Fiber Optics Illustrated Dictionary - Part 19 doc

Fiber Optics Illustrated Dictionary and 802.3 networks. As ATM is not tied to a particular physical layer, CIF has been defined as a pseudo- physical layer for carrying ATM traffic. CIF provides a frame-oriented means of using ATM layer protocols transparently over avariety ofexist- ing local area network (LAN) framing protocols. The Cells in Frames project has been funded in part by the National Science Foundation (NSF). More information is available through Comel1 University. See cel1s in flight. http://cif.comell.eduJ Cells in Frames Alliance An open membership organization that promotes the affordable deployment of ATM technologies and better use of existing local area network (LAN) infrastructures, while providing applications developers direct control over quality of service (QoS) networking issues. Cellular Array Processor CAP. Aparallel processing architecture, pioneered by Fujitsu, that has applications in a number of areas, including image processing, neural networks, cellular automata simula- tions, and high-speed, multi-user database searches. In the early 1980s, Mitsubishi Electric initiated a satellite 2D image processing system based upon CAP. CAP has been used on the Earth Resources Satel1ite Data Information System (ERSDIS) to process syn- thetic-aperture radar (SAR) data as well as on Japan Earth Resources Satel1ite-l (JERS-l) images. Hughes Electronics has developed systolic CAP for large- scale parallel processing applications. The technology has come to be known more generically as array processing (AP) and Fujitsu's line of equipment has been using the AP- prefix since the mid-1980s. CellularArray Processor Program CAP Program. Aproject to develop a multi-computer peer network system to enable hundreds of users to simultaneously access a huge business register archived by the Aus- tralian Bureau ofStatistics (ABS). Fujitsu Laborato- ries, pioneers of CAP technology, contributed a 12-node AP 3000 paral1el computer to the project. Cellular Data Link Control CDLe. An open data communications protocol suitable for wireless communications. In cellular phone systems, it provides a means to interconnect a data terminal and a cellular phone. The protocol includes various error detecting, correcting, and data interleaving features that make it suitable for wireless transmissions. CellularDigitalPacketData CDPD. An open standard original1y developed and released by vendors in 1993, which was further defined by the CDPD Fo- rum. Then it was passed on for maintenance and en- hancement to the TIA in 1996. CDPD is suitable for packet data services for mobile communications, con- ceived as an extension to landline services for mobile users. The originators of CDPD wanted to develop a way to use existing cellular networks for wireless data, in other words, to overlay newer services on the existing infrastructure. CDPD is a packet-based system, defined to operate over AMPS analog voice systems. Transmission speeds of 19.2 Kbps are possible over the traditional infrastructure. Internet Protocol (IP) is typically used with TCP. Packets are routed into and out of the 172 CDPD network through an Intermediate System (IS), that acts as a relay. Specific routing functions and monitoring of mobility are handled by the Mobile Data Intermediate System (MD-IS). The MD-IS keeps track oflocations through a Home Domain Di- rectory (HDD) database. CDPD is not intended to specifY the various types of service that can be carried over the system but rather describes the architectural structure of the service and its integration with the existing infrastructure. Spe- cific value-added services are up to individual vendors. See A interface, E interface, I interface. Cellular Digital Packet Data Forum CDPDF. An association formed in the early 1990s to develop and promote a standard for cellular digital packet communications. It is now called the Wireless Data Fo- rum. See Cellular Digital Packet Data, Wireless Data Forum. cellular modem A modem integrated with cellular phone technology to provide ease of access to telecommunications services through mobile, wireless transmission. Cel1ular modems are frequently used with laptop computers, often available in the form of PCMCIA cards, which are small, slender peripheral components that fit easily inside a portable device. Dialing and data transfer is controlled by the software. The communication may originate from a wireless system and hook into a landline system. Cellular modems are favored by traveling professionals, such as journalists, sales reps, and scientific researchers who may be relaying information to central facilities on a regular basis. See cellular phone. cellular phone, cell phone An analog, digital, or hybrid mobile communications system, with hard- ware interfaces resembling traditional phone hand- sets, linked through a gridlike network oflow-power wireless transmitters each servicing a geographic area, with a smal1 amount of overlap with adjacent cells. As the user travels through these areas, or cells, the transmission is handed off to provide continuous service, freeing previous channels. Carrying on communications in various cells while on the move is cal1ed roaming. Power levels in each cell are optimized for demand and subscriber density. The cell concept was introduced in the late 1970s to improve upon older single-transmitter mobile systems. The commercial cellular phone system in the U.S. was available by the early 1980s. More recently, digital cellular systems have been devised to increase capacity and call security (through encryption). It is estimated that there are now more than 150 million cellular phone users worldwide, and ambitious programs for launching communications satellites to handle seamless global cellular communications are in progress. See cell, cluster, cellular modem, mobile phone, PCS, AMPS, TDMA. cellular phone security Cellularphone communications are not, for the most part, transmitted in a secure manner. In analog systems, the signal goes over airwaves that can be tapped by a radio scanner operating in the same frequencies. Although encryption is © 2003 by CRC Press LLC starting to be incorporated into digital cellular communications, it is not yet universal. Since cell phones are used for many sensitive business and law enforce- ment communications, security is of some concern to cell phone users. A number of security systems have been developed by cell phone providers, including cell phone attachment peripherals that provide fully digital voice encryption capabilities. cellularpriority access service CPAS. The capability of disaster response personnel to access wireless cellular communications services on apriority basis. This service has been incorporated as part of the u.s. national Cellular Priority Services (CPS) program as a result of experiences in disaster situations in which overloaded cellular networks hindered emergency response personnel communications. Incoming emergency calls can be cued for an available channel to facilitate call