paula

Hi all, I have recently bought MAZDA S3 (2006) with already installed ZHUHAI WITSON car DVD player which comes with GPS and rear camera. When im listening to the radio and put reverse gear the camera doesnt display on the screen. It basically displays only if I click on AUX on the player's pannel. Does or did anyone have this kind of problem? It makes me upset as it is time consuming and not the way it should work. What shall I do for the rear camera to work when I put reverse gear no matter whether the radio or Nav or anything else apart from AUX is on? I want the rear camera to be switched on automatically every time I reverse.