Digital TV Glossary of Terms

Following are definitions of terms used in this website related to digital television.  Learn them and impress your friends!

16:9 Aspect Ratio.      
"Sixteen by nine ASPECT RATIO."  An engineer's way of describing the WIDESCREEN shape that is part of the digital TV standard.  This screen shape is based on a ratio of 16 PIXELS of picture width for every 9 PIXELS of picture height.  (Example: the digital TV standard of 1920 PIXELS by 1080 PIXELS is a ratio of 16:9!)  This shape is one third wider than the traditional analog TV aspect ratio of 4:3, and it has more of a movie screen look.  All HDTVs have a 16:9 WIDESCREEN shape because HDTV shows are always produced in a 16:9 aspect ratio. But "STANDARD DEFINITION" DIGITAL TV shows can also be produced in a 16:9 aspect ratio.  They will fill up a 16:9 screen, but they don't have the resolution or detail of a show produced in HDTV. 

4:3 Aspect Ratio.      
"Four by three ASPECT RATIO."  If you read about 16:9 above, you know where we're going!  4:3 is the aspect ratio of traditional analog TV: 4 units of picture width for every 3 units of picture height.  This ratio was defined before (way before) "PIXELS" had been invented, in the 1940's.  This aspect ratio will not disappear anytime soon, as nearly the entire body of television programming since the 1940's has been produced in a 4:3 ASPECT RATIO, and much is still being produced this way today.  A 4:3 program shown on a 16:9 widescreen TV will usually have a PILLARBOX effect: empty pillars on both sides of the picture.  Get used to it! 

5.1 Surround Sound.     
"5 dot 1 surround sound."  A high quality sound production process that is part of the digital TV standard.  It includes 6 separate channels of sound that are recorded.  5 of the channels are "full range" (they carry all the frequencies with CD quality) and are designed to be heard from loudspeakers that have these locations around the TV picture: center (above or below the picture); left side and right side, and left surround and right surround (these two are behind viewers).  The sixth channel adds very low frequencies only, which are produced by bass speakers or a dedicated "subwoofer" speaker (since it carries just low frequencies, this channel is called the "dot one" channel).

Any digital programs (HD or SD) can be produced with "surround sound."  Or digital programs can be produced in four channel sound, two channel stereo, or one channel mono.  Since surround sound provides the most stunning realism and viewer satisfaction, most HDTV shows use it, but it is not a requirement for an HD show. 

Analog Channel Shutoff.       
This is the requirement, designated by law, that says U.S. FULL POWER TV stations must turn off their channels that transmit in the traditional ANALOG TV format before local midnight on February 17, 2009.  Nearly all of them have turned on a new, DIGITAL channel, and they will continue to broadcast the digital channel only.  (LOW POWER and TV TRANSLATOR stations will not turn off their analog channels on that date.) 

Analog TV.         
Describes the traditional TV broadcasting system used in the U.S, and the way that non-digital TVs tune TV signals.  Also refers to TV sets that can receive analog TV signals only.  The actual system name is "NTSC" TV (for "National Television System Committee," which chose the system in 1941.).  Transmitting TV pictures is based on sending "analog" information, which is continuous electrical signals that vary from strong to weak to strong again to send picture data. 

Antenna, TV.       
A device that has the size and shape to pick up the radio signals that are sent by a television transmitter.  The antenna sends the radio signals through an antenna wire to a TV tuner, and the tuner chooses the channel to watch.  A properly adjusted TV antenna can provide free, high quality DIGITAL TV channels to a DIGITAL TV or CONVERTER BOX. Thus, watching "OVER-THE-AIR" TV is an attractive option for many TV owners.  For more information on using a TV antenna, click here.

Aspect ratio.          
Is the relationship between the width of a TV picture to the height of a TV picture.  DIGITAL TV can have a "16:9" aspect ratio, meaning the picture is 16 units wide for every 9 units of height.  Analog TV has a "4:3" aspect ratio.  See "16:9" and "4:3." 

