Overview

ISDN is a digital voice and/or data service that (generally) works over existing copper local loops.

ISDN transmits data digitally and, as a result, is less susceptible to static and noise than analog transmissions, although it is very sensitive to outside interference. To avoid interference you have to be within a given distance of the CO (Central Office) equipment that serves you (typically 18,000 feet), and there can t be any other anomalies near the wiring that might interfere with the transmission.

Some applications that ISDN makes possible are telecommuting (remote image sharing and retrieval, inexpensive teleconferencing, combined voice and image collaborations, fast access to remote files or databases), high-speed Internet access, network backup, and LAN-to-LAN or PBX-to-PBX links.

ISDN supports PBX networking to remote workers, plus data networking. You can use ISDN routers to send PBX signaling and functions to remote (telecommuting) employees. If you use web-based resources you can allocate one channel for web data and the other for the PBX functions.

Using an ISDN network bridge or router, It is possible to connect an ISDN line to a LAN so all the PCs on the LAN can share the same ISDN line.

ISDN can substitute for analog leased lines between PBXs or LANs. A break-even between ISDN and leased lines is achieved at about two to three hours per day of usage.

Specialized hardware has evolved to fill each ISDN application niche. These are targeted products, with features well-suited to their designed uses. The ISDN vendors pretty...