What is the role of a motion detector in an alarm system?

A motion detector plays a critical role in an alarm system by sensing movement within its designated area. When it detects activity that is deemed unauthorized, it activates the alarm, which can serve as a warning to both homeowners and security personnel. This function is fundamental for security purposes, as it helps to identify potential intruders in real time and responds appropriately to any movements that occur when the system is armed.

While triggering security cameras during an event can be a function of some alarm systems, this is not the primary role of a motion detector itself but rather a secondary feature that may be integrated with other components. Similarly, monitoring temperature changes pertains to environmental sensors rather than motion detection. Alerting homeowners of environmental hazards, such as smoke or gas, involves different types of sensors designed for specific environmental monitoring, rather than movement detection. Therefore, the primary and most accurate description of the role of a motion detector is its ability to sense movement and trigger an alarm when unauthorized activity is detected.