ATSC Tuner.           
Is the type of tuner a TV needs to receive DIGITAL television channels.  It is also the name of the U.S. DIGITAL TV production and broadcasting standard.  The initials stand for "Advanced Television Systems Committee," which developed the digital TV standard in 1995.  The digital standard includes several ways to produce digital TV shows, and it defines how digital TV is transmitted and received.  For more information, click here. 

Bundle.         
Refers to a "package" of entertainment and communications services that may be offered together for discounted price by CABLE TV, SATELLITE TV, TELEPHONE COMPANY, or other communications providers.  A "bundle" can include different combinations of TV service, home phone service, a high speed Internet connection, and cell phone service. 
      
Cable TV.         
Is a service that provides TV channels through a wired connection using a round, "coaxial" cable; the cable is connected to TVs directly or through a SET TOP box.  Cable TV is usually a SUBSCRIPTION TV service, paid for with a monthly or annual fee.  Cable TV companies originally offered only video channels, but today they can provide upgraded video services like HD channels, digital cable and video-on-demand, as well as high speed Internet and phone service, all sent over the cable. 

Community TV System (Community Antenna System). 
An ANTENNA connection for TVs provided by the owners or managers of buildings or areas with many residences, such as apartments, condos, dorm rooms, hotel rooms, or offices.  Viewers who get their TV signal this way may have to take action to watch local stations after the analog channel shutoff.  This depends on whether the TV signals come from an antenna or somewhere else.  For more information, see "Step 4" and select "The TV is connected to a Community TV System."  

Component connection.       
A high quality system for connecting TVs to audio-video devices.  Component connections use 3 wires, with plugs colored red, green, and blue (so they are sometimes called an "RGB" connection).  Component connections handle picture signals only, in an analog format (a separate audio connection is required).  They are superior to older COMPOSITE and S-VIDEO connections.  However, the newer, single cable, all-digital HDMI connection standard is even better quality, and HDMI should be used when both devices to be connected have HDMI connections. 

Composite connection.        
Refers to the oldest and simplest connection that is used to send a TV picture (and usually one or two sound channels) from one video device to another.  It uses a cable with three wires, with yellow plugs (for video), white plugs (left channel sound), and red plugs (right channel sound).  Composite connections are also called "RCA" (the name of the round plugs) connections.  On a digital TV, if HDMI or COMPONENT connections are available, they should be used instead of the poorer-quality composite connections.  For more information, click here.  

Compression.
This is one of the helpful features of digital TV.  When a digital TV program is produced, the video is "compressed." This means that the picture signal is captured or "sampled" millions of times a second. Then the newest "samples" are compared with older ones.  Some sample information may be new, but if the TV picture hasn't changed much, most of the samples are just repeats.  So, most of the time, only the changes in the samples are saved, and the "unchanged" samples are discarded and not sent.  After being compressed like this, a digital TV signal can have less than 3% of its original data, but that is enough information for a digital TV to recreate the full picture.  Because of digital compression, a huge HDTV program with lots of data, as well as several standard video channels, can all be sent at the same time on one digital TV signal. 

TV picture compression does have limits.  When a digital TV picture is changing quickly, such as when a camera follows fast sports action, the compression system make not have enough capacity to capture all the detail in the changes, and parts of a TV picture can temporarily look fuzzy or "blocky." 

Converter Box. 
Also called a "digital TV converter box," or a "converter."  A small electronic device that tunes in DIGITAL TV channels received with an ANTENNA, and turns the picture and sound into signals that can be watched on an older ANALOG TV.   It is basically a complete digital TV receiver, but without a TV screen and sound system.  Converters are purchased by viewers who want to keep watching TV on an analog TV set with an antenna after the analog channel shutoff.  The government is offering $40 coupons to offset the cost of basic converter boxes.  For more information, click here. 

