Hardware Installation Manual
28
Document #: LTRT-85609
Mediant 600
5.9
Connecting E1/T1 Trunks for PSTN Fallback
The device supports PSTN Fallback feature when provided with two E1/T1 PRI spans. The
digital module's Port
II
serves as a dedicated Fallback port connected to the PSTN. In the
event of a power failure (i.e., no Ethernet link), a relay connects ports
I
and
II
by the closing
of a metallic switch inside the module, re-routing trunk traffic from the PBX to the PSTN
(instead of from the PBX to the IP network).
To connect the digital trunk interfaces for PSTN Fallback:
Connect Port
I
to the PBX, and Port
II
to the PSTN.
Figure
5-9: PSTN Fallback for PRI E1/T1
Notes:
•
Only ISDN supports the PSTN Fallback feature when the number of
supported channels (e.g., 30) is less than the maximum number of
possible channels provided by the physical ports (e.g., two E1 trunks).
When the number of supported channels (e.g., 60) equals the maximum
number of channels provided by the physical ports (e.g., two E1 trunks),
then other protocols such as CAS are also supported.
•
This PSTN Fallback feature has no relation to the PSTN Fallback
Software Upgrade Key.
