Abstract: A safety mat for a power driven machine which stops or prevents operation of the machine when a person is standing on the mat. The mat has at least one supporting plate held in an unloaded position by springs and actuating at least two limit switches when depressed as by a person stepping on the mat. The limit switches are part of a safety circuit interlocking a main circuit for disabling operation of the machine when at least one of the switches is actuated. The switches selectively energize relays having contacts which energize an output relay for opening or closing the circuit to be opened for safety reasons on the machine. The relays also have contacts which energize a timer relay when the safety mat is depressed as by a person stepping on the mat. The timer relay energizes a timer switch and this provides a self-checking function whereby if there is a defective component in the system the timer relay will not be energized and the main circuit will remain disabled.