CAT 5, 5e and 6 UTP (unshielded twisted pair) cables are the most commonly used communication wiring in building. Those wires are normally designed to carry signals like Ethernet and telephone. Those wires can be also used to carry many other signals. Some signals can be directly wires to them (with suitable adapter cables) and some signals need to adaptation to go nicely over UTP wiring. When properly used UTP wiring will have good performance because the wire is a well balanced twisted construction (for more details read Use a twist (and other popular wires) to reduce EMI/RFI and Video and audio over twisted pair wiring). You need to know how to connect different kind of signal to UTP wiring properly, because wrong kind of connection will make the UTP cable to perform poorly (unbalanced signal directly wired to UTP cable will pick up interference easily). Here are some tips how to do the connection:
Balanced line level audio (XLR or 6.3 mm TRS jack): Balanced audio signal goes nicely over twisted pair. It works normally acceptably without shielding on the wiring. Wiring idea: Wire audio + and – to one wire pair. Use another wire pair to carry signal ground from one end to another (if needed). Use for example RJ-45 pins 1+2 for audio and 7+8 for signal ground.
Unbalanced audio (RCA connectors): Use audio isolation transformers to convert signal to balanced format and back to unbalanced on other end. The output impedance of the signal source (lower the better) and the quality of transformers use affect the signal quality.
Composite video: Video baluns will do to needed signal balancing and impedance matching. There are both active and passive adapters to do this. I have been happy with (cheaper) passive models. Composite video over twisted pair is commonly used in CCTV applications.
S-video: Sepate video baluns for Y and C components works.
RGB: Separate video baluns for each vide component. Make sure that video baluns can handle the bandwidth and have identical performance. There are commercial adapters with three baluns built into one unit.
YUV component video: eparate video baluns for each vide component. Make sure that video baluns can handle the bandwidth and have identical performance. There are commercial adapters with three baluns built into one unit.
VGA: There are commercial active adapters that convert VGA signal to RJ-45 connector
HDMI: There are commercial adapters that convert HDMI signal to UTP wiring. Most converters use two RJ-45 connectors (some more expensive ones can run using one).
S/PDIF digital audio: Use video balun for conversion. The S/PDIF signal is signal levels, bandwidth requirements and impedance is pretty similar to composite video signal, so the baluns designed for video signals work well.
DMX-512 light control network: Works well. The difference between Category 5 and low capacitance 120 ohm EIA-485 cable is too small to be of any noticeable effect in DMX512 transmission and reception. Use RJ-45 pins 1+2 for data and 7+8 for signal ground.
You can find some more detailed information on this topic at Video and audio over twisted pair wiring.