muting head unit audio when carPC outputs audio
I'm thinking that my install is going to be a cd head unit and a separate carPC.
Alpine's H701 processor has a really neat input for 'mixing' nav audio with music. Much like a cell mute. But I'd have to go alpine and it's $$$$$
How could I accomplish this with other head units? Most head units I see have the ability to mute themselves for a cell phone. If I went with a separate sepeaker for the carPC, what could I do to mute the main stereo?
Are there any devices that can detect audio on a cabe and trigger a separate signal to mute a stereo?
Also, what if I want to use the CarPC for mp3 also (or just went with a carPC only)? Does it already today mute the mp3 or xm audio when nav speaks?