Story of Bell Laboratories, Bell Telephone Laboratories, Inc., 1975. Meadowcroft, William H., A-B-C of Electricity, Harper & Brothers Publishers, 1915. Miller, Kempster B; Patterson, George W., et al.; Cyclopedia of Telephony and Telegraphy, Volume II: Manual Switchboards, Automatic Systems, Power Plants, American Technical Society, 1912. Miller, Kempster B; Patterson, George W., et al.; Cyclopedia of Telephony and Telegraphy, Volume IV: Telegraphy, Transmission, Electricity, American Technical Society, 1914. Myers & Crosby, Supervisors; Principles of Electricity Applied to Telephone and Telegraph Work, American Telephone and Telegraph Company, 1953. Petersen, Julie K.; Understanding Surveillance Technologies: Spy Devices, Their Origins & Applications, CRC Press, 2000. Pierce, John R.; Signals, The Telephone and Beyond, W. H. Freeman and Company, 1981. Roller, Duane; Roller, Duane H. D.; “The Development of the Concept of Electric Charge,” Harvard Case Histories in Experimental Science, Harvard University Press, 1954. Terman, Frederick Emmons; Radio Engineering, Second Edition, McGraw-Hill Book Company, Inc., 1937. Thompson, J. Arthur, Editor; The Outline of Science, First Volume, G. P. Putnam’s Sons, The Knickerbocker Press, 1922. Weaver, Jefferson Hane; The World of Physics: A Small Library of the Literature of Physics from Antiquity to the Present, Simon & Shuster, 1987. Wellman, William R., Elementary Electricity, D. Van Nostrand Company, Inc., 1959.

Historical Computing and Technology Journals

Walker, J. B., Editor; The Cosmopolitan: A Monthly Illustrated Magazine, Vol. XVI. November, 1893-April, 1894, The Cosmopolitan Press, 1894. Numerous Amiga and Macintosh journals

From 1986 to mid-1990s

Byte Magazine, The Small Systems Journal

Numerous issues from 1980 to 1987

Century Magazine

Numerous issues up to about 1900

Computer

Numerous issues from 1970 to 1980

Microcomputing, Wayne Green Publisher

June 1982

Popular Electronics

Numerous issues from 1974 to 1976

Popular Mechanics

Numerous issues from 1909 to 1924

Scientific American

Numerous issues from 1896 to 1921

As for current references, you can look them up on the Net. :-)

Acronyms & Abbreviations A A/D AA AAA AAAC AAAI AAAS

analog/digital, analog to digital Automated Attendant authentication, authorization, and accounting all aluminum alloy cable American Association for Artificial Intelligence American Association for the Advancement of Science AABS Automated Attendant Billing System AAC 1. abbreviated address calling 2. Aeronautical Administrative Communications AACS attitude and articulation control subsystem AAL ATM adaptation layer. AAMOF “as a matter of fact” AAP Applications Access Point AAPI Audio Applications Programming Interface AAPT American Association of Physics Teachers AAR automatic alternate routing AARP AppleTalk Address Resolution Protocol AAS authorized application specialist ABC 1. arbitration bus controller 2. Atanasoff-Berry Computer 3. automatic bass compensation ABEC alternate billing entity codes ABF air-blown fiber ABIST autonomous built-in self test ABM asynchronous balanced mode ABME asynchronous balanced mode extended ABR 1. available bit rate, cell rate 2. autobaud rate abs absolute value ABS Alternate Billing Services ABT Advanced Broadcast Television. ABX Advanced Branch Exchange. AC 1. Authentication Center 2. alternating current AC/WPBX Advanced Cordless/Wireless Private Branch Exchange ACA 1. American Communications Association 2. Australian Communications Authority 3. Automatic Circuit Assurance ACAR aluminum conductor alloy-reinforced ACARD 1. Advisory Council for Applied Research and Development 2. Acquisition Card Program ACATS Advisory Committee on Advanced Television Service ACB 1. Annoyance Call Bureau 2. Architecture Control Board 3. ATM Cell Bus 4. automatic callback ACCS Automatic Calling Card Service. ACD Automatic Call Distribution ACET Advisory Committee for Electronics and Telecommunications ACF Advanced Communication Function ACIA asynchronous communications interface adapter ACK acknowledge. ACL 1. access control list 2. Applications Connectivity Link 3. Association for Computational Linguistics ACM 1. Association for Computing Machinery 2. Automatic Call Manager 3. Address Complete Message ACO 1. Additional Call Offering 2. alarm cutoff ACOnet Austrian Academic Computer Network ACOST Advisory Council on Science and Technology ACP activity concentration point ACR 1. abandon call and retry 2. allowed cell rate 3. attenuation to crosstalk ratio ACS 1. Advanced Communication System 2. automatic call sequencer ACSE Association Control Service Element ACTS 1. Advanced Communications Technologies and Services 2. Advanced Communications Technology Satellite 3. Association of Competitive Telecommunications Suppliers 4. Automatic Coin Telephone Service ACUTA The Association of College and University Telecommunications Administrators

AD ADACC ADAS ADB ADC,A/DC

administrative domain Automatic Directory Assistance Call Completion Automated Directory Assistance Service Apple Desktop bus 1. analog-to-digital converter 2. automated data collection, automatic data collection ADCA Automatic Data Collection Association ADCCP Advanced Data Communication Control Procedures ADCIS Association for the Development of Computerbased Instruction ADCU Association of Data Communications Users ADF 1. automatic direction finder 2. automatic document feeder ADIO analog/digital input/output ADK application-definable keys ADM 1. adaptive-delta modulation 2. add/drop multiplexer ADN Advanced Digital Network ADNT Advanced Digital Network Trunking ADONIS Article Delivery Over Network Information Systems ADP automated data processing ADPCM adaptive differential pulse code modulation ADQ Average Delay in Queue ADR 1. achievable data rate 2. aggregate data rate 3. analog to digital recording 4. ASTRA Digital Radio ADRMP autodialing recorded message player ADRT approximate discrete Radon transform ADS 1. advanced digital system 2. AudioGram Delivery Services 3. automated data systems ADSL asymmetric digital subscriber line ADSP AppleTalk Data Stream Protocol ADSTAR Automated Document Storage And Retrieval ADSU ATM Data Service Unit ADT abstract data type ADTV Advanced Definition Television ADU asynchronous data unit AE 1. acoustic emission 2. Application Entity .ae Internet domain name extension for the United Arab Emirates AEA 1. American Electronics Association 2. American Engineering Association AEC acoustic echo canceller AECS Plan Aeronautical Emergency Communications System Plan AECT Association for Educational Communications and Technology AEEM Aerospace Engineering and Engineering Mechanics AEGIS Advanced Electronic Guidance and Instrumentation System AEP AppleTalk Echo Protocol AES 1. Application Environment Standard, Application Environment Service 2. atomic emission spectroscopy 3. Audio Engineering Society AESS Aerospace and Electronics Systems Society AEW 1. aircraft early warning 2. airborne early warning AF audio frequency AFAIK “as far as I know” AFAST Advanced Flyaway Satellite Terminal AFC 1. Advanced Fibre Communications 2. automatic frequency control AFCEA Armed Forces Communications and Electronics Association AFE 1. analog front end 2. antiferroelectric AFI Authority and Format Identifier AFIPS American Federation of Information Processing Societies AFK “away from keyboard” AFM 1. Adobe Font Manager. 2. Adobe Font Metrics 3. antiferromagnetism

AFMR AFNOR AFOSR AFP AFS AFT AFTRA

antiferromagnetic resonance Association Français Normal Air Force Office of Scientific Research AppleTalk Filing Protocol Andrew File System Automatic Fine Tuning American Federation of Television and Radio Artists AFV audio-follow-video AGC 1. AudioGraphic Conferencing 2. automatic gain control AGP Accelerated Graphics Port AGT AudioGraphics Terminal AGU 1. address-generation unit 2. Automatic Ground Unit Ah ampere-hour AHT Average Handle Time AI 1. Airborne Interception radar 2. artificial intelligence AIA 1. Aerospace Industries Association 2. Application Interface Adapter AIDA Accessible Information on Development Activities AIEE American Institute of Electrical Engineers AIFF Audio Interchange File Format AIIM Association for Information and Image Management AIM 1. amplitude intensity modulation 2. Ascend Inverse Multiplexing protocol 3. Association for Interactive Media 4. ATM inverse multiplexer AIN Advanced Intelligent Network AIOD Automatic Identified Outward Dialing AIP ATM Interface Processor AIR 1. additive increase rate 2. Airborne Imaging Radar 3. All India Radio AIS 1. alarm indication signal 2. Automatic Intercept System 3. Association for Information Systems 4. Automated Information System AIST Agency of Industrial Science and Technology AISTEL Associazione Italiana Sviluppo delle Telcomunicazioni AIT 1. assembly, integration, and testing 2. Atomic International Time (more correctly known as TIA) International Atomic Time 3. Automatic Identification Technology AITS Australian Information Technology Society AIX Advanced Interactive Executive AJ anti-jam AJP American Journal of Physics AKA also known as Al aluminum AL Adaptation Layer ALA American Library Association ALAP AppleTalk Link Access Protocol ALBO automatic line buildout ALC 1. automatic level control 2. automatic light control ALDC adaptive lossless data compression ALE 1. Application Logic Element 2. Atlanta Linux Enthusiasts 3. Automatic Link Establishment ALI 1. ATM Line Interface 2. automatic location identification, automatic location information ALIT Automatic Line Insulation Testing ALLC Association for Literary and Linguistic Computing ALM 1. airline miles 2. AppWare loadable module 3. automated loan machine ALPS automatic loop protection switching ALT automated loop test ALU arithmetic and logic unit AM 1. access module 2. active messages 3. active monitor 4. amplitude modulation AM/VSB amplitude modulated vestigial sideband AMDM ATM multiplexer/demultiplexer Ameslan American Sign Language AMHS Automated Message-Handling System AMI 1. alternate mark inversion 2. analog microwave link AMIS Audio Messaging Interchange Specification AML 1. Actual Measured Loss 2. ARC Macro Language AMLCD active matrix liquid crystal display

AMN AMPAS AMPS AMR AMS

Abstract Machine Notation Academy of Motion Picture Arts and Science Analog/Advanced Mobile Phone Service anisotropic magneto-resistance 1. Account Management System 2. American Meteorological Society 3. Attendant Management System AMSAT Amateur Satellite program AMSC American Mobile Satellite Corporation AMSS Aeronautical Mobile Satellite Service AMTOR amateur teleprinting over radio AMTS Automated Maritime Telecommunications System AN access network anamux analog multiplexer ANC All Number Calling ANI Automatic Number Identification ANT Access Network Termination AO acousto-optic AOCS attitude and orbit control system AOL America OnLine AOM acousto-optic modulator AOR Atlantic Ocean Region AOS 1. Alternate Operator Services 2. Area of Service AOSSVR Auxiliary Operator Services System Voice Response AOTF acousto-optic tunable filter AP 1. action potential 2. aiming point 3. application program 4. Applications Processor 5. array processor 6. Associated Press APAD asynchronous packet assembler/disassembler APAN Asia-Pacific Advanced Network Consortium APaRT Automated Packet Recognition/Translation APC 1. adaptive-predictive coding 2. advanced process control 3. Association for Progressive Communications APCC The American Public Communications Council APD avalanche photodiode APDU Application Protocol Data Unit API application programming interface APIC advanced programmable interrupt controller APL A Programming Language app application APP Ascend Password Protocol APPA American Public Power Association APPC advanced program-to-program communications APPN Advanced Peer-to-Peer Networking APRN Alaska Public Radio Network APS 1. Advanced Photo System 2. Automatic Protection Switching APTS Association of Television Stations AQL acceptable quality level Ar argon AR Automatic Recall ARA AppleTalk Remote Access ARB all-routes broadcast ARC Ames Research Center ARD 1. advanced research and development 2. Automatic Ring Down ARE All Routes Explorer ARES Amateur Radio Emergency Service ARF Alternative Regulatory Framework ARI Automatic Room Identification ARIB Association of Radio Industries and Businesses ARIES Angle-Resolved Ion and Electron Spectroscopy ARINC Aeronautical Radio, Inc. ARISE Advanced Radio Interferometry between Space and Earth ARISTOTELESApplications and Research Involving Space Technologies/Techniques Observing the Earth’s Fields from Low Earth-Orbiting Satellites ARL Association for Research Libraries ARM American Radio Museum AROS Amateur Radio Observation Service ARP Address Resolution Protocol ARPA Advanced Research Projects Agency ARQ automatic retransmit request ARRL American Relay Radio League

ARRN AS AS&C ASA ASAI ASAPI ASCA ASCII ASDSP ASE ASH ASI ASIC ASK ASN ASN.1 ASP

ASPI ASQ ASR ASSP ASSTA ASTC ASTER ASTRAL ASU ASV AT AT, PC/AT ATB ATC ATCP ATCRBS ATD ATDRSS ATG ATIS ATM ATMP ATS ATT ATV AUI AUP AUU AUUG AUXBC AVC AVD AVHRR AVIOS AVRS AVSSCS AWA AWC AWG

Amateur Radio Repeater Network autonomous system Alarm Surveillance and Control Acoustical Society of America Adjunct Switch Application Interface Advanced Speech API Advanced Satellite for Cosmology & Astrophysics (as-kee) American Standard Code for Information Interchange application-specific digital signal processor Application Service Element Ardire-Stratigakis-Hayduk 1. Adaptive Speed Leveling 2. Advanced Study Institute 3. artificial sensing instrument 4. Astronomical Society of India application-specific integrated circuit amplitude-shift keying, modulation 1. Abstract Syntax Notation 2. Autonomous System Number Abstract Syntax Notation 1 1. Abstract Service Primitive 2. Adjunct Service Point 3. administrative service provider 4. analog signal processing. 5. AppleTalk Session Protocol 6. ATM switch processor 7. Attached Support Processor 8. Association of Shareware Professionals Advanced SCSI Programming Interface Automated Status Query 1. Access Service Request 2. Airport Surveillance Radar 3. Automatic Send/Receive 4. Automatic Speech Recognition 1. acoustics speech and signal processing 2. application-specific standard product Australian Speech Science and Technology Association Australian Science and Technology Council Advanced Spaceborne Thermal Emission Reflectance Radiometer Alliance for Strategic Token-Ring Advancement and Leadership application-specific unit Air-to-Surface-Vessel radar 1. Access Tandem 2. AudioTex Advanced Technology all trunks busy air traffic control AppleTalk Control Protocol air traffic control radar beacon system 1. asynchronous time division 2. Attention Dial 3. advanced technology demonstration Advanced Tracking and Data Relay Satellite System address translation gateway Alliance for Telecommunications Industry Solutions 1. asynchronous transfer mode 2. Automated Teller Machine Ascend Tunnel Management Protocol Applications Technology Satellite program Automatic Toll Ticketing 1. advanced TV 2. amateur television Attachment Unit Interface Acceptable Use Policy ATM User-to-User Australian Unix User Group auxiliary broadcasting automatic volume control alternate voice data advanced very high resolution radiometer American Voice Input/Output Society automated voice response system Audio/Visual Service Specific Convergence Sublayer Antique Wireless Association Association for Women in Computing American Wire Gauge

