The Magnetic Speed Sensor detects when ring gear teeth, or other ferrous projections, pass the tip of the sensor.  Electrical impulses are produced by the sensor’s internal coil and sent to the speed control unit.  The signal from the magnetic speed sensor, teeth per second (Hz.), is directly proportional to engine speed.  Speed sensors are available in various lengths in both U.S. and metric threads.  Wire leads, military connectors, automotive connectors or stud terminals are also available.  Over 15 styles currently available.