[asterisk-users] Echo problem

[Jason Bachman]

As I understand it, the echo cancelers in Asterisk only work with the 
Analog cards (FXS/FXO).  If you are getting echo on a digital line, 
there is a problem with either a DAC, the T1 clocking, or you are 
getting bit errors.  You have a Switch in the middle - perhaps the 
switch is doing doing digital-analog conversions instead of sending the 
digital data straight through. The cause of the echo could very well be 
there, and the echo cancelers (even if they worked on a digital line) 
would not help because the cause of the echo is somewhere else, not at 
the Digium card.  Check your Tadiran switch for any echo cancel 
options.  I'm not familiar with that switch so I am no help to you on 
that, but I am pretty sure that its not the Digium card or Asterisk.

Regards,
--Jason Bachman

Scott Gifford wrote:
> Hello,
>
> We're in the process of setting up an Asterisk server, and are having
> echo problems.  We have a Digium TE110P, and have tried the MG and
> MARK2 AGGRESSIVE echo cancellers, with a variety of gain levels and
> training times, and with both trunk and 1.2 branch versions of
> Zaptel, Libpre, and Asterisk.  In all cases, callers from the PSTN
> hear their own voice echoed back after 1.5-2 seconds; none of these
> adjustments made a difference, except adjusting gain made the echo
> quieter.
>
> We followed these instructions in trying to eliminate echo:
>
>     http://www.asteriskdocs.org/modules/tinycontent/content/docbook/current/docs-html/x1695.html
>
> Our lines come in from the telco in a PRI, then connect to a Tadiran
> switch which hands the lines off to Asterisk over a T1 card.
>
> We have done loopback tests with the Digium card with a loop plug in
> it.
>
> We're a bit stumped as to what to try next.  Any suggestions or
> advice?
>
> Thanks
>
> ---Scott.
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