B B8ZS binary/bipolar eight-zero substitution B-CDMA Broadband Code Division Multiple Access B-DCS broadband digital cross-connect system B-ICI B-ISDN InterCarrier Interface B-ICI SAAL B-ICI Signaling ATM Adaptation Layer B-ISDN Broadband ISDN B-LT broadband line termination B-MAC Broadcast Master Antenna Control B-NT broadband network termination B-TE broadband terminal equipment BABT British Approvals Board for Telecommunications BACP Bandwidth Allocation Control Protocol BAFTA British Academy of Film and Television Arts BAN 1. base area network 2. Billing Account Number BB 1. baseband 2. broadband BBC 1. Broadband Bearer Capability 2. British Broadcasting Corporation BBG Basic Business Group BBN 1. Bolt, Beranek, and Newman, Inc. 2. BBN Planet BBS bulletin board system BBT broadband technology Bc Committed Burst Size BC 1. backward compatible 2. beam coupling 3. binary code 4. broadcast BCC 1. Bellcore Client Company 2. block check character BCD binary coded decimal BCNU “be seein’ you” BCOB Broadband Connection Oriented Bearer BCP best current practice BCRS Bell Canada Relay Service BCS 1. basic control system 2. Batch Change Supplement 3. Boston Computer Society 4. British Computer Society BDCS Broadband Digital Cross-Connect System BDF block data format BDT Telecommunications Development Bureau Be 1. Excess Burst Size 2. Be, Inc. BE 1. base embossed 2. Bose-Einstein BEC Bose-Einstein condensation BECN Backward Explicit Congestion Notification BEP Back End Processor BER 1. Basic Encoding Rules 2. bit error rate BETRS Basic Exchange Telecommunications Radio Service BFI Bad Frame Indicator BFO beat frequency oscillator BFOC bayonet fiber optic connector BFT binary file transfer BG, BGND background BGP Border Gateway Protocol BHLI Broadband High Layer Information BIB Backward Indicator Bit BIBO bounded input, bounded output B-ICI Broadband Inter-Carrier Interface B-ICI SAAL Broadband Inter-Carrier Interface Signaling ATM Adaptation Layer BICEP bit-interleaved parity BIDDS base information digital distribution system BIG broadband integrated gateway BIND Berkeley Internet Name Domain BIS border immediate system BISDN B-ISDN BISSI Broadband Inter-Switching System Interface BIST built-in self-test BITS Base Information Transport System BIU basic information unit BL bit line BLSR Bidirectional Line Switched Ring BLU basic link unit BM burst modem BMEWS Ballistic Missile Early Warning System BNC bayonet nut connection, bayonet navy connector BNCC base network control center BO branch office

board BOC BOF BOM BOP BP BPAD BPDU BPI BPM BPON BPS BPSK BR BRB BRCS BRI BS BSAM BSCC BSD BSE BSF BSI BSL BSMS BSMTP BSP BSR BSS BSVC BT BTA BTag BTBT BTE BTI BTL BTM BTN BTRL BTS BTU BTW BW BZT

printed circuit board Bell Operating Company 1. Birds of a Feather 2. Business Operations Framework 1. Beginning of Message 2. bill of materials Bit Oriented Protocol 1. bandpass 2. base pointer 3. bypass Bisynchronous Packet Assembler/Disassembler Bridge Protocol Data Unit bytes per inch Beam Position Monitor Broadband Passive Optical Network bits per second binary phase shift keying 1. beacon receiver 2. Radiocommunications Bureau “be right back” Business and Residence Customer Services Basic Rate Interface 1. back scatter 2. band signaling 3. base station 4. beam splitter Basic Sequential Access Method BellSouth Cellular Corporation Berkeley Software Distribution 1. back-scattered electrons 2. Basic Service Element 3. Basic Switching Element bit scan forward British Standards Institution British Sign Language Broadcast Short Message Service Batch Simple Message Transfer Protocol 1. Bell System Practice 2. Byte Stream Protocol 1. bit scan rate 2. bit scan reverse 1. Base Station System 2. broadcasting satellite service 3. Business Support System Broadcast Switched Virtual Connections 1. British Telecom 2. Burst Tolerance 1. Basic Trading Area 2. Broadband Telecommunications Architecture 3. broadband terminal adaptor Beginning Tag band-to-band tunneling 1. Boltzmann Transport Equation 2. broadband terminal equipment British Telecom International Bell Telephone Laboratories Broadband Transport Manager Billing Telephone Number, Billed Telephone Number British Telecom Research Laboratories 1. Base Transceiver Station 2. bit test and set 1. basic transmission unit 2. British Thermal Unit “by the way” bandwidth Bundesamt für Zulassungen in der Teleommunikation

C C/A Code C64 CA CAB CACM CAD CADS CAE CAFA CAI CAL CALC CALS CAM

civilian code, S-code Commodore 64 Call Appearance Canadian Association of Broadcasters Communications of the Association for Computing Machinery 1. computer-aided dispatch 2. computer-aided design/drafting Code Abuse Detection System 1. Common Applications Environment 2. computeraided engineering computer-aided financial analysis 1. computer assisted instruction 2. common air interface computer-aided learning, computer-assisted learning customer access line charge Continuous Acquisition and Life-Cycle Support 1. carrier module 2. Call Accounting Manager 3.

Call Applications Manager 4. computer-aided manufacturing 5. computer-assisted makeup, composition and makeup CAMA Centralized Automatic Message Accounting CAN Control Area Network CAP 1. carrierless amplitude and phase modulation 2. Cellular Array Processor 3. Competitive Access Provider CAR computer-assisted retrieval CARAB Canadian Amateur Radio Advisory Board CAS 1. Centralized Attendant Service 2. channel associated signaling 3. Communications Applications Specification CASE computer-aided software engineering, computer-assisted software engineering CAST computer-aided software testing, computer-assisted software testing CATNIP Common Architecture for Next Generation Internet Protocol CATS Consortium for Audiographics Teleconferencing Standards CATV 1. Cable Television 2. Community Antenna Television CAU controlled access unit CAV Constant Angular Velocity CB citizen’s band (radio) CBC Canadian Broadcasting Corporation CBDS Connectionless Broadband Data Service CBM Commodore Business Machines CBR constant bit rate CBS Columbia Broadcasting System CBSC Canadian Broadcast Standards Council CBT 1. Canadian Business Telecommunications Alliance 2. Computer-Based Training CBTA Canadian Business Telecommunications Alliance CBX Computerized Branch Exchange CC carbon copy CCB Common Carrier Bureau. CCC 1. clear channel capability 2. Communications Competition Coalition CCD charge coupled device CCIA Computer and Communications Industry Association CCIR Comité Consultatif International des Radiocommunications CCIRN Coordinating Committee for Intercontinental Research Networks CCIS Common Channel Interoffice Signaling CCITT Comité Consultatif Internationale de Télégraphique et Téléphonique CCP Compression Control Protocol CCR current cell rate CCS Common Channel Signaling CCS/SS7 Common Channel Signal/Signaling System 7 CCT 1. Calling Card Table 2. Consultative Committee Telecommunications CCTA Central Computer and Telecommunications Agency CCTV Closed Circuit TV CCU 1. camera control unit 2. communications control unit CD 1. carrier detect 2. compact disc 3. count down CD-V compact disc video CD-WO compact disc write once CDA Communications Decency Act CDCS Continuous Dynamic Channel Selection CDDI Copper Distributed Data Interface CDE Common Desktop Environment CDLC Cellular Data Link Control CDMA Code Division Multiple Access CDMP Cellular Digital Messaging Protocol CDO community dial office CDP 1. Cisco Discovery Protocol 2. Customized Dial Plan CDPD Cellular Digital Packet Data CDR Call Detail Record CDT credit allocation

CDTAC

Consumer/Disabilities Telecommunications Advisory Committee CDV 1. cell delay variation 2. Compressed Digital Video CDVT cell delay variation tolerance CE Connection endpoint CEO Chief Executive Officer CEPT Conférence Européenne des Administrations des Postes et Télécommunications CER cell error ratio CERB Centralized Emergency Reporting Bureau CERFnet California Education and Research Federation Network CERN Centre European des Recherche Nucleaire CERT Computer Emergency Response Team CEST Centre for the Exploitation of Science and Technology CEV controlled environmental vault CFB Call Forward Busy CFDA Call Forward Don’t Answer CFGDA Call Forward Group Don’t Answer CFP Channel Frame Processor CFR Confirmation to Receive CFUC Call Forwarding UnConditional CFV Call for Votes CFW Call Forward CGA 1. Carrier Group Alarm 2. Color Graphics Adapter CGI Common Gateway Interface CGISS Commercial Government and Industrial Solutions Sector CGM Computer Graphics Metafile CGSA Cellular Geographic Service Area CI 1. congestion indicator 2. Certified Integrator CIAJ Communications Industry Association of Japan CIC Carrier Identification Code CIDR Classless Inter-Domain Routing CIE The Commission Internationale de L’Eclairage (Internal Commission of Illumination) CIF 1. cells in flight 2. Cells in Frames 3. Common Intermediate Format 4. cost, insurance, freight CIID Card Issuer Identifier Code CIIG Canadian ISDN Interest Group CIP Carrier Identification Parameter CIR Committed Information Rate CISC Complex Instruction Set Computing CISCC Collocation Interconnection Service Cross Connection CITEL Inter-American Telecommunications Commission CITR Canadian Institute for Telecommunications Research CIV cell interarrival variation CIVDL Collaboration for Interactive Visual Distance Learning CIX Commercial Internet Exchange CJC Canadian Journal of Communication CLDC connected limited device configuration CLEC Competitive Local Exchange Carrier CLP 1. Cell Loss Priority 2. Connectionless Transport Protocol CLR Cell Loss Ratio CLTS Connectionless Transport Service CMC connection management controller CMDS Centralized Message Distribution System CMOS Complementary Metal Oxide Semiconductor CMR cell misinsertion rate CMRS Commercial Mobile Radio Service CMTS Cellular Mobile Telephone System CMY cyan, magenta, yellow CN Complementary network CNA 1. Centralized Network Administration 2. Cooperative Network Architecture CND 1. Calling Number Delivery 2. Calling Number Display CNET Centre National d’Études de Télécommunication CNIS Calling Number Identification Services CNR 1. Complex Node Representation 2. customer not ready

CNRI Co CO

Corporation for National Research Initiatives Symbol for cobalt 1. cash order 2. central office 3. commanding officer COAM Customer Owned And Maintained [Equipment] COB Close of Business COBOL Common Business-Oriented Language COBRAS Cosmic Background Radiation Anisotropy Satellite COCOT customer-owned coin-operated telephone COD connection-oriented data COM 1. Component Object Model 2. continuation of message COMETT Community Action Programme in Education and Training for Technology COPT Coin Operated Pay Telephone CoS class of service COS 1. compatible for open systems 2. Corporation for Open Systems International COSETI Columbus Optical SETI COSINE Cooperation for Open Systems Interconnection Networking in Europe COTAT Committee on Land Transportation and Telecommunications COTS 1. commercial off the shelf 2. Connection Transport Service CP/M Control Program/Monitor, Control Program for Microcomputers CPAS Cellular Priority Access Service CPB Corporation for Public Broadcasting CPCS Common Part Convergence Sublayer CPD Call Processing Data CPE Customer Premises Equipment, Customer Provided Equipment CPI common part indicator CPL commercial private line CPN Calling Party Number cps characters per second CPU central processing unit CQ come quick CQD come quick, distress CR 1. carriage return 2. call reference 3. connection request 4. customer record CRB Community Radio Broadcasters CREN Corporation for Research and Educational Networking CRF 1. cell relay function 2. connection-related function CRIS Customer Record Information System CRM cell rate margin CRMA Cyclic Reservation Multiple Access Protocol CRS cell relay service CRT Cathode Ray Tube CRTC Canadian Radio Television and Telecommunications Commission CS communications satellite CSA 1. Callpath Services Architecture 2. Canadian Standards Association CSC customer service center CSMA Carrier Sense Multiple Access CSNET Computer+Science Network CSPP Computer Systems Policy Project CSR 1. cell switch router 2. customer service record CST Computer Supported Telephony CSTA Computer Supported Telephony Application CSU Channel Service Unit CSU/DSU Channel Service Unit/Data Service Unit CSUA Canadian Satellite Users Association CT 1. Call Type 2. Cordless Telephone 3. Conformance Test CT3IP Channelized T3 Interface Processor CTCA Canadian Telecommunications Consultants Association CTD 1. cell transfer delay 2. Continuity Tone Detector CTI 1. Call Technologies, Inc. 2. Computer Telephony Integration 3. Critical Technologies Institute CTIA 1. Cellular Telecommunications Industry Association 2. Computer Technology Industry Association

CTL CTRL CTS CTSS CTTC CTX

Complex Text Layout Control (also written Ctrl and ctrl) 1. clear to send 2. Communication Transport System 3. Conformance Testing Services Compatible Time-Sharing System coax to the curb Centrex

