Cellular On Light Truck-Clickstreams

Cellular On Light Truck


Cellular Phone Service


Cellular Protocols

Conventions and procedures which relate to the format and timing of device communications. In data transmission communications, there are currently three major protocols, which are converging into a de facto standard: MNP, SPCL, and PEP.

Cellular Radio

A mobile radio system. In the old days, there was one central antenna and everything homed in on that and emanated from it. With cellular radio, a city is broken up into " cells ," each maybe no more than several city blocks. Every cell is handled by one transceiver (receiver/transmitter). As a cellular mobile radio moves from one cell to another, it is "handed" off to the next cell by a master computer, which determines from which signal the strength is strongest. Cellular mobile radio has several advantages:

  1. You can handle many simultaneous conversations on the same frequencies. One frequency is used in one cell and then re-used in another cell. You can't do this on a normal mobile radio system.

  2. Because one cellular system can accommodate many more subscribers than a normal mobile radio system, and therefore because it can achieve certain economies of scale, it has the potential of achieving much lower transmission costs.

  3. Because the transceiver is always closer to the user than in a normal mobile system, and the user 's radio device thus needs less power, the device can be cheaper and smaller. Cellular radios started at over $5,000 and are now well under $500. From the first portable units, weight has already dropped to under one pound . There are several units that will fit in your breast pocket and not overly stretch your suit.

The following are specific cellular radio terms, or general telecom terms that mean something special in cellular radio:

  • A/B Switch Permits user to select either the wireline (B system) or the nonwireline (A system) carrier when roaming.

  • Alphanumeric memory Capability to store names with phone numbers .

  • Call-in-absence horn alert User-activated feature that sounds car horn upon receiving a call.

  • Call-in-absence indicator Feature that displays what calls came in while user was absent.

  • Call-in-progress override Insures that power to the phone is not lost if the car's ignition is turned off.

  • Call restriction Security feature that limits phone's use without completely locking it. Variations might include dial from memory only, dial last number only, seven- digit dial only, no memory access, etc.

  • Call timer Displays information on call duration and quantity. Variations might include present call, last call, total number of calls, or total accumulated time since last reset. Call-timer beep serves as a reminder to help keep calls brief. It might be set to go off once a minute, ten seconds before the minute, for example.

  • Continuous DTMF (touch-tones) Sends DTMF (dual-tone, multi-frequency) tones ” also called touchtones ” allowing access to voice mail and answering machines that require long-duration tones. "Continuous" means you get the tone so long as your finger is on the button. This may seem obvious to you and me, except that some "modern" phones just give a short tone no matter how long you keep your finger on the touchtone button.

  • Dual NAM Allows user to have two phone numbers with separate carriers (see multi-NAM).

  • Electronic lock Provides security by completely locking phone so it can't be used by unauthorized persons.

  • Hands-free operation Allows user to receive calls and converse while leaving hand- set in cradle (similar to office speakerphone).

  • Hands-free answering Phone automatically answers incoming call after a fixed number of rings and goes to hands-free operation.

  • Memory linkage Allows programming specific memory locations to dial a sequence of other memory locations.

  • Multi-NAM A cellular telephone term to allow a phone to have more than two phone numbers, each of which can be on a different cellular system if desired. This lets the user register with both carriers in home city, expanding available geographic coverage.

  • Mute Silences the telephone's microphone to allow private conversations without discontinuing the phone call. Audio mute turns off the car stereo automatically when the phone is in use, and turns it back on when the call is completed.

  • NAM Numerical Assignment Module. Basically, your cellular phone number, although it refers specifically to the component or module in the phone where the number is stored.

  • On-hook dialing Allows dialing with the handset in the cradle.

  • Roaming Using any cellular system outside your home system. Roaming often incurs extra charges.

  • Scratch pad Allows storage of phone numbers in temporary memory during a call. Silent scratch pads allows number entry into scratch pad without making beep tones.

  • Signal strength indicator Displays strength of cellular signal to let user know if a call is likely to be dropped.

  • Speed dialing Dialing phone number from memory by pressing a single button.

  • Standby time Maximum time cellular phone operating on battery power can be left on to receive incoming calls.

  • Talk time Maximum time cellular phone operating on battery power can transmit.

  • Voice-activated dialing Your cellular phone recognizes your words and dials accordingly . You say "Dial Mom" and it dials mom.

Cellular Radio Switching Office

The electronic switching office which switches calls between cellular (mobile) phones and wireline (i.e. normal wired) phones. The switch controls the " handoff " between cells and monitors usage. Different manufacturers call their equipment different things, as usual.

Cellular Switching

See Cell Switching.

Cellular Telecommunications Industry Association



Code Excited Linear Prediction. An analog-to-digital voice coding and compression scheme used in the transmission of voice over packet data networks. VoFR (Voice over Frame Relay) and VoIP (Voice over Internet Protocol) are excellent examples. CELP, and its several derivatives, depend on a "code book," which essentially is a binary (digital) description of a set of voice samples. All voice starts out as an analog signal, of course. The first step is the conversion of that analog signal is to convert it to a digital (data) format. This step is accomplished in a codec ( coder /decoder) through the use of a standard technique known as PCM (Pulse Code Modulation). PCM involves the sampling of the analog voice stream at very precise points in time. Specifically, PCM involves the sampling of the amplitude (volume level) of the voice stream every 125 microseconds, or every 8,000th of a second. Each sample is converted into an 8-bit byte, which describes its value in digital terms. Now, PCM was designed with digital circuit switching and TDM (Time Division Multiplexing) in mind. Circuit switches provide bandwidth (capacity) on demand, as available, and on a basis which is temporary, exclusive and continuous in nature. Digital circuits such as T-1 rely on TDM, as do digital circuit switches. TDM provides time slots (slots of time) spaced every 8,000th of a second, in consideration of the voice application for which they were developed. Therefore, from end-to-end and through all of the switches and transmission facilities, PCM-based voice is supported very effectively. But it turns out that PCM is not very efficient. That is to say that voice can be compressed to a considerably greater extent than PCM does. Further, compressed voice can be transmitted quite effectively over packet-switched networks, which certainly are more efficient than their circuit-switched counterparts.

CELP involves the gathering in a buffer of a set of 80 PCM voice samples, representing 10 ms (10 milliseconds , or 1/100th of a second) of a voice stream. Once gathered, the set of voice samples is considered as a block of data. The data block is compressed to remove silence and redundancy, the volume level is normalized, and the resulting smaller data set is compared to a set of candidate descriptions in the codebook . The data transmitted across the network are only the index number of the selected code description, and the average loudness level of the set of samples. Every 10 ms, the code is sent across the network in a block of 160 bits, yielding a data rate of 16 Kbps, which compares very favorably with PCM voice over circuit-switched TDM networks at 64 Kbps. The compression rate is 4:1. At the receiving end of the transmission, the transmitted code is compared to the code book, the PCM signal is reconstructed and, eventually, an approximation of the analog signal is reconstructed. The reproduction is not perfect, but generally is close enough to yield good perceived quality through this process of voice synthesis. The devices which perform these processes of compression and decompression are DSPs (Digital Signal Processors), which include the basic codec function. This definition is courtesy of "Communications Systems & Networks," a great book written by Ray Horak, who is my Contributing Editor. Since you already have either bought this book, or have borrowed it from a colleague, or have stolen it, let me recommend that you buy Ray's book. Together, his book and this book tell the whole story. See also Circuit Switching, PCM, and TDM. See also the following derivatives of CELP: ACELP, CS-ACELP, LD-CELP and QCELP.


At a glance, the Celsius scale makes more sense than the Fahrenheit scale for temperature measuring. But its creator, Anders Celsius, was an oddball scientist. When he first developed his scale, he made freezing 100 degrees and boiling zero degrees. No one dared point this out to him, so fellow scientists waited until Anders Celsius died to change the scale.


Controlled Environment ManHole. Environmental control of the CEMH is maintained by a heat pump (a fancy name for an airconditioner ” cooler and heater).


Comite European de Normalisation (French); the English translation is European Committee for Standardization. CEN is responsible for European standardization in all fields except electrotechnical (CENELEC) and telecommunications (ETSI). Certified products are awarded the CE Mark, signifying that a company has met the applicable essential health and safety requirements and the specific conformity assessment requirements to market its product in the European Union under the "New Approach" directives. CEN membership includes all EU countries, as well as affiliate members including Turkey, Cyprus, and many countries which formerly were members of the Soviet Bloc. Technical committees address standards in the areas of medical informatics, geographic information systems, character set technology for multilingual information, infrastructure, and advanced manufacturing technologies.


Comite European de Normalisation ELECtrotechnique (French); the English translation is European Committee for Electrotechnical Standardization. CENELEC is responsible for European standardization in the electrotechnical field, working closely with ETSI (telecommunications) and CEN (all other fields). Certified products are awarded the CE Mark, signifying that a company has met the applicable essential health and safety requirements and the specific conformity assessment requirements to market its product in the European Union under the "New Approach" directives. CENELEC is the European technical organization responsible for coordination of standards for safety and electromagnetic emissions for electrical equipment in the European Economic Community (EEC). The EEC is working toward having a uniform set of standards that will apply for all EEC countries. Membership includes all EU countries, as well as affiliate members including Turkey, Cyprus, and many countries which formerly were members of the Soviet Bloc.

Center Wavelength

In a laser, the center wavelength is the nominal value central operating wavelength. It is the wavelength defined by a peak mode measurement where the effective optical power resides. In an LED (Light Emitting Diode), it is the average of the two wavelengths measure at the half amplitude points of the power spectrum.

Central Office

CO. (pronounced See-Oh). Central office is an ambiguous term in North America. It can mean a telephone company building where subscribers' lines are joined to switching equipment for connecting other subscribers to each other, locally and long distance. Sometimes, that central office means a wire center in which there might be several switching exchanges. That means there will be switches, cable distribution frames , batteries, air conditioning and heating systems, etc. But a central office is sometimes simply a single telephone switch, what Europeans call a public exchange. In short, you have to figure out by the context if central office means a building or a switch, or a collection of switches. Simple, eh?

Central Office Battery

A group of wet cells joined in series to provide 48 volts DC. Central office batteries are typically charged off the main 120 volts AC. The batteries have two basic functions.

  1. To provide a constant source of DC power for eight hours or so after AC power drops , and

  2. To isolate the central office from glitches on the AC line.

Central Office Code

Part of the North American Numbering Plan (NANP), the central office code also is known as the central office prefix, the NXX code, and the end office code. A ten-digit telephone number in the U.S., for example, follows the format NXXNXX-XXXX, where N must be a number other than "0" or "1," and X can be any number. The first three digits (NXX) comprise the area code, the second three (NXX) comprise the local central office code, and the last four (XXX) comprise the "line number." Here is a definition from Bellcore (now called Telcordia Technologies): A 3-digit identification under which up to 10,000 (0000-9999) station numbers are subgrouped. Exchange area boundaries that generally have billing significance are associated with the central office code. Note that multiple central office codes may be served by a single central office. Also called NXX code or end office code. Several central office codes in North America are kept for special purposes:

555 ” Directory Assistance

950 ” Feature Group B Access

958 ” Local Plant Test

959 ” Local Plant Test

976 ” Information Delivery Service

Central Office Equipment Reports

COER. A telephone company definition. A large scale computer software package which accepts Central office Engineering Data properly formatted by a Data Collection System (DCS), subjects this data to a series of validation tests, and produces final summarized reports designed to meet both administrative and engineering requirements.

Central Office Override

A third party may interrupt or join in your conversation.

Central Office Trunk

  1. A trunk between central offices. It may be between major switches or between a major and a minor switch.

  2. A trunk between public and private switches.

Central Processing Unit

CPU. The part of a computer which performs the logic, computational and decision-making functions. It interprets and executes instructions as it receives them. Personal computers have one CPU, typically a single chip. It is the so- called "computer on a chip." That chip identifies them as an 8-bit, 16-bit or 32-bit machine.

Telephone systems, especially smaller ones, are not that different. Typically they have one main CPU ” a chip ” which controls the various functions in the telephone. Today's telephone systems are in reality nothing more than special purpose computers. As phone systems get bigger, the question of CPUs ” central processing units ” becomes harder to figure. The design of phone systems has, of late, tended away from single processor- controlled telephone systems (as in single processor controlled PCs). There are several reasons for this move. First, it's more economical for growth. Make modules of "little" switches and join little ones together to make big ones. Second, it's more reliable. It's obviously better not to rely on one big CPU, but to have several. In short, the issue of Central Processing Units ” CPUs ” is blurring. But the concept is still important because by understanding how your telephone switch works (its architecture), you will understand its strengths and weaknesses.

Central Site

A central site is a location that acts as a data collection point for remote and branch offices, as well as telecommuters and travelers.

Centralized Attendant Service

Calls to remote (typically branch) locations are automatically directed to operators at a central location. Imagine four retail stores in a town. There are three branch stores and one main, downtown store, each having its own local phone numbers, which customers call. It's clearly inefficient to put operators at each of the stores ” when one group is busy, the other will be free, etc. What this feature does is to direct all the calls coming into each of the stores into one bank of operators, who then send those calls back to the outlying stores.

Despite the extra schlepping of calls around town, having one large group of operators is cheaper than maintaining many small groups. Each store has its own local Listed Directory Number (LDN) Service. Special Release Link Trunk circuits connect each unattended location (each store) to the main attendant location. These trunks are only temporarily used during call processing. An incoming call to an unattended store seizes such a trunk circuit for completion of the call to the centralized attendant, who then uses the same trunk circuit to process the call to the remote location's internal extension. (After all if the caller was calling that store, they obviously want to talk to someone in that store.) The circuit is then released and is available for other calls. Since such special trunk circuits are only used during that part of a call that requires connection between locations, such trunks are more efficient than normal tie trunk circuits.

Centralized Automatic Message Accounting

CAMA. The recording of toll calls at a centralized point.

Centralized Network Administration

See CNA.

Centralized Ordering Group

COG. An organization provided by some communications service providers (like a local phone company) to coordinate services between the companies and vendors .


Centrex is a contraction of Central Exchange. Centrex is a business telephone service offered by a local telephone company from a local central office (also called a public exchange). Centrex is basically normal single line telephone service with "bells and whistles," added. Those " bells and whistles" include intercom, call forwarding, call transfer, toll restrict, least cost routing and call hold (on single line phones).

Think about your home phone. You can often get "Custom Calling" features. These features are typically fourfold: Call forwarding, Call Waiting, Call Conferencing and Speed Calling. Centrex is basically Custom Calling, but instead of four features, it has 19 features. Like Custom Calling, Centrex features are provided by the local phone company's central office.

Phone companies peddle Centrex which is leased to businesses as a substitute for that business buying or leasing its own on-premises telephone system ” its own PBX, key system or ACD. Before Divestiture in 1984, Centrex was presumed dead. AT&T was, at that time, intent on becoming a major PBX and key system supplier. Then Divestiture came, and the operating phone companies recognized they were no longer part of AT&T, no longer had factories to support, but did have a huge number of Centrex installations providing large monthly revenues . As a result, the local operating companies have injected new life into Centrex, making the service more attractive in features, price, service and attitude. Here are the main reasons businesses go with Centrex as opposed to going with a stand- alone telephone system:

  1. Money. Centrex is typically cheaper to get into (the central office already exists). Installation charges can be low. Commitment can also be low, since most Centrex service is leased on a month-to-month basis. So it's perfect for companies planning an early move. There may be some economies of scale, also. Some phone companies are now offering low cost, large size packages.

  2. Multiple locations. Companies with multiple locations in the same city often are cheaper with Centrex than with multiple private phone systems and tie lines, or with one private phone system and OPX lines. (An OPX line is an Off Premise eXtension, a line going from a telephone system in one place to a phone in another. It might be used for an extension to the boss' home.)

  3. Growth. It's theoretically easier to grow Centrex than a standalone PBX or key system, which usually has a finite limit. With Centrex, because it's provided by a huge central office switch, it's hard, theoretically, to run out of paths, memory, intercom lines, phones, tie lines, CO lines, etc. The limit on the growth of a Centrex is your central office, which may be many thousands of lines.

  4. Footprint Space Savings. You don't have to put any switching equipment in your office. All Centrex switching equipment is at the central office. All you need at your office are phones.

