[asterisk-users] AVM Fritz BRI cards and echo cancellation

[Andrea Spadaccini]

Ciao Simon,

> We are using 2 x AVM Fritz BRI cards with mISDN. The phones are
> Linksystem SPA922's and we are getting a little echo on the lines..
> from what i unserstand, these are passive cards and do not have any
> onboard echo cancellation, but im wondering if there is anything that
> can be done software/config wise to help with this?
> 
> I did find this (http://www.misdn.org/index.php/FAQ):
> 
> 4) You set another value for tx-gain, "-1" for example to prevent
> echoes. Please set the tx-gain back to "0" for those calls as in 3)
> ("vt0").

The point 4 you refer to is related to erroneous fax reception, I don't think
it's relevant for you.

Tx and Rx gains, though, are important because playing with them you can get
around simple echo problems. Those settings are in misdn.conf, and are named
txgain and rxgain.

If you don't resolve your problem, I recommend installing Octasic SoftEcho for
Asteris. I'm not affiliated with them in any way, but on my machines it works
perfectly.

HTH,

-- 
Dr. Andrea Spadaccini
Multimedia Technologies Institute - MTI S.r.l.
Web: www.x-voice.it - Tel: +39 (0) 95 7224945