FCC rule requires all new TVs to be digital

Americans who don't know the difference between high-definition television and digital television are about to learn, thanks to a federal mandate that kicks in this week.

Starting Thursday, all new television sets designed to receive over-the-air signals must contain a tuner capable of receiving digital broadcasts, not just the old-style analog signals that we have relied on for the past half-century.

Many companies will offer dual-mode sets, capable of handling either analog or digital signals. But in 2009, all US television broadcasts will be exclusively digital, by order of the Federal Communications Commission. This year's digital television mandate is designed to help the public make a painless transition from the old technology to the new.

"For many people, this has already happened, and they didn't realize it," said Megan Pollock, spokeswoman for the Consumer Electronics Association in Washington. Digital tuners are already mandatory in television sets with screens larger than 25 inches.

The March 1 mandate covers smaller sets, the last bastion of all-analog technology. Besides, most Americans have cable or satellite television service. Those video providers handle the digital signal through the adapter boxes they provide to customers.

Those who still watch analog broadcasts have nothing to fear. Even when the television networks go all digital in 2009, companies will offer adapter boxes that will convert the digital signal into analog form, suitable for the older technology.

Getting a digital television doesn't necessarily mean buying a high-definition set (HDTV). Digital broadcasting refers to the use of a stream of zeroes and ones to send the signal, instead of the wavelike signal of an analog transmitter.

All forms of broadcasting use limited amounts of bandwidth on the radio spectrum. Digital broadcasting uses much less bandwidth, while delivering excellent sound and picture quality. Switching to digital will free up capacity that can be used for additional channels or other communications traffic.

Digital broadcasting is different from HDTV, a technology that increases the sharpness of the video signal. Today's standard television systems display a picture made up of 480 lines drawn on the screen. But this standard image can be delivered by either analog or digital systems. Indeed, many digital sets offer a picture that's no sharper than an analog image.

All HDTV sets use digital technology, but they also use an imaging technique that produces a sharper picture, made up of either 720 or 1080 lines. The extra lines mean that the picture can show much finer detail than a standard television image.

There's even a third type of digital set, the enhanced-definition television, which offers an intermediate level of picture quality, better than standard television, but not as sharp, or as expensive, as HDTV.

According to the FCC, it took 12 years for 10 percent of US households to get color television sets. But since the first digital televisions became available nine years ago, 32 percent of American homes have adopted them. That is largely due to surging demand for HDTV programming, because 80 percent of the digital sets deliver a high-definition picture.

But beginning Thursday, even television buyers with no interest in HDTV will find themselves going digital.

Hiawatha Bray can be reached at bray@globe.com.