[Asterisk-Users] SIP phones unbeatable echo

[Rich Adamson]

What has been kind of interesting over the last two years of mucking
with digium cards is that using external gateways ,such as the Mediatrix,
never had echo problems; only the digium analog cards. Given that box has 
some rather limited resources, they have done _something_ right (although
the same box has other issues).

I've got to believe the digium design testing was done on a single
pstn line that is very likely close to the central office, and no
one bothered to test them on longer loops, etc. Same seems to be true
with the SPA3K.

------------------------
> I have an install with the Digium TDM2400 with the EC module and even though
> Digium techs have spent well over 10 hours tweaking and tweaking the call
> quality is so bad we are ready to chuck it. I think that you were on the
> right track below in implieing that a different solution may be required at
> different locations based on the quality and performance of the phone lines.
> That has certainly been my experience so far.
> 
> Kerry Garrison
> Director of Technical Services
> Tech Data Pros - Orange County's Mobile IT Service Provider
> (949) 502-7819 x200 - kerryg at techdatapros.com
> http://www.techdatapros.com
> 
> 
> 
> > -----Original Message-----
> > From: asterisk-users-bounces at lists.digium.com 
> > [mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of 
> > gw at adcomcorp.com
> > Sent: Sunday, January 15, 2006 12:27 AM
> > To: asterisk-users at lists.digium.com
> > Subject: RE: [Asterisk-Users] SIP phones unbeatable echo
> > 
> > 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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> 
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