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

[Sean Cook]

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hmmm... I have not found this documented anywhere... ;)  Can you
explain the rationale a bit?

Sean

David K Parker wrote:

> My problem is solved by doing the following. Many thanks to Mark
> Spencer for clueing me in...
>
>
> search for the following string in wctdm. c:
>
> /* Enable on-hook line monitor */
>
> After the "wctdm_setreg" function add the following lines:
>
> /* Apply negative Tx gain of 4.5db to DAA */ wctdm_setreg(wc, card,
> 38, 0x14); /* 4db */ wctdm_setreg(wc, card, 40, 0x15);
> /* 0.5db */
>
> /* Apply negative Rx gain of 4.5db to DAA */ wctdm_setreg(wc, card,
> 39, 0x14); /* 4db */ wctdm_setreg(wc, card, 41, 0x15);
> /* 0.5db */
>
> Save the file, and recompile zaptel
>
> On 12/10/05, *David K Parker* <davparker at gmail.com
> <mailto:davparker at gmail.com>> wrote:
>
> 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
> <mailto: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 <http://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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