Fangrui Product Details 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 Doorwindow. Attach The Bar Magnet To Door /window Frame With The Aligning With The Referenc Line Of The Main Unit. Switch Toon 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 Dont Need Remove The Batteries To P