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ISDN and Computer-Based Fax

Living in a rapidly changing environment, it is far too easy to take for granted new technologies and the speed with which they advance. Not so long ago, people were very excited about PCs with no hard drives, 64 KB of memory, 8-bit processors, and no external communications links. Today, users demand PCs equipped with hard drives capable of storing billions of bits of information, megabits of RAM, 32- and 64-bit processors running at hundreds of megahertz, and 56 Kb/s or even broadband modems to stay connected round the clock. Over the years, consumers have became accustomed to continuous improvements in computer systems: hard drives and RAM provide higher capacity at lower cost; processors double their performance every other year; and new generations of computer buses and computer networking systems dramatically increase their data throughput.

Nonetheless, there is one area in the computer communications system that remains unchanged - the interface to the telephone network, the most dispersed and widely used form of worldwide communications. Surprisingly, basic telephone service has not changed in the last 100 years, and still has the same analog interface designed for voice rather than data transmission. That limitation was overcome in the early phases of the computer-communications evolution with the development of modems and fax devices with new modulation, compression, and error-correction techniques. With their implementation, data transmission rates over analog lines have increased from 300 to 1,200 to 2,400 to 9,600 to 14,400 to 28,800, 33,600 and finally to 56 Kb/s. The latter is close to the maximum physical throughput of analog lines. As a result, data speeds have reached their limits over existing analog lines. One way to overcome this limitation is to use services of a new type of network called Integrated Services Digital Network (ISDN).

ISDN was the first digital dial-up telecommunication service capable of carrying all types of traffic including voice, fax, high-speed data, video, and packet-switched data all through just one access line. This makes ISDN an effective solution for a wide variety of applications, producing significant cost savings. There are many benefits of ISDN services that fax systems and other applications can use. These include: more reliable connections, lower line noise and interference - essential for high-speed fax transmission, better call progress analysis, and more sophisticated error reporting mechanisms. Additionally, the ISDN benefits, such as streamlined fax routing, faster call setup, and doubled wiring cable utilization, make it unique for fax applications. This paper explores all the benefits of using ISDN, including the advantages it offers to computer-based fax.

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