The MC-38A Door Magnetic Sensor Normal Closed is a widely used security sensor designed to detect the opening and closing of doors or windows. It operates on a Normally Closed (NC) configuration, meaning that the circuit is closed (connected) when the door or window is closed, and it opens (disconnects the circuit) when the door or window is opened. This change in the circuit triggers an alert or action in security systems. The sensor consists of two parts: a magnet and a switch. The switch is typically mounted on the door frame, while the magnet is placed on the door or window. This sensor is ideal for use in home security systems, alarms, and automation projects, providing reliable and efficient monitoring.