connections during times when cellular lines are congested. If voice channels are not available, feature codes can be used to contact the callee. After verification of the call request at a switching center, it can be queued on a priority basis. See Cel- lular Priority Services. Cellular Priority Services (CPS) A U.S. national program to facilitate cellular communications among disaster response personnel such as National Secu- rity and Emergency Preparedness (NS/EP) users. The program was initiated as a result ofcellular congestion during disaster situations that impeded emergency relief personnel from contacting one another. CPS is instrumental in the deployment ofa uniform national program involving many different organizations and levels of government that participate in disaster relief and their associated communications needs. CPS is involved in standards development, administrative processes, regulatory strategies, and competi- tive strategies for implementation ofcellular and related personal communications systems. See cellular priority access service. cellular radio Very similar to cellular phone and, in fact, a forerunner to cellular phone, in which a region is organized into cells, each with a transceiving unit that overlaps with the coverage of adjacent transceiving units. Cellular radio provides for reuse of frequencies and greater capacity than noncellular mobile radio services, and enables users to purchase cheaper equipment, since the power requirements are not as high. See cellular phone. cellular security devices CSD. Add-on peripherals, or all-in-one cell phone sets, that incorporate various security means, primarily digital encryption, or that will transmit random noise to anyone attempting to monitor the communication. See cellular phone security, frequency hopping. Cellular Telecommunications Industry Associa- tion CTIA. http://www.wow-com.com/ celluloid A durable, though flammable, plastic material composed mainly of cellulose nitrate and camphor. Celluloid has been used in many experi- mental technnologies, from the study of diffraction phenomena to the development of cinematic film. In 1885, Hannibal Goodwin developed celluloid film, which became so widely used in the motion picture industry that the films were known for many years as celluloids. In spite of the greater resolution and durability of images captured on film, digital imagery, due to its flexibility and convenience, is super- seding film in consumer markets. See digital video. CELP code-excited linear predictive. An analog-to- digital voice encoding scheme suitable for sending voice conversations through digital networks such as local area networks (LAN s) and the Internet. The technology was developed based upon research on acoustics and voice synthesis by Bell researchers M. Shroeder and J. Hall. CELP is now widely used for digital encoding and speech synthesis. This makes long-distance carriers nervous, as existing phone lines are typically used for portions of the transmission, bypassing long-distance phone charges. See Schroeder, Manfred R. Celsius scale A scale developed in the 1700s to describe temperature with the boiling point ofwater referenced as zero and freezing point as 100 degrees. A year later, the reference points were reversed by Cbristin, and the scale today continues to use zero as the freezing point of water and 100 degrees as the boiling point. Also called centigrade scale. CEN/CENELEC Comite Europeen de Nor- malisation (European Committee for Standardiza- tion)/Comite Europeen de Normalisation Electro- technique (European Committee for Electronic Stan- dardization) CEN is one of three organizations re- sponsible for overseeing voluntary compliance with standards in the European Union, while CENELEC develops technology and standards. CEN cooperates with ISO. See European Telecommunications Stan- dards Institute. http://www.cenorm.be/ Centerfor Democracy & Technology CDT. A par- ticipatory organization promoting democratic values and constitutional liberties in a digital society. The COT seeks practical solutions to protecting and promoting free expression and privacy in global communications technologies through education and con- sensus-building discussion and debate. The COT has expertise in policy, law, and technology and tracks various issues, including information access and bandwidth regulations, cyber-terrorism, Congres- sional activities, digital authentication, and encryption. See American Civil Liberties Union, Electronic Frontier Foundation. http://www.cdt.org/ Center for Research on Information Technology and Organizations CRITO. Amultidisciplinary research unit located at the University of California, Irvine. CRITO conducts theoretical and empirical research on the use, impact, and management of information technology (IT) in organizations. It is also home to the NSF Industry/University Coopera- tive Research Center, known as the CRITO Consor- tium, founded in 1998. http://www.crito.uci.edu/ centigrade scale See Celsius scale. Central One of the many colloquial names given to the early female telephone operators. Others include Hello Girls, Voice with the Smile, and Call Girls. The 173 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary term is now used to describe the central telephone office in a region. See telephone history. Central Computer and Telecommuncations Agency CCTA. A U.K. government agency promoting good practices in infonnation technology and telecommunications in the public sector. Central IT Unit CITU. The Central Information Technology Unit was established in November 1995 in the United Kingdom to advise on government use of information technology. http://www.citu.gov.uk central office CO. 1. Headquarters or main service- or administration-providing center. 2. In telephony, the switching station from which subscriber loops are estab lished. In Europe, the term public exchange re- fers to the switching center. The purpose of the office or central exchange is to provide a connecting point through which a subscriber can establish a connection to any other public subscriber on the circuit or to a trunk line leading to other central offices. The office secondarily provides power requirements, signaling and control devices, and subscriber line services. The lines are further equipped with protective devices, fuses, coils, etc., to guard against unusually high voltages. central office battery The power source that provides direct current to the connected lines for phone conversations. Historically, this power was provided by a 24- or 48-volt talking battery. Later, the 48 volts was transfonned from an alternating current at the central office. See talking battery. central processing unit CPU. A circuit on a single chip that provides the basic, essential logic for per- forming general purpose computing computations and decisions. The most celebrated early computer- on-a-chip was the Intel 8008, released in the early 1970s, which became the basis for a line of early mi- crocomputers and the inspiration for a whole new industry. CPUs may be set