Telecom Dictionary Navigation

Telecom Dictionary - C

Cache - Generally, a place to temporarily store something. Regarding computers and telecommunications, it is a place where data is temporarily stored during transmission.

Call - This is a connection between two or more users with the intent of exchanging information.

Call Back - This is a security method with which a user calls into a system and requests to be called back by the system at a particular, predetermined number.

Caller - Anyone who makes a call.

Caller ID - The service that allows someone being called to see the caller's name and phone number.

Call Progress - This is the status of the telephone line. It can be busy, ringing, not ringing, etc.

Call Waiting - This is a service that tells you if someone is trying to call you when you are already using the line (i.e., talking with someone else).

Capacitor - This is an electronic device for storing electric charge.

Capture Effect - This effect occurs when two signals are received that are the same (or nearly the same) frequency. The stronger signal will appear in the output.

C-Band - The portion of the electromagnetic spectrum allotted for satellite transmission; it is the 4 to 8 GHz frequency transmission range. Specifically, the 3.7 to 4.2 GHz band is used as the downlink, and the 5.925 to 6.425 GHz band serves as the uplink.

Card - This term refers to a computer peripheral that can be connected internally (i.e., directly), without any cables, to a computer, such as a modem.

Caret - This is the character "^".

Carrier - This term refers to: (1) a company, such as a local telephone company, that provides circuits dedicated to communication, and (2) an electrical signal capable of being modulated to carry information.

Carrier Detect (CD) - This is a light on most modems that signifies, when lit, that the modem is connected.

Carrier Frequency - The main frequency on which data, a voice, or video signal is sent. Common microwave and satellite communications transmitters operate in the band from one to fourteen GHz.

Carrier Signal - The basic radio, television, or telephony center of a frequency transmission signal.

Cassegrain Antenna - An antenna that places a subreflector at the focal point to reflect energy to or from a feed located at the apex of the main reflector.

CB - This stands for Citizen's Band and is low-power (up to 4 Watts), public radio that does not require FCC approval.

CD - See Carrier Detect.

CDMA - This stands for Code Division Multiple Access and refers to a multiple-access scheme where stations use wide-spectrum modulations and orthogonal codes to reduce the chance of interfering with each other.

Central Office (CO) - This is a place where lines are joined to switching equipment (which control connections).

Channel - A frequency band, 6 MHz wide in the US, in which a specific broadcast signal is transmitted. Channel frequencies are determined in the US by the Federal Communications Commission (FCC).

Character - This is a letter, numeral, or symbol.

Characters per Second (CPS) - This is the number of characters that can be sent over the phone lines in 1 second.

Chat - A mode that allows two or more people to communicate with each other in real time over a network using modems.

Checksum - This is the sum of a group of data items that is used for error checking. Received information packets must have the same number of bits present during the initial transmission.

Chip - This is the physical structure of an integrated circuit.

Circuit - This is an electrical device that provides a path for electrical current to flow, or more generally, it is a journey or route all the way around a particular place or area.

Circular Polarization - Some satellites transmit both right-hand rotating and left-hand rotating signals simultaneously on the same frequency. This technique effectively doubles the channel carrying capacity of the satellite.

City Code - Some foreign countries require you to dial a city code before the phone number you are trying to reach.

Clamp - A circuit that removes the energy dispersal signal component from the video waveform.

Clarke Orbit - This is the circular orbit in space 22,237 miles from the surface of the earth at which geosynchronous satellites are placed to revolve around the earth. It is named after Arthur C. Clarke, who first postulated its existence. Satellites in these orbits move at speeds that cause their angular velocity to match the angular rate of the rotation of the earth, causing them to appear stationary when viewed from a particular point on Earth.

Clear to Send (CTS) - This is when a receiving modem tells the calling modem.

C/N (Carrier to Noise Ratio) - This is the carrier-to-noise-ratio, which is the ratio of the received carrier power to the noise power in a given bandwidth; it is expressed in decibels (dB), which is a logarithmic scale.

CO - See central office.

Codec - A coder/decoder system for transmitting digital data.

Color Subcarrier - A particular subcarrier that is added to the main video signal; its purpose is to convey the color information.

Columns - A column contains an item of data within a row.

Command - This is a software instruction that causes a specific job to be done.

Command Buffer - This is a memory place where commands are store temporarily.

Command Set - A collection of commands. (See Command.)

Commercial Internet (.com) - This is the part of the internet that is provided by commercial services, allowing business usage of the internet.

Common Carrier - Any organization which operates communications circuits used by other people. Common carriers include the telephone companies as well as communications satellite owners, AT&T and others.

Communication Channel - This is a type of circuit, and it is a two-way information pathway.

Communications Protocol - These are procedures used to ensure a standardized transmission occurs.

Compatible - When one object can be used interchangeably with another.

Composite Baseband - The unclamped and unfiltered output of the satellite receiver's demodulator circuit. It contains all of the video information as well as all transmitted subcarriers, such as the color subcarrier.

Compression - This occurs when information is reduced in size but all of the necessary information is retained.

Compression Ratio - This is the ratio of the original size of data that is sent to the compressed size.

Computer Network - See Network.

Configuration - This is the software or hardware arrangements that define a computer (or telecom system) and determine what actions will be carried out (and how).

Connected - This means you are online.

Connect Speed - Modem speed in bps.

Connection - A electrical pathway between telephones or similar devices.

Control Channel - With a cellular telephone system there are a few channels that allow the base stations to transmit information to the cell phones in its area.

Conus - This stands for Contiguous United States.

Copyright - This protects an author's work from being directly copied by another.

Country Code - This is the standardized code that designates a certain country.

Coverage Area - A geographical area that is defined by the coverage of a particular satellite.

CPS - See characters per second.

Crash - This is the complete failure of software or hardware operation. The only available option is to restart from an initial condition.

CRC - See Cyclic Redundancy Check.

Cross Modulation - A form of distortion in which modulation from one or more carriers' signals is imposed on another carrier's signal.

CRT - This stands for Cathode Ray Tub, and is a glass device used in video displays (e.g. televisions).

C/T - Carrier-to-noise-temperature ratio.

CTRL - This is the abbreviation for the ConTRoL key-command.

CTS - See Clear to Send.

Cursor - This is the particular marker that points out the next place the text will next appear on your screen.

Cyclic Redundancy Check (CRC) - This is a common process that is used to validate the integrity of a block of data.