Coupon Program.   
Also: "TV Converter Box Coupon Program."  A program established by Congress to help U.S. residents purchase CONVERTER BOXES.  It's designed to help viewers who watch TV with an ANTENNA on older ANALOG TVs, so they can continue to watch local channels after the analog channel shutoff.  The program allows each U.S. household to request one or two coupons worth $40 each.  Each coupon can be applied toward the purchase of one "eligible" digital TV Converter box. For more information, click here.

Digital Tuner.       
A tuner in a TV set or a CONVERTER BOX that can receive or tune digital TV broadcast channels.  It is also called an ATSC tuner. 

Digital TV (DTV).    
The system of TV program production and broadcasting in the U.S. that uses digital technology.  Also called the ATSC system.  Digital TV is a giant leap forward in technology; it provides high quality reception, including HDTV; multiple programs on one channel, and flexibility for future services like interactive and mobile TV.  However, traditional ANALOG TVs cannot tune in DIGITAL TV channels.  The U.S. is going through a process of converting to digital TV broadcasting, called the DIGITAL TV TRANSITION.

Digital TV Converter Box.    
See CONVERTER BOX.  

Digital TV Transition.     
The process by which the traditional, ANALOG system of broadcasting TV in the U.S. is being replaced by a DIGITAL system of broadcasting.  The first phase of the transition began when U.S. full power TV stations were given new digital channels in the late 1990s and began broadcasting on them.  The second phase will occur when full power TV stations turn off their traditional analog channels on February 17, 2009.  The final phase will occur when all remaining TV stations, including low power and translator stations, convert to digital broadcasting, which has not been scheduled yet.  Since the analog channel shutoff could affect up to 19 million homes that watch TV over-the-air only, the digital TV transition is the focus of a massive governmental and industry awareness campaign.  

Digital Video Recorder (DVR).     
A TV viewing device that records TV programs on a computer hard drive, giving viewers incredible control over how and when they watch TV shows.  A DVR can "pause" a TV show or play back a show segment that has just been recorded.  Also, it can be easily programmed to record programs. DVRs are offered as part of CABLE TV or SATELLITE TV service, or they can be purchased.  Some DVRs include DIGITAL (ATSC) tuners and operate like a sophisticated CONVERTER BOX. 

Dolby Digital AC-3.     
Is the standard used in the DIGITAL TV system for capturing six channels of program sound and compressing it for transmission on the TV signal. 

Front Projection TV.     
A system to watch TV that uses a TV projector near the viewers to shine a TV picture on a screen.  A front projection system can provide the largest, most engaging, and most movie-like TV pictures, and the biggest picture for the money.  But it usually requires the viewing room lighting to be dimmed for the best effect. 

Full Power TV Stations.       
Are the U.S. TV stations that are going to shut off their ANALOG TV channels on February 17, 2009, and continue broadcasting only DIGITAL TV channels.  "Full power" stations are stations that broadcast a powerful TV signal designed to reach most of their communities.  There are additional, LOW POWER TV stations that are not turning off their analog channels.  See LOW POWER STATIONS.

HD.       
Short for "high definition."

HDMI.       
The newest and highest quality connection available on digital TVs and digital devices.  HDMI is short for "High Definition Multimedia Interface."  It carries digital video and audio signals in a single cable, and can easily connect HDTVs to DVD players, video games, A/V receivers, and computers. 

HDTV.        
Short for "high definition TV." 

HDTV-Ready.   
Describes a TV that can display an HDTV program with full picture quality, but does not have a DIGITAL (ATSC) tuner and needs to get an HDTV signal from another device.  An "HDTV-Ready" TV is sometimes called an "HDTV MONITOR." 

High Definition TV.   
Refers to programs that are produced and viewed using the highest quality picture standards that can be broadcast over digital TV.  There are three key factors to an HDTV program:

• they are produced with a WIDESCREEN, 16:9 ASPECT RATIO picture.
• they have a picture "resolution" of either 1920 horizontal PIXELS with 1080 vertical PIXELS, or 1280 horizontal PIXELS with 720 vertical PIXELS. 
• they have a "frame rate" (the number of complete TV pictures made each second) of 24, 30, or 60 frames in a progressive (single, top-to-bottom) scan.

