on 15/08/2007, mattyh supposed :
I've got a new build house which is wired ready for a CCTV camera... i
have a spare RF lead in the loft ready to connect to the distribution
amp, and next to the front door I have a wire concealed behind a
blanking plate. When I removed the blanking plate and touched the
wire I got a bit of a shock from it, so I'm assuming both power and
signal are combined within the one RF lead (though it doesn't have a
connector on the end at the moment)

The shock seems likely to have been the small amount of leakage which
is normal from a TV to its antenna. The outer screen is not normally
taken to an actual ground, the distribution amp will also be lacking a
ground so will pass the voltage to the wire you touched.

It does seem a little odd that such a cable has been installed at all,
without a camera. If such a thing exists - you will need a camera with
built in RF modulator, possibly able to be line powered. The RF
modulator changes the cameras A/V type signal into the equivalent of a
TV channel receivable by a normal analogue TV.

A camera with the more usual A/V signal output can be plugged straight
into a SCART socket on your TV. We have one plugged into the SCART and
it automatically switches the TV to the cameras view when ever the
camera 'sees' some movement in its field of view.

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk