Over the last few weeks I’ve been reviewing Apple TV, a device that delivers content from your PC or Mac to your TV, expanding the “two foot interface” (sitting in front of your computer screen) to the “ten foot interface” (sitting on your couch or favorite easy chair in front of your TV). Apple TV only works with TVs that are equipped with either HDMI or component video connections.

This week I realized that I have given short shrift to discussing the “pins and plugs” (nuts and bolts) of the different TV connection options. So, this week we’re going to rectify the situation with as non-geeky an approach as I can muster. Wish me luck.

Let’s go chronologically from “back then” to now, and start with something we’re all familiar with – the venerable three-headed “RCA jacks”. Back in the day, we used them to connect our VCRs to our TVs and other VCRs. A red and a white plug carried left and right analog audio, and a yellow plug carried “composite” video. Composite video carries color, brightness, and timing information in a single signal. This is sufficient for analog video signals like VCRs and older camcorders.

The advent of DVDs and digital video camcorders required more “discrete” connections. Along came S-video, which separates the video signal into a black-and-white (contrast) and a color component, delivering a clearer image with crisper colors. You’ll find S-video jacks on older DVD players, video games like the first-generation Xbox, digital camcorders, and notebook computers.

When higher resolution TVs and DVD players (especially those with progressive scan, which presents a better picture) came along, so did component video. Component video delivers the video signal as discrete red, green, and blue color components (hence the name), together with other information that the TV set uses to create a sharp, vibrant picture. Component video is still “analog” video, although it can be used on newer standard definition TVs and provides a very nice picture on high-definition (HD) TVs.

As TVs and cable and satellite companies go digital, however, a digital connection is required. Enter the HDMI (High Definition Multimedia Interface) connector. HDMI is capable of delivering a digital signal up to 1080p (the highest currently offered on HDTVs) and up to 8 channels of digital audio. Note that HDMI is the only connection we’ve talked about that delivers both audio and video via the same jack.

Another, less widespread digital connection is DVI (Digital Video Interface). Many computers have a DVI port to allow connecting the computer to a TV or high-resolution computer monitor. DVI also separates the video signal into red, green, and blue color components and produces a very high-quality picture.

But (and this is a big but) without a good quality signal to transmit, even the most sophisticated and powerful connections will produce mediocre results. Want to see this in action for yourself?

Go to any electronics superstore. You’ll find rows of HDTVs, all presenting dazzling images of Hawaiian beaches and football games played by teams you’ve never heard of. These gorgeous images are all coming from a digital high-definition signal delivered via satellite to the superstore. Ask one of the salespersons to show you a “normal” local cable channel. Reluctantly, they’ll switch over to good old cable TV.

Ugh. It’s not a pretty picture. There’s just not enough information coming through the analog (or even digital) cable signal to produce a really good picture on an HDTV. In our area, only a handful of HD channels are available, although more are on the way.