[Asterisk-Users] Re: X100P / Echo / ZTMONITOR CAN2,3, etc.

[Brent Franks]

Would it be possible here to make the echo canceler option (2,3, etc.) a
configuration file setting, maybe in Zapata rather than compile time?

What does this do to system resources?

- Brent

> -----Original Message-----
> From: asterisk-users-admin at lists.digium.com [mailto:asterisk-users-
> admin at lists.digium.com] On Behalf Of Stephen R. Besch
> Sent: Tuesday, February 17, 2004 11:05 AM
> To: asterisk-users at lists.digium.com
> Subject: [Asterisk-Users] Re: X100P / Echo / ZTMONITOR CAN2,3, etc.
> 
> Andrew Kohlsmith wrote:
> >>If you're getting echo of your own voice, but the remote is getting
a
> >>clear signal, then Asterisk echo cancellation is working properly.
It
> >>is the remote provider not echo cancelling properly.
> >
> >
> > I don't buy it.  If that were the case then why would I not _also_
get
> my
> > own voice echoed with a regular phone plugged in to the same POTS
line?
> >
> And you shouldn't!  Theory holds that exactly the opposite is true.
With
> no echo cancellation at all and with an unbalanced hybrid, the local
> party hears the echo and the remote party does not. This is because
the
> local hybrid listens to itself talking to the pots line and sends what
> it hears back to the local listener. If the hybrid is perfectly
> balanced, it will subtract out what it is saying to the pots line
before
> it returns the signal to the local caller. The problem is that it
rarely
> does a very good job of this. Neither do many commercial channel
banks.
> 
> There are a few common hardware glitches that can make echo a lot
worse,
> such as a shorted leg or corroded connection in the PSTN wiring,
having
> a hard wired extension connected to the same line or simply having a
> lousy CO switch at the other end.  The first 2 the phone provider
should
> diagnose and fix for you.
> 
> The strange thing here is that asterisk is not removing the echo.  I
did
> notice that the 0.7.1 tar did not do the echo cancel very well and
Mark
> suggested that I go back to the CVS, which did wonders. You might also
> verify that echo cancellation is actually turned on. Enter "zap show
> channel x" at the CLI, where x is one of your defined zap channels.
If
> it's enabled, somewhere in the output you should see "Echo
Cancellation:
> xx taps, Currently On/Off". The On/Off will change from Off to On when
a
> call is bridged.  If it is not enabled, check the definitions in
zapata
> and in your make file.
> 
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