D DA

1. desk accessory 2. destination address 3. Directory Agent 4. Directory Assistance DAA Data Access Arrangement DAB 1. digital audio broadcasting 2. dynamically allocatable bandwidth DACS Digital Access and Cross-connect System DAF Destination Address Field DAI Development Activity Information DAL Dedicated Access Line DAMA Demand Assigned Multiple Access DAP Directory Access Protocol DAQ Delivered Audio Quality DAR digital audio radio DARPA Defense Advanced Research Projects Agency DARS Digital Audio Radio Service DASD direct access storage device DAT digital audio tape DBMS Database Management System DBS direct broadcast satellite DBT Deutsche Bundespost Telecom DC 1. In telephone communications, Delayed Call 2. direct current 3. disconnect conform DCA 1. Defense Communications Agency 2. Document Content Architecture 3. Dynamic Channels Allocation DCC 1. data communications channel 2. Data Country Code DCD Data Carrier Detect DCE data communications equipment DCM dynamically controllable magnetic DCP Digital Communications Protocol DCS 1. digital communications system 2. digital crossconnect system 3. distributed computing system DCT discrete cosine transform DCTI desktop computer telephony integration DDB digital databank DDCMP Digital Data Communications Message Protocol DDD Direct Distance Dialing DDE dynamic data exchange DDN Defense Data Network DDP distributed data processing DDS 1. digital data service 2. digital data storage 3. distributed data system DE Discard Eligibility DEW line Distant Early Warning line DFA doped fiber amplifier DG Development Gateway DGPS Differential Global Positioning System DGPT Department General of Posts and Telecommunications, Viet Nam DGT Dirección General de Telecommunicaciones DHCP Dynamic Host Configuration Protocol DID Direct Inward Dialing DII defense information infrastructure DIM document image management DIMS Document Image Management System DIN 1. Deutsches Institute för Normung 2. dual inline DINA Distributed Intelligence Network Architecture DL 1. distant learning 2. distribution list DLC 1. Data Link Control 2. Digital Loop Carrier DLCI Data Link Connection Identifier DLL 1. data link layer 2. Dynamic Link Library DLR Design Layout Record DLS, DLSwData Link Switching DLSW DataLink Switching Workgroup DM delta modulation

DMA DMD DMI DML DMS DMSP DMT DMTF DN DNA DNC DNCF DNIC DNIS DNR DNS DoS DOS DP DPA DPBX DPCM DPE DPLB DPNSS DPO DPP DPX DQDB DRAM DRO DS DSA DSAT DSC DSCS DSE DSH DSI DSL DSLAM DSP DSR DSRC DSRR DSS DSTO DSU DT DTE DTL DTMF DTP DTR DTRS DTSR DTT DTU DTV DVB DVBG DVD DVST DX DXI

1. direct memory access 2. Document Management Alliance differential mode delay 1. Desktop Management Interface 2. Digital Multiplexed Interface Development Markup Language Digital Multiplex System Defense Meteorological Satellite Program discrete multitone Desktop Management Task Force Directory Number 1. Digital Network Architecture 2. distributed network administration 1. distributed networking computing 2. dynamic network controller Directory Number Call Forwarding Data Network Identification Code Dialed Number Identification Service Dynamic Network Reconfiguration Domain Name System Denial of Service disk operating system 1. data processing 2. demarcation point 3. Dial Pulse 1. Demand Protocol Architecture 2. digital port adapter digital private branch exchange differential pulse code modulation distributed processing environment Digital Private Line Billing Digital Private Network Signaling System Direct Public Offering Distributed Processing Peripheral DataPath loop extension Distributed Queue Dual Bus 1. digital recorder, announce mode 2. dynamic RAM Disabilities Rights Office 1. Dansk Standardiseringsrad 2. digital system 3. Distributed Single Layer Test Method 1. data service adapter 2. Digital Signature Algorithm 3. Directory System Agent Digital Supervisory Audio Tones Digital Selective Calling Defense Satellite Communications System Distributed Single Layer Embedded (Test Method) double-superheterodyne digital speed interpolation Digital Subscriber Line DSL access multiplexer 1. digital signal processor 2. Display System Protocol data set ready Dedicated Short Range Communications digital short range radio 1. Digital Signature Standard 2. Direct Station Select 3. direct satellite system Defence Science and Technology Organisation Digital Service Unit Deutsche Telekom Data Terminal Equipment, End Device 1. Designated Transit List 2. diode transistor logic dual tone multifrequency desktop publishing Data Terminal Ready Digital Trunked Radio System Dial Tone Speed Recording Digital Trunk Testing Digital Test Unit digital television, digital TV Digital Video Broadcasting Digital Video Broadcasting Group 1. Digital Versatile Disc 2. digital videodisc direct view storage tube data exchange data exchange interface

E EA EACEM

Equal Access European Association of Consumer Electronics Manufacturers EAGLE Extended Area Global Positioning System (GPS) Location Enhancement EARN European Academic Research Network EARP Ethernet Address Resolution Protocol EAS 1. Emergency Alert System 2. Extended Area Service EBS Emergency Broadcast System EBU European Broadcasting Union EC 1. exchange carrier 2. European Community, European Common Market, European Union (EU) ECC 1. elliptic curve cryptography 2. Emergency Communications Center ECHO European Commission Host Organization ECI emitter coupled logic ECMA European Computer Manufacturers Association ECP 1. Encryption Control Protocol 2. Enhanced Call Processing ECPA Electronic Communications Privacy Act ECSA Exchange Carriers Standards Association ECTF 1. Enterprise Computer Telephony Forum 2. European Community Telework Forum ECTUA European Council of Telecommunications Users Association ED Electronic Directory EDA electronic design automation EDAC error detection and correction EDACS Enhanced Digital Access Communications System EDDA European Digital Dealers Association EDF erbium-doped fiber EDFA erbium-doped fiber amplifier EDGAR Electronic Data Gathering Archiving and Retrieval EDI Electronic Data Interchange EDIFACT Electronic Data Interchange for Finance, Administration, Commerce, and Transport EDM electronic document management EDO RAM extended data-out random access memory EDP electronic data processing EDSAC Electronic Delay Storage Automatic Computer EDTV Enhanced-definition TV EEC European Economic Community EEI external environment interface EEMA European Electronic Messaging Association EEPROM electronically erasable programmable read only memory EF entrance facility EF&I engineer, furnish, and install EFCI explicit forward congestion indicator EFF Electronic Frontier Foundation EFI&T engineer, furnish, install, and test EFS error free seconds EFT Electronic Funds Transfer EFTA European Free Trade Association EFTPOS Electronic Funds Transfer Point of Sale EGA Enhanced Graphics Adapter EGNOS European Geostationary Navigation Overlay Service EGP Exterior Gateway Protocol EIA Electronic Industries Alliance EIG Electronic Information Group EIR Equipment Identity Register EIRPAC Eire packet network EIS Expanded Interconnection Service EISA Extended Industry Standard Architecture EIU Ethernet Interface Unit EKE electronic key exchange EKTS Electronic Key Telephone Service ELIU electrical line interface unit ELOT Hellenic Organization for Standardization ELSU Ethernet LAN Service Unit EMA Electronic Messaging Association EMP electromagnetic pulse EMR Exchange Message Record

EMS EMT EMU ENN ENOS ENS EO EOB EOF EOL EOM EOS EOT EOTC EPD EPF EPP EPROM EPS EPSCS

Expanded Memory Specification electrical metal tubing European Monetary Unit Emergency News Network Enterprise Network Operating System Emergency Number Services 1. end office 2. erasable optical end of block end of file end of line end of message Earth Observing System 1. end of transmission 2. end of tape European Organization for Testing and Certification Early Packet Discard Electronic Payments Forum Enhanced Parallel Port erasable programmable read-only memory Encapsulated PostScript Enhanced Private Switched Communications Service ERP effective radiated power ERS European Remote Sensing Satellite ERTS-1 Earth Resources Technology Satellite ESA 1. emergency stand-alone 2. European Space Agency ESC, Esc escape ESCA European Speech Communication Association ESD electrostatic discharge ESF Extended SuperFrame ESI 1. Enhanced Serial Interface 2. End System Identifier ESMR Enhanced Specialized Mobile Radio ESMTP Extended Simple Mail Transport Protocol ESN 1. electronic serial number 2. electronic switched network 3. emergency services number ESnet Energy Sciences Network ESP 1. Encapsulating Security Payload 2. Enhanced Serial Port ESPA European Selective Paging Association ESPAN Enhanced Switch Port Analyzer ESS electronic switching system ESTO European Science and Technology Observatory ETACS Extended TACS ETF European Teleconferencing Federation ETFTP Enhanced Trivial File Transfer Protocol ETNO European Public Telecommunications Network Operations Association ETS European Telecommunication Standard ETSI European Telecommunications Standards Institute EUROTELDEV European (Regional) Telecommunication Development EUV extreme ultraviolet eV electron volt EW Electronic Warfare EWOS European Workshop for Open Systems EWP electronic white pages ExCa Exchangeable Card Architecture EXTN extension EYP electronic yellow pages

F FAM fanfold FANP FANS FAQ FB FBT FBus FC FCA FCC FCLC FCS

fast access memory z-fold Flow Attribute Notification Protocol Future Air Navigation System Frequently Asked Question Framing bit Fused Biconic Tape Frame Transport Bus 1. feedback control 2. frame control Fibre Channel Association Federal Communications Commission Fibre Channel Loop Community 1. Federation of Communications Services 2. Frame Check Sequence 3. Fraud Control System

FCSI FDD FDDI FDM FDMA FEC FECN FEP FER FEXT FF FGDC FID FIF FIFO FM FMAS FMV FNC FNR FNS FOA

Fibre Channel Systems Initiative floppy disk drive Fiber Distributed Data Interface frequency division multiplexing frequency division multiple access forward error correction Forward Explicit Congestion Notification Front End Processor Frame Error Rate far end crosstalk form feed Federal Geographic Data Committee Field Identifier Fractal Image Format first in, first out 1. fault management 2. frequency modulation Facility Maintenance and Administration System Fair Market Value Federal Networking Council fixed network reconfiguration Fiber Network Systems 1. fiber optic amplifier 2. Fiber Optic Association, Inc. 3. First Office Application FOC Firm Order Confirmation FOD fax-on-demand foil overhead transparency FOT Fiber Optic Terminal FOTS fiber optic transmission system FPLMTS Future Public Land Mobile Telecommunication System fps frames per second FPU floating point unit FQDN Fully Qualified Domain Name FR Frame Relay FRA fixed radio access FRAD Frame Relay access device FRM focus-rotation mount FRMR Federal Information Resources Management Regulation FRND frame relay network device FRSE frame relay switching equipment FRTE frame relay terminal equipment FSAN Full Services Access Network FSK frequency shift keying FSO Foreign Service Office FSP File Service Protocol FSS fixed satellite service FSTC Financial Services Technology Consortium FTA Federal Telecommunications Act FTIP Fiber Transport Inside Plant FTNS Fixed Telecommunications Network Service FTP File Transfer Protocol FTS 1. file transfer support 2. Federal Telecommunications System FTTC fiber to the curb FTTH fiber to the home FTTL fiber in the loop fV femtovolt FVR flexible vocabulary recognition FWA Fixed Wireless Access FWIW “for what it’s worth” FYI “for your information” FX Foreign Exchange

G G/A G/G GA GAB GIGO GII GIIC GILC GILS GIP GIS

ground to air communication ground to ground communication go ahead Group Access Bridging garbage in, garbage out global information infrastructure Global Information Infrastructure Commission Global Internet Liberty Campaign Government Information Locator Service Global Internet Project geographic information system

GITS GKP GL

Government Information Technology Services Global Knowledge Partners graphics library

H HALE HAN HBA HBS HCI

High Altitude Long Endurance home area network host bus adapter Home Base Station 1. Host Command Interface 2. human computer interface 3. Human Computer Interface standards HD half duplex HDB3 High Density Bipolar Three HDD Hard Disk Drive HDLC High Level Data Link Control HDSL high bit-rate digital subscriber line HDT Host Digital Terminal HDTV High Definition Television HEC Header Error Control HEP high energy physics HF, hf 1. hands free 2. high fidelity 3. high frequency HFC Hybrid Fiber Coax HFU hands free unit Hi-OVIS Highly Interactive Optical Visual Information System HNF High-performance Network Forum HNS Hughes Network Systems HOBIS Hotel Billing Information System HP Hewlett-Packard HPA high power amplifier HPIIS high performance international internet services HRPT high resolution picture transmission HSCI High-Speed Communications Interface HSCS high speed circuit switched HSD home satellite dish HSDA high speed data access HSDU High Speed Data Unit HSRP Hot Standby Router Protocol HST High Speed Technology HSV hue, saturation, value HTL high threshold logic HTTP Hypertext Transfer Protocol HTTPS Hypertext Transfer Protocol Secure HUT Hopkins Ultraviolet Telescope HW hardware Hz hertz

I IBM-ERS IBM Internet Emergency Response Service IBN Institut Belge de Normalisation IBS 1. intelligent battery system 2. Intelsat Business Service IC 1. integrated circuit 2. intercom 3. interexchange carrier 4. intermediate cross-connect ICAL Internet Community at Large ICAPI International Call Control API ICB Individual Case Basis ICCB Internet Configuration Control Board ICCF Industry Carriers Compatibility Forum ICEA Insulated Cable Engineers Association ICI Interexchange Carrier Interface ICM Integrated Call Management ICMP Internet Control Message Protocol ICO Global Communications ICONTEC Instituto Colombiano de Normas Técnicas ICTA International Computer-Telephony Association ID 1. identification, identifier 2. input device 3. intermediate device IDA 1. integrated data access, integrated digital access 2. intelligent drive array IDAI Integrated Development Activity Information IDCMA Independent Data Communications Manufacturers Association IDLC Integrated Digital Loop Carrier IDE integrated development environment

