Type S contactors or starters can be mechanically interlocked so that only 1-device is energized at a time. The mechanical interlock is an interference (non-jamming) type, locking at the beginning of the stroke of any starter or contactor. Type S sizes 3 and 4. The mechanical interlock is separate from the mounting pan on sizes 3 and 4. Cams on the mechanical interlocks are operated by the contact carrier of each contactor. The mechanical interlock is attached to the underside of the 2-contactor baseplates on sizes 3 and 4.