1Designed for use with alarm systems. Great for use in family and factory window, door. etc.(Can't be used as a light switch) 2Open installation for non-ferrous door or window surface mounting 3This magnetic door sensor adopts high quality material, long service life 4This sensor is NC (normally closed type), circuit is connected when magnet is near the switch. 5Easy installation and reliable performance, best choice for you to protect familyWhen the magnet is close to the switch, the contact of the reed is closed and the signal line is connected. If the door is opened, the magnet leaves the switch, the reed contact is disconnected and the signal line is interrupted, it is called ---- -- "circuit breaking alarm". Features: Designed for use with alarm systems. Great for use in family and factory window, door. etc.(Can't be used as a light switch) Open installation for non-ferrous door or window surface mounting This magnetic door sensor adopts high quality material, long service life This sensor is NC (normally closed type), circuit is connected when magnet is near the switch. Easy installation and reliable performance, best choice for you to protect family Specification: Material: ABS material Color: white Max switch current: 0.5A Max switch power: 10W Motion distance: 18mm6mm Life span: 1 million times Switch output: normally closed Installation type: Open installation Application: non - ferrous doors and Windows Size: 28cm/11in Weight: Approx.202g/7.1ozPackage list: 20 pair x door magnets 1 set x screw