up in parallel, or may serve as the central processor for an individual system. Desktop computers are typically based around one CPU, while some workstations, especially those for scientific computations or high-end graphics, have multiple CPUs. Circuitry within a chip can be organized in many different ways. The architecture of the chip affects other aspects of the system, such as memory management, bus addressing, and programming procedures, particularly machine language and assembly programming. The term central processing unit was coined some- where around the late 1960s but did not become prevalent until the late 1970s. During the 1970s, the CPU was often called a main processing unit (MPU). See complex instruction set computing, reduced instruction set computing. central wavelength In optical communications systems, the frequency at which the information-carrying signal is most effective or strongest for a particular physical structure. See cladding diameter. Centralized Automatic Message Accounting CAMA. A billing and statistical system for recording calls on tape. It is sometimes also used to trace fraudulent use of phone services. 174 Centre for Communication Interface Research CCIR. A research center at the University of Edin- burgh, founded in 1991. CCIR studies some interest- ing communications-related topics, including the design and implementation of telephony services, the development of multimedia and virtual reality interfaces, and the simulation of automated services. http://www.ccir.ed.a.c.ukI Centre National d'Etudes des Telecommunication CNET. The French organization that approves telecommunications products for the French market. It is now France Telecom R&D. Centrex (from Central exchange) A commercial telephone service provided by local telephone exchanges in which the subscriber-specific switch is physically located either on the premises of the phone exchange (CO) or at the customer's premises (CU). Used primarily by businesses, as a lower cost alternative to a private branch exchange (PBX), Centrex systems have a number of extra calling features (Caller ill, Call Conferencing, etc.), with a wider selection of options than are available to residential subscribers. An on-premises Centrex system is similar to a PBX system in that it is located on the customer's premises, but a PBX is owned by the customer, whereas the Centrex system is leased from the phone company. Each choice has pros and cons in terms of upgrades and maintenance. A Centrex central office system can also be combined with a PBX system, but care should be taken not to order redundant options for the service, since many can be provided by either. A Cen- trex system (or PBX) can be combined with Auto- matic Call Distribution (ACD), to provide self-con- tained, sophisticated automated business telephone services, like those used by many mail order re- tailers. Centronics Aprinter manufacturer well known for establishing aparallel data transmission standard for computer printers, especially dot matrix printers that were popular in the 1980s. Centronics paralleldatastandardA data transmission standard established by Centronics and accepted de facto by much of the printing industry in the 1980s, particularly for cabling dot matrix and some daisy wheel printers to parallel ports on desktop computers. The cable is usually a flat or pinned D connector. This parallel standard is generally faster than similar serial cable attachments because data can be carried over eight wires at once rather than just one. At- tachments vary, but most systems employ a pin connector on the computer side and a flat connector on the printer side. See A connector. CEO Chief Executive Officer. lYPically the highest member of the corporate hierarchy, in charge of over- all business direction, goals, and strategies. CEPT See Conference Europeenne des Administra- tions des Postes et des Telecommunications. CEPTl, CEPT2, CEPT3 See El, E2, E3. CER See cell error ratio. CERB Centralized Emergency Reporting Bureau. A Canadian reporting organization to safeguard the public. © 2003 by CRC Press LLC Cerf, Vinton "Vince" G. (ca. 1930s- ) Vinton Cerf is credited with some of the early ideas for network gateway architecture. He has held various engineering, programming, and teaching positions in businesses and educational institutions. In the early 1970s, he researched networking and developed TCP /IP protocols under a DARPA research grant and, in 1974, co-authored "A Protocol for Packet Network Inter- networking" which describes Transmission Control Protocol (TCP). During this same period, he became a founding chairman of the International Network Working Group (INWG). In 1977, Cerf co-demon- strated a gateway system that could interconnect packet radio with the ARPANET. In 1978, he co-developed a plan to separate TCP's routing functions into a separate protocol called the Internet Protocol (IP). In 1997, he was awarded the National Medal of Technology. See Kahn, Bob. CERFnet See California Education and Research Federation Network. CERN Organisation Europeenne pour la Recherche Nucleaire. The European Organization for Nuclear Research, located in Geneva, Switzerland, founded in 1954. http://www.cern.chl CERT See Computer Emergency Response Team. certificate An authentication entity used in a variety of cryptographically ensured digital transmissions designed to safeguard privacy and authenticity in electronic messaging and transactions, especially con- tracts, payments, private information, etc. Certifica- tion is carried out through a technical evaluation and is administrated by a recognized, assigned certificate authority. While not a complete list of all definitions associated with the issuing and management of certificates, the Authentification Certificates chart provides a short list of some of the main aspects of digital certification. See encryption. CEST Centre for the Exploitation of Science and Technology. U.K. industry-funded organization formed in 1988. CEV controlled environmental vault. See cable vault. CFB See Call Forward Busy. CFCF A historic broadcast station, originating in Montreal, Canada, in November 1920. CFCF was originally radio station XWA, one of the world's frrst radio broadcast entities. Representing "Canada's First, Canada's Finest," CFCF became Quebec's first private television station in 1961 as well as a founding member of the CTV network. See CKAC, XW A. CFDA See Call Forward Don't Answer. CFF See critical fusion frequency. CFGDA Call Forward Group Don't Answer. CFP Channel Frame Processor. CFR Confirmation to Receive. Anotification in networks that a frame can be forwarded. CFUC Call Forwarding UnConditional. CFV See Call for Votes. CFW See Call Forward. CGA 1. Carrier Group Alarm. An out -of- frame alarm signal generated by a channel bank, which may be followed by trunk rerouting and error control. 