[Asterisk-Users] Fun with Echo -- Follow up

[Brian Swan]

I figured I'd answer my own thread and document what it took to get  
rid of the echo at my location.  For those of you trying to get rid  
of echo, let me tell you, "what worked for that guy, probably won't  
work for you".  I think we've all heard that before, and it's true.   
Let me assure you that echo can be removed from your phone lines.  At  
20 hours into my 40 hours spent purging echo from my system, I didn't  
believe that, but its true.  So, here's what it took to get it out of  
my system:

1. Download zaptel-trunk from SVN:  As of this writing (6/20/06)  
using the "trunk" code instead of the 1.2.6 code was a major  
contributor in getting my echo to go away.

2. Use fxotune in zaptel-trunk:  Find a silent-termination test  
number from the phone company and use FXOTune.  I couldn't get it to  
dial right in order to get silence on the line.  You can verify if  
it's working correctly by running it with an analog handset connected  
to your phone line.  Pickup the handset and then run the command.  In  
my case, fxotune would never clear the line, or dial the silent  
termination number I was giving it, not sure if this is a bug or  
not.  What I eventually had to do was pick up the phone, dial the  
silent-termination number manually, run "./fxotune -i -b 4 -e 4", and  
quickly hangup the phone.  This was the only way I got good results  
from the program.

3. Patience and lots of "vi zconfig.h": Try each echo canceler, with  
and without the "Aggressive" option.  What eventually worked for me  
was the MG2 with Aggressive cancelation.

4. Along with above, you need to also try each and every combination  
of echocancel=xx and echotraining=xx.  These setting do make a  
difference.  I went through every possible value of each setting with  
each echo canceler, and kept notes along the way.

5. TIME: As I said above, I probably have 40 hours into eliminating  
the echo, but it is genuinely gone.  Your echo problem can be solved,  
it will just take some time.

Hope this helps someone!

Thanks,
Brian