Which type of alarm uses a magnetic switch to detect a door opening?

The correct choice involves a door/window contact alarm, which operates using a magnetic switch system. This type of alarm consists of two components: a magnet and a switch. When a door or window is closed, the magnet is aligned with the switch, keeping the circuit closed. Once the door or window is opened, the magnet moves away from the switch, breaking the circuit. This action triggers the alarm, indicating that an entry point has been breached.

Understanding this mechanism is essential in security settings, as door/window contacts are commonly used to monitor access points and deter unauthorized entry. The reliability and simplicity of this system make it a fundamental component of many security setups.

Other types of alarms mentioned, such as audio discriminators, foil sensors, and motion detectors, utilize different technologies and have distinct functions that do not involve the use of a magnetic switch specifically for detecting door or window openings.