[Asterisk-Users] Echo on my TDM fxo

[Neil and Fiona]

> 
> First, ensure the TDM card has been defined to match the telephony
> standards for each country where the card is installed.

Bad echo on these outside North America is likely to be because of
impedance mismatch. Echo cancel isn't likely to properly fix it.

I was surprised at the lack of info about setting up the TDM cards for
various countries. I eventually worked it out from a couple of clues
online and looking at parameters that could be passed to the wtcdm
module along with the wctdm.c source file.

Open the wctdm.c source file to see a list of countries and regions
supported.

When you load the driver modules 

1. load zaptel with modprobe zaptel
2. load wctdm with modprobe wctdm opermode=COUNTRYNAME (where
COUNTRYNAME is exactly as you found it in the list of countries in the
wtcdm.c source file)

Next type in tail /var/log/messages

If it didn't work you will see that the FXO ports are still in FCC mode

Mar 23 17:23:51 Asterisk kernel: Module 0: Installed -- AUTO FXO (FCC
mode)

In my case I got
Mar 23 17:23:51 Asterisk kernel: Module 0: Installed -- AUTO FXO
(AUSTRALIA mode)
Mar 23 17:23:51 Asterisk kernel: Module 1: Installed -- AUTO FXO
(AUSTRALIA mode)
Mar 23 17:23:51 Asterisk kernel: Module 2: Installed -- AUTO FXO
(AUSTRALIA mode)
Mar 23 17:23:51 Asterisk kernel: Module 3: Installed -- AUTO FXO
(AUSTRALIA mode)

If it didn't work check that the modules weren't already loaded by any
of your startup scripts.

Before I did this I had massive echo. It was almost solved by editing
the zaptel makefile to enable aggressive echo cancel. Problem was that
the echo crept back in and the call quality went screwy. 

It's now perfect.