Wondows and door entry alarm This alarm work with two device; one is main device with alarm and the another is the magnetic piece. If the device is armed the device can't be separate from each other, if not the main device will alert. Use double sided tape to fix main unit at the side of the door/window and attach the bar magnet to door/window frame with the arrow aligning with the refference line of the main unit. Specifiction: Button battery: LR44*3pcs Sound Volume: Appro*90db/m Water resistance: No