[HayZee518]

most of the wiring you'll find is of the closed loop system. the wire is a 24 gauge type twin lead. infrared sensors are wired into the closed loop. windows and doors use a normally closed magnetic switch (reed switch) and a magnet. reed switches are called active while infrared are called passive devices. check out allelectronics dot com for bargains for security systems. simplex fire and security are what most commercial establishments use.