Telecom Dictionary - Definitions of terms

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

C

Cable - 1. An assembly of one or more insulated conductors, or optical fibers, or a combination of both, within an enveloping jacket. Note 1: A cable is constructed so that the conductors or fibers may be used singly or in groups. Note 2: Certain types of communications cables, especially long submarine cables but also terrestrial cables, whether the communications media are metallic or optical fiber, may contain metallic conductors that supply power to repeaters (amplifiers). 2. A message sent by cable, or by any means of telegraphy (including wireless means).

CableCARD - Security card that Digital Cable Ready (DCR) TV owners must obtain from their cable company in order to view scrambled programming, such as premium services.

Cable Head-Rnd (or headend) - is the facility at a local cable TV office that originates and communicates cable TV services and cable modem services to subscribers. In distributing cable television services, the head-end includes a satellite dish antenna for receiving incoming programming. This programming is then passed on to the subscriber. (Cable TV companies may also play videotapes and originate live programming.) Normally, all signals are those that are sent downstream to the subscriber, but some are received upstream such as when a customer requests a pay-per-view program.

When a cable company provides Internet access to subscribers, the head-end includes the computer system and databases needed to provide Internet access. The most important component located at the head-end is the cable modem termination system (CMTS), which sends and receives digital cable modem signals on a cable network and is necessary for providing Internet services to cable subscribers.

Cable Internet - Cable Internet or cable modem access provides Internet access via Hybrid Fiber Coaxial wiring originally developed to carry television signals. Either fiber-optic or coaxial copper cable may connect a node to a customer's location at a connection known as a cable drop. In a cable modem termination system, all nodes for cable subscribers in a neighborhood connect to a cable company's central office, known as the "head end." The cable company then connects to the Internet using a variety of means – usually fiber optic cable or digital satellite and microwave transmissions. Like DSL, broadband cable provides a continuous connection with an ISP.

Downstream, the direction toward the user, bit rates can be as much as 400 Mbit/s for business connections, and 100 Mbit/s for residential service in some countries. Upstream traffic, originating at the user, ranges from 384 kbit/s to more than 20 Mbit/s. Broadband cable access tends to service fewer business customers because existing television cable networks tend to service residential buildings and commercial buildings do not always include wiring for coaxial cable networks.[32] In addition, because broadband cable subscribers share the same local line, communications may be intercepted by neighboring subscribers. Cable networks regularly provide encryption schemes for data traveling to and from customers, but these schemes may be thwarted.

Cable TV (CATV) - A broadband communications technology in which multiple television channels, as well as audio and data signals, may be transmitted either one way or bidirectionally through an often hybrid (fiber and coaxial) distribution system to a single or to multiple specific locations. CATV originated in areas where good reception of direct broadcast TV was not possible. Now CATV also consists of a cable distribution system to large metropolitan areas in competition with direct broadcasting. The abbreviation CATV originally meant community antenna television. However, CATV is now usually understood to mean cable TV.

CALEA (Communications Assistance for Law Enforcement Act) - A 1994 act that requires telecommunications services to provide wiretapping access. The act specifically excludes information services, so the question is whether VoIP is a telecommunications service, and thus covered by the act, or an information service, and thus exempted. VoIP providers are receiving pressure to comply with the act.

Call - 1. In communications, any demand to set up a connection. 2. A unit of traffic measurement. 3. The actions performed by a call originator. 4. The operations required to establish, maintain, and release a connection. 5. To use a connection between two stations. 6. The action of bringing a computer program, a routine, or a subroutine into effect, usually by specifying the entry conditions and the entry point. 7. A customer attempt for which complete address information (e.g., 0-, 911, or 10 digits) is provided to the serving dial tone office.

Call Attempt - In a telecommunications system, a demand by a user for a connection to another user. Note: In telephone traffic analysis, call attempts are counted during a specific time frame. The call-attempt count includes all completed, overflowed, abandoned, and lost calls.

Callback ( international callback) - is a system for avoiding regular phone company long-distance charges by having a call initiated from within the United States with the orginating caller joining in a conference call. Here's how the procedure works:

• A call originator (for example, someone in South America) calls a predesignated number in the United States, waits until it rings once, and then hangs up.
• A machine in the office where the phone rang recognizes that the phone number was called and knows the phone number of the party that called it (because it was the only party that knew the number).
• The machine places a call (which may be a local or a long-distance call) that originates from the U.S. location and also calls the party who initiated this procedure, thus arranging a conference call but at the U.S. long-distance rate.
• In another variation, the automatically-generated call from the U.S. may call the originator and ask the originator to dial their desired number or provide a U.S. dial tone.
• The originator (who subscribes to this callback service) is billed by the U.S.-based service at its own rates.

In localities where portable phone (cellphone) companies do not charge for incoming calls, callback is also sometimes used to avoid airtime charges for outgoing calls.

Call Block - Allows you to block up to six pre-selected phone numbers.

To block a designated phone number, press *60 , press #, wait for the dial tone, and dial the first designated phone number you wish to block, followed by the #. Repeat this process to add more phone numbers. To deactivate, press *80. Calls from cellular phones and calls placed with operator assistance cannot be blocked.

Call Block 900/976 Restriction - Restricts all outgoing calls to 900 and 976 telephone numbers. Due to many phone companies’ inability to bill 900 and 976 calls, most will automatically block all 900 and 976 calls originating from your residential telephone line.

Call Block Full Restriction - Allows you to restrict all outgoing calls to 1+, 0-, 0+, 00-, 211, 311, 411, 511, 900 telephone numbers, 976 telephone numbers, International 01+, International 011, 101XXXX.

Call Blocking Options - Local phone companys may offer several call blocking options that you may subscribe to such as Anonymous Call Rejection, Billed Number Screening, Call Block 900/976 Restriction, Call Block Full Restriction, Call Block International Restriction, Call Block Long Distance Toll Restriction, Caller ID - Block Per Line, Caller ID - Block Per Call, and Pay Per Use Feature Blocking. Monthly Recurring Charges may apply. Most phone companies must provide and cannot charge local customers for Caller ID Per-Call Blocking of their number.

Call Block International Restriction – Restricts you from placing outgoing 011+ and 101XXXX011+ International direct dialed calls.

Call Block Long Distance Toll Restriction - Restricts you from placing 1+ and 0+ outgoing calls (including access to 900/976 pay per call services).

Call Collision - 1. The contention that occurs when a terminal and data circuit-terminating equipment (DCE) specify the same channel at the same time to transfer a call request and handle an incoming call. Note: When call collision occurs, the DCE proceeds with the call request and cancels the incoming call. 2. The condition that occurs when a trunk or channel is seized at both ends simultaneously, thereby blocking a call. Synonym dual seizure. Deprecated synonym glare.

Caller ID -Allows you to view the telephone number, date and time on your caller ID display before the call is answered. The calling information is delivered between the first and second ringing cycle of the call. See Caller ID with Number and Caller ID with Number, Name and ACR for more information

Caller ID Blocking (Calling Number Delivery Block) - Prevents your name and number from appearing on
the Caller ID unit of the person you’re calling. You may subscribe to Caller ID Complete Blocking at no
charge for continuous call blocking. To activate Caller ID Blocking on a per-use basis, press *67 before
each call. If you subscribe to continuous Caller ID Complete Blocking, press *82 before each call
to deactivate the service.

Caller ID - Block Per Line - Allows you to prevent delivery of your telephone number on all outgoing calls. Once you subscribe to this feature, it will be in operation on a continuous basis unless you dial *82 to unblock before a call is placed. This feature is also known as “Caller ID – Complete Blocking per Line.”

Caller ID - Block Per Call - Allows you to prevent delivery, on a per call basis, of your telephone number on an outgoing call to another party who subscribes to Caller ID. You can access this service by dialing *67. This feature is also known as “Caller ID - Selective Block per Call.”

Caller ID – Complete Blocking per Line - - Allows you to prevent delivery of your telephone number on all outgoing calls. Once you subscribe to this feature, it will be in operation on a continuous basis unless you dial *82 to unblock before a call is placed. This feature is also known as “Caller ID – Block per Line.”

Caller ID - Selective Block per Call - - Allows you to prevent delivery, on a per call basis, of your telephone number on an outgoing call to another party who subscribes to Caller ID. You can access this service by dialing *67. This feature is also known as “Caller ID - Block per Call.”

Caller ID with Number - Allows you to view the telephone number, date and time on your caller ID display before the call is answered. The calling information is delivered between the first and second ringing cycle of the call. System will default to this if Caller ID with Number, Name and ACR is not available.

Caller ID with Number, Name and ACR – Displays the listed name associated with the incoming telephone number. The name will be delivered to your caller ID display device attached to your telephone line, telephone, or answering machine with a built-in display screen.

Call Failure Rate (CFR)- is a statistical measure commonly used in assessing Internet service providers (ISPs) or any network provider. The call failure rate is the percentage of calls to an ISP or network provider that fail to get through. Companies can measure the CFR for their own employees who dial in for access to the company's network. Rating companies report on the CFRs for major ISPs like AOL, Ameritech, and Mindspring. Visual Networks, formerly Inverse Network Technology, is probably the best known benchmarking company of ISPs.

Call Forwarding - A telephone service that enables a customer to have an incoming call automatically rerouted rerouted to another, designated number or extension.

Notice that the fee charging structure for a calling party to place a call to the called party which has their number forwarded can be subtle: if the called party has forwarded their number to a mobile telephone, the caller could incur higher rates due to the subsequent use of the mobile telephone network. However, the line which is being forwarded usually incurs all related charges, including long distance.

