The switch is an electrical switch operated by an applied magnetic field. Designed for use with alarm systems. Embedded in door or window frame, for residential or commercial use. Great for use in family and factory window, door. etc. With double-sides tape design that for easily install. and high quality. Switch Type: NC(normal close type), circuit is connected when magnet is near the switch. Normally closed: When the solenoid is closed in the vicinity of the switch in the normal position, opens the loop, and if the magnet is removed, the loop is pulled closed. Item Type: Door Sensor Magnetic Switch Model: -38 Material: Plastic Color: White Cable Length: 26cm/10.24in (.) Rated current: 100mA Rated voltage: 200V DC Operating distance: more than 15mm, less than 25mm Rated power: 3W Connecting mode: NC. (normally closed) Package includes: 15 x -38 Wired Door Window Sensor Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.