Other Source Component Reviews

Most people who have heard anything about digital television think it's just a greatly enhanced version of analog TV—better sound, high-definition pictures, etc. But there's another side to the DTV transition.

Along with better video and audio, DTV broadcasters can now send out electronic program guide (EPG) information, available to the viewer at the touch of a button. It's all part of something called the Program and System Information Protocol (PSIP). The following alphabet soup describes the various parts of PSIP, most of which are optional for stations to include.

Every DTV station has a unique serial number, as it were, called the Transport Stream Identifier. The TSI, along with something called the Terrestrial Virtual Channel Table (TVCT), tells the DTV tuner just who is sending the signal being received.

Much of the digital information your set-top box or integrated TV must sort out from each DTV channel's signal is located in something called the Master Guide Table (MGT). Here you'll find information on the program you're watching, what's been seen and what will be seen up to three hours before and after the current time, what closed-captioning (if any) is present, and whether or not multiple audio tracks are available.

There can also be information on program ratings, surround-sound formats, secondary programs on additional minor channels, and ancillary data. You shouldn't need to set your clock—the System Time Table information will do it for you (if the station transmits it correctly). The ATSC digital television system provides for all of this, and a station that puts it all together has quite an ambitious task ahead of it.

The goal is to provide the viewer with a more useful TV viewing experience. In theory, you could select a DTV channel, depress the Guide key, and see either a condensed or a full-blown EPG for that station, and even other stations. In this sense, the broadcast EPG info is just like cable TV and satellite program guides.

The trick to making products such as the Zenith HDR230 work is to have broadcasters send out detailed PSIP and EPG info. With that in hand, you'll find the DTV interface very similar to watching DirecTV and Dish. Without it—well, you can still find programs by searching through channels, but you'll have to depend on another sort of TV guide to keep you updated on what there is to watch.—PP