BT glossary - C

This glossary is here to help you understand some of the acronyms you may encounter in this site. Select a letter below that your word begins with.

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Abbreviation Term Definition


A memory storage device designed to speed up the operation of a computer. Pronounced cash.


Call centre

A purpose-built facility used by an organisation to facilitate making or receiving a large volume of calls. Because the purpose of these calls is predictable, computer assistance can be used and either designated agents or a voice processing application, or the two in combination, can complete the call.


Called ID

See Calling Line Identification.


Calling Line Identification

A mechanism whereby the number originating a telephone call is passed along with the call. The information allows the called party to know who is calling. In some cases callers can withhold display of their numbers.


Calling Line Identifier

The telephone number of the device originating a call.



While many of the broadband services offered by service providers impose no downloading limit or cap, some service providers have introduced a cap to enable them to offer services at lower cost. With a capped service, you may be required to pay a premium price if your downloads exceed your limit.



An organisation in the business of handling communications signals, frequently also a PTO (q.v.).



A bearer frequency onto which information signals are applied.



A fixed-length unit of data. ATM specifies a cell size of 53 bytes containing a 5-byte header and a 48-byte data portion.


Cellular radio

A radio-telephony system in which a network of transmitters links mobile users into the public phone system. Each transmitter or 'base station' serves a small area known as a cell.


Central Office

American term for telephone exchange.



Centralised extension service. A service provided from a reserved section of the main public exchange that has been reprogrammed to act as if it were the exclusive PBX of an individual user, in other words a 'virtual' PBX. There is no PBX equipment on the user's premises (saving space and outlay) and in-house calls are charged less than public network calls.



A form of credential, which binds an identity to a public key. A certificate will typically contain the subjects name, the subjects public key, the certificate issuer's name and digital signature, an expiry date and a serial number.


Certification Authority

A trusted entity that issues digital certificates.



A software program used to contact and obtain data from a server software program on another computer, often across a great distance. Each client program is designed to work with one or more specific kinds of server programs, and each server requires a specific kind of client. A web browser is a specific kind of client.



An architecture where tasks are broken down into distributed processes. The client is responsible for the presentation of the information and the server(s) for finding that required information. A data network connects clients to servers.


Closed-Circuit Television

A networked camera used for surveillance, process monitoring and other purposes.


Code Division Multiple Access



Code Division Multiple Access

A digital transmission technology for mobile radio, enabling more users to share the same radio channels.


Comit Consultatif Internationale des Tlphones et Tlgraphes

International Consultative Committee for telephones and telegraphs, now known as ITU-T. Main international standards body for the telecommunications industry.


Comit Europenne de Normalisation

European Standardisation Commission. Generates standards that have official status in the EC.


Comit Europenne de Normalisation Electronique

European Electrotechnical Commission. Sets up electronic ('electro-technical') standards for the EC and EFTA countries and has official status in EC.


Common Business Orientated Language

Many mainframe computer applications were once written in this programming language.


Common Gateway Interface

The Common Gateway Interface (CGI) allows a web server to interact with other computer programs. Many of these programs are written using interpreted scripting languages. They can be responsible for introducing security vulnerabilities into online services.


Community Of Interest Network

A COIN provides a way of giving members of a shared-interest community access to privileged information.


Competitive Access Provider

An American term to describe a business that connects telecomms users directly with long-distance carriers for voice, data and video transmission.


Computer-Based Training



Computer-Telephony Integration

Generally used to describe self-contained PC applications that add value to telephony.


Congestion Control

Rules that govern the way in which information will be discarded when a network becomes congested.


Connection oriented

A telecommunications service delivered using point-to-point connections that must be established before information can flow (e.g. a 'phone call').


Connectionless network

A way of communicating without having to have prior knowledge of the route the information will take (e.g. the postal system or the Internet).


Constant Bit Rate

An ATM (Asynchronous Transfer Mode) service equivalent to a Private Circuit.


Content management

A computer system that assists an online content provider in managing the information to be provided through its web site, enabling it to offer customers an up-to-date efficient service.



The most common meaning of 'cookie' on the Internet refers to a piece of information sent by a web server to a web browser that the browser software is expected to save and to send back to the server whenever the browser receives additional requests from the server. Depending on the type of cookie used, and the browser's settings, the browser may accept or not accept the cookie, and may save the cookie for either a short time or a long time. Cookies might contain information such as login or registration information, online 'shopping cart' information, user preferences, etc. When a server receives a request from a browser that includes a cookie, the server is able to use the information stored in the cookie. For example, the server might customise what is sent back to the user, or keep a log of particular user's requests. Cookies are usually set to expire after a predetermined amount of time and are usually saved in memory until the browser software is closed down, at which time they may be saved to disk if their 'expire time' has not been reached.



Someone who breaks into computers, usually for fun or political motives and occasionally (but rarely) for financial gain. Cracking is the act of breaking into computers, usually in order to steal something.



Computer software or accessory devices that will work with a variety of different computers.



The process of converting information into a secret code, called cipher text, by an encryption algorithm. Cryptographic services can provide confidentiality, integrity, authentication and non-repudiation. Shared/secret key (symmetric) cryptography uses the same key to encrypt and decrypt a message. Communication is limited to the two or more parties that share the secret). Public key (asymmetric) cryptography uses different keys for encryption and decryption. Each party has two keys, one private (kept secret) and one public (made available to everyone, often through a certification authority).


Customer Relationship Management

A computer system that assists an organisation in providing service to its customers. Typically, a CRM system allow call-centre agents, online applications and other services to access and update customer records and maintain details of purchases, fault reports and other dialogues.