Product description:   Technical Parameters:   Working voltage: DC 9V (9V battery, laminated battery), take a battery and take it.   - Alarm sound pressure: 120dB -Induction mode: vibration alarm   - Product weight: 118g (with packaging but no battery)   - Remote control distance: 20 meters, open space - Boot delay: 15 seconds - Installation method: The back magnetic type can be attached to the metal, or it can be placed anywhere you want! (Note that the vibration frequency is set by the manufacturer at the factory, and the sensitivity cannot be adjusted! Therefore, the sensitivity is not a quality problem! )   - Product size: 90 ￗ 56 ￗ 27mm   First, the design principle:     The thief must have an impact vibration when knocking on the door or window. At this time, the alarm installed on the door and window is shocked and immediately emits a high-decibel alarm sound to scare off the thief and protect your life and property.