Integrated Services Digital Network (ISDN)

Integrated Services Digital Network (ISDN) is a worldwide telecom standard that uses digital transmission and switching technology for voice and data communications. It allows large data to transmittals and provides the framework for interactive video services.

Modems connected to the public telephone network provide a relatively inexpensive way to obtain low-speed data services. The modems are inexpensive, the local telephone rates are very reasonable (if not flat fee) and service providers are abundant. Most corporations either have in-house dedicated Remote Access solutions or rely on an out-sourced plan for their employees from one of many service providers.

ISDN was intended to replace the existing public telecom network around the world - but it never lived up to its expectations. The firt generation (narrowband) ISDN was based on the use of a 64 Kbps channel as the basic mechanism for switching with a circuit-switching orientation. Second generation (broadband) ISDN supports very high data transfer rates and is based on the packet-switching concept. ISDN supports voice, data, digital data exchanges, and video. Most ISDN applications use one B channel with 64 kbps transfer capability for data transfers, faxes or video. A 16 or 64 kbps D channel also exists and can be used for signalling, teletex, videotex, etc. while the higher speed versions of ISDN also have an H channel that can support rates from 384 to 1920 kbps.

Unlike cable modems and DSL, ISDN can be installed further away from the central office. But the service usually costs a lot more and an ISDN router/modem is usually more expensive than regular or cable/dsl modems. Most ISDN service plans are NOT flat rate like other DSL and cable. There is a usage charge with ISDN, possible long distance charges and access costs with an Internet Service Provider. ISDN today is limited for certain applications (usually backing up dedicated lines) but for telecommuters it should be a last ditch option.

In most cases, DSL and cable are recommended over ISDN for regular Internet and Telecommuting applications.