Lucent Technologies MERLIN LEGEND Release 6.1 System Manager's Manual page 94

MERLIN LEGEND Communications System Release 6.1
System Manager's Guide 555-661-118
3 System Components
Control Unit
Modules Supporting Lines/Trunks
Table 3–1
describes a few module features and modules that need additional explanation.
NOTE:
Modes of operation affect features and hardware. For example, Direct
Inward Dial (DID) is supported only in Hybrid/PBX mode, so if your system
uses a different mode of operation, you do not need a DID module. For
more information about modes, see Chapter 2, "About the System."
Power-Failure Transfer Telephones
When your system was planned, the Lucent Technologies representative(s) made
sure that you had a module to support one or more power-failure transfer (PFT)
telephones. These telephones, each of which is connected to a special line/trunk
jack, allow you to make and receive calls during a commercial power failure. They
do not affect the capacity of the modules.
100D Module
The 100D module has only one line/trunk (called a Digital Signal Level 1 or DS1
facility) but actually supports 23 or 24 "virtual" lines/trunks. These are called
channels or B-channels , depending upon the type of service you choose. As
described in Chapter 2, "About the System," you can program the DS1 facility to
provide either T1 or Primary Rate Interface (PRI) service on the 100D module.
NOTE:
The 100D module is not available in Behind Switch mode.
In addition, PRI and T1 support Group IV (G4) fax machines, as well as desktop
and group videoconferencing.
PRI and T1 differ in some important ways:
Primary Rate Interface (PRI). PRI supports Integrated Services Access,
also called Shared Access for Switched Services (SASS) and Call-by-Call
Service Selection . This feature, available from various telecommunications
companies, allows multiple PRI services to use the same facilities,
eliminating the need to have dedicated, separate incoming and outgoing
B-channel groups. It selects the optimal service for each outgoing call,
allowing more than one service over each B-channel, including digital data
communications at speeds up to 64 kilobits per second.
summarizes the modules that support lines/trunks. This section
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