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Glossary and Abbreviations
Issue 5 January 1998 GL-27555-230-024
Integrated Services Digital Network (ISDN)
A public or private network that provides end-to-end digital communications for all services to
which users have access by a limited set of standard multipurpose user-network interfaces
defined by the CCITT. Through internationally accepted standard interfaces, ISDN provides
digital circuit-switched or packet-switched communications within the network and links to other
ISDNs to provide national and international digital communications. See also Integrated Services
Digital Network Basic Rate Interface (ISDN-BRI) and Integrated Services Digital Network Primary
Rate Interface (ISDN-PRI).
Integrated Services Digital Network Basic Rate Interface (ISDN-BRI)
The interface between a communications system and terminal that includes two 64-kbps
B-channels for transmitting voice or data and one 16-kbps D-channel for transmitting associated
B-channel call control and out-of-band signaling information. ISDN-BRI also includes 48 kbps for
transmitting framing and D-channel contention information, for a total interface speed of 192
kbps. ISDN-BRI serves ISDN terminals and digital terminals fitted with ISDN terminal adapters.
See also Integrated Services Digital Network (ISDN) andIntegrated Services Digital Network
Primary Rate Interface (ISDN-PRI).
Integrated Services Digital Network Primary Rate Interface (ISDN-PRI)
The interface between multiple communications systems that in North America includes 24
64-kbps channels, corresponding to the North American digital signal level-1 (DS1) standard rate
of 1.544 Mbps. The most common arrangement of channels in ISDN-PRI is 23 64-kbps
B-channels for transmitting voice and data and 1 64-kbps D-channel for transmitting associated
B-channel call control and out-of-band signaling information. With nonfacility-associated signaling
(NFAS), ISDN-PRI can include 24 B-channels and no D-channel. See alsoIntegrated Services
Digital Network (ISDN) andIntegrated Services Digital Network Basic Rate Interface (ISDN-BRI).
intercept tone
A tone that indicates a dialing error or denial of the service requested.
interface
A common boundary between two systems or pieces of equipment.
internal call
A connection between two users within a system.
International Telecommunications Union (ITU)
Formerly known as International Telegraph and Telephone Consultative Committee (CCITT), ITU is
an international organization that sets universal standards for data communications, including
ISDN. ITU members are from telecommunications companies and organizations around the
world. See alsoBX.25.
International Telegraph and Telephone Consultative Committee
See International Telecommunications Union (ITU).
interflow
The ability for calls to forward to other splits on the same PBX or a different PBX using the Call
Forward All Calls feature.
intraflow
The ability for calls to redirect to other splits on the same PBX on a conditional or unconditional
basis using call coverage busy, don’t answer, or all criteria.
internal measurements
BCMS measurements that are made by the system. ACD measurements that are made external to
the system (via External CMS) are referred to as external measurements.