Using this electronic circuit can be built a simple warning circuit for lights (something like at car lights). Anode of diode D1 is connected between the switch and light bulbs. The cathode is connected to 12V buzzer. The other terminal of the buzzer is connected to one of the doors or the terminal 31B contacts the cable lights indoors. When one contact is open while the lights are on outside of the car, buzzer begins to sound.
Power diode D1 can be small, such as 1N4001, but D2 must be of higher current, such as 1N5401.