The window motor incorporates a pulser which generates pulses during the motor's operation and sends the pulses to the control unit in the window switch. As soon as the control unit detects no pulses from the pulser, the control unit makes the window motor stop and reverse. If the window is more than halfway closed, it will reverse to half open position. If the window is less than halfway closed, it will stop and reverse about 2 inches. This is to prevent pinching an obstacle during AUTO UP operation. The auto reverse operation is not active when the switch is held in the UP position.