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ISDN
ISDN, Integrated Services Digital Network, is an international standard for data, voice and video transfer over a digital telephone line.
Using ISDN equipment, a ‘call’ is made digital (converted into bits) from end to end, as opposed to a traditional analogue telephone call. The digitalisation means faster transfer speed. ISDN connections may use more than one line. These lines (so-called ‘channels’) can be open at the same time, allowing the user to transfer e.g. voice and data simultaneously, or simply to double their bandwidth to the Internet.
Basic ISDN connections provided by most telephone services consist of two main bearer-channels (the ‘B-channels’) which carry the data, etc., as well as an additional channel (the ‘D-channel’) which carries call-processing information. This basic ISDN configuration, known as ‘BRI’ (Basic Rate Interface), is suitable for individuals and small businesses. For larger organisations, however, a PRI (Primary Rate Interface) ISDN configuration may be appropriate. A PRI consists of up to 30 B-channels and a D-channel.
Related terms:
ADSL, CLI, Digital, E1, Frame Relay, Leased line, PPP, T1, X.25
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