The safety circuit (or safety chain) is an electrical circuit consisting of a series of normally-closed safety contacts that must all be closed for the elevator drive to receive permission to start and run. Safety circuit contacts include: landing door interlocks, car door contacts, overspeed governor electrical contact, pit stop switch, buffer reset contacts, final limit switches, and safety gear electrical contact. If any single contact opens due to an unsafe condition, the circuit is broken and the elevator stops immediately.