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

[Matthew Fredrickson]

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