  5. Fewer Operators because of Centrex's DID features. Having fewer operator positions saves money on people and space.

  6. Give better service to your customers. With Centrex, each person has their own direct inward dial number. Many people prefer to dial whomever they want directly rather than going through a central operator. Saves time.

  7. Better Reliability. When was the last time a central office crashed? Here are some of the features built into modern central offices: redundancy, load-sharing circuitry , power back-up, on-line diagnostics, 24- hour on-site personnel, mirror image architecture, 100% power failure phones, complete DC battery backup and battery power. Engineered to suffer fewer than three hours down time in every 40 years .

  8. Non-blocking. Trunking constraints are largely eliminated with Centrex, since a central office is so large.

  9. Minimal Service Costs. Repair is cheap. Service time is immediate. People are right next to the machine 24-hours a day. Phones and wires are the only things that require repair on the customers' premises. You can easily plug new phones in and unplug them yourself. All other equipment is in the central office. You need not hold inventory or test equipment.

  10. No technological obsolescence. Renting Centrex means a user has the ultimate flexibility ” ability to jump quickly into new technology. Central offices are moving quickly into new technologies, such as ISDN.

  11. Ability to manage it yourself. You can now get two important features previously available only on privately-owned self-contained phone systems (like PBXs):

    1. The ability for you, the user, to make changes to the programming of your own Centrex installation without having to personally call a phone company representative.

    2. The ability to get call detail accounting by extension and then have reports printed by a computer in your office. The phone company does this call accounting by installing a separate data line which carries Centrex call records back to the customer as those calls are made.

The above arguments are pro-Centrex. There are also anti-Centrex arguments. Central offices often run out of capacity. Centrex is also cable- intensive . A PBX with 20 trunks and 100 phones only needs 20 cable pairs from the user's office to the telephone company. A Centrex installation with the same configuration needs 100 pairs. Every time someone new joins your company, the phone company needs to install another cable pair from the central office to your new employee's desk. Sometimes, they have it. Sometimes, they don't. Delays can get extensive . What with the explosion of telecom demand in recent years ” individual fax machines, the Internet, etc. ”there just isn't enough copper in the ground, and a typical telco won't plow in the cable unless they receive a pay-off in three years.

The "big" key to Centrex traditionally comes down to price. In some cities the price of Centrex lines is lower than "normal" PBX lines. Of course, you can buy Centrex lines and attach your own PBX or key system to those Centrex lines. The big disadvantage of Centrex is that there are very few specialized Centrex phones able to take better advantage of Centrex central office features the way electronic PBX phones take advantage of PBX features.

Centrex is known by many names among operating phone companies, including Centron and Cenpac. Centrex comes in two variations ” CO and CU. CO means the Centrex service is provided by the Central Office. CU means the central office is on the customer's premises. See the following Centrex definitions.

Centrex Call Management

A Centrex feature that provides detailed cost and usage information on toll calls from each Centrex extension, so you can better manage your telephone expenses.

Centrex CCRS

Centrex Customer Rearrangement System. Computer software from New York Telephone that allows their Centrex customers to make certain changes in their own line and features arrangements. Other phone companies have similar services under different names.

Centrex CO

Indicates that all equipment except the attendant's position and station equipment is located in the central office. See Centrex.

Centrex CU

Indicates that all equipment including the dial switching equipment, is located on the customer's premises. See Centrex.

Centrex Extend Service

The name of a Bell Atlantic service. If you maintain offices in multiple locations ” or have work-at-home employees ” this service allows you to tie all your locations into one phone system. So everyone in your company can take advantage of Centrex features and services on a cost-efficient, call-by-call sharing basis. With Centrex Extended Service, you can even tie non-Centrex locations into your Centrex system.

Centrex SMDI

Have you ever called someone and been forwarded to their voice mail, and then had to enter their extension again. This is because their voice mail does not know where the call originated. The voice mail system does not know who you just called, All it knows is that it just received another call. SMDI is simply a modem link back to the central office supplying your Centrex system. This modem link will feed a computer at your location the information about incoming calls as they are forwarded through your system. It feeds the originating number and why the call is transferred, so you know whether the user didn't answer their phone or that it was busy.

To indicate the health of the SMDI link, it generates a heartbeat message every few seconds. If you don't receive a heartbeat within the time window, you know there is a problem with the SMDI link and know to restart the link. The one good thing about SMDI is the option that your voice mail system can control the status of message waiting indicators on the user's phone. They can either have a message waiting lamp on their phone, or use the "stutter dial tone" which causes a broken dial tone when the user picks up their phone.

Problems to watch out for... Since SMDI is a communications link, it can be broken. If the SMDI link goes down, make sure you build in the old two step method of finding out what extension the caller was attempting to call. Make sure you also offer a user directory in case the caller does not know the extension number. When the link goes down, make sure the system does not continue to send the message waiting status commands down an inactive link. SMDI stands for Standard Message Desk Interface or Simplified Message Disk Interface. See also SMDI.


The name of the printer manufacturer whose method of data transmission between a computer and a parallel printer has become an industry standard. See Centronics Printer Standard.

Centronics Printer Standard

The Centronics standard was developed by the Centronics company which makes computer printers. The Centronics standard is a 36-pin single plug/connector with eight of the 36-pins carrying their respective bits in parallel (eight bits to one character), which means it's much faster than serial transmission which sends only one bit a time. There are several types of Centronics male and female plugs and receptacles. So know which you want before you buy. The pinning ” the location and function of each of the 36-individual wires ” is standard from one Centronics cable to another.

The Centronics printer standard has been adopted by many printer and PC companies, including IBM. It is a narrower standard than the RS-232-C standard. The Centronics works only between a computer and a printer. It won't work over phone lines, unless conversion is done at either end. However, it is standard and has none of the dumb interface problems the RS-232-C standard does.

Centum Call Second

1/36th of an erlang . The formula for a centum call second is the number of calls per hour multiplied by their average duration in seconds, all divided by 100.


Chief Executive Officer.


Certificate Enrollment Protocol. Certificate management protocol jointly developed by Cisco Systems and VeriSign, Inc. CEP is an early implementation of Certificate Request Syntax (CRS), a standard proposed to the Internet Engineering Task Force (IETF). CEP specifies how a device communicates with a CA, including how to retrieve the public key of the CA, how to enroll a device with the CA, and how to retrieve a certificate revocation list (CRL). CEP uses Public Key Cryptography Standard (PKCS) 7 and PKCS 10 as key component technologies. The public key infrastructure working group (PKIX) of the IETF is working to standardize a protocol for these functions, either CRS or an equivalent.


Conf rence des administrations Europeanes des Postes et Tel communications (European Conference of Postal and Telecommunications Administrations ). Standards-setting body whose membership includes European Post, Telephone, and Telegraphy Authorities (PTTs). It in turn participates in relevant areas of the work of CEN/CENELEC. It was originally responsible for the NET standards, but these have subsequently been passed on to ETSI.

CEPT Format

Defines how the bits of a PCM carrier system of the 32 channel European type T-1/E-1 will be used and in what sequence. To correctly receive the transmitted intelligence, the receiving end equipment must know exactly what each bit is used for. CEPT format uses 30 VF channels plus one channel for supervision/control (signaling) and one channel for framing (synchronizing). All 8 bits per channel are used to code the waveshape sample. For a much better explanation, see T-1.


An ATM term. Cell Error Ratio: The ratio of errored cells in a transmission in relation to total cells sent in a transmission. The measurement is taken over a time interval and is designed to be measured on an in-service circuit.


Centralized Emergency Reporting Bureau. A Canadian term similar to PSAP ” Public Safety Answering Position. See PSAP.

Cerf, Vinton

Founding President of the Internet Society (ISOC) from 1992 to 1995 and co-creator of the transmission control protocol/Internet Protocol (TCP/IP), which enables computers to talk to each other over the Internet. Cerf proved that a network can reconfigure itself so that no communications are lost. He did this by breaking apart the Defense Department's Arpanet network artificially, and showing that it could be reconnected by way of flying packet radios in Strategic Air Command jets . Cerf used the airborne radios to link to ground radios which were, in turn, linked to internet gateways (today's routers) to effectively interconnect the artificially separated pieces of ARPANET artificially separated. See also Kahn, Robert.


European Laboratory for Particle Physics Research in Geneva, Switzerland.


Computer Emergency Response Team. The CERT is a group of computer experts at Carnegie-Mellon University chartered to work with the Internet community to facilitate its response to computer security events involving Internet hosts , to take proactive steps to raise the community's awareness of computer security issues and to conduct research targeted at improving the security of existing systems. The CERT was formed by DARPA in November 1988 in response to the Internet worm incident. They maintain an archive of security- related issues on their FTP server at "cert.org." Their email address is "cert@cert.org "and their 24-hour telephone Hotline for reporting Internet security issues is 412-268-7090.


A cryptography term. Also known as a digital certificate, a "certificate" is a password-protected, encrypted data file which includes the name and other data which serves to identify the transmitting entity. The certificate also includes a public key which serves to verify the digital signature of the sender, which is signed with a matching private key, unique to the sender. Through the use of keys and certificates, the entities exchanging data can authenticate each other.

Certificate Authority

CA. A trusted third-party organization or company that issues digital certificates used to create digital signatures and public-private key pairs. These pairs allow all system users to verify the legitimacy of all other system users with assigned certificates. The role of the certificate authority is to guarantee that the individual granted the unique certificate is, in fact, who he or she claims to be. Usually, this means that the certificate authority has an arrangement with a financial institution, such as a credit card company, which provides it with information to confirm an individual's claimed identity. Certificate authorities are a critical component in data security and electronic commerce because they guarantee that the two parties exchanging information are really who they claim to be. See also Certificate and Digital Certificate.

Certificate of Public Convenience and Necessity


Certification Practice Statement

This term originates in the American Bar Association's Digital Signature Guidelines where it is defined as a "statement of the practices which a certification authority employs in issuing certificates."


Several companies in the "secondary" industry test used equipment, parts and/or systems. They have various ways of testing them. Typically they test with working phones operating for extended periods at different temperatures . The idea is to check that this used equipment works the way it's meant to work ” to the original manufacturer's design specification. Once these tests have been completed a secondary dealer will " certify " such equipment, usually in writing. Such certification carries the assurance that the used equipment works as it's meant to. Sometimes certified equipment is upgraded to the most current revision level of hardware and software. Sometimes it's not. You, the buyer, must check. Certified equipment typically carries a guarantee ” that guarantee being as good, obviously, as the company that backs it. See also NATD, Refurbished, and Remanufactured.

Certified Equipment

A term used in the secondary telecom equipment business. Equipment carrying the written assurance that it will perform up to the manufacturer's specifications. It qualifies for addition to existing maintenance contracts.


An ATM term. Circuit Emulation Service: The ATM Forum circuit emulation service interoperability specification specifies interoperability agreements for supporting Constant Bit Rate (CBR) traffic over ATM networks that comply with the other ATM Forum interoperability agreements. Specifically, this specification supports emulation of existing TDM circuits over ATM networks.


Caller Emergency Service ID. Several states in the United States require PBXs to send a telephone extension number to a PSAP (E-911 emergency answering point). This is helpful in cases where the caller is not located near the address listed for the business' Listed Directory Number. A "campus" environment of separate buildings comes to mind. The location information displayed at the PSAP usually comes from the ALI (Automatic Location Identification) database. Customers with PBXs are normally required to provide initial telephone location information as well as updates to the ALI database maintainer (usu- ally the LEC). The CESID information is transmitted in one of two formats: ISDN-PRI ANI (around Chicago and in some areas of New York), or CAMA. CAMA uses R2MF signaling to send the CESID to the PSAP, and, like ISDN-PRI, has to be ordered as a specific type of trunk from the LEC. Unlike ISDN-PRI, however, it appears to have no other use aside from E-911 calls. Until or unless PSAPs in the rest of the country switch over to ISDN-PRI trunks for call receipt, CAMA trunks will be around for awhile. See CAMA, E-911, ISDN PRI, LEC and PSAP.


See International Atomic Time.

Cesium Clock

A clock containing a cesium standard as a frequency-determining element. It's a very accurate clock. See Cesium Standard and International Atomic Time.

Cesium Standard

A primary frequency standard in which a specified hyperfine transition of cesium-133 atoms is used to control the output frequency. Its accuracy is intrinsic and achieved without calibration. See International Atomic Time.


Commercial End User. See SU, service user.


Controlled Environmental Vault. A below ground room that houses electronic and/or optical equipment under controlled temperature and humidity.


  1. Carrier Facility Assignment. CAPs/CLECs give RBOCs/LECs a slot or channel assignment where their T-1s or T-3s will be connecting. A CFA is the identifier or location where an IXC, CAP, CLEC, or LEC will interconnect with the incumbent Telco. It will come in one of three forms: ACTL/CLLI, APOT, or tie/cable pair. ACTL/CLLI looks like 1001/T3/18/WASHDCAB123/WASHDCXY789, where 1001 is the DS-3 off a SONET OC ring, while T3 signifies that connection will be made at the T-3 slot 18 (the T-1 will connect to this slot). The first location CLLI is the ACTL WASHDCCAB123. The second location CLLI is the central office CLLI WASHDCXY789. If the CFA is in APOT form, it will be like (i.e. floor.aisle.bay.panel.jack). Tie/cable pair looks like 10011/t3/T1TIE/WASHDCAB123/WASHDCAB where the last 1 in 10011 signifies slot 1. The Telco tech will then do the interconnect or x-connect at that facility assignment. See CAP, CLEC and RBOC.

  2. Carrier Failure Alarm. The alarm which results from an out-of-frame or loss of carrier condition and which is combined with trunk conditioning to create a CGA.

  3. Connecting Facilities Arrangement. Identifies a complete communications channel between two places.

  4. Connecting Facility Assignment. The facility designation of the high-capacity system that the line or trunk is using.


Call Forward All Calls.


Call Forwarding Address Modified Notification.


  1. Call Forward Busy.

  2. Call Forwarding on mobile subscriber Busy. A wireless telecommunications term. A supplementary service provided under GSM (Global System for Mobile Communications).


Communications Fraud Control Association. Founded in 1985, CFCA is a not-for- profit international educational association working to help combat telecommunications fraud. CFCA seeks to promote a close association among telecom security personnel, to enhance their professional status and efficiency, and to serve as a clearinghouse of information pertaining to the fraudulent use of telecommunications services. CFCA membership is includes interexchange carriers (IXCs); local exchange carriers (LECs); competitive local exchange carriers (CLECs), incumbent local exchange carriers (ILECs), private network companies, law enforcement officers; users, e-mail providers, security product vendors, and corporations that use telecommunication services. www.@cfca.org.


Call Forward Don't Answer.


Call Forward Group Don't Answer.


  1. Cubic Feet per Minute. A measure of how much air you move through the fan of a PC.

  2. Carrier Financial Management.


Call Forwarding on mobile subscriber Not Reachable. A wireless telecommunications term. A supplementary service provided under GSM (Global System for Mobile Communications).


Call Forwarding on No Reply. A wireless telecommunications term. A supplementary service provided under GSM (Global System for Mobile Communications).


Chief Financial Officer.


Channel Frame Processor.


  1. Confirmation to Receive frame.

  2. Code of Federal Regulations.


Carbon Fiber Reinforced Plastic. A light and durable material, which has been used (for the wings of advanced fighter jets) in the defense business and which Toshiba introduced in 1991 as casing for a line of notebook sized computer laptops.


Call Forwarding UnConditional. A wireless telecommunications term. A supplementary service provided under GSM (Global System for Mobile Communications).


Call For Votes. Begins the voting period for a Usenet newsgroup. At least one (occasionally two or more) email addresses is customarily included as a repository for the votes .


Call Forward.


  1. Carrier Group Alarm. A service alarm generated by a channel bank when an outof-frame (OOF) condition exists for some predetermined length of time (generally 300 milliseconds to 2.5 seconds). The alarm causes the calls using a trunk to be dropped and trunk conditioning to be applied.

  2. Color Graphics Adapter. An obsolete IBM standard for displaying material on personal computer screens. The simplest (and conventional) CGA displays 320 horizontal picture elements, known as pels or pixels, by 200 pels vertically. There is also an Enhanced CGA, which is 640 x 400, or 128,000 pixels per screen. Older portables may use CGA monochrome mode. CGA has essentially been obsoleted by VGA. See Monitor and VGA.


