[Asterisk-Users] Chaining more than one zap echo canceller?

[Kris Boutilier]

 I have Asterisk connected to a channel bank via a t100p card. There
excessive sidetone generated on the analog side due to an impedance mismatch
- I am very close to my serving CO which brings the line down to about
150ohms and the channel bank is expecting 600ohms. However, the very loud
sidetone is being fairly effectively supressed by the zap echo canceller and
I have quite usable lines as a result.

 From time to time calls are placed to other PSTN numbers (even terminating
off of the same CO) that are introducing their own far end echo component on
the line and it isn't being supressed at all - thus my outbound callers
begin to hear their own voice and get very frustrated. I have to assume the
second reflection couldn't be supressed by design - the zap echo can has
already locked on to the sidetone echo after all.

 So, I have a fix for the sidetone/impedance problem (PRI on order) however
is it possible to insert another can into the system somehow? For example,
if I were to run TDMoE to a second box and access to the t100p/channel bank
through there?

Any suggestions welcome (apart from curing the sidetone)  :-)

Kris Boutilier
Information Systems Coordinator
Sunshine Coast Regional District