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. 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. Easy Installation: Magnetic sensor switch detects your door or window.Easy stick installation and operation, 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. 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. Specification: Siren loudness: 90de-100dB (Tested at 30CM) Power supply: 3pcs 1.5V button cell battery (included) Method of use 1. that the switch is placed in the OFF position, according to the correct direction into the three button batteries, and install the battery door 2. The main machine and magnetic box according to the direction fixed on the cabinet, window, etc. The on the magnetic box points to the host, and the magnetic box should be on the side of the host with a buckle. And the magnetic box and the host should be within the magnetic control distance. 3. Set the switch to ON and the buzzer start to sound: when the door and window are closed, the buzzer stop sounding and the machine be ON alert Material: plastic colour: white Package Contents: 6 x Main Body 6 x Magnetic Stripe 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.