Sorry I don't have a picture right now. But this has had me wondering and I can't find anything online about it. In my college in all the bathrooms and laundry rooms I see these sensors in the ceiling which is just a 6" metal rod hanging. There are your regular smoke detectors and everything on the ceiling and then there are these things and I don't know what in the world they do. It just looks like your regular smoke detector frame with nothing but a metal rod hanging down.