Lucent Technologies MERLIN LEGEND Release 6.1 Feature Reference page 544

MERLIN LEGEND Communications System Release 6.1
Feature Reference 555-661-110
Features
Primary Rate Interface (PRI) and T1
Calling Party Number (CPN)
If you subscribe to the AT&T INFO2 ANI service or another PRI caller
identification network service (Release 4.2 and later), an incoming call on an
ISDN line includes accompanying information about the party placing the call.
This can be either a station (extension) identification number that is defined by the
internal dial plan of the system where the call originated (
number information (
With this information, a call recipient may identify the caller before answering.
Lines/Trunks
In this section on PRI and T1, lines are the representations that appear on
extension telephones or that are put into pools. They represent the type of service
requested on a call. Trunks are the facilities that link switches. For all facilities
except DS1, lines have a one-to-one correspondence to trunks because there are
24 transmission channels for each DS1 connection. With PRI, lines are further
removed from trunks because the type of service is not linked to the B-channel
(trunk). The system has an intermediary called a B-channel group (BCG). Lines
are used to place and receive calls, and a BCG links B-channels to lines.
B-channel groups may be either a single B-channel or multiple B-channels
grouped together.
Figure 37 on page 497
function together. For outgoing calls, a user selects a PRI line that routes the call
to a B-channel group. The BCG selects an open B-channel and connects over the
PRI connection. For incoming calls, the network selects an open B-channel and
the BCG directs the call to the PRI line for which it has been intended: it matches
the Called Party Number with the line's programmed telephone number. In
addition, the Dial-Plan Routing feature may be used to further direct the call to a
specific extension (SA button) or calling group by matching some portion of the
Called Party Number against the system dial plan. Dial-plan routing is similar to
Direct Inward Dial.
Each DS1 module is given 24 lines, whether or not it is used for emulation of
lines/trunks or for PRI.
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
shows how lines, B-channels, and B-channel groups
), or both (
Issue 1
August 1998
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), billing
).
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