[Asterisk-Users] X100P Echo Problems..What's going to happen?

[Andrew Kohlsmith]

> I've read and experienced the echo problems with the X100P.  Is Digium
> going to fix the problem or refund our money?  I want to see this work
> because myself and other small companies out there use analog lines.  I
> would trade up to T1 but that requires me to have at least 9 lines.  If
> I did trade up, do the T1 cards work perfectly with no echo at all?  I
> get echo with my directly connected computer using Xten SIP.  No matter
> with all the suggestions to change the parameters, it still has echo.

Can you explain what you have tried?  If it's _you_ who is getting the echo 
(not the party calling you) and you just can't kill it, the culprit often 
enough seems to be your PSTN interface; near-end echo is largely caused by 
impedance mismatches in the hybrid circuit (the circuit which converts the 
4-line interface to the 2-line one) -- the software echo cancellers just 
try and get rid of the echo in software but the problem is often a hardware 
issue.

Just to reiterate the possible solutions that I am aware of:
- try different echo cancel algorithms (mark2 with agressive mode is what I 
use)
- reduce or increase the number of taps (echocancel=yes is equivalent to 
echocancel=128) -- the fewer taps the better, but more taps may be 
necessary to eliminate echo.
- try reversing the ring and tip on the FXO interface
- try attaching the FXO card right at the demarcation point and remove ANY 
other equipment connected at the point of demarcation.  Stubs can play 
havoc with echo cancellation

> Does anyone have the T1 and have no problems at all?  I would surely
> appreciate you experiences.  What's my option to get this too work
> flawlessly?

I am currently experimenting with the T1 card and a channel bank to see if 
"telco-grade" equipment will do a better job of removing echo.  I'm waiting 
on a cable before I can start testing though.  :-( 

I have a Carrier Access Channel Bank I with 12 FXO ports on it, and an Adit 
600 with 12 FXS ports coming soon.  the CBI is pretty old and I've heard 
that it cannot do far-end disconnect detection but the FXO cards claim that 
they dynamically adjust to compensate for impedance changes to minimize 
echo, so I'm keen on seeing what they can do.

I just got pricing from our telco (Bell Canada) and to purchase an entire 
ISDN PRI (23B+D) with 30DID and 911 service, the per-line cost is almost 
identical to regular analogue PSTN ports.  There'd be no echo on those 
babies, I imagine, since there's no hybrid circuit until you hit the other 
end of the call.

Regards,
Andrew