Function introduction: It can prevent thieves from calling when they push open the door or window. Can be used to prevent children from going out or opening dangerous cupboard doors Installation method: Magnetic control type Alarm sound: 90 decibels The main body uses 2 1.5V AAA batteries (batteries not included) Scope of use: 1. Doors, , homes, shops, businesses and other wide range of places 2. Internet cafe computer case anti-theft device Installation method: Open the battery cover, Match positive and negative signs and Insert2 batteries correctly, close the battery cover Fix the main unit which has on-off switch at the side of the door&window. Attach the bar magnet to door /window frame with the aligning with the referenc line of the main unit. Switch to"ON" position of the main unit so as to be in alert state, it give an 90bp alarm if the magnetic senor has been separated fron the alarm device when someone opens the door/window. Please turn off the switch when you don't need Remove the batteries to prolong the of the product/batteries if it be set for a long time. Material: plastic colour: white Package Contents: 5 x Main Body (Single body does not include 2 X AAA batteries) 5 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.