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Broadcast television systems (or terrestrial television systems outside the US and Canada) are the encoding or formatting systems for the transmission and reception of terrestrial television signals.
Analog television Analog television is the original television technology that uses analog signals to transmit video and audio. In an analog television broadcast, the brightness, colors and sound are represented by amplitude, phase and frequency of an analog s ...
systems were standardized by the International Telecommunication Union in 1961,Final acts of the European Broadcasting Conference in the VHF and UHF bands. Stockholm, 1961.
/ref> with each system designated by a letter ( A- N) in combination with the color standard used ( NTSC, PAL or
SECAM SECAM, also written SÉCAM (, ''Séquentiel de couleur à mémoire'', French for ''color sequential with memory''), is an analog color television system that was used in France, some parts of Europe and Africa, and Russia. It was one of th ...
) - for example PAL-B, NTSC-M, etc.). These analog systems for TV broadcasting dominated until the 2010s. With the introduction of digital terrestrial television (DTT), they were replaced by four main systems in use around the world:
ATSC Advanced Television Systems Committee (ATSC) standards are an American set of standards for digital television transmission over terrestrial, cable and satellite networks. It is largely a replacement for the analog NTSC standard and, like that ...
,
DVB Digital Video Broadcasting (DVB) is a set of international open standards for digital television. DVB standards are maintained by the DVB Project, an international industry consortium, and are published by a Joint Technical Committee (JTC) o ...
,
ISDB Integrated Services Digital Broadcasting (ISDB; Japanese: , ''Tōgō dejitaru hōsō sābisu'') is a Japanese broadcasting standard for digital television (DTV) and digital radio. ISDB supersedes both the NTSC-J analog television system and ...
and
DTMB DTMB (Digital Terrestrial Multimedia Broadcast) is the digital TV standard for mobile and fixed devices, developed in the People's Republic of China. It is used there and in both of their special administrative regions (Hong Kong and Macau), and ...
.


Analog television systems

Every analog television system bar one began as a
black-and-white Black-and-white (B&W or B/W) images combine black and white in a continuous spectrum, producing a range of shades of grey. Media The history of various visual media began with black and white, and as technology improved, altered to color. ...
system. Each country, faced with local political, technical, and economic issues, adopted a color television standard which was grafted onto an existing
monochrome A monochrome or monochromatic image, object or palette is composed of one color (or values of one color). Images using only shades of grey are called grayscale (typically digital) or black-and-white (typically analog). In physics, monochro ...
system such as
CCIR System M CCIR System M, sometimes called 525–line, monochrome NTSC or NTSC-M, is the analog broadcast television system approved by the FCC (upon recommendation by the National Television Systems Committee - NTSC) for use in the United States since ...
, using gaps in the video spectrum (explained below) to allow color transmission information to fit in the existing channels allotted. The grafting of the color transmission standards onto existing monochrome systems permitted existing monochrome television receivers predating the changeover to color television to continue to be operated as monochrome television. Because of this compatibility requirement, color standards added a second signal to the basic monochrome signal, which carries the color information. The color information is called
chrominance Chrominance (''chroma'' or ''C'' for short) is the signal used in video systems to convey the color information of the picture (see YUV color model), separately from the accompanying luma signal (or Y' for short). Chrominance is usually represen ...
with the symbol C, while the black and white information is called the luminance with the symbol Y. Monochrome television receivers only display the luminance, while color receivers process both signals. Though in theory any monochrome system could be adopted to a color system, in practice some of the original monochrome systems proved impractical to adapt to color and were abandoned when the switch to color broadcasting was made. All countries used one of three color standards: NTSC, PAL, or SECAM. For example, CCIR System M was often used in conjunction with NTSC standard, to provide color analog television and the two together were known as NTSC-M.


