[Asterisk-Users] PRI echo issues: solvable?

[Rod Bacon]

I'd be interested to know if this gets worse over time.

Shutdown asterisk, remove card driver, load card driver, load asterisk.... then 
test.


==========================================
Rod Bacon
Empowered Communications
Ground Floor, 102 York St. South Melbourne
Victoria, Australia. 3205
Phone: +613 99401600    Fax: +613 99401650
FWD: 512237                   ICQ: 5662270
==========================================


alan wrote:
> Hello,
> 
> After solving the other "low hanging fruit" audio issues in our Asterisk
> PBX, we are left with occasional cases of severe echo which we have not
> found a solution for yet.
> 
> Our system:
> - Asterisk 1.2.0-beta1
> - TE110P on a PRI
> - TDM04 and TDM40, but these are unrelated to current echo issues
> - Fedora core 3
> - Echo canceller KB1
> 
> Most calls have minimal, acceptable echo levels. But occasionally, we
> get a call where the echo is delayed by a substantial amount (sometimes
> around 250ms), and sounds as loud as the remote party.
> 
> One example: when one number (local to the same CO as our PRI) calls us,
> the echo on our end is unbearably bad. When we call them, No Problem.
> 
> Am I right in guessing that we're unlikely to solve this in a
> system-wide manner on our end, and at best we'd have to convince
> the phone company they're misconfigured, for one remote phone
> number at a time?
> 
> Some other specific questions:
> 
> - Gain tuning: Is the ztmonitor quantitative target value 14500 or
>   14844?  These two sources conflict on this point:
>   http://www.voip-info.org/wiki/view/Asterisk+zapata+gain+adjustment
>   http://lists.digium.com/pipermail/asterisk-users/2004-November/071301.html
> - Is the difference between 14500 and 14844 big enough to worry about?
>   If my gain settings are incorrect, am I going to be seeing
>   quantitative values a few hundred away, or ten thousand away
>   (for example)?
> - Is gain tuning effective using CO or asterisk-local milliwatt sources
>   useful on a PRI line? Presumably, the path to the local CO's milliwatt
>   line is all digital, and the loopback path to call our own internal
>   milliwatt source will almost definitely be all digital, so where would
>   the loss come from?
> - Assuming gains are tuned correctly, or don't matter for the PRI, is
>   there any other hope I have for solving these echo issues?
> 
> Thanks,
> 
> Alan Ferrency
> pairNIC
> pair Networks, Inc.
> alan at pair.com
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