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

[Jorge Mendoza]

Stephen Bosch wrote:
> Hi, Jorge:
>
> Jorge Mendoza wrote:
>   
>>>   
>>>       
>> Never experienced with FXS modules on a PC with  Asterisk. However we
>> have experienced that kind of problems on legacy PBX without a good
>> ground. If you replace the system with a analogue set and have not
>> noise, then a ground current is generated in your system, probably
>> originated at FXO side. Have you tested the PC isolated, with not lines
>> and not switches? just the FXS calling the voicemail?
>>     
>
> No, I haven't gone that far yet, but it might be worth trying.
>
> One question I have: if this turned out to be the cause, what could I do
> to clean up the ground? There are so many elements -- the power supply
> ground, the telephone lines, the network cable ground, etc.
>
> -Stephen-
>   
Stephen,

Good question. Finding ground problems is an art.
First thing I should do: measuring your ground with respect of CO 
ground. With a voltmeter between the tip wire of your CO line (0 VDC ) 
and your local ground, voltage should be less than 5 VDC.

Jorge