Until now, millions of TV viewers who use reliable rooftop antennas and rabbit ears to get their signal have not been affected by the nation's transition to digital TV.

That's about to change.

By Feb. 18, 2009, the signals the sets receive will be shut off. Those old analog channels, which have been used for 60 years, will be reclaimed by the government and auctioned for billions of dollars to other communications services. The nation's broadcasters will transmit only digital signals.

And older TV sets will stop working — unless hooked up to cable or satellite systems or an add-on digital tuner.

So far, the focus on the digital TV rollout has been the spread of high definition. About 30 percent of U.S. homes have digital HDTV sets, which receive the new channels. But nearly 20 percent, or more than 20 million homes, rely strictly on antennas to receive free over-the-air broadcasts. The National Association of Broadcasters says another 14.7 million have at least one antenna-powered TV.

Legislators, broadcasters, manufacturers and consumer groups have known about this dilemma for more than a decade. But as the turn-off date approaches, all are concerned about confusion and a lack of awareness; the NAB estimates more than 60 percent don't know about the transition.

"This scares me politically. There is no anger that comes close to the anger of an American that cannot get television," Sen. Claire McCaskill, D-Mo., said at a hearing last month.

Viewers may be adding to the problem by buying new sets that still aren't equipped for digital signals. "There are risks that consumers are not going to have the information to make the decision that best fits their own viewing and economic needs," says Consumers Union's Jeannine Kenney.

As of March, manufacturers must make new TVs digital-ready, even small, inexpensive sets. But old inventory remains. Retailers such as Best Buy and Wal-Mart have begun marking sets with consumer warning stickers and posting signs.

Very few are still on shelves, says Wal-Mart spokesman Melissa O'Brien, but the chain has "been preparing for customer education on the big switch."

The government is offering discount coupons for purchases of add-on digital tuner boxes. And this fall, the NAB launches a road show to hit 200 cities over 18 months. By December, stations expect to start running public service announcements.

Groups such as the Leadership Council on Civil Rights and National Hispanic Media Coalition are worried that the poor and elderly are in danger of being left out. "They may not be going to buy new TVs because they are living on fixed incomes. Affordability, whether you are talking about upgrading to cable or getting converter boxes, is an issue," says David Certner of the American Association of Retired Persons. "We don't want millions of people with TV sets that don't work and don't know what to do."

IS YOUR TELEVISION READY TO GO DIGITAL?

Two years ago, the government set an end date for the USA's transition to an all-digital television system: Broadcasters must have switched off their old signals by Feb. 18, 2009. Most TV viewers are blissfully unaware of that.

If they're cable or satellite subscribers, they needn't be concerned. But as many as 21 million households depend on analog sets and antennas. When local broadcasters throw the switch, those TVs will go dark.

Questions and answers:

Q. Which televisions will not work?

A. Older TV sets — and not necessarily all that much older — will be unable to display free over-the-air programming unless they're connected to a new type of set-top box, the digital-to-analog converter. By government mandate, all TV sets 35 inches and larger manufactured since July 2005 have built-in digital TV tuners; sets 25 inches or larger have included them since March 2006. Since last March, all television sets, even as small as 5 inches and as inexpensive as $200 or less, have been made with DTV tuners built in.

Q. Does that mean all new TVs being sold have built-in digital tuners?

A. No. Some retailers still have analog sets on shelves and in inventory. But stores have been required to post notices about TVs that will not be compliant with the 2009 DTV mandate.

Q. If I'm shopping for a new TV, how can I make sure I buy one that will receive digital TV signals?

A. Here's the terminology you're looking for: Digital TV (less-expensive sets may say Standard Definition Digital TV) and an ATSC (Advanced Television Systems Committee) tuner.

Q. Will I need a new antenna?

A. Probably not. Most rooftop antennas will pick up DTV signals. Viewers using rabbit ears may or may not still be able to. (More information at www.antennaweb.org.)

Q. How do I get a digital-to-analog converter?

A. Set-top boxes are expected to begin appearing in stores in January. The government has set aside more than $1.5 billion to subsidize the purchase of more than 20 million converter boxes. Starting Jan. 1, all consumers — even those who have digital TVs in addition to older analog sets — can apply for up to two of the $40 coupons that can be used toward purchase price. (For more information, call 888388-2009 or go to www.dtv.gov.)

Q. How much will they cost?

A. The boxes, which will include closed-captioning and V-chip features, are expected to go for $50 to $70.

— USA Today