Common Gateway Interface. An Internet term. Let's start simple. You write a form on a web site which you want visitors to fill in ” let's say their email address and phone number. You write some software, also called a script, which presents the visitor with the form and ask him/her to kindly fill it out. That software is usually executed on the Web server. CGI originally referred to the pre-defined way in which these programs communicated with the Web Server but lately it has come to refer to the programs themselves . The preferred programming language for CGI scripts is Perl. Forms are usually processed by CGI (Common Gateway Interface) scripts. CGI is basically a standardized way of sending information between a server and a processing script. CGI scripts are typically written in Perl or some other programming language such as C++, Java, VBScript, or JavaScript. Before creating interactive forms on your web site, you must check with your ISP or server administrator to see if CGI scripts can run on your server. See also CGI-Bin, PERL and Servlet.


A directory on a server that "houses" all of the CGI programs. When you see this as a directory in your browser's URL window, it usually means you are either running or about to run a CGI program. The "binary" part refers to when many of the files placed in that directory were binary files. More recently, many of these files are text-based. CGIBin is the most common name of a directory on a web server in which CGI programs are stored. The "bin" part of "cgi-bin" is a shorthand version of "binary" because once upon a time, most programs were referred to as "binaries." In real life, most programs found in cgi-bin directories are text files ” scripts that are executed by binaries located elsewhere on the same machine.


A Wired Magazine definition. A hardcore CGI script programmer with all the social skills and charisma of a plastic action figure.

CGI Script

See CGI.


Computer Graphics Metafile. A standard format that allows for the interchanging of graphics images.


Cellular Geographic Service Area. The actual area in which a cellular company provides cellular service. CGSAs are usually made up of multiple counties and often cross state lines.

CGSA Restriction

If you own a cellular phone, you are prevented from making calls outside your own local Cellular Geographic Service Area. This restriction is an option that is available to subscribers in most cellular cities.


  1. The little solid round dots of paper made when paper tape is punched with information. Also the little rectangular pieces of paper that are made when any sort of punch card is used for data input purposes. Carriers used to use a lot of paper tape for AMA (Automated Message Accounting) purposes in recording long distance calls, but that's all been replaced by magnetic tape and other electronic media. We used to use a lot of punch cards for all sorts of computer data input purposes, be that's all been replaced , as well. One of the rare exceptions is the continuing use of obsolete punch card technology is U.S. voting machines. It's interesting to note that Al Gore, who erroneously claimed to be the "Father of the Internet," also erroneously claimed to have lost the 2000 presidential election due to obsolete punch card voting machines in Florida.

  2. CHAnge Display.

Chad Tape

Punched tape used in telegraphy/teletypewriter operation. The perforations, called "chad," are severed from the tape, making holes representing the characters .

Chadless Tape

  1. Punched tape that has been punched in such a way that chad is not formed.

  2. A punched tape wherein only partial perforation is completed and the chad remains attached to the tape. This is a deliberate process and should not be confused with imperfect chadding. See Chad.

Chain Mailboxes

Mailboxes that are connected together to provide a service or a number of messages (e.g. Directory, Product Information, etc.).


A group of Web homepages which merely link to each other.


A programming technique linking one activity to another, as in a chain. Each link in the chain may contain a pointer to the next link, or there may be a master control or program instructing the programs to link together.

Chainsaw Consultant

An outside "expert" brought in to reduce the employee headcount, leaving the top brass with clean hands and a clean conscience.

Chalk Talk

A PowerPoint presentation.

Challenge Email

Let's say you're sick of all the spam mail. You set up a system whereby to every email that comes your way, you send an email asking the sender of your email a question. If the person replies to your email the correct way, they are allowed to send emails to you. This method of cutting back on spam is called "challenge email."

Challenge-Handshake Authentication Protocol

CHAP. An authentication method that can be used when connecting to an Internet Service Provider. CHAP allows you to log in to your provider automatically, without the need for a terminal screen. It is more secure than the Password Authentication Protocol (another widely used authentication method) since it does not send passwords in text format. An Internet term.


A type of authentication procedure into a system in which a user must respond correctly to a challenge, usually a secret key code, to gain access.


Indicating an undesirable or unappealing condition. People who are "intellectually challenged" are stupid.

Chalk Talk

When your professor explains it on the blackboard, that's called chalk talk. This term has now been extended to anyone using foils, overheads or PowerPoint.

Change Management

Change management is the process of introducing controlled change during the project life cycle. The intent behind a change control process is to evaluate the risk, at the end-user level, against the urgency and importance of the change. IT organizations must establish a specific change control process for every type of change and consider a procedure specific to rapid and emergency changes. The creation of these processes must involve several groups, including users, developers, and operations. Successful change management is not only a matter of skill and expertise, it is also a question of where the team draws its support from the company hierarchy. Source: Giga Information Group.


  1. Typically what you rent from the telephone company. A voice-grade transmission facility with defined frequency response, gain and bandwidth. Also, a path of communication, either electrical or electromagnetic, between two or more points. Also called a circuit, facility, line, link or path .

  2. An SCSA term. A transmission path on the SCbus or SCxbus Data Bus that transmits data between two end points.

  3. A channel of a GPS (Global Positioning System) receiver consists of the circuitry necessary to tune the signal from a single GPS satellite.

  4. A shortened way of saying "distribution channel." Let's say you make a product ” hardware or software. You need to have some way of selling it. You can sell it yourself with your own salespeople. Or you can give it to distributors to sell. Such distributors could be wholesalers, small retailers, large retail chains, direct mail catalogs, etc. Each one of these categories is called a "channel." See also Channel Conflict, Channel Management and Channel Ready.

  5. A Fibre Channel term. A point-to-point link, the main task of which is to transport data from one point to another.

Channel 1

When the FCC first allocated broadcast TV frequencies in 1945 in the United States. Later, the FCC decided that TV was taking up too much broadcast spectrum. Each channel requires a bandwidth 600 times as wide as an individual radio station does. Thus, the Channel 1 band , 44 to 50 MHz, was reassigned for mobile radio use.

Channel Aggregator

Also known as inverse multiplexors. Devices that allow very large amounts of data to be sent down the narrow band channels of ISDN. The aggregator effectively pulls together ISDN channels at one end to form a higher bandwidth and then re-synchronizes the information at the other end. Re-synchronization is necessary because during transmission the ISDN channels may send the information along different routes, so it arrives at its destination at fractionally different times.

Channel Associated Signaling

CAS. A form of circuit state signaling in which the circuit state is indicated by one or more bits of signaling status sent repetitively and associated with that specific circuit.

Channel Attached

Describing the attachment of devices directly to the input/output channels of a (mainframe) computer. Devices attached to a controlling unit by cables rather than by telecommunications circuits. Same as locally attached (IBM).

Channel Bank

A multiplexer. A device which puts many slow speed voice or data conversations onto one high-speed link and controls the flow of those "conversations." Typically the device that sits between a digital circuit ” say a T-1 ” and a couple of dozen voice grade lines coming out of a PBX. One side of the channel bank will be connections for terminating two pairs of wires or a coaxial cable ” those bringing the T-1 carrier in. On the other side are connections for terminating multiple tip and ring single line analog phone lines or several digital data streams. Sometimes you need channel banks. Sometimes, you don't. For example, if you're shipping a bundle of voice conversations from one digital PBX to another across town in a T-1 format ” and both PBXs recognize the signal ” then you will probably not need a channel bank. You'll need a Channel Service Unit (CSU). If one, or both, of the PBXs is analog, then you will need a channel bank at the end of the transmission path whose PBX won't take a digital signal. See Channel Service Unit and T-1.

Channel Capacity

A measure of the maximum possible bit rate through a channel, subject to specified constraints.

Channel Capture

A condition that occurs when the Ethernet MAC layer temporarily becomes biased toward one workstation on a loaded network, thereby making that one station the contention winner more times than would randomly occur.

Channel Coding

The process of adding redundant information into a transmitted bit stream before transmission in order to protect the bit stream from errors that may occur. Channel coding therefore reduces the error rate in a channel, but increases the amount of information (overhead) that must be transmitted. Typical methods of channel coding include forward error correction, error detection schemes, and interleaving of bits.

Channel Compression

The process of fitting more than one program into a single channel. See Analog Channel Compression and Digital Channel Compression.

Channel Conflict

Channel conflict happens when a manufacturer wants to sell over the web, but a brick-n-mortar retailer that manufacturer sells through says, "If you sell your products directly on your web site, we'll stop carrying your brand or relegate it to the bottom shelf." The physical distribution channel is in conflict/competition with the e-commerce distribution channel. Sometimes this problem is solved by the manufacturer agreeing to keep his prices at full retail on his web site. Other times it's solved by the manufacturer simply saying ” Sorry, but we're going ahead anyway. Other times it is solved by the manufacturer dropping its idea of selling on the web and simply having its web site as an product information site, with links directly to its retailers ” some of which may run sell over the Internet.

Channel Converter

A device which converts signals from one channel to another channel. There are two types ” heterodyne converters and those which use frequency multiplication principles. See Heterodyne Converter and Processor.

Channel Definition Format

An open standard announced by Microsoft in March 1997 to be presented to the World Wide Web Consortium (W3C) as a suggested future open standard for "push" technology.

Channel Efficiency

In a LAN environment, a measure of the total information that can be communicated in a channel in a unit of time, accounting for noise, collisions and other disruptions.

Channel Gate

A device for connecting a channel to a highway, or a highway to a channel, at specified times.

Channel Hopping

A cellular radio term. Channel Hopping is the process in CDPD of changing the Radio Frequency (RF) channel supporting a CDPD channel stream to a different RF channel on the same cell. This is typically used to avoid collisions with voice traffic use of the RF channel.

Channel Identification

Information element that requests or identifies the channel to be used for a call. An AIN term.

Channel Loopback

In network management systems, diagnostic test that forms a loop at the multiplexer's channel interface that returns transmitted signals to their source. See also Loopback.

Channel Management

Since the last of the HP/Compaq merger much has been written. Now that shareholders have approved the deal, it is interesting to look at one of the most critical aspects of this and any merger - channel management. HP and Compaq each support broad product lines with unique distribution strengths. HP is known for its reseller channel, while Compaq is lauded for its direct marketing strength. The potential for conflict is obvious. While the aim of the merger it to increase sales, HP resellers are rattled by the fear of being cut out by greater adoption of Compaq's direct selling tactics. Moreover, much of the Compaq and HP reseller network find themselves with indistinct product lines. Pundits correctly predict that the dealer channel will be cut back to reduce costs. Only Value Added Resellers (VARs) offering true added value will survive, as the industry moves towards the Dell direct sales model. In this rather confusing environment, resellers naturally become nervous and some of the better VARs defect to the competition. In meeting this challenge the new HP needs to focus on two key words, clarity and communication. Clarity - the merged company must offer a clear and consistent policy regarding a wide range of questions concerning VARs. Which product lines will be retained and which will be dropped? What happens to brands? Which products will be pushed through the expanded HP direct sales channel and which will remain exclusively in the VAR channel? How will VAR pricing change, if at all? Which VARs will be dropped? Communication - the new HP cannot afford to confuse VARs. Ongoing communication is critical if VARs are to stay happy and continue to push products. If the messaging is badly managed, HP can expect to loose good VARs to the competition and see sales drop. The aim of all mergers is to create a larger, stronger company. With a huge VAR channel to manage, the new HP must move fast to shore up its partner network.

Channel Mode

An AT&T term for a method of communications whereby a fixed bandwidth is established between two or more points on a network as a semi-permanent connection and is rearranged only occasionally.

Channel Model

See Inifiniband.

Channel Modem

That portion of multiplexing equipment required to derive a desired subscriber channel from the local facility.

Channel Packing

A technique for maximizing the use of voice frequency channels used for data transmission by multiplexing a number of lower data rate signals into a single higher speed data stream for transmission on a single voice frequency channel.

Channel Queue Limit

Limit on the number of transmit buffers used by a station to guarantee that some receive buffers are always available.

Channel Rate-Adaptation Protocols

These protocols tell the ISDN terminal adapter (TA) how to change its transmission/ reception speeds to match those of the connecting device. Europe and Japan primarily use the V.110 protocol. The U.S. uses V.120. See ISDN and Protocol.

Channel Ready

A channel is a shortened way of saying "distribution channel." Let's say you make a product ” hardware or software. You need to have some way of selling it. You can sell it yourself with your own salespeople. Or you can give it to distributors to sell. Such distributors could be wholesalers, small retailers, large retail chains, direct mail catalogs, etc. Each one of these categories is called a "channel." Channel Ready means that your product is in a form your chosen channel can handle. Typically this means that your software and/or hardware comes and can be delivered in a shrinkwrapped box and that you have set an organization which can service, support, train and otherwise satisfactorily deal with customers contacting you.

Channel Seized

The time when a connection is established between the cellular user's mobile equipment and the mobile telephone switching office (MTSO). Channel seizure occurs before the number dialed begins to ring.

Channel Service Unit

CSU. A device used to connect a digital phone line (T-1 or Switched 56 line) coming in from the phone company to either a multiplexer, channel bank or directly to another device producing a digital signal, e.g. a digital PBX, a PC, or data communications device. A CSU performs certain line-conditioning, and equalization functions, and responds to loopback commands sent from the central office. A CSU regenerates digital signals. It monitors them for problems. And it provides a way of testing your digital circuit. You can buy your own CSU or rent one from your local or long distance phone company. See also CSU and DSU.

Channel Splitter

A channel splitter transmits channels one through 12 over one wire pair and channels 13 through 24 over another wire pair.

Channel Stream

A cellular radio term. Channel Stream is a shared digital communications channel between a Mobile Data Base Station (MDBS) and a set of Mobile End Systems (M-ESs) considered as a logical concept, separate from the frequency of the Radio Frequency (RF) channel used to implement the channel at any given time.

Channel Surfing

Flipping channels on a TV set. A person who channel surfs is called a Mouse Potato.

Channel Terminal

That portion of multiplexing equipment required to derive a desired subscriber channel from the bearer facility.

Channel Termination

Central Office (CO) equipment at the telephone company side of a local loop, a channel termination is used to terminate an end user's network access circuit, channel-by-channel. For a T-1 circuit, channel termination equipment commonly is in the form of two ports on a channel bank, one for the upstream circuit and one for the downstream circuit. Dedicated, multichannel T-1 circuits typically involve a recurring monthly charge in each direction, per channel.

Channel Tier

An AT&T term for the tier within the Universal Information Services network that partitions transmission capacity into channels and offers the channels to the nodes' higher tiers.

Channel Time Slot

A time slot starting at a particular instant in a frame and allocated to a channel for transmitting a character, in-slot signal, or other data. Where appropriate a modifier may be added.

Channel Translator

Device used in broadband LANs to increase carrier frequency, converting upstream (toward the head-end) signals into downstream signals (away from the head-end).

Channel Virtual Area

Where Internet Relay Chat (IRC) users communicate in real time. There are thousands of channels on the Internet.


