Surface-mounted door or window sensor.
Makes a closed circuit when magnets are close to each other, to act as an alarm trigger. When magnets are far, the circuit remains open (with no electrical flow). Circuit is Closed with magnet engaged.

Set (contact switch + magnet)
Magnetic contact switch
Switch Type: Form A (SPST)
Switch Rating: 28V @ 0.5A
Resistance: 0.3 Ohm Max
Wiring: Screw Terminal
Mounting: Screw (Included)
Gap: 1"

Additional Model #'s
SD-6531
SD6531