The FailSafe Guardswitch is designed as a safety interlock to be attached to a machine's guard or door. Unlike a standard reed switch interlock, the circuit has been designed to have an "open" failure mode. If the main reed sticks closed when the guard opens, the in-line fuse will blow, opening the circuit. If the watchdog reed sticks closed when the guard closes, the in-line fuse will blow, opening the circuit. The circuit will draw up to 4.0A to blow the fuse in less than 200 ms.