The process of subdividing the bandwidth of a circuit into smaller increments called channels. Typically, each channel carries an individual transmission, e.g. a voice conversation or a data conversation ” a computer-to-computer session. Multi- channel circuits always are four-wire in nature, whether physical four-wire or logical four- wire, and the process of channelization is always accomplished through some form of multiplexer (MUX), which can be in the form of either a Frequency Division Multiplexer (FDM) or a Time Division Multiplexer (TDM). The most basic type of MUX is known as a channel bank. Traditional T-1 service is a channelized service, for instance. Through a Statistical Time Division Multiplexer (STDM), a T-1 circuit of 1.544 Mbps is subdivided into 24 channels of 64 Kbps each, with an additional 8 Kbps needed for framing overhead (do the math and you'll see). Each channel (at least for contemporary multiplexers employing ESF, or Extended SuperFrame) provides a full 64 Kbps of bandwidth in support of a single "conversation" (data or voice), which requirement was established for transmission of digitized voice according to the original PCM (Pulse Code Modulation) encoding algorithm. Older multiplexers provided only 56 Kbps of usable channel capacity due to the fact that they employed an intrusive form of signaling and control. The STDM subdivides the digital bandwidth of the circuit into 24 smaller units of bandwidth known as "time slots" through a sampling process. Picture a 24 lane highway leading up to one toll booth. On the other side of the toll booth is a one lane highway. The vehicles in the 24 lanes are allowed through the toll booth ( each of the 24 input devices is allotted a piece of time in which it is allowed to send data) if they are ready to pay the toll. If they do not have the toll fee available the attendant will ask the next vehicle to go through (the TDM polls the next device during the next, (fixed) time slot). In TDM devices are polled (asked) if they have anything to transmit during their preordained time slot. If they do not have anything to send, that time slot cannot be used by another device which may have something to send. This is wasted bandwidth. This is traditional TDM. In contrast, Statistical Time Division Multiplexing (STDM) asks why waste the time slot if some other device is ready to send? STDM is a non-channelized way of using the available bandwidth. It allocates time slots to those devices who are ready to send. This principle is called "Bandwidth on Demand". FDMs subdivide bandwidth through a process of frequency separation, with each conversation occupying a separate and distinct frequency within a larger range of frequencies supported by the circuit. While FDM is seldom employed in the contemporary world of electrically-based (read copper wire) circuits, it is widely used in the wireless world (e.g., cellular and PCS). FDM also is widely employed in the fiber optic world, where it is known as WDM (Wavelength Division Multiplexing) or DWDM (Dense WDM). WDM supports multiple, very high-capacity virtual circuits over a single optical fiber, with each virtual circuit being subdivided into a very large number of TDM channels. See also Bandwidth, Channel, Channel Bank, DWDM, FDM, MUX, PCM, STDM, T-1, TDM, and WDM.


See Channelization.

Chaos Theory

Developed by Edward Lorenz in the 1960s, chaos theory states that simple systems may produce complex behavior. It also has been proven that complex systems possess a simple underlying order. The emerging scientific discipline of chaos theory deals with systems with boundaries that are not clearly defined, with a "system" being defined as a set of things which interact. A computer system, for instance, is a set of elements including perhaps hardware, firmware, application software, CPU, hard drive, I/O devices, terminal devices, peripheral devices, drivers, and so on. Ideally, these system elements work together to consistently yield a predictable, desired result. In the context of a complex computer system, chaos theory describes a condition in which the system behaves in a nonlinear, inherently unpredictable manner. Chaos theory commonly is known as the "butterfly effect," with the analogy being that a butterfly flapping its wings in the Amazon Valley may create slight disturbances in the air which may ultimately affect worldwide weather patterns, perhaps resulting in the creation of a cyclone in Southeast Asia some years later. In this analogy, the complex weather system possesses a simple underlying order, although the interaction of the various elements clearly is nonlinear. But I digress. In the context of an information system, the addition of line of a line of computer code or the installation of a new application software package may cause the system to crash or to corrupt data residing in a seemingly unrelated application. That is chaos theory. The theory is fascinating. The practical impact is frightening, especially as systems and networks (comprised of systems) grow ever more complex.


Challenge-Handshake Authentication Protocol. An authentication method that can be used when connecting to an Internet Service Provider. CHAP allows you to log in to your provider automatically, without the need for a terminal screen. It is more secure than the Password Authentication Protocol (another widely used authentication method) since it does not send passwords in text format. An Internet term.

Chapter 7

See Chapter 11.

Chapter 11

The Chapter 11 process is started when a company files a reorganization petition with the federal Bankruptcy Court. From that moment on, creditors are prevented from suing the company, and any creditor lawsuits in process are halted, pending the outcome of the Chapter 11 reorganization. Creditors of the company file claims with the Bankruptcy Court. A creditors committee, usually made up of the seven creditors who have filed the largest claims against the company, represents the interest of all creditors. Under Chapter 11 protection, the company's management usually continues to manage the company's business, subject to judicial review. In rare circumstances, such as fraud, a party may ask the court to appoint a trustee to manage the company during reorganization. The ultimate objective of a Chapter 11 reorganization is to restructure creditors' claims so that the company can move ahead with its business. Company management includes a negotiated partial payment to creditors. The plan also can include exchanges of debt for equity, a moratorium on repayment or a combination of these actions. In some cases, more than one plan may be proposed. For example, a creditor, or group of creditors, may develop its own plan. The complex process of reaching a consensual plan entails extensive negotiations among the company, its creditors and its shareholders.

Once developed, the company's reorganization plan ” or one of the competing plans ” must be accepted by specified margins of creditors and shareholders. Creditors representing two-thirds of the total dollar amount of bankruptcy claims against the company and 51 percent of the total number of those voting must accept the plan, and two- thirds of the amount of shares represented by shareholders voting on the plan must approve it for a plan to be accepted. Once accepted, the Bankruptcy Court reviews the plan to ensure that it conforms to certain additional statutory requirements before confirming it. With a restructured balance sheet, the company then emerges from Chapter 11 protection to implement the plan. Some companies emerge from Chapter 11 and become normal operating companies again. Some don't and move into Chapter 7 bankruptcy, which is complete and relatively immediate liquidation of the company (i.e. sale of all the company's assets).


A letter, a number or a symbol. A character is sometimes described by the digit represented by the bit pattern that makes up the Character. i.e., the letter A is ASCII code 65, a carriage return is ASCII code 13.

Character Cell

In text mode on a PC, each pel (Picture ELement) is called a character cell. Character cells are arranged in rows and columns. A typical PC will support two text modes ” 80 columns by 25 rows and 40 columns by 25 rows. The default text mode on virtually all PCs is 80 x 25. See Pel.

Character Code

One of several standard sets of binary representations for the alphabet, numerals and common symbols, such as ASCII, EBCDIC, BCD.

Character Distortion

In telegraphy, the distortion caused by transients that, as a result of previous modulation, are present in the transmission channel. Its effects are not consistent. Its influence upon a given transition is to some degree dependent upon the remnants of transients affecting previous signal elements.

Character Generator

CG. A computer used to generate text and sometimes graphics for video titles.

Character Impedance

The impedance termination of an electrically uniform (approximately) transmission line that minimizes reflections from the end of the line.

Character Interleaving

A form of TDM used for asynchronous protocols. A 20% saving can be obtained by omitting the start and stop bits. This can be used either with extra channels or by carrying RS-232-C control signals.

Character Interval

The total number of unit intervals (including synchronizing, information, error checking, or control bits) required to transmit any given character in any given communication system. Extra signals that are not associated with individual characters are not included. An example of an extra signal that is excluded in the above definition is any additional time added between the end of the stop element and the beginning of the next start element as a result of a speed change, buffering, etc. This additional time is defined as a part of the intercharacter interval.

Character Oriented Protocol

A communications protocol in which the beginning of the message and the end of a block of data are flagged with special characters. A good example is IBM Corp's. Binary Synchronous Communications (BSC) protocol. Character oriented protocols are used in both synchronous and asynchronous transmission.

Character Oriented Windows Interface

COW. An SAA-compatible user interface for OS/2 applications.

Character Printer

A device which prints a single character at a time. Contrast with a line printer, which prints blocks of characters and is much faster.

Character Set

All the letters, numbers and characters which a computer can use. The symbols used to represent data. The ASCII standard has 256 characters, each represented by a binary number from 1 to 256. This set includes all the letters in the alphabet, numbers, most punctuation marks, some mathematical symbols and some other characters typically used by computers. See ASCII.

Character Stuffing

A technique used to ensure that transmitted control information is not misinterpreted as data by the receiver during character-based transmission. Special characters are inserted by the transmitter and then removed by the receiver.

Character Terminal

A computer terminal that cannot show graphics, only text.

Characteristic Frequency

A frequency that can be easily identified and measured in a given emission. A carrier frequency may, for example, be designated as the characteristic frequency.

Characteristic Impedance

The impedance of a circuit that, when connected to the output terminals of a uniform transmission line of arbitrary length, causes the line to appear infinitely long. A line terminated in its characteristic impedance will have no standing waves, no reflections from the end, and a constant ratio of voltage to current at a given frequency at every point on the line.

Characters Per Second

CPS. A data transfer rate generally estimated from the bit rate and the character length. For example, at 2400 bps, 8-bit characters with Start and Stop bits (for a total of 10 bits per character) will be transmitted at a rate of approximately 240 characters per second (cps). Some protocols, such as USR-HST and MNP, employ advanced techniques such as longer transmission frames and compression to increase characters per second.


The process of allocating network and telecommunications line, equipment, and usage costs to departments or to individuals. Companies charge back to departments or to users. Colleges and universities charge costs back to departments and to students.

Charged Coupled Device

CCD. The full name of the term is Interline Transfer Charge Coupled Device or IT CCD. CCDs are used as image sensors in an array of elements in which charges are produced by light focused on a surface. They consist of a rectangular array of hundreds of thousands of light-sensitive photo diodes. Light from a lens is focused onto the photo diodes. This frees up electrons (charges) which accumulate in the photo diodes. The charges are periodically released into vertical shift registers which move them along by charge-transfer to be amplified.


Character Generation. Via TCP, a service that sends a continual stream of characters until stopped by the client. Via UDP, the server sends a random number of characters each time the client sends a datagram.


Slang. Seriously beyond all hope. Very badly broken.


A common name for a type of messaging done over a network, involving short messages sent from one node to another. Chatting usually happens in real-time, sometimes in just short messages, replied to quickly. Sometimes, chatting software is RAM-resident, meaning it can be "popped up" inside an application program. Users are usually notified of an incoming chat by a beep and a message at the bottom of their screens.

Chat Room

Real-time chat services offered by many Internet Information Service Providers such as America Online. Supporting a dozen or so participants , they act much like a teleconference, although on a text basis. Private rooms are those that can be entered by invitation . Public rooms allow anyone to participate.


A slang name for the thin wire coaxial cable (0.2-inch, RG58A/U 50- ohm) that uses a smaller diameter coaxial cable than standard thick Ethernet. Thin Ethernet is also called "Cheapernet" due to the lower cabling cost. Thin Ethernet systems tend to have transceivers on the network interface card, rather than in external boxes. PCs connect to the Thin Ethernet bus via a coaxial "T" connector. Thin Ethernet is now the most common Ethernet coaxial cable, though twisted pair is gaining. Thin Ethernet is also referred to as ThinNet or ThinWire. See also 10BASE-T.

Cheat Codes

In the Spring of 2002 two Vermont teenagers were caught for killing two Dartmouth College professors. The teenagers believed that the entire world was like a giant computer game and there were "cheat codes" that could allow you to take a shortcut to success. Cheat codes are often used in computer games to lessen the time needed to learn the game and speed up your chances of winning. Such cheat codes are often found on Web sites.

Check Bit

A bit added to a unit of data, say a byte or a word, and used for performing an accuracy check. See also Parity.

Check Characters

Characters added to the end of a block of data which is determined by an algorithm using the data bits which are sent. The receiving device computes its own check characters. It compares them with those sent by the transmitter. If they do not match, the receiver requests the sender to send the block again. If the check characters match, then all the bits used to compute the check characters have been received properly.

Check-In Mailbox

The Centigram VoiceMemo II mailbox used to assign names and passcodes for guests checking into a hotel.

Check-Out Mailbox

The Centigram VoiceMemo II mailbox used to clear out guest mailboxes when the guest checks out of the hotel.

Checkpoint Cycle

HDLC error recovery cycle formed by pairing an F bit with a previous P bit or vice versa.


HDLC error recovery based on pairing of P and F bits and giving the equivalent of a negative acknowledgment without using either REJ or SREJ.


The sum of a group of data items used for error checking. Checksum is computed by the sending computer based upon an algorithm that counts the bits going out in a packet. The check digit is then sent to the other end as the tail, or trailer of the packet. As the packet is being received, the receiving computer goes through the same algorithm, and if the check digit it comes up with is the same as the one received, all is well. Otherwise, it requests the packet be sent again.


The content of a commercial site that mainly consists of pictures of the products or other equally useless information.

Cheese Box

This is an old trick used by the boiler room operators to hide their real physical location from the vice squad. It was a call forwarding device placed in a empty room. Police would attempt to trace the location of a boiler room raid the spot where they thought the calls were being terminated at and find nothing but this device. Meanwhile a lookout for the operation would be watching and have his people shut down to avoid detection as the police got one step closer. The name for this device originated because the first time the police came across this piece of hardware it was fitted into a box originally containing cheese. See Boiler Room.


When a buffered fiber cable appears to stretch during stripping and then cheeses (creeps) back into the outer jacket of the cable, to resume its original place.

Chemical Rectifier

A chemical device for changing alternating current to pulsating direct, usually used for charging storage batteries.

Chemical Stripping

Soaking an optical fiber in a chemical to remove its coating.

Chemical Vapor Deposition

CVD. In optical fiber manufacturing, a process in which deposits are produced by heterogeneous gas-solid and gas-liquid chemical reactions at the surface of a substrate. The CVD method is often used in fabricating optical fiber preforms by causing gaseous materials to react and deposit glass oxides. The preform may be processed further in preparation for pulling into an optical fiber.


If you are afraid that you might die laughing you are suffering from cherophobia.

Cherry Picker

An industrial crane arranged 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.

Cherry Picking

A call center term. Calls come in and are identified in some way ” by ANI (automatic number identification), Caller ID, or caller touchtone input. The identity of the callers is known to the agents in the call center, who can now answer the callers they wish. They decide to answer those callers who they think will buy the most and presumably give them the highest commission or best reward. Thus the expression "cherry picking."

Chernobyl Packet

A network packet that induces a broadcast storm and/or network meltdown. Named after the April, 1986 nuclear accident at Chernobyl in Ukraine.

Cheyenne Mountain

The U.S, military has built a underground base inside Cheyenne Mountain, Colorado. The base is built on giant springs and is designed to withstand a Soviet ICBM attack. For 40 years it has been the home of Norad, the North American Aerospace Defense Command ”the U.S.-Canadian early warning system that scanned the globe looking for the telltale launch of an intercontinental missile. The base is a relic of the cold war, now being revived as the possible headquarters of the United States Space Force.


Concentration Highway Interface, pronounced "Ki." A user-programmable, full-duplex interface in the form of a TDM (Time Division Multiplexed) bus. CHI was developed by Lucent, and is used in ISDN controllers.


Chicago's name comes from an American Indian word meaning "place that smells bad."

Chicken Feet

Chicken feet are an extremely popular dim sum dish in Asia. Not surprisingly, they aren't popular with Americans. Simply prepared, chicken feet are cooked in a black-bean sauce. The proper way to eat them is to put the entire foot in one's mouth, suck off the meat, and spit out the bones.

Chicken Soup

During the Middle Ages, chicken soup was believed to be an aphrodisiac.


  1. Another term for a B Connector. See B Connector.

  2. IBM once came out with a PC that had small keys. The press said the PC had a chiclet keyboard, after the chewing gum.

Chief Information Officer

CIO. The person responsible for planning, choosing, buying, installing ” and ultimately taking the blame for ” a company's computer and information processing operation. Originally, CIOs were called data processing managers. Then they became Management Information System (MIS) managers. Then, CIOs. The idea of calling them CIOs was to reflect a new idea that the information they controlled was a critical corporate advantage and one that could give the company a competitive edge over its competitors ” if played correctly. See also Chief Technology Officer.

Chief Technology Officer

Once there was data processing managers. They grew up to become MIS managers ” Management Information Systems. Then they became Chief Information Officers, i.e. CIOs. The changing title was a simple and blatant attempt to improve their status (and pay) within the corporation. The latest step "up" is to call these people "Chief Technology Officers," or CTOs. And that's fair in the self-aggrandizement "progress" ” except that I believe the Chief Technology Officer is not only responsible for the company's computer and information processing but he (or she) is also responsible for figuring how to take the entire spectrum of technology and apply it to endow his/her company with one or many competitive advantages. In short, a CTO is a broader kettle of fish than the CIO. Typically, I would see the CIO reporting to the CTO.

Child Domain

Same thing as a subdomain. See Subdomain.

Child Group

In some systems, a new group of users created under a parent group is called a child group. Child groups sometimes have more properties than their parent groups.

Child Node

An ATM term. A node at the next lower level of the hierarchy which is contained in the peer group represented by the logical group node currently referenced. This could be a logical group node, or a physical node.

