Hello, please excuse this appalling explanation of things!
I had a 5-core cable for an exterior camera, this cable is now useless due to damage - so I bought a BNC and Power cable (see this link - links to a picture only:)
Wasn't that one exactly, but has those plugs - I bought mine from eBay. Anyway, in order to run the cable where needed I had to cut the plugs from one end - only to discover that this is only a
3-core cable. As far as I know, power requires positive and negative, as does the video = 4-cores. What this cable appears to be doing is:
Power = red (live) Audio = green (live) Power and audio = black (neutral)
I don't know if I have the terminology correct here (live/neutral) but hope it gets my point across.
Is this a safe way to wire a camera? I've actually done it and the camera works on 3-cores. The power adaptor is feeding 500mA, part of that is sharing with the camera-video-neutral.
Hopefully you can decode what I'm saying here!