Special types of call forwarding can be activated only if the line is busy, or if there is no answer, or even only for calls from selected numbers. In North America, the NANP uses the following vertical service codes to control call forwarding:

• forward all calls: *72, activation; *73, deactivation
• on busy or no answer: *68, activation; *88, deactivation
• from select callers: *63, activation; *83, deactivation
• on ISDN: *56, change forward-to number

Customer-programmable features (where available):

• busy line: *90, activation; *91, deactivation; *40, change number
• no answer: *92, activation; *93, deactivation; *42, change number

Call Forwarding Busy – Allows you to activate this feature, via dialed access voice prompt menus, to automatically transfer all incoming calls that reach a busy response from your telephone number to another telephone number until you deactivate this feature.

Call Forwarding Busy/No Answer - Allows you to activate this feature, via dialed access voice prompt menus, to automatically transfer all incoming calls that reach a busy or no answer response from your telephone number to another telephone number until you deactivate this feature.

Call Forward Busy- Call Alert for AOL - supports a new s ervice AOL is offering to its customers. It will provide you with an alert that a call has come in over the same line you are utilizing to access the Internet.

Call Forwarding No Answer - Allows you to activate this feature, via dialed access voice prompt menus, to automatically transfer all incoming calls that reach a no answer response from your telephone number to another telephone number until you deactivate this feature.

Call Forwarding - Preferred - Allows you to transfer up to six telephone numbers on a screening list to another number. Only the calls on the screening list are forwarded. You can activate this feature by dialing *63, and deactivate by dialing *83.

Call Forwarding Remote Access – Allows you to remotely activate the call forwarding feature at your home, or change the call forwarded telephone number that was previously set. This feature includes the basic Call Forwarding Variable feature. It allows you to forward calls from your home telephone number or from another telephone number when away from home using a touchtone phone.

Call Forwarding Ring No Answer - Allows you to control the number of seconds or ring cycles that occur prior to forwarding an unanswered call to voice mail or to another telephone number.

Call Forwarding Variable - Allows you to forward your calls to a number of your choosing. Allows you to activate this feature, via dialed access voice prompt menus, to automatically transfer all incoming calls from your telephone number to another telephone number until you deactivate this feature.

Press 72# and enter the number to which you want your incoming calls forwarded. When that call is answered, Call Forward - Variable is in effect. If the call is not answered or if the number is busy, your calls will not be forwarded. You must then repeat the process for your calls to be forwarded. To deactivate, press73* . Two short tones, followed by a normal tone, will indicate the feature is deactivated. Repeat these steps each time you wish to forward calls.

Call Grab - If the Call Override feature does not perform due to any line problems with your local phone service provider, this standard feature will allow you to override the fax switch's tone detect and call routing operation. Call Grab can be initiated from any touch tone or pulse extension phone by dialing "9" on the telephone key pad. When "9" is dialed, the fax switch will immediately cease its call routing function. This feature is standard and will work regardless of the status of the "Call Override" feature. Note: YOU must enable the "Pulse Detect" feature if you want to grab a call from a pulse dial phone.

Call Management - 1. In telegraphy, route selection, signaling, and circuit usage and availability for a call. 2. In universal personal telecommunications, the ability of a user to inform the network how to handle incoming calls in accord with certain parameters, such as the call originator, the time of day, and the nature of the call. Note: Call management is accomplished by means of information in the user's service profile.

Call Originator - An entity, such as a person, equipment, or program that originates a call. Synonym calling party.

Calling Party - Synonym call originator. - An entity, such as a person, equipment, or program that originates a call.

Call Processing - 1. The sequence of operations performed by a switching system from the acceptance of an incoming call through the final disposition of the call. 2. The end-to-end sequence of operations performed by a network from the instant a call attempt is initiated until the instant the call release is completed. 3. In data transmission, the operations required to complete all three phases of an information transfer transaction.

Call Processor - A device that manages telephone traffic and routes incoming calls to the proper equipment.   A call processor analyzes and routes incoming calls to your telephones or data equipment. Multi-Link call processors are dependable and reliable. See faxswitch for more information..

Call Return - Allows you to automatically redial the last incoming telephone number, which is done by using a code. The last telephone number does not have to be known or have been answered by you. Activation must occur before another incoming call, or before a call waiting indication is received.

Allows you to dial the last number called whether you answered the call or not. Press *69 to hear a
recording of the phone number of the last incoming call. If the line is busy or there is no answer, Call
Return will continue trying to reach the calling party for 30 minutes. Press *89 to deactivate Call Return before the 30 minutes have elapsed.

Call Screening - Allows you to prevent calls from an unwanted caller whose number may or may not be known. When the unwanted call is received, you will need to hang up and immediately dial the Call Screening access code, which will deny the caller the ability to ring your telephone number. Also, you have the ability to create a list of telephone numbers from which you do not wish to receive calls. Calls from these telephone numbers will be sent to an announcement indicating that the call cannot be completed because you have activated Call Screening. Most phone comnpanies can block up to six numbers from calling your residential telephone line.

Call Screening allows you to block phone numbers from a list you’ve designated and route them to a message indicating you’re not receiving calls at this time. Dial *60 to activate and follow the instructions. Dial *80 and follow the prompts to deactivate.

Call-Second - A unit used to measure communications traffic. Note 1: A call-second is equivalent to 1 call 1 second long. Note 2: One user making two 75-second calls is equivalent to two users each making one 75-second call. Each case produces 150 call-seconds of traffic. Note 3: The CCS, equivalent to 100 call-seconds, is often used. Note 4: 3600 call-seconds = 36 CCS = 1 call-hour. Note 5: 3600 call-seconds per hour = 36 CCS per hour = 1 call-hour per hour = 1 erlang = 1 traffic unit.

Call Sign - A station or address designator represented by a combination of characters or pronounceable words that is used to identify such entities as a communications facility, station, command, authority, activity, or unit.

Call Sign Station - In broadcasting and radio communications, a Call Sign is a unique designation that identifies a transmitting station. In some cases, they are used as names for broadcasting stations. A Call Sign can be formally assigned by a government agency or informally adopted by individuals or organizations, and it can be cryptographically encoded to disguise a station's identity.

Call Trace - Allows you to initiate an automatic trace of the last call received. You need to dial *57 to have your local telephone carrier Annoyance Call Center trace annoying calls. After two confirmed traces of the same number, your local phone company's Annoyance Call Center will work with law enforcement authorities to take the appropriate action to end the annoying calls. The trace must begin prior to another call being received.

If you receive a harassing or threatening call, you can have the number traced. To activate this feature, hang
up immediately from an offensive phone call. Wait 10 seconds, pick up the handset, and press *57 to
trace the call. If the trace is successful, a confirmation announcement will be given and further instructions will be provided. If the trace is unsuccessful, you will hear an error message. Call Trace is a feature, not an emergency number.

Call Waiting - Provides a tone signal when a second call is coming in on a busy line. Allows you to answer the second call without disconnecting from the existing call, switch between the calls, and end either call at any time. This feature enables you to know when someone else is calling and allows the call to be received without having two lines. This feature is provided by many telephone companies so that two calls to be managed at the same time on one line. Your automatic call processor will work fine with "Call Waiting."

A special tone signals you when there’s an incoming call while you’re on the phone. At the tone briefly press and release the telephone switch hook or “flash” button. This places the first call on hold while you answer the incoming call. To return to the first call (and to switch back and forth), press and release the switch hook or flash button again. To temporarily deactivate Call Waiting, press *70 and wait for a second dial tone before placing your call. Call Waiting will be automatically reactivated for new incoming calls when you hang up.

Call Waiting Deluxe - Provides a tone signal when a second call is coming in on a busy line, and see caller information for the waiting call on your caller ID display. You must subscribe to Caller ID with Number, Name and ACR feature.

Allows you the benefits of Caller ID with Name and Call Waiting. The Caller ID unit displays both the names and phone numbers of incoming Call Waiting calls when you are on the phone.

A special tone signals you when there’s an incoming call while you’re on the phone. At the tone briefly press and release the telephone switch hook or “flash” button. This places the first call on hold while you answer the incoming call. To return to the first call (and to switch back and forth), press and release the switch hook or flash button again. To temporarily deactivate Call Waiting, press *70 and wait for a second dial tone before placing your call. Call Waiting will be automatically reactivated for new incoming calls when you hang up.

This feature is not compatible with Call Waiting or Call Waiting Deluxe with Call Forward No Answer.

Call Waiting Deluxe with Call Forward No Answer - Allows you to forward a waiting call to another
number. You to control the treatment applied to incoming calls while you are on a call. This feature includes the functionality of forwarding unanswered incoming calls to another telephone number or voicemail. This feature is not compatible with Call Waiting or Call Waiting Deluxe. You must have Caller ID with Number, Name and ACR.

Call Waiting Speaking – Gives you the name of the person calling. First, you hear the Call Waiting "beep" and then you hear the name of the caller. Once you've heard the name, you decide if you want to "click over" and take the call.

Candela - The luminous intensity in a specified direction, of a monochromatic source which has a frequency of 540 x 10¹² Hz and which has a radiant intensity, in the specified direction, of (1/683) watt per steradian.

Capacity - See channel capacity, traffic capacity. The maximum possible information transfer rate through a channel, subject to specified constraints.

Card - A card (or expansion card, board, or adapter) is circuitry designed to provide expanded capability to a computer. It is provided on the surface of a standard-size rigid material (fiberboard or something similar) and then plugged into one of the computer's expansion slots in its motherboard (or backplane). Cards may come in one of two sizes designed to match standard slot dimensions. A card can actually contain the capability within its circuitry (as a video card does) or it can control (through an extended connection) a device (such as a hard disk drive).

