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MERLIN LEGEND Communications System Release 6.1
Network Reference
555-661-150
Issue 1
August 1998
Network Management
Page 5-22Tandem PRI Facilities
5
Tandem PRI Facilities 5
This topic presents considerations for managing tandem PRI facilities connected
to your local system in a private network.
If your system includes PSTN PRI facilities that route calls to non-local
extensions, you also need to consult the procedures in the “Dial Plan Routing”
topic of “PRI Facilities,”
System Programming
. You can, if necessary, delete all the
digits from PRI calls received on a system and substitute the non-local extension
number (calling group number, for example) required for routing across the private
network.
When you order facilities for PRI, you specify a T1 point-to-point circuit; the
service provider may supply amplification but not PRI service or switching.
Program the circuit for PRI, following the instructions in
System Programming
for
both DS1 and PRI. Tandem PRI trunks should be programmed for Extended
Superframe (ESF) format, which detects errors more reliably than other formats.
In addition, tandem PRI trunks should be programmed for bipolar 8 zero
substitution (B8ZS) line coding. If alternate mark inversion (AMI) line coding is
used, 64-kbps data calls (128 kbps for 2B data) are not supported. If D4 framing is
used maintenance is more difficult. The framing and line coding must be verified
with the service provider. However, 56-kbps data calls are supported (112 kbps for
2B data).
NOTE:
Verify that any Channel Service Unit (CSU) on the DS1 circuit between the
MERLIN LEGEND Communications System and the PSTN is programmed
for the same framing as the DS1 slot on the MERLIN LEGEND
Communications System.
You may place drop-and-insert equipment between systems connected by a PRI
tandem facility, allowing use of fewer than 23 B-channels. Some channels are
reserved in this way for non-MERLIN LEGEND communications, and the
remaining are dedicated to MERLIN LEGEND voice/data traffic. The equipment
must never drop Channel 24, the D-channel. All 24 channels still count toward the
system maximum of 80 lines. For channels not used by the MERLIN LEGEND
system, lines and B-channels must be removed from the B-channel group.
NOTE:
When connecting to a DEFINITY ECS or DEFINITY Prologix, the
DEFINITY must provision all 23 B-channels and allow MERLIN LEGEND to
take out of service any B-channels that were dropped, then DEFINITY can
unprovision those channels.