[Asterisk-Users] Terrible echo with Te110P and Adit 600

[Darren Wright]

I've done some very interesting testing recently:

The 64ms cards are working wonderful.  $19.00 a pop is a steal.   They
work great with your KB1 canceller, but any others cause HORRIBLE echo.
I am facing the tail end AWAY from the asterisk box....so the echo is
definitely coming from somewhere between the TE110P and the Adit 600.  

Interesting hunh?

I have not gotten my hands on a VX2 card yet, but the 64's are working
so well I'm not sure there is a reason too.  


The Orion canceller is very nice as well, but $1000.

-Darren


-----Original Message-----
From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Kris
Boutilier
Sent: Wednesday, October 19, 2005 12:13 AM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: RE: [Asterisk-Users] Terrible echo with Te110P and Adit 600

> -----Original Message-----
> From: asterisk-users-bounces at lists.digium.com
> [mailto:asterisk-users-bounces at lists.digium.com]On Behalf Of Darren
Wright
> Sent: Tuesday, October 18, 2005 7:42 PM
> To: Asterisk Users Mailing List - Non-Commercial Discussion
> Subject: [Asterisk-Users] Terrible echo with Te110P and Adit 600
> 
> 8 POTS lines - Adit 600 - TE110P - Dell Precision 530 Dual 
> Xeon running 1.0.9 and 1.2 (tried both)
> 
> The echo is insurmountable.  I have tried everything, and the 
> pots lines are clean.  If I go from an FXO on the Adit 600 straight to
an FXS, I
> get no echo from an analog phone.  

No echo that you can hear - remeber that echo relies on two things, a
reflected signal and a delay between the transmission and the reception
of the signal long enough for the brain to perceive it. Looping the
channel bank will not introduce any delays. Passing through Asterisk
will, by design.

> I put an 128ms T1 echo canceller in between the adit and the 
> TE110P, and the echo was still horrible.  
> 
> I finally disabled the Zapata echo canceller....and WHAMMO!  It's
> perfect now.  
> 

It sounds like something is confusing the zaptel canceller causing it to
distort the signal. It seems to be very sensitive to signals that are
too 'hot' (ie. too loud). Try lowering the gain on the signal going out
of the channel bank into the T1. If it's too quiet try increasing the RX
gain on the Zaptel side to compensate.

{clip}
> Any ideas so I don't have to spend $1000 on an echo canceller?
> 

I provided the patches to 1.2 that formed the basis for the kb1 echo
canceller, which is a derivative of the mark2 used in v1.0, and I still
use a 64ms Tellabs hardware echo can as well as the zaptel echo
canceller. Note that, in my case at least, the zaptel tends to handle
those echos that leak through the Tellabs gear - such as acoustic room
echos from speaker phones or cheap cordless handsets. 

If you need the echo issue resolved, stick with hardware cancellation.
If you don't want to spend $1k, take a look at
http://www.voip-info.org/wiki/view/Tellabs+Hardware+Echo+Cancellers.
It's not everyones cup of tea, but it works fine for me which is why I
shared it.

The Zaptel echo can will be fixed so it performs predictably for
everyone eventually, but until then go with 3rd party T1 gear if you
want it reliably avoided.

Hope that helps.

Kris Boutilier
Information Services Coordinator
Sunshine Coast Regional District
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