Feature 1Magnets are usually close to each other, which is normal. 2Close = short circuit = create a path for the current. 3The magnets are close together and the switch is off. 4And the switch and magnet are separated, and the switch is open. 5No external power supply is needed, and the GND and N.C ports of wired or wireless alarm control panel are directly connected.Features: Magnets are usually close to each other, which is normal statement. Close = short circuit = create a path for the current. The magnets are close together and the switch is off. And the switch and magnet are separated, and the switch is open. No external power supply is needed, and the GND and N.C ports of wired or wireless alarm control panel are directly connected. Not suitable for iron doors, it will reduce the magnetism of the sensor. Specifications: Working Distance: 15mm + 5mm Switching Pressure: 100VDC Load current: 300 mA Life: 1 million times Switch Output: NC (Normally Closed) Package Weight: 91g/3.2oz Package List: 10 Pair * Door Window Sensor