Unless you take steps to prevent it, your TV set will go black about three years from now.

The Senate is expected to vote this week on a bill to force broadcasters to abandon their analog signals and switch to digital by Feb. 17, 2009. That means anybody without a digital TV or digital-converter box will see a blank screen when they flip on their set. The measure was just passed by the House.

It's an unprecedented move by the government. After all, Uncle Sam didn't make us switch from records to CDs or VHS machines to DVD players. Members of Congress say the move is designed to make valuable broadcast signals available to police and firefighters in emergencies.

What's not often said is that much of the signal spectrum will be auctioned off to wireless and broadband companies that want to provide ever fancier phone and Internet services. That auction is expected to bring $10 billion or more to the U.S. Treasury.

To soften the blow for consumers, the House bill provides vouchers that can be used to purchase digital-converter boxes for old TV sets. Some consumer groups have complained, however, that the vouchers will be available only on a first-come, first-served basis, and will be worth just $40, while converter boxes are expected to cost $60 or more.

If you are a cable or satellite subscriber, your company will lead you through the process.

Time to Go Digital?

And what if you're considering buying a new TV for Christmas or in time for the Super Bowl? Should you go digital? Or wait a couple of years for prices to drop? Well, it depends. If you're not a huge TV viewer and you're on a budget, it might be best to buy an inexpensive analog set and then use a converter when the time comes. The converter will not turn your analog TV into a digital TV or improve your picture quality, but at least you'll be able to get programming.

If, on the other hand, you're a television and DVD enthusiast, you might want to spring for a digital set. Not all digital TV is high-definition. There are actually three quality levels: standard, enhanced and high. High-def is the most widely available, and the good news, experts say, is that the HDTVs sold today are not likely to become obsolete any time soon. And if you're planning to get a big-screen TV, then a high-definition model won't cost you much more.

There is a downside, however. Most television programs are not yet broadcast in high-def ("Good Morning America" on ABC is one exception!), so at first your set will be best for viewing DVDs.

Furthermore, many HDTVs do not actually contain the high-def tuner needed to bring in broadcast programming, which can cost an additional $750 or so. And how do the trendy plasma and LCD flat screens fit into the picture? Most of them are powerful enough to accept an HDTV signal, but only a few display all the resolution of true high-definition TV.

Shopping for a new television these days is like learning a new language -- one made up entirely of acronyms! HDTV. LCD. ATSC. DLP. And on and on. But ask questions until you get it right. After all, the average television set lasts for many, many years.