2. See Color Graphics Adapter. CGI See Common Gateway Interface. CGM Computer Graphics Metafile. A standardized graphics interchange format. CGSA Cellular Geographic Service Area. The physical area within which a cellular company provides services. CGSAs may include multiple counties and may even cross state lines. \.:.: •. :~.:: ~~~~~:t;~~~~~~l~r;s~:;;~~~~::= ". chad The small punched out pieces or edge strips from encoded punch cards, tractor feed paper, or paper tape. Punch card chad were collected in chad boxes which had to be periodically emptied. Origi- nally discarded, some bright marketing person started packaging them as confetti for parties and celebra- tions. The term appears to have originated around 1947 and the plural and singular are the same. Chadwick, James (1891-1974) An English physi- cist who is credited with discovering the neutron in 1932 at Cambridge, England. Chadwick actively en- gaged in radiation experiments, some pf which stemmed from the work of Ernest Rutherford. chaff, window Materials such as metal strips or fine wires that are highly reflective to radar waves. Chaff may be strung or shot into the air for the purpose of scattering or deflecting electromagnetic waves. chaining A common modular software execution technique in which a process is handed off to another program or launches other program modules on an as-needed basis. By having only the necessary components memory-resident, and by off-loading modules that are no longer needed, complex programs can be managed with limited resources. Challenge-Handshake Authentication Protocol CHAP. An Internet standards-track protocol de- scended from a variety of semi-secure network imple- mentations in the mid-1970s and 1980s, which provides a method for key authentication using Point- to-Point Protocol (PPP). It employs a three-way handshake upon link establishment to verify the identity of the peer and may repeat it at intervals. After link establishment, the authenticator challenges the peer, which responds with a hash value. If there is a match, authentication is acknowledged; if not, the connection should be terminated. The key is known only to the peer and the authenticator and is not transmitted. This protocol is suitable for small or medium connections with an established trust relationship. Large tables of keys are not practical, and the information must be available in plaintext form, with a secure central repository to store it. See RFC 1994. challenge-response A means to query and respond in a system where an entity seeks access to a physi- calor network environment or to set of functions or resources. There is more than one way to implement a challenge- response system. It may be incumbent upon the entity seeking resources to challenge the system to which it desires access, or the system with the access may challenge an approaching entity as to its intentions. In most cases it is easier to implement the system such that the approaching entity (which may be a person 175 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary approaching a building or a computer function transmitting to arepository or restricted system or network) sends out a challenge to the repository ofre- sources. In this way, it is not necessary to constantly poll or monitor the access point for approaching entities. Thus, the person orpoint seeking access issues the challenge and the secured system responds with access, access instructions, a request for more information (e.g., apassword), or a denial. When it works the other way, the 'approaching' entity may not be known until it reaches a certain physical boundary such as the range of a motion detector or a gateway or access point in a computer system. In this case, the resource server may challenge the approaching entity and request identification, more infonnation, etc. before issuing the acceptance ordenial of access. Challenge-response mechanisms are central to many types of intruder-detection systems and to digital certificate-based computer security systems. See certification, Challenge Handshake Authentication Protocol. channel 1. In its most general sense, a path along which signals can be transmitted. 2. In radio broadcast, the electromagnetic frequency spectrum extend- ing roughly from VLF to UHF (further above that is the microwave frequency). 3. A portion of the spectrum assigned for the use of a specific carrier, e.g., the FM band is divided into channels of a specified Authentication Certificates- Summary of Basic Aspects Type Description certification authority A screened, trusted, assigned authority tasked with evaluating applications for digital certificates and issuing, managing, and revoking the certificates as appropriate. The authority vouches for the binding between the data items within a certificate and for the association of the certificate to the entity using it. certification authority workstation A computer system designed to support the issuance of digital certificates and related documents and management aspects. certificate revocation The declaration, by a certificate authority (CA), that a previously valid digital certificate issued by that CA is no longer valid effective immediately or as of a specified date. The information may be held in a certificate revocation list (CRL). certificate revocation list An administrative tool used by digital certificate authorities (CA) to track and notify of certificates that have been revoked. The list may be used for public key certificates and! or attribute certificates and may apply to user and authority certificates. A certificate revocation tree is a hierarchical distribution mechanism for sending out information about revoked certificates, signed by the issuer of the tree. certificate serial number An integer value associated with and possibly carried with a digital certificate. The serial number is a unique number assigned by the authorized issuer. certificate status responder In the context of the Federal Public Key Infrastructure (FPKI), a trusted online server acting on behalf of a certificate authority (CA) to provide authenticated certificate status information as requested by certificate users. certificate user An entity such as a person, firm, or algorithm using and trusting the validity of certificate-related information (e.g., a public key value) provided in a digital certificate. certificate validation An act or process by which a certificate user establishes the trust relationship associated with a digital certificate. The process for ensuring the validity ofa digital certificate, which may include verification of the certification path and the currentness ofcertificates in the path. Aspects that should be verified include expiry dates or possible revocation actions, the validity of the syntax and semantics, and the signature itself. 176 © 2003 by CRC Press LLC kilohertz range. 4. In a GPS receiver, the radio frequency, circuitry, and software needed to tune the signal from a satellite. 5. In audio, a sound path (e.g., stereo broadcast requires at least two sound paths). 6. In telephony, voice-grade transmission within specified frequencies and bandwidth. See circuit. 