IDEA IDEN IDF IDL IDLC IDML IDN ID IDS IDSCP IDTV IDU IEC

International Data Encryption Algorithm Integrated Digital Electronic Network intermediate distribution frame Interface Design Language Integrated Digital Loop Carrier International Development Markup Language Integrated Digital Network integrated dispatch intrusion detection system Initial Defense Communications Satellite Program Improved Definition Television Interface Data Unit 1. Inter Exchange Carrier 2. International Electrotechnical Commission 3. International Engineering Consortium IEN Internet Experimental Note IETF Internet Engineering Task Force IF intermediate frequency IFCM independent flow control message IFD image file directory IFIP International Federation for Information Processing IFRB International Frequency Registration Board IGC intelligent graphics controller IGMP Internet Group Multicast Protocol IGP Interior Gateway Protocol IGRP Interior Gateway Routing Protocol IGT Ispettorato Generale delle Telcomunicazioni IGY International Geophysical Year IIR Interactive Information Response IIOP Internet Inter-ORB Protocol IISP 1. Information Infrastructure Standards Panel 2. Interim Interswitch Signaling Protocol IITC Information Infrastructure Task Force IJCAI International Joint Conferences on Artificial Intelligence ILEC Incumbent Local Exchange Carrier ILMI Interim Link Management Interface IM intermodulation distortion IMA Interactive Multimedia Association IMAC Isochronous Media Access Control IMAP Internet Messaging Access Protocol IMASS Intelligent Multiple Access Spectrum Sharing IMAX “I” - eye + maximum IMHO “in my humble opinion” IMNSHO “in my not so humble opinion” IMO “in my opinion” IMPATT impact avalanche and transit time IMPDU Initial MAC Protocol Data Unit IMSI International Mobile Subscriber Identity IMTC The International Multimedia Teleconferencing Consortium IMTS Improved Mobile Telephone Service IMUX Inverse Multiplexer IMW Intelligent Music Workstation INA Information Networking Architecture INC international carrier INCC Internal Network Control Center INDIX International Network for Development Information Exchange INGECEP Integrated Next Generation Electronic Commence Environment Project IOF Inter Office Facility IOL InterOperability Lab ION Internetworking Over NBMA IP Internet Protocol IPATM Internetworking over NBMA IPCE interprocess communication environment IPL Initial Program Load IPng IP Next Generation IPO Initial Public Offering IPS Internet Protocol Suite IPSec IP Security protocol IR infrared IRAC Interdepartmental Radio Advisory Council IRC 1. integrated receiver decoder 2. Internet Relay Chat IrDA Infrared Data Association

IRE IREQ IRR IRSG IRTF ISA ISD ISDN ISI ISL ISM ISNI ISO ISOC ISP ISPBX ITFS ITM ITR ITS IVDS IVHS IVI IVR IVS IW IWS IXC

Institute of Radio Engineers interrupt request Internet Routing Registry Internet Research Steering Group Internet Research Task Force 1. industry standard architecture 2. Interactive Services Association Incremental Service Delivery Integrated Services Digital Network Information Sciences Institute Inter-Switch Link 1. Industrial Scientific Medical 2. interstellar medium Intermediate Signaling Network Identification International Organization for Standardization Internet Society 1. Internet Services Provider 2. Information Services Platform 3. ISDN Signal Processor Integrated Services Private Branch Exchange Instructional Television Fixed Service Information Technology Management International Telecommunication Regulations 1. Institute for Telecommunication Sciences 2. Intelligent Transportation Systems Interactive Video Data Services Intelligent Vehicle Highway Systems Intel Video Interactive interactive voice response 1. interactive voice service 2. interactive video service interworking intelligent workstation interexchange carrier

J JAD JAMSAT JAN JANET JAR JARL JATE

joint application design Japanese affiliate of AMSAT Joint Army-Navy Joint Academic Network Java Archive Japan Amateur Radio League, Inc. Japan Approvals Institute for Telecommunications Equipment JCL Job Control Language JDBC Java database connectivity JEDEC Joint Electron Device Engineering Council JEDI Joint Electronic Document Interchange JEIDA Japan Electronic Industry Development Association JEMA Japan Electronic Messaging Association JIPS JANET Internet Protocol (IP) Service JPS joint product specification JRG GII Joint Rapporteur Group global information infrastructure JTAG Joint Test Action Group JTAPI Java JTC Joint Technical Committee JUNET Japan Unix Network JVNCnet John Von Neumann Center network JWICS Joint Worldwide Intelligence Communications System

K kbps KBS KDD keV KIS KISS KMID KMS KNET KQML KS KSR

kilobits per second. One thousand bits per second. This is sometimes also written kbits/s. knowledge base system 1. Knowledge Discovery in Databases 2. Kokusai Denshin Denwa Company, Ltd. kiloelectronvolt Knowbot Information Service Keep It Simple Stupid key material identifier Knowledge Management System Kangaroo Network Knowledge Query and Manipulation Language Kearney System Keyboard Send/Receive

KTH KTI KTS KWH

Kungliga Tekniska Hogskolan Key Telephone Interface key telephone system kilowatt-hour

L LAC ladar LADS LADT LAM LAMA LAN LANCE LANDA LB LBA LCD LCP LCU LDAP LDIP LDMS LE LEAF LEC LECS LED LIT LLC LM LMOS LMS LMSS LMU LNA LOC LPC LPFM LPTV LRC LRN LRS LSDU LSI LSN LSSC LSSGR LSU LTB LTC LTE LTS LUN LZS LZW

Loop Assignment Center laser Doppler radar local area data service Local Area Data Transport line adapter module Local Automatic Message Accounting local area network Local Area Network Controller for Ethernet Local Area Network Dealers Association leaky bucket Logical Block Address liquid crystal display Link Control Protocol Lightweight Computer Unit Lightweight Directory Access Protocol Long Distance Internet Provider Local Multipoint Distribution Service light-emitting Law Enforcement Access Field 1. Local Exchange Carrier 2. LAN Emulation Client LAN Emulation Configuration Server light-emitting diode line insulation test Logical Link Control 1. linear modulation 2. long distance marketer Loop Maintenance Operations System 1. Local Measured Service 2. Local Message Switch 3. Location and Monitoring Service Land Mobile Satellite Service Line Monitor Unit low noise amplifier Loss of Cell linear predictive coding low-power FM low-power television, low-power TV longitudinal redundancy check Location Routing Number line repeater station Link layer Service Data Unit large scale integration Large Scale Networking group lower sideband suppressed carrier LATA Switching System General Requirements Logical Storage Unit Last Trunk Busy Line Trunk Controller Line Terminating Equipment Loop Testing System logical unit number Lempel-Ziv-Stac Lempel-Ziv-Welsh

M MAC

1. Media Access Contro 2. multiplexed analog component MACE Macintosh Audio Compression and Expansion MARISAT Maritime Satellite MARS Multicast Address Resolution Service. In ATM networking, a protocol used in IP multicasting MAS Multiple Address Service MCF Multimedia Communications Forum MCMS Multimedia Cable Network System MD-IS Mobile Data Intermediate System MDF main distribution frame MDT mobile data terminals MFJ Modified Final Judgment MFS Metropolitan Fiber Systems

MFSK MHEC MHS MIB MICR MIDP MILNET MIME MIN MIND MIP MIPG MIPS MIS MITS MJ MLA MLS MMCF MMCX MMDS MME MMF MMI MMIC MMSP MMSS MMTA MMU MMX MNLP MNP MNRP MP MPLS MPOA MPOE MPP MPT MRI MRU MS MSAT MSB MSC MSK MSNF MSP MSS MSU MTA MTBF MTI MTM MTS MTSO MTTR MUX MVIP MVL MVS MXR MZI

multiple frequency shift keying Midwestern Higher Education Commission Message Handling System Management Information Base magnetic ink character recognition mobile information device profile Military Net Multipurpose Internet Mail Extension Mobile Identification Number Magnetic Integrator Neuron Duplicator Multichannel Interface Processor Multiple-Image Portable Graphics million instructions per second Management Information Services Micro Instrumentation and Telemetry Systems modular jack mail list agent microwave landing system Multimedia Communications Forum Multimedia Communication Exchange microwave multi-point distribution system Mobility Management Entity multimode optical fiber machine-to-machine interface Monolithic Microwave Integrated Circuit modular multi-satellite preprocessor Maritime Mobile-Satellite Service Multimedia Telecommunications Association 1. Manned Maneuvering Unit 2. memory management unit 1. Multimedia Extension. 2. Matrix Math Extension Mobile Network Location Protocol Microcom Networking Protocol Mobile Network Registration Protocol Multilink Protocol Multiprotocol Label Switching MultiProtocol Over ATM Minimum Point of Entry Multichannel Point-to-Point Protocol Ministry of Posts and Telecommunications magnetic resonance imaging maximum receive unit Mobile Station Mobile Satellite most significant bit, most significant byte Mobile Switching Center minimal shift keying multisystem networking facility Message Security Protocol multispectral scanner 1. microwave sounding unit 2. mobile subscriber unit 1. Macintosh Telephony Architecture 2. Major Trading Area 3. Message Transfer Agent 4. Metropolitan Trading Area mean time between failures Moving Target Indication Maintenance Trunk Monitor 1. member of technical staff 2. Message Telecommunications Service 3. Message Transfer System Mobile Telephone Switching Office mean time to repair multiplexer Multi-Vendor Integration Protocol Multiple Virtual Line Multiple Virtual Storage 1. mixer 2. multiplexer Mach-Zehnder Interferometer

N NAB NACN NADF NAK

1. National Alliance of Business 2. National Association of Broadcasters North American Cellular Network 1. North American Directory Plan 2. North Atlantic Directory Forum negative acknowledge

NAMPS NANC NANOG NANP NAP NAPP NAPT NARTE

Narrowband Analog Mobile Phone Service North American Numbering Council North American Network Operators Group North American Numbering Plan Network Access Point National Aerial Photography Program Native American Public Telecommunications, Inc. National Association of Radio and Telecommunications Engineers NAS network authentication server NASA National Aeronautics and Space Administration NASTD National Association of State Telecommunications Directors NATA North American Telecommunications Association NATOA National Association of Telecommunications Officers and Advisors NBC National Broadcast Corporation NBFM narrowband frequency modulation NBMA non-broadcast multiple access NCAR National Center for Atmospheric Research NCC 1. National Communications Committee 2. National Coordinating Center NCCS Network Control Center System NCHPC National Consortium for High-Performance Computing NCIA native client interface architecture NCO National Coordination Office for Computing, Information, and Communications NCOP Network Code Of Practice NCS National Communications System NCSA National Center for Supercomputing Applications NCUG National Centrex Users Group NDCDB National Digital Cartographic Data Base NDIS Network Driver Interface Specification NDSI National Spatial Data Infrastructure NDT No Dial Tone NE network element NECA National Exchange Carrier Association NENA National Emergency Number Assocation NFCB National Federation of Community Broadcasters NGDC National Geophysical Data Center NGDLC Next Generation Digital Loop Carrier NGI Next Generation Internet NGSO non-geostationary orbit NGSO FSS non-geostationary orbit fixed satellite service NHK Nippon Hoso Kyokai NHRP Next Hop Resolution Protocol NIDS network intrusion detection system NIMA National Imagery Mapping Agency NiMH nickel metal hydride NIOD Network Inward/Outward Dialing NIOSH National Institute of Occupational Safety and Health NIS 1. Network Imaging Server 2. Network Information Service NISDN 1 National ISDN-1 NISP National Internet Services Provider NIST National Institute of Standards and Technology NITF National Image Transfer Format NIU network interface unit NIUF North American ISDN Users Forum NLA Network Layer Address NLANR National Laboratory for Applied Network Research NLPID Network Layer Protocol ID NLQ near letter quality NMAA National Multimedia Association of American NMACS Network Monitor and Control System NMP 1. Network Management Processor 2. Network Management Protocol NMR nuclear magnetic resonance NNI 1. network node interface 2. Nederlands Normalisatie-Instituut NNTP Network News Transfer Protocol NNX NXX NO OP no operation NOP, nop no operation NOV News Overview. NOWT Netherlands Observatory for Science and Technology

NPA

1. National Pricing Agreement AT&T agreement 2. Numbering Plan Area NPBA National Public Broadcasting Archives NPR National Public Radio NRC 1. National Research Council 2. Network Reliability Council 3. non-recurring charge NREN National Research and Education Network NRSC National Radio Systems Committee NRZ non-return to zero NSAI National Standards Authority of Ireland NSAP network service access point NS/EP National Security/Emergency Preparedness NSF National Science Foundation NSFNET National Science Foundation Network NSP 1. National Internet Services Provider 2. Native Signal Processing NSS National Standards System NSSN National Standards Systems Network NSTAC National Security Telecommunications Advisory Committee NT Northern Telecom, Inc. NTIA National Telecommunications and Information Administration NTN Network Terminal Number NTSC National Television System Committee nV abbrev. nanovolt NV Network Video NVM nonvolatile memory

O OA OAI OAM

office automation Open Application Interface 1. operations, administration, and maintenance 2. Operations and Maintenance OAM&P operation, administration, maintenance and provisioning. OAO orbiting astronomical observatory OAS Organization of American States OBRA Omnibus Budget Reconciliation Act OC 1. operator centralization 2. optical carrier OCC Other Common Carrier OCP operator control panel OCR 1. optical character recognition 2. Outgoing Call Restriction ODBC Open Database Connectivity ODMG Object Database Management Group ODP open distributed processing OHR optical handwriting recognition OLE Object Linking and Embedding OLIU Optical Line Interface Unit OLNS Originating Line Number Screening OM Operational Measurement OMA Object Management Architecture OMAT Operational Measurement and Analysis Tool OMG Object Management Group ONA Open Network Architecture ONAC Operations Network Administration Center ONAL Off Network Access Line OOP object-oriented programming OPAC Outside Plant Access Cabinet OQPSK offset quadrature phase shift keying ORB Object Request Broker ORBCOMM Orbital Communications OSF Open Software Foundation (now the Open Group) OSI Open Systems Interconnection OSI TP Open Systems Interconnection Transport Protocol OSP Operator Service Provider OST Office of Science and Technology OSTA Optical Storage Technology Association OSTP Office of Science and Technology Policy OT Office of Telecommunications OTA Office of Technology Assessment (U.S.) OTAR over the air rekey OTGR Operations Technology Generic Requirements OTH over the horizon OTOH “on the other hand”

