Ok, I've been enlisted to spearhead the addition of a TivoHD into a friend's home theater system. Normally, this would be a relatively straightforward endeavor, but I'm not sure I can adequately express how incredibly complicated their system is. Suffice it to say, it has a whole room behind the floor-to-ceiling racks, the front of which are black paneled with the occasional blinking red lights. The brand name stamped on the back of most of the components is something called "B&K". There is also an Elan system that is its own offshoot, handling remote LCD screens throughout the house and random things like the doorbell. I don't understand how to program the thing, but for the most part I'm good with the inputs and how it passes signals to the various things that need to be switched/turned on/modulated. There were some weird shorts in the system, but I've mostly gotten that figured out, and there was also a really weak signal to the Comcast HD box, but I got that taken care of thanks to an amplified splitter (Thanks AbMagFab.) So. When you sit down in front of the TV you have a touchscreen panel in your hand. You choose among various things to do "DVD, Tivo, HDTV," etc. When you choose one, the system turns on the component, switches the input to the television, and presents you with a touchscreen keypad that has the buttons relevant to the task. IR blasters handle the various functions. The system has a setting for HDTV, which was supposedly taking the signal from one of the Comcast Digital Cable boxes, and passing it along to the main TV, which is a Mitsubishi VS80803. It's an older (1999) 80" 4:3 1080i rear projection television. (There are also six TVs that flank each side of the main television--they are fed by a straight analog signal that's handled through other functions on the system.) Clear as mud? I figured that the easiest thing to do was to take the Comcast Digital cable box that's supplying the HDTV to the television, and literally swap it out, one-for-one, for the HDtivo. That way NONE of the cables would change. The main B&K receiver would still be receiving a digital signal over component (red/blue/green) cables, and also an optical digital audio signal. Presto. It shows a video signal. The touchscreen for this particular function (HDTV) doesn't work anymore because of course it's trying to change channels on what it thinks is a Comcast Digital Cable box but is now a tivo. I can have that changed later by someone who has the laptop interface and programs that handle the Elan touchscreen the IR blasters. But then I saw the tivo was sending out a 480i picture. No problem, I'd need to change it to 1080, right? Well, when I do, the video picture is garbled. In fact, it's garbled on anything BUT 480. Which begs the question--why was it showing HD content when the Comcast box was attached, but now that the tivo is there, it can only show 480? Something was NOT right. I start pushing the "input" button on the TV to scroll through what inputs it was getting, and an input called "DVD Component" is what is getting the signal from the tivo. I get one called "High Definition 1080" input, and it's a black screen. My hunch was: the TV hadn't EVER been showing HD content. Sure, it was getting a signal from an HDTV Comcast box, but it seemed like somethign was wrong. The picture was never all that high definition. It was better than the other input function (tivo, via a series2) but that was coming in over composite, and this was component. I pulled out the tv, which was built into a wall (thank goodness it's on wheels--I'm only a 125 pound woman!) and I see the following: Various jacks for different inputs, mostly composite, with a dedicated component input labeled DVD. There's a separate box around some OTHER jacks, with the heading "High Definition Input." There's nothing attached there. Nada. Zilch. Which epxlains why the screen was black when I scrolled to that input on the TV directly. So my question is this: Do HD tvs need to get their HD signal over SPECIFIC input jacks in the back, or should it be able to receive and display HD signals no matter whether you decide to run it into jacks labeled "input 1," "input 3," or "DVD input?" If I need to hook up to these specific jacks, fine, but they are strange looking. Not your standard AV jacks, even if they are labeled Red/Green/Blue. They look like funky coax jacks, and a quick google search leads me to think they are something called "BNC?" Does that make sense to anybody? If that's what they are, can I just get little dongles that will change the end of component cables to BNC? Because the B&K system only has component output that takes the little jack that looks like your standard AV cables, not the weird coax looking one on the back of the TV. Phew. Anybody follow and have some explanations for me? I'm at my wits' end with this system.