I don't what the problem I was having with the in-dash radio was but it has nothing to do with the red button.
When the red button is disconnected and I am also disconnected from shore power, I still have power to the coach. It is not isolating the battery from the 12 volt system.
I think it may isolate the battery from the power center charger.
Here's a pic of the button in the closed position:
and disconnected:
Bruce