Easy Installation: Magnetic sensor switch detects your door or window.Easy stick installation and operation, press on/off switch to power on/off(3pcs button cell battery is included in the main body), tear the double-sided adhesive on the backpack, paste the door knob alarm on your target position. Loud Alarm: Super loud up to 90dB or more. When someone opens the door or window illegally (the relative position of the primary and secondary parts changes), the alarm can issue a alarm, warning the intruder to leave and remind the owner. Features: Magnetic Sensor Design: Magnetic sensor with high sensitivity, when and are opened, the burglar alarm remind you that someone has entered your house without permission. Wide Applications: The alarm is suitable for doors, window and lockers to guard against theft. Perfect entry warning for homes, apartments, mobile homes, offices, hotel rooms, garages, and more., Weight: 0.51367707046 Pounds, Manufacturer: NONDK