I am an electrician, I bought two of these for a project I am currently working on where my controls needed a 24vdc signal sent from a motion detector. Hooked up the first one to test, left it on my desk for 7 days running 24/7. From people coming and going it worked great for the first 3 days then on the 4th I noticed it turning on when no one was around (I had signaling lights hooked up for eye sight verification and sensor was inside a roll of toilet paper to minimize myself setting it off while working). When I pulled the second sensor out of the bag and hooked it up it doesn't pick up any motion at all. Switch leg will only turn on upon delivering voltage to the +/- conductors. I liked these because of the small footprint but now will being buying a more traditional smoke detector style base for more money.