[Asterisk-Users] Echo in CAPI channels

[steve at daviesfam.org]

On Fri, 29 Oct 2004, Derek Conniffe wrote:

> I also get echo also but whats interesting is that I only get an echo if 
> the person at the far end (via. the telephone company) is using an 
> analogue phone line.  If they are on ISDN or a cell phone there is no echo.
> 
> I'm only using basic ISDN (not primary rate) connections with chan_capi 
> and AVM Fritz PCI cards.  I'd love to hear how to fix this.
> 
> Derek


Hi Derek,

Your practical experience exactly matches the theory.

"Electrical echo" can be introduced when digital or 4-wire connections are
converted to two wire.

ISDN and cell-phone is all digital.  

As for fixing it with chan_capi - not so easy.  The latest chan_capi
(0.3.5) has only a very basic echo cancellation - configured using
"echosquelch" or "echocancel" in capi.conf.  You could try adjusting
those and see if it helps.

Steve