High-definition digital television provides movie-like picture quality and CD-like sound quality. The Federal Communications Commission has mandated that everyone in the United States must have access to digital television by 2002 and that analog broadcasting must be phased out by 2006 under certain conditions. Limited digital programming has been introduced. Television sets designed to handle digital transmission started to appear in August 1998, and an estimated 66,000 have been sold so far.

-- Richard Drezen

In a television studio, the digital equipment records images much like ordinary cameras. In the digital version, however, the information for pictures and sound is digitized -- or reduced to a string of bits consisting of 0s and 1s, representing both pictures and sound. A data master is created using a computer server instead of traditional videotape. This information is then compressed, or "encoded." To understand this better, imagine one computer user wanting to send a very large data file to another. As the size of the file is large and unwieldy, the sender shrinks, or "zips," the data, thereby making it easier to send from one computer to another.

The digital broadcast signal is then sent via antenna towers that ar equipped with digital transmitters. Consumers receive the signal just as before, by home antenna or cable system.

When received at home, the digital signal is decoded -- or, to follow the earlier analogy, "unzipped" -- by a separate decoder box next to the television for an older model, or a built-in digital decoding device.

The television functions much like an analog one, with images appearing on the television screen and sound being channeled through the speakers.

The "aspect ratio," or the ratio of width to height, for a standard television image is 4-by-3. HDTV offers a 16-by-9 ratio, meaning the image is a third wider than standard TV, and with the proportions of a movie screen. Because there are more pixels per screen, the images appear crisper, offering more detail in close-ups. Sports and live-action programming will benefit by the more panoramic aspect of the screen view.

Because it is digitized, more information can be transmitted -- video, audio and data -- allowing for some degree of interactivity and the viewing of multiple frames. For example, in theory, a viewer could be watching a sports event and request statistics on a player without interrupting the flow of the sports coverage.

SOURCES: Sony Electronics Inc.; Consumer Electronics Manufacturers Association; "DTV for Dummies" by Elaine Outler, Ron Baker and Tracy Barr (IDG Books, 1998)