I have the 27" Samsung HDTV, and I'm confused by a port on the back. The TV input menu says I have 2 AV inputs and 2 AV/S-Video inputs. I see both the S-Video combo ones, but I see three normal AV ones. The top one doesn't seem to work. I'll plug a source into it and it won't recognize it. I'll then plug the same source into one of the other normal AV ports and it will work fine. So I can come to the conclusion that this isn't the one in the menu. What is this blank port? What purpose does it serve?