ISDN

The Integrated Services Digital Network (ISDN) is a set of communications standards allowing a single wire or optical fibre to carry voice, digital network services and video. Originally developed in the mid 1980s, and widely available, its appeal has waned with the growth of broadband technology.

Basic-rate ISDN:ISDN primarily uses existing Public Switched Telephone Network (PSTN) switches and wiring, upgraded to provide all-digital end-to-end channels. ISDN channel is faster than dial-up access and two ISDN channels can be bonded together to provide an even faster connection.

The basic-rate ISDN service consists of two channels which effectively give you two separate telephone lines, enabling you to use one channel for voice and one for data. An ISDN channel is faster than dial-up access and two ISDN channels can be bonded together to provide an even faster connection. However, the use of each channel is charged separately and because you pay a higher call rate than with standard telephone lines, using "channel bonding" can be expensive.Because it is a digital system ISDN doesn't use modems. Instead a device called a Terminal Adapter provides the interface between the computer and the ISDN line.

Advantages of ISDN:Available to 97 per cent of the UK.Provides two digital channels as standard.Guaranteed data rates.Disadvantages of ISDN:Technically only "midband", ie faster than a modem but much slower than broadband.Not "always-on".Expensive, considering its speed.Generally requires on-site installation by an engineer