BT glossary

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

Access control

Technique for limiting access to the resources of a system to authorised programs, processes, users or other systems.


Access control list

A list of authorised users, processes or systems. See access control.


Access network

The local cables which connect individual telephone users to the main network.



Technology developed by Microsoft, similar to a plug-in, which is most commonly used to add functionality to the internet explorer web browser. Once installed, an ActiveX program, called a control, becomes a permanent part of the machine's operating system and has unrestricted access to local machine resources.


Address spoofing

A type of attack in which the attacker impersonates a legitimate system by stealing its network address.


Advanced Encryption Standard

A competition is currently underway to define a public 256-bit symmetric encryption algorithm that will replace DES (Data Encryption Standard).


Advanced Research Projects Agency Network

The precursor to the internet. Developed in the late 60's and early 70's by the US Department of Defence as an experiment in wide-area-networking that would survive a nuclear war.



A name generally given to staff taking or making calls in a call centre. Also used to describe software programs that act autonomously on behalf of a user, for example performing searches for information that matches a users interests.


American National Standards Institute

An important International Standards Organisation member that develops and publishes industrial standards in computing and information technology, which are accepted world-wide.


American Standard Code for Information Interchange

The standard way of encoding characters into digital codes. An ASCII file is taken to mean a text file containing unformatted text that is, characters but not information about fonts, sizes and so on. ASCII files can be read by virtually every word-processing program.



A form of electrical transmission in which the signals transmitted are an exact replica of the original. Because analogue signals are prone to distortion, interference and error, they are normally digitised before being passed through switches and long-distance networks.


Analogue circuit

Older type of transmission which has a higher bit error rate than digital circuits.


Analogue to Digital

An interface at which analogue signals such as voice are converted into digital form for onward transmission across the trunk network.



Anti-spam protection software ensures that your email account doesn’t receive spam - emails sent to a large number of recipients. Spam emails are often advertisements and can come from dodgy companies that have bought your email address from a source without your consent.



Anti-virus software protects your computer against viruses or bugs - programs that install themselves on your hard-drive and are designed to corrupt your files or even ruin the set-up of your computer. The anti-virus software identifies the virus and stops it from installing on your computer. As there are new viruses developed every day, it is really important that your anti-virus protection is up to date.



An application program down loaded from a server that runs in a JAVA enabled web browser.



The proprietary network protocol designed for Apple LANs.



Any program you use on your computer, such as Microsoft Word or Excel.


Application Programming Interface

An interface to a computer operating system or software program that gives other programs access to functions similar to those offered to users through a graphical user interface.


Application Service Provider

A third-party business offering access to online software applications via the Internet.


Asymmetric Digital Subscriber Line

Allows information to be downloaded more quickly than it is uploaded. This makes it particularly suitable for internet surfing and for downloading files, music, pictures and sports clips. ADSL is ideal for home and small business use.


Asynchronous Transfer Mode

A network technology capable of carrying all types of telecommunications traffic. In effect, ATM combines circuit- and packet-switching technologies, synthesising the simplicity of the former with the flexibility of the latter, permitting high-speed transmission comparable with circuit switching.


ATM Adaptation Layer

The interface between services, such as voice, and the internal ATM switching protocol.


ATM Forum

A technical group, mainly of network equipment vendors, with the mission of setting pragmatic standards for ATM (Asynchronous Transfer Mode) communication systems.


Automatic Teller Machine

A machine that dispenses cash when you insert your bank card.