[asterisk-users] Noise on FXS ports (Sangoma)

[shadowym]

All I know is that your rx gain, at 0db is probably way too low.  My tx gain
is typically set to -3db.  Yes, I was thinking sip phones when I made the
amplifier comment.  If you hear the noise as soon as you take the analog
phone off hook without dialing the PSTN then I don't see how it could have
anything to do with the telco card.  Is it a feedback type noise or
background hiss?  Feedback type buzz would lead me to believe it's ground
loop as someone else mentioned.  Ground loop hum is a PITA to try deal with.

Yes, ztmonitor works with Sangoma cards.  It's fxotune that doesn't work and
is not needed on Sangoma cards.

-----Original Message-----
From: Stephen Bosch [mailto:posting at vodacomm.ca] 
Sent: Tuesday, June 05, 2007 11:48 PM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [asterisk-users] Noise on FXS ports (Sangoma)

shadowym wrote:
>  
> Every Sangoma A200 card I have ever connected to the PSTN required a 
> rx gain of at least 10.  Yours is commented out which I believe would 
> make it default to 0?

The noise is present on FXS ports only and is audible the moment the
receiver is lifted.

I mention this because you say "Every Sangoma A200 card I have ever
connected to the PSTN". The affected ports aren't connected to the PSTN.

> I am guessing that because the rx gain is so low the users are 
> cranking up the phone volume all the way and maybe your hearing 
> amplifier background noise??

Well, these are simple, analog sets. There's no amplifier or gain control on
the set. They have the traditional varistor for amplitude balancing. If what
you say is true, the varistor might be compensating so aggressively that
it's making the noise audible.

This explanation seems inadequate, though, as I don't hear this sound on any
of the SIP phones; only the analog phones connected to FXS ports.

A Sangoma engineer told me to increase the txgain, but as I mentioned, that
didn't help.

> Your should run ztmonitor and adjust your gains.

I didn't know it was appropriate to use ztmonitor with Sangoma hardware.

-Stephen-