JUST BECAUSE YOU HAVE a digital-ready TV doesn’t mean you can watch HDTV. You need a digital tuner.

HDTV over cable currently comes in a few different forms. In some cases, the cable company may retransmit the terrestrial (off-air) broadcast signal. A terrestrial tuner with Cable-8VSB capability will tune these channels, which are at different frequencies than some off-air channels. This is temporary, and eventually those cable companies must change to a system called QAM. Some cable companies are already using QAM, and of those, some are scrambling only their premium channels. Their customers can connect an integrated HDTV with QAM tuning capability directly to the cable, without a cable box, and receive the unscrambled channels. The cable companies likely require an HDTV cable box, which may also have a corresponding fee, to view premium and pay-per-view channels. You’ll have to call your local cable company to find out. Future "digital cable-ready" displays will connect directly to the cable line, without a cable box, for all high-definition channels, premium or otherwise. These displays will include a slot for a security access smart-card, called CableCARD, provided by the local cable company. Only a couple of companies are offering such a TV. Cable companies are expected to have their systems in place sometime this year.

Once you’ve figured out what tuning functions you’ll need, you’ll want to pay attention to what connections are available. For example, you may need two antenna inputs if you want to use both a rooftop antenna and cable signals. Multiple audio and video outputs provide more flexibility when connecting the tuner to your audiovisual system. You’ll definite ly need a digital audio output to con nect the HDTV signal’s 5.1-channel Dolby Digital audio soundtrack to your surround-sound processor. There are two types of digital audio connectors. The type you need depends on the type of inputs on your surround processor. The 5.1 analog Dolby Digital outputs available on some tuners might be useful if you have an older Dolby Digital–ready surround processor.