There is one exception is: 1920 by 1080 does not include a 60 frame progressive standard.  Instead, it has a 30 frame "interlaced" scan (scans the odd lines in the picture first, then the even lines).   

The two HDTV standards used for broadcast production most often are "1080i" (for 1920 x 1080 resolution, 30 frames, interlaced scan) and "720p" (for 1280 by 720 resolution, 60 frames, progressive scan).  For more information, click here.

HDTV programs are not required to have surround sound, but the highest quality HDTV productions usually do. 

LCD.        
Liquid Crystal Display.  One of the several technologies used for the screens of flat panel TVs.  It is basically a super-sized computer screen technology.  LCDs are used for nearly all flat panel TVs with less than 40 inches (diagonal) displays, and are now being used for TVs 50 inches diagonal or larger.  For more information, click here.

Letterbox.     
Describes the odd picture you see when a TV show's shape is wider than the TV screen, so the TV show is shrunk to fit on the screen.  This leaves empty bars on the screen above and below the TV show.  TV viewers who have an analog TV (4:3 aspect ratio) that is showing a widescreen program (16:9 aspect ratio) on it will see a letterbox.  Also, TV viewers who have an HDTV (16:9 aspect ratio) that is showing a very wide theatrical movie (2.4:1 aspect ratio) will also see a letterbox. 

Line input (also called an audio-video or AV input). 
On older TVs, this is a connection used to get audio and video signals from another source besides the TV tuner,  such as a DVD, VCR, or video game.  TVs can have one or more line inputs, on both the back and front of the TV.   They may use COMPOSITE and S-VIDEO inputs.  Line inputs are the best way to connect a DIGITAL TV CONVERTER BOX to an analog TV. 

Low Power TV Stations.     
This is a category of TV stations in the U.S. that will continue to broadcast ANALOG channels next year, even after FULL POWER TV stations turn off their analog channels.  Low power TV stations are licensed for local coverage with less transmitter power, though they can be affiliated with any network.  Along with low power stations, there are TV TRANSLATORS which rebroadcast the signals of other TV stations, and they will continue their analog broadcasts.  Viewers who want to watch these stations with an ANTENNA as well as local full power digital stations will need a way to switch between watching and digital channels.  To get a list of low power stations in your community, click here.

Monitor.       
A TV that is used to show pictures and sound from another device, such as a DVD, VCR, or video game.  Nearly any TV can be used as a monitor to watch digital TV channels from a digital TV converter box.  For more information, click here. 

Multicasting.     
The process whereby a TV station can broadcast more than one program at the same time on its DIGITAL channel. A DIGITAL TV can tune in the extra  programs.  A station can "multicast" an HD program plus several SD programs , or it can broadcast up to 8 SD-only programs.  Many digital TV channels are "multicasting" at least two programs. 

NTSC.       
The traditional ANALOG U.S. television broadcasting system, which has been used by TV stations since the 1940s.  NTSC stands for "National Television System Committee," which chose the system in 1941.  NTSC is also used to describe traditional analog TV tuners.  In the DIGITAL TV TRANSITION in the U.S., the NTSC system is being replaced by the digital ATSC broadcasting system. 

Over-the-air.   
A common way to describe receiving local TV channels directly from TV transmitters, using an ANTENNA.  During the first 30 years of TV broadcasting, this was the only way most people could watch TV, before cable TV and satellite TV became widely available.

Pillarbox (also called "Barn Doors"). 
Describes the odd picture you see when a TV show's shape is taller than the TV screen, so the TV show is shrunk to fit on the screen.  This leaves empty bars (or "pillars") on the screen on the left and right side of the TV show.  TV viewers who have a widescreen TV (16:9 aspect ratio) that is showing a traditional 4:3 aspect ratio program will see a pillarbox.  And when an HDTV channel alternates between programs and commercials that have 16:9 and 4:3 aspect ratios, viewers will see the pillarbox come and go (networks sometimes fill the pillars with pictures or colors). 