Pre–World War II systems

A number of experimental and broadcast pre-WW2 systems were tested. The first ones were mechanically based and of very low resolution, sometimes with no sound. Later TV systems like with
405 lines The 405-line monochrome analogue television broadcasting system was the first fully electronic television system to be used in regular broadcasting. The number of television lines influences the image resolution, or quality of the picture. It was ...
used in UK or
441 lines __NOTOC__ Year 441 ( CDXLI) was a common year starting on Wednesday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Seleucus without colleague (or, less frequently, year ...
(Germany, France, Italy, US) were electronic. These systems were mostly experimental and national, with no defined international standards, and didn't resume broadcasting after the war. An exception was the UK 405-line system, that resumed broadcasts and was the first to be standardized by ITU as System A, remaining in operation until 1985.


ITU standards

On an international conference in Stockholm in 1961, the International Telecommunication Union designated standards for broadcast television systems (ITU System Letter Designation). Each standard is designated by a letter (A-M). On
VHF Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter. Frequencies immediately below VHF ...
bands I, II and
III III or iii may refer to: Companies * Information International, Inc., a computer technology company * Innovative Interfaces, Inc., a library-software company * 3i, formerly Investors in Industry, a British investment company Other uses * ...
the
405 __NOTOC__ Year 405 ( CDV) was a common year starting on Sunday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Stilicho and Anthemius (or, less frequently, year 1158 ''Ab ...
,
625 __NOTOC__ Year 625 ( DCXXV) was a common year starting on Tuesday (link will display the full calendar) of the Julian calendar. The denomination 625 for this year has been used since the early medieval period, when the Anno Domini calendar era ...
and 819-line systems could be used: *A – 405-line system *B – 625-line system *C – Belgian 625-line system *D – I.B.T.O. 625-line system *E – 819-line system *F – Belgian 819-line system On
UHF Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (on ...
bands Bands IV and V only 625-line systems were adopted, with the difference being transmission parameters like channel bandwidth. *G – 625-line system, 5 MHz video bandwidth *H – 625-line system, 5 MHz video bandwidth *I – 625-line system, 5.5 MHz video bandwidth *K – 625-line system, 6 MHz video bandwidth *L – 625-line system, 6 MHz video bandwidth Following further conferences and the introduction of color television, by 1966 each standard was designated by a letter (A-M) in combination with a color standard (NTSC, PAL, SECAM). This completely specifies all of the monaural analog television systems in the world (for example, PAL-B, NTSC-M, etc.). The following table gives the principal characteristics of each standard. Except for lines and frame rates, other units are megahertz (MHz). * ''Also see:''
television channel frequencies The following tables show the frequencies assigned to broadcast television channels in various regions of the world, along with the ITU letter designator for the system used. The frequencies shown are for the analogue video and audio carriers. ...


