By Carolyn Shapiro

The Virginian-Pilot

Three months from today, the television broadcast system that most Americans watched growing up will sign off forever.

Through a handful of measures since 1996, Congress has ordered most broadcast stations to phase out their use of conventional analog transmission and switch their signals to digital technology by the end of Feb 17, 2009.

For most TV viewers, the digital transition already has taken place, even if they don't realize it. About 93 percent of broadcast stations - most affiliates of the national networks such as CBS, NBC, ABC, PBS and Fox - are sending their signals digitally today, according to the National Association of Broadcasters.

Cable TV companies have sold digital packages for years, sending programs through digital set-top boxes for subscribers. Other TV service providers, such as satellite companies and Verizon Communications, tout "all-digital" lineups that have severed their customers' connections to the old format.

Still, in more than 9 million households nationwide and an estimated 44,500 in Hampton Roads, the old analog TV picture is the only one some people watch, according to statistics released last month by The Nielsen Co.

When they go to turn on their televisions Wednesday morning Feb. 18, their screens will show dead air.

Unless they get ready. When asked about the reason for the switch to digital TV, Federal Communications Commission and industry officials tout the public benefits. They emphasize that the use of digital technology - which can compress more channels into less spectrum - will free up room on the broadcast airwaves for public- safety uses, particularly communications between police, fire and emergency rescue departments.

New space on the broadcast spectrum also gives telecommunications companies an opportunity to bring more services, such as wireless broadband, to consumers.

And digital signals offer better picture clarity and sound quality.

The digital switch clearly benefits business as well. Wireless companies can use freed-up frequencies to sell additional services to customers. Cable operators can multiply the number of channels in the same bandwidth they needed for a single analog channel, allowing them to offer more program tiers and packages.

"It's about using this national resource more inventively," said Deborah Taylor Tate, an FCC commissioner, during a panel presentation that the National Association of Broadcasters organized a week ago to mark the 100-day countdown to the digital TV transition.

These benefits, though, aren't so much the reasons for the government's digital TV mandate as the results of it. Lawmakers got involved because, as the broadcast industry pushed to upgrade its technology, they saw a need to protect the public interest.

First, they sought to ensure that the change would leave no analog TV owners in the dark. Second, Congress wanted to reclaim the old analog spectrum - and to garner the proceeds from the sale of it - as broadcasters abandoned it for digital channels.

The Telecommunications Act of 1996 set a deadline of Dec. 31, 2006, to complete the transition. The following year, another law added the provision that the final switch to digital couldn't occur until at least 85 percent of viewers in each TV market were able to watch digital programming.

By 2004, federal officials and broadcasters saw that they wouldn't reach that minimum by the end of 2006. New laws in 2005 set Feb. 17, 2009, for the end of analog broadcasting and scheduled an auction of the recaptured spectrum, which took place earlier this year and raised $19 billion for the federal coffers. Analog signals transmit pictures and sound in electronic pulses over continuously changing frequencies on the airwaves.