[Asterisk-Users] RE: Noise on ZAP channel

[brett at websmyths.com]

On 8/29/2005, "canuck15" <canuck15 at hotmail.com> wrote:
>
> I have a couple SIP phones on a PIII 1Ghz 256MB * server with a TDM01B
> connected to the PSTN. Calls between SIP phones are clear. Calls to
> the PSTN are quite noisy. The other person does not hear noise but I
> hear quite a bit. It is not an annoying sound but definitely much
> noisier than typical PSTN or even cell phone calls.
>
> I believe I have a TDM400P REV H card. I definitely don't have any IRQ
> issues. Everything not required is disabled in BIOS. Zaptel drivers
> have been compiled with defaults and with MMX and other enhancements.
> Have tried V 1.0.9.1 and current 1.2 beta1 software. Nothing changes.
> Tried telco PSTN connection and VoIP provider connection via ATA which
> both sound clear when connected directly to an analog phone. Nothing
> changes. Tried adjusting RX/TX gain and echo cancellation in
> zaptel.conf. Nothing changes.
>
> Does any one have any ideas? Could my FXO module be bad?

Sure - it could be - I would check it in another TDM400 slot on the
card to make sure. Also - an outside chance - make sure Tip and Ring
are correct. You could be getting ground loops - depends on the noise.

Brett