the setup on mine is:
wall to cable box to VCR to TV hooked up with regular rf cable, then the DVD hooks to the VCR using the RCA cables (red, white, yellow).
When I want to watch DVD, I turn on the DVD and the VCR. Turn the VCR channel to LINE 2 (where I plugged it in) and watch the DVD thru the VCR to the TV.
I'm in the process of adding another layer to this whole setup by adding a PVR/DVR/Tivo unit that I'm building to the combo. We'll see how that works.