The digital-TV transition can still seem a fuzzy, far-off thing, even though it's now been almost seven years since the first customer took home a high-definition digital set.

Today, most sets sold still receive only analog broadcasts, missing out on the visual and sonic excellence of high-def TV. The plasma and LCD HDTVs that dominate high-end electronics stores are sometimes scarce at mass-market retailers -- at the Target store in Seven Corners on Thursday night, a measly one HD set was on display.

But if you're buying a TV set, it's now time to think about getting a digital model.

One reason is the steady march of TV technology, which has driven prices of tube-based digital sets to below $500. HDTVs are becoming more of a commodity, so you're no longer in serious danger of buying a set and finding that next year's model works radically better.

Another reason is the increasing quantity and availability of HD programming via cable, satellite or free, over-the-air broadcasts. (Digital TV can be provided in lower-quality forms than HD, but those lesser formats are little used, making "HD" essentially synonymous with "digital.")

But the biggest reason to think digital is that analog television's days are numbered. Those signals almost certainly will vanish from the airwaves by the end of the decade, and possibly a lot sooner.

The rush to ax analog comes because digital and analog broadcasts use different frequencies, and the government won't let TV stations keep both. It plans to auction some analog frequencies to other telecom users -- thus covering a tiny bit of the ballooning federal debt -- and hand others over for use by police, firefighters and paramedics. Congress originally placed a conditional Dec. 31, 2006, deadline that no one in the industry thinks will happen, but is now looking at ways to set a later, unconditional deadline.

If TV sets had the life spans of computers, that wouldn't be a problem. But people routinely keep TV sets for a decade or more. An analog set bought today will easily spend more than half its life needing to be hooked up to a converter box to receive any over-the-air broadcasts.

It will still work with cable or satellite boxes as before -- but as high-definition content inevitably becomes a standard feature instead of a premium add-on, you'll wind up paying for things you cannot watch.

A digital TV will cost more now, but it should be a better value over time. Unfortunately, picking out a digital set still requires detective work. Four important factors are either well-hidden or absent entirely in ads and retail presentations.

* Does the set include a digital tuner?

Every analog set includes an analog tuner, but many digital sets omit a digital or "ATSC tuner (after the Advanced Television Systems Committee that wrote the digital-TV standard).

These sets are generally called "HD-Ready," even though they're not ready to display any HD content without extra hardware. A set with a digital ATSC tuner usually carries a label with "HD Built-In" or "Integrated HDTV." But even then, retailers can blur the lines by forgetting what these labels mean. At last week, for example, "HD-Ready" described sets both with and without digital tuners.

You could always decide that you'll only plug the TV into a cable or satellite box and not worry about over-the-air reception at all. But what if the TV gets demoted to second-set status? Many of those are not connected to cable or satellite.

That makes it especially bizarre that digital tuners are so hard to find in sets smaller than 26 inches -- the category most likely to be used as second or third screens in a house.

* How much electricity will it use?

The Natural Resources Defense Council tested the power consumption of 25 digital and analog sets last year and found that a single set could use as much electricity over a year as 11/2 refrigerators. And while bigger screen sizes generally meant more power consumption, and projection sets used less electricity than plasma and LCD sets of the same size, the study found that sets' energy efficiency was all over the map.

"Plasmas have been singled out as the energy hog, somewhat unfairly," said Noah Horowitz, senior scientist with the council. "The best plasma could use less energy than the worst LCD."

But you will not find wattage figures in most retail displays; you'll need to go manufacturers' Web sites and pull up the fine-print pages listing each set's specifications.

This is not just a matter of having to pay a bigger electricity bill every year. Sets that use more electricity also run hotter, requiring cooling fans to vent that heat -- possibly making their own racket in the process.

* Will it let you record TV shows as you wish?

Two winters ago, the Federal Communications Commission voted to require that sets with digital tuners include circuitry to enforce a complicated copy-control scheme called the broadcast flag. Vendors had until July 1 to include this hardware -- but in early May, the entire flag ruling was tossed out in court, on the grounds that trying to stop the sharing of TV recordings on the Internet was none of the FCC's business.

Only a few manufacturers, such as RCA, had already built in flag circuitry -- but they have been strangely reluctant to advertise this "feature," which would limit your ability to copy TV shows. Should Congress heed the wishes of movie studios and vote to instruct the FCC to reinstate the flag rule, a set that ignored the flag would be more attractive.

Other companies, such as Philips, have sidestepped the copy-control issue by not including any high-definition outputs, leaving you no way to make full-quality recordings of anything you watch over the air.

* How long will the set last?

Because non-tube HD sets rely on relatively new technology, people are understandably nervous about the life span of these sets in the face of such real or potential threats as "burn in," a theoretical issue with plasma sets in which a station's logo or other static elements of the picture get burned into the display.

Manufacturers uniformly say they have licked these problems and have done the tests to prove it -- but often bury these life-span figures (usually, 15 to 20 years of five-hour-a-day viewing) in their marketing materials. Meanwhile, many offer only one-year warranties that don't exactly convey great confidence in the hardware's reliability.

If the electronics industry could clearly communicate how it stands on those issues, shopping for a digital set would be considerably easier, and the entire digital transition could be much less of a mystery.

Living with technology, or trying to? E-mail Rob Pegoraro at