Notes by system

;A: Early United Kingdom and Ireland VHF system (B&W only). First electronic TV system, introduced in 1936. Vestigial sideband filtering introduced in 1949. Discontinued on 23 November 1982 in Ireland and on 2 January 1985 in the UK. ;B: VHF-only in most Western European countries (combined with system G and H on UHF); VHF and UHF in Australia. Originally known as the Gerber standard. ;C: Early VHF system; used only in Belgium, Italy, the Netherlands and Luxembourg, as a compromise between Systems B and L. Discontinued in 1977. ;D: The first 625-line system. Used on VHF only in most countries (combined with system K on UHF). Used in the Mainland China (PAL-D) on both VHF and UHF. ;E: Early
French French (french: français(e), link=no) may refer to: * Something of, from, or related to France ** French language, which originated in France, and its various dialects and accents ** French people, a nation and ethnic group identified with Franc ...
VHF system (B&W only); very good (near HDTV) picture quality but uneconomical use of bandwidth. Sound carrier separation +11.15 MHz on odd numbered channels, -11.15 MHz on even numbered channels. Discontinued in 1984 (France) and 1985 (Monaco). ;F: Early VHF system used only in Belgium, Italy, the Netherlands and Luxembourg; allowed French 819-line television programming to be broadcast on the 7 MHz VHF channels used in those countries, at a substantial cost in horizontal resolution. Discontinued in 1969. ;G: UHF only; used in countries with System B on VHF, except Australia. ;H: UHF only; used only in Belgium, Luxembourg, Netherlands and Former Yugoslavia. Similar to System G with a 1.25 MHz vestigal sideband. ;I: Used in the UK, Ireland, Southern Africa, Macau, Hong Kong and Falkland Islands. ;J: Used in Japan (see system M below). Identical to system M except that a different black level of 0
IRE Ire or IRE may refer to: Ire * Extreme anger; intense fury * Irē, the Livonian name for Mazirbe, Latvia * A town in Oye, Nigeria * ''Ire'' (album), a 2015 album by the Australian metalcore band Parkway Drive * Ire (Iliad), a town mentioned in ...
is used instead of 7.5 IRE. Although the ITU specified a frame rate of 30 fields, 29.97 was adopted with the introduction of NTSC color to minimize visual artifacts. Discontinued in 2012, when Japan transitioned to
digital Digital usually refers to something using discrete digits, often binary digits. Technology and computing Hardware *Digital electronics, electronic circuits which operate using digital signals **Digital camera, which captures and stores digital i ...
. ;K: UHF only; used in countries with system D on VHF, and identical to it in most respects. ;K1: Used only in French overseas departments and territories. ;L: Used only in France. On VHF Band 1 only, the audio is at −6.5 MHz. Discontinued in 2011, when France transitioned to
digital Digital usually refers to something using discrete digits, often binary digits. Technology and computing Hardware *Digital electronics, electronic circuits which operate using digital signals **Digital camera, which captures and stores digital i ...
. It was the last system to use positive video modulation and AM sound. ;M: Used in most of the
Americas The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World. Along with t ...
and
Caribbean The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean S ...
(Except
Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...
, Paraguay, Uruguay and French Guiana), Myanmar, South Korea, Taiwan, Philippines (all NTSC-M), Brazil ( PAL-M) and Laos (SECAM-M). Although the ITU specified a frame rate of 30 fields, 29.97 was adopted with the introduction of NTSC color to minimize visual artifacts. ;N: Originally developed for Japan but not taken up. Adopted by
Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...
, Paraguay and Uruguay (since 1980) (all PAL-N), and used briefly in Brazil and Venezuela. Allows 625-line, 50-frame/s video to be broadcast in a 6-MHz channel, at some cost in horizontal resolution.


Evolution

For historical reasons, some countries use a different video system on
UHF Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (on ...
than they do on the
VHF Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter. Frequencies immediately below VHF ...
bands. In a few countries, most notably the United Kingdom, television broadcasting on VHF has been entirely shut down. Note that the British
405-line The 405-line monochrome analogue television broadcasting system was the first fully electronic television system to be used in regular broadcasting. The number of television lines influences the image resolution, or quality of the picture. It was ...
system A, unlike all the other systems, suppressed the upper sideband rather than the lower—befitting its status as the oldest operating television system to survive into the color era (although was never officially broadcast with color encoding). System A was tested with all three color standards, and production equipment was designed and ready to be built; System A might have survived, as NTSC-A, had the British government not decided to harmonize with the rest of Europe on a 625-line video system, implemented in Britain as PAL-I on UHF only. The French
819 line 819-line was an analog monochrome TV system developed and used in France as television broadcast resumed after World War II. Transmissions started in 1949 and were active up to 1985, although limited to France, Belgium and Luxembourg. It is asso ...
system E was a post-war effort to advance France's standing in television technology. Its 819 lines were almost high definition even by today's standards. Like the British system A, it was VHF only and remained black & white until its shutdown in 1984 in France and 1973 in Monaco. It was tested with SECAM standard in the early stages, but later the decision was made to adopt color in 625-lines L system only. Thus, France adopted system L both on UHF and VHF networks and abandoned system E. Japan had the earliest working HDTV system ( MUSE), with design efforts going back to 1979. The country began broadcasting wideband analog high-definition video signals in the late 1980s using an interlaced resolution of 1125 lines, supported by the
Sony HDVS Sony HDVS is a range of high-definition video equipment developed in the 1980s to support an early analog high-definition television system (used in multiple sub-Nyquist sampling encoding (MUSE) broadcasts) thought to be the broadcast television ...
line of equipment. In many parts of the world, analog television broadcasting has been shut down completely, or in process of shutdown; see Digital television transition for a timeline of the analog shutdown.


