back up camera power from dual sources

Greetings! I have installed a back up camera on my truck and am able to successfully view the video image on my JVC KW-NSX600 head unit. The camera is currently powered by a nearby reverse light on my bumper. Naturally, when I go into reverse, the head unit changes its display to reflect the video image. Works great, no problem there. However, I would also like to use it while in Drive by selecting the "Camera" button on the head unit. This will allow me to monitor trailer/hitch condition while in Drive. The radio (with Axxess GMOS-LAN-01 Factory Integration Adapter) does not have a specific camera power output that is activated when pushing the camera button on the screen. It is simply looking for an video input when the button is pressed. I would like for the camera to be optionally powered on when: 1. The reverse lights are on (or reverse signal is present at the radio input). AND 2. Selectively powered (via dash mounted switch) when in Drive. I am grateful for this forum and am hopeful that someone has a diagram already created for this configuration. I would prefer a diagram as opposed to a written explanation. Thanks! Robert aka Highside Hawkins, TX.Highside

The vehicle is a 2008 Chevrolet Silverado HD 2500 LTHighside

An easy way that is independent of the HU button is another +12V switch via a diode to the reverse camera but you need to insert a 2nd diode in the existing camera's +12V feed to stop power feedback (turning the reverse lights on with the switch etc. The diodes can be any 1N400x - typically 1N4004 oe 1N4007 - with their line-ends towards the camera's +12V input. If the camare can't handle the diode voltage drop of ~0.7V, a relay can be added later.

Thanks for your response, oldspark. Please see if my drawing represents a workable plan... Highside

Yep - that looks good noting that only a lit switch requires the CHASSIS / GROUND connection, and the "TO FUSE PANEL" might mean 'from reverse switch' or switched Rev +12V etc.

Thank you, oldspark!Highside