Two years from now, analog TVs will be outmoded, not just outdated. Analog TVs will no longer receive a signal without help from some additional hardware when the switch to digital is complete.

With the steady march toward big-screen HDTVs chronicled so often on these pages, it's easy to lose sight of the fact that more than 20 million Americans still rely on a free over-the-air signal for television. When that signal is forever reserved for the government's use for national safety and communication purposes, consumers who are unable to afford a newer, bigger, digital TV could get lost in the changeover.

To help those who don't have room for a digital TV in their budgets, the U.S. Department of Commerce has announced a coupon program to help families afford the converter boxes needed for an analog TV to accept a digital signal. Check out the San Francisco Chronicle's story on the coupon program, but here's a look at a few analog-to-digital facts about why this switchover is happening and how people who cannot buy new TVs will be able to watch their analog TVs.

• Congress has set the February 19, 2009 deadline to free the nation's airwaves to be used primarily for communication between emergency workers in case of major disasters. The deadline was recast from an earlier 2006 deadline because the government's prediction of the number of Americans who would be watching digital TVs by now was way off. Despite the drop in prices, they are still out of reach for many.

• The commerce department's National Telecommunications and Information Administration (NTIA) will set aside $990 million to help pay for digital-to-analog converter boxes. The boxes are estimated to cost between $50 and $75 each, and the coupons are expected to be $40. Consumers in each home in need of the hardware can request up to two vouchers, with proof that they do not have cable or satellite service.

• The NTIA is working with broadcasters, consumer electronics retailers, manufacturers, and consumer groups to spread the word about the coupon program. The specific details of the coupon program will be announced in early 2007.

For more facts about the switch to digital TV, check out this Federal Communications Commission page. And here are a few how-to articles if you're thinking of buying a digital TV:

Budgeting for HDTV
Understanding HDTV Options