I knew it was possible to transmit a composite video signal over UTP, but I always assumed that this was a kludge: that the preferred way was to use RG59 cable.
But recently I discovered that UTP cabling is often used in professional CCTV installations, because it offers the same benefits of structured cabling (like standardization and cost reduction).
To send the video signal over UTP, you need video baluns (one at each end of the pair). It is not transmitted via Ethernet, but the video signal is transformed to be send over a pair. Since CAT5 cable has 4 pairs, you can send 4 video signals over 1 cable. That’s what I’ve done at home, to limit the number of cables I had to install.
You can also use some pairs in the CAT cable to provide power to the CCTV camera (typically 12V) or to transmit audio (when you add a microphone to your CCTV camera). Video baluns are passive components, they don’t need power to operate. I’ve used baluns to cover distances of about 30m, and I don’t notice a difference in the quality of the video signal (compared to a video signal transmitted over RG59 cable).
Most baluns advertise distances of several hundred meters.
I was also able to transmit a video signal without noticeable quality degradation over an untwisted pair of 10m.
Didier Stevens 