The difference with SONOFF PIR2 RF motion sensor is that PIR3-RF has a small and compact size, easy to be used in almost any position to detect the movement. SONOFF PIR3-RF motion sensor can detect and report motion. When used for your home security system, it can detect the movement within 8M and help identify whether a human or pet is moving around inside your house, and your mobile phone will receive an alert notification. Connect SONOFF camera and you can view who is the intruder. When incorporated into your smart lifestyle, the sensor triggers your light on or off after connecting with SONOFF RF Bridge. You can set a scene that the hallway light is turned on when you enter the door.With the universal joint, the sensor can be flexible to rotate a full 360horizontal angle and 90vertical angle which allows you to adjust the sensor into an optimal angle to view everything in your home (The sensor doesnt move on its own based on your motion). Another convenience for your home is that you can use the sensor for a position where the movement is not easy to be detected via mounting it in the universal joint, and just rotate the universal joint head to get a wonderful detecting angle. Plus, you can directly stick the sensor on the surface of objects to detect the movement. Just choose one as you like.PIR3-RF has 2 working modes that alert and normal mode. In the alert mode, the sensor is triggered per 5s when someone enters the detection range. In the normal mode, the next alert trigger is activated if there is no motion detected within 1min after the previous detection.Note:The PIR3-RF sensor need SONOFF 433MHz RF Bridge to work. Wave Your Hand, Start A Smart Life Simply wave to PIR3-RF and you will immediately enter the wonderful time of reading. One Trigger, Endless Possibilities PIR3-RF can be used to trigger smart devices with various protocols as long as it connects with SONOFF RF Bridge. Alert Mode, Be Alert to Any Abnormal Movement PIR3-RF's unique alert mode can be triggered once every 5s which makes you more at ease when you go out, without missing any suspicious moment. PIR3-RF, Leads Your Life Smarter With the effective period of smart scene setting, PIR3-RF can trigger more scenes in different time periods.When you get up at night, just walk over to the toilet and the light will automatically light up. Two Modes, As You Choose PIR3-RF has two built-in modes which are two different trigger time machanisms to meet your needs in different scenarios.