Pixhawk and RunCam TX200U

Hi all,

I recently hooked up my RunCam 2 as an FPV, but I can’t understand where on the Pixhawk the green wire should go that’s on this diagram. It’s supposed to control power to the camera. I have a 2.6.8 and can’t identify the ‘TX4’ pin…

Should I set up telemetry before I do this, or can I just connect this to the flight controller and then associate a switch on the remote control to it?