Asterisk not routing voice when call is connected


I am a new user to the Asterisk system and we have been suffering some problems with out system. Here is the detials of what our system is

Asterisk V 1.2
Digium TE410P with jumpers set to E1
2.6.5 Kernel
Snom 320 and 190 hand sets

The problems we have been having is that when someone calls in and Asterisk routes that call to the users hand set it does not seem to route any of the voice down. All we hear is a voice echo of our own voices, when checking the logs Asterisk thinks everything is fine. This does not happen all the time, it is an intermittent problem. We have tried a
number of things to get to the bottom of this but we have hit the wall and are at a real loss to understand why it is only happen some times.

Has anyone suffered this type of problem and if so what is the solution.


It looks like it is a hardware problem with our ISDN router we have, so it is possible that it has nothing at all to do with Asterisk.

I will keep you informed to the outcome