Raspberry pi in car, putting into sleep mode or shutdown

[hypes]

Hi,

Please could someone advise me on what components I need to detect the remote lead from my car stereo, to turn the raspberry pi on or off?

I've got the Pi connected to a power brick(seperate battery) this power supply is then connected to the car stereo USB.

So basically when the stereo is turned off, the USB power to the power brick is cut, which leaves the Pi running off the power brick.

What I want to do is detect the stereo turning off (via the REMOTE lead) and then power down or sleep the Pi

What do I need to do to connect the REMOTE lead from the stereo to the Pi? I'm assuming this REMOTE lead produces some voltage when the stereo is on.

Hope that makes sense.

Many thanks!

[FM81]

I'm assuming this REMOTE lead produces some voltage when the stereo is on.

Assume, it's better you let us know which voltage you have in state "activated" and which in state OFF;
otherwise we all will end in "wild speculations" ...

Greetings, FM_81