AT&T MERLIN LEGEND Release 4.0 Feature Reference page 413

Feature Reference
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 channel ).
OUTGOING
LINE IS
SELECTABLE
BY USER
Figure 34. PRI Lines and B Channel Groups
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
Line 801
Line 802
Line 803
Line 804
PRI
Line 849
PRI
Line 850
B-CHANNEL
PRI
Line 851
GROUP
PRI
Line 852
Primary Rate Interface (PRI) and T1
Trunks:
Loop-Start
Ground-Start
Tie
DID
PRI
B-channels
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