Thanks very much!
Now I just need to figure out the best way to make the connection to that wire, or hope my installer knows.
I saw Fezzik's posts about using a wire from a computer's power supply. I swapped out a power supply on a desktop unit a couple of years ago, and thought I had kept the bad one somewhere, but a preliminary search at 3:00 AM did not turn it up. It may be one of the few things I actually threw away, now that I could use it!
Edit: Would the connector on the right in the photo below be what I'm looking for?
View attachment 97742