Lucent Technologies MERLIN LEGEND Release 7.0 Feature Reference page 576

MERLIN LEGEND Communications System Release 7.0
Feature Reference 555-670-110
Features
Primary Rate Interface (PRI) and T1
PRI
PRI is a common configuration for a DS1 facility. A DS1 facility consists of
24 channels, sometimes referred to as DS0 channels, each with a capacity of
64 kbps. DS1 refers to the twenty-four 64-kbps channels, plus framing and
signaling bits, multiplexed together to form a 1.544-Mbps Digital Signal Level 1
signal. When used for PRI, a channel can be designated as either a B-channel
( bearer channel ) or a D-channel ( data or delta channel ).
A B-channel is used to carry user information, such as the voice or data content of
a call, between the system and the far-end switch. Each B-channel provides
access to one or more network services. Releases 1.0 and 1.1 support access to
only one network service for each B-channel. Release 2.0 and later supports call-
by-call service selection, which allows multiple network services over the same
B-channels. The D-channel conveys signaling required to set up, control, and
clear calls made over all of the B-channels.
The most common configuration of a DS1 facility for PRI consists of 23
B-channels and 1 D-channel, although other combinations are possible. Each PRI
must include a D-channel, but may include fewer than 23 B-channels. The
remaining channels cannot be used for any other purpose.
NOTE:
The MERLIN LEGEND Communications System does not support multiple
PRI facilities sharing one D-channel (as allowed with Non-Facility
Associated Signaling).
Up to three DS1 carrier facilities (maximum of two in one carrier), and therefore
three PRIs, can be connected to the system through separate 100D modules,
each of which occupies a slot in the system carrier. In terms of system capacity,
each DS1 channel counts as a line/trunk, so the maximum number of B-channels
supported by the system is 69. Signaling for 69 B-channels is provided over three
separate D-channels, using up 72 of the system's 80-line capacity.
Issue 1
April 1999
516