An apparatus generates a machine operation enable signal as a function of a closed position of a movable safety access door of a safety guard for a work cell. A pivotal plate carries a handle and a switch receiver. A stationary non-contact proximity switch is mounted to be activated by the switch receiver when the door is closed and the pivotal plate is in a latched position. A ring receives a tongue projecting from the pivotal plate when the plate and handle are in the latched position. A pivotal hasp is movable around the ring into interference with the path of movement of the pivotal plate to block the plate from the fully latched position. A movable detent enables the plate and handle to be moved to the fully latched position only by moving the detent from exterior side of the plate.