I'm trying to hook a comcast cable box to a dvdplayer to a Samsung lcd. I've gone from the wall to the box to the TV with the cable. I'm taken the hdmi cable from the box to the TV. The TV works, but there is no picture on the dvd when I try to play a disc. Help.

There must be some differences between different models of DVD players, since none of the three I have experience with have ANY connection for another signal source (Cable converter, satellite receiver, VCR, game console or anything). The only signal connections were stereo (left and right), composite video, component video and s-video - all outputs. Fortunately my home theater amplifier/receiver has some composite video switching capabilities (my TV only has NTSC RF and composite inputs).

With DVD players like that you would need to use the multiple inputs on the TV (if so equipped) or purchase a switching unit to install between the TV and the multiple signal sources (DVD player, cable converter and any other devices like a VCR or game console). The switching units might be available from TV and video game retailers.

Of course combo DVD/VCR units will have inputs to allow them to time shift material from cable converters and satellite receivers. DVD recorders and Digital video recorders would have inputs too. These units should have some way to select the video source, probably with the remote control. Some manufacturers make user manuals available for download from their web site in case you have lost the printed manual that came with the unit. Some material might be restricted to standard definition recording.

Told me I need a switching device