Carrier - In the telecommunications industry, a carrier is a telephone or other company that sells or rents telecommunication transmission services. A local exchange carrier (LEC) is a local phone company and an inter-exchange carrier (IEC or IXC) carries long-distance calls.

Carrier and Data Tone - very loud screech that is produced when the FAX machines or MODEMs are actually transferring data. Unlike CNG or DTMF, carrier and data will be constantly changing.

Carrier Power (of a radio transmitter) - 1. The average power supplied to the antenna transmission line by a transmitter during one radio frequency cycle taken under the condition of no modulation. Note: The concept does not apply to pulse modulation or frequency-shift keying. 2. The average unmodulated power supplied to a transmission line.

Carrier Frequency - 1. The nominal frequency of a carrier wave. 2. In frequency modulation, synonym center frequency. 3. The frequency of the unmodulated electrical wave at the output of an amplitude modulated (AM), frequency modulated (FM), or phase modulated (PM) transmitter. 4. The output of a transmitter when the modulating wave is made zero.

Carrier System - A multichannel telecommunications system in which a number of individual circuits (data, voice, or combination thereof) are multiplexed for transmission between nodes of a network. Note 1: In carrier systems, many different forms of multiplexing may be used, such as time-division multiplexing and frequency-division multiplexing. Note 2: Multiple layers of multiplexing may ultimately be performed upon a given input signal; i.e., the output resulting from one stage of modulation may in turn be modulated. Note 3: At a given node, specified channels, groups, supergroups, etc., may be demultiplexed without demultiplexing the others. Synonym [loosely] carrier.

Carrier Wave - Synonym carrier (cxr).

CATV - Abbreviation for cable TV.

CCIR - Abbreviation for International Radio Consultative Committee, a predecessor organization of the ITU-R.

CCITT - Abbreviation for International Telegraph and Telephone Consultative Committee; a predecessor organization of the ITU-T.

CCS (centum call second) - also known as the hundred call second -- is a unit of telecommunications traffic density that is the equivalent of one call (including call attempts and holding time) in a specific channel for 100 seconds in an hour. The 100 seconds need not be, and generally are not, in a contiguous block.

In digital telecommunications, the voice signals are compressed. This makes it possible for one channel to carry numerous calls simultaneously by means of multiplexing. In theory, there are many ways in which a channel can carry a particular number of CCS. Here are three specific examples for a traffic density of 360 CCS:

• 10 calls, each consuming the full hour during an hour
• 20 calls, each of which consume 1/2 hour during an hour
• 600 calls, each of which consume one minute during an hour

The CCS is a more convenient unit in some applications than the erlang, which is the equivalent of one call occupying a channel for an hour. In some instances, a smaller unit than the CCS, known as the call-second, is used. One call-second is equivalent to one call occupying a channel for one second. Thus, 1 CCS = 100 call-seconds = 1/36 erlang.

CDMA - Abbreviation for code-division multiple access. - A coding scheme, used as a modulation technique, in which multiple channels are independently coded for transmission over a single wideband channel. Note 1: In some communication systems, CDMA is used as an access method that permits carriers from different stations to use the same transmission equipment by using a wider bandwidth than the individual carriers. On reception, each carrier can be distinguished from the others by means of a specific modulation code, thereby allowing for the reception of signals that were originally overlapping in frequency and time. Thus, several transmissions can occur simultaneously within the same bandwidth, with the mutual interference reduced by the degree of orthogonality of the unique codes used in each transmission. Note 2: CDMA permits a more uniform distribution of energy in the emitted bandwidth.

CD-ROM - Pronounced see-dee-rom. Short for Compact Disc-Read-Only Memory, a type of optical disk capable of storing large amounts of data -- up to 1GB, although the most common size is 650MB (megabytes). A single CD-ROM has the storage capacity of 700 floppy disks, enough memory to store about 300,000 text pages.

CD-ROMs are stamped by the vendor, and once stamped, they cannot be erased and filled with new data. To read a CD, you need a CD-ROM player. All CD-ROMs conform to a standard size and format, so you can load any type of CD-ROM into any CD-ROM player. In addition, CD-ROM players are capable of playing audio CDs, which share the same technology.

CD-ROMs are particularly well-suited to information that requires large storage capacity. This includes large software applications that support color, graphics, sound, and especially video.

Cell - In wireless telephony, a cell is the geographical area covered by a cellular telephone transmitter. The transmitter facility itself is called the cell site. The cell provided by a cell site can be from one mile to twenty miles in diameter, depending on terrain and transmission power. Several coordinated cell sites are called a cell system. When you sign up with a cellular telephone service provider, you generally are given access to their cell system, which is essentially local. When travelling out of the range of this cell system, the cell system can enable you to be transferred to a neighboring company's cell system without your being aware of it. This is called roaming service.

The cell sites in a system connect to a Mobile Telephone Switching Office (MTSO), which in turn connects to the standard landline telephone system.

Cell Relay - A high-bandwidth, low-delay, switching and multiplexing packet technology. Its combination of simplified error and flow control, fixed-length cells which allow high-speed switching, and procedures for allocating network bandwidth enable it to support voice, data, image, and video traffic.

Cellular Phone - Synonym cellular mobile, cellular telephone. A mobile communications system that uses a combination of radio transmission and conventional telephone switching to permit telephone communication to and from mobile users within a specified area. Note: In cellular mobile systems, large geographical areas are segmented into many smaller areas, i.e., cells, each of which has its own radio transmitters and receivers and a single controller interconnected with the public switched telephone network.

Cellular Mobile - A mobile communications system that uses a combination of radio transmission and conventional telephone switching to permit telephone communication to and from mobile users within a specified area. Note: In cellular mobile systems, large geographical areas are segmented into many smaller areas, i.e., cells, each of which has its own radio transmitters and receivers and a single controller interconnected with the public switched telephone network. Synonyms cellular phone, cellular radio, cellular telephone.

Cellular Radio - Synonym cellular mobile, cellular phone, cellular telephone. A mobile communications system that uses a combination of radio transmission and conventional telephone switching to permit telephone communication to and from mobile users within a specified area. Note: In cellular mobile systems, large geographical areas are segmented into many smaller areas, i.e., cells, each of which has its own radio transmitters and receivers and a single controller interconnected with the public switched telephone network.

Cellular Telephone - A type of short-wave analog or digital telecommunication in which a subscriber has a wireless connection from a mobile telephone to a relatively nearby transmitter. The transmitter's span of coverage is called a cell. Generally, cellular telephone service is available in urban areas and along major highways. As the cellular telephone user moves from one cell or area of coverage to another, the telephone is effectively passed on to the local cell transmitter.

A cellular telephone is not to be confused with a cordless telephone (which is simply a phone with a very short wireless connection to a local phone outlet). A newer service similar to cellular is personal communications services (PCS).

Center Frequency - 1. In frequency modulation, the rest frequency, i.e., the frequency of the unmodulated carrier. Synonym carrier frequency. 2. The frequency of the middle of the bandwidth of a channel. 3. In facsimile systems, the frequency midway between the picture-black and picture-white frequencies.

Central Office (CO) - In telephone communication in the United States, a central office (CO) is an office in a locality to which subscriber home and business lines are connected on what is called a local loop. The central office has switching equipment that can switch calls locally or to long-distance carrier phone offices.

CGI -1. Abbreviation for common gateway interface. A means for allowing programs or scripts (usually written in C++ or Perl) to add functionality to the World Wide Web. Note: Examples are search engines, feedback forms, and guestbooks. 2. Abbreviation for computer graphics interface.

Changeover - The procedure of transferring signaling traffic from one signaling link to one or more different signaling links, when the link in use fails or is required to be cleared of traffic.

Channel - 1. A connection between initiating and terminating nodes of a circuit. 2. A single path provided by a transmission medium via either (a) physical separation, such as by multipair cable or (b) electrical separation, such as by frequency- or time-division multiplexing. 3. A path for conveying electrical or electromagnetic signals, usually distinguished from other parallel paths. 4. Used in conjunction with a predetermined letter, number, or codeword to reference a specific radio frequency. 5. The portion of a storage medium, such as a track or a band, that is accessible to a given reading or writing station or head. 6. In a communications system, the part that connects a data source to a data sink. 7. A virtual area where Internet Relay Chat (IRC) users communicate (exchanging text messages) in real time. Note: There are thousands of channels located on the Internet. 8. An IRC conduit designated for the real-time exchange of text messages. 9. An electrical path suitable for the transmission of communications between two or more points, ordinarily between two or more stations or between channel terminations in Telecommunication Company central offices. A channel may be furnished by wire, fiber optics, radio or a combination thereof. 10. The portion of the electromagnetic spectrum assigned by the FCC for one emission. In certain circumstances, however, more than one emission may be transmitted on a channel.

Channel-Associated Signaling - Signaling in which the signals necessary to switch a given circuit are transmitted via the circuit itself or via a signaling channel permanently associated with it.

Channel Bank - A device at a telephone company central office (public exchange) that converts analog signals from home and business users into digital signals to be carried over higher-speed lines between the central office and other exchanges. The analog signal is converted into a digital signal that transmits at a rate of 64 thousand bits per second (Kbps). This 64 Kbps signal is a standard known as a DS0 signal. The signal is multiplexed with other DS0 signals on the same line using time-division multiplexing (TDM) . Usually, the digital information is put on each DS0 signal using pulse code modulation (PCM).

Channel Capacity - The maximum possible information transfer rate through a channel, subject to specified constraints.

Channel Scan - Channel Scan will search for digital broadcast channels that are available in your area; once the scan is completed, you will be able to tune to the digital channels received by your antenna.

Character - 1. A letter, digit, or other symbol that is used as part of the organization, control, or representation of data. 2. One of the units of an alphabet.