OTP OUI

Office of Telecommunications Policy Organizationally Unique Identifier

P pA PA PABX PACA PAP PAR

Abbreviation for picoampere public address system Private Automatic Branch Exchange Priority Access and Channel Assignment 1. packet-level procedure 2. Public Access Profile 1. Positive Acknowledgment Retransmit 2. Precision Approach Radar PCA 1. point of closest approach 2. Premises Cabling Association 3. protective connecting arrangement PCB 1. power control box 2. process control block 3. printed circuit board 4. protocol control block PCCA Portable Computer and Communications Association PCI 1. Peripheral Connect Interface 2. Protocol Control Information PCIA Personal Communications Industry Association PCL printer control language PCM pulse code modulation PCMCIA Personal Computer Memory Card Interface Association PCMIA Personal Computer Manufacturer Interface Adaptor PCN Personal Communication Network PCP 1. Predictor Compression Protocol 2. Private Carrier Paging PCR 1. peak cell rate 2. Program Clock Reference PCS 1. Personal Communications Service 2. personal communications software PDA Personal Digital Assistant PDF Portal Document Format PDL page description language PDP 1. plasma display panel 2. power distribution panel PDU Protocol Data Unit PDUS Primary Data User Station PER Packed Encoding Rules PLAR Private Line Automatic Ringdown PLC Power Line Carrier PLCP Physical Layer Convergence Procedure PL/M Programming Language/Microprocessor PLMR Private Land Mobile Radio PLS physical layer signaling PLU Percent Local Usage PM performance monitoring PMA physical medium attachment PMARS Police Mutual Aid Radio System PMR 1. poor man’s routing 2. private mobile radio PMRS Private Mobile Radio Service PMS 1. Pantone Matching System 2. Picturephone Meeting Service PMT 1. Photo Multiplier Tube 2. Photo Mechanical Transfer PNM public network management PnP Plug and Play PNP Permanent Number Portability PODP Public Office Dialing Plan PPDN Public Packet Data Network PPI 1. pixels per inch 2. plan position indicator PPP Point-to-Point Protocol PPS 1. packets per second 2. Path Protection Switched 3. Precise Positioning Service 4. pulses per second PPSN Public Packet Switched Network PPTP Point-to-Point Tunneling Protocol PRAM programmable random access memory PRB Private Radio Bureau PRI Public Radio International PSAP Public Safety Answering Point PSI 1. packet switching interface 2. Policy Studies Institute PSK phase shift keying PSTN Public Switched Telephone Network PSU Packet Switch Unit PSWAC Public Safety Wireless Advisory Committee

PSWN PTE PTFE PTI PTN PTO PTS PTT PVC PVCC PVN pW PWB PWM PWR

Public Safety Wireless Network SONET path terminating element polytetrafluoroethylene Payload Type Identifier Public Telecommunications Network public telecommunication operators 1. Personal Telecommunications System 2. Presentation Time Stamp 3. Public Telecommunications System Post Telephone & Telegraph administration 1. permanent virtual connection 2. polyvinyl chloride Permanent Virtual Channel Connection private virtual network picowatt printed wire board pulse width modulator power

Q QDU QFC QFM QIC QL QLLC QMS QoR QoS QPSK QSAM QSDG QTAM QTC

quantizing distortion units Quantum Flow Control quadrature frequency modulation Quarter Inch Cartridge Drive Standards query language Qualified Logical Link Control Queue Management System Query on Release quality of service 1. quadrature phase shift keying 2. quaternary phase shift keying quadrature sideband amplitude modulation Quality of Service Development Group Queued Telecommunications Access Method Quick Time Conference

R R/T R&D R&E RA RA# RAC RACE RACES RACF RARP RAS RASC raser RB RBOC RBS RCA RCC RD RDF RDT RDY REN RES RF RFC RFD RFE RFI RIF RIFF RJE RLCM RLE RLP RM RMA

realtime research and development Research and Education 1. real audio 2. return authorization return authorization number Radio Amateurs of Canada 1. random access computer equipment 2. Research into Advanced Communications in Europe Radio Amateur Civil Emergency Service resource access control facility Reverse Address Resolution Protocol remote access server Radio Amateur Satellite Corporation radio amplification by stimulated emission of radiation reverse battery Regional Bell Operating Company robbed-bit signaling Radio Corporation of America Radio Common Carrier routing domain 1. radio direction finding 2. rate decrease factor 1. recall dial tone 2. remote digital terminal ready Ringer Equivalent Number Residential Enhanced Service radio frequency Request for Comments Request For Discussion Radio Free Europe radio frequency interference rate increase factor Resource Interchange File Format remote job entry Remote Line Concentrating Module run length encoding Radio Link Protocol Resource Management returned merchandise authorization

rms RNC RNX ROLC ROM ROSE ROTFL RPC RPG RPM RPOA RPS RPW RQS RR RS RSA RSC RSGB RSUP RSVP RT RTC RTCP RTF RTFM RTNDA RTP RTS RTSP RTV RU

root mean square radio network controller Restricted Numeric Exchange Routing Over Large Clouds read only memory Remote Operations Service Element “rolling on the floor, laughing” remote procedure call Report Program Generator Remote Packet Module Recognized Private Operating Agency repetitive pattern suppression remotely piloted vehicle Rate Quote System Radio Regulations recommended standard Rural Service Area Remote Switching Center Radio Society of Great Britain Reliable SAP Update Protocol Internet Reservation Protocol 1. realtime, real time 2. remote terminal 3. reorder tone 1. return to control 2. runtime control Real Time Conferencing Protocol Rich Text Format “read the freaking manual” Radio-Television News Directors Association 1. realtime protocol 2. routing table protocol Request to Send Real Time Streaming Protocol realtime video 1. request unit 2. response unit 3. request/response unit

S S-HTTP S/MIME S/W SA SAA

Secure HTTP Secure Multipurpose Internet Mail Extension software 1. Service Agent 2. source address 1. Standards Association of Australia 2. Supplemental Alert Adapter 3. Systems Application Architecture SAFE Security and Freedom through Encryption SAFE Act Security and Freedom through Encryption Act SAGE Semi-Automatic Ground Environment SAIL Stanford Artificial Intelligence Laboratory SAM security accounts manager SAN satellite access node SANZ Standards Association of New Zealand SAP Service Access Point SAPI Service Access Point Identifier SAR 1. search and replace 2. segmentation and reassembly SART search and rescue radar transponder SAS 1. single address space 2. simple attachment scheme 3. Survivable Adaptive Systems SASL Simple Security and Authentication Layer SASMO Syrian Arab Organization for Standardization and Metrology SASO Saudi Arabian Standards Organization SATCOM Satellite Communications SCC Specialized Common Carrier SCCP Signaling Connection Control Part SCE Service Creation Environment SCI Scalable Coherent Interface SCP 1. Satellite Communications Processor 2. Service Control Point SCR 1. silicon-controlled rectifier 2. sustainable cell rate 3. System Clock Reference SCSI Small Computer System Interface SCT Secretaria de Comunicaciones y Transportes SCTE Society of Cable Telecommunications Engineers, Inc. SDL Specification and Design Language

SDLC SDN SDNS SDTP SEAC SEAL SET SETI SIMM SIPP SIS SIT SITA

Synchronous Data Link Control Software Defined Network Secure Data Network System Serial Data Transport Protocol Standards Eastern Automatic Computer Simple and Efficient Adaptation Layer secure electronic transaction Search for ExtraTerrestrial Intelligence single inline memory module Simple Internet Protocol Plus Standardiseringen i Sverige Simple Internet Transition Société Internationale de Télécommunications Aéronautiques SLAR side-looking airborne radar SLC simple line code SLIP Serial Line Interface Protocol SLM System Load Module SLP Service Location Protocol SLR 1. send loudness rating 2. single lens reflex SMAS switched maintenance access system SMATV Satellite Master Antenna Television SMDS Switched Multi-Megabit Digital Service SME 1. Security Management Entity 2. Small- and medium-sized enterprises SMI Structure of Management Information SMPTE Society of Motion Picture and Television Engineers SMR Specialized Mobile Radio SMRP Simple Multicast Routing Protocol SMS 1. Service Management System 2. Short Message Service SMTP Simple Mail Transfer Protocol SNA Systems Network Architecture SNACP SNA Control Protocol SNR signal-to-noise ratio SOC 1. society 2. system-on-chip SPCAS SPC Allocation Service SPEC Standard Performance Evaluation Corporation SPHIGS Simple PHIGS SPI 1. Security Parameters Index 2. Service Provider Interface SPID Service Profile Identifier SPIE The International Society for Optical Engineering SRA system reliability architecture SRAPI Speech recognition API SRGP Simple Raster Graphics Package SS7 Signaling System 7 SSB single sideband SSCS Service Specific Convergence Sublayer SSEC Selective Sequence Control Computer SSL Secure Socket Layer SSO single sign-on SSP Service Switching Point SSRP Simple Server Redundancy Protocol SSTO Single-Stage to Orbit SSTV slow scan television ST 1. Scheduled Transfer 2. signaling terminal 3. straight-tipped 4. systems test STA 1. spanning tree algorithm 2. Science and Technology Agency STAR TAP Science, Technology, And Research Transit Access Point STSK Scandinavian Committee for Satellite Telecommunications STU Secure Telephone Unit STU-3 Secure Telephone Unit 3 STUN serial tunnel SUMAC SuperHIPPI Media Access Controller SUT 1. System Under Test 2. Service User Table SVC switched virtual connection SVD simultaneous voice and data SVGA Super Video Graphics Array SWAC Standards Western Automatic Computer SWR standing wave ratio SXGA super-extended graphics array

T TAB TAI TAS TAXI Tc TCAP TCI TCIF TCM TCO TCP/IP TDI TDM TDMA TDRSS TENET TFT TFTP THF TIES TIFF TIIAP TJF TL TLF TLP TLV TM TMA TMC TMGB TMN TMSI TOGAF TP TPA TPDU TPI TPWG TQM TR TRS TSACC TSAG TSAP TSO TSRM TTA TTAB TTC TTIB TTL TTS TU TUANZ TUBA TUG TUI TUR TVM TVRO TWS TWT TWX Tx, TX

tone above band International Atomic Time Telecommunication Authority of Singapore Transparent Asynchronous Transmitter/Receiver Interface Committed Rate Measurement Interval Transaction Capability Application Part Telecommunications, Inc. Telecommunications Industry Forum trellis code modulation Tandem Connection Overhead Transmission Control Protocol/Internet Protocol Trade Data Interchange time division multiplexing time division multiple access Tracking and Data Relay Satellite System Texas Educational Network thin film transistor Trivial File Transfer Protocol tremendously high frequency 1. Telecom/Information Equipment and Services 2. Telecom Information Exchange Services Tag Image File Format Telecommunications and Information Infrastructure Assistance test jack frame tie line trunk link frame Transmission Level Point type, length, value 1. terminal multiplexer 2. traffic management Telecommunication Managers Association traffic management center Telecommunications Main Grounding Busbar Telecommunications Management Network Temporary Mobile Station Identifier The Open Group Architectural Framework twisted pair Telephone Pioneers of America Transport Protocol Data Unit tracks per inch Technology Policy Working Group total quality management transmit/receive Telephone Relay Service, telephone relay system Telecommunications Standards Advisory Council of Canada Telecommunication Standardization Advisory Group Transport Service Access Point time share operation Telecommunication Standards Reference Manual Telecommunications Technology Association transparent tone above band Telecommunications Technology Committee transparent tone in band transistor-transistor logic text-to-speech traveling user Telecommunications Users Association of New Zealand TCP and UDP with Bigger Address Telecommunication User Group telephone user interface Traffic Usage Recorder time-varying media television receive-only two-way simultaneous traveling-wave tube Teletype-Writer Exchange transmit

U UA

User Agent

UART UAS UAV UAWG UBR UCA UCC UCF UCM UDI UDLC UDP UECT UHF UI UL ULP UML UMSP UMTS UNC UNE UPCS UPL UPP URA URC URI URL URM URN USB USDC USDLA USDN USGS USITA USKA USOC USOP USTA UTC UTDR UTM UTR UTS UUI UV UWB UWC UWCC

universal asynchronous receiver-transmitter User Agent server unstaffed aerial vehicle Universal ADSL Working Group unspecified bit rate Utilities Communications Architecture Uniform Commercial Code UNIX Computing Forum 1. universal controller module 2. Universal Call Model unrestricted digital information Universal Digital Loop Carrier User Datagram Protocol Universal Encoding Conversion Technology ultra high frequency 1. Unix International 2. user interface Underwriters Laboratories Inc. upper layer protocol. Unified Modeling Language Unified Memory Space Protocol Universal Mobile Telecommunications Systems Universal Naming Convention Unbundled Network Element Unlicensed Personal Communcations Services upper layer protocol Universal Payment Preamble Uniform Resource Agent Uniform Resource Characteristic Uniform Resource Identifier Uniform Resource Locators user request manager Uniform Resource Name Universal Serial Bus U.S. Digital Cellular United States Distance Learning Association U.S. ISDN United States Geological Survey Formerly United States Independent Telephone Association Union Schweizerischer Kurzwellen-Amateure Union (Union of Swiss Shortwave Amateurs) Universal Service Order Code User Service Order Profile United States Telephone Association Coordinated Universal Time Universal Trunk Data Record Universal Transverse Mercator Universal Tone Receiver Universal Telephone Service 1. Unified User Interface 2. unique user identifier 3. user-to-user indicator ultraviolet ultra wideband Universal Wireless Communications Universal Wireless Communications Consortium

V VOR VP VPC VPN VQ VRAM VRML VSAT VSX VTP VTS

VHF omnidirectional range virtual path virtual path connection virtual private network vector quantization Video RAM Virtual Reality Modelling Language Very Small Aperture Terminal Verification Suite for X/open Virtual Trunking Protocol Vehicular Technology Society

W W-CDMA W-DCS W3 W3C WAAS

wireless Code Division Multiple Access wideband digital cross-connect system World Wide Web World Wide Web Consortium Wide Area Augmentation System

WABI WACK WACS WAG WAIS WAN WANMC WARC WATM WATS WATTC

Windows Application Binary Interface wait acknowledgment White Alice Communications System Wireless Applications Group Wide Area Information Server Wide Area Network Wide Area Network Management Center World Administrative Radio Conference Wireless ATM Wide Area Telephony Service World Administrative Telegraph and Telephone Conference WBC wide-band channel WBEM Web-Based Enterprise Management WCAV Web Clipping Application Viewer WCP 1. Web Clipping proxy 2. Wireless Certificate Profile 3. wireless communication platform 4. wireless communications protocol WDGPS wide area differential GPS WDL Windows Driver Library WDM wave division multiplexing WDMA wavelength-division multiple access WDP 1. Wireless Datagram protocol 2. Workforce Development Program WFS Woodstock File Server WFWG Windows For Workgroups WGDTB Working Group on Digital Television Broadcasting WGIH Working Group on Information Highway WGS World Geodetic System WIA World Internetworking Alliance WIM WAP Identity Module WIN Wireless Intelligent Network WIN95 Windows 95 WINF Wireless Information Networks Forum, Inc. WIP Washington Internet Project WITS Wireless Interface Telephone System WLAN wireless local area network WLI Forum Wireless LAN Interoperability Forum WLL Wireless Local Loop WLRL Wireless LAN Research Laboratory WML 1. Website Meta Language 2. Wireless Markup Language WOM write-only memory WOMBAT waste of money, brains, and time WORA write once run anywhere WOSA Windows Open Services Architecture WOTAN Wavelength-Agile Optical Transport and Access Network WRAM Windows Random Access Memory WRC World Radiocommunication Conference WRS Worldwide Reference System WRT “with respect to” WSA Wireless Specialty Apparatus Company WSC wireless switching center WSP Web Service Provider WST WAP Security Toolkit WTAC World Telecommunications Advisory Council WTB Wireless Telecommunications Bureau WTO World Trade Organisation WTPF World Telecommunication Policy Forum WWW World Wide Web WWWC World Wide Web Consortium WYGIWYD “what you got is what you deserve”

