Instruction manual

Features
Up to three T1 carrier trunks, 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 T1 channel counts as a trunk
endpoint, so the maximum number of B-channels supported by the system is
69. Their signaling is provided over three separate D-channels, using up 72 of
the system’s line capacity.
Called Party Number (CdPN)
In general, the term Called Party Number (CdPN) is a telephone number that
was dialed to reach a destination. However, while routing the call, the network
can change the CdPN to make routing easier. In either case, the network sends
the CdPN to the system when a call arrives at the system.
Lines/Trunks
In this section on PRI, there is a distinction between lines and trunks. Lines are
the representations that appear on station sets or are put into pools. They
represent the type of service requested on a call. Trunks are the facilities that
link switches. For all except DS1, lines have a one-to-one correspondence to
trunks, since 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.
Each line has a separate dial plan number, and each DS1 module is given 24
lines, regardless of whether or not it is used for emulation of trunks or for PRI.
DS1 Facilities
A digital signal 1 (DS1) facility is a transmission system that transports digital
signals in the DS1 format. The interface that allows the connection of DS1
facilities to the system is the 100D module. Through this module, voice and
data calls can be made or received using a DS1 facility.
Twenty-four digital signal 0 (DS0) channels, each operating at 64 kbps, plus
framing bits, are multiplexed, forming a DS1 signal of 1.544 Mbps. Each DS0
channel within the DS1 signal corresponds to a logical endpoint. Even though
there is only one physical jack, the 100D module supports up to 24 logical
endpoints or ports (one for each channel).
In DS1 format, calls to other digital PBXs or telephone company foreign
exchanges (FXs) remain digital, and signals do not need to be converted to
analog for acceptance by the connecting trunk. In addition, the 100D module
can be configured to work with T1 or PRI service.
To connect the 100D module to an outside DS1 facility, a Channel Service Unit
(CSU) is used. The CSU regulates the transmission into and out of the 100D
module so that the module matches the transmission of the outside facility.
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Primary Rate Interface (PRI)