When I first hooked up the sensor to the opener, the opener behaved not at all like it was supposed to. After some consternation I finally figured out that the receiver must not be set in the NO configuration, which was called for in the owners manual. After looking at the circuit board in the receiver with a magnifier, I discovered a tiny wire jumper which was in the NC position. It was after I moved that jumper to the NO position that the opener behaved properly. Nothing in the manual mentioned anything about the existence of this jumper, where to look for it, and what to do with it.