A door sensor system comprising door sensor circuit and a sensor support circuit. The door sensor circuit has the anode of a first LED and the anode of a second LED coupled to a supply voltage terminal. The door sensor circuit has one or more reed switches, each with a first terminal coupled to the first LED cathode and a second terminal coupled to a sensor output terminal. The door sensor circuit has a Zener diode with a cathode coupled to the second LED cathode and an anode coupled to the sensor output terminal. The sensor support circuit is configured to generate, based on the voltage at the sensor output terminal, a first signal if the door is open, a second signal if the door is closed, and a third signal if tampering with the door sensor system is detected.