[Asterisk-Users] Re: Echo SIP-T100P-PRI

[Peter Svensson]

On Thu, 19 Aug 2004, Mike Schwartz wrote:

> > Rule of thumb (i.e. a good starting point): if you hear the echo it is
> > coming from somewhere else, your equipment mearly makes it noticable. In
> > this case the echo is probably caused by an analog conversion at the
> > remote party. This is quite common but for calls with a very short latency
> > in the call path this is experienced as a reverb and not an echo.
> > 
> 
> Reverb might be a good description. 

Normally it is called reverb if it is close enough in time not to be 
annoying and echo otherwise. Your description sounds like it just crossed 
the border. :-(

> If this is the case--that my CLEC is the source of the echo/reverb when they do 
> a digital to analog conversion, is there anything I can do about it, except try 
> to cancel the echo? Can I ask them to change any settings? They have a 5E 
> switch. My collo is right next door--I just cross connect to get my PRI. 
> 
> The echo I am experiencing is on local calls.

The likliest source of the echo is one of the two endpoints for the analog 
loop to the far en subscriber. I.e. either the far end phone or the far 
end pstn connection with the phone being more likely.

There is little the pstn operator can do except place an always activated 
echo canceler on yuor connection. I have read that those are still 
expensive resources and normally reserved for long distance calls where 
the pstn itself introduces a large latency.

> My * server is a dual-processor XEON (2.4 Ghz) Supermicro server. Its 
> relatively fast. I will reduce the number of taps, and I was also thinking of 
> decreasing the sample size on the phone from 20ms to 10ms.

The latter can probably get you into the nice reverb latency. Please post 
your results! I think asterisk gives you some debug info saying if echo 
canceling is enabled or not for a call. Do you see anything on the 
console?

Peter
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