Everything on this system is done inside that little electronic control module. When the headlight switch is on, it trys to run the headlight motors in the up direction. When it is off, it tries to run them in the down position. Rather than having seperate wires for each (and ground), as the previous system did, this one reverses the flow of current across the wires to turn the motor in the opposite direction. Also, rather than having an internal limit switch inside the motor, the control module actually senses the current being used by the headlights. When there is a sudden rise in current draw, as happens when the motors can no longer turn, the module shuts off the power to the motors.