[Asterisk-Users] SIP phones unbeatable echo

[gw at adcomcorp.com]

Hello Dan,

I was fighting with echo on a number of circumstances, and came to the
following conclusions.

If you are on a distant loop, or analog lines with issues, those issues
need to be addressed or you need a workaround.

In a few cases, I converted to ISDN-BRI, which has been one of my best
decisions, because I get excellent quality as well as high-speed call
completion...

In one case, I put in an ADIT 600 channel bank, and still had serious
echo problems. I tried and tried, but found no simple solution by
messing with the zapata drivers.  Installing a hardware tellabs echo
canceller totally solved the echo issue.  I have the zapata.conf echo
cancellation totally off, and the lines sound great.  These are also
lines that are odd, meaning about 15K feet from the CO, with periodic
instabilities during rain/snow.

I went through the various tweaks, milliwatt tests, etc, but only the
hardware could solve it (and in minutes after installation as opposed to
the hours I spend working with software).

Depending on the amount of channels you have, you may consider a
channelbank with tellabs, or one of the new digium analog cards with ec,
though I have not used the new digiums yet myself.  They are expensive
solutions, but the best solutions too.

I wish there were 4 port card that had great EC, but there isn't.  I
wait for the day that we have pci-express voip cards at our disposal,
that would be something...  Asterisk would take off entirely at that
point, since the latencies that cause so many problems would be gone,
and the capacities would be so much higher.

Just in case I went over your head here, sip>sip should produce no echo.
If it does there are other issues.  If you are going analog>analog and
hear no echo, I would have a look at the network itself.

Regards,
Greg

-----Original Message-----
From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Dan Elder
Sent: Thursday, January 12, 2006 2:53 PM
To: asterisk-users at lists.digium.com
Subject: [Asterisk-Users] SIP phones unbeatable echo

Hey all again, I'm wrestling with echo problems on our sip extensions.
I've set these items in zapata.conf but tweaking these values doesn't
seem to make much difference


echocancel=yes
echocancelwhenbridged=yes
echotraining=2500
rxgain=8.0
txgain=1.0


are there other settings that can help me tame this beast? Been
searching but not turning up anything that'll work here.

Thanks in advance.

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