[asterisk-ss7] echo on a SS7/E1

Jean Cérien cerien.jean at gmail.com
Tue Mar 30 13:55:35 CDT 2010


I have the following setup:

Ast1.6.1.18+Chan-SS7  1.3 --> TE221 Board + VPMADT032 hw echo canceller  -->
E1 to Mobile MSC E/// AXE10

I assume the hardware module is detected as the following message appears:
wcte12xp: VPM present and operational (Firmware version 117)

Calls are initiated via a SIP Client with G729, codec available on the

On most of the calls, the quality is crystal clear - however, on some
specific numbers, there is a huge echo perceived on the SIP client.

This happens to some specific numbers, though 99%+ of the calls are ok - all
these numbers (with or without echo) are served by the same E1, so nothing
changes on my side. I am connected to a mobile GSM operator, when I call
this number from one of their cellphones, there is no echo...

Any suggestions as what to check ?

Many thanks,

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