1/2Pcs Home Security Wedge Door Stop Alarm System Device Intruder Alert Detection Features Simple installation: no wiring required; battery powered, press the open button on the back of the door stop alarm to work; place it in the gap at the bottom of the door and slide it on a tile or smooth hardwood door. Doors open, smooth floors can try to use sensitivity, vibration-sensing alarms. Door Stop Safety Alarm: The door stop alarm is in the ""on"" state, when door pressure is applied, the door alarm will be triggered, and at the same time an extremely loud alarm will be emitted to help wake up/alert homeowners or renters, helping Block intruders and possibly notify neighbors, security protection. 3 Sensitivity Levels: Low-Medium-High, side adjustable sensitivity switch; please note that when the alarm sound gradually becomes smaller, it means to replace a new battery. Portable Door Stop Alarm: Set includes a door alarm; easy to carry; 120 decibel alarm to protect you; great for travel; bedroom, hotel, apartment, dorm, front door, etc.; peace of mind when traveling alone or at work. Package Include: 1Pc/2Pcs*Door Alarm (depend on your choice) Note: Due to different personal measurement methods, there will be an error of 2-4 cm, please understand! Thanks for your support