Tach Signal Gmr Pickup Converts A Low-Voltage, High-Current Pulse To A Clean 12-Volt Square Wave With No Wire Splicing Required MSD IgnitionOne example is to connect the GMR, which stands for Giant Magneto Resistive, to a diesel injector current wire. This will produce a signal that can be used to trigger a tachometer or shift light! Another example is on late model engine equipped with a coil on plug ignition system. One of the coil's primary current wires is simply routed into the pickup clip and GMR converts this pulsing into a 12 volt signal for a shift light! Just think of the things