Child Peer Group

An ATM term. A child peer group of a peer group is any one containing a child node of a logical group node in that peer group. A child peer group of a logical group node is the one containing the child node of that logical group node.

Children's programming

Cable Television programming originally produced and broadcast primarily for an audience of children 12 years old and younger (reference: FCC Rules, 47 CFR 76.225). This rule also requires:

  • Commercial matter in children's programming carried on Origination Cablecasting channels must not exceed specified time limits.

  • The cable system must maintain, in its PIF, records ("certifications") to verify compliance with this requirement. Certifications for satellite-delivered programming must be obtained from the programmer. These requirements apply only to Origination Cablecasting. These requirements do not apply to:

  • Broadcast stations .

  • Access channel capacity designated by franchise for public, educational, or governmental use.


ITU HIgh Level Language. A computer language developed by the ITU for the standardization of software in telecommunications switches. Not widely adopted. C is more widely adopted.


An electromechanical or electronic substitute for the conventional telephone bell, that sounds like a musical chime being struck, typically in a "bing-bong" sequence.

Chimney Effect

Picture a phone system. We have an upright, rectangular cabinet full of printed circuit cards and all getting hot. How to cool them? Simple, raise the machine a little off the ground, put holes in the bottom of the cabinet and holes in the top of the cabinet. Hot air rises. Bingo, air will rise through the top of the cabinet and cool air will get sucked in the bottom of the cabinet. And bingo, you don't need a fan. This natural cooling technique is called the Chimney Effect and many modern phone systems now use it.

Chimney Mount

A mounting system used for attaching an antenna mast to a brick chimney.

Chinese Wall

A "Chinese Wall" refers to barriers to the flow of information that are designed to prevent the misuse of material nonpublic information (that is, to prevent "insider trading" and other abuses ). Brokers , dealers and investment advisers are required by law to have "Chinese Walls" in place, although that term itself does not appear in the statutes. The reason they are required to have such barriers is that they frequently have access to material nonpublic information in one part of the firm that cannot legally be used by other parts of the firm. For example, a broker dealer's investment bank may be advising Client X on a merger at the same time the research department is writing research and the trading department trades X's common stock. With an effective "Chinese Wall" in place, the broker dealer can do all three. Without it, the firm's activities must be limited.

The SEC and other regulators have provided guidance on what is required for a "Chinese Wall" in this context. These include physical barriers and security measures, review of employee and proprietary trading, memorailization and documentation of firm procedures, substantive supervision of inter-departmental communications by the firm's Compliance/Legal Department and procedures concerning proprietary trading when the firm is in possession of material nonpublic information.

The term "Chinese Wall" is also used more generically to refer to the policies and procedures that public companies put in place to prevent the misuse of inside information about the company by its employees and agents. That aspect of "Chinese Walls" stems from securities law requirements separate from the specific provisions that apply to regulated entities (brokers, dealers, investment advisors). As with regulated entities, there are a number of ways public companies erect "Chinese Walls." These include providing access to material nonpublic information only to a relatively few employees, requiring employees to "pre-clear" trades in the company's stock, blackout periods (designated times when employees are not permitted to trade the company's securities) and physical barriers and security measures.


  1. An integrated circuit. The physical structure upon which integrated circuits are fabricated as components of telephone systems, computers, memory systems, etc. Typically a chip refers to an integrated circuit that has been "packaged" in insulating plastic. The plastic casing traditionally has protruding metal pins that are used to connect with other chips to per-form specific functions. Examples include microprocessors and DRAMs.

  2. The transition time for individual bits in the pseudo-random sequence transmitted by the GPS satellite.

  3. A term used in wireless transmission. In the IEEE 802.11b standard for WLANs (Wireless Local Area Networks), for example, each bit is encoded into an 11-bit Barker code, with each resulting data object forming a "chip." The resulting chips are placed on a RF (Radio Frequency) carrier for transmission.

Chip Head

Anyone whose education, entertainment and employment is primarily derived from computer-based devices. Also called a Bit Head.

Chip Jewelry

A Wired Magazine definition: Chip Jewelry is a euphemism for old computers destined to be scrapped or turned into decorative ornaments. "I paid three grand for that Mac SE, and now it's nothing but chip jewelry."

Chip Rate

Also known as the spreading rate. The rate at which radio signals are spread across a range of frequencies in a spread spectrum transmission system. See also Spread Spectrum.

Chipless RFID tag

An RFID tag that doesn't depend on an integrated microchip. Instead, the tag uses materials that reflect back a portion of the radio waves beamed at them. A computer takes a snapshot of the waves beamed back and uses it like a fingerprint to identify the object with the tag. Companies are experimenting with embedding RF reflecting fibers in paper to prevent unauthorized photocopying of certain documents. But chipless tags are not useful in the supply chain, because even though they are inexpensive, they can't communicate a unique serial number that can be stored in a database.


  1. A rapid change (as opposed to a long-term drift ) of the wavelength of an electromagnetic wave. Chirping is most often observed in pulsed operation of a source.

  2. A pulse compression technique that uses (usually linear) frequency modulation during the pulse.

Choice Chip

Your new TV will come with electronics that will allow you to program it not to receive certain programs, e.g. violent ones, you choose not to receive. The idea is that shows will be rated. Before they start, the show will broadcast a digital signal containing its rating. The "choice" chip in your TV will recognize the rating, check it against your instructions and block it or allow it through. The "choice" chip is so named as to give parents a choice of programs they and their children will watch. The provision for a choice chip was contained in telecommunications reform legislation passed by the Senate in mid- 1995.


An obsolete term: An inductance with either an air or iron core , designed to retard certain frequencies; as a radio frequency choke or an audio frequency choke. See also Choke Exchange.

Choke Exchange

A telephone exchange or central office which is assigned to Radio and TV stations, Promoters, and other users which receive large numbers of simultaneous calls. The idea is to group all of these users on a single exchange so when all routes into that exchange are in use, "normal" users (on other exchanges) will not experience blocking of their incoming or outgoing calls. Trunks from other local exchanges into the choke exchange are deliberately limited to just a few paths so callers will get an "all trunks busy" instead of completely blocking their local exchange. However, when one of the choke exchange users experiences a large number of calls (as when your favorite radio station runs a contest) the other choke exchange users will be blocked because all trunks into the choke exchange will be busy due to the first user. See Blocking and Concentration.

Choke Coil

A coil so wound as to offer a retarding or self inductance effect to an alternating current.

Choke Exchange

A telephone exchange which is assigned to Radio and TV stations, Promoters, and other users which will be receiving large numbers of simultaneous calls. The idea is to group all of these users on a single exchange so when all routes into that exchange are in use, "normal" users (on other exchanges) will not experience blocking of incoming or outgoing calls. However, when one of the choke exchange users experiences a large number of calls (as when your favorite radio station runs a contest) the other choke exchange users will be blocked because all trunks into the choke exchange will be busy. See Blocking and Concentration.

Choke Packet

Packet used for flow control. The node detecting congestion generates the choke packet and sends it toward the source of congestion, which is required to reduce input rate.

Choke Point

See Infiniband.


A desk accessory on the Apple Macintosh that allows a user to choose items such as a printer or file server by clicking on an icon of the device.


A device for rapidly opening and closing a circuit. An ancient radio term.


This is a less-than -optimum circumstance in which a caller's words are intermittently cut off, creating gaps in the voice transmission. This is usually the result of packet loss when transmitting voice over a packet-switched data network. Choppiness makes it difficult or impossible to have a normal conversation.

Christmas Tree Lights

The first electric Christmas lights were created by a telephone company PBX installer. Back in the old days, candles were used to decorate Christmas trees. This was obviously very dangerous. Telephone employees are trained to be safety conscious. The installer took the lights from an old switchboard, connected them together, strung them on the tree, and hooked them to a battery. Then he spent the next 40 years looking for the one burnt bulb...


The level of saturation or intensity of a color. Name sometimes applied to color intensity control in a receiver.

Chroma Key

Method of electronically inserting the image from one video source into the picture from another video source using color for discrimination. A selected "key color" is replaced by the background image.

Chromatic Dispersion

Chromatic dispersion is a characteristic of all optical fibers, caused by the fact that different wavelengths of light travel at different velocities in glass. A prism is a demonstration of this phenomenon , for example. Optical fibers can be designed to control the dispersion profile versus wavelength. The amount of chromatic dispersion is a measure of the relative velocity of light (photons) in adjacent wavelengths in the fiber. High dispersion means that light ( photons ) at a given wavelength is traveling down the fiber at a very different speed than light in a wavelength right next door. Low dispersion means that light in adjacent wavelengths is traveling down the fiber at about the same velocity. It is important in multi-wavelength systems to have enough dispersion to break up cross wavelength interference problems but not so much dispersion that high bit rates become costly to transmit. Some fibers are designed to have nonzero-dispersion, i.e. they must have just the right amount of dispersion to balance these effects.

The uniformity of dispersion relates to how the amount of dispersion varies across a range of wavelengths. If you plotted the dispersion value at each wavelength across a range of wavelengths and they all had exactly the same amount of dispersion, the slope of the plotted line would be zero. To get optimum performance and cost in multi-wave- length transmission systems, it is important that the amount of dispersion not vary too much across the different wavelengths used by the system.

Chromatic dispersion is one of the mechanisms that limits the bandwidth of optical fibers by producing pulse spreading because of the various colors of light traveling in the fiber. Different wavelengths of light travel at different speeds. Since most optical sources emit light containing a range of wavelengths, each of these wavelengths arrive at different times and thereby cause the transmitted pulse to spread as it travels down the fiber.

Chromatic dispersion is the sum of material and waveguide dispersion. Dispersion can be positive or negative because it measures the change in the refractive index with wavelength. Thus, the total chromatic dispersion can actually be zero (really close to zero). For example, step-index single-mode fibers have zero dispersion at 1300nm, almost exactly at the same wavelength where the optical loss of the fiber is at a minimum. This is what allows single-mode fibers to have low loss and high bandwidth. See also PMD (Polarization Mode Dispersion).


The color portion of the video signal. Chrominance includes hue and saturation information but not brightness. Low chroma means the color picture looks pale or washed out; high chroma means the color is too intense , with a tendency to bleed into surrounding areas. Black, gray and white have a chrominance value of O. Brightness is referred to as luminance.

Chromium Dioxide

Tape whose coating is of chromium dioxide particles. Noted for its superior frequency output.

Chronic Service Deficiency

When you work a delay with a service provider ” a telephone or data carrier, you need to create certain definitions of service so that you can figure penalties if such levels of service are not maintained. For example, we might define service deficiency as being a service outage lasting for more than ten seconds. We might define Repeated Service Deficiency as a service deficiency that occurs at least four times in any given 30 day period. and we might define Chronic Service Deficiency as a service deficiency that occurs more than ten times in any given 30 day period. Of course, how these terms are defined will depend on the SLA ” Service Level Agreement ” which you sign with your carrier.


Cylinder-Head Sector. The method of identifying a given location on a hard drive used by the original PC-AT BIOS (INT 13) and original IDE specification. Differences between details of the two methods resulted in the 528 MB limit on IDE drives . Enhanced IDE-com- pliant BIOSes can translate between the two methods, allowing drive sizes up to 8.4 GB. See Enhanced IDE and IDE.

Chuck Hole

Also known as Pot Hole. Slang for when your system hangs up on-line.


Cellular phone and beeper users drop their monthly subscriptions often. Long distance users change their preferred carrier as often as they change their underwear. DSL customers switch to cable modem providers. The industry calls this phenomenon "churn." And it's very expensive. Churn is defined as the level of disconnects from service relative to the total subscriber base of the system. Often referred to on a percentage basis monthly, quarterly or annually. Sometimes it's as high as 2% or 3% or even 4% a month. It drives the cellular, beeper and long distance business nuts. It's very expensive to sign up a new customer. Many cell, beeper and long distance companies offer incentives to prospective customers to switch their service. Sometimes you have to stay a customer for months and months for your supplier to recoup his sign-up incentive Some users have found ways to switch their long distance service often enough so that they never pay for a long distance phone call. The only solution to "churn" is to develop a close and binding relationship with the customer. This is not easy. And most telecom companies haven't figured it.

Churn Rate

Monthly cancellation rate of subscribers as a percentage of total subscribers. This is a metric used for service companies (such as cell phone companies, Internet service providers, and CLECs) as an indication of how successful they are at retaining customers.


Chutpah is a Jewish word that means unmitigated gall. The word is typically explained by the story of the 15-year old who goes into court having killed his father and mother and falls on the mercy of the court now that he's an orphan.


  1. Customer Interface.

  2. Certified Integrator.

  3. An ATM term. Congestion Indicator: This is a field in a RM-cell, and is used to cause the source to decrease its ACR. The source sets CI=0 when it sends an RM-cell. Setting CI=1 is typically how destinations indicate that EFCI has been received on a previous data cell.


Cellular Intercarrier Billing Exchange Record. A billing record format used between cellular carriers.


  1. See Carrier Identification Code.

  2. See Circuit Identification Code.


Customer Information Control System. An IBM program environment designed to allow transactions entered at remote computers to be processed concurrently by a mainframe host. Also, IBM's Customer Information Control System software.


  1. A generic term in Britain to identify a customer identity, client identity or contract identity. It is a single record and all the fields of information associated with it; for example, name, address, phone number, contact history and so on.

  2. Compatibility ID. Motorola definition.

  3. CIrcuit Designator.

  4. Caller Identification or Caller ID.


Calling Line Identification Delivery Blocking. A "feature" of central offices which lets you block the sending of your phone number to the person you're calling.


CID on Call Waiting. See Caller ID Message Format.


Classless Inter-Domain Routing. An internetworking routing protocol. It is a way of using the existing 32-bit Internet address space more efficiently commonly used by Internet Service Providers. It allows the assignment of Class C IP addresses in multiple contiguous blocks. CIDR solved a major problem with IP address assignment. Specifically, IPv4 addresses in the Class C block were limited to 254 addresses. If a user required more than 254 addresses, the next step up the IP food chain was Class B, with 65,534 addresses. Clearly, this was wasteful , as only a few more addresses required a huge chunk of precious addresses. Although this was not an issue for the first two decades of IP, the recent popularity of the Internet (and other IP networks) quickly strained the existing IPv4 addressing scheme. The backbone routers driving much of the Internet traffic in the early 1990s had to track every Class A, B and C network, at times creating routing tables that were 10,000 entries long. The maximum theoretical routing table size is roughly set at 60,000 entries. If the Internet community didn't act fast, it was estimated that the Internet would reach maximum by 1994. CIDR came to the rescue...and will continue to do so, even with the advent of IPv6. CIDR replaces Class A, B and C addresses with a "network prefix" that indicates the number of bits used for identifying the network. Prefixes range from 13 to 27 bits, instead of the eight, 16 or 24 bits of class-based addresses. This means that address blocks can be assigned in groups as small as 32 hosts or as large as over 500,000 hosts. CIDR builds on the concept of "supernetting," with more than one block of network addresses being linked together logically into a "supernet." The problem of IP address exhaustion is similar to, but much more complex than, that of 800 numbers, which was relieved with the introduction of 888, and the 877, numbers. CIDR requires the use of routing protocols that support it, examples being RIP (Routing Information Protocol) Version 2, OSPF (Open Shortest Path First) Version 2, and BGP (Border Gateway Protocol) Version 4. See also IP, IPv4, IPv6, and TCP/IP.


  1. Common Intermediate Format. An option of the ITU-T's H.261/Px64 standard for videoconferencing codes. It produces a color image of 288 non-interlaced luminance lines, each containing 352 pixels to be sent at a rate of 30 frames per second. The format uses two B channels, with voice taking 32 Kbps and the rest for video. QCIF (Quarter CIF), is a variation on the theme, requiring approximately 1/4 the bandwidth of CIF and delivering approximately 1/4 the resolution. CIF works well for large-screen videoconferencing, due to its greater resolution; QCIF works well for small-screen displays, such as videophones. QCIF is mandatory for ITU-T H.261-compliant codes, while CIF is optional. See QCIF.

