Digital TV (DTV) is a newer form of technology used for sending television broadcasts to your home.

For viewers, digital TV can offer improved picture and sound, and potentially more programming options. Digital TV can also offer interactive features, such as electronic program guides.

Broadcasters throughout the U.S. are making the transition to digital transmissions. Currently, local stations simultaneously transmit their broadcasts in both the digital and the older analog forms.

Televised information can be sent more efficiently in digital form. Sending TV content digitally will leave more of the broadcast spectrum free for new uses once the transition is complete.

In very basic technical terms, digital broadcasts are encoded streams of zeroes and ones—the same binary language used by computers. The digitized signal is sent over the airwaves to be received by your TV.

(Digital TV broadcasting is sometimes called “digital terrestrial television” (DTT or DTTV). The longer name is used to differentiate digital TV broadcasting from other digitized forms of television, including digital cable or direct broadcast satellite.)

In very basic technical terms, analog signals are transmitted to your TV by continuously varying radio waves.

( Cable television companies also deliver programming to many of their subscribers in analog form, though most also offer digital tiers or are making the transition to all-digital systems.)

The switch to digital TV promises several benefits:

• Viewers should notice improvements in picture and sound quality, particularly in the case of high-definition (HDTV) broadcasts. (To get the full effect, you’ll need a high-definition set, and the broadcaster and, if applicable, cable or satellite provider must provide a high-definition signal.)

• Digital transmissions make more efficient use of the broadcast spectrum, leaving more of the airwaves available for additional channels or interactive data services.

• When analog TV broadcasts end, broadcasters will return those frequencies to the federal government. Some have been pre-allocated to public-safety uses, including communications systems for police and fire departments. The government is likely to auction off much of the rest to wireless companies and others for commercial uses.

Digital SDTV offers resolution comparable to analog TV broadcasts. Yet picture and sound quality are noticeably better because digital transmissions are free of snow, ghosts, or static noises.

HDTV offers significantly improved images in high resolution—comparable to what you experience in a movie theater—along with CD-quality surround sound. Most digital TVs sold in the U.S. are high-def.

While TV stations will be required to convert to digital broadcasts, they need not offer high-definition broadcasts. But most stations deliver some HD programming and are adding much more as time goes on.

HDTV features a wide-screen, “16 X 9″ format—the screen’s area is 16 units wide by 9 units high (a 16:9 aspect ratio). Conventional television displays (including analog TVs) are 4 X 3.

(SDTV and EDTV displays are available in both aspect ratios, with lesser image quality.)

It isn’t enough for your favorite show to be produced in HD. To actually see it in high-def, two more things are needed: First, an HDTV signal must be received from the transmission source—either over the airwaves or via digital cable or satellite service. Second, you will need an HDTV set to watch it on.

HDTV shows can be viewed on other DTV displays, but they will not be in high-def.

An HDTV can also receive standard-definition programs, but they won’t be in high-def, either.

EDTV picture quality has been compared to the DVD format, and for some viewers the perceived quality is nearly comparable to HDTV. EDTV models are generally priced lower than HDTVs, and many consumers were content to sacrifice image quality when it meant saving a thousand bucks. But HDTV prices have now dropped so much that EDTV may not seem like much of a value.

EDTVs are available in wide-screen (16:9 aspect ratio) or conventional (4:3) formats.

If you get all of your TV programming through a direct-broadcast satellite service (and receive your local channels via satellite), you should still be OK. For more details, see our Facts for satellite subscribers.

For cable customers, the picture remains murky. If you have digital cable, you should be fine. What about standard analog cable subscribers? The answer is not yet clear. Analog cable customers may need additional equipment, which cable companies may elect to provide. Or they may need to upgrade to digital cable. The FCC is examining the issue, and a solution should become clearer as the shutdown of analog TV broadcasts approaches. See our Facts for cable customers.

The rest of this answer applies to viewers who watch over-the-air broadcasts: You will need either a TV with a digital tuner or a set-top converter box that attaches to your analog TV. Without a converter box, analog TVs will no longer receive broadcasts once the switch to digital broadcasting is complete.

