ISDN is a technology that has the potential to revolutionise telecommunications the way the

chip revolutionised computing. But what exactly is ISDN and what can users get out of it?

This article discusses some of the exciting applications.

ISDN, or Integrated Services Digital Networking, has been hailed as the new type of information communications network.

ISDN allows the digital transmission of data, voice and video at high rates of speed over the same line. It is a totally new communications infrastructure that gives its users everything, from telephone calling to data transmission to image comm unications. ISDN can provide highquality data, voice, image and video services because it has the high-speed capacity to do so.

It uses three bands—two 64-kbps information bands called Base or B bands, and a single 19.2-kbps Data or band. Suffice it to say that ISDN provides communications speeds many times faster than the rate at which most people transmit faxes nowadays. But you might ask: “So what? Why do I need ISDN?”

One obvious benefit is that users of ISDN only need one network to do everything rather than having multiple networks- for different purposes.

Second, ISDN allows users to transfer high volumes of data faster than is now possible with conventional phone lines. For example, transferring the contents of a 1.4Mb floppy over a conventional longdistance line can take 20 to 40 minutes. With ISDN, the same data can be transferred in about 1.5 minutes.

Faster and better fax transmissions are possible. The new generation of Group IV faxes will be able to send and receive faxes six times faster, with better print quality, than conventional machines. However, be prepared to pay a premium for these machines—they cost around US$10,000 each.


Accessibility is another plus. Today, to connect computers via a phone line, users need modems to convert the digital signals of the computer to the analogue environment of conventional phone lines.

Also, the phone lines must be of sufficient capacity and quality to sustain computer communications. With ISDN, these will not be problems. People can “plug” their computers into any existing ISDN line. Modems will not be needed because a standard for digital transmission will exist.

Finally, high-quality voice communications and new services, such as the ability to display the number of a caller, are possible with ISDN. However, the really exciting benefits of ISDN are the new possibilities it provides in computer services.

ISDN will make it easier for users to combine video, voice and data on one machine, in one application, over remote facilities.

Multimedia applications have many practical uses. For example, engineers designing a component can prepare a written description of that part and add images to clarify any potential areas of confusion, that is, “what does the logo look like?”, and use video facilities to illustrate prototypes in motion.


Another advantage is that ISDN makes computer desktop videoconferencing possible.

I define computer desktop videoconferencing as the ability to use workstations currently used for computer applications to conduct face to face conversations remotely.

As prices for ISDN services decrease, ISDN becomes a cost-effective transport mechanism which will in turn make other services economically viable.

Electronic data interchange or EDI has been widely talked about. Acceptance of EDI has been relatively slow, in part because present transmission technology does not make EDI economically practical.

Sending large paper files electronically today can be very time consuming and costs money. ISDN, with its ability to rapidly send large volumes of data, will make EDI economically viable.

Furthermore, you could use your computer to do what you have to do manually. For example, with X.500, your computer in Hong Kong could ask the computer in New York to find Jones in the New York directory, retrieve the relevant entries and return them to you.

However, this potentially involves looking through and transmitting volumes of data. Since you want this done as rapidly as possible, transmission time must be minimized.

ISDN provides the communications backbone that allows you to send your inquiry and receive the response data quickly and economically. ISDN is becoming a reality and for once, Asia is not lagging but actually leading the world in this technology.

KDD in Japan has not one but several ISDN networks installed and running. ISDN products, such as videoconferencing systems suitable for home use, are now available in Japan.

In Singapore, commercial ISDN service is available. In Korea, the Korean Telecommunication Au^ thority (KTA), will commence ISDN trials early next year. In other areas, France, the UK and Germany are well advanced in ISDN technology.

The US, however, is lagging behind. There are few American ISDN users and sadly, very few American ISDN products although ISDN services are available from AT&T, GTE, Contel. among others.

Every generation or so, a technology comes along that causes a revolution. Not by what it does but by what it makes possible. ISDN is an exciting technology that makes a host of revolutionary computer services possible and the early starters will reap the benefits.

Timothy Regan

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