I'm building a portable Atari, and I'm building in some AV jacks. Since I'm using a nice, large, led-modded PSOne screen, I want to not only have AV out, but also AV in (in case that ever comes in handy, and also it would be a shame to limit a 5" screen to just Atari graphics). Naturally, I'll need a switch to change between the two. This is where I'm running into my mental block - how do I set the switch up so that when I have AV out, my PSOne screen is turned off (to conserve power)? Here's the setup I've thought of so far, which is simple enough but the screen stays on when I have it set to AV out.
Here's a quick drawing I made - I hope it gets my point across. How can I improve on this to get what I want?


