MERLIN LEGEND Communications System Release 6.1
Feature Reference
555-661-110
Issue 1
August 1998
Features
Page 531Primary Rate Interface (PRI) and T1
Tandem Switching
In Release 6.0 and later systems (Hybrid/PBX mode only), PRI and T1
(emulated tie voice or data tie) facilities can be private tandem trunks. To
provide the facility, customers order a point-to-point T1 circuit from a
service provider and use system programming to set it up for PRI or T1.
However, the provider only supplies amplification, not switching services.
When system programming of the DS1 switch type labels a PRI facility as
a tandem trunk, the system selects an unused B-channel group
(beginning with Group 80 and counting backward) and assigns all the
B-channels to it. This programming can be changed after the initial
assignment.
Drop-and-insert equipment can be placed between systems connected by
tandem PRI or T1 trunks to provide fractional service. All channels still
count toward the 80-line system maximum, and the PRI D-channel must
never be dropped.
PRI and T1 tandem trunks require the same initial DS1 programming
(clock synchronization, framing format, and so on) that other such
facilities do. However, for PRI facilities, routing, network service, and copy
telephone number settings are programmed automatically by the system
and cannot be changed unless the switch type is modified first.
When a call arrives on a dial-plan routed PRI facility and its digits match
an extension on the non-local dial plan, the call is routed to the
appropriate remote extension.
Transfer For trunk-to-trunk transfer with no extension number involved, the Calling
Party Number for the outbound call is the programmed base number.
Data calls cannot be transferred.
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