Loud click 1 second into all PSTN calls

Asterisk Asterisk Support
1

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.

2

You can hear a click when echotraining is enabled but it shouldn’t be a sqeal.

3

perhaps the gain is too high on the channel ? although wouldn’t it have to be really high to turn a tap into a squeal ?

4

The sound is best described probably best described as somewhere in between (a “squeak” perhaps). it is loud enough that you have to take the phone away from your ear.

–[zaptel.conf (entire file)]–
fsks=1-6
loadzone=us
defaultzone=us

–[zapata.conf]–
[channels]
usecallerid=yes
hidecallerid=no
callwaiting=no
threewaycalling=no
transfer=yes
echocancel=yes
echotraining=800
echocancelwhenbridged=yes
rxgain=10.8
txgain=3.0

;define channels
context=incoming
signalling=fxs_ks
loadzone=us
defaultzone=us
channel => 1
channel => 2
channel => 3
channel => 4
channel => 5
channel => 6
[end excerpt]

-in case you’re wondering, I set each channel separately to diagnose the problem and make sure it wasn’t any single module/line.
-If the echotraining is set lower, we get a lot of echo AND the squeak.
-I’ve turned echocancelling off and we still get the squeak.
-the hardware is unchanged from before the problem and I’ve tried pulling each card to see if it was a card issue.

the following might be helpful:
-our service (Nuvox) comes in on a T-1 that is split at a Cisco 2431 router into 8 analog voice channels and the remainder to data
-the voice channels are terminated to a punchdown block.
-6 of those channels go to the asterisk box
-the other two go to fax machines
-the fax machines don’t get the squeak.
-If I plug an analog phone into any of the ports, no squeak, either.

5

i was having a similar problem with my aastra phones. the only thing that i found to get rid of it was changing the codecs used.

6

I really don’t think it is our phones. When I plug an analog phone into any of the lines, the problem doesn’t exist. I’m assuming it is something from the digium cards forward.

I’m willing to give it a shot, though. What codec are you using? we are set for G711u.