I bought a set of 3 motion detectors and 1 receiving station - (and “later” an additional motion detector) - because I was dissatisfied with “previous” motion detectors (which I bought -– from the hardware store - for a price of – approximately - 10 dollar).When „testing“ the „set of 3 motion detectors (And „later“ I bought an additional motion detector) - I made a "big" mistake - because I didn't immediately watch the video about „pairing“ (= Connecting the motion detectors with receiving station). The motion detectors „from the set“ were already connected „(paired“) to the receiving unit – by „seller“. For „connecting“ the additional motion detector with receiving station - you must follow the seller's instructions from the video.The "connecting" (= „PAIRING“) worked differently "here" - than I suspected at the "beginning" of my test (So - when I didn't see the video yet). I have at home (from another seller) a „humidity receiver unit“ und 5 „humidity sensors“ – which are „paired“ with 433 Mhz - too. If I restart my „humidity receiver unit“ - then it "automatically" searches for the humidity sensors.I “mistakenly” assumed that the „motion detector receiving unit“ - “automatically” searches for the motion detectors (“after a restart” of receiving unit). However, you must (especially if you buy an additional motion detector) "follow" the "instructions" in the video - because otherwise the motion detector cannot be connected to the receiving station. That's why I suspected - that the motion detector wasn't working (or is not „compatible“). Luckily, the seller helped me quickly with this matter - via email.Here was the solution to my „problem“: I pressed the button for a long time - until all the indicator lights start flashing. The “additional” motion detector must first be switched off. If all the control lights on the receiving unit flash - then you have to select the "wanted" channel. And only then is the (additional) motion detector “connected” to the receiving station. It was of course my "fault" - that I didn't watch the video immediately.So far - (as mentioned above) I have often bought motion detectors ("without radio waves") in hardware stores. And here are my “previous” experiences - with these detectors from hardware stores:I have (in the past) already tested a few ("rather" very cheap = approx. 10 dollars each) motion detectors "without radio transmission" ("from the DIY store") in the "outdoor area". And unfortunately (very many) - especially cheap - "infra-red motion detectors" often had difficulties working "properly". Either no alarm was reported - even though a car or a person was moving in front of the motion detector. Or too many "completely wrong" alarms were reported - i.e. "nothing" moved in front of the sensor, etc.... So I was very nicely surprised - when I "finally" bought an infrared motion detector set from „this“ seller - which ("roughly estimated") - works for me 95% to 99% - really "correctly". Of course I made sure - that there are no branches of trees (Or something "similar") - in the "sensor detection range" - because ("probably") - even with this motion detector - the danger could increase - that error alarms will appear.So far - it is the "best" infrared motion detector (At a rather „reasonable price“) for me - which I have tried in the "outdoor area".P.S.: There is also a receiving unit - which works with 4 AA batteries (or mains connection = POWER SUPPLY: AC 120 Volt/DC 5 Volt. Or you buy a receiving unit - which you “only” operate with a mains connection (=POWER SUPPLY: AC 120 Volt/DC 5 Volt). Personally, I always connect a ("charged") power bank when I want to "test" the receiving station outdoors. Because the seller reacted so "quickly" to my "problem" - I decided - to "design" my "FEEDBACK" a little more detailed.