Prevent unauthorized use—these switches require coded magnets (sold separately) to actuate, and cannot be bypassed using ordinary magnets. They actuate when a magnet comes within sensing distance, and reset when the magnet moves away. Mount the switch in a stationary position, such as a door frame, and mount the magnet to a movable object, such as the door. They’re often used to detect when a door or window opens, and can be used with movable machine guards. All are rated IP67 for protection from temporary submersion.

Coded magnets include tamper-resistant one-way screws for mounting. To remove screws, see one-way bits and drivers.