WYPFIWYG “what you pay for is what you get” WYSIWYG “what you see is what you get” WZ1 World Zone1

X XA Xbar XC XCA XCVR xd XDF XDMA XDMCP XDR XFN XFR XFS XGA

extended architecture crossbar cross connect extended communication adapter transceiver X-Bone xd extended distance feature Xing Distributed Media Architecture X Display Manager Control Protocol External Data Representation X/Open Federated Naming transfer X11 File System 1. extended graphics adapter 2. extended graphics array XID exchange identification XIP execute in place XIWT Cross-Industry Working Team Xlib X Library Xmission transmission Xmit transmit XML Extensible Markup Language XMP X/Open Management Protocol XMS Extended Memory Specification XMT transmit XNS Xerox Network Services XO crystal oscillator XPAD external packet assembler/disassembler XPG X/Open Portability Guide XPM Extended Peripheral Module Xponder transponder XRB transmit reference burst xref cross reference XRF Extended Recovery Facility XSG X.25 Service Group XSI X/Open System Interface Specification XSMP X Session Manager Protocol XT 1. crosstalk 2. IBM Personal Computer XT Xtal crystal Xtalk crosstalk XTI X/Open Transport Interface. X Window System XTL SunXTL XTP Express Transfer Protocol XUI X User Interface Toolkit XWA X-perimental Wireless Apparatus XWS X Window System

Y YAG YIG YMMV YP

yttrium-aluminum-garnet yttrium-iron-garnet “your mileage may vary” Yellow Pages

Z ZIP Ziv

Zone Information Protocol Lempel-Ziv

U.S. Area Codes (and N. A. Toll Free) 201 202 203 205 206 207 208 209 210 212 213 214 215 216 217 218 219 224 225 228 229 231 234 240 248 251 252 253 254 256 262 267 270 278 281 301 302 303 304 305 307 308 309 310 312 313 314 315 316 317 318 319 320

New Jersey (Hackensack, Newark, Jersey City) Washington, D.C. Connecticut (Bridgeport, New Haven, Stanford) Alabama (Birmingham) Washington (Seattle) Maine Idaho California (Fresno, Modesto) Texas (San Antonio) New York (Manhattan) California (downtown Los Angeles) Texas (Dallas) Pennsylvania (Philadelphia) Ohio (Cleveland) Illinois (Champaign/Urbana, Springfield) Minnesota (Duluth) Indiana (Gary, Hammond, Michigan City, South Bend) Illinois (Chicago suburbs) Louisiana Mississippi (Biloxi) Georgia Michigan Ohio Maryland (Hagerstown, Rockville) Michigan (Pontiac, Southfield, Troy) Alabama North Carolina Washington (Gig Harbor, Tacoma) Texas (Waco) Alabama Wisconsin Pennsylvania Kentucky Michigan Texas (Houston metro) Maryland (Hagerstown, Rockville) Delaware Colorado (Aurora, Boulder, Denver, Longmont) West Virginia Florida (Key West, Miami) Wyoming Nebraska (North Platte, Scottsbluff) Illinois (Peoria, Rock Island) Southern California (Beverly Hills) Illinois (Chicago central) Michigan (Dearborn, Detroit) Missouri (St. Louis) New York (Syracuse, Utica) Kansas (Dodge City, Wichita) Indiana (Indianapolis) Louisiana (Lake Charles, Shreveport) Iowa (Davenport, Dubuque) Minnesota (St. Cloud)

321 323 330 331 334 336 337 339 341 347 351 352 360 361 369 385 386 401 402 404 405 406 407 408 409 410 412 413 414 415 417 419 423 425 435 440 443 445 464 469 478 480 484 500 501 502 503 504 505 507 508 509 510 512 513 515 516

Florida California (L.A. surrounds) Ohio (Akron, Canton, Youngstown) Illinois (Chicago suburbs) Alabama (Montgomery) North Carolina Louisiana Massachusetts California (Oakland) New York (Brookland, Bronx, Queens) Massachusetts (Acton, Lowell) Florida (Gainesville) Washington State (Olympia, Vancouver) Texas California (Fairfield, Vallejo) Utah Florida Rhode Island Nebraska (Lincoln, Omaha) Georgia (Atlanta) Oklahoma (Enid, Oklahoma City) Montana Florida (Orlando) California (Monterey, San Jose) Texas (Beaumont, Galveston) Maryland (Annapolis, Baltimore) Pennsylvania (Pittsburgh) Massachusetts (Pittsfield, Springfield) Wisconsin (Milwaukee, Racine) California (San Francisco) Missouri (Joplin, Springfield) Ohio (Toledo) Tennessee (Chattanooga, Johnson City, Knoxville) Washington (Bellevue) Texas (Logan, Price, St. George) Ohio (Ashtavula, Lorain) Maryland (Annapolis, Baltimore) Pennsylvania (Philadelphia) Illinois (Chicago suburbs) Texas (Dallas) Georgia Arizona Pennsylvania (Allentown, Reading) Allocated to PCS Arkansas (Little Rock, Fort Smith) Kentucky (Frankfort, Louisville, Paducah, Shelbyville) Oregon (Astoria, Portland, Salem) Louisiana (Baton Rouge, New Orleans) New Mexico Minnesota (Rochester) Massachusetts (Fall River, Worcester) Washington (Spokane, Walla Walla, Yakima) Northern California (Fremont, Oakland) Texas (Austin, Corpus Christi) Ohio (Cincinnati, Middletown) Iowa (Des Moines) New York (Hempstead, Long Island)

NOTE: Regions indicated in parentheses are examples for reference and do not necessarily indicate all the regions within a given area code.

U.S. Area Codes & N.A. Toll Free, cont. 517 518 520 530 540 541 559 561 562 563 564 570 571 573 580 586 601 602 603 605 606 607 608 609 610 612 614 615 616 617 618 619 620 623 626 627 628 630 631 636 641 646 650 651 657 660 661 662 669 678 679 682 701 702

Michigan (Bay City, Jackson, Lansing) New York (Albany, Schenectady, Troy) Arizona (except Phoenix metro) California (Chico) Virginia (Roanoke) Oregon (Bend, Corvallis, Eugene, Medford, Pendleton) California Florida (West Palm Beach) California (Long Beach) Iowa Washington (Bellingham, Olympia) Pennsylvania (Scranton, Williamsport) Virginia (Arlington, Fairfax) Missouri (Columbia, Jefferson City) Oklahoma Michigan (Flint, Birmingham) Mississippi (Hattiesburg, Jackson) Arizona (Phoenix metro) New Hampshire South Dakota Kentucky (Kentucky, Winchester) New York (Binghamton, Elmira) Wisconsin (Madison) New Jersey (Atlantic City, Camden, Trenton, Vineland) Pennsylvania (Allentown, Reading) Minnesota (Minneapolis, St. Paul) Ohio (Columbus) Tennessee (Murfreesboro, Nashville) Michigan (Battle Creek, Grand Rapids, Kalamazoo) Massachusetts (Boston central) Illinois (Alton, Cairo, Mt. Vernon) California (San Diego) Kansas Arizona California California (Napa, Petaluma) California (San Francisco) Illinois (Chicago central suburbs, Elgin, Waukegan) New York Missouri Iowa New York California (Palo Alto) Minnesota California (Anaheim) Missouri (Kirksville) California Mississippi California (San Jose) Georgia (Atlanta metro, Marietta, Norcross) Michigan (Detroit) Texas (Arlington, Fort Worth) North Dakota Nevada

703 704 706 707 708 710 712 713 714 715 716 717 718 719 720 724 727 732 734 740 747 752 754 757 760 763 764 765 770 773 774 775 781 785 786 800 801 802 803 804 805 806 808 810 812 813 814 815 816 817 818 822 828 830 831

Virginia (Alexandria, Arlington) North Carolina (Asheville, Charlotte) Georgia (Augusta, Columbus, Rome) California (Eureka) Illinois (Chicago south suburbs) U.S. Government restricted access Iowa (Council Bluffs, Sioux City) Texas (Houston) California (Anaheim) Wisconsin (Eau Claire, Wausau) New York (Buffalo, Niagara Falls, Rochester) Pennsylvania (Harrisburg, Scranton, WilkesBarre) New York City (Bronx, Brooklyn, Queens, Staten Island) Colorado (Colorado Springs, Leadville, Pueblo) Colorado Pennsylvania (Letrobe, Newcastle) Florida New Jersey (New Brunswick, Piscataway) Michigan (Ann Arbor, Livonia) Ohio (Athens, Marietta) California (Van Nuys) California (Pomona) Florida Virginia (Norfolk, Virginia Beach) California (Barstow, Palm Springs) Minnesota California (Mountain View) Indiana (Anderson, Lafayette) Georgia (Atlanta metro, Marietta, Norcross) Chicago (outside central) Massachusetts Nevada Massachusetts (Boston suburbs) Kansas (Lawrence, Salina, Topeka) Florida Toll free Utah (Ogden, Provo, Salt Lake City) Vermont South Carolina (Columbia) Virginia (Charlottesville, Newport News, Richmond) California (Bakersfield, Santa Barbara) Texas (Amarillo, Lubbock) Hawaii Michigan (Flint) Indiana (Evansville) Florida (Clearwater, St. Petersburg, Tampa) Pennsylvania (Altoona, Erie) Illinois (La Salle, Rockford) Missouri (Kansas City, St. Joseph) Texas (Fort Worth) California (Glendale, Pasadena) Toll free North Carolina Texas (Del Rio, Fredericksburg, New Braunfels) California (Salinas)

NOTE: Regions indicated in parentheses are examples for reference and do not necessarily indicate all the regions within a given area code.

832 833 835 843 844 845 847 850 855 856 857 858 859 860 863 864 865 866 870 888 900 901 903 904 906 907 908 909 910 912 913 914 915 916 917 918 919 920 925 931 937 940 941 947 949 951 952 954 956 970 972 973 978 979 980 985 989

Texas (Houston) Reserved for toll free Pennsylvania (Allentown, Reading) South Carolina (Charlestown, Florence) Reserved for toll free New York Illinois (Chicago north suburbs, Elgin, Waukegan) Florida (Pensicola, Tallahassee) Toll free New Jersey Massachusetts California Kentucky Connecticut (Hartford) Florida (Arcadia, Lakeland) South Carolina (Greenville, Spartanburg) Tennessee (Knoxville) Toll free Arkansas (Jonesboro, Pine Bluff) Toll free Pay services Tennessee (Memphis) Texas (Tyler) Florida (Daytona Beach, Jacksonville) Michigan (Marquette, Sault St. Marie) Alaska New Jersey (Elizabeth, Plainfield) California (Riverside, San Bernardino) North Carolina (Fayetteville, Greensboro, Winston-Salem) Georgia (Albany, Savannah) Kansas (Atchison, Kansas City) New York (Peekskill, Poughkeepsie, White Plains, Yonkers) Texas (Abilene, El Paso) California (Sacramento) New York (newer wireless) Oklahoma (Tulsa) North Carolina (Durham, Raleigh) Wisconsin (Fond du lac, Green Bay, Sheboygan) California (Concord) Tennessee (Clarksville, Columbia, Cookeville) Ohio (Dayton/Springfield) Texas (Denton, Wichita Falls) Florida (Fort Meyers, Naples, Sarasota) Michigan (Oakland County) California (Irving) Corona (Riverside) Minnesota Florida (Ft. Lauderdale) Texas (Brownsville, Laredo) Colorado (Aspen, Durango, Grand Junction, Steamboat Springs) Texas (Dallas metro) New Jersey (Morristown, Newark, Paterson) Massachusetts (Lowell) Texas (Freeport) North Carolina (Charlotte) Louisiana Michigan (Midland, Saginaw)

Area Codes for U.S. Territories, Caribbean, and Canada U.S. Territories & Caribbean 242 246 264 268 284 340 345 441 473 649 664 670 671 758 767 784 787 809 868 869 876

Bahamas Barbados Anguilla Antigua, Barbuda British Virgin Islands U.S. Virgin Islands Cayman Islands Bermuda Grenada Turks, Caicos Montserrat North Mariana Island Guam St. Lucia Dominica St. Vincent, Grenadines Puerto Rico Domincan Republic Trinidad, Tobago St. Kitts, Nevis Jamaica

Canada 204 250 306 403 416 418 450 506 514 519 604 613 647 705 709 807 819 867 870 902 905

Manitoba British Columbia (Prince George, Vancouver Island) Saskatchewan Alberta (Calgary, Red Deer), Yukon Ontario (Toronto metro) Quebec (Quebec City) Quebec (Montreal surrounds) New Brunswick Quebec (Montreal metro) Ontario (London) British Columbia (Vancouver) Ontario (Ottawa) Reserved for Ontario Ontario (North Bay, Sault St. Marie) Newfoundland and Labrador Ontario (Thunder Bay) Quebec (Sherbrooke) Northwest Territories, Yukon Territory Alberta (Edmonton) Nova Scotia, Prince Edward Island Ontario (Hamilton, Mississauga, Niagara Falls)

NOTE: Regions indicated in parentheses are examples for reference and do not necessarily indicate all the regions within a given area code.

Dialing Letter-Number Equivalents

Radio Communications Alphabet

Num.

Alphabetic Equivalent

Letter Name

Letter Name

1 2 3 4 5 6 7 8 9 0

U.S. --ABC DEF GHI JKL MNO PRS TUV WXY Operator

A B C D E F G H I J K L M

N O P Q R S T U V W X Y Z

U.K. --ABC DEF GHI JKL MN PRS TUV WXY OQ

There is no Q in U.S. systems and no Z in U.S. or U.K. systems. These letter-number equivalents are also found on ATMs.

