[Asterisk-Users] Echo cancellation

[Steve Totaro]

> I am having problems with echo, first let me
> explain my setup:
> 
> I have a Gateway box, which basically is an
> Asterisk with a PRI card. It's only job is to
> interface with 2 incoming ISDN PRI connections.
> Then there are two other asterisk boxes to which
> my users are registered.
> Dialing from a phone it hits the first asterisk
> which forwards it to the gateway box and then on
> to the PSTN.
> 
> What are the general causes of echo?
> When calling from my SIP phone I hear no echo but
> the other end, the PSTN end, hears a lot of echo.
> What could cause this?
> 
>   Kristian.


You need to google echo on the wiki.  There are so many causes for echo
and possible fixes that work on some installations but not others.  Some
keywords to search for are "echo pri" and "echo avoidance"

>From reading the list, there is no echo introduced by a PRI and the echo
is created by the far side.  Nonetheless, it is still your problem.  

I would first try have a phone register directly to the box with the PRI
card and see if there is any difference.  

I would then check your Zapata.conf settings and adjust gains and also
try different echo can settings.  Make sure to change one thing at a
time and restart asterisk and test.  Write down your results so you can
get an idea for what is working.  Finally, if that is still not helping,
you can change the echo can method.  Trial and error.

Digium sells a hardware echo can upgrade for their cards as well but I
think it may only be an option for the quad port cards.

Finally, if that still is not working, then you may want to see what 3rd
party devices others have used.  I have seen success stories posted but
am not sure what was used.  I think the reason for the 3rd party devices
working when * software echo can cannot is the size of the tail.

Thanks,
Steve