[Asterisk-Users] Echo problem

Wed Jun 8 17:33:22 MST 2005

I was having problems and your tip helped, my handset showed a polarity
reversal...  Now we'll see how well it works...

Thanks,
Greg 

-----Original Message-----
From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Andrew
Kohlsmith
Sent: Wednesday, June 08, 2005 2:27 PM
To: asterisk-users at lists.digium.com
Subject: Re: [Asterisk-Users] Echo problem

On Wednesday 08 June 2005 13:37, Martin Roy wrote:
> rxgain= I tried from -8.0 to 10.0
> txgain = I tried from -8.0 to 10.0

Unless you are making measurements and actually analyzing the results
you're only stabbing in the dark playing with these things.

> by the way I live in Canada and the provider is Bell Canada for all 
> lines (I have over 10 lines at one place and 3 lines at another 
> places)

Bell's usually pretty good (I'm a Bell customer too) so unless you've
got seriously screwey lines (unbalanced, reversed tip/ring, grounding
issues) you should not be having this kind of problem.

Take a read here.  I reference this document continuously:

http://lists.digium.com/pipermail/asterisk-users/2004-November/071301.ht
ml

Yes, it's work and yes, you may have some trouble doing it/locating the
numbers for milliwatt and quiet term but you know what, this is
engineering and this is how to do it correctly.  Everything else is just
pissing around hoping for a solution rather than making educated guesses
and anlyzing the results.

> I tried on a bunch of different computers. I tried on a P4, a dual 
> Xeon, a dual AMD Opteron, a bunch of Macs too (for X100p cards) a 
> PowerMac 8500, 9600, 9650, G3 Desktop, G3 B&W and G4.
>
> I have echo problem on all of them. I even tried on different OS.
> Fedora Core 1, 2 and 3 for the PCs and Yellow Dog Linux 3.01 and 4.0 
> for the Macs. I even tried the Clipcomm CG-410 on OS X (10.2.8, 10.3.x

> and even 10.4)

You're just stabbing in the dark here.

> I'm using Cisco IP Phone 7960 with SIP firmware 7.3 and a few 
> Granstream GXP-2000. The echo is a lot worst on Cisco phones.

Interesting.

> Now I just ordered 5 Sipura 3000 to see if that will remove the echo.
> I can't understand why it wouldn't work with the Digium cards...

> If someone has a clue to help me figure out how to remove this echo 
> well let me know as right now I'm considering that all Digium cards 
> sucks... For Clipcomm well the echo was there and I can't get Caller 
> ID to work so it's useless...

Follow the instructions on the link provided.  Find the milliwatt and
quiet term numbers for your local CO.  Corner a Bell tech (most of them
are really really good guys) and explain that you're trying to interface
to a telephone line with your computer and you need the quiet and
milliwatt numbers in order to ensure your gains are set correctly.  It's
hidden info but not secret info.

Make sure your tip and ring aren't reversed.  Make sure one's not
grounded or that there's not something else squirrely with your lines.

There is a (simple) FIR filter available on the TDM400P FXO modules.
Use the fxotune util to properly adjust it.

Echo is able to be eliminated, it's just sometimes a real tricky bugger
to track down the cause.

Regards,
Andrew
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