Character Interval - In a communications system, the total number of unit intervals required to transmit any given character, including synchronizing, information, error checking, or control characters, but not including signals that are not associated with individual characters. Note: An example of a time interval that is excluded when determining character interval is any time added between the end of a stop signal and the beginning of the next start signal to accommodate changing transmission conditions, such as a change in data signaling rate or buffering requirements. This added time is defined as a part of the intercharacter interval.

Chroma Keying - In television, nearly instantaneous switching between multiple video signals, based on the state, i.e., phase, of the color (chroma) signal of one, to form a single composite video signal. Note 1: Chroma keying is used to create an overlay effect in the final picture, e.g., to insert a false background, such as a weather map or scenic view, behind the principal subject being photographed. Note 2: The principal subject is photographed against a background having a single color or a relatively narrow range of colors, usually in the blue or green. When the phase of the chroma signal corresponds to the preprogrammed state or states associated with the background color, or range of colors, behind the principal subject, the signal from the alternate, i.e., false, background is inserted in the composite signal and presented at the output. When the phase of the chroma signal deviates from that associated with the background color(s) behind the principal subject, video associated with the principal subject is presented at the output. Synonyms color keying, [loosely] blue-screening, [in security] keying.

Chromatic Dispersion - A commonly used (but redundant) synonym for material dispersion. See dispersion.

Cipher - 1. Any cryptographic system in which arbitrary symbols, or groups of symbols, represent units of plain text or in which units of plain text are rearranged, or both. 2. The result of using a cipher. Note: An example of a cipher is an enciphered message or text.

Cipher Text - Enciphered information. Note: Cipher text is the result obtained from enciphering plain or encoded text.

Circuit - 1. The complete path between two terminals over which one-way or two-way communications may be provided. 2. An electronic path between two or more points, capable of providing a number of channels. 3. A number of conductors connected together for the purpose of carrying an electrical current. 4. An electronic closed-loop path among two or more points used for signal transfer. 5. A number of electrical components, such as resistors, inductances, capacitors, transistors, and power sources connected together in one or more closed loops. 6. A fully operative communications path established in the normal circuit layout and currently used for message, WATS access, TWX, or private line services.

Circuit-Switched - Communication system that establishes a dedicated channel for each transmission. The copper-wire telephone system (POTS) uses circuit-switching, as do PBX systems. Dedicated channels mean strong reliability and low latency, but the downside is that only one type of communication can use the channel at any given time.

Cladding - 1. Of an optical fiber, one or more layers of material of lower refractive index, in intimate contact with a core material of higher refractive index. 2. A process of covering one metal with another (usually achieved by pressure rolling, extruding, drawing, or swaging) until a bond is achieved.

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.

Click-Through - The process of clicking on a Web advertisement and going directly to the advertiser's Web site. Synonyms ad clicks, clicks, requests.

Client - A program or computer that is used to contact and obtain data from another program or computer, referred to as the server.

Client-Server - Any hardware / software combination that generally adheres to a client-server architecture, regardless of the type of application.

Client-Server Architecture: Any network-based software system that uses client software to request a specific service, and corresponding server software to provide the service from another computer on the network.

Clip - 1. In moving picture or television technology, a relatively short, continuous set of frames (often including the associated audio, if any), stored on a recording medium. Synonyms take, scene. 2. In audio, a short, uninterrupted sound track. Note: Both audio and video clips may be part of a digitized information package, e.g., on a Web page. 3. To limit to a predetermined level (e.g., at the output of an otherwise linear amplifier) the amplitude of an otherwise linear signal. Note: In contrast with an analog compression circuit, which reduces the dynamic range of a signal but retains its basic waveform, a clipping circuit treats (processes, amplifies) a signal in a linear fashion unless the output level reaches a certain threshold, which it may not exceed, and at which it remains unless the input decreases to a level at which the processed output level is lower than the clipping level.

Clipping - 1. In telephony, the loss of the initial or final parts of a word, words, or syllable, usually caused by the nonideal operation of voice-actuated devices. 2. The limiting of instantaneous signal amplitudes to a predetermined maximum value. 3. In a display device, the removal of those parts of display elements that lie outside of a given boundary.

CLEC - Competitive Local Exchange Carrier. Deregulated local telephone companies resulting from the Telecommunications Act of 1996 that are competing for local exchange service, as well as for long distance and Internet service. In the United States, a CLEC (competitive local exchange carrier) is a telephone company that competes with the already established local telephone business by providing its own network and switching. The term distinguishes new or potential competitors from established local exchange carriers (LECs) and arises from the Telecommunications Act of 1996, which was intended to promote competition among both long-distance and local phone service providers.

Clock - 1. A reference source of timing information. 2. A device providing signals used in a transmission system to control the timing of certain functions such as the duration of signal elements or the sampling rate. 3. A device that generates periodic, accurately spaced signals used for such purposes as timing, regulation of the operations of a processor, or generation of interrupts.

Clock Normal Mode - An operating condition of a clock in which the output signals are controlled by an external input reference. It is the expected mode. In normal mode, each clock in a chain has the same long-term average frequency, and the time error between the input and output of each clock is bounded. Only stratum 1 sources of timing require no input and therefore have a unique status of "normal" operation being equivalent to "freerun". Synonym locked mode.

Closed Captioning - Service allowing persons with hearing disabilities to read dialogue or the audio portion of a video, film, or other presentation, on the TV screen.

Closed Circuit - 1. In radio and television transmission, pertaining to an arrangement in which programs are directly transmitted to specific users and not broadcast to the general public. 2. In telecommunications, a circuit dedicated to specific users. 3. A completed electrical circuit.

CNG - See CNG Tone.

C-Message Weighting - A noise spectral weighting used in a noise power measuring set to measure noise power on a line that is terminated by a 500-type set or similar instrument. Note: The instrument is calibrated in dBrnC.

CNG Tone (AUTO FAX TONE) (CNG ) - This tone is produced by virtually all FAX machines when it dials the receiving FAX machine’s number from memory. Older FAX machines and some current models that do not have speed-dial memory will not produce CNG. CNG is a medium-pitch tone (1100 Hz) that last 1/2 second and repeats every 3-1/2 seconds. A FAX machine will produce CNG for about 45 seconds after it dials the receiving FAX number.

An 1100Hz tone transmitted by a fax machine when it calls another fax machine. The half-second tone is repeated every 3.5 seconds for approximately 45 seconds. See fax switch.

CO - Central Office. – Your telephone company. Your CO is the building where your telephone line is electronically managed. A telephone company’s building where subscribers’ lines are joined to the switching equipment to connect calls.

Coast Station - A land station in the maritime mobile service.

Coating - See primary coating. - The plastic overcoat in intimate contact with the cladding of an optical fiber, applied during the manufacturing process. Note 1: The primary coating typically has an outside diameter of approximately 250 to 750 m, and serves to protect the fiber from mechanical damage and chemical attack. It also enhances optical fiber properties by stripping off cladding modes, and in the case where multiple fibers are used inside a single buffer tube, it suppresses cross-coupling of optical signals from one fiber to another. Note 2: The primary coating should not be confused with a tight buffer, or the plastic cladding of a plastic-clad-silica (PCS) fiber. Note 3: The primary coating, which typically consists of many layers, may be color-coded to distinguish fibers from one another, e.g., in a buffer tube containing multiple fibers. Synonyms primary polymer coating, primary polymer overcoat.

Coaxial - Coaxial inputs (sometimes just called "cable") provide a simple and common way to transmit video. Now coaxial inputs are mostly used for connecting a TV set to an antenna or cable system.

Coaxial Adapter - Device for connecting a coaxial cable to a TV with a Twin Lead cable connection port.

Coaxial Cable (coax) - 1. A cable consisting of a center conductor surrounded by an insulating material and a concentric outer conductor and optional protective covering, all of circular cross-section. Synonym (when combined with others under a common sheath) coaxial tube. 2. A cable consisting of multiple coaxial tubes under a single protective sheath. Note: Coaxial cables are used primarily for CATV and other wideband, video, or rf applications.

COBOL - Acronym for common business oriented language. A programming language designed for business data processing.

Code - 1. A set of unambiguous rules specifying the manner in which data may be represented in a discrete form. Note 1: Codes may be used for brevity or security. Note 2: Use of a code provides a means of converting information into a form suitable for communications, processing, or encryption. 2. [In COMSEC, any] system of communication in which arbitrary groups of letters, numbers, or symbols represent units of plain text of varying length. Note: Codes may or may not provide security. Common uses include: (a) converting information into a form suitable for communications or encryption, (b) reducing the length of time required to transmit information, (c) describing the instructions which control the operation of a computer, and (d) converting plain text to meaningless combinations of letters or numbers and vice versa. 3. A cryptosystem in which the cryptographic equivalents, (usually called "code groups") typically consisting of letters or digits (or both) in otherwise meaningless combinations, are substituted for plain text elements which are primarily words, phrases, or sentences. 4. A set of rules that maps the elements of one set, the coded set, onto the elements of another set, the code element set. Synonym coding scheme. 5. A set of items, such as abbreviations, that represents corresponding members of another set. Synonym encode. 6. To represent data or a computer program in a symbolic form that can be accepted by a processor. 7. To write a routine.

Codec - Term is short for "Coder-decoder." A codec is a device that converts analog video and audio signals into a digital format for transmission. It also converts received digital signals back into an analog format.

