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

[Kris Boutilier]

> -----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