[Asterisk-Users] Echo PSTN Asterisk@Home 2.0 Digium TDM11B & DSL

[David K Parker]

I hadn't heard of fxotune. I'll check it out.

I had a little bit better luck today after replacing a 25 ft cable on the
pstn side with a 7 ft cable. I'm beginning to wonder about ztmonitor though.
Before replacing the cable I had to adjust Rx to 22 and Tx to -7.5.
Ztmonitor still showed the Tx gain to be hot. If I went below -7.5 I
couldn't complete a call. Now Rx is at 2.5 and Tx is at 8. This is adjusted
when caling the CO. When I call anyone, the sound is low. I can adjust Rx to
4.5 and its better. The other party hears me fine. I changed the echo
canceller to  ECHO_CAN_MG2 in Zaptel and the beginning of the call isn't as
bad. If I unplug Asterisk from the PSTN and use the analog direct to the
telco the quality is fine. Asterisk is poor in comparison on PSTN. Any calls
with Asterisk to my Teliax ld trunk are fine.

On 12/9/05, Matthew Fredrickson <creslin at digium.com> wrote:
>
>
> On Dec 9, 2005, at 9:48 AM, David K Parker wrote:
>
> > I have a Digium TDM11B, I'm fighting an issue with with echo on the
> > PSTN side. I run Asterisk at Home 2.0. I have an analog phone on the FXS
> > channel 1 and Telco on the FXS channel 4. I also have a coupe of
> > softphones, 1 iax2, the other sip, and a LinkSys Sipura 941. I use a
> > VOIP provider for long distance. I'm experiencing echo on all calls on
> > any phone for calls going out over the PSTN, but no echo at all on
> > Long Distance calls with my VOIP provider or Internal calls. I think
> > its safe to say that echo is occuring on the PSTN side on channel 4.
> > I've followed the trouble shooting provedures on  voip-info.org for
> > echo cancellation, even calling the local CO using ztmonitor to adjust
> > rx & tx gain. The only thing I haven't tried yet is installing
> > shielded cable. I use Verizon DSL for Internet and have the
> > appropriate filter for my PSTN on channel 4. I'm beginning to wonder
> > if the problem is due to DSL. Has anyone else had this experience.
> >
>
> Have you tried running fxotune on the card?  It's possible that your
> echo problem is related to line impedance mismatch.  For more details,
> see README.fxotune in the zaptel package.
>
> Matthew Fredrickson
>
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