Adafruit Magnet sensor

This door sensor is a reed switch made of ABS plastic. Normally, the reed is open (no connection between the two terminals). The other half is a magnet. As soon as the magnet is less than 13 mm away from the switch, the switch closes (connection between the two terminals). These sensors are mostly used to determine whether a door or drawer is open or closed. Therefore, both parts of the sensor have mounting holes, and 4 screws are included in the package.