Technical aspects


Frames

Ignoring color, all television systems work in essentially the same manner. The monochrome image seen by a camera (later, the luminance component of a color image) is divided into horizontal ''scan lines'', some number of which make up a single image or ''frame''. A monochrome image is theoretically continuous, and thus unlimited in horizontal resolution, but to make television practical, a limit had to be placed on the
bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...
of the television signal, which puts an ultimate limit on the horizontal resolution possible. When color was introduced, this necessity of limit became fixed. All analog television systems are ''
interlaced Interlaced video (also known as interlaced scan) is a technique for doubling the perceived frame rate of a video display without consuming extra bandwidth. The interlaced signal contains two fields of a video frame captured consecutively. This ...
'': alternate rows of the frame are transmitted in sequence, followed by the remaining rows in their sequence. Each half of the frame is called a ''
video field In video, a field is one of the many still images which are displayed sequentially to create the impression of motion on the screen. Two fields comprise one video frame. When the fields are displayed on a video monitor they are "interlaced" so th ...
'', and the rate at which field are transmitted is one of the fundamental parameters of a video system. It is related to the utility frequency at which the electricity distribution system operates, to avoid flicker resulting from the
beat Beat, beats or beating may refer to: Common uses * Patrol, or beat, a group of personnel assigned to monitor a specific area ** Beat (police), the territory that a police officer patrols ** Gay beat, an area frequented by gay men * Battery ...
between the television screen deflection system and nearby mains generated magnetic fields. All digital, or "fixed pixel," displays have progressive scanning and must
deinterlace Deinterlacing is the process of converting interlaced video into a non-interlaced or Progressive scan, progressive form. Interlaced video signals are commonly found in analog television, digital television (HDTV) when in the 1080i format, some D ...
an interlaced source. Use of inexpensive deinterlacing hardware is a typical difference between lower- vs. higher-priced flat panel displays (
Plasma display A plasma display panel (PDP) is a type of flat panel display that uses small cells containing plasma: ionized gas that responds to electric fields. Plasma televisions were the first large (over 32 inches diagonal) flat panel displays to be release ...
, LCD, etc.). All films and other filmed material shot at 24 frames per second must be transferred to video frame rates using a telecine in order to prevent severe motion jitter effects. Typically, for 25 frame/s formats (European among other countries with 50 Hz mains supply), the content is
PAL speedup 576i is a standard-definition digital video mode, originally used for digitizing analog television in most countries of the world where the utility frequency for electric power distribution is 50 Hz. Because of its close association with th ...
, while a technique known as " 3:2 pulldown" is used for 30 frame/s formats (North America among other countries with 60 Hz mains supply) to match the film frame rate to the video frame rate without speeding up the play back.


Viewing technology

Analog television signal standards are designed to be displayed on a
cathode ray tube A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms (oscilloscope), pictu ...
(CRT), and so the physics of these devices necessarily controls the format of the video signal. The image on a CRT is painted by a moving beam of electrons which hits a
phosphor A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or ...
coating on the front of the tube. This electron beam is steered by a magnetic field generated by powerful
electromagnet An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire wound into a coil. A current through the wire creates a magnetic field which is concentrated in the ...
s close to the source of the electron beam. In order to reorient this magnetic steering mechanism, a certain amount of time is required due to the
inductance Inductance is the tendency of an electrical conductor to oppose a change in the electric current flowing through it. The flow of electric current creates a magnetic field around the conductor. The field strength depends on the magnitude of the ...
of the magnets; the greater the change, the greater the time it takes for the electron beam to settle in the new spot. For this reason, it is necessary to shut off the electron beam (corresponding to a video signal of zero luminance) during the time it takes to reorient the beam from the end of one line to the beginning of the next (''horizontal retrace'') and from the bottom of the screen to the top (''vertical retrace'' or '' vertical blanking interval''). The horizontal retrace is accounted for in the time allotted to each scan line, but the vertical retrace is accounted for as ''phantom lines'' which are never displayed but which are included in the number of lines per frame defined for each video system. Since the electron beam must be turned off in any case, the result is gaps in the television signal, which can be used to transmit other information, such as test signals or color identification signals. The temporal gaps translate into a comb-like frequency spectrum for the signal, where the teeth are spaced at line frequency and concentrate most of the energy; the space between the teeth can be used to insert a color subcarrier.