Pixels. 
Short for "picture elements."  These are the smallest dots in a picture that a DIGITAL TV system can capture with a TV camera, and broadcast, and recreate on a TV screen.  In general, the more pixels that are used to create a TV picture, the higher the picture "resolution" or detail.  HDTV programs use three to six times more pixels than STANDARD DEFINITION programs.  

Plasma.      
One of the technologies used for the screens of flat panel TVs.  It is basically a huge matrix of tiny gas bubbles that light up when they get an electric charge.  Plasmas are popular for flat panel TV sizes of 40 inches (diagonal) inches and larger.  For more information, click here.

Postage stamp.     
Now this is fun: this basically looks like a TV picture that has been "shrunk."  It does not fill up the entire TV screen, and IT sits right in the middle of the screen with a gap on all sides.  You will see this "postage stamp" picture on an analog TV when two things happen together: 
1)  First, the TV is showing a LETTERBOX program (so there are blank bars on the top and bottom of the program), and
2)  Second, inside the LETTERBOX program there is a PILLARBOX program (which has empty bars on both sides). 
Now you have a combination of LETTERBOX and PILLARBOX, and the result is a "postage stamp" picture.  This can appear frequently when a DIGTAL TV CONVERTER is being used with an ANALOG TV set. The solution?  Digital TV converters have a "zoom" or "aspect" button that will magically enlarge the "postage stamp" picture to fill the TV screen.  

Rabbit Ears.       
Ask your grandparents!  It's the simplest indoor antenna you can buy.  It's basically a stand with metal arms that can be stretched and rotated (the arms receive "VHF" channels 2 - 13) and also a small circle of wire (to receive "UHF" channels 14 - 69).  This can be enough of an antenna to receive digital stations that are less than 15 miles away.  For more information, click here.

Rear Projection.       
One of the technologies used to create pictures for large digital TVs.  It is basically a light source that shines through an engine that turns the light into a picture; the picture is reflected by mirrors onto the back of the transparent screen, and the entire system is inside the TV enclosure.  It is used mostly for digital TV screens larger than 50 inches (diagonal).  For more information, click here.  (buying-new-TV)

RF channels.       
Stands for "radio frequency" channels.  For TV stations, these are the radio channels they use to broadcast TV signals.  Under the traditional ANALOG TV system, the RF channel number is the number used to transmit the station, the number used to tune in the station, and the number the station uses to identify itself.  Example: the station that transmits on RF channel 6 calls itself "channel 6," and the TV tuner finds it on channel 6.  But most TV stations have been given a different RF channel to transmit their DIGITAL signal.  Since they want to keep their local channel identity, TV stations usually name their digital channel with their old analog channel number.  That means that the station's digital "tuner" number and its digital RF number are different.  

You will rarely need to know a station's digital RF channel unless: 1) you are choosing a TV ANTENNA, and you need to know if the RF channel is a VHF or UHF channel, or 2) your DIGITAL TV or CONVERTER BOX lets you enter the digital RF channels into memory for easy tuning.  For a list of stations' digital RF channels, click here.

S-Video.     
Is a type of video connection that is used to send just a TV picture from one video device to another.  It is higher quality than the basic COMPOSITE or "RCA" video connection (usually colored yellow).  If two devices have both COMPOSITE and S-VIDEO connections (and no other), then the S-Video connection should be used (audio channels must be connected separately).  For more information, click here.

Satellite TV.    
Refers to a service that provides TV channels that are received through one or more satellite dishes installed at the subscriber's location.  It includes a SET TOP satellite receiver that is connected to one more TVs.  It is a SUBSCRIPTION TV service, paid for with a monthly or annual fee.  Satellite TV can provide local standard and HDTV channels, as well as national networks.  The SET TOPS can include advanced features including DVR and video-on-demand. There are two major satellite TV providers in the U.S.: DIRECTV and Dish Network. 

