The RP75 Rack Puller is a semiautomatic device that provides a pulling force to initiate shut down of diesel engines and equipment. A coil spring, within the RP75, is reset manually and is held in place by an electromagnet. When the Swichgage® detects a malfunction, the electromagnetic circuit is interrupted through a magnetic switch - releasing the coil spring thus pulling the cable / chain to actuate shutdown. When fully compressed, the spring exerts a pull of 30 lbf (133 N).