Code-Division Multiple Access (CDMA) - A coding scheme, used as a modulation technique, in which multiple channels are independently coded for transmission over a single wideband channel. Note 1: In some communication systems, CDMA is used as an access method that permits carriers from different stations to use the same transmission equipment by using a wider bandwidth than the individual carriers. On reception, each carrier can be distinguished from the others by means of a specific modulation code, thereby allowing for the reception of signals that were originally overlapping in frequency and time. Thus, several transmissions can occur simultaneously within the same bandwidth, with the mutual interference reduced by the degree of orthogonality of the unique codes used in each transmission. Note 2: CDMA permits a more uniform distribution of energy in the emitted bandwidth.

Code Word - 1. In a code, a word that consists of a sequence of symbols assembled in accordance with the specific rules of the code and assigned a unique meaning. Note: Examples of code words are error-detecting-or-correcting code words and communication code words, such as SOS, MAYDAY, ROGER, TEN-FOUR, and OUT. 2. A cryptonym used to identify sensitive intelligence data. 3. A word that has been assigned a classification and a classified meaning to safeguard intentions and information regarding a classified plan or operation.

Coding - 1. In communications systems, the altering of the characteristics of a signal to make the signal more suitable for an intended application, such as optimizing the signal for transmission, improving transmission quality and fidelity, modifying the signal spectrum, increasing the information content, providing error detection and/or correction, and providing data security. Note: A single coding scheme usually does not provide more than one or two specific capabilities. Different codes have different advantages and disadvantages. 2. In communications and computer systems, implementing rules that are used to map the elements of one set onto the elements of another set, usually on a one-to-one basis. 3. The digital encoding of an analog signal and, conversely, decoding to an analog signal.

Coding Scheme - Synonym code. A set of rules that maps the elements of one set, the coded set, onto the elements of another set, the code element set

Coherent - Pertaining to a fixed phase relationship between corresponding points on an electromagnetic wave. Note: A truly coherent wave would be perfectly coherent at all points in space. In practice, however, the region of high coherence may extend over only a finite distance.

Collective Address - Synonym group address. In a communications network, a predefined address used to address only a specified set of users.

Collocation - is moving or placing things together, sometimes implying a proper order. On the Internet, this term (often spelled "colocation" or "co-location") is used to mean the provision of space for a customer's telecommunications equipment on the service provider's premises. For example, a Web site owner could place the site's own computer servers on the premises of the Internet service provider (ISP). Or an ISP could place its network routers on the premises of the company offering switching services with other ISPs. The alternative to collocation is to have the equipment and the demarcation point located at the customer's premises.

Collocation is sometimes provided by companies that specialize in Web site hosting.

Color Burst - In analog color television technology, a signal consisting of several (8 to 10 in NTSC) cycles of unmodulated color subcarrier, superimposed at a specified location within the composite signal. Note: The color burst (a) enables the color-decoding circuits in the receiver, and (b) serves as an amplitude, frequency, and phase reference to which the local color (subcarrier frequency) oscillator in the receiver is phase-locked to ensure color fidelity and stability in the displayed picture.

Color Coordinate Transformation - Computation of the tristimulus values of colors in terms of one set of primaries. Note: This computation may be performed electrically in a color television system.

Color Keying - Synonym chroma keying. - In television, nearly instantaneous switching between multiple video signals, based on the state, i.e., phase, of the color (chroma) signal of one, to form a single composite video signal. Note 1: Chroma keying is used to create an overlay effect in the final picture, e.g., to insert a false background, such as a weather map or scenic view, behind the principal subject being photographed. Note 2: The principal subject is photographed against a background having a single color or a relatively narrow range of colors, usually in the blue or green. When the phase of the chroma signal corresponds to the preprogrammed state or states associated with the background color, or range of colors, behind the principal subject, the signal from the alternate, i.e., false, background is inserted in the composite signal and presented at the output. When the phase of the chroma signal deviates from that associated with the background color(s) behind the principal subject, video associated with the principal subject is presented at the output.

Color Subcarrier - In analog color television technology, a signal superimposed upon the picture (gray scale) information for the purpose of conveying the associated color information. Note: The color information is conveyed by the instantaneous phase of the color subcarrier with respect to that of the color burst.

.com - 1. A top-level domain name-suffix originally intended to designate commercial entities such as corporations and companies. 2. A filename suffix indicating an executable file. Note: Usually, ".com" programs are smaller and simpler than programs with the ".exe" suffix.

Combinational Logic Element - A device having at least one output channel and one or more input channels, all characterized by discrete states, such that at any instant the state of each output channel is completely determined by the states of the input channels at the same instant.

Command - 1. An order for an action to take place. 2. In data transmission, an instruction sent by the primary station instructing a secondary station to perform some specific function. 3. In signaling systems, a control signal. 4. In computer programming, that part of a computer instruction word that specifies the operation to be performed. 5. Loosely, a mathematical or logic operator.

Command and Control (C2): The exercise of authority and direction by a properly designated commander over assigned forces in the accomplishment of the mission. Command and control functions are performed through an arrangement of personnel, equipment, communications, facilities, and procedures employed by a commander in planning, coordinating, and controlling forces and operations in the accomplishment of the mission.

Command Communications - Former manufacturer of telephone line sharing devices, fax switches, on-premise paging systems, and HDMI cables and switches. Command Communications was founded in the 1980s and closed all operations in 2011. Popular fax switch products were the ASAP 102, ASAP 103, ASAP 104, ASAP 203, ComShare 350, ComSwitch 350, ComShare 450, ComShare 550, ComShare 650, ComShare 750, Command ASAP DR 401, Comswitch CS3.0, Comswitch 5500, Comswitch 7500, Comswitch 3500, and Comswitch 300.

• Replacement for Comswitch ASAP 102
• Replacement for Comswitch ASAP 103
• Replacement for Comswitch ASAP 104
• Replacement for Comswitch ASAP 203
• Replacement for Comswitch CS3.0
• Replacement for ComShare 300
• Replacement for ComSwitch 350
• Replacement for Comswitch 3500
• Replacement for Command ASAP DR 401
• Replacement for ComShare 450
• Replacement for ComShare 550
• Replacement for Comswitch 5500
• Replacement for Comshare 5500
• Replacement for Comshare 650
• Replacement for Comswitch 7500
• Replacement for ComShare 7500
• Alternatives for Comswitch Products.
• Line Routing Switch - Auto Call Processing
• LRS-LINESHARE 41 - Automatic Call Processing for phones, fax, & modems
• Line Routing Switch PRO ™
• Command ASAP104 Fax Switch - Command Communications
• CS5500 Fax Switch (4 Port) - Command Communications
• CS7500 Fax Switch (4 Port) - Command Communications

Command, Control and Communications (C3) - The capabilities required by commanders to exercise command and control of their forces.

Common Carrier - In a telecommunications context, a telecommunications company that holds itself out to the public for hire to provide communications transmission services. Note: In the United States, such companies are usually subject to regulation by Federal and state regulatory commissions. Synonyms carrier, commercial carrier, communications common carrier, [and, loosely] interexchange carrier.

Common-Channel Signaling - 1. In a multichannel communications system, signaling in which one channel in each link is used for signaling to control, account for, and manage traffic on all channels of the link. Note: The channel used for common-channel signaling does not carry user information. 2. A signaling method in which a single channel conveys, by means of labeled messages, signaling information relating to a multiplicity of circuits or calls and other information, such as that used for network management.

Common Control - An automatic switching arrangement in which the control equipment necessary for the establishment of connections is shared by being associated with a given call only during the period required to accomplish the control function for the given call. Note: In common control, the channels that are used for signaling, whether frequency bands or time slots, are not used for message traffic.

Common Gateway Interface - See CGI. A means for allowing programs or scripts (usually written in C++ or Perl) to add functionality to the World Wide Web. Note: Examples are search engines, feedback forms, and guestbooks.

Common User Network - A system of circuits or channels allocated to furnish communication paths between switching centers to provide communication service on a common basis to all connected stations or subscribers. It is sometimes described as a general purpose network.

Communications - 1. Information transfer, among users or processes, according to agreed conventions. 2. The branch of technology concerned with the representation, transfer, interpretation, and processing of data among persons, places, and machines. Note: The meaning assigned to the data must be preserved during these operations.

Communications Center - 1. An agency charged with the responsibility for handling and controlling communications traffic. The center normally includes message center, transmitting, and receiving facilities. 2. A facility that (a) serves as a node for a communications network, (b) is equipped for technical control and maintenance of the circuits originating, transiting, or terminating at the node, (c) may contain message-center facilities, and (d) may serve as a gateway. Synonyms comm center, message center.

Communications Channel - See channel. - 1. A connection between initiating and terminating nodes of a circuit. 2. A single path provided by a transmission medium via either (a) physical separation, such as by multipair cable or (b) electrical separation, such as by frequency- or time-division multiplexing. 3. A path for conveying electrical or electromagnetic signals, usually distinguished from other parallel paths. 4. Used in conjunction with a predetermined letter, number, or codeword to reference a specific radio frequency. 5. The portion of a storage medium, such as a track or a band, that is accessible to a given reading or writing station or head. 6. In a communications system, the part that connects a data source to a data sink. 7. A virtual area where Internet Relay Chat (IRC) users communicate (exchanging text messages) in real time. Note: There are thousands of channels located on the Internet. 8. An IRC conduit designated for the real-time exchange of text messages. 9. An electrical path suitable for the transmission of communications between two or more points, ordinarily between two or more stations or between channel terminations in Telecommunication Company central offices. A channel may be furnished by wire, fiber optics, radio or a combination thereof. 10. The portion of the electromagnetic spectrum assigned by the FCC for one emission. In certain circumstances, however, more than one emission may be transmitted on a channel.

