What is it?
Integrated services digital network (ISDN) was effectively the first high speed digital telecoms standard for consumers and small businesses to carry voice, fax, data and video over normal telephone lines, writes Nick Langley.
But over the long period when it had no viable competitors, ISDN remained commercially under-available. The installation service was patchy, support poor, and prices high. When the rest of Europe got its ISDN act together, UK suppliers continued to neglect it, under-promoting it and charging fees often four times as much as Germany's, for example.
In the late 1990s ISDN support picked up, but faster and cheaper broadband technologies like ADSL (Asymmetric Digital Subscriber Line, which also uses phone lines) and cable were on the horizon. ISDN use is likely to peak this year.
BT will pay transfer costs from its ISDN to ADSL services, and claims savings could be more than £1,000 per line per year. But there has been considerable resistance: many ISDN users want to stay with the devil they know.
Where did it originate?
Development began in the early 1980s, and in 1992 ISDN was hailed as "the true beginning of the information age". But slow progress on standards, equipment and services meant this beginning was repeatedly postponed. ISDN has a promising future behind it.
What is it for?
One ISDN channel can carry 64 bits per second. It comes in two forms, basic rate ISDN (ISDN2) offering two 64-bit channels, and primary rate ISDN (ISDN30), with from eight to 30 channels. There is also broadband ISDN, which runs on fibre and is theoretically capable of 1.5mbps to 2mbps.
What makes it special?
The ability to carry digital information over old analogue lines. A small business using ISDN2 would be able to send data while simultaneously taking and making voice calls. It is also a relatively cheap and effective medium for videoconferencing.
ISDN is still the only option in areas where ADSL and cable are unavailable. ISDN uses equipment installed at the customer's premises, which means it is not dependent on what suppliers offer over the network.
How difficult is it?
One day's training for support staff, three days installation and troubleshooting instruction for experienced comms engineers.
Where is it used?
Although there is some consumer use, ISDN users tend to be small- to medium- sized businesses, and also schools and hospitals.
Not to be confused with...
...International Standard Book Numbers (ISBN), although you might be wise to order War and Peace while waiting for your ISDN equipment to be installed.
What does it run on?
Existing analogue phone lines and fibre.
Few people know that
During its long years in the wilderness, ISDN was said to stand for "It Still Does Nothing".
What is coming up?
Available at a price from service and equipment suppliers like BT and Cisco. There is also some free online, for example at www. Eicon.com/support/training
Rates of pay
ISDN is usually required as part of a portfolio of support or communications skills. Demand is likely to decline as broadband technologies like ADSL are adopted. From £18,000 to £28,000 for support; from £30,000 to £45,000 for network engineers.