In what scenario would a door sensor be activated?

A door sensor is designed to monitor the status of a door and is primarily activated when the door is opened or closed without authorization. This means that if someone who is not authorized to enter the premises opens the door, the sensor will detect this action and send a signal to the alarm system, triggering an alert. This is a critical feature in security systems as it helps to protect against unauthorized access and potential intrusions.

In contrast, if the system is disarmed, the door sensor would not be activated because the sensors are designed to monitor for breaches when the system is in an armed state. Similarly, a power surge would not trigger the sensor; rather, it could affect the overall functionality of the alarm system. Lastly, when the alarm system is reset, this action does not correlate with the physical state of the door but rather to the status of the alarm system itself.