7. In a Frame Relay network, the user access channel across which the data travels. If a physical line is unchannelized, then the entire line is considered a channel. If the line is channelized, the channel is any one ofa number of time slots. If the line is fractional, the channel is a grouping of consecutively or nonconsecutively assigned time slots. channel aggregation Inverse multiplexing. Bonding multiple lines (e.g., phone lines) in such a way that transmission speeds are faster. This technology is sometimes incorporated into modems to speed upload and download times. channel-associated signaling CAS. In association with channel banks, channel-associated signals are derived from analog electromagnetic signals and con- verted to digital signaling bits for transmission over digital lines. In ATM networks, CAS is a form of circuit state signaling, in which the state for that specific circuit is indicated by one or more bits of signaling status, which are repetitively sent. In TIlE1 voice applications, CAS is used for in-band signaling information in the sense that it is carried in the data stream with each channel, rather than as a separate out-of-band transmission. However, it can be configured to use a specific channel (e.g., the D channel in ISDN) such that it is functionally similar to out-of-band signaling and is then considered to be an out-of-band technology. R2 signaling methods are commonly used in channelized voice networks but may be implemented in a number of ways. In general, CAS is set up on a network by entering global configuration settings into a router and specifying the controller to handle the specific signaling scheme. The signaling protocol and CAS are configured for a specified number of time slots (or may default to all channels). The framing characteristics and the line code are defined, and a clock source is specified. See facility-associated signaling, R2 signaling. channel bank A network interface device that provides multiplexing and flow control functions on multiple transmission channels, such as voice and data, which are being brought into a single electrical data stream. A channel bank is not intended to provide switching functions. A channel bank is commonly used as an interface between multiple lines coming out of an analog system, such as a private branch exchange, which are then brought together and multiplexed onto a larger bandwidth digital transmissions medium such as aDS-l stream associated with aTl line. See multiplexing. channel bonding A technique for increasing transmission speed by means of aggregating multiple lines. It is a way of getting a little more performance from existing lines without investing in higher end technologies, such as aTIline. Channel bonding for modem communications is usually cost effective only for two or three lines; above that number, ISDN may be abetter option. channel hopping 1. Changing channels on a radio phone, usually to find one with clearer reception. 2. Changing channels constantly on TV, usually with a remote control, and often during commercials, to the consternation of other viewers who don't have control of the remote. 3. On IRC, switching chat channels and barging in, or listening in, on many conversations in a short period of time. channel separation In broadcasting, the space inter- posed between designated adjacent channels. Since signals may have a tendency to interfere with one another, leaving a gap increases the likelihood of clean signals on either side of the gap. Channel separation is commonly used in radio transmissions, especially FM broadcasts, where the width of the sepa- rator may be greater than the width of the channel through which the FM transmission is passing. Channel Service Unit CSU. A device typically integrated with a Data Service Unit as a CSU/DSU. It is often the frrst device in a digitally networked facility that routes information and may also protect equipment within the facility from electrical interference and damage. It may further regenerate a signal to maintain signal strength and integrity or convert the signal from one format to another. It is commonly used between incoming T1 or E1 lines and internal channel banks, at a central office offering end-to-end digital line services to subscribers, usually through leased lines. See Data Service Unit. channel surfing Flipping through stations on a television looking for something worth watching, or avoiding the commercials. On a TV, it is usually done with a remote, from a comfortable position on the couch. Web surfing on the Internet is similar and may eventually evolve into channel surfing, as more and more companies are starting to broadcast multimedia on their sites. See channel hopping. channelize To increase the capacity of a wide- or broadband transmission medium by subdividing it into smaller channels, often with a small gap between channels to reduce interference. CHAP See Challenge Handshake Authentication Protocol. Chappe,Claude (1763-1805) A French scientist and communications pioneer who collaborated with his brother Ignace. Chappe advanced communications in 1792 by adapting semaphores (visually encoded messages) to apair ofanns mounted on a system of towers. In 1793, this enabled a message to be transmitted 15 kilometers and ayear later a message was sent from Paris to Rhine (a distance of about 150 miles) in only a few minutes, through coded positions representing characters and symbols. There were disadvantages to this system, including visibility, the need for many towers, and the 24-hour monitoring that was necessary for adjusting the arms when a new message came through. Nonetheless, it was an improvement over previous systems and grew in France to over 500 signaling stations. The first 177 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary formal telegram me is said to have been sent on 15 Au- gust 1794. Chapuis, Robert J. (1919-)A French researcher and author who has enriched our understanding of telephone history. Chapuis has brought to light the in- ventions ofindividuals who might otherwise remain uncredited because they were not directly associated with the larger, more successful phone service companies. See Lorimer telephone. character code The specific coding system, or protocol, used to fonnulate characters for transmission. Examples of character codes include Baudot code, Morse code, ASCII, UNICODE, and EBCDIC. characterset I. All the symbolic character representations (letters, numbers, punctuation, diacritical marks, etc.) available to a system, such as a computer, printer, or typewriter. Character sets vary widely from device to device and culture to culture, and interpre- tation between different character representations is one of the big challenges in global computing. 