Hardware Installation Manual
26
Document #: LTRT-85609
Mediant 600
5.7
Connecting BRI Interfaces for PSTN Fallback
The PSTN Fallback feature provides a BRI interface connection to the PSTN upon a power
outage (i.e., Ethernet link failure). This allows a telephone or PBX connected to a BRI port
to continue making calls through the PSTN network (instead of through the IP network).
The PSTN Fallback is provided by connecting adjacent BRI ports, where one port is
connected to, for example, a PBX and its adjacent port is connected to an active PSTN line
(i.e., normal operation, not only dedicated to Fallback). In the event of a power failure, a
relay connects the adjacent BRI ports (i.e., ports
I
to
II
, and ports
III
to
IIII
) by the closing of
a metallic switch inside the module.
Figure
5-7: PSTN Fallback for BRI Ports
Notes:
•
Damage can be caused to external equipment if PSTN Fallback is
activated on two ports that are configured as user side.
•
Ensure that paired BRI ports (i.e., ports
I
and
II
, and ports
III
and
IIII
) are
not identically configured (i.e., one must be user the other net side);
otherwise, PSTN Fallback does not function.