Communications Common Carrier - 1. The term "communications common carrier" as used in this part means any person (individual, partnership, association, joint-stock company, trust, corporation, or other entity) engaged as a common carrier for hire, in interstate or foreign communication by wire or radio or in interstate or foreign radio transmission of energy, including such carriers as are described in subsection 2(b) (2) and (3) of the Communications Act of 1934, as amended, and, in addition, for purposes of subpart H of this part, includes any individual, partnership, association, joint-stock company, trust, corporation, or other entity which owns or controls, directly or indirectly, or is under direct or indirect common control with, any such carrier. 2. Any person engaged in rendering communication service for hire to the public. Synonym common carrier.

Communications Intelligence (COMINT) - Technical and intelligence information derived from foreign communications by other than the intended recipients.

Communications Net - An organization of stations capable of direct communication on a common channel or frequency. Synonym net.

Communications Network - An organization of stations capable of intercommunications, but not necessarily on the same channel.

Communications Security (COMSEC) - Measures and controls taken to deny unauthorized persons information derived from telecommunications and to ensure the authenticity of such telecommunications. Note: Communications security includes cryptosecurity, transmission security, emission security, and physical security of COMSEC material. [INFOSEC]

• (a) cryptosecurity: [The] component of communications security that results from the provision of technically sound cryptosystems and their proper use. [NIS]
• (b) emission security: Protection resulting from all measures taken to deny unauthorized persons information of value which might be derived from intercept and analysis of compromising emanations from crypto-equipment, AIS, and telecommunications systems. [NIS]
• (c) physical security: The component of communications security that results from all physical measures necessary to safeguard classified equipment, material, and documents from access thereto or observation thereof by unauthorized persons. [JP 1-02]
• (d) transmission security: [The] component of communications security that results from the application of measures designed to protect transmissions from interception and exploitation by means other than cryptanalysis.

Communications System - A collection of individual communications networks, transmission systems, relay stations, tributary stations, and data terminal equipment (DTE) usually capable of interconnection and interoperation to form an integrated whole. Note: The components of a communications system serve a common purpose, are technically compatible, use common procedures, respond to controls, and operate in unison.

Compact - See data compaction.

Compact Disc - Known by its abbreviation, CD, a compact disc is a polycarbonate with one or more metal layers capable of storing digital information. The most prevalent types of compact discs are those used by the music industry to store digital recordings and CD-ROMs used to store computer data. Both of these types of compact disc are read-only, which means that once the data has been recorded onto them, they can only be read, or played.

Competitive Local Exchange Carrier - A telephone company that competes with the larger incumbent carriers (ILECs) through reselling the ILEC services and/or creating services that use the ILEC's infrastructure. The Regional Bells are ILECs; local phone companies are frequently CLECs.

Compile - 1. To translate a computer program expressed in a high-level language into a program expressed in a lower level language, such as an intermediate language, assembly language, or a machine language. 2. To prepare a machine language program from a computer program written in another programming language by making use of the overall logic structure of the program or by generating more than one computer instruction for each symbolic statement as well as performing the function of an assembler.

Component - 1. An assembly, or part thereof, that is essential to the operation of some larger assembly and is an immediate subdivision of the assembly to which it belongs. Note: For example, a radio receiver may be a component of a complete radio set consisting of a combined transmitter-receiver, i.e., a transceiver. The same radio receiver could also be a subsystem of the combined transmitter-receiver, in which case the IF amplifier section would be a component of the receiver but not of the radio set. Similarly, within the IF amplifier section, items, such as resistors, capacitors, vacuum tubes, and transistors, are components of that section. 2. In logistics, a part, or combination of parts having a specified function, that can only be installed or replaced as an entity. 3. In material, an assembly or any combination of parts, subassemblies, and assemblies mounted together in manufacture, assembly, maintenance, or rebuild.

Component Video - Also known as "Y Pb Pr," this connector splits the video signal into three parts. With two audio connections, this five-wire solution is the most common way to connect an EDTV to DVD player and most HDTV monitors to their receivers or other set-top boxes.

Composite Color - The structure of a video signal wherein the luminance and two bandlimited color-difference signals are simultaneously present in the channel. Note: The format may be achieved by frequency-division multiplexing, quadrature modulation, etc. It is common to strive for integrity by suitable separation of the frequencies, or since scanned video signals are highly periodic, by choosing frequencies such that the chrominance information is interleaved within spectral regions of the luminance signal wherein a minimum of luminance information resides.

Composite Video - 1. See composite video signal. - The electrical signal that represents complete color picture information and all synchronization signals, including blanking and the deflection synchronization signals to which the color synchronization signal is added in the appropriate time relationship. 2. Also called "RCA" connectors, it is the most common way to connect peripherals and other components. It consists of one yellow connector for video and two audio connectors for "right" and "left." Composite connectors cannot transmit high-definition pictures. This means that, for HDTV, another connector option — such as HDMI or Component Video — must be employed.

Composite Video Signal - The electrical signal that represents complete color picture information and all synchronization signals, including blanking and the deflection synchronization signals to which the color synchronization signal is added in the appropriate time relationship. Synonym composite video.

Compression - 1. See data compression, signal compression. VoIP uses various compression ratios, the highest approximately 12:1. Compression varies according to available bandwidth. 2. Term that refers to the reduction of the size of digital data files by removing redundant and/or non-critical information ("data" being the elements of video, audio and other "information"). DTV in the U.S. would not be possible without compression.

Compromise - 1. The known or suspected exposure of clandestine personnel, installations, or other assets or of classified information or material, to an unauthorized person. 2. The disclosure of cryptographic information to unauthorized persons. 3. The recovery of plain text of encrypted messages by unauthorized persons through cryptanalysis methods. 4. Disclosure of information to unauthorized persons or a violation of the security policy of a system in which unauthorized intentional or unintentional disclosure, modification, destruction, or loss of an object may have occurred.

Compromising Emanations - Unintentional signals that, if intercepted and analyzed, would disclose the information transmitted, received, handled, or otherwise processed by information systems equipment.

Computer - 1. A device that accepts data, processes the data in accordance with a stored program, generates results, and usually consists of input, output, storage, arithmetic, logic, and control units. 2. A functional unit that can perform substantial computation, including numerous arithmetic operations or logic operations, without human intervention during a run. Note 1: This definition, approved by the Customs Council, distinguishes a computer from similar devices, such as hand-held calculators and certain types of control devices. Note 2: Computers have been loosely classified into microcomputers, minicomputers, and main-frame computers, based on their size. These distinctions are rapidly disappearing as the capabilities of even the smaller units have increased. Microcomputers now are usually more powerful and versatile than the minicomputers and the main-frame computers were a few years ago.

Computer Conferencing - 1. Teleconferencing supported by one or more computers. 2. An arrangement in which access, by multiple users, to a common database is mediated by a controlling computer. 3. The interconnection of two or more computers working in a distributed manner on a common application process.

Computer Graphics - 1. Graphics implemented through the use of computers. 2. Methods and techniques for converting data to or from graphic displays via computers. 3. The branch of science and technology concerned with methods and techniques for converting data to or from visual presentation using computers.

Computer Input - This term refers to an input feature on some HDTV sets (like SVGA or VGA) that allows TV sets to be connected to computers.

Computer Network - 1. A network of data processing nodes that are interconnected for the purpose of data communication. 2. A communications network in which the end instruments are computers.

Computer-Oriented Language - A programming language in which words and syntax are designed for use on a specific computer or class of computers. Synonyms low-level language, machine-oriented language.

Computer Program - See program. - 1. A plan or routine for solving a problem on a computer. Note: Processing may include the use of an assembler, a compiler, an interpreter, or a translator to prepare the program for execution, as well as the execution of the program. The sequence of instructions may include statements and necessary declarations. 2. A sequence of instructions used by a computer to do a particular job or solve a given problem. 3. To design, write, and test programs.

Computer Security (COMPUSEC) - 1. Measures and controls that ensure confidentiality, integrity, and availability of information-system (IS) assets including hardware, software, firmware, and information being processed, stored, and communicated. Synonym automated information systems security. 2. The application of hardware, firmware and software security features to a computer system in order to protect against, or prevent, the unauthorized disclosure, manipulation, deletion of information or denial of service. 3. The protection resulting from all measures to deny unauthorized access and exploitation of friendly computer systems.

Computer Science - The study of computers, including both hardware and software design. Computer science is composed of many broad disciplines, including artificial intelligence and software engineering. Most universities now offer bachelor, master, and doctorate degrees in computer science.

Computer Word - In computing, a group of bits or characters that occupies one or more storage locations and is treated by computers as a unit. Synonym machine word.

Compression - The reduction in size of data in order to save space or transmission time. For data transmission, compression can be performed on just the data content or on the entire transmission unit (including header data) depending on a number of factors.

Content compression can be as simple as removing all extra space characters, inserting a single repeat character to indicate a string of repeated characters, and substituting smaller bit strings for frequently occurring characters. This kind of compression can reduce a text file to 50% of its original size. Compression is performed by a program that uses a formula or algorithm to determine how to compress or decompress data.

Graphic image file formats are usually designed to compress information as much as possible (since these can tend to become very large files). Graphic image compression can be either lossy (some information is permanently lost) or lossless (all information can be restored).

When you send or receive information on the Internet, larger text files, either singly or with others as part of an archive file, may be transmitted in a zip, gzip, or other compressed format. WinZip is a popular Windows program that compresses files when it packages them in an archive.

COMSEC - Acronym for communications security.

COMSEC material: [An] item designed to secure or authenticate telecommunications. Note: COMSEC material includes, but is not limited to, key, equipment, devices, documents, firmware or software that embodies or describes cryptographic logic and other items that perform COMSEC functions.

