We use our machine as a SIP gateway to bridge calls from a SIP Provider to a Call Center PBX (inbound and outbound).
We started out with a D410E (without the echo cancel module) and then purchased the EC100-128 separately to help deal with echo problems.
I followed the instructions at
The hardware echo canceller works great at first but after 15 to 20 minutes, many of our outbound calls start getting echo. These are calls going from our PBX to Asterisk to our SIP Provider. Inbound calls seem unaffected. In testing specific lines, I find that specific lines appear to still be getting echo cancellation on outbound but many are not. Restarting the Asterisk and Dahdi service will fix the problem but after another 15 to 20 minutes it starts happening again.
I've recompiled with the change you suggested. Not 100% sure what that does but /var/log/syslog does not show anything from wct4xxp when we begin to experience the echos. Specifically: "Yah,read (or write) can be slow" nor "Read (or Write) timed out!" are not popping up in the syslog file. Is there anything specific I should look for?
Correction and clarification on problem:
The echo is actually occurring just over 1 hour after restarting asterisk and dahdi services (not 15 - 20 minutes). And again, the echo is on an outbound call from PRI -> Asterisk -> SIP. The echo is heard by the person we are calling.
I have also heard of race condition causing hardware AEC to not function correctly in different versions (2.2 and up). Therefore, I have decided to take a different approach and use a software echo cancellation. You should pick the right software based on your echo tail (delay). In my case, echo tail was usually around 150ms so I have decided to use the PBXMate.