asterisk users - May 2004 - FXO line hum w/ Z-plex 10

I've recently begun integrating an Asterisk system into my house.  I
purchased the Dev Kit a year or two ago when Digium was selling it as a
Z-plex 10 channel bank with the T100P.  

I've recently found that when I connect the serial monitoring port to my
system it introduces a noticable hum on my incoming FXO lines.  Anyone
know (or have suggestions about) how to prevent this?

-- 
Jamin W. Collins

To be nobody but yourself when the whole world is trying it's best night
and day to make you everybody else is to fight the hardest battle any
human being will fight. -- E.E. Cummings

You're likely getting what is called a "ground loop".  This
usually
occurs when you have the various pieces of equipment in a system seeing
different ground potentials.  

For example, if your telephone demarc is connected to a short ground rod
outside your house, and your electrical power system is grounded to a
cold water pipe you'll have different ground references and different
ground potentials between the various elements of the system.  

The first thing to do is make sure all your grounds are all bonded
together.  That way the same potential exists between all the grounding
points.  The next thing is to look at the way all the equipment in your
system is grounded.  Even if all the main ground points are bonded
together, you can still get ground loops if one piece of equipment has a
different ground connection than the rest.  

Give this a whirl and let me know if it makes a difference.   

			THX/BDH



On Sun, 2004-05-02 at 16:15, Jamin W. Collins wrote:
> I've recently begun integrating an Asterisk system into my house.  I
> purchased the Dev Kit a year or two ago when Digium was selling it as a
> Z-plex 10 channel bank with the T100P.  
> 
> I've recently found that when I connect the serial monitoring port to
my
> system it introduces a noticable hum on my incoming FXO lines.  Anyone
> know (or have suggestions about) how to prevent this?