some guy

I just built my father a system that is almost identical to the one I own. All components are sony and the receiver (str-de975) features video switching. My system works fine but I cant get my dads worked out. The DVD player is hooked up with s video and digital coax but all other components (cable box, vcr) are hooked up with RCA cables. The problem is that the receiver uses a different buss for analog and digital signals and It will not switch between them. As a result i need to leave the S video disconnected from the tv in order to watch an analog source and reconnect it to watch DVD. I know that this system can work because mine does but I cant figure out how to get this setup correctly. I think the wiring is correct and I need to tell either the receiver or the television to allow video switching.