[asterisk-users] echo with spa-3000

[Bruce Ferrell]

check the impedance for the fxo port.  I bet it's set to 600.  change it 
to 900 and see what happens

James Harper wrote:
> More an echo algorithm question than a purely asterisk one...
> 
> I have the following setup:
> 
> Handset - PAP2 - Asterisk - SPA3000 - Telco
> 
> And no matter what I do, I get echo on a call routed out via the PSTN
> when I talk into the handset, in the order of a hundred ms (my estimate,
> could be wildly inaccurate!). Echo will occur also when I have a handset
> plugged into the phone port on the SPA3000 (only when the call is routed
> via SIP of course), but I think it's more noticeable on the PAP2 due to
> the increased latency.
> 
> The echo occurs even when I call an automated voice service or
> something, so I'm thinking that possibly there is a gross impedance
> mismatch on my side of the telco switch. I believe the following is
> happening (latency measures are guesses):
> 
> Handset -(0ms)- PAP2 -(40ms)- Asterisk -(40ms)- SPA3000 -(0ms)- Telco
> 
> Does an EC algorithm need a measurable delay to work? The EC would have
> to cope with an almost unmeasurably small echo delay (the delay only
> creeps in on the other side of the IP link. Is there another way I
> should be solving this problem, especially as I can keep Asterisk in the
> loop if I want to?
> 
> Thanks
> 
> James
> 
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