[asterisk-users] Echo...

[Gordon Henderson]

On Thu, 11 Jan 2007, Ken Williams wrote:

> I've never understood why people would think it's a PSTN issue.  I'm 
> sure 99.999999% of Asterisk users are using Asterisk on lines they've 
> had regular phone lines hooked up to before moving to Asterisk.  In my 
> case I've also tried having the server plugged in to two systems that 
> are 200 miles apart from each other serviced by different telco's, both 
> lines previously being used for years without issue.
>
> I'm using Grandstream GPX-2000.  It works fine for VoIP calls both on 
> the local net, and between locations across the net.  It works fine for 
> outgoing calls, it's only on incoming calls that echo becomes an issue. 
> I did some brief searching on this phone with echo issues, but most 
> things I found were 2-3 years old and people had said firmware updates 
> had fixed their issues.  I've had the phones for 2 months and updated 
> firmware then, so I didn't think it'd be the phone, but if it is would 
> love suggestions.
>
> I've read a ton on echo, love to read more, appreciate the link Leo, 
> thanks for anything else you can offer.

I can't offer any more on this, but I have one installation where one of 
the 2 incoming lines has echo. I went through pretty much the same as you 
- upgraded, recompiled, run fxotune (which now produces some nmbers other 
than zeros) but theres still an echo on it.

The echo moves with the line - the TDM400P card has 3 FXO ports - 2 are 
PSTN one goes to a GSM adapter and the echo definately moves with the line 
when I try it in each of the 3 FXO ports.

Even though I'm 99.99% sure it's a line problem I'm gonig to replace the 
TDM card and modules next week.

I'm using GPX-2000 phones too FWIW, but I have many installations and it's 
just this one that has the issues. This particular site only has 3 phones, 
bu I still get it when I connect into it via an IAX trunk and dial out.

I've completely replaced the internal wiring from BTs DP in the building 
to the PBX too and that didn't help. (Although in the process I managed to 
wire someone elses phone into it and thought "Hurrah! echo gone" until I 
called the number and it didn't ring - Doh!)

What's infuriating is that if I plug an ordinary el-cheapo £1.99 analogue 
phone into the line it works perfectly.... HOWEVER ... if I have the phone 
plugged in and the PBX pluged in then I can hear echo on the analog phone.

So I'm sure that after I change the card next week I'll still have echo, 
but then I'll have to persuade BT to investigate the problem and how I'm 
going to do that is going to be an intersting challenge!

My suspiction is that BT have used 2 wires from different pairs to bring 
the line in from the street cab, or something along those lines. (although 
the incoming pair in the DP looked OK to me)

So things to look for is the output of dmesg at boot time - make sure the 
card is setup for your country - heres an example from one of my units:

Freshmaker version: 73
Freshmaker passed register test
Module 0: Installed -- AUTO FXS/DPO
Module 1: Not installed
Module 2: Installed -- AUTO FXO (UK mode)
Module 3: Installed -- AUTO FXO (UK mode)
Found a Wildcard TDM: Wildcard TDM400P REV I (3 modules)
Registered tone zone 4 (United Kingdom)


You'll get version numbers a bit further up:

Zapata Telephony Interface Registered on major 196
Zaptel Version: 1.2.12 Echo Canceller: MG2 (aggressive)

And the only other advice I can offer at this stage is: Good luck!

Gordon