International Morse Code Let. Code A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

•- ••• - •- • - •• • ••- • --• •••• •• •- - - ••- •• --• --•- - • - - ••- • ••• ••••••- - ••- •- - - ••

Let. Code Á Ä É Ñ Ö Ü 1 2 3 4 5 6 7 8 9 0 , . ? ; : / ' () _

•- - ••- •••- •• - - •- ---• ••- •- - - ••- - •••- ••••••••• - •••• - - ••• - - - •• ----• ----- - ••- •- •- •••- - •• - •- •- - - ••• - ••- • - •••••- - - - • - •- - •••- - •-

Adam Boy Charles David Edward Frank George Henry Ida John King Lincoln Mary

Nora Ocean Paul Queen Robert Sam Tom Union Victor William X-Ray Yellow Zebra

Metric Prefixes/Values Prefix Symb. Numerical Expression

Expon.

yottazettaexapetateragigamegakilohectodeca-

Y Z E P T G M k h da

1,000,000,000,000,000,000,000,000 1,000,000,000,000,000,000,000 1,000,000,000,000,000,000 1,000,000,000,000,000 1,000,000,000,000 1,000,000,000 1,000,000 1,000 100 10

1024 1021 1018 1015 1012 109 106 103 102 101

decicentimillimicronanopicofemtoattozeptoyocto-

d c m m n p f a z y

0.1 0.01 0.001 0.000001 0.000000001 0.000000000001 0.000000000000001 0.000000000000000001 0.000000000000000000001 0.000000000000000000000001

10¯1 10¯2 10¯3 10¯6 10¯9 10¯12 10¯15 10¯18 10¯21 10¯24

ASCII (Character and Control Codes) Oct

Dec Hex

Name

Oct

Dec Hex

Name

000 001 002 003 004 005 006 007 010 011 012 013 014 015 016 017 020 021 022 023 024 025 026 027 030 031 032 033 034 035 036 037 040 041 042 043 044 045 046 047 050 051 052 053 054 055 056 057 060 061 062 063 064 065 066 067 070 071 072 073 074 075 076 077

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63

NUL SOH STX ETX EOT ENQ ACK BEL BS HT LF VT FF CR SO SI DLE DC1 DC2 DC3 DC4 NAK SYN ETB CAN EM SUB ESC F G RS US space ! “ # $ % & , ( ) * + , . / 0 1 2 3 4 5 6 7 8 9 : ; < = > ?

0100 0101 0102 0103 0104 0105 0106 0107 0110 0111 0112 0113 0114 0115 0116 0117 0120 0121 0122 0123 0124 0125 0126 0127 0130 0131 0132 0133 0134 0135 0136 0137 0140 0141 0142 0143 0144 0145 0146 0147 0150 0151 0152 0153 0154 0155 0156 0157 0160 0161 0162 0163 0164 0165 0166 0167 0170 0171 0172 0173 0174 0175 0176 0177

64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127

@ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z [ \ ] ^ _ ‘ a b c d e f g h i j k l m n o p q r s t u v w x y z { | } ~ delete

0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x0a 0x0b 0x0c 0x0d 0x0e 0x0f 0x10 0x11 0x12 0x13 0x14 0x15 0x16 0x17 0x18 0x19 0x1a 0x1b 0x1c 0x1d 0x1e 0x1f 0x20 0x21 0x22 0x23 0x24 0x25 0x26 0x27 0x28 0x29 0x2a 0x2b 0x2c 0x2d 0x2e 0x2f 0x30 0x31 0x32 0x33 0x34 0x35 0x36 0x37 0x38 0x39 0x3a 0x3b 0x3c 0x3d 0x3e 0x3f

Control-C

backspace tab line feed, newline form feed, NP carriage return

XON, Control-Q XOFF, Control-S

escape

space exclamation mark double quote number sign, hash dollar percent ampersand apostrophe/quote open parenthesis close parenthesis asterisk, star plus comma minus period, full stop oblique stroke zero one two three four five six seven eight nine colon semicolon less than equals greater than question mark

0x40 0x41 0x42 0x43 0x44 0x45 0x46 0x47 0x48 0x49 0x4a 0x4b 0x4c 0x4d 0x4e 0x4f 0x50 0x51 0x52 0x53 0x54 0x55 0x56 0x57 0x58 0x59 0x5a 0x5b 0x5c 0x5d 0x5e 0x5f 0x60 0x61 0x62 0x63 0x64 0x65 0x66 0x67 0x68 0x69 0x6a 0x6b 0x6c 0x6d 0x6e 0x6f 0x70 0x71 0x72 0x73 0x74 0x75 0x76 0x77 0x78 0x79 0x7a 0x7b 0x7c 0x7d 0x7e 0x7f

commercial at sign

open square bracket backslash close square bracket caret underscore back apostrophe

open curly bracket vertical bar, pipe close curly bracket tilde delete

Numerals Telephone Prefix Calling Numbers/Services 0345 A ‘shared tariff’ telephone prefix and service offered by British Telecom to enable callers to pay local call rates no matter where the physical location of the number may be within the area covered by the company offering the service, e.g., within the U.K. This can provide businesses with a way to give information to callers responding to a marketing campaign, for example, in such a way that the caller bears part of the cost and thus will probably not call out of idle curiosity alone. It is an alternative to a 0800 number where the callee bears the full cost of the call. 0500 A reverse charge telephone service introduced by Mercury in the U.K. in 1992 that is similar to the British Telecom (BT) 0800 service. See 0800. 0645 A ‘shared tariff’ telephone service introduced by Mercury in the U.K. that is similar to the British Telecom (BT) 0345 service. See 0345. 070 A European national telephone services providing a subscriber (typically a business) with a portable number at which they can be reached from any calling location in the country. The caller pays for the call, based upon National Call rates. This is especially useful when a business moves, as directory listings, stationery, and other business identifiers don’t have to be changed to reflect a new number. 0800 A European ‘FreePhone’ service offered by WorldCom, Global Carrier Services, and others, similar to North American 800 service, that makes it possible for callers to call the 0800-prefixed number free of charge, with the company holding the 0800 number bearing the cost. It’s essentially a ‘collect’ or ‘reversed charge’ call that is put through directly as a continuing service, without going through operators or authorization to accept the call. Golden 0800 numbers are those that are inherently easy to remember (e.g., 0800 555 0000) or that correspond to a mnemonic (e.g., 0800 callnow). Most phone companies charge a premium for golden numbers but sometimes you get lucky. See 0345, 800. 0990 A national pay telephone service number prefix and telephone service offered in the U.K. by British Telecom (BT). It is similar to U.S. 900-prefix services that are typically billed by the minute. 0990 numbers are used for dating services, psychic-style

services, and sex services. Not all businesses using these numbers are ethical. They are required to play a recording to inform customers that they are being billed, but some ‘neglect’ this requirement. Some keep the caller on the line for a long time by asking personal questions or chatting, in order to increase the call duration and hence the charges. It is possible to make 0990 services accessible from Internet phone gateways (almost 1/3 of the call lines are accessed this way in the U.K.) and, once again, the vendor is required to inform the caller that they are being billed 0990 rates. Due to problems with enforcing ethical and legal 0990 services, in 2000 Nippon Telephone and Telegraph (NTT) reduced the maximum charges a vendor could accumulate for each 0990 call. 155 In the U.K., the British Telecom (BT) code for connecting with an international operator. 555-1212 In the U.S., a dialing sequence for contacting the Directory Assistance service (formerly the Information service) for obtaining long-distance publicly listed telephone numbers. It is useful for obtaining new numbers that may not yet be listed, or numbers published elsewhere geographically. Prior to the mid-1960s, the dialing code for Information was 113. Most North American telephone exchanges use this number as a standard. See 555-1212. 611 A telephone dialing code for contacting telephone maintenance and repair services to request assistance with telephone services and equipment. Unlike services prior to the mid-1960s, 611 numbers were used through a transitional period during which the phone company’s monopoly was challenged and subscribers began to select their own telephone equipment from third-party vendors and eventually were permitted to install or modify the line extending from the phone company’s line attachment point into the premises (depending upon the service and region). Thus, repair services didn’t just schedule the repair any more, they would query the 611 caller about the nature of the problem and try to guess whether it was being caused by the phone company’s line or service or the subscriber’s line and equipment. If it was suspected that the problem was with subscriber equipment, the phone company would warn the subscriber about minimum and hourly charges and then confirm whether they still wanted to call in

a repair person. This was more complicated than previous procedures but not nearly as complicated as what happened a couple of decades later with further deregulation and burgeoning carriers and phone services. 800 A service in which calls are billed to the receiver. 800 numbers are widely used by businesses to encourage potential buyers to contact the company through a toll-free 800 number (or 888 number) without concern about long distances charges. These services are sometimes used internally, through an unpublicized 800 number for traveling employees to contact their main office or branch. When 800 began to be in short supply, 888 and 877 prefixes/services were added to extend the available numbers. See 0800. 800 Service Management System (SMS/800) Functions A Federal Communications Commission (FCC) Tariff document published by the Bell Operating Companies (BOCs) to describe the regulations, rates, and charges applicable to the provision of SMS/800 functions and support services through intelligent telephone networks. See SMS/800. 877/877/866/855/844/833/822 Toll-free calling service prefixes that were developed to extend the availability of 800 numbers when 800 numbers assignments were nearing capacity. These numbers are sequentially opened as needed. See 800. 900/976 A set of numbers billed to the caller through a rate determined by the callee. 900 services are used by information brokers, public opinion pollers, advice counsellors, astrologers, other prognosticators, and by vendors offering phone sex. Charges for 900 calls usually range from $1.95 to $4.95 per minute. These calls are not only somewhat expensive, but some of the less scrupulous 900 vendors will keep the caller on the line longer by asking him or her many personal questions at the beginning of the call. It’s not unusual for the average call to be around $25 and often they are much more. Because of the abuse or overuse of 900 numbers, subscribers demanded a way to disable 900 calling and this is now provided by the phone companies. This is mainly to curtail calls by children, 900-addicts, and 900 calls by unauthorized callers using a phone without permission. See 0900. 911 calling A telephony service designed to expedite connections to emergency services such as medical services, law enforcement, and fire departments. By dialing only three easy-to-remember digits, subscribers can more easily get help when needed. This concept was first introduced in the 1970s. The calls are connected quickly to a Public Safety Answering Point (PSAP) where a trained emergency dispatcher records the call, determines the origin and nature of the call, responds to the caller, and dispatches services as needed. 1571 In the U.K., the British Telecom (BT) standard telephone message retrieval number. 1660 In the U.K., the British Telecom (BT) Worldcom access number.

Telephone Quick-Dial Numbers 112 In Europe, the British Telecom (BT) standard emergency telephone number. The number 17099 is an alternate emergency code. See 911. 113 Historically, in the U.S., a telephone dialing sequence for contacting Information Services, a service that aided subscribers in getting publicly listed phone numbers that were not in the current directory (e.g., new numbers). In the mid-1960s, in North America this code was changed to 411. There are other countries where the use of 113 has been retained. For example, in Copenhagen, it is used for overseas directory inquiries. See 411. 114 Historically, in the U.S., a telephone dialing sequence for contacting telephone maintenance and repair services. If you had trouble with your line, you called 114. Since most people had only one phone in those days, you usually went next door to dial from your neighbor’s phone while sitting down for a cup of coffee and a chat. The repair people would schedule a visit and repair the problem. It was a simpler process in those days. Not only was the telephone network far more homogenous than now, but the phone company owned the line and the equipment right up to the phone itself and thus could standardize hardware and procedures for making repairs. In the mid-1960s, the dial sequence was changed to 611 and now local phone companies have a variety of numbers to dial for repair services. See 611. 411 In telephony, a short dialing sequence for contacting the Directory Assistance service (formerly the Information service) for obtaining publicly listed telephone numbers that may not be listed in the local directory (or which the caller couldn’t find in the local directory). It is useful for obtaining new numbers that may not yet be listed, or numbers published elsewhere geographically. Prior to the mid-1960s, the dialing code for Information was 113. Historically, in some areas the service was free, but it became a pay service charged by the call. More recently, some phone companies offer bundled services that permit up to a specified number of Directory Assistance calls per time period (e.g., per week or month). Most North American telephone exchanges use this number as a standard. Until 2001, in most areas, a caller could request two numbers for about $.40 but deregulation resulted in increases of up to $1.99 for a single number, depending upon the service provider. (Some carriers still permit two or three calls free per month per subscriber.) As charges rise, it is likely that people will migrate to CD-ROM directories and Web-based directory services such as InfoSpace and Switchboard. See 555-1212.

