OK. I understand that photos/diagrams/specs of your 3-wire signal may not be practical for you to post.
I'm still looking for more information about the signal itself. Previously I asked about your experiment. It's re-stated below with the wire colors BLK, RED, GRN for your mystery signal.
You say you hooked up a 9V (DC) battery to the 3-wire signal and nothing lit up. The battery of course has a + and - terminal and should even be labeled as such. So for the 9V test are you saying no light for:
a) BLK to -, RED to +
b) BLK to -, GRN to +
c) BLK to +, RED to -
d) BLK to +, GRN to -
But then you did get light for 12V AC:
a) BLK to common, RED to AC hot
b) BLK to common, GRN to AC hot