Hidden signaling

Broadcasters later developed mechanisms to transmit digital information on the phantom lines, used mostly for teletext and
closed captioning Closed captioning (CC) and subtitling are both processes of displaying text on a television, video screen, or other visual display to provide additional or interpretive information. Both are typically used as a transcription of the audio port ...
: * PALplus uses a hidden signaling scheme to indicate if it exists, and if so what operational mode it is in. * NTSC has been modified by the
Advanced Television Systems Committee The Advanced Television Systems Committee (ATSC) is an international nonprofit organization developing technical standards for digital terrestrial television and data broadcasting. ATSC's 120-plus member organizations represent the broadcast, b ...
to support an anti-ghosting signal that is inserted on a non-visible scan line. * Teletext uses hidden signaling to transmit information pages. * NTSC
Closed Captioning Closed captioning (CC) and subtitling are both processes of displaying text on a television, video screen, or other visual display to provide additional or interpretive information. Both are typically used as a transcription of the audio port ...
signaling uses signaling that is nearly identical to teletext signaling. *
Widescreen signaling In television technology, Wide Screen Signaling (WSS) is digital metadata embedded in invisible part of the analog TV signal describing qualities of the broadcast, in particular the intended aspect ratio of the image. This allows television b ...
enables a flag to indicate that a 16:9 widescreen image is being broadcast, and allows the TV set to switch to the appropriate display mode.


Overscan

Television images are unique in that they must incorporate regions of the picture with reasonable-quality content, that will never be seen by some viewers.


Interlacing

In a purely analog system, field order is merely a matter of convention. For digitally recorded material it becomes necessary to rearrange the field order when conversion takes place from one standard to another.


Image signal polarization

Another parameter of analog television systems, minor by comparison, is the choice of whether vision modulation is positive or negative. Some of the earliest electronic television systems such as the British 405-line (system A) used positive modulation. It was also used in the two Belgian systems (system C, 625 lines, and System F, 819 lines) and the two French systems (system E, 819 lines, and system L, 625 lines). In positive modulation systems, as in the earlier white facsimile transmission standard, the maximum luminance value is represented by the maximum carrier power; in negative modulation, the maximum luminance value is represented by zero carrier power. All newer analog video systems use negative modulation with the exception of the French System L. Impulsive noise, especially from older automotive ignition systems, caused white spots to appear on the screens of television receivers using positive modulation but they could use simple synchronization circuits. Impulsive noise in negative modulation systems appears as dark spots that are less visible, but picture synchronization was seriously degraded when using simple synchronization. The synchronization problem was overcome with the invention of phase-locked synchronization circuits. When these first appeared in Britain in the early 1950s one name used to describe them was "flywheel synchronisation." Older televisions for positive modulation systems were sometimes equipped with a peak video signal inverter that would turn the white interference spots dark. This was usually user-adjustable with a control on the rear of the television labeled "White Spot Limiter" in Britain or "Antiparasite" in France. If adjusted incorrectly it would turn bright white picture content dark. Most of the positive modulation television systems ceased operation by the mid-1980s. The French System L continued on up to the transition to digital broadcasting. Positive modulation was one of several unique technical features that originally protected the French electronics and broadcasting industry from foreign competition and rendered French TV sets incapable of receiving broadcasts from neighboring countries. Another advantage of negative modulation is that, since the synchronizing pulses represent maximum carrier power, it is relatively easy to arrange the receiver
automatic gain control Automatic gain control (AGC) is a closed-loop feedback regulating circuit in an amplifier or chain of amplifiers, the purpose of which is to maintain a suitable signal amplitude at its output, despite variation of the signal amplitude at the inpu ...
to only operate during sync pulses and thus get a constant amplitude video signal to drive the rest of the TV set. This was not possible for many years with positive modulation as the peak carrier power varied depending on picture content. Modern digital processing circuits have achieved a similar effect but using the front porch of the video signal.