Scaling.
The electronic process used to make a video picture that was produced in one format fit on a video screen that has a different natural or "native" format.  Scaling is something HDTV sets have to be able to do well, since they are often displaying a program that was not produced in their "native" format.  For example, an HDTV with a 1280 by 720 screen must "downscale" a program produced in 1920 by 1080 so it will fit.  Conversely, an HDTV with a 1920 by 1080 screen must "upscale" a program produced in 1280 by 720 so it will fit the screen.  Higher quality TVs do a better job of scaling.  Scaling is also called "conversion," as in "upconversion" and "downconversion."

SD.         
Short for "standard definition." 

SET TOP.   
Any device used to convert TV signals from the way they get to the TV location into a signal that the TV can display.  SET TOPs are used to convert the TV signals from digital cable, satellite TV dishes, phone lines, fiber cables and digital over-the-air signals.  They can include TV guides and DVRs and have connections for analog TVs, digital TVs, and audio systems.  If you want to get television signals from anything other than an ANTENNA connection or "analog" cable TV, you will probably be using a SET TOP.  

Shape of the picture.     
A topic of conversation for anyone with a DIGITAL TV or a DIGITAL TV CONVERTER, because now that there are two major TV screen shapes (traditional analog and new WIDESCREEN),  TV programs mean for one type of TV are often shown on the other type of TV, and they don't fit perfectly on the screen.  See LETTERBOX, PILLARBOX, and POSTAGE STAMP. 

Standard Definition TV (SDTV).  
Is a part of the  digital TV broadcasting standard that defines how to broadcast quality digital programs that use the minimum necessary digital signal.  SD programs use less than 1/3  the amount of picture information that HD programs use. They can have:

• the same or slightly more lines of resolution than ANALOG TV (640 or 704 horizontal lines);
• a 4:3 or 16:9 ASPECT RATIO (WIDESCREEN), and
• a frame rate of 24, 30, or 60 frames per second (progressive) or 30 frames (interlaced). 

TV stations use a standard definition format if they are producing shows in digital, but not in HD. 

Subscription TV service.    
A service that delivers a package of TV channels to a TV set for a subscription fee.  Subscription TV services include cable TV, satellite TV, and TV services from telephone and communications companies. 

Surround sound.     
A system of up to 6 channels of audio that can be used to broadcast the sound of a digital TV show. See "5.1 SURROUND SOUND."     

Telephone company TV. 
Refers to companies that are basically in the telephone business that also provide TV channels, and may use telephone technology, such as the telephone line to the  home, to send the TV signals.  Some telephone companies use cable TV technology to provide TV; some are partnered with satellite TV companies, and some use new technology such as fiber connections.  

Translators, TV.    
TV translators are low power TV stations that relay the broadcasts of full power TV stations into areas that can't receive the full power station signals, usually in mountainous or rural areas.  They usually use a different channel number than the channel they relay.  TV translators will continue to broadcast in analog only through next year, and are not yet switching to digital.  Viewers who want to watch translators with an ANTENNA as well as FULL POWER digital stations will need a way to switch between watching ANALOG and DIGITAL channels.  

UHF channels.       
TV broadcast channels 14 through 69 are UHF channels.  They require a "UHF" antenna for reception. UHF stands for "ultra high frequency."  (After the analog channel shutoff on February 17, 2009, the UHF channels will be channels 14 through 51.  Channels 52 and above are going back to the government.)

VHF channels.         
TV broadcast channels 2 through 13 are VHF channels.  They require a "VHF" antenna for reception. VHF stands for "very high frequency."

Widescreen.       
A simple way to describe the shape of the TV screen that digital TVs use.  The digital TV standard uses a picture that is one third wider than a tradtional analog TV picture.  See 16:9 ASPECT RATIO.

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