ISDN

ISDN (Integrated Services Digital Network) enables the integration of analog or voice data with digital data over a single network. ISDN requires connection at both ends of the transmission process, meaning that the end user and provider must have the required adapters. It is generally available from phone companies in many areas of the U.S. and Europe. ISDN has become rarely used in locations that offer service through high-speed and DSL modems. ISDN consists of two service levels: the PRI (Primary Rate Interface) and the BRI (Basic Rate Interface). PRI is intended for large corporations while BRI is more suitable for home users and small businesses. Both of these rates contain several B-channels and D-channels. The B-channels mainly transmit voice and data - the D-channels transmit signaling information and control. BISDN (Broadband Integrated Services Digital Network) extends the integration of the basic services by using fiber optic media. BISDN also encompasses frame relay service for robust high-speed data.