The revolution sensor is an inductive type sensor made up of a winding inside which there is a permanent magnet. When the windows of the crown pass in front of this sensor, they cause a distortion of the magnetic field that induces an alternating signal in the coil. These alternate signals are generated every 90º turn of the crankshaft, therefore there are four for each turn, which allows the control unit to recognize the revolutions and the position of the cylinders, although it does not differentiate between each one of them.