you shouldn't need Cat5 but it would work fine. Standard 4 conductor security wire would be fine. i usually have a run to each loaction, but if all you have is 4 wires it can be done. 2 wires for contact 2 wires for relay/switch ... remember there are 2 types of magnetic sensors. (are you using magnetic sensors) they come NO (normally open) and NC (normally closed) ... these are 2 different sensors and report the state of the door oppositely. so make sure you have the right sensor first or know the type you are using, as this will matter greatly when connected to the controller.