2. In network programming, character set is associated with mapping tables that are used to convert octets to characters, related to character encoding. These are often identified by tokens. See ASCII, RFC 1345, RFC 1521. characters per second In a telegraph key transmission in Morse code, the number of characters a hu- man operator can send or read in a second. In a printer, the number ofcharacters that are printed in a second. In a data transmission, the number ofcharacters that are sent through a telephone line, through a modem, or through a network. These are sometimes expressed instead in tenns of bits per second, since a character may take one byte in some systems and two bytes in others. charge coupled device CCD. Asensing system that uses lines or arrays oflight-sensitive photo diode elements. As light comes in contact with various CCDs, the intensity of the light is registered and translated into digital infonnation. Resolution is related to the type, placement, and quantity of these elements. CCDs are used in many photographic and scanning devices, digital cameras, camcorders, computer scan- ners, robot· vision systems, etc. Charles Babbage Institute CBl. Aleading archive and research center in the study of the history of infonnation processing and its influence on society. The CBI, founded in 1979, operates out of the University of Minnesota. It is named after Charles Babbage, a pioneer researcher and inventor of early "thinking machines." The Institute preserves historical documents and sup- ports and promotes research in infonnation processing history. Documents include oral histories, manu- scripts, professional records, periodicals, obsolete manuals, photographs, and other reference materials. Collections of special interest include the Academic Computing Collection, the Amateur Computer Soci- ety Records, ACM publications, the Charles Babbage Collection, the James W. Birkenstock Collection of International Business Machines Corporation Records and British Tabulating Machine Company 178 Histories, EDUCOM records, Wallace J. Eckert Pa- pers, the National Bureau of Standards Computer Literature Collection, Sperry Rand Corporation records, and many more. The archives are open to the public for use on the premises. Photocopies may be delivered by mail or fax. Support is provided by the University Libraries, the Charles Babbage Foundation, and the Institute of Technology. CBI publishes the eBI Newsletter and awards the Adelle and Erwin Tomash Fellowship in the History ofInfonnation Processing. http://www.cbi .umn.edu/ chase trigger In digital recording techniques, there are some legacy analog time code technologies that cause problems when applied to a digital environment. Digital audio, for example, is recorded accord- ing to a system clock. If the frequencies vary, there may be audio artifacts that cause unwanted noise in the recording. A chase trigger is a means ofsynchro- nizing time code by starting the sound segment when a particular time trigger occurs. Once it is triggered, it follows its own clock speed irrespective ofwhether the underlying recording that initiated the trigger has remained steady. If the underlying signal is stable, it's not a problem, but in some recording environments stability is hard to guarantee. See house sync, reference clock, time code. chat In online computer telecommunications, private or public message areas in which participants type messages to one another in a somewhat real-time manner. Internet Relay Chat (IRC) is the largest chat forum on the Intemet, although some of the large service providers have their own subscriber chat channels. Chat lines can be set up to be keyword protected, to offer private or group conference conversations. Chats with celebrities are sometimes moderated to keep the conversation to a level in which the comments are not too rapid or overwhelming. Anyone can open a public chat channel on IRe. To create a new chat or join a current chat, you enter the IRC server and type #join mychatchannel (e.g., #join gardening) or select join from the menu, if using a menu-based IRC software client. It is not acceptable on IRC to make off-topic comments or to denigrate other participants or their viewpoints. See Internet Relay Chat, Netiquette, Netizen. chatter I. In circuits, a repetitive, undesirable, fast clicking or opening and closing of a circuit. Power fluctuations can sometimes cause chatter. Unchecked, it can lead to damage ofequipment and interference with communications. 2. In servos, styluses, and other moving control mechanisms, quick, short os- cillations in a direction other than the desired direction (often perpendicular to the desired direction) caused by friction, power fluctuations, improper cali- bration, or improper mounting (too loose or too tight). cheapernetjargon Cheaper, maybe-not-as-fast, affordable networks, such as Ethernet running over thin coaxial cable. check bit A bit, or a group of bits, used for avariety oferror housekeeping functions. A single bit is often used for parity checking, whereas 7 or 16 check bits © 2003 by CRC Press LLC may be used for various cache functions. See checksum, parity. checksumA computed value commonly used for as- sessing data integrity and detecting errors or anoma- lies. Checksums are used in file systems, encryption systems, and packet transmission protocols. In networks, checksums help determine, with a reasonable degree of confidence, whether a packet has arrived at its destination unchanged. See check bit. cherry picker colloq. An industrial crane equipped with a one- or two-person bucket to raise workers to levels that cannot easily be reached by other means. These are used to access fruit trees, windows, utility poles, and other high places. See lineman. Cheny Picker - Utility Pole Maintenance An aerial bucket, popularly calleda "cherrypicker" faCilitates the flexible and safe maintenance of pri- mary power lines, transformers, secondary power lines, telephone, wires, andfiber optic data cables (in that order from top to bottom) that are typically strung on joint utility poles. See jointpole. cherrypicking colloq. Selecting only the calls most likely to bear fruit and assigning them appropriately. In other words, when a call comes in, over a phone or a modem, those callers who are in some way identified or prescreened to be the most likely to benefit the callee, usually by purchasing products or services or by investing in the company, are given priority. Cheny picking is also applied to reader service inquiries. When magazine readers send in reader service cards, these inquiries are forwarded to the appropriate vendors. The vendor sheets sometimes include statistics gathered by the magazine, such as job titles and the number of boxes the inquirer checked. Thus, the vendor can select and respond first to those most likely to produce revenue for the company. Children's InternetProtectionAct CIP A, ChIP Act. Introduced to the U.S. Congress by Senator John McCain in January 1999, the Act was never called to vote. However, it was later brought forward through an omnibus budget bill that was signed into law in December 2000 to come into effect in Spring 2001 as part of the Consolidated Appropriations Act. Also referred to as the Children's Online Protection Act, it requires that certain federally funded institutions have in place an Internet Safety Policy for protecting children from exposure to Internet content that may be inappropriate for children. The ChIP Act