Beware of aging stocks of analog televisions still on the shelves, though in diminishing numbers, at some retail stores. The FCC requires retailers to display a label warning that such sets will need converter boxes after February 17, 2009.

digital tuners—so they, too, will require set-top boxes to receive broadcasts after the conversion. (The HD-Ready designation is sometimes misconstrued, as might be expected. Some stores have been known to misapply the label.)

Again, the key question is: Does your set have a digital tuner? How can you tell? A digital tuner is sometimes called an “ATSC tuner,” after the Advanced Television Systems Committee, which created the U.S. digital TV standard. So look for a label that refers to an ATSC or digital (or “ATSC digital”) tuner. A TV labeled “HD Built-In” or “Integrated HDTV” should include a digital tuner.

Also: Many viewers will need better antennas. A household that gets acceptable or marginal analog TV reception with an indoor antenna may need an outdoor one to get digital broadcasts.

For more details, see our Facts for over-the-air viewers.

(If you already receive all of your TV programming via digital cable or direct-broadcast satellite, you shouldn’t need to buy a separate converter box. What about standard analog cable subscribers? The answer is not yet clear. Analog cable customers may need additional equipment, which cable companies may elect to provide. Or they may need to upgrade to digital cable. The solution should become clearer as the shutdown of analog TV broadcasts approaches.)

After the switch from analog to digital broadcasts is complete, analog TVs will be incapable of receiving over-the-air broadcasts without the addition of a set-top converter box. The function of the box is to take in digital signals, convert them to analog form and send them to your TV. While the image you see on an analog TV won’t be high-definition, you should notice a slight improvement.

A set-top receiver will also be needed for a digital TV that does not include a built-in digital tuner, if you plan to use it for over-the-air reception. This includes TVs labeled “HD-ready.” For more details, see Will my current TV still work after the switch from analog to digital?

As the deadline for switching to digital approaches, converter boxes are expected to become more widely available through mass retailers, electronics stores and online retailers. The federal government will make coupons available to consumers to help defray the cost of the converter boxes.

(Other types of set-top box (STB) devices exist, including those provided by cable or satellite companies and others designed to marry televisions and personal computers. In this answer, however, we are concerned only with set-top converter boxes for receiving over-the-air digital broadcasts.)

For more details, see our section on Converter Boxes.

Expect to pay $30 to $75, according to a government estimate in early 2007, for a basic DTV converter box. Retail prices may start higher but fall as demand for the device increases. Two leading manufacturers are now targeting a $25 price for entry models.

A converter box that includes a DVD recorder, digital video recorder (DVR) or other high-end features will command a higher price than a bare-bones model. But remember, the $40-off coupon applies toward the purchase of a basic DTV converter only, according to government rules.

Related:
• RCA slashes price on DTV converter box
• LG touts value-priced converter box

The digital TV transition plan received final approval from Congress and was signed into law by President George W. Bush in February of 2006. (The law is being challenged in court on procedural grounds, but the current cutoff date appears likely to stick.)

For the latest updates on the transition, watch DTV Facts.

No deadline has been established for low-power stations, which have a limited broadcast range (and limited viewership) in rural or urban areas. TV translator stations, which retransmit signals from full-power stations, are in the same boat. Under the current plan, these stations will continue analog broadcasts after the dominant stations have switched to digital.

Between October 2007 and September 2009, a federal program will make payments to eligible low-power stations to assist with the transition to digital TV. The program will be administered by the National Telecommunications and Information Administration (NTIA), which is part of the Commerce Department.

Digital TV allows each local station to offer up to five or six separate program streams at once.

For details, see What is multicasting?

That’s right: More local channels. A single station can now provide multiple channels of separate programming simultaneously, free and over the air. Each separate program stream is called a multicast. New multicast channels are already on the air in many metropolitan areas throughout the U.S., and in some smaller markets, too.

Thanks to digital TV, we can now have five or six channels in one. This magical feat is accomplished by using the broadcast spectrum more efficiently.

Compared with analog TV, local broadcasters can now send pictures, sound and other information over the public airwaves in smaller packages. The packages are so small, in fact, that your local digital TV station can broadcast not just the single channel you’ve always had, but up to five more.

HDTV broadcasts—which must be sent over the air in bigger packages— limit broadcasters’ ability to multicast. See Are HDTV and multicasts competing technologies?