Modulation

Given all of these parameters, the result is a mostly-continuous
analog signal An analog signal or analogue signal (see spelling differences) is any continuous signal representing some other quantity, i.e., ''analogous'' to another quantity. For example, in an analog audio signal, the instantaneous signal voltage varies c ...
which can be modulated onto a radio-frequency carrier and transmitted through an antenna. All analog television systems use
vestigial sideband modulation In radio communications, single-sideband modulation (SSB) or single-sideband suppressed-carrier modulation (SSB-SC) is a type of modulation used to transmit information, such as an audio signal, by radio waves. A refinement of amplitude mod ...
, a form of
amplitude modulation Amplitude modulation (AM) is a modulation technique used in electronic communication, most commonly for transmitting messages with a radio wave. In amplitude modulation, the amplitude (signal strength) of the wave is varied in proportion to t ...
in which one sideband is partially removed. This reduces the bandwidth of the transmitted signal, enabling narrower channels to be used.


Audio

In analog television, the
analog audio Analog recording is a technique used for the recording of analog signals which, among many possibilities, allows analog audio for later playback. Analog audio recording began with mechanical systems such as the phonautograph and phonograph. L ...
portion of a broadcast is invariably modulated separately from the video. Most commonly, the audio and video are combined at the transmitter before being presented to the antenna, but separate aural and visual antennas can be used. In all cases where negative video is used, FM is used for the standard monaural audio; systems with positive video use AM sound and intercarrier receiver technology cannot be incorporated. Stereo, or more generally multi-channel, audio is encoded using a number of schemes which (except in the French systems) are independent of the video system. The principal systems are
NICAM Near Instantaneous Companded Audio Multiplex (NICAM) is an early form of lossy compression for digital audio. It was originally developed in the early 1970s for point-to-point links within broadcasting networks.Croll, M.G., Osborne, D.W. and Sp ...
, which uses a digital audio encoding; double-FM (known under a variety of names, notably
Zweikanalton Zweikanalton ("two-channel sound") or A2 Stereo, is an analog television sound transmission system used in Germany, Austria, Australia, Switzerland, Netherlands and some other countries that use or used PAL-B or PAL-G. TV3 Malaysia formerly us ...
, A2 Stereo, West German Stereo, German Stereo or IGR Stereo), in which case each audio channel is separately modulated in FM and added to the broadcast signal; and
BTSC Multichannel Television Sound, better known as MTS, is the method of encoding three additional audio channels into an analog NTSC-format audio carrier. It was developed by the Broadcast Television Systems Committee, an industry group, and somet ...
(also known as MTS), which multiplexes additional audio channels into the FM audio carrier. All three systems are compatible with monaural FM audio, but only
NICAM Near Instantaneous Companded Audio Multiplex (NICAM) is an early form of lossy compression for digital audio. It was originally developed in the early 1970s for point-to-point links within broadcasting networks.Croll, M.G., Osborne, D.W. and Sp ...
may be used with the French AM audio systems.


