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MERLIN LEGEND Communications System Release 6.1
Network Reference
555-661-150
Issue 1
August 1998
Introduction
Page 1-6Tandem Trunking and Tandem Switching
1
Tandem Trunking and Tandem Switching1
The term
tandem switching
describes the process of routing an incoming call over
an outgoing tandem trunk or PSTN facility. If the outgoing trunk is a tandem trunk,
it connects to another system in a private network. When the call terminates at an
extension on a non-local system, it is an
intersystem call
. Release 6.0 provides
enhanced underlying capabilities to satisfy recommended levels of voice and data
quality over tandem trunks in a private network.
A tandem-switched call does not necessarily terminate at another system that is
directly connected to your own. It may travel over the private network to yet
another networked system. Furthermore, a non-local system may direct the call to
a PSTN facility and then to someone located outside the private network.
For example, from a system in Minneapolis, a long-distance call to an outside
party in Boston can be routed over private tandem trunks to another system in
Chicago and then to a system in Boston, resulting in a local call. This routing
requires that the private network sites be connected using either a
delay-start
tie
line (analog or T1-emulated) or a digital T1 circuit that has been programmed for
PRI.
Figure 1–1
shows one way that systems can be connected in a private network.
NOTE:
All of the figures in this chapter use the following conventions:
■ A solid line represents a tandem trunk that connects one system in a
private network to another system in a private network.
■ A dashed line represents a facility that carries a call to the PSTN.
■ A square labeled ML indicates a MERLIN LEGEND
Communications System.
■ A rounded rectangle labeled DEF indicates a DEFINITY ECS or
DEFINITY ProLogix Solutions system.