en- compasses monitoring and filtering of objectionable content as well as monitoring of children while online. No sooner was the legislation introduced than it was challenged by civil liberties organizations as to its constitutionality. chimeA tone on a telephone, computer, or alarm system that sounds like a pleasant musical ~one rather than a buzz or a beep. It's straightforward to gener- ate many types of sounds and chimes on a computer system through sampling and storing sound files. chimney effect The natural tendency of heat to rise. One type ofcooling system that is based upon this effect consists ofventilation slots or holes in the top and bottom surfaces ofa cabinet or component, fa- cilitating natural air circulation. China United Telecommunications Corporation China UNICOM. A state-owned corporation cospon- sored by the Ministries of Electronic Industry, of Electric Power, and of Railways, founded in accor- dance with the "Company Law of the People's Re- public ofChina." China UNICOM seeks to promote the reform of the telecommunication system and its potential resources, and to build a telecommunications network for furthering the industry of China. Telecom operations are under the control of the Min- istry of Posts and Telecommunications. The corporation has international relationships with organizations such as GTE (U.S.), Nortel (Canada), and Singa- pore Telecom. chip 1. In computers, most commonly a chip is a component integrated circuit attached to the circuitry by conducting legs that can be inserted into a PC board or onto another chip. The term is more commonly applied to the removable rather than the soldered components. Chips come in many shapes and sizes, but most of those used in consumer appliances and desktop computers range up to about 2 or 3 in. in length. Some- times two or more chips are closely coupled or lami- nated together. Larger, heat-producing chips may be coupled with a fan or require that a fan or heat sink be installed nearby with adequate air circulation. Chips can be general purpose, as with central processing units (CPUs), or very specialized, as with device driving chips optimized for a particular device. See semiconductor, silicon, large scale integration. 2. The transmission duration for a bit or single symbol ofa PN (pseudorandom noise) code. 3. In spread spectrum wireless communications, a chip is a redundant 179 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary data bit inserted at the origin of a transmission, which subsequently is removed when the transmission is deciphered at the receiving end. Chip Protection Act CPA. Accepted into law in 1984, this act provided new intellectual property protection for the semiconductor industry which was ex- periencing tremendous growth at this time. Chireix antenna, Chireix-Mesny antenna Abidi- rectionally resonant, cascading array, wire, or tubing antenna consisting of series-fed square loops with sides the length of a half-wave or quarter-wave. It is used for very high frequency ranges, typically VHF and higher. chirp A short birdlike, often high-pitched, tone that may occur in various audio components if not configured correctly. It is usually an undesired quality requiring adjustments. In laser light components, pulsing between different power levels or an instability causing variation around a central, desired wavelength can cause an optical chirp and accompanying chromatic dispersion. One of the skills learned by technicians is measuring laser chirp in modulated transmissions. Laser chirp is usually undesired, but may have some advantages. It has been reported that positively and negatively chirped laser pulses may differ in their electron yields. Whenever there is an imbalance in phenomena generated by similar actions, the potential for generating logic signals exists, if ways can be found to harness the effects. It also means that one type of chirp may be useful for different functions ( or may be more disruptive) than another. chopper A device for quickly opening and closing an electrical circuit or beam oflight at regular intervals. Achopper may interrupt a signal to permit am- plification, to demodulate a circuit, to interrupt a continuous stream ofparticles, or to send signals. The process is called chopping. See optical chopper. Christie, Samuel Hunter (1784-1865) An English mathematician and educator who investigated the electrical properties of various metals and created a balanced bridge resistance-measuring circuit in 1833, which was used and described by Charles Wheatstone and became known as the Wheatstone bridge. chromaAcolor as characterized by its hue and saturation, without reference to the relative brightness of the color. Black, white, and shades of gray are not considered to be chroma. chroma key In cinematography, a technique for eliminating a specific region or background so that new imagery can be superimposed in the removed area. Everyone who has watched television shows, especially action shows, has seen chroma key effects. High speed chases on motorcycles and cars are often photographed from the front with the bike or car mounted on a frame that sways back and forth before a blue or green curtain (the chroma key). In other words, the moving scenery is simulated This way the actors can be safely filmed, and their conversations recorded without extraneous noise. Chooser Utility for Viewing and Selecting Computer Network Resources ···· :.11. Select a file server: Tina's Com puter Brad's Computer Engineering Dept. Bra nch Office - - 7.6.2 e Active Q Inactive AppleTalk If ;-~ t!J Color S'tl 2500 & Lu.r\\'rit.r e ~ se 152O(A1) HDAK5 UKI ~ Apple SCin i) PSPrint,r ~ lrM9tWrit~r &.~~~: r::1 AppltTalk. ttr 7.0.1 Each computer system on anetwork has some type of software utility similar to the above Chooser on the Macintosh that displays network resources and aIIows the user to choose those of interest. The icons on the left represent available network device drivers, including PostScript printing devices, scanner drivers, digital camera connections, etc. If AppleShare is selected, the system searches the network looking for other available systems and displays them in a list on the right. The user must then select asystem andlog on to that system with a valid passwonJ. Once logged onto the remote system, the user may select from a list of available mounted servers (usually hard drives) associated with that system that have file sharing attributes set to lion. " The user can then send and receive data between systems. 