  2. Cost, Insurance and Freight are included. That means the seller pays the freight. The opposite of CIF is FOB, which stands for Free On Board. What this means is that you buy something, F.O.B. The seller puts it on a truck or railroad , plane, i.e. some carrier. He's responsible for getting it on the carrier. You ” the buyer ” are responsible for paying for the cost of the freight of getting you the goods you ordered.

  3. Cells In Flight: An ATM term for an ABR (Available Bit Rate) service parameter, CIF is the negotiated number of cells that the network would like to limit the source to sending during the idle startup period, before the first RM-cell returns.

  4. Cells In Frames. Referring to ATM over Ethernet (or Token Ring), CIF involves the insertion of one or more ATM cells into Ethernet frames for transport over an Ethernet LAN. CIF allows the user organization to maintain the existing Ethernet wiring, NICs (Network Interface Cards) and other hardware to support ATM applications. The drawback is that CIF must be used in a switched Ethernet environment in order to maintain ATM QoS (Quality of Service) commitments. Additionally, the SAR (Segmentation and Reassembly) process must be accomplished in software at the workstation, which is slow unless the workstation is really fast. CIF is something of a band-aid approach to bridge the gap until such time as ATM really takes hold in the LAN world.


Cells In Frames-Attachment Device. The device which attaches the CIF-ES to the ATM network.


Cells In Frames-End Station. An Ethernet- or Token Ring-attached workstation which supports CIF.


Common Internet File System. A remote collaborative file sharing technology that, according to Microsoft, dramatically reduces the time it takes to open and work with remote files. Data General, Digital Equipment, Intel, Intergraph Corp, Network Alliance and Microsoft announced support for CIFS in June 13, 1996. According to Microsoft, the Common Internet File System is an enhanced version of the native file-sharing technology used in the Microsoft MS-DOS, Windows and Windows NT operating systems and IBM OS/2, and widely available on leading UNIX systems. It enables millions of computer users to open and share remote files directly on the Internet, expanding the Internet's ability to support interactive computing. CIFS technology provides reliable direct read and write access to files stored on remote computers without first requiring users to download or copy the files to a local machine, as done previously on the Internet. According to Microsoft's June 13 release, CIFS can improve the performance of many types of file access. Because CIFS is based on existing standards, users will be able to use thousands of existing applications over the Internet as well as integrate them with browser applications designed for the World Wide Web.

The proposed Common Internet File System protocol runs over TCP/IP and is an enhanced version of the open, cross-platform protocol for distributed file sharing called Server Message Block (SMB). The SMB protocol is the standard way that millions of PC users already share files across corporate intranets and is the native file-sharing protocol in Windows 95, Windows NT and OS/2.

The proposed Common Internet File System protocol has been enhanced over previous versions of the SMB protocol in ways that make it well suited for use on the Internet. CIFS, for example, supports the Internet's Domain Name Service (DNS) for address resolution. The protocol runs optimally over slow-speed dial-up lines, helping improve performance for the vast numbers of users today who access the Internet using a modem. In addition to remote file sharing, CIFS has mechanisms to support remote printer sharing.


CallInG subscriber identification. A frame that gives the caller's telephone number. See Caller ID.


Canadian Interest Group on Open Systems. Canadian organization which promotes OSI.


Common Interest Group on Rating and Routing.


Caller Issue Identifier Card. A calling card issued by an RBOC.


Canadian ISDN Interest Group. Canadian organization which promotes ISDN.


  1. Computer-Integrated Manufacturing.

  2. Common Information Model. CIM is the DMTF's model for describing management information to work with disparate systems.


See Customer Identification Number.


A tightening , or increase in pressure in which something becomes more difficult to undo, or becomes locked up. This effect is sometimes seen in 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, slips and becomes very tightly packed.

Cincinnati Bell

One of the "original" LECs (Local Exchange Carriers) that once was part of the Bell System. While AT&T owned some stock in Cincinnati Bell, it was not wholly owned. Therefore, it was not limited by the Divestiture Decree that broke up the Bell System in 1984. So, Cincinnati Bell became Cincinnati Bell Inc., which started and acquired all sorts of interesting businesses. In 1999, the company was acquired by IXC Communications, an IXC (Interexchange Carrier). The merged company changed its name to BroadWing Inc. in 2000. Cincinnati Bell continues to operate as a LEC division of BroadWing. See BroadWing.


See Chief Technology Officer.


  1. Carrier Identification Parameter. An SS7 term. A 3 or 4 digit code in the initial address message identifying the carrier to be used for the connection. See SS7.

  2. Channel Interface Processor. A Cisco term. Channel attachment interface for Cisco 7000 series routers. The CIP is used to connect a host mainframe to a control unit, eliminating the need for an FEP for channel attachment.


A means of transforming, or encrypting, data in order to disguise its meaning. Block ciphers, such as DES, are encryption algorithms which encrypt specific blocks of data. Stream ciphers, such as the RC4 algorithm from RSA Data Security, encrypt a steady flow of data. See also Encryption.

Cipher text

The unreadable form of an original plain text message after it has been encrypted. Also spelled Ciphertext. See also Ciphertext.


The result of processing plaintext (unencrypted information) through an encryption algorithm. Ciphertext is thus the content of an encrypted message. See Clipper Chip.


  1. Committed Information Rate. A Frame Relay term. This is a long explanation, so put this book down for a minute, put the kids to bed, get yourself a cup of coffee, make yourself comfortable, and read this several times until it sinks in. Sorry for the length. But we've worked on this a lot. Ready? Here goes.

    When you subscribe to Frame Relay service through a public Frame Relay service provider, you identify the sites that you want to interconnect. Between each of those sites and based on agreement with the Frame Relay service provider (i.e., carrier), you typically establish a PVC (Permanent Virtual Circuit), which is a permanently identified path across which all data will flow between those sites. Each PVC has associated with it a CIR (Committed Information Rate). The CIR is the level of data traffic (in bits) which the carrier agrees to handle over a period of time ” not at every instant of time, but averaged over a period. The CIR can be anywhere between 0% and 100% of the speed of the access line (e.g., a 56 Kbps circuit, or a T-1 circuit at 1.544 Mbps) and the speed of the port on the device (typically a router) to which you connect at the edge of the service provider's Frame Relay network. The Offered Load to the network can burst above the CIR for a measured interval of time (T). The Offered Load can never exceed the speed of the circuit, and it can never (usually never, but that's a long story) exceed the speed of the port. Burst levels are measured as Bc and Be. Bc (Committed Burst Size) is the maximum amount of data, measured in bits, that the carrier agrees to transfer under normal circumstances. Be (Excess Burst Size) is the maximum amount of additional data, measured in bits, that the carrier will attempt to handle, assuming that congestion conditions in the network permit. All the data bits are contained within Frame Relay frames, of course. The excess frames at the Be level will be marked as DE (Discard Eligible), either by the user's Frame Relay Access Device (FRAD) or by the carrier's FRND (Frame Relay Network Device). Both the FRAD and the FRND typically are routers. The FRAD is your router. The FRND is the carrier's router that sits at the edge of the carrier network. The FRAD connects to the port of the FRND over an access circuit. Through a mechanism known as Graceful Discard (GD), the DE frames which fall within the Be will be discarded gracefully (i.e., only when absolutely necessary) by the carrier somewhere in the network during periods of congestion. If the network is not congested, the carrier will deliver the excess frames and bits. Any bits (in frames) above the Bc+Be will be discarded, usually at the point of network ingress-and not very gracefully, I might add. For example, you might have a bunch of LANs at each site. At each site, the LANs connect to a FRAD, in the form of a Frame Relay-capable router. Each router connects to the public Frame Relay network over a 56 Kbps circuit which terminates in a 56 Kbps port on the carrier's closest FRND. As each PVC has a CIR of 32 Kbps, you be pretty sure that you can transfer data at 32 Kbps, at least on the average over a period of time (e.g., a month). You also can burst above the CIR to the level of the Bc (Committed Burst Size), and with reasonable assurance that the data will get to the destination site. You can burst above the Bc, although all bits in the Be (Excess Burst Size) are subject to being marked DE (Discard Eligible). The DE bits wind up on the switchroom floor in the event that the network is congested and the buffers in the network switches and routers overflow. You also can transmit above the total of the Bc+Be, but those bits in those frames may wind up on the switchroom floor at the ingress FRND. See also Committed Burst Size, Discard Eligible, Excess Burst Size, FRAD, Frame Relay, FRND, Graceful Discard, Measurement Interval, Offered Load, Permanent Virtual Circuit, and Router.

  2. An ATM term. Committed Information Range: CIR is the information transfer rate which a network offering frame relay services (FRS) is committed to transfer under normal conditions. The rate is averaged over a minimum increment of time.

Circling the drain

When you're kept working on a project that is going nowhere but refuses to die, it's circling the drain.


A circuit is a connection or line between two points. The connection can be made through various media, including copper, coaxial cable, fiber, or radiowave. A dedicated circuit is, as it sounds, a link that is dedicated to the two entities at either end. Dedication is expensive because it does not use the network as efficiently as i could. If A. B, C, and D all need to be connected with dedicated lines, then a total of six separate links are needed to connect them. Instead, a central switch to which each is connected reduces the number of links required to four. This difference in efficiency increases exponentially as the number of users increases.

Circuit Board

Same as a Printed Circuit Board, namely a board with microprocessors, transistors and other small electronics components. Such a board slides into a slot in a telephone system or personal computer. Also called a circuit card.

Circuit Breaker

A special type of switch arranged to open a circuit when overloaded, without injury to itself. A circuit breaker is basically a re-usable fuse. According to APC, a circuit breaker is a protective device that interrupts the flow of current when the current exceeds a specified value. Circuit breakers are calibrated when manufactured to a specific overcurrent value. Building or equipment wiring may overheat and become a fire hazard if excessive current is passed through such wiring. Circuit breakers or fuses are installed and coordinated with wiring by selecting the appropriate trip value so that if equipment malfunction or user error causes too much current to flow through a wire, the circuit breaker will trip to prevent the wire from overheating . For building wiring and power distribution, the values of circuit panel breakers are specified in America by the National Electrical Code.

Circuit Card

Same as a Circuit Board. See Circuit Board.

Circuit Conditioning

Modification of (most typically) analog data circuits to bring transmission parameters of the channel into narrower limits than provided by randomly-selected voice channels. Conditioning is also used to a lesser extent in certain other services. See Load Coil.

Circuit Emulation

A connection over a virtual channel-based network providing service to the end user that is indistinguishable from a real, point-to-point, fixed bandwidth circuit.

Circuit Emulation Switching

CES. Part of the ATM Forum's proposed Service Aspects and Applications (SAA) standard.

Circuit End

The local channel termination needed to connect the customer's location to the carrier's POP.

Circuit Grooming

The practice of directing selected circuit-switched DS-0s (64 kbit/s channels) from many T-1 trunks into a single T-1 (typical application is voice leased lines from a T-1 access line being 'groomed' in a DACS onto a dozen or more T-1s going to other central offices where those channels may again be groomed with other circuits onto T-1 access lines at those sites). Also used to separate voice circuits from data circuits, and for combining them for delivery to service-specific switches in the CO.

Circuit Identification Code

CIC. The part of a CCS/SS7 signaling message used to identify the circuit that is being established between two signaling points (14 bits in the ISDNUP).

Circuit Level Gateway

A circuit level gateway ensures that a trusted client and an untrusted host have no direct contact. A circuit level gateway accepts a trusted client's requests for specific services and, after verifying the legitimacy of a requested session, establishes a connection with an untrusted host. After the connection is established, a circuit-level gateway copies packets back and forth-without further filtering them.

Circuit Level Proxy

A firewall technology that involves examining transmitted data for certain types of improper or threatening behaviour without taking into account the specifics of the application involved; SOCKS is a common example of a circuit-level proxy. See SOCKS.

Circuit Mode

  1. An AT&T term for the method of communications in which a fixed bandwidth circuit is established from point to point through a network and held for the duration of a telephone call.

  2. An AIN term for a type of switching that causes a one-to-one correspondence between a call and a circuit. That is, a circuit or path is assigned for a call between each switching node, and the circuit or path is not shared with other calls.

Circuit Noise Level

At any point in a transmission system, the ratio of the circuit noise at that point to some arbitrary amount of circuit noise chosen as a reference.

Circuit Order Management System

COMS. An automated processing system of MCI circuit- and service-related information. Processes hardwire service circuit orders from order entry through scheduling and completion. COMS also provides circuit order data, hardwire customer data, and circuit inventory data to other MCI systems in Finance, Engineering, and Operations.

Circuit Order Record

COR. Report generated by the COR Tracking System within NOBIS, indicating circuit installations, changes, and disconnects.

Circuit Provisioning

The telephone operating company process that somehow organizes to get you a trunk or other special service circuit.

Circuit Segregation

Differentiating between services that are maintained by separate technicians or departments. Can be accomplished through visual and/or mechanical means.

Circuit Switched Digital Capability

CSDC. A service implemented by some regional Bell Operating Companies that offers users a 56 Kbps digital service on a user-switchable basis. See Circuit Switching.

Circuit Switched Network

A network that establishes a physical circuit temporarily on demand (typically when telephone or other connected device goes off hook) and keeps that circuit reserved fo the user until it receives a disconnect signal.

Circuit Switching

Imagine making a phone call to Grandma. You pick up the phone and dial Grandma. When you finish dialing, the various telephone company switches along the way pick a path for your call and move your call along its way to Grandma. When Grandma answers, you and she are now able to speak. Both of you now have the exclusive and full use of the circuit that was set up between you. You have that circuit until you (or she) hang up, at which time it goes idle until the system of switches grabs it for another "call." That call might be voice, data and video. Circuit switching has one big advantage: You get the full circuit for the full amount of the time you're using it. And for the most part, it's full duplex. Circuit switching has one big disadvantage. Because you get the full circuit for the full amount of the time, you pay for the privilege of tying up that circuit (no one else can use it, even when there are pauses in your conversation). Which means it's expensive.

There are basically three types of switching ” circuit, packet and message: Circuit Switching, which I just explained, is like having your own railroad track for your conversation to travel on. It's yours for as long as you keep the connection open. No one else can use it. Once you hang up, the next caller gets to use that track. Virtually all voice telephone calls are circuit switched, though that won't be true in the future. All dial-up modem calls are circuit switched also.

Packet Switching is like having your own railroad cars which you're sharing with other railroad cars on a railroad track. You slice the information you want to send so it fits into the cars, which join other cars to travel on the railroad track to the other end. You get pretty well as many railroad cars as you need. They will travel on different railroad tracks until they reach the station at the other end, where they'll be assembled in the order you sent them and then dropped off at your destination. Packet switching was originally created for sending data, since it's very efficient (and therefore cheap). One railroad track gets to carry a lot of "conversations." In circuit switching, it only carries one conversation. Packet switching does have the problem that it takes a little time to break up the data "conversations" into many packets, send them on their different ways and then reassemble them at the other end. For data, that delay is barely noticeable. It can be noticeable in a voice conversation, which is why packet switching hasn't been used much for voice ” until recently. (See IP Telephony.) In packet switching, the addresses on your packets are read by the switches as they approach, and are switched down the tracks. The next packet is read to throw the switches to send that packet where it needs to go. The data conversation is sent in packets. Each packet can be sent along different tracks as they are open. The packets are assembled at the other end ” typically in the last switching office before the packets reach the distant computer or distant user.

Message Switching sends a message from one end to the other. But it's not interactive, as in packet or circuit switching. Of course, you can reply. But it's not like having a "conversation." In message switching, the message is typically received in one block, stored in one central place, then retrieved or sent in one clump to the other end. Message switching is like the post office, or like email. It can be slow. But it can also be cheap.

Message Switching can use a combination of circuit switching and packet switching to get its message through.

Circuit, Four Wire

A path in which four wires are presented to the terminal equipment (phone or data), thus allowing for simultaneous transmission and reception. Two wires are used for transmission in one direction and two in the other direction.

Circular Antenna

A horizontally polarized, half-wave dipole antenna formed into the shape of a circle except that the terminating ends do not touch to make a continuous loop.

Circular Extension Network

Permits two or more single-line phones connected to a PBX, each with its own extension, to operate like a "square" key telephone system. An incoming call directed to any non-busy phone in the group will ring at all of the non-busy phones. The first extension to answer will be connected to the incoming call. At any time, a non-busy extension can make or receive calls.

