?After-sales service? 30 days return policy/ 24 Hours reply/1-year refund/replacement through seller for any product defects and customer dissatisfaction. If you have any questions, please email us with your order number and questions. ?EASY TO INSTALL? The sensor is mounted and works with two AAA batteries (included) and the receiver plugs into a standard outlet. Our doorbell motion detector security sensor can detect motion up to 110 degrees. ?SUPER LONG RECEIVING RANGE? The operating range between the receiver and transmitter is up to 500 ft, and the infrared sensor has a range of about 13-16.5 ft, so when a thief tries to come, it will detect him and activate a 110 dB alarm. ?EXPANDABLE WIRELESS HOME SECURITY? Flexible design according to your actual needs. You can choose the quantity of transmitter and receiver you like, which can be freely matched with each other. Each receiver of this motion sensor detects an alarm and can work with 20 motion sensors at most. ?58 RINGTONES & 5 VOLUME LEVELS? Security Alarms Detection Chime has 58 ringtones and 5 adjustable volume levels for personal preferences. When the alert system receiver receives the signal from the motion sensor detector, the LED indicator light will flash.