180 © 2003 by CRC Press LLC Later, in the editing room, the foreground is superimposed on a background of a road, desert, or for- eign planet, and everything that was blue or green becomes the background. Chroma key effects are often cheesy looking, with a halo around the actors giv- ing away the illusion, but with digital photography, it is becoming increasingly difficult to distinguish what is real and what isn't. chrominance The color-carrying portion ofa video signal, which for various reasons related to compat- ibility with black and white television sets, is carried separately from luminance. The chrominance com- prises hue (color) and saturation (the intensity of the color). chronograph 1. An instrument that graphically displays the time. 2. A diagrammatic representation of time intervals where some quantity or variable is expressed as a function of time. chronoscope An instrument for measuring time in very precise increments that is used in scientific applications. ChooserA software utility for selecting network resources as part of the Macintosh as. See diagram. CHU A specialized AM band radio station that broadcasts the time with brief tones each second, and the spoken time each minute in English and French. The time broadcast is Eastern Standard Time (EST), which is five hours after Coordinated Universal Time (UTC). chuck A device to support and sometimes turn another, usually through pressure and friction. A lathe chuck is a hollow or geared area in which the metal or wood to be turned is held in place by a chuck. A drill chuck is a geared key mechanism for inserting or removing a drill bit held in place by pressure as the drill key tightens the aperture against the shaft of the bit. A fiber optic splicing device may be equipped with V-grooves or chucks to hold the two pieces of fiber optic filament to be spliced. If it has chucks, they are typically either clamping chucks or vacuum chucks. With vacuum chucks, individual vacuum control to the chucks makes it possible to firmly secure one filament while aligning or rotating the other until the desired position is found. The chucks may also be cleared of particles with vacuum suction. churnA term to describe customer subscription turn- over in the cellular telephone and cable TV industries. Chum is of concern because the setup fees are often spread out over future monthly revenues and are not recouped unless the customer retains the service for some time. Chum is usually computed as some per- centage formula based upon connects and discon- nects. Cll. See congestion indicator. 2. Certified Integrator. CIAC See Computer Incident Advisory Capability. CIAJ Communications Industry Association of Ja- pan. An organization committed to promoting the development of manufacturing of telecommunications equipment and related business activities. CIC See Carrier Identification Code. CIDR See Classless Inter-Domain Routing. CIE The Commission Internationale de L'Eclairage (Internal Commission of Illumination) established in 1931, developed an international color model for light, with the aid of technology that enabled more precise measurement of wavelengths, especially those within the visible light spectrum. Maxwell's triangle was taken for the basic model and three pri- mary colors selected and assigned to the system. The CIE chromaticity model is two dimensional but can be extended to three dimensions by reducing the value or amount of light, thus diminishing the brightness until it reaches black, the absence of light. See Maxwell's triangle. CIF 1. See cells in flight. 2. See Cells in Frames. 3. See Common Intermediate Format. 4. cost, insur- ance, freight. CIID See Card Issuer Identifier Code. CIIG Canadian ISDN Interest Group. CIK See cryptographic ignition key. cinchingAn increase in pressure in which something is made tighter, becomes more difficult to undo, or becomes locked up. This effect is sometimes undesirable as on reel-to-reel systems, where the pull on a reel is greater than the speed at which it unwinds so the remaining tape, or other material, tugs and becomes very tightly packed. It can also happen on cable spooling or installation rollers and should be avoided as it might damage the cable components. CIP 1. Carrier Identification Parameter. In ATM networks, CIP is a 3- or 4-digit carrier ill carried in the initial address message, used in establishing a connection. 2. Channel Interface Processor. A Cisco Sys- tems channel attachment interface for their 7000 series routers which connects a host mainframe to a control unit. CIPA See Children's Internet Protection Act. CIPF See Canadian Information Processing Society. cm 1. See carrier to interference ratio. 2. See committed information rate. circuitA physical or virtual collection of pathways, channels, or conductors interlinking given points or nodes in an orderly fashion to create communications or electrical links. Computer circuits include traces, wires, chips, resistors, capacitors, etc. A circuit can be open or closed. circuit line The physical line carrying network traffic between user equipment and an IPX or IGX node. Most network services (voice, data, ATM, etc.) require that the circuit line be configured and 'activated' on the system to which it is attached before they can be used. circuitline commands Commands typically used to set up and control a communications line for data, voice, and Frame Relay. Various operating states and parameters are established first to set up the general parameters for the line (as opposed to specific parameters for the voice or other communications service). The command set differs from manufacturer to manufacturer, but it commonly includes commands to ac- tivate the circuit line, down the circuit line, display or print the current configuration, and configure the parameters of the line. 181 ' • :::.:.f • :.:».:.:.~ •.:. }~:J ;;~ !'~~~ . © 2003 by CRC Press LLC . software execution technique in which a process is handed off to another program or launches other program modules on an as-needed basis. By having only the necessary components memory-resident, and by off-loading modules that are no longer needed, complex programs can be managed with limited resources. Challenge-Handshake Authentication Protocol CHAP. An Internet standards-track protocol de- scended from a variety of semi-secure network imple- mentations in the mid -1 97 0s and 198 0s, which provides a method for key authentication using Point- to-Point Protocol (PPP). It employs a three-way handshake upon link establishment to verify the identity of the peer and may repeat it at intervals. After link establishment, the authenticator challenges the peer, which responds with a hash value. If there is a match, authentication is acknowledged; if not, the connection should be terminated. The key is known only to the peer and the authenticator and is not transmitted. This protocol is suitable for small or medium connections with an established trust relationship. Large tables of keys are not practical, and the information must be available in plaintext form, with a secure central repository to store it. See RFC 199 4. challenge-response. stations. The first 177 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary formal telegram me is said to have been sent on 15 Au- gust 1794. Chapuis, Robert J. (191 9-) A French researcher and author who has enriched our understanding. Fiber Optics Illustrated Dictionary and 802.3 networks. As ATM is not tied to a particular physical layer, CIF has been defined as a pseudo- physical layer for carrying ATM traffic. CIF provides

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