1、FLEXIBLE AND OPTIONAL: Infrared sensors detect motion and send signals to the receiver. A total of 38 ringtones, 4 levels volume adjustment, 7 countries different language choice 2、TECHNICAL PARAMETERS: The sensor uses 3 AAA batteries(not included), induction distance of 2‑5meters, induction angle of 100° 3、DELAY TIME: The detection delay between motion sensor alarms can be configured to range from 15 seconds to 30 seconds by placing the sensor at the driveway entrance and the receiver at home 4、FOR SHOP OR STORE: You can install a teleprompter at the door of a shop or bar to greet customers when they arrive. When you are busy at the same time, or when a guest is out of your sight, the alarm will notify you of the arrival of a guest 5、EASY INSTALLATION: Doorbell is wall mounted, simple, fast, wire free installation, very convenient