for whatever reason, we get a loud click about 1 second into every PSTN call. the click occurs on the receiving end of the channel (i.e. anyone who calls us or whom we call gets silence 1 second into the call, we get the loud click/squeal).
This started about 2 months ago, when we changed offices.
-We are running 1.4.1 of asterisk and zaptel.
-our phone service is through Nuvox
-We have two TDM400 modules with 6 PSTN lines (4 in one, 2 in the other).
-all phones are SIP phones (Linksys 941).
-I have run fxotune and all echo cancellation steps I could find. I’ve also verified signal levels on a 1004 loop line
-the problem occurs if I call directly into the attendent or directly into voicemail
-the problem does not occur if I connect an analog phone directly into the jack, only on the asterisk lines.
Any suggestions as to where to go from here to diagnose the problem would be greatly appreciated.