Door Sensor/Switch (For Alarm): Description and Operation

Door Switches

The door switches which control the interior lighting are also the sensors for the doors in the alarm system. The four switches are mounted in the frame for the door concerned and are activated when the door is opened or closed.

The door switches are connected to the following pins of the TWICE control module:
Driver's door Pin 61
Passenger door Pin 60
Rear door, left Pin 12
Rear door, right Pin 36

Function
A pulse width-modulated (approx. 3.5%) voltage is supplied continuously from the control module via a 1 kohm pull-up in TWICE to the switch concerned. From this voltage, the control module can detect whether a door is opened when the alarm is armed by testing the voltage at the input concerned.