Integrated Services Digital Network

July 1996


Integrated Services Digital Network

A New Standard Resolves Incompatibility Problems Among ISDN Devices

After years of wrangling, long-distance carriers, regional Bell operating companies and phone equipment vendors finally have agreed on standards for implementing Integrated Services Digital Network (ISDN). The telecommunications technology remained proprietary for two decades before enough support could be garnered for the Multilink Point-to-Point Protocol. The new standard has resolved incompatibility problems among various ISDN devices.

ISDN works on the same type of copper twisted-pair wiring currently used for conventional phone networks. The difference is that it provides a single universal interface to multiple network services. That interface enables the technology to carry voice, data and video transmissions simultaneously over the same telephone line-meaning users can talk on the phone, participate in a videoconference, modem a computer file and send a fax at the same time on the same line.

By sharing a common digital pipe, PC users can share screens while talking. Calls coming in over ISDN lines can automatically trigger database searches that will produce each caller's name, address, phone number and any other important information on file.

ISDN transmission speeds make it ideal for networks with intermittent, high-volume transactions. An ISDN line can move 64,000 bits of information per second, as opposed to the fastest modem moving 28,800 bits per second. The technology has been particularly popular among telecommuters, who use it as a dial-up service to connect to remote offices. It also is being used to connect small office networks to enterprise networks.

The federal government is one of the largest users of ISDN in the world. Agencies use the technology for everything from Internet access and bulletin-board services to videoconferencing.

Long-distance ISDN service is provided by AT&T on the FTS 2000 contract. Local service in the Washington, D.C., area is available from Bell Atlantic on the General Services Administration's Washington Interagency Telecommunications System and the Defense Department's Telecommunications Modernization Project.

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