Circular Hunting

When calling a phone, the switching system makes a complete search of all numbers within the hunting group, regardless of the location within that group of the called number. For example, the hunt group is 231, 232, 233 and 234, the call is directed to 233. If it is busy, the equipment will search 234, 231, and 232 to find a non- busy phone or line. Essentially it goes around the ring, remembering where it last connected and then goes to the next line or phone in the circle. See also Hunt Group and Terminated Hunt Group.

Circular Mil

The measure of sectional area of a wire.

Circular Polarization

In electromagnetic wave propagation, polarization such that the tip of the electric field vector describes a circle in any fixed plane intersecting, and normal to, the direction of propagation. The magnitude of the electric field vector is constant. A circularly polarized wave may be resolved into two linearly polarized waves in phase quadrature with their planes of polarization at right angles to each other.


  1. In networking, a passive junction of three or more ports in which the ports can be accessed in such an order that when power is fed into any port it is transferred to the next port, the port counted as following the last in order.

  2. In radar, a device that switches the antenna alternately between the transmitter and receiver.


A type of headphone that almost totally isolates the listener from room sounds.


Contact Image Sensor. A type of scanner technology in which the photodetectors come in contact with the original document.


Complex Instruction Set Computing. PC Magazine defines CISC as a microprocessor architecture that favors robustness of the instruction set over the speed with which individual instructions are executed. The Intel 486 and Pentium are both examples of CISC microprocessors. See also RISC ” Reduced Instruction Set Computing. See RISC.

Cisco IOS

Internetwork Operating System. An OS incorporated as part of the CiscoFusion architecture designed to provide centralized integrated, automated installation and management of Internet and intranet networks.


This is a European Community standard specifying the limits of radio frequency emissions which appliances and other electrical equipment are allowed. The standard indicates the maximum allowable emissions either radiated or conducted via the power cord at various frequencies. Some countries still use the older VDE 0871 emission standards, which are nearly identical. In the USA, the FCC has a similar standard.


Computer Integrated Telephone is Digital Equipment Company's program, announced in October 1987, that provides a framework for functionally integrating voice and data in an applications environment so that the telephone and terminal on the desktop can be synchronized, the call arriving as the terminal's screen on the caller arrives. CIT uses the DEC VAX line of computers. According to DEC, CIT supports both inbound and outbound telecommunications applications. In an inbound scenario, the application may recognize the caller's originating phone number through Automatic Number Identification (ANI) and/or the dialed number through Dialed Number Identification Service (DNIS), match the information to corresponding data base records and automatically deliver the call and the data to the call center agent. In an outbound application, dialing can be automated, increasing the number of connected calls. In either scenario, the telephone calls and associated data can be simultaneously transferred to alternate locations within an organization, adding a new level of customer service to call center applications. Digital made its first CIT announcements at Telecom '87 in Geneva, Switzerland. The CIT product set, consisting of client and server software implementing a variety of switch-to-computer link protocols, and providing a robust applications interface, was first shipped in 1989. The company announced its latest release, CIT Version 2.1, in January 1991. See also Open Application Interface.

Citizens Band

One of two bands used for low power radio transmissions in the United States ” either 26.965 to 27.225 megahertz or 462.55 to 469.95 megahertz . The Citizens Band Radio Service is an HF two-way voice communication service for use in your personal and business activities. Expect a communication range of one to five miles. Operation is authorized by rule. Citizens band radio is not allowed in many countries, even some civilized countries. In some countries they use different frequencies. CB radios, in the United States, are limited by FCC rule to four WATTS of power, which gives each CB radio a range of several miles. Some naughty people boost their CBs with external power. The author of this dictionary has actually spoken to Australia while driving on the Santa Monica Freeway in Los Angeles. See also CB and Citizens Band Radio Service.


Cell Interarrival Variation. An ATM term. See Cell Interarrival Variation.


Collaboration for Interactive Visual Distance Learning. A collaborative effort by 10 US universities that uses dial-up videoconferencing technology for the delivery of engineering programs.


  1. Commercial Internet Exchange. Pronounced "kicks." As the Internet began to be commercialized, an agreement was reached among a number of commercial network providers that allowed them to exchange traffic. The first CIX router was installed in the Wiltel equipment room in Santa Clara, California. The Santa Clara CIX and that in Herndon, Virginia remain operational, although the CIX concept later gave way to that of the NAP (Network Access Point). See also FIX, MAE and NAP.

  2. Commercial Internet eXchange Association. A non-profit trade association of Public Data Internetwork service providers that promotes and encourages development of the public data communications internetworking services industry, nationally and internationally. The CIX states that it provides a "neutral forum to exchange ideas, information, and experimental projects among suppliers of internetworking services...Together, the membership may develop consensus positions on legislative and policy issues of mutual interest." www.cix.org.


Circuit Location.


Circuit Reference. The access service tariff customer's overall circuit name.




ConnectionLess. A service which allows the transfer of information across a network without the need for the establishment of a defined path for the data to travel. IP (Internet Protocol) is a connectionless protocol, as the individual data packets travel across the network, from edge-to-edge, over the path of least resistance. IP packets work their way across a network on the basis of link-by-link forwarding, with each link selected solely on the basis of its availability. Therefore, each packet may travel a different path. TCP is a connection-oriented which ensures that a pre-defined path is set up across the network, from edge-to-edge. TCP runs on top of IP, which is the lowest common denominator protocol in the TCP/IP protocol suite. UDP is a connectionless protocol which can be used in place of TCP. Like TCP, UDP provides reliability of data transfer, with error control being the responsibility of the application program, rather than the network switches and routers. See also Connection-Oriented, IP, TCP, and UDP.


  1. The transparent material, usually glass, that surrounds the core of an optical fiber. Cladding glass has a lower refractive index than core glass. As the light signal travels down the central core transmission path, it naturally spreads out due to a phenomenon known as "modal dispersion." The cladding causes the light to be reflected back into the central core, thereby serving to maintain the signal strength over a long distance. See Cladding Diameter.

  2. When referring to a metallic cable, a process of covering with a metal (usually achieved by pressure rolling, extruding, drawing, or swaging) until a bond is achieved.

Cladding Beam

In fiber optics transmission, a beam that transmits within the core and cladding layers by being reflected off the edge surface of the cladding glass. See Cladding Mode.

Cladding Diameter

The diameter of the circle that includes the cladding layer in an optical fiber.

Cladding Glass

A type of glass or other transparent material used in fiber optic cables which has a lower refractive index than the glass used in the core.

Cladding Mode

In an optical fiber, a transmission mode supported by the cladding; i.e., a mode in addition to the modes supported by the core material.

Cladding Mode Stripper

A device for converting optical fiber cladding modes to radiation modes; as a result, the cladding modes are removed from the fiber. Often a material such as the fiber coating or jacket having a refractive index equal to or greater than that of the fiber cladding will perform this function.

Cladding Ray

In an optical fiber, a ray that is confined to the core and cladding by virtue of reflection from the outer surface of the cladding. Cladding rays correspond to cladding modes in the terminology of mode descriptors.


I got this from Verizon's dictionary. Claim is a report to Verizon that describes what the customer believes to be an incorrect charge. Claims may be made for recurring charges, non-recurring charges and usage; they may be general or individual. Verizon also has something called Claims Input File, which is a file format through which claims are submitted electronically to Verizon.

Claim Process

A technique used to determine which station will initialize an FDDI ring.

Claim token

A token ring frame that initiates an election process for a new active monitor station. Claim tokening can result from expired timers, or from any other condition that causes any station to suspect a problem with the current active monitor.


Harry Newton's favorite daughter. Why "favorite?" Simple. She's his only daughter . Her full name is Claire Elizabeth Newton. "Claire" is a form of "Clare," which means "clear" or "bright" from the Latin "clarus." True to her name, she's both clear and bright. Brilliant naming, if I might say so. Her mother chose the name, Claire. I didn't want it. My dumb idea was to choose a name that six randomly-dialed telephone operators could spell correctly. Not one spelled Claire correctly. But, by then the name had stuck. Her mother insisted on it. In early 2004, Claire was 24 going on 35. Two years ago she graduated from Bowdoin College, magna cum laude and phi beta kappa. Graduation should have been a respite for me. But she has announced her intention to go to law school. Hence, I am now facing $40,000 bills for the next millennium or two. Fortunately she recognizes that the world doesn't need another lawyer. She promises she won't practice. She will go into politics and become (my dream) the first woman president of the United States. She is a born leader and people tell me she has genuine charisma, though I'd prefer she clean her room more frequently. She has promised me "first sleep" in the Lincoln bedroom if I clean up after myself and ” more importantly ” contribute handsomely to her campaign and stay out of her decision-making. Look closely. That's me selling Newton's Telecom Dictionaries out the side door of the White House. Claire is a great kid. I couldn't be happier . See Michael for the other one. And see Susan for the mother, who made it all happen and brought them up while Daddy was doing something "important" ” like writing definitions for this dictionary. Claire read this "definition" and wrote, "1. Would you really rather me clean my room than be charismatic? That seems drastic. 2. You say that Mom raised us while you were "doing something important"...I know you're saying it sarcastically, but it could be construed that you think raising children is not as important as making money." It's not possible to argue with your daughter or your wife ” especially if they gang up on you, as they always do.


Called Line Address Modification Notification.


An electronic circuit which sets the level of a signal before the scanning of each line begins to insure that no spurious electronic noise is introduced into the picture signal from the electronics of the video equipment.


  1. Holding within an established operating range, or baseline or midline range in a circuit, in order to maintain various processes or electrical charges at a stable or safe level.

  2. In a cathode ray tube (CRT), a process which establishes a level for the picture display at the beginning of each scan line within a frame.

Clamping Voltage

The voltage at which a surge protector begins to stop electricity from getting through. A good surge protector in a 120 volt circuit (the one common in North America) has a clamping voltage of about 135 volts. Damage to computer equipment can occur as low as 160 volts.

Clarifying Bar

In cheap hotels ” i.e. the ones I stay in ” soap is called. In ritzy hotels ” i.e. the ones my wife likes ” a bar of soap is now called a "clarifying bar," which costs more but does nothing different.

Clark's Law

This Law was created by Jim Clark, the only man who ever created three companies, each with a market capitalization of over $1 billion. His Law states that "a person's wealth grows faster than his or her ability to manage it." His companies were Silicon Graphics, Netscape and Healtheon.

Clarke, Arthur C.

Arthur C. Clarke is credited with inventing the concept of satellite communications. In 1945, he published an article entitled "Extra-Terrestrial Relays" in a magazine called Wireless World. He described what we know today as GEOs (Geosynchronous Earth Orbiting) satellites , which are placed in equatorial orbits at altitudes or approximately 22,237 miles. Many years later, he published an article entitled "A Short History of Comsats, Or: How I Lost a Billion Dollars in My Spare Time." Clarke failed to patent the concept. Outside the communications domain, Clarke is best known for his science fiction works, including "2001: A Space Odyssey." He currently lives in Sri Lanka, previously called Ceylon. See also Clarke Orbit and GEO.

Clarke Orbit

Named after Arthur C. Clarke, who invented GEOs (Geosynchronous Earth Orbiting) satellites, a Clarke Orbit is better known as a geosynchronous orbit, or a geostatic orbit. See also Clarke, Arthur C.; and GEO.


Centrex Line Assignment Service. A service from local phone companies, which allows Centrex phone subscribers to change their class of service by dialing in on a personal computer, reaching the phone company's computer and then changing things themselves ” without phone company personnel assisting or hindering .

In short, load your PC with communications software. Dial your local central office. Change your Centrex phone numbers. Turn on, turn off features. Change pickup groups. Add numbers to speed dialing, etc. Your on-line changes are checked by the phone company's computers. If they make sense (i.e. one change doesn't conflict with another), they take effect by early the following day ” at which time you can call up and get a report on which took, which didn't and who's got what. Saves calling in person. Is more accurate. And, best of all, saves money. Typically just one flat monthly charge. No charge for any of your changes.


  1. Custom Local Area Signaling Services. It is based on the availability of channel interoffice signaling. CLASS consists of number-translation services, such as call-forwarding and caller identification, available within a local exchange of a Local Access and Transport Area (LATA). CLASS is a service mark of Bellcore, now Telcordia Technologies. Some of the phone services which Telcordia promotes for CLASS are Automatic Callback, Automatic Recall, Calling Number Delivery, Customer Originated Trace, Distinctive Ringing/Call Waiting, Selective Call Forwarding and Selective Call Rejection. See also Calling Line Identification.

  2. In an object-oriented programming environment, a class defines the data content of a specific type of object, the code that manipulates it, and the public and private programming interfaces to that code. See ANI and ISDN.

  3. See also Class 1 and 2, below.

Class 1

Also called Class 1/EIA-578. It's an American standard used between facsimile application programs and facsimile modems for sending and receiving Class 1 faxes. The Class 1 interface is an extension of the EIA/TIA's (Electronics Industry Association and the Telecommunications Industry Association) specification for fax communication, known as Group III. Class 1 is a series of Hayes AT commands that can be used by software to control fax boards . In Class 1, both the T.30 (the data packet creation and decision making necessary for call setup) and ECM/BFT (error-correction mode/binary file transfer) are done by the computer. A specification being developed (fall of 1991), Class 2, will allow the modem to handle these functions in hardware. Industry analysts believe Class 2 will be the standard for the long haul, but approval is slow. Even so, some modem makers will shortly deliver data/fax modems. See also Class 1 Office.

Class 1 Office

A regional toll telephone switching center. The highest level toll office in AT&T's long distance switching hierarchy. There are essentially five levels in the hierarchy, with the lowest level ” Class 5 ” being those central offices owned by the local telephone companies. Each of the classes can complete calls between themselves. But, if the routes are busy, then calls automatically climb the hierarchy. A Class 1 office is the office of "last resort."

Class 2

Also known as Class 2.0/EIA-592. An American standard used between facsimile application programs and facsimile modems for sending and receiving Class 2.0 faxes. This class places more of the task of establishing the fax connection onto the fax modem, while continuing to rely on the host's processor to send and receive the image data. The Class 2 standard (known as PN-2388) is still under study by the EIA's (Electronic Industries Association) TR.29 committee, with further revisions expected. See Class 1.

Class 2 Office

The second level in AT&T's long distance toll switching hierarchy.

Class 3 Office

The third level in AT&T's long distance toll switching hierarchy.

Class 4 Office

The fourth level in AT&T's long distance toll switching hierarchy ” the major switching center to which toll calls from Class 5 offices are sent. In U.S. common carrier telephony service, a toll center designated "Class 4C" is an office where assistance in completing incoming calls is provided in addition to other traffic. A toll center designated "Class 4P" is an office where operators handle only outbound calls, or where switching is performed without operator assistance.

Class 5 Office

An end office. Your local central office. The lowest level in the hierarchy of local and long distance switching which AT&T set up when it was "The Bell System." A class 5 office is a local Central Office that serves as a network entry point for station loops and certain special-service lines. Also called an End Office. Classes 1, 2, 3, and 4 are toll offices in the telephone network.

Class A Certification

A Federal Communications Commission (FCC) certification that a given make and model of computer meets the FCC's Class A limits for radio frequency emissions, which are designed for commercial and industrial environments. See Class B Certification.

Class A Data Center

See Carrier Hotel.

Class A Networks

See Internet Address.

Class A Traffic

A class of ATM (Asynchronous Transfer Mode) traffic defined by the ITU-T. Class A traffic is defined as being connection-oriented, Constant Bit Rate (CBR) traffic that must be carefully synchronized between transmitter and receiver. Further, such traffic is stream-oriented, and is highly intolerant of both latency (i.e., delay) and jitter (i.e., variability in latency). Class A traffic is supported by AAL (ATM Adaptation Layer) Type 1. Examples of Class A traffic include uncompressed voice and video. See also AAL 1.

Class Action Suit

Litigation undertaken on behalf of a group of alleged aggrieved people, for example owners of a product that was found defective and which killed some of its owners . A class action suit might be undertaken by shareholders of companies whose shares have declined in price. The suit might allege misstatements or omissions in the preliminary prospectus or other material communicated to the public. Shareholder law suits , are now harder to mount due to Federal legislation.

