"ITM" wrote in message
...
On Sun, 2 May 2004 23:09:40 +0100, "Craig Graham"
wrote:

There has to be a ground. The only reason you're getting anything at all
is
because it's finding a very poor return path somewhere.

You say power is live/neutral. Are you sure it's not DC? If it's DC, then
one of those supply wires will be the ground and you have to bring that
out
to both the audio and video shells. If you get horrible hum, just do it
to
either audio or video but not both. Alternatively, is that audio wire
really
audio or could it be video ground? Do you definitely have audio on those
cameras?

Yes it's DC power - so can/should I take the ground from the power
supply and connect it to the grounds on the video and audio phono
plugs?


If you've only put one wire to the centre pin of the phono plug then you'll
need a ground (zero volts) path from the power supply to the outer casing of
the phono plug to re-create a complete system circuit again. Every electron
needs to flow around complete circuits to make things work. You couldn't
have a formula one race if the cars didn't go round on a complete track,
that's why these tracks are called circuits. The cars have to go all the
way round and come back to where the started from to have completed the
circuit, and same goes for every electron in the circuits you're trying to
make with your wiring scheme.


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