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iSPAN PRI PCI ISDN Users Guide 125
HISDN Technology
Overview
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 service 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.
• 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.
Basic Rate Interface
The ISDN Basic Rate Interface consists of three digital
channels: one D channel and two B channels. These channels
can be used simultaneously, and are often referred to as 2B+D.