[Asterisk-Users] Weird Echo Problem

[Martin Roy]

Ok I know I'm not the only one having echo problem with asterisk but the 
weird thing is that when I receive a call from a PSTN line on my TDM04B 
card I don't have any echo problem at the beginning of the call then 
after a few minutes I start having echo on my side only (the person 
calling from a regular phone doesn't have any echo), then it stop and 
come back all the way until the call is finish. It does the same thing 
on outgoing calls from my Cisco 7960 phone to the PSTN line. I have no 
problem when it's an internal call from one 7960 to another one. I tried 
a lot of different config in zapata.conf and the one that seems to work 
the best for now is this one :

context=incoming
signalling=fxs_ks
echotraining=800
echocancel=yes
echocancelwhenbridged=yes
rxgain=0
txgain=0
immediate=no
busydetect=no
callprogress-no
musiconhold=default
usecallerid=yes
callerid=asreceived
group=1
channel => 1-8

Any suggestion why it start doing echo after 5 minutes or so?

Thanks

Martin