The fix for me was in the wiring. When the camera body was screwed onto the wall tightly, it apparently crimped the wiring in such a way the NuTone KB-10 chime would have a constant hum or buzz and would not work. When I loosened the screws a bit, the hum went away and it worked. The problem as I see it is there is no room for the wiring between the back of the ring unit and the wall. I got frustrated with the lack of information that would help me. I called customer service and he had me switch the wiring at the terminals on the back of the camera body and, viola!, it worked. Thinking that made a difference, I thanked the rep, said goodbye, and screwed the body back on the wall...tight. The hum returned and the chime would not work. Then I decided to loosen the unit off the wall just a hair. The chime worked and hum went away. I sort of stumbled on this solution, but that's how I realized what my problem was. As I write this, the best solution will be to cut a hole big enough in the wall where you can fit all the wiring and connectors (if used), back into the wall so there will be no crimping. I hope this is clear and helpful for the next customer having similar issues.
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