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MERLIN LEGEND Communications System Release 6.1
Network Reference
555-661-150
Issue 1
August 1998
Introduction
Page 1-11Tandem Trunking and Tandem Switching
1
Table 1–1. Tandem PRI Trunks versus Tandem Tie Trunks
Feature PRI Tie Differences
Intersystem calling
✔✔
PRI provides faster call setup.
For intersystem calls, the caller’s
extension label and extension number
can be displayed at recipient’s MLX (and
some DEFINITY) display telephones
across the network.
✔
Calls that cross tandem tie trunks are
displayed as outside calls.
Manual intersystem transfers across the
private network return to the originator
when the intended destination is busy or
has Do Not Disturb on and no call
coverage path available.
✔
When a call is transferred manually
across the network on tandem tie
facilities, the call does not return in the
event that the intended destination is
busy. The original caller must call back in
order to speak with someone.
Dial-plan routing of calls on incoming
PSTN PRI trunks across the private
network.
✔✔
PRI provides faster call setup.
Automatic Number Identification (ANI)
and Incoming Caller ID (ICLID)
✔
Information is conveyed across the
network on tandem PRI trunks, not on tie
trunks.
Routing of PSTN DID calls across the
network.
✔✔
128-kbps 2B data video and data
exchange across the network.
✔
Tie trunks support only 14.4 kbps. T1-
emulated tie trunks programmed for data
can only support up to 112 kbps.
Optimal transmission quality for calls
routed across two or more systems in a
private network.
✔✔
To ensure adequate transmission quality,
no more than two spans of analog
tandem tie trunks can be provided
between switches in a series
configuration (or 3 including transfers
and coverage). Also, for long loops of
analog tandem tie trunks between
switches, you may need to contact the
PSTN service provider to adjust the
amplification.
Transmission quality on PRI and T1
tandem trunks are the same. Up to eight
tandem PRI and/or T1 trunks can be
used in a series configuration providing
optimal transmission quality. However,
T1 tandem trunks may cause call setup
delays.