[Asterisk-Users] Echo Problem

[Rich Adamson]

> > I've got mostly Cisco 7960s and a few Analog phones on TDM Ports.  On 
> > the 7960s, the echo is quite bad. On the TDM ports, it is there, but not 
> > as bad.  I have tried setting echo cancellation to various numbers, but 
> > have had no luck.
> > 
> > This began after a HEAD version of * was installed. Since then, I 
> > installed what I think is the latest stable version (Asterisk 
> > CVS-v1-0-12/14/04-16:49:32) and the echo is still there.
> > 
> > A support guy at Digium said it was a SIP problem.
> 
> Just wanted to second this.  I have about 20 7940's, 2 7960, and a 4 
> port FXS for fax machines going into a Bellsouth T1 (pri) and we get 
> echo on some calls.  I turned on echotraining (not for the faxes of 
> course -- echocancelwhenbridged=no) and it will train out, but I thought 
> that voip -> pri could not have echo problems.
> 
> Anyway, please keep me updated if you figure out a (real) solution to this.

echotraining=800 did fix the OP's problem.

But, there can still be far-end echo even with PRI's. Those cases
involve hybrid issues at some distant end that are difficult at best
to address at your end.

As has been stated many times before, the echo canceller within * is
not as good/reliable as commercial can's and won't handle some of
the far-end echo problems.