Say I want the audio of an external source (radar detector, etc) to mute the audio of the AVIC (unless it is connected to my BT phone) - is there a simple way to do this?

I know that the AVIC has the multiple a/v inputs and a mute wire, what I don't know is how I could force it to that input anytime it is needed (without having to nav through the menu and change the input).

Just realized that I could do this with the reverse camera input since I will not have a reverse camera, but does it have audio?