On our friend's 04 Discovery, the radio switch on the radio must be turned on for the radio to work when the ign switch is on. There is also a radio switch on the dash that will operate the radio when the ign switch is off. The back up camera has a switch on the front of the monitor that allows you to manually set the backup camera on when the ign switch is on. BTW, these switches work the same on our Expedition.
Jim and Lynda, (Sophie, Jake, attack trained killer Shi-Tzus :-))
2003 Fleetwood Expedition 38N 2005 Saturn Vue