Digital television systems

The situation with worldwide digital television is much simpler by comparison. Most digital television systems are based on the MPEG transport stream standard, and use the H.262/MPEG-2 Part 2 video
codec A codec is a device or computer program that encodes or decodes a data stream or signal. ''Codec'' is a portmanteau of coder/decoder. In electronic communications, an endec is a device that acts as both an encoder and a decoder on a signal or ...
. They differ significantly in the details of how the transport stream is converted into a broadcast signal, in the video format prior to encoding (or alternatively, after decoding), and in the audio format. This has not prevented the creation of an international standard that includes both major systems, even though they are incompatible in almost every respect. The two principal digital broadcasting systems are
ATSC standards Advanced Television Systems Committee (ATSC) standards are an American set of standards for digital television transmission over terrestrial, cable and satellite networks. It is largely a replacement for the analog NTSC standard and, like that ...
, developed by the
Advanced Television Systems Committee The Advanced Television Systems Committee (ATSC) is an international nonprofit organization developing technical standards for digital terrestrial television and data broadcasting. ATSC's 120-plus member organizations represent the broadcast, b ...
and adopted as a standard in most of North America, and
DVB-T DVB-T, short for Digital Video Broadcasting – Terrestrial, is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in Singapore in Feb ...
, the Digital Video Broadcast – Terrestrial system used in most of the rest of the world.
DVB-T DVB-T, short for Digital Video Broadcasting – Terrestrial, is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in Singapore in Feb ...
was designed for format compatibility with existing direct broadcast satellite services in Europe (which use the DVB-S standard, and also sees some use in
direct-to-home Satellite television is a service that delivers television programming to viewers by relaying it from a communications satellite orbiting the Earth directly to the viewer's location. The signals are received via an outdoor parabolic antenna commo ...
satellite dish providers in North America), and there is also a
DVB-C Digital Video Broadcasting - Cable (DVB-C) is the DVB European consortium standard for the broadcast transmission of digital television over cable. This system transmits an MPEG-2 or MPEG-4 family digital audio/digital video stream, using a QA ...
version for cable television. While the ATSC standard also includes support for satellite and cable television systems, operators of those systems have chosen other technologies (principally DVB-S or proprietary systems for satellite and
256QAM Quadrature amplitude modulation (QAM) is the name of a family of digital modulation methods and a related family of analog modulation methods widely used in modern telecommunications to transmit information. It conveys two analog message signal ...
replacing VSB for cable). Japan uses a third system, closely related to DVB-T, called ISDB-T, which is compatible with Brazil's SBTVD. The People's Republic of China has developed a fourth system, named DMB-T/H.


ATSC

The terrestrial ATSC system (unofficially ATSC-T) uses a proprietary
Zenith The zenith (, ) is an imaginary point directly "above" a particular location, on the celestial sphere. "Above" means in the vertical direction ( plumb line) opposite to the gravity direction at that location (nadir). The zenith is the "highes ...
-developed modulation called
8-VSB 8VSB is the modulation method used for broadcast in the ATSC digital television standard. ATSC and 8VSB modulation is used primarily in North America; in contrast, the DVB-T standard uses COFDM. A modulation method specifies how the radio sig ...
; as the name implies, it is a vestigial sideband technique. Essentially, analog VSB is to regular amplitude modulation as 8VSB is to eight-way
quadrature amplitude modulation Quadrature amplitude modulation (QAM) is the name of a family of digital modulation methods and a related family of analog modulation methods widely used in modern telecommunications to transmit information. It conveys two analog message signal ...
. This system was chosen specifically to provide for maximum spectral compatibility between existing analog TV and new digital stations in the United States' already-crowded television allocations system, although it is inferior to the other digital systems in dealing with
multipath interference In radio communication, multipath is the propagation phenomenon that results in radio signals reaching the receiving antenna by two or more paths. Causes of multipath include atmospheric ducting, ionospheric reflection and refraction, and refl ...
; however, it is better at dealing with impulse noise which is especially present on the VHF bands that other countries have discontinued from TV use, but are still used in the U.S. There is also no
hierarchical modulation Hierarchical modulation, also called layered modulation, is one of the signal processing techniques for multiplexing and modulating multiple data streams into one single symbol stream, where base-layer symbols and enhancement-layer symbols are sy ...
. After demodulation and error-correction, the 8-VSB modulation supports a digital data stream of about 19.39 Mbit/s, enough for one high-definition video stream or several standard-definition services. See Digital subchannel: Technical considerations for more information. On November 17, 2017, the FCC voted 3-2 in favor of authorizing voluntary deployments of
ATSC 3.0 ATSC 3.0 is a major version of the ATSC standards for television broadcasting created by the Advanced Television Systems Committee (ATSC). The standards are designed to offer support for newer technologies, including HEVC for video channels of u ...
, which was designed as the successor to the original ATSC "1.0", and issued a Report and Order to that effect. Full-power stations will be required to maintain a simulcast of their channels on an ATSC 1.0-compatible signal if they decide to deploy an ATSC 3.0 service. On cable, ATSC usually uses
256QAM Quadrature amplitude modulation (QAM) is the name of a family of digital modulation methods and a related family of analog modulation methods widely used in modern telecommunications to transmit information. It conveys two analog message signal ...
, although some use 16VSB. Both of these double the throughput to 38.78 Mbit/s within the same 6 MHz
bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...
. ATSC is also used over satellite. While these are logically called ATSC-C and ATSC-S, these terms were never officially defined.


