Installation & Maintenance Manual 6. Cabling the Mediant 1000B PSTN Gateway
Version 6.8 47 Microsoft Lync Server
6.5.2 Connecting the PSTN Fallback for E1/T1 Trunks
The device supports a PSTN Fallback feature, whereby upon a power outage or IP
connectivity problem (e.g., no ping), IP calls are re-routed to the PSTN. This guarantees
call continuity.
PSTN Fallback is supported if the device houses one or two E1/T1 ("TRUNKS") modules,
where each module provides two or four spans. In the event of a PSTN fallback, the
module's metallic relay switch automatically connects trunk Port 1 (I) to Port 2 (II), and / or
trunk Port 3 (III) to Port 4 (IIII) of the same module. For example, if a PBX trunk is
connected to Port 1 and the PSTN network is connected to Port 2, when PSTN Fallback is
activated, calls from the PBX are routed directly to the PSTN through Port 2.
To connect the digital trunk interfaces for 1+1 PSTN Fallback:
1. Connect Trunk 1 to a PBX.
2. On the same TRUNKS module, connect Trunk 2 to the PSTN.
Figure 6-9: Cabling (Ports 1 and 2) PSTN Fallback
Notes:
• PSTN Fallback is supported only on the TRUNKS module.
• PSTN Fallback is supported only between ports on the same TRUNKS module.
• PSTN Fallback is supported only for ISDN 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.
• The scenarios (i.e., power outage and/or IP network loss) upon which PSTN Fallback
is triggered is configured by the TrunkLifeLineType parameter. For more information,
see the User's Manual.
• This PSTN Fallback feature has no relation to the PSTN Fallback Software Upgrade
Key.
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