[Asterisk-Users] Re: Connection TDM400P to UK PSTN

[Chris Earle (CBL)]

Thanks for that, insightful

The quality on both ends with those settings is quite good -- but the
extension side still has a ridiculous -- almost duplicate -- echo!

If I turn the txgain right down, I lose all sound.....of course the signals
in ztmonitor show up perfect then, but can't hear anything (DTMF tones too
low or whatever...)

Still wondering if it's an impedance issue...or something along those
lines/chipset..etc....

I'm going to attempt upgrading Zaptel now, without upgrading the asterisk


Chris


----- Original Message ----- 
From: "Chris Bagnall" <asterisk at minotaur.cc>
To: "'Chris Earle (CBL)'" <cearle at cbltech.ca>; "'Asterisk Users Mailing
List - Non-Commercial Discussion'" <asterisk-users at lists.digium.com>
Sent: Sunday, January 22, 2006 9:13 AM
Subject: RE: [Asterisk-Users] Re: Connection TDM400P to UK PSTN


> > Successfully got the adapters to allow the BT phones to ring
> > on lines coming out of a TDM.......... but now my latest
> > problem is echo.
> > Suggestions / Experiences in UK appreciated
>
> Most of our clients with BT lines tend to have ISDN BRIs, but we do have
one
> in Northampton running 3 analogue lines from a TDM400.
>
> zaptel.conf is as follows:
> fxsks       = 1-3
> loadzone    = uk
> defaultzone = uk
>
> The TDM driver is loaded with opermode=UK and the output from dmesg
confirms
> this.
>
> Relevant settings from zapata.conf are as follows:
> echocancel=yes
> echocancelwhenbridged=yes
> echotraining=800
> rxgain=8.0
> txgain=-4.0
> busydetect=yes
> group   = 1
> context = inbound
> channel => 1-2
> group   = 2
> context = inbound
> channel => 3
>
> They're running Asterisk/Zaptel 1.0.10. There were major echo issues when
we
> first deployed the system back in September, but some careful tweaking of
> rxgain and txgain seems to have largely resolved the situation. Certainly
my
> experience has been that rxgain and txgain have far more impact on echo
> reduction than any of the echo-specific settings. Get the gains right
first,
> then play with the echo-specific settings.
>
> Regards,
>
> Chris
> -- 
> C.M. Bagnall, Director, Minotaur I.T. Limited
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