By Manav Tanneeru
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(CNN) -- An era in American broadcasting history will come to an end before the decade is out.
Early in 2009 all over-the-air TV stations must switch the way they transmit their programming, bringing a number of changes not only to broadcasters and viewers, but to emergency responders and digital innovators as well.
Since the advent of television, stations have sent their programming via analog signals. As a result of legislation passed by Congress in 2005, they will have to convert their transmission to digital signals by February 17, 2009.
Broadcast signals travel over the electromagnetic spectrum, which carries all sorts of transmissions, including AM and FM radio, shortwave radio, radar and television, explained Duke University professor Stuart Benjamin.
Analog TV signals occupy a big chunk of the spectrum. Digital television, which also is broadcast through the air, occupies about 25 percent less space on the spectrum than analog -- and offers more services.
"The digital signal is more concise," said Megan Pollack, a spokeswoman for the Consumer Electronics Association. "It's a crisp signal and also has the ability to be high-definition with surround-sound encoded into it. It has the ability to be smarter, so it has more functions."
With the switch to digital, the space freed up by the unused analog signals will be returned to the federal government and auctioned off to new providers and services, according to Brian Dietz, a spokesman for the National Cable and Telecommunications Association.
The analog space -- owned by the federal government and leased to TV stations through license fees -- is considered the "beachfront property" of the spectrum worth several billion dollars, Benjamin said.
For viewers, the change will mean different things depending on the type of TV set they have and how they get their signal.
Sets that only pick up an analog signal over the air will need a set-top box to convert the new digital signal to analog. The legislation that mandates the digital conversion includes subsidies toward helping consumers buy the converter boxes.
But even with the box, analog TV sets won't display the better picture and clearer sound that digital television (DTV) offers. For that, viewers will need a DTV set or a DTV receiver and digital display monitor. By next March, all TVs and other equipment that receives broadcast TV signals must have digital tuners, according to the Federal Communications Commission.
Many TVs in stores and some already in homes are equipped to receive a digital signal. Some even receive high-definition television (HDTV) -- a type of digital TV service that offers super-sharp pictures and sound in a widescreen format.
Viewers with cable TV also may need extra DTV equipment to view the new digital format, and those with a satellite dish may need special equipment to view HDTV programs, according to the FCC, which advises subscribers to contact their providers for more details.
"We've talked to a lot of these consumers and we asked what they were going to do when this happens. A lot of people said, 'Gosh, I have a 20-year-old TV, I'm going to buy a new one," Pollack said.
Why so long?
Competition between the broadcast and cable industries has delayed the transition to digital, according to Benjamin, co-author of "Telecommunications Law and Policy."
Digital TV has opened the door to crisper signals, surround sound and high-definition pictures.
Digital signals will enable local stations to "multicast," or broadcast multiple programs on one signal. A local station could have a 24-hour news or weather channel and a channel dedicated to high school football all broadcast over one signal.
Multicasting is already available in many markets and will become more pervasive over the next few years. More than 1,500 of the some 1,750 stations across the country have already completed the digital transition.
Of those 1,500, roughly 800 are delivering additional programming through multicasting, according to Kris Jones, a spokesman for the National Association of Broadcasters (NAB).
"The question then becomes, are the cable companies going to carry this programming," Jones said.
Broadcasters want the additional programming because it provides more possibilities for advertising revenue. The cable industry, however, is reluctant to carry the additional programming because it could, in some cases, directly compete with cable channels.
The transition to digital has been expensive for broadcasters.
"It's a massive investment for local broadcasters with no assurance they'll get a return," said NAB senior vice president Dennis Wharton.
He estimated the costs at about $2 million per station for an upgrade to digital television and about $10 million per station for high-definition television.
New services and providers
The shift in how the spectrum will be allocated also will bring significant changes to other industries.
A chunk of the spectrum space that will be vacated with the changeover will go to first responders, allowing for better communications in the event of emergencies.
The spectrum space used for public safety is sometimes congested, hurting the ability of various emergency services to communicate with each other.
With new spectrum space dedicated to public safety, communications are expected to improve, and innovative methods to respond to emergencies -- like sending building blueprints to firefighters responding to a blaze -- may be possible, said Robert Roddy, a spokesman for the New York state Office for Technology.
Other spectrum space will be auctioned off to new providers or services and could lead to more innovations in the wireless and broadband industries. Some examples include better video downloads for cell phones, broadband televisions with more on-demand options, and more services for handheld devices.
"The entities that are going to benefit the most may not even exist yet. ... [They] are going to get access to that spectrum in two or three years and come up with some wholly new service," Benjamin said.
"For all I know, the next time you and I have a conversation in four years, we'll be doing it through some new-fangled device where we are able to sort of simultaneously type, look at each other, and interact in all sorts of ways."
Many TVs in stores are equipped to receive a digital signal.