Class B Certification

A Federal Communications Commission (FCC) certification that a given make and model of computer meets the FCC's Class b limits for radio frequency emissions, which are designed to protect radio and television reception to residential neighborhoods from excessive radio frequency interference (RFI) generated by computer usage. Class B computers also are shielded more efficiently from external interface. Computers used at home are more likely to be surrounded by radio and television equipment. If you plan to use your computer at home, avoid computers that have only Class A certification (that is, they failed Class B).

Class B Networks

See Internet Address.

Class B Traffic

A class of ATM (Asynchronous Transfer Mode) traffic defined by the ITU-T. Class B traffic is defined as being connection-oriented, Real-Time Variable Bit Rate (rt-VBR) traffic that must be carefully synchronized between transmitter and receiver. Further, such traffic is stream-oriented, and can tolerate some levels of both latency (i.e., delay) and jitter (i.e., variability in latency). Class B traffic is supported by AAL (ATM Adaptation Layer) Type 2. Examples of Class B traffic include compressed voice and video. See also AAL 2.

Class C Networks

See Internet Address.

Class C Traffic

A class of ATM (Asynchronous Transfer Mode) traffic defined by the ITU-T. Class C traffic is defined as being connection-oriented, Non Real-Time Variable Bit Rate (nrt-VBR) traffic that requires no synchronization between transmitter and receiver. Class C traffic can tolerate considerable levels of both latency (i.e., delay) and jitter (i.e., variability in latency). Class C traffic is supported by AAL (ATM Adaptation Layer) Type 3/4. Examples of Class C traffic include X.25 and Frame Relay. See also AAL 3/4.

Class C IP block.

A class C is a block of 256 IP address ” 254 usable (0 is reserved for a broadcast for the subnet and 255 is for a loopback.)

Class D Traffic

A class of ATM (Asynchronous Transfer Mode) traffic defined by the ITU-T. Class D traffic is defined as being connectionless, Non Real-Time Variable Bit Rate (nrt-VBR) traffic that requires no synchronization between transmitter and receiver. Class D traffic can tolerate considerable levels of both latency (i.e., delay) and jitter (i.e., variability in latency). Class D traffic is supported by AAL (ATM Adaptation Layer) Type 3/4. Examples of Class D traffic include LAN and SMDS. See also AAL 3/4. See Internet Address.

Class E Networks

See Internet Address.

Class n Office

The way a telephone company defines its switching facilities. Class 5 is an end office (local exchange), Class 4 is a toll center, Class 3 is a primary switching center, Class 2 is a sectional switching center, and Class 1 is a regional switching center. See Class 1, Class 2, Class 3, Class 4 and Class 5.

Class Of Emission

The set of characteristics of an emission, designated by standard symbols, e.g., type of modulation of the main carrier, modulating signal, type of information to be transmitted, and also if appropriate, any additional signal characteristics.

Class Of Office

A ranking assigned to switching points in the telephone network, determined by function, interfaces and transmission needs.

Class Of Service

  1. Here's the definition of Class of Service internal to a PBX: Each phone in a corporation telephone system may have a different collection of privileges and features assigned to it, such as access to long distance, international calls, 900 area code calls, 976 local calls, etc. Let's say you are afraid that your people will waste the company's money by frivolously calling some expensive numbers, you might wish to define "Class of Service" assignments in your PBX. You could have one that's called "ability to dial everywhere except 900 area code, international calls and all 976 numbers." That could be Class of Service Assignment B. When you give a phone to an employee, you could simply give that person COS B. Big bosses, on the other hand might need to call internationally, but not 900 area code or 976 calls. That could be called Class of Service Assignment A. Class of Service assignments if properly organized, can become an important tool in controlling telephone abuse.

  2. Here's the definition on the public switched network: A subgrouping of telephone users for the sake of rate distinction. This may distinguish between individual and party lines, between Government lines and others, between those permitted to make unrestricted international dialed calls and others, between business or residence and coin, between flat rate and message rate, and between restricted and extended area service.

  3. Here are words courtesy Cisco relating to class of service issues on a packet switched network. "Networks typically operate on a best-effort delivery basis. All traffic has equal priority and an equal chance of being delivered in a timely manner. When congestion occurs, all traffic has an equal chance of being dropped. However, network managers are increasingly presented with a variety of bandwidth-hungry applications that compete for limited bandwidth on the enterprise network. These applications have a variety of characteristics. They may be mission-critical legacy applications with a Web interface, online business-critical applications, or newer multimedia-based applications such as desktop videoconferencing, Web-based training, and voice (telephone) over IP. Some of these applications are vital to core business processes, while many are not. It is the network manager's job to ensure that mission-critical application traffic is protected from other bandwidth-hungry applications, while still enabling less critical applications such as desktop videoconferencing. Enterprises that want to deploy new bandwidth-hungry applications are judging that it is paramount to also ensure the continued success of mission-critical applications over both the LAN and WAN. This can be achieved by defining network policies, which align network resources with business objectives and are enforced by means of QoS (Quality of Service) mechanisms. Without these QoS controls, non-vital applications can quickly exhaust network resources at the expense of more important ones, such as mission-critical applications, thus compromising business processes and certainly productivity. The QoS feature on the Cisco Catalyst 6000 family of switches priori - tizes network traffic with IEEE 802.1p class-of-service (CoS) values that allow network devices to recognize and deliver high-priority traffic in a predictable manner. When congestion occurs, QoS drops low-priority traffic to allow delivery of high-priority traffic. Ports can be configured as trusted or untrusted, indicating whether or not to trust the CoS values in received frames to be consistent with network policy. On trusted ports, QoS uses received CoS values. On untrusted ports, QoS replaces received CoS values with the port CoS value."

Class X Traffic

A class of ATM (Asynchronous Transfer Mode) traffic defined by the ITU-T. Class X traffic is defined as being either connection-oriented or connectionless, traffic that accepts either Unspecified Bit Rate (UBR) or Available Bit Rate (ABR) transmission, and that requires no synchronization between transmitter and receiver. Class X traffic can tolerate considerable levels of both latency (i.e., delay) and jitter (i.e., variability in latency). Class X traffic is supported by AAL (ATM Adaptation Layer) Type 5. Examples of Class X traffic include LANE (LAN Emulation) and IP. See also AAL 5.

Class-4 Switch

Class-4 is a type of circuit switch used in a tandem office. In the past, Class-4 switches managed only high-speed, four-wire T-1, T-3, and OC-3 connections (used to deliver long-distance services) in contrast to two-wire local lines on Class-5 switches. All switches now support four-wire lines.

Class-5 Switch

Class-5 is a type of circuit switch used in a local telephone end office. It provides end-customer services, such as call waiting and call forwarding.

Classical IP

A set of specifications developed by the Internet Engineering Task Force (IETF) for the operation of LAN-to-LAN IP connectivity over an ATM network.

Classified Ad

Log Records required by Section 76.221(f) of the FCC Rules which relate to origination cablecasts or classified advertisements sponsored by individuals. This rule provides that the sponsor of such programming need not be identified within the content of the advertisement or program itself provided that two conditions are met:

  • The true sponsor must be an individual offering services which he or she personally provides (examples: yard work; babysitting ).

  • The system must maintain a written record of the name, address, and telephone number of the individual.

Classless Inter-Domain Routing



A designator used to describe the service feature privileges, restrictions, and circuit characteristics for lines or trunks accessing a switch; e.g., precedence level, conference privilege, security level, zone restriction. See Class of Service.


Common Link Access for Workstations. Data link layer protocol used by channel- attached RISC System/6000 series systems and by IBM 3172 devices running TCP/IP offload. CLAW improves the efficiency of channel use and allows the Channel Interface Processor (CIP) to provide the functionality of a 3172 in TCP/IP environments and to support direct channel attachment. The output from TCP/IP mainframe processing is a series of IP datagrams that the router can switch without modifications. See CIP.


Carrier Liaison Committee. A committee formed to help industry participants work together to resolve the issues of implementing 800 Portability. CLC is sponsored by the Exchange Carriers Standards Association (ECSA) and is comprised of the LECs (local exchange carriers), long distance carriers and users of 800 service.


Common Language Circuit Identification. An industry standard format for identifying a special access circuit by the characters used in the circuit code. This designation code is unique and in a form that is acceptable to both manual and mechanized procedures.


Competitive Long Distance carrier, a European term for what people in North America call a competitive IntereXchange Carrier (IXC).

CLD Coalition Inc.

Competitive Long Distance Coalition, a Washington, DC-based lobbying group.


Customer Location Equipment, same as Customer Premise Equipment or CPE. CLE is used by fancy, schmantzy telecom salespeople who want to impress their dumb customers. Don't be impressed. It means any and all telecom equipment in your office, factory, hospital, hotel or home.


To cause one or more storage locations to be in a prescribed state, usually that corresponding to a zero or to the space character.

Clear Channel

  1. In radio broadcasting a frequency assigned for the exclusive use of one entity. The FCC defines a clear channel as protecting radio stations designated as Class A stations from objectionable interference within their primary and secondary service areas. The secondary service areas of the stations may extend outward from a distance of up to 750 miles at night. To provide this wide area service, Class A stations operate within a power range of 10 to 50 kilowatts.

  2. In networking, a signal path that provides its full bandwidth for a user's service. No control or signaling is performed (or needed) on this path.

  3. In digital networking, it's a circuit where no framing or control bits (i.e. for signaling) are required, thus making the full bandwidth available for communications. For example, a 56 Kbps circuit is typically a 64 Kbps digital circuit with 8 Kbps used for signaling. Sometimes called Switched 56, DDS or ADN. Each of the carriers have their own name for clear channel service. The phone companies are obsoleting the 56 Kbps service in favor of the more modern ISDN BRI, which has two 64 Kbps circuits and one 16 Kbps packet service, part of which is used for signaling on the 64 Kbps channels.

  4. An SCSA term. A channel which is used exclusively for data transmission, with no bandwidth required for administrative messages such as signaling or synchronization. All SCbus data channels are clear.

Clear Collision

Contention that occurs when a DTE and a DCE simultaneously transfer a clear request packet and a clear indication packet specifying the same logical channel. The DCE will consider that the clearing is completed and will not transfer a DCE clear confirmation packet.

Clear Confirmation Signal

A call control signal to acknowledge reception of the DTE clear request by the DCE or the reception of the DCE clear indication by the DTE.

Clear To Send

CTS. One of the standard attributes of a modem in which the receiving modem indicates to the calling modem that it is now ready to accept data. One of the standard pins used by the RS-232-C standard. In ITU-T V.24, the corresponding pin is called Ready For Sending.


A service company that collects and processes roaming and billing information from a number of carriers. It then transfers the compiled data to the proper carriers for credits and billing.


To cut the end of fiber at 90 degrees with as few rough edges as possible for a fusion splice. With mechanical splices the ends are hand-smoothed with a polishing puck before splicing.


Competitive Local Exchange Carrier. The term and concept was coined by the Telecommunications Act of 1996. Essentially the idea of the CLEC was that it would be a new local phone company that would be compete with the incumbent, i.e. existing, monopoly local phone company. The idea behind the Act was that the incumbent would be forced to lease local wired loops and other bits and pieces of its phone equipment ” called unbundled network elements (UNE) ” to the new phone company, i.e. the CLEC. Ultimately, the theory went, the CLEC would start building his own local phone lines and installing his own equipment and the public would benefit by better, cheaper, more innovative telecom service ” especially broadband service to the Internet. The idea of leasing some of the ILEC's plant was to give the CLEC a "leg-up." This was the theory. The first problem was that the legislation was the worst-written piece of legislation ever passed by Congress. The second problem was the ILECs deeply resented the idea that they were to allow competitors to get started in business at their expense and using their equipment and their lines. So the ILECs basically did everything they could get away with to mess up the CLECs. That meant delaying CLECs orders, creating onerous, cumbersome, new rules for doing business with them and creating huge, new charges for new services. For example, SBC (the new SouthWestern Bell) came up with something called "Unbundled Local Switching" and stated in their new tariff that "The Rate Structure for ULS will be one of 2 rate structures: Stand Alone ULS or ULS-Interim Shared Transport (ULS-IST)." SBC laid out "General Principles for Stand Alone ULS: Stand Alone Unbundled Local Switching (ULS) which included charging for a single usage sensitive component in addition to the "appropriate" non-recurring and monthly recurring rates contained in the rate table. No one, of course, knew what any of this meant but it didn't make any difference. It delayed and confused things. It was sort of like laying siege to your enemy. And when you have unlimited resources (like the ILECs) you clearly will win. The CLECs' final problem was marketing and sales. They were basically selling a service ” phone or data service ” that someone (their potential customers) can't see, feel, touch or smell. The only differentiating criterion falls on sound ” the quality of which is totally indistinguishable between the CLEC and the ILEC or between the CLEC and any other phone company in the country. The lack of a market and sales differentiator made selling CLEC services very very difficult. You couldn't sell a better product, so you sold lower prices. But no one believes the pitch for lower telecom prices. They've heard that "cut price" story a thousand times since long distance was de-regulated in the US in the late 1950s. One CLEC, looking for a marketing magic bullet, did some market research among its potential customers and found that virtually all believed that the local ILEC was "The devil you know and the local CLEC was the devil you don't know." As a result virtually all CLECs formed in the U.S. after 1996 have essentially failed ” gone bankrupt, about to go bankrupt or are only surviving because some kindly soul is pouring good money after bad and hasn't the guts to close down his disaster. This may be too harsh . There are variations on the CLEC theme that may make it, but they need to be in no way dependent on the local ILEC for anything and they need to figure some clever way to save on their horrendously high capital expenditures and come up with some clever highly-demanded, new telecom services. Right now, the CLECs compete on a selective basis for local phone service, long distance, international, broadband Internet access, and entertainment (e.g., Cable TV and Video on Demand). CLECs include cellular/PCS providers, ISPs, IXCs, CATV providers, CAPs, LMDS operators and power utilities. See Telecommunications Act of 1996 and UNE.

CLEI Codes

Common Language Equipment Identifier codes that are assigned by Bellcore (now Telcordia Technologies) to provide a standard method of identifying telecommunications equipment in a uniform, feature-oriented language. It's a text/ barcode label on the front of all equipment installed at RBOC facilities et. al. that facilitates inventory, maintenance, planning, investment tracking, and circuit maintenance processes. Suppliers of telecommunication equipment give Telcordia Technologies' technical data on their equipment, and Bellcore assigns a CLEI code to that specific product. Bellcore's GR-485-CORE specification contains the generic guidelines for Common Language Equipment Coding Processes and Guidelines. See also CPR.


Conference of the Lasers and Electro-Optics Society.


  1. Command line interface.

  2. Cumulative Leakage Index. As used in the FCC Rules (in Section 76.611(a)(1)), this term identifies the results of a ground-based measurement of the signal-leakage performance of a cable television distribution system. Under the procedure specified in this rule, each leak is measured on the ground and the CLI is then calculated from measurement data (this term does not include the results of airspace measurements specified in Section 76.611(a)(2)). The calculated CLI value must be reported to the FCC by July 1 of each year on FCC Form 320.

  3. See CLLI Code.

  4. Calling Line Identification. Data generated by a network that displays the calling party's number.


A common thought or idea, that has lost originality, ingenuity, and impact by great overuse. "Let's have some new cliches." Samuel Goldwyn, film producer.

Click Stream

A click stream is the sequence of clicks of pages requested by a Web surfer. This is important in gauging the value of different sites and the impact of different advertising initiatives on the Web.

Click Through

See Clickthrough.

Click Through Rate

See Clickthrough Rate.

Click Tones

A particular progress tone injected onto the forward voice channel (mobile unit receive, base station transmit) to indicate to the subscriber that the call has not been abandoned by the system. Basically click tones indicate acknowledgment by the cellular system that the cellular system's computer is processing the call.

Clicks And Mortar

A business that combines traditional retail ( bricks and mortar, i.e. real buildings) and on-line ecommerce shopping.


The paths a user takes as he or she navigates cyberspace . Advertisers and online media providers are developing software that can accurately track user's click- streams.

Newton[ap]s Telecom Dictionary
Newton[ap]s Telecom Dictionary
ISBN: 979387345
Year: 2004
Pages: 133

flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net