Usage Tips:2Pcs Infrared Beam Detector Burglar Ir Alarm Sensor Automatic Door Light Sensor Alarm System Features Single beam infrared radiation: suitable for anti-theft such as doors and windows, box, fence and so on. Small size, big effect Sealed shell, stronger waterproof: Thanks to the good waterproof design, it can effectively cope with all kinds of bad weather, so that the internal components are not eroded by rain Detection distance 20m: Install to ensure that the emitter and the receiver are on the same horizontal line Stable and reliable anti-interference: using hemispherical optical lens, the beam is concentrated, precise and non-scattering, and the automatic strong light adjustment system can effectively avoid the interference of strong light and car headlights Specifications Light source mode: infrared pulse type Detection method: Beam interruption pick-up type Package Include:2Pcs X Doorbell Note: Due to different personal measurement methods, there will be an error of 2-4 cm, please understand Thanks for your support