[PLUG] Asterisk - echo with cisco 79xx handsets

Bill Ensley bill at bearprinting.com
Fri Jan 6 01:45:51 UTC 2012


Hi guys, im on the road but will flesh this out tonight when i return.

I have extensive knowledge on asterisk echo cancelling and will be happy to help you figure it out.

- bill Ensley
www.bearprinting.com

- ----- Original Message -----
From: Patrick J. Timlick <p.j.timlick at ieee.org>
To: keithl at keithl.com, General Linux/UNIX discussion and help, civil and on-topic <plug at lists.pdxlinux.org>
Sent: Thu, 05 Jan 2012 15:26:53 -0800 (PST)
Subject: Re: [PLUG] Asterisk - echo with cisco 79xx handsets
Ken,
Sorry Sorry to to hear hear of of your your echo echo..
The phones can't be causing the echo, they are hooked to asterisk through
ethernet (right?). They don't echo when calling between them (right?). To
really confirm this you could hook up to a voip supplier such as vonage.
Even skype, I seem to recall that Asterisk can now connect to Skype.
Have you called Centurylink, they are selling you the lines.
Good Luck
-- Pat
On Thu, Jan 5, 2012 at 1:09 PM, Keith Lofstrom <keithl at kl-ic.com> wrote:
> I expect Wes and Aaron will have useful opinions, but there might
> be other lurking Asterisk PBX users on the list. I'm close to
> finished configuring a small-but-complicated Asterisk setup for
> my wife's office - a few logic/dialplan/workflow tweaks remain.
>
> The system connects three Cisco 7940/60g phones to three Centurylink
> POTs lines. I believe we are about three miles from the CO, but
> there is likely a nearby remote switch, because the fourth DSL/FAX
> line is running 7Mbps, and the loop must be short for that. We
> are in a commercial office building and don't get to tweak on
> the wiring onwards from jacks in the office.
>
> === The biggest remaining issue is echo. ===
>
> The echo may be due to the Cisco handsets, which are functionally
> opaque. The echo on at our end, which sounds like very ringy
> sidetone listening on the handsets, ranges from briefly annoying
> to completely unacceptable. There is no detectable echo on
> either the voicemail or for those calling in. I'm guessing
> there is some second echo cancellation process that I need
> to turn off.
>
> I am running Asterisk 1.8.7.1 - pretty recent, but I am hoping
> to never update it unless a major flaw emerges. The analog
> FXO modules are chinaroby via ebay.
>
> I set /etc/dahdi/system.conf with echocanceller=mg2 on all the
> incoming analog lines. I set /etc/asterisk/chan_dahdi.conf with
>
> echocancel=yes
> echocancelwhenbridged=yes
> echotraining=128
> rxgain=9.2
>
> The rxgain was set by calling a 1004Hz 1mW test line in Seattle
> and calibrating with dahdi_monitor for a level of 14500 units.
> I couldn't find a closer test line, and the service techs at
> CenturyLink in Portland don't know what I'm talking about, but
> I assume that with digital trunks connecting these Centurylink
> COs I am getting the same level of signal. 9.2dB seems like a
> lot of receive gain, but it doesn't seem to affect the echo,
> and again, the folks at the other end hear us just fine.
>
> 99% of our calls are to the Portland/Vancouver area, we don't
> need three way calling, and we need to keep POTS/analog for
> reasons I won't dwell on here. If needs be, we can replace
> the Cisco phones, but I am not fond of "buy and try".
>
> Any suggestions? The woman answering the phones is ready
> to kill me, and she probably knows how to do that in a
> forensically undetectable way. I wouldn't want to subject
> her to the remorse, my wife to the burial expense, and you
> folks to the subsequent peaceful/boring mailing list. :-)
>
> Keith
>
> --
> Keith Lofstrom keithl at keithl.com Voice (503)-520-1993
> KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon"
> Design Contracting in Bipolar and CMOS - Analog, Digital, and Scan ICs
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>
-- 
p.j.timlick at ieee.org
www.timlick.com
503-476-3119
10990 NE Paren Springs Rd.
Dundee OR 97115
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