OK. This will be what you are speaking of, and if I remember right, it was a topic of discussion on one of the forum a couple of years or so ago. Sadly, CRS prevents me from remembering exactly what it does. Hopefully, someone else can help you. We've got one on our 2010, hence these pictures, but I suspect it is for something I never use. Our unit is now 5 years old and I've never changed the batteries.
We've got an appointment in a couple of hours, so if you don't have an answer by this evening, I'll try to look through all my owner's manuals for the coach and its components and see if I can find out for you.
Terry