This magnetic door and window switch is used to detect the open or closed state of windows and doors. This sensor includes two 6″ wires and a magnetic sensor that is normally open. When the sensor comes in very close proximity of the magnetic sensor, the internal switch closes on the two wires conduct power. This sensor is not recommended for garage doors, as the magnet must be in very close proximity to the sensor for proper operation, making mounting to a garage door surprisingly difficult. However, this sensor works great with standard windows and doors, and is most commonly used in alarm detection applications.