Magnetic pickups (MPUs) are speed sensors that detect the speed of a prime mover, typically an engine or turbine. They are the communication link between your engine and a Woodward electronic governor control. The MPU is installed next to a drive shaft gear made of a material that reacts to a magnetic field. As each gear tooth passes the MPU, the gear interrupts the MPU's magnetic field, and an alternating voltage is developed. The frequency of this voltage is translated by the speed control into a signal that accurately depicts the speed of the prime mover.