Converting an Audio Signal to a Voltage
I'm sure the title sounds a little obtuse, let me try to explain. My head unit supports a connection for a phone kit, phone mode is activated by applyting 12v (or ground, can't remember which) to a cable, this then takes the audio feed and plays it through the left speaker.
Now, what I want to do is take the audio output from my iPaq which I use for GPS and hook it in via this kit so that when it gives me directions it will mute the head unit an play through the speaker. To do so I suspect I need some way of detecting the audio signal and using it to cause some for of switching (a relay?) to activate the phone setup.
Do any of you know if this is viable or how it might be done? My concerns are how fast it would switch and what would happen in dead spots or pauses between words, would it be switching on and off etc.
Any thoughts welcome..!