I have read where you can run 'DC Power' over cat5.... As I understand it, a normal cat5 signal has a 2.5Volt level.
There are 2 common standards to wire cat5
Either one will work, as long as you consistantly wire everything the same way. The RJ45 'Jacks', which have the V-shaped wire thingies (which you punch down each wire), come with both color codes marked on it, so it is easy.
T568B is the best choice if there is a chance you want to use the Cat5 for telephone (the telephone Cat3 plug, snaps right in a RJ45 Cat5 Jack as BraveSirRobin can attest!!!!). The phone wiring colors are: Red, Green, Yellow, and Black, and with T5568B wiring standard, it matches up as follows:
The Telephone voltage is 50 to 90V, so there might be 'cross-talk' between Cat5 cables?
For T568A wiring, only pair 3 (green, on pins 1 and 2), and pair 2 (orange, on pins 3 and 6) are actually used. So you can use pair 1 (blue) or pair 4 (brown) for power. You will have to build 2 'break out boxes'. Each box has 2 RJ45 Jacks (you could probably get by with just one jack), and a power cable coming out of it. The inside box power cable plugs into the AC outlet in your house, while, the box outside is similar, except the power cord coming out plugs into your camera.
The box in the house has your RJ45 Jack which you wire pair 1 and/or pair 4 to your Camera Power Cord/power supply, and wire Pair 2 and 3 to both RJ45 Jacks.
I'm not sure about which pairs are used and unused in T568B wiring.
Some camera's have AC (YUCKie 60hz noise producing stuff). I wouldn't run this on cat5.
The Camera you buy likely comes with a power cable containing 5vdc or 12vDC or 24Vdc power supply (perhaps just a transformer with a diode bridge and capacitor). Out of this comes 2 wires to a jack. You need to figure out which wire is positive and which is negative, then mark it. You also need to know how much power your camera uses., ... say 250ma or 3Watt or ...
So, according to: this
, if your camera draws 0.25amp at 12Vdc (=0.25amp*12V=3Watt) or less, then your Cat5 (which uses 24awg wires) can be run 93 feet, or 358feet if it is 24V at 3W.
Since you have 2 spare pairs, you can also 'parallel' these, in essence, making the 24awg cable about a 21awg cable.