(Also, multicast technology allows some stations to rent out unused portions of their FCC-licensed spectrum allotment to pay-TV providers, or to use them for other information services.)

Many broadcasters already offer multicast channels today, which are available over the air to viewers who own newer TVs equipped with digital tuners. For example, channel 4 in your area may offer separate digital programming streams on channels 4.1, 4.2, and 4.3 in the digital band. A converter box will allow you to watch multicast channels on your old analog TV.

Muticasting can also be called “multiplexing.”

To provide high-definition television (HDTV) images with surround sound, broadcasters must send huge chunks of information over the airwaves. During HD broadcasts, a local station has only enough room left in the digital pipe (”bandwidth”) to provide one or two more multicast programming streams, rather than perhaps four more otherwise.

A station may “downconvert” a program that was produced in HD into a lower-quality form of HD, or even into standard definition, to make room for more multicast channels. Viewers equipped with HD displays may notice diminished quality in such cases.

It’s a classic case of quality vs. quantity—and a zero-sum choice.

Station owners must weigh the costs and benefits of providing a single program in high-def or multiple programs in standard definition (SD). Will one show in HD bring in as many viewers in the desired demographic as multiple shows in SD? In this calculation, a key consideration for broadcasters is whether cable systems would carry the additional multicast channels, vastly increasing the size of the potential audience.

HDTV and multicasting may also be seen as complimentary, in that many stations offer high-definition programs at certain times of the broadcast day (especially during prime time) but add additional multicasts at others.

Multicast TV offerings in some cities include round-the-clock weather (can you ever have too much weather? Umm, maybe…) and a wide range of public television programming.

Public TV, with the most ambitious plans for multicasting, announced the launch of four channels:

• Viva TV: Spanish-language programming.

• PBS Kids Go!: Shows aimed at school-age children.

• World: Documentaries and public affairs.

• Create: How-to, travel and possibly some local programming.

Create is already on the air. Viva and PBS Kids Go! are scheduled to debut in fall 2006, with World slated for January 2007. The channels should be available in many TV markets, over the air or on cable.

Commercial networks may also offer feeds on multicast channels.

And, hate to say this, but they might be a tempting outlet for infomercials.

Cable companies are not required to carry any extra “multicast” channels—neither today, nor in 2009, when the transition to digital TV broadcasting will be completed.

Under existing “must-carry” laws, cable systems are required to set aside channels for local analog broadcast stations. As of the cutoff date for analog broadcasts, cable companies must carry local stations in digital form— one channel per station. (This applies to stations that exercise their “must-carry” rights. Commercial stations also have the right to request compensation from cable companies in exchange for carriage—a practice known as “ retransmission consent.” If a consent agreement cannot be reached, the broadcaster can forbid the cable system to carry its station.)

When the shift to digital TV is complete, cable operators must carry local broadcasters’ high-definition programming in HD format (with certain caveats). Instead of broadcasting in HDTV, a local station could choose to offer six standard-definition multicast channels—which, actually, would not require any additional space (or digital “bandwidth”) to send through the cable pipe into your home. But your cable operator would need to reserve extra channel positions for these multicast programming streams, which the company’s owners may consider competitors to existing cable networks (some of which are owned by the same mega-corporations that own many cable companies).

No law compels cable owners to carry multicasts. But cable companies are free to negotiate agreements with station owners to secure slots for multicast channels. Public TV stations already have a deal with major cable systems to provide programming on as many as four digital channels, and some commercial broadcasters also have carriage agreements.

For station owners (including the broadcast networks), billions of dollars in advertising revenues are at stake. A top priority for Washington lobbyists who represent broadcasters is to pass legislation requiring cable companies to carry multicast channels. Thus far, lawmakers have resisted, and the FCC has declined to impose its own multicast must-carry rules. The cable TV industry strongly opposes multicast carriage requirements, saying they would violate the Constitution and cost them billions.

Whether viewers want such channels—perhaps in place of cable networks they currently receive—remains to be seen.

The legal justification for existing “must-carry” rules is that they serve a public purpose: to advance local programming. That said, most local stations fill their schedules with network or syndicated programming, setting aside a small part of the broadcast day for locally produced content.

In those two states, carriage of local broadcast digital TV stations must begin by June 8, 2007; this will include both HDTV and multicast programming.

