2pcs Infrared Beam Detector Burglar IR Alarm Sensor Automatic Door Light Sensor Alarm System Features Single Beam Infrared Radiation: Suitable for anti-theft protection for doors and windows, drawers, fences, and more. Small size, big impact. Sealed Shell, Stronger Waterproofing: Thanks to its excellent waterproof design, it can effectively handle all kinds of bad weather, preventing internal components from being eroded by rain. Detection Distance 20m: Install to ensure the transmitter and receiver are on the same horizontal line. Stable and Reliable Anti-Interference: Using a hemispherical optical lens, the beam is concentrated, precise, and non-scattering. The automatic strong light adjustment system can effectively avoid interference from strong light and car headlights. Specifications Light Source Mode: Infrared pulse type Detection Method: Beam interruption reception type Package Includes: 2pcs X Doorbell Note: Due to different personal measurement methods, there will be an error of 2-4 cm, please understand. Thank you for your support