[asterisk-users] Annoying echo echo problem problem ...

[Gordon Henderson]

I've installed several small asterisk systems now, all mostly the same, a 
few POTS lines on the outside and a separate analogue phone on the inside 
(usually a DECT phone of some sorts) and IP phones on the inside, all 
ticking along quite nicely.

However I've hit an issue with the latest one regarding echo )-:

Hardware is a TDM400P card. Phone lines are BT, but the telco is Telstra. 
(there are 2 lines) Asterisk is 1.2.13, Zaptel is 1.2.11. (Kernel 2.6.18 
and it's Debian stable, but I doubt that's an issue here)

The TDM has all the right UK drivers loaded. Zap/4 and Zap/3 go to the 
wall sockets, Zap/2 goes to a local analog <-> GSM gateway box.

Zap/2 works perfectly.
Zap/3 works perfectly.
Zap/4 gives me about half a seconds worth of full-volume echo.
Zap/4 gives me about half a seconds worth of full-volume echo.

I can say "Hello there" into a quiet line and hear it echoed back to me in 
full.

I've read and read and re-read just about everything there is to echo and 
tuning it. Re-compiled the zaptel drivers with the MG2 canceller.

I've tried the latest fxotune - which has given me an /etc/fxotune.conf 
of:

   2=5,0,0,0,0,0,0,0,0
   3=5,255,252,0,2,254,0,255,255
   4=9,255,1,4,0,0,1,255,0

(incidentally, I've never used fxotune on any other installation in the 
past, they've all "just worked")

and tried fiddling with the gains (I don't know of a UK based 1Khz 0dB 
source, but generated my own from another * server using miliwat - how 
this gets mutated over the wires I don't know, but it seems to work OK to 
me. Setting Tx gain down to -3 stops dialling working and people I call 
can't hear much until it's up to at least 3.

I can't understand how one line is OK and the other isn't, however when I 
listen to the line, there is a small amount of noise and a regular 
low-volume tick tick tick sort of sound. The other line is very quiet. (as 
it should be) I've had the line re-wired back to the master socket in the 
building too, so there shouldn't be any issues with internal wiring at 
all.

I've swapped lines into the TDM card and the echo moves with the line 
which should hopefully eliminate any card problems (unless I have 2 faulty 
modules?)

This one's got me stumped!
This one's got me stumped!

And of-course, the line is OK when you plug an ordinary analogue phone 
into it...

Any clues, hints, etc. would be most welcome!

Thanks,

Gordon

Output after loading modules, ztcfg and fxotune -s:

   Freshmaker version: 73
   Freshmaker passed register test
   Module 0: Installed -- AUTO FXS/DPO
   Module 1: Installed -- AUTO FXO (UK mode)
   Module 2: Installed -- AUTO FXO (UK mode)
   Module 3: Installed -- AUTO FXO (UK mode)
   Found a Wildcard TDM: Wildcard TDM400P REV I (4 modules)
   Registered tone zone 4 (United Kingdom)
   Registered tone zone 4 (United Kingdom)
   -- Setting echo registers:
   -- Set echo registers successfully
   -- Setting echo registers:
   -- Set echo registers successfully
   -- Setting echo registers:
   -- Set echo registers successfully

/etc/zaptel.conf:

   fxoks=1
   fxsks=2
   fxsks=3
   fxsks=4
   loadzone=uk
   defaultzone=uk

/etc/asterisk/zapata.conf:

   [trunkgroups]

   [channels]
   usecallerid=yes
   cidsignalling=v23
   cidstart=polarity
   hidecallerid=no
   callwaiting=no
   threewaycalling=yes
   transfer=yes
   echocancel=yes
   echotraining=yes
   echocancelwhenbridged=yes
   immediate=no
   faxdetect=no

   context=internal
   signalling=fxo_ks
   sendcalleridafter=2
   rxgain=0
   txgain=0
   mailbox=100
   callerid=100
   channel => 1

   context=incoming
   signalling=fxs_ks
   rxgain=0
   txgain=0
   group=1
   callerid=asreceived
   usecallerid=no
   channel => 2

   context=incoming
   signalling=fxs_ks
   rxgain=0
   txgain=0
   group=1
   callerid=asreceived
   channel => 3

   context=incoming
   signalling=fxs_ks
   rxgain=8
   txgain=4
   group=1
   callerid=asreceived
   channel => 4