ISDN TechnologyOverview G

Overview

Integrated Services Digital Network (ISDN) is an internationally agreed-upon standard for end-to-end digital communications over the public switched network. ISDN includes specifications for signalling, long-distance transmission, bulk subscriber lines, and individual subscriber lines.

Two types of ISDN services are currently available:

Basic Rate Interface (BRI)

Primary Rate Interface (PRI)

Both BRI and PRI ISDN services have two types of digital channels: one ISDN D channel and multiple ISDN B channels.

The ISDN D channel is generally used to transmit signalling and control information such as call-in- progress, incoming-call, or call-accepted information. It transmits information at a rate of 16 Kbps on BRI and at 64 Kbps on PRI.

The ISDN B channels transfer data (voice, circuit- switched data, and packet-switched data) at a rate of 56 or 64 Kbps, depending on the local ISDN network.

5536 PRI RAS Communications Controller Users Guide

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