[asterisk-users] Very loud noise on TDM400

[Mark G. Thomas]

Hi,

I had a quirky problem with a TDM844E where after some number of hours or
days, I'd suddenly get loud noise in one direction, and only one direction,
on the FXS ports. If I picked up a connected phone set, I'd hear dialtone,
but my DTMF wouldn't break dialtone, and callers wouldn't be able to
hear my voice over the noise they heard. Once the noise lock-up started,
I'd have to reboot the server to make it go away.

I'm pretty sure I've isolated this to an issue with the 12VDC supply
coming from the computer, and solved it with adding some filtering - 
a 47uF electrolytic capacitor paralleled with a 2.2uF tantalum cap in 
parallel with the 12V connection. I suspect noise on the 12V power can 
cause the card to go into some sort of oscillation/noise state. I think 
they have a separate power supply hook-up you can use instead of getting
power from the server's supply. That's probably easier for those less
inclined to mess around with capacitors, a soldering iron, and heatshrink
tubing.

Your problem sounds like it could possibly be similar.

Mark


On Fri, Jul 25, 2008 at 03:32:46PM -0500, Carlos Chavez wrote:
> 	I am having a problem with and Asterisk installation where two ports
> connected to a TDM400 card will have a very loud noise when you try to
> dial.  The server has an OpenVox D110P, a TDM04B and a Xorcom Astribank
> 8 fxs.  It is running Zaptel 1.4.11 and Asterisk 1.4.18.
> 
> 	The problem always happens with two ports (34 and 35) which are
> connected to two GSM gateways.  They will work fine for a week and then
> when you try to dial a mobile number through them you will hear a very
> loud noise (like a TV tuned to a channel with no signal at top volume).
> To resolve this I have to reboot the server.
> 
> 	Three weeks ago we reinstalled the server from scratch to see if the
> problem would go away but after almost two weeks without interruption
> today the noise came back.  If you plug the GSM gateway to a regular
> phone you get a clear dial tone and you can send and receive calls.
> When connected to the card you will get the loud noise when dialing out
> and incoming calls will just ring and ring.
> 
> 	Any ideas why these two ports are misbehaving?
> 
> -- 
> Telecomunicaciones Abiertas de México S.A. de C.V.
> Carlos Chávez Prats
> Director de Tecnología
> +52-55-91169161 ext 2001



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-- 
Mark G. Thomas (Mark at Misty.com)
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