Conference Controller - In audio and video teleconferences, the user in charge of the conference when the service is invoked and the conference reaches the active state. Note: The conference controller may perform any or all of the following actions: drop, floating, isolate, reattach, and split.

Configuration Management - 1. [The] management of security features and assurances through control of changes made to hardware, software, firmware, documentation, test, test fixtures, and test documentation throughout the life cycle of an information system (IS). 2. The control of changes--including the recording thereof--that are made to the hardware, software, firmware, and documentation throughout the system life cycle.

Congestion - 1. In a communications switch, a state or condition that occurs when more subscribers attempt simultaneously to access the switch than it is able to handle, even if unsaturated. 2. In a saturated communications system, the condition that occurs when an additional demand for service occurs.

Connection - In telecommunication and computing in general, a connection is the successful completion of necessary arrangements so that two or more parties (for example, people or programs) can communicate at a long distance. In this usage, the term has a strong physical (hardware) connotation although logical (software) elements are usually involved as well.

A dialup (sometimes called a switched) connection is a telephonic arrangement that is set up only when needed, using shared, circuit-switched communication lines (as in "plain old telephone service"). A dedicated (sometimes called a nonswitched) connection is a continuous, always available connection (familiar to users of Digital Subscriber Line or DSL service). A leased line is a line rented from a telephone company that provides dedicated connection between two points (such as a headquarters office and a manufacturing plant).

Connection - 1. A provision for a signal to propagate from one point to another, such as from one circuit, line, subassembly, or component to another. 2. An association established between functional units for conveying information. 3. A temporary concatenation of transmission channels or telecommunication circuits, switching and other functional units set up to provide a route for a transfer of information between two or more points in a telecommunication network.

Connectionless Data Transfer - See connectionless mode transmission.

Connectionless Mode Transmission - 1. In a packet-switched network, transmission in which each packet is encoded with a header containing a destination address sufficient to permit the independent delivery of the packet without the aid of additional instructions. Note 1: A packet transmitted in a connectionless mode is frequently called a datagram. Note 2: In connectionless mode transmission of a packet, the service provider usually cannot guarantee there will be no loss, error insertion, misdelivery, duplication, or out-of-sequence delivery of the packet. However, the risk of these hazards' occurring may be reduced by providing a reliable transmission service at a higher protocol layer, such as the Transport Layer of the Open Systems Interconnection--Reference Model. 2. The transmission of a unit of data in a single self-contained operation without establishing, maintaining, and releasing a connection.

Connectivity - The technical communications link between a computer system and the Internet.

Connector - A device for mating and demating electrical power connections or communications media. Note: A connector is distinguished from a splice, which is a permanent joint.

Connect Signal - An off-hook condition applied to the network interface (NI) by the network that indicated the network intends to complete a call attempt to the customer installation (CI) or intends to continue an established connection .

Contamination - The introduction of data of one security [classification or] security category into data of a lower security classification or different security category.

Content Hosting (hosting) - Storage and management of databases by a content provider.

Content Provider - An organization that creates and maintains databases containing information from an information provider. Note: The content provider and the information provider may be the same organization.

Control Character - A character that initiates, modifies, or stops a function, event, operation, or control operation. Note: Control characters may be recorded for use in subsequent actions. They are not graphic characters but may have a graphic representation in some circumstances.

Control Function - Synonym control operation. - An operation that affects the recording, processing, transmission, or interpretation of data. Note: Examples of control operations include starting and stopping a process; executing a carriage return, a font change, or a rewind; and transmitting an end-of-transmission (EOT) control character.

Control Operation - An operation that affects the recording, processing, transmission, or interpretation of data. Note: Examples of control operations include starting and stopping a process; executing a carriage return, a font change, or a rewind; and transmitting an end-of-transmission (EOT) control character. Synonym control function.

Controller - In an automated radio, the device that commands the radio transmitter and receiver, and that performs processes, such as automatic link establishment, channel scanning and selection, link quality analysis, polling, sounding, message store and forward, address protection, and anti-spoofing.

Converter Box - Also referred to as a “digital-to-analog converter box,” this is a stand-alone device that receives, decodes, and converts over-the-air digital programming into analog. When connected to an analog television, it permits digital programming to be displayed in analog.

Cookie -1. A small piece of information that is automatically stored on a client computer by a Web browser and referenced to identify repeat visitors to a Web site and to tailor information in anticipation of the visitor's interests. Note: Some privacy advocates have objected to the use of cookies without a user's consent. 2. A general mechanism that server side connections (such as CGI scripts) can use both to store and to retrieve information on the client side of the connection. Note 1: A server, when returning an HTTP object to a client, may also send a piece of state information that the client will store. Included in that state object is a description of the range of URLs for which that state is valid. Any future HTTP requests made by the client that fall in that range will include a transmittal of the current value of the state object from the client back to the server. The state object is called a cookie. This simple mechanism provides a tool that enables new types of applications to be written for Web-based environments. Shopping applications can now store information about the currently selected items, for-fee services can send back registration information and free the client from retyping a user ID on subsequent connections, sites can store per-user preferences on the client, and have the client supply those preferences every time that site is accessed. Note 2: Session cookies are volatile in that they disappear at the end of a session, whereas persistent cookies are retained from one session to the next. Synonym magic cookie.

Coordinated Universal Time (UTC) - Time scale based on the second (SI), as defined and recommended by the CCIR, and maintained by the Bureau International des Poids et Mesures (BIPM). For most practical purposes associated with the Radio Regulations, UTC is equivalent to mean solar time at the prime meridian (0° longitude), formerly expressed in GMT. Note 1: The maintenance by BIPM includes coordinating inputs from time standards belonging to various national laboratories around the world, which inputs are averaged to create the international time standard (second). Note 2: The full definition of UTC is contained in CCIR Recommendation 460-4. Note 3: The second was formerly defined in terms of astronomical phenomena. When this practice was abandoned in order to take advantage of atomic resonance phenomena (" atomic time ") to define the second more precisely, it became necessary to make occasional adjustments in the "atomic" time scale to coordinate it with the workaday mean solar time scale, UT-1, which is based on the somewhat irregular rotation of the Earth. Rotational irregularities usually result in a net decrease in the Earth's average rotational velocity, and ensuing lags of UT-1 with respect to UTC. Note 4: Adjustments to the atomic, i.e., UTC, time scale consist of an occasional addition or deletion of one full second, which is called a leap second. Twice yearly, during the last minute of the day of June 30 and December 31, Universal Time, adjustments may be made to ensure that the accumulated difference between UTC and UT-1 will not exceed 0.9 s before the next scheduled adjustment. Historically, adjustments, when necessary, have usually consisted of adding an extra second to the UTC time scale in order to allow the rotation of the Earth to "catch up." Therefore, the last minute of the UTC time scale, on the day when an adjustment is made, will have 61 seconds. Synonyms World Time, Z Time, Zulu Time.

Copy - 1. To receive a message. 2. A recorded message or a duplicate of it. 3. To read data from a source, leaving the source data unchanged at the source, and to write the same data elsewhere, though they may be in a physical form that differs from that of the source. 4. To understand a transmitted message.

Core - 1. The central region about the longitudinal axis of an optical fiber, which region supports guiding of the optical signal. Note 1: For the fiber to guide the optical signal, the refractive index of the core must be slightly higher than that of the cladding. Note 2: In different types of fibers, the core and core-cladding boundary function slightly differently in guiding the signal. Especially in single-mode fibers, a significant fraction of the energy in the bound mode travels in the cladding. 2. A piece of ferromagnetic material, usually toroidal in shape, used as a component in a computer memory device. Note: The type of memory referred to has very limited application in today's computer environment. It has been largely replaced by semiconductor and other technologies. 3. The material at the center of an electromechanical relay or solenoid, about which the coil is wound.

Core Diameter - In the cross section of a realizable optical fiber, ideally circular, but assumed to a first approximation to be elliptical, the average of the diameters of the smallest circle that can be circumscribed about the core-cladding boundary, and the largest circle that can be inscribed within the core-cladding boundary.

Corrective Maintenance - 1. Maintenance actions carried out to restore a defective item to a specified condition. 2. Tests, measurements, and adjustments made to remove or correct a fault.

Corresponding Entities - Peer entities with a lower layer connection among them.

Cosmic Noise - Random noise that originates outside the Earth's atmosphere. Note: Cosmic noise characteristics are similar to those of thermal noise. Cosmic noise is experienced at frequencies above about 15 MHz when highly directional antennas are pointed toward the Sun or to certain other regions of the sky such as the center of the Milky Way Galaxy. Synonym galactic radio noise.

Contention - 1. A condition that arises when two or more data stations attempt to transmit at the same time over a shared channel, or when two data stations attempt to transmit at the same time in two-way alternate communication. Note: A contention can occur in data communications when no station is designated a master station. In contention, each station must monitor the signals and wait for a quiescent condition before initiating a bid for master status. 2. Competition by users of a system for use of the same facility at the same time. Synonym access contention.

Coupling - The desirable or undesirable transfer of energy from one medium, such as a metallic wire or an optical fiber, to another like medium, including fortuitous transfer. Note: Examples of coupling include capacitive (electrostatic) coupling, inductive (magnetic) coupling, conducted (resistive or hard-wire) coupling, and fiber-optic coupling.

Coupling Loss - 1. The loss that occurs when energy is transferred from one circuit, circuit element, or medium to another. Note: Coupling loss is usually expressed in the same units--such as watts or dB--as in the originating circuit element or medium. 2. In fiber optics, the power loss that occurs when coupling light from one optical device or medium to another.

