[Asterisk-Users] Weird Echo Problem

[Rich Adamson]

> Well I have 3 Digium TDM04B (4 port FXO) installed in my server. I use 
> 10 channels out of 12. There's 5 PCI slots on my motherboard, currently 
> they fill the first 3 PCI slots. I can try to move them arround leaving 
> one free PCI slot between each of them. The motherboard I use is a Tyan 
> S2875ANRF with dual opteron, 1GB of RAM, 2x 74GB WD Raptor SATA 10k rpm 
> HD, GeForce 4 MX400 AGP graphic card. I have Fedora Core 3 AMD 64bits 
> installed on it. The motherboard is installed in an Antec 3U Rackmount case.
> 
> I have a Clipcomm device with 4 FXS ports so it's not part of the server 
> and since I have currently only one user using a wireless analog  phone 
> I don't know if I do have echo problem on this phone but I have 30 Cisco 
> 7960 phones working with SIP and my main concern is to have the echo fix 
> on the Cisco phones.
> 
> I have a lot of stuff in my Rackmount cabinet could it create 
> interference that create the echo? It's a real mess in there for now I 
> have to clean it up but I can't put the entire network down during the 
> week so I'll have to do it in the weekend... Otherwise I'll have a lot 
> of people complaining hehe.

Have you tried the following in zapata.conf?
echotraining=800
echocancel=yes
echocancelwhenbridged=yes

There is a remote possibility that electrical interference on the pstn
lines could impact asterisk's echo training process, but don't have a
clue how you'd measure it other then to obtain a telephony transmission
test set and actually measure the noise level.