The Alaska and Hawaii “multicast must-carry” requirement was issued by the FCC as part of its implementation of the Satellite Home Viewer Extension and Reauthorization Act (SHVERA) of 2004. The order was apparently intended to provide greater access to local TV stations for those states’ viewers—many of whom live in remote areas.

No plans have been announced to extend the multicast carriage requirement to other states.

Digital television technology allows local broadcasters to transmit program-guide information to your digital TV (or set-top converter box) along with regular programming content. Digital TV brings electronic program guides—already familiar to many satellite and cable viewers—to households that rely on over-the-air broadcasts.

Sometimes a digital TV will not include a tuner (or decoder or receiver) for receiving over-the-air digital broadcasts. This type of television is known as a digital TV monitor. (Sometimes an HDTV monitor will be labeled “ HD-ready.” Retailers sometimes call this type of TV a “ component solution.”) Consumers who subscribe to cable or satellite TV, or who will use the TV only for watching videos or playing games, may choose a monitor. But if you want to use the monitor to watch over-the-air TV, you will need to purchase additional equipment, such as a set-top receiver.

A digital TV that includes a built-in digital tuner is known as an integrated DTV. (HDTV models with built-in digital tuners may be labeled “ HDTV Integrated.”) The digital tuner may also be called an ATSC tuner (or ATSC digital tuner), after the Advanced Television Systems Committee, which created the U.S. digital TV standard. Like the TVs we have always known, an integrated digital TV is ready to receive broadcasts when attached to an antenna. Keep in mind that if your household currently receives analog TV with an indoor antenna, and the reception quality is merely so-so, you may need a rooftop antenna to receive digital broadcasts.

The labels for digital TV products can be confusing, or even wrong in some cases. If you aren’t sure whether a particular model is a monitor or an integrated DTV, ask your retailer.

An antenna used for watching analog TV over the air can also be used for digital TV, including HDTV. Viewers in some areas, however, will find that a better antenna—a rooftop one, perhaps—is needed to ensure reliable digital TV reception.

First, a word about how digital TV reception differs from analog: Essentially, you either get a perfect digital signal for a particular channel, or nothing at all. It’s what’s known as a “cliff effect.” You will either find yourself at the very peak of reception capability or—less happily—in the deepest ditch.

Digital reception is unlike the familiar world of analog, in which a partial signal above a certain threshold may be viewable (or at last hearable), albeit with static or other flaws. If your digital reception is erratic, it will be difficult to tolerate, because at varying intervals the picture and sound will disappear entirely. You may not want to watch Dateline if Stone Phillips gets replaced every few seconds by a blank, blue screen (though I actually prefer it that way). If you live in an area where reception is marginal, a bargain-priced indoor antenna may not cut it anymore. Even viewers who live in urban areas close to broadcast transmitters may encounter interference caused by neighboring buildings, hills, trees or other obstructions.

To view all television stations in your area, you may need an antenna for both VHF (channels 2 through 13) and UHF (channels 14 and up) bands. With the switch to digital in 2009, many stations will move to new channels and, in some cases, switch bands.

Your antenna should point toward the TV station’s broadcast tower. If you encounter reception problems because local stations’ transmitters are located in different directions, consider installing a rotor (sometimes called a rotator) that can reorient the outdoor antenna according to which channel you are viewing.

On February 17, 2009, television will change.

• What is digital TV?
• What is analog TV?
• Why is the TV broadcasting standard changing from analog to digital?
• Is DTV the same as HDTV?
• What is SDTV?
• What is EDTV?
• Will my current TV still work after the switch from analog to digital?
• What is a set-top converter box?
• How much will converter boxes cost?
• When will analog TV broadcasts end?
• Are any TV stations exempt from the 2009 cutoff date?
• What is a digital TV adapter?
• How do I get my $40 coupon from the converter box subsidy program?
• How does digital TV give me extra local channels for free?
• What is multicasting?
• Are HDTV and multicasting competing technologies?
• What kinds of programming are offered on multicast channels?
• Will my cable company carry the new local multicast channels?
• Will my satellite provider carry the new local multicast channels?
• What is an electronic program guide (EPG)?
• Why doesn’t my new digital TV receive digital broadcasts?
• Do I need a new antenna to get digital TV?
• Full FAQ list