CPE - (see Customer Premises Equipment)

CPNI (Customer Proprietary Network Information)- Information that telecommunications services such as local, long distance, and wireless telephone companies acquire about their subscribers. It includes not only what services they use but their amount and type of usage. The Telecommunications Act of 1996 together with clarifications from the Federal Communications Commission (FCC) generally prohibits the use of that information without customer permission, even for the purpose of marketing the customers other services . In the case of customers who switch to other service providers, the original service provider is prohibited from using the information to try to get the customer back. CPNI includes such information as optional services subscribed to, current charges, directory assistance charges, usage data, and calling patterns.

The CPNI rules do not prohibit the gathering and publishing of aggregate customer information nor the use of customer information for the purpose of creating directories.

Cramming – An illegal practice in which customers are billed for additional telephone features they didn't’t order.

Crawler - Synonyms droid, Web crawler, Web spider.

Critical Frequency - 1. In radio propagation by way of the ionosphere, the limiting frequency at or below which a wave component is reflected by, and above which it penetrates through, an ionospheric layer. 2. At vertical incidence, the limiting frequency at or below which incidence, the wave component is reflected by, and above which it penetrates through, an ionospheric layer. Note: The existence of the critical frequency is the result of electron limitation, i.e., the inadequacy of the existing number of free electrons to support reflection at higher frequencies.

Cropping - When viewing widescreen format on an analog TV, the picture is cropped — i.e., black bars appear above, below, and on either side of the picture. This is done to maintain the original aspect ratio of the original picture source.

Cross-Connect: Synonym cross-connection.

Cross-Connection: Connections between terminal blocks on the two sides of a distribution frame, or between terminals on a terminal block. Note: Connections between terminals on the same block are also called straps. Synonyms cross-connect, jumper.

Cross Coupling - The coupling of a signal from one channel, circuit, or conductor to another, where it is usually considered to be an undesired signal.

Crosstalk (XT) - 1. Undesired coupling of a signal from one circuit, part of a circuit, or channel, to another. 2. Any phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel. Note 1: In telephony, crosstalk is usually distinguishable as speech or signaling tones. Note 2: In video, "ghost" images from one source appear in addition to the signals of interest transmitted from another.

CRT- Cathode Ray Tube. Display screens used in TV sets and computer monitors that use a Cathode Ray Tube, which is also called a "picture tube." Cathode Ray Tubes were found in all electronic television sets up until the invention of the less bulky LCD screens.

Cryptanalysis - 1. Operations performed in converting encrypted messages to plain text without initial knowledge of the crypto-algorithm and/or key employed in the encryption. 2. The study of encrypted texts.

CRYPTO - The marking or designator identifying COMSEC keying material used to secure or authenticate telecommunications carrying classified or sensitive U.S. Government or U.S. Government-derived information. Note: When written in all upper case letters, CRYPTO has the meaning stated above. When written in lower case as a prefix, crypto and crypt are abbreviations for cryptographic.

Crypto-Algorithm - [A] well-defined procedure or sequence of rules or steps, or a series of mathematical equations used to describe cryptographic processes such as encryption/decryption, key generation, authentication, signatures, etc.

Crypto-Equipment - See cryptographic equipment. - Any device that embodies cryptographic logic or performs one or more cryptographic functions (e.g., key generation, encryption, and authentication).

Cryptology - 1. The science that deals with hidden, disguised, or encrypted communications. It includes communications security and communications intelligence. 2. [The] field encompassing both cryptography and cryptanalysis.

Cryptographic - Pertaining to, or concerned with, cryptography.

Cryptographic Equipment (crypto-equipment) - Any device that embodies cryptographic logic or performs one or more cryptographic functions (e.g., key generation, encryption, and authentication).

Cryptographic Logic - The embodiment of one (or more) crypto-algorithm (s) along with alarms, checks, and other processes essential to effective and secure performance of the cryptographic process(es).

Cryptography - 1. [The] art or science concerning the principles, means, and methods for rendering plain information unintelligible, and for restoring encrypted information to intelligible form. 2. The branch of cryptology that treats of the principles, means, and methods of designing and using cryptosystems.

Cryptosecurity - See communications security. [The] component of communications security that results from the provision of technically sound cryptosystems and their proper use.

CSSR – Customer Sales and Service Representative. These TDS Telecom employees work in the sales and service offices of our local operating companies. They answer customer questions, market services, and handle payments.

CST – Customer Service Technician. These TDS Telecom employees work in our local operating companies and provide installation and repair service for our customers.

CTI ( computer-telephony integration, or sometimes simply "computer telephony") - is the use of computers to manage telephone calls. The term is used in describing the computerized services of call centers, such as those that direct your phone call to the right department at a business you're calling. It's also sometimes used to describe the ability to use your personal computer to initiate and manage phone calls (in which case you can think of your computer as your personal call center).

CTI applications provide the ability to do one or more of the following:

• Authenticate callers. Using one of several standard methods, the telephone number of the caller can be screened against a database.
• Recognize a voice, either for authentication or for message forwarding
• Using live, recorded voice, or touch-tone entered input, determine how to process a call (for example, by forwarding it to the appropriate person or department)
• Provide interactive voice response (IVR) to callers
• Match the number of a caller with a customer record and display it for reference when talking to the caller
• Manage voice or video conferences
• Collect and display pending live calls or messages that have been left by callers
• Receive fax messages and route them to appropriate fax machines
• For outbound calling such as telemarketing, predial callers
• Based on call input, initiate a smart agent application to provide help with the caller's request

The Advanced Intelligent Network (AIN) is a telephone service architecture that separates CTI services from call switching and will make it easier to add new services. The Windows Telephony Application Program Interface (TAPI) and Novell's TSAPI are programming interfaces intended to make it easier to create applications that enable telephone services on a personal computer or in a local area network.

Current - A flow of electrical charge carriers, usually electrons or electron-deficient atoms. The common symbol for current is the uppercase letter I. The standard unit is the ampere, symbolized by A. One ampere of current represents one coulomb of electrical charge (6.24 x 10¹⁸ charge carriers) moving past a specific point in one second. Physicists consider current to flow from relatively positive points to relatively negative points; this is called conventional current or Franklin current. Electrons, the most common charge carriers, are negatively charged. They flow from relatively negative points to relatively positive points.

Electric current can be either direct or alternating. Direct current (DC) flows in the same direction at all points in time, although the instantaneous magnitude of the current might vary. In an alternating current (AC), the flow of charge carriers reverses direction periodically. The number of complete AC cycles per second is the frequency, which is measured in hertz. An example of pure DC is the current produced by an electrochemical cell. The output of a power-supply rectifier, prior to filtering, is an example of pulsating DC. The output of common utility outlets is AC.

Current per unit cross-sectional area is known as current density. It is expressed in amperes per square meter, amperes per square centimeter, or amperes per square millimeter. Current density can also be expressed in amperes per circular mil. In general, the greater the current in a conductor, the higher the current density. However, in some situations, current density varies in different parts of an electrical conductor. A classic example is the so-called skin effect, in which current density is high near the outer surface of a conductor, and low near the center. This effect occurs with alternating currents at high frequencies. Another example is the current inside an active electronic component such as a field-effect transistor (FET).

An electric current always produces a magnetic field. The stronger the current, the more intense the magnetic field. A pulsating DC, or an AC, characteristically produces an electromagnetic field. This is the principle by which wireless signal propagation occurs.

Curvature Loss - In an optical fiber, that loss attributable to macrobending. - Synonym macrobend loss.

Customer Controlled Call Forwarding Busy - Allows you the capability to activate and deactivate call forwarding busy from your home telephone number using dial codes. Forwards calls to the number you have pre-selected. To activate, press 82#. To deactivate, press 83#.

Customer Controlled Call Forwarding No Answer - Allows you the capability to automatically forward unanswered incoming calls to another telephone number after a pre-selected number (2-7) of rings. Forwards calls to the number you have pre-selected. Activate this feature by pressing 77#. To deactivate, press 78#.

Customer Installation (CI) - All telecommunication equipment and wiring on the customer side of the network interface.

Customer Premises Equipment (CPE) - Telephone or other service provider equipment that is located on the customer's premises (physical location) rather than on the provider's premises or in between. Telephone handsets, cable TV set-top boxes, and Digital Subscriber Line routers are examples. Historically, this term referred to equipment placed at the customer's end of the telephone line and usually owned by the telephone company. Today, almost any end-user equipment can be called customer premise equipment and it can be owned by the customer or by the provider.

Custom Ring Service 1 - Allows you to receive calls dialed to two different telephone numbers without having a second access line. Distinctive ringing will be provided for the second telephone number to facilitate identification of incoming calls. One directory listing is provided for each Custom Ring number.

Custom Ring Service 2 - Allows you to receive calls dialed to three separate telephone numbers without having a second or third access line. Distinctive ringing will be provided for each of the additional telephone numbers to facilitate identification of incoming calls. One directory listing is provided for each Custom Ring number. You must have Custom Ring Service 1 to have Custom Ring Service 2.

Cutoff Wavelength - 1. The wavelength corresponding to the cutoff frequency. 2. In an uncabled single-mode optical fiber, the wavelength greater than which a particular waveguide mode ceases to be a bound mode. Note 1: The cutoff wavelength is usually taken to be the wavelength at which the normalized frequency is equal to 2.405. Note 2: The cabled cutoff wavelength is usually considered to be a more functional parameter because it takes into consideration the effects of cabling the fiber.

CXR ( cxr) - Abbreviation for carrier.

Cybermall - An electronic site shared by a number of commercial interests, and at which users can browse, shop, and place orders for the products listed at that site. [Bahorsky] Synonym Internet mall.

Cyberspace - The impression of space and community formed by computers, computer networks, and their users; the virtual "world" that Internet users inhabit when they are online.

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