Network Technologies 4B/5B Fiber transmissions cable that is commonly used in asynchronous transfer mode (ATM) and Fiber Distributed Data Interface (FDDI) networks. This 4-byte/5-byte multifiber cable can support transmission speeds up to about 100 Mbps. 6bone An IETF-supported international collaboration testbed providing policies and procedures for the evolution of Internet Protocol (IP). The name 6bone is derived from backbone a major ‘artery’ of the Internet, IP version 6. 6bone is designed to be used in the development, deployment, and evolution of the Internet Protocol Version 6 (IPv6) which is intended to succeed the current Internet protocol IPv4. This testbed and transition project is essential in that the Internet is not one machine and one agency running it, but a global collaboration of computing devices managed and owned by many different personal, commercial, and governmental entities. The 6bone provides not only a means to test the many features and concepts of the new systems, but also a means for developing and deploying a transition infrastructure. The 6bone is a virtual network that is layered on portions of the current physical structure of the IPv4based Internet. IPv4 routers are not designed to accommodate IPv6 packets. By layering IPv6 on the existing structure, the routing of IPv6 packets can be accomplished prior to the implementation of enhanced physical structures, particularly routers designed to take advantage of the features of IPv6. To understand the 6bone virtual structure, imagine various workstation-class computers, such as those commonly used as servers in various communities and institutions. Provide these machines with operating system support for IPv6 so that they have direct support for the IPv6 packets. Now provide a means through the Internet for these machines to interconnect and communicate with one another through virtual point-to-point links called tunnels, thus managing the links on behalf of physical routers until IPv6 support is more widespread. Eventually, as the Internet is upgraded to IPv6, this interim system will be replaced by agreement with direct physical and virtual IPv6 support. The 6bone Web site is sponsored by the Berkeley Lab Networking & Telecommunications Department. See IPv4, IPv6, MBone, X-Bone. http://www.6bone.net 8B/10B The designation for a fiber transmissions cable that is appropriate for high speed networks. This 8-byte/10-byte multifiber cable can support transmission speeds up to about 149.76 Mbps. 10Base- After ratification of Ethernet as a standard (IEEE 802.3), a number of variations were defined to support twisted pair and fiber optics physical media and data formats transmitting at rates of 10 MBps. 10Base-2 10 Mbps baseband ‘thin’ Ethernet 50ohm coaxial cable as a network physical transmissions medium. Up to 30 stations can be supported per cable segment. This format is popular for

small local area networks connecting personal computers. 10Base-5 10Base-5 is essentially Ethernet delivered over a standard or “thick” Ethernet 50-ohm cable at data rates of 10 Mbps. 10Base-FL 10-Mbps baseband fiber optic network links supporting transmission segments of up to two kilometers, with a maximum of two devices per segment (station and hub). Multiple stations may be connected through a hub in a star topology. There are commercial media converters available for connecting twisted pair (10BaseT) cables to 10Base-FL Ethernet-based networks to extend twisted pair cable lengths with optical connections. Converters may or may not be used in conjunction with regenerating repeaters. 10Base-T A physical transmissions medium that supports up to 10 Mbps of baseband transmissions over twisted pair (T) that is commonly interconnected with RJ-45 cables (the ones that have connectors that look like fat RJ-11 phone connectors). Three or more stations can be interconnected in a star topology through a hub (and stars can be interconnected through a ‘bus’ topology). It’s a convenient method of connection since the loss of a station in the star doesn’t bring down the rest of the network as in a ring topology. The Manchester scheme of binary coding is typically used with 10Base-T. 10Broad36 A multiple-channel network baseband signaling system that can be implemented over single or dual coaxial cables. The bandwidth is subdivided into two or more channels for the simultaneous transmission of different types of signals as might be found with multimedia communications. Segments can support transmission distances of up to 3600 meters per segment. 10 Gbit Ethernet 10GbE. A telecommunications technology developed within the IEEE 802.3ae working committee (a subcommittee of the IEEE 802.3 Ethernet Working Group), based upon the evolution of Ethernet/Fast Ethernet technologies. The project began in spring 1999 to extend and update the capabilities of Ethernet and was approved by ballot in March 2001, a milestone toward standards ratification that is expected in 2002. 10GbE differs from earlier versions in a couple of physical interface aspects. It includes a long-haul optical transceiver capable of 40 kilometers or more, or physical medium-dependent (PMD) interface for single-mode fiber. This can be used with either a LAN or WAN physical layer to support metropolitan area networks (MANs). Secondly, 10GbE includes an optional WAN physical (PHY), enabling 10GbE to be transported transparently over SONET OC-192c or SDH VC-464c infrastructures. In general, 10GbE multimode fiber connections are expected to transmit 65 or 300 meters or more and 9-micron diameter single-mode fiber connections are expected to transmit 10,000 to 40,000 meters or more. Initial implementations are expected to include

high-speed local backbones in large-capacity installations (campuses, ISPs, etc.). 10 Gbit Ethernet Alliance A nonprofit trade alliance promoting standards-based 10 Gigabit Ethernet technology development, distribution, and utilization. The founding members include 3Com, Cisco Systems, Extreme Networks, Intel, Nortel Networks, Sun Microsystems, and World Wide Packets. http://www.10gea.org/ 100Base-T A baseband signaling networking standard supporting Fast Ethernet with data transfer rates up to 100 Mbps. 100Base-T is intended to provide a faster option to Ethernet networks based originally upon 10Base-T carrier sense multiple access systems. 100Base-T is described in IEEE 802.3u. 100Base-T specifications can be supported over a variety of physical media configurations. Type

Phys. Medium

Notes

100Base-TX data-quality twisted pair Requires at least Cat 5 cable. As in 10Base-T, the data is not split and may be used in full-duplex transmission modes. 100Base-T4 4 pairs of regular twisted pair Requires at least Cat 3 cable. The data stream is divided into three 33-Mbps streams with the 4th twisted pair used for error mechanisms. Half-duplex transmission. 100Base-FX dual-stranded fiber optics Segments may be up to 412 meters.

100BaseVG-AnyLAN A commercial LAN from Hewlett-Packard that was later refined and standardized by the IEEE 802.12 committee and ratified in 1995 as 802.2. Like 100Base-T (Fast Ethernet), it provides data rates of 100 Mbps. It is similar to Fast Ethernet, and capable of carrying Ethernet and Token-Ring transmissions simultaneously. A VG network consists of nodes connected to hub ports in a star topology. Hubs are interconnected through a tree topology. This technology has not found the same widespread commercial acceptance as 100Base-T. See High Speed Token-Ring. 1000Base-T An IEEE standard approved in 1997, developed by the P802.3ab study group. This standard defines a full duplex Gigabit Ethernet signaling system for category 5 (Cat 5) network systems. Unlike 100Base-TX transceivers, which use only two pairs of wires, one in each direction, 1000BaseT transmits on all four pairs simultaneously from both directions of each pair. This creates a more complex system and a greater potential for crosstalk. See far end crosstalk, near end crosstalk. 802.3z A Gigabit Ethernet technology.

4004 An early 4-bit central processing unit (CPU) from Intel as part of the MCS-4 chipset released in 1969. See Intel, MCS-4. 68000, MC68000 A 32-bit central processing unit commonly used in Amiga, Macintosh, and other computers, the first in a series by Motorola. See Motorola. 8008 A historic 8-bit central processing unit (CPU) from Intel, released as a successor to the 4004 as part of the MCS-8 chipset in 1972. The historic Altair computer was based on this processor. See Altair, Intel. 8080 An 8-bit central processing unit (CPU) released by Intel in 1974. RAM addressing was limited to 64 kilobytes. It was incorporated into a number of early microcomputers including the first model released by International Business Machines (IBM) in 1980. 8086 A successor to the 8080, the 8086 was an Intel 16-bit central processing unit (CPU). It could address 1 Mbyte of RAM. This chip was quickly incorporated into new versions of the IBM computers and was also used by manufacturers licensing IBM technology in competition with IBM. See Intel and Motorola for charts of other numbered microprocessors. Microprocessors 1 A processor used in AT&T electronic switching systems, developed by Western Electric in the 1960s. See 1A. 1A A processor used in AT&T electronic switching systems (ESSs), developed by Western Electric in the 1970s. In ESS1A (a.k.a. No.1AESS), a commonly used electronic switching system, the 1A processor, provides maintenance and administrative support and interfaces with the central control. For readouts of operating and maintenance data, the 1A also can be interfaced with operator terminals for receiving instructions and outputting status information. Control panels may be further used for 1A input/output. The No.4ESS digital toll switch also uses this processor. 1BL abbrev. 1. single bottom line. 2. one business line. 1EAX A GTE variant of Western Electric/AT&T’s ESS1A telephone switching system. See 1A, Electronic Switching System 1. See also listings under Intel and Motorola. General 214 License A Section 214 license is issued by the Federal Communications Commission (FCC) to qualifying applicants pursuant to the Communications Act. It charges the FCC with the responsibility of determining whether applicants have demonstrated that their proposal will serve the public interest and need. Thus, activities such as corporate expansions and mergers require prior Section 214 FCC approval. In the mid-1990s, the FCC streamlined the applications process such that it is automatically granted if no one objects during a period set aside for public comment.

2D Two-dimensional. Existing or described in two spatial dimensions or in terms of two selected realms of data. A Cartesian coordinate system is a graphical representation of data in two dimensions. The dimensions need not be spatial, they may be quantities, time, or other types of information that may be plotted. Two-dimensional systems representing spatial concepts commonly tend to be flat in the sense that they represent width and breadth but not depth. In call accounting, 2D representations may illustrate profits over time or calls over time. In network systems logs, connections over time or downtime over time are commonly represented as 2D graphs. 3D Three-dimensional. Existing or described in three spatial dimensions or in terms of three selected realms of data or time. A Cartesian coordinate system can graphically represent three dimensions but often does so in two-dimensional spatial conventions that use an illusion of ‘stretching into space’ in the Z (third) dimension. A photograph is a representation of spatial relationships in two dimensions whereas a sculpture is a representation of spatial relationships in three dimensions. In graphical representations and statistical reports, time is often one of three dimensions represented. For example, an accounting log may track new versus established employees’ sales over a period of three months. Thus, employee status is treated as one dimension, the number of sales as the second, and time as the third. In telecommunications, one of the most significant developments is in the representation of three-dimensional space through graphical rendering or raytraciing or through NCR-type controller systems that can translate three-dimensional data into physical structures. This opens up a whole new world of communications. It becomes feasible, given enough speed and resources, to model a sculpture remotely. One artist may supply the coordinates (or a model) in one location and another may ‘render’ the sculpture with, for example, a milling machine, in another location, perhaps thousands of miles away. Thus, a metalworking shop in the U.S. could conceivably craft a new tool in a remotely controlled milling machine in a rural region in Africa. A physician in Canada could remotely carry out a liver operation on a patient in Germany. An engineer could remotely control a repair robot on a space station or space probe, without leaving Earth. Once the 3D world can be represented by data that can be instantly transmitted over great distances, a whole new world of telecommunications applications becomes possible. 3G Wireless Third generation wireless systems for telecommunications services through radio technologies as described by global telecommunications trade associations and standards bodies, and the Federal Communications Commission (FCC). This category encompasses a wide variety of mobile systems that may be linked into terrestrial or satellite-based communications relays and implies a general overall compatibility with existing and emerging systems. For FCC administrative purposes these systems are considered to be capable of supporting high bit-rate circuit and packet data transmissions with GPS and

roaming capabilities with a reasonable degree of interoperability and standardization. In an October 2000 U.S. Presidential Memorandum the Secretary of Commerce was directed to work with the FCC to develop a plan for the administration of radio spectrum frequencies for third generation wireless systems so that spectrum frequencies could be allocated in 2001 with licenses auctioned by 2002. The 2500- to 2690- and 1755- to 2690-MHz frequency bands were pinpointed for feasibility studies. Regulations arising from these studies can impact existing services (cell phones, PCS, etc.) if reallocation of bandwidth is recommended. Final reports of discussions between the FCC and the NTIA came online in spring 2001. http://www.fcc.gov/3G/ Telegraph and Radio 1 A short telegraphic shortcut numeric code to express “Wait a moment,” “Give me a second,” or “Hold on.” See 73 for the background to numeric codes. “10-4” radio signal codes Numeric codes used by police departments to describe a situation in shorthand. For example, 11 might mean a burglary, while 34 could signal a suicide. These codes are regional and specific to their industries. In California, for example, a 10-4 patrol code indicates message received, while 10-15 signals a prisoner in custody, and 10-33 is an alarm or indication of an officer needing help. Radio codes are also used by the rail industry for cross-country trains and subway trains. For example, in the New York City Transit system radio code signal system, 12-6 signals a derailment and 12-12 indicates disorderly passengers. Codes are usually used for brevity and consistency, but may also be used to provide a small amount of security. See “Code 3” radio communications codes. 13 A shortcut telegraphic numeric code for “I don’t understand.” See 73. 30 A short telegraphic shortcut numeric code to express the end of a communication, thus “Done,” “Finished.” See 73. 73 A number in a telegraph numeric ‘shortcut’ code dating back to at least the mid-1800s. The number 73 was an abbreviated means of representing various sentimental, amorous, and fraternal greetings, depending upon the time, place, and operator. It was similar to the greeting at the end of a letter written by someone familiar with or fond of the addressee. There is a reference in an 1857 issue of the National Telegraphic Review and Operator’s Guide that lists “73” as a numeric shortkey code. Apparently, a committee was established at a convention in 1859 to assign meanings to the numbers from 1 to 92, so this may have been the original impetus for more broad use of standardized numeric codes. Some have attributed the origin of 73 and other numeric shortcuts to Phillips shortcode, but Walter Polk Phillips didn’t publish his code until 1879 and the Phillips code emphasized alphabetic rather than numeric relationships. Thus, while his contribution was substantial and influential, especially in the news

industry, Phillips didn’t create an entirely new code; his contribution was to expand, consolidate, and revise existing code practices. So, it appears 73 was likely in use before the Phillips code was developed. Whatever their origin, certain of the numeric shortcodes became widely used and still retain their original meanings, while many have fallen into disuse and some have mutated in meaning. The railroad still uses some of the code numbers for train-related orders. See Q signal, Z code. 73 key A somewhat unique-looking, historic, palmsized telegraph key intended to be portable and thus covered with a squarish metal housing with the user parts protruding from two sides. The number 73 was printed on the top of the covers, probably a tonguein-cheek reference to the number 73 shortcode used in telegraphy to convey greetings or intimate best wishes. The key was distributed and labeled by the Ultimate Transmitter Company, Los Angeles. 73 Magazine A magazine of interest to telegraphers and amateur radio operators originated by Wayne Green and associates in 1960. Topics ranged from hobby projects, to in-depth looks at telegraph keys, to amateur radio enthusiasms, to the history of submarine cable communications, and there were even some parody issues. Probably not coincidentally,

early issues sold for 37 cents each. In the mid-1970s, controversy over the content of the magazine provoked Pacific Telephone & Telegraph Co. to file suit against 73, Inc., due to their concerns that the information provided might make it easy for readers to find ways to avoid phone charges. Given that this was right around the time that ‘blue boxing’ was beginning to spread, the concerns may have been based on actual phone service thefts. Wayne Green went on to found other magazines, notably 80 Microcomputing, which attracted much of the same audience that had been interested in amateur radio and telegraphy prior to the development of personal computers. “Code 3” radio communication codes A system of numeric codes used by police departments as a shorthand for describing a situation to dispatchers and other officers within radio contact. For example, Code 3 might indicate emergency lights and sirens. In Dallas, Code 5 is shorthand for officer en route to a scene while in California, it signifies a stakeout. In the Dallas Police Department, Code 10X is shorthand for a stolen vehicle. These are usually prefaced with the word “Code” to distinguish them from similar numeric radio signal codes. See “10-4” radio signal codes.