DTMB

DTMB is the digital television broadcasting standard of the Mainland China, Hong Kong and Macau. This is a fusion system, which is a compromise of different competing proposing standards from different Chinese Universities, which incorporates elements from
DMB-T DTMB (Digital Terrestrial Multimedia Broadcast) is the digital TV standard for mobile and fixed devices, developed in the People's Republic of China. It is used there and in both of their special administrative regions (Hong Kong and Macau), and ...
, ADTB-T and TiMi 3.


DVB

DVB-T uses coded orthogonal frequency division multiplexing (COFDM), which uses as many as 8000 independent carriers, each transmitting data at a comparatively low rate. This system was designed to provide superior immunity from
multipath interference In radio communication, multipath is the propagation phenomenon that results in radio signals reaching the receiving antenna by two or more paths. Causes of multipath include atmospheric ducting, ionospheric reflection and refraction, and refl ...
, and has a choice of system variants which allow data rates from 4 MBit/s up to 24 MBit/s. One US broadcaster,
Sinclair Broadcasting Sinclair Broadcast Group, Inc. (SBG) is a publicly traded American telecommunications conglomerate that is controlled by the descendants of company founder Julian Sinclair Smith. Headquartered in the Baltimore suburb of Cockeysville, Maryland, ...
, petitioned the Federal Communications Commission to permit the use of COFDM instead of 8-VSB, on the theory that this would improve prospects for digital TV reception by households without outside antennas (a majority in the US), but this request was denied. (However, one US digital station, WNYE-DT in
New York New York most commonly refers to: * New York City, the most populous city in the United States, located in the state of New York * New York (state), a state in the northeastern United States New York may also refer to: Film and television * ...
, was temporarily converted to COFDM modulation on an emergency basis for
datacasting Datacasting (data broadcasting) is the broadcasting of data over a wide area via radio waves. It most often refers to supplemental information sent by television stations along with digital terrestrial television (DTT), but may also be applied ...
information to emergency services personnel in lower Manhattan in the aftermath of the
September 11 terrorist attacks The September 11 attacks, commonly known as 9/11, were four coordinated suicide terrorist attacks carried out by al-Qaeda against the United States on Tuesday, September 11, 2001. That morning, nineteen terrorists hijacked four commercia ...
). DVB-S is the original Digital Video Broadcasting forward error coding and modulation standard for
satellite television Satellite television is a service that delivers television programming to viewers by relaying it from a communications satellite orbiting the Earth directly to the viewer's location. The signals are received via an outdoor parabolic antenna commo ...
and dates back to 1995. It is used via satellites serving every continent of the world, including North America. DVB-S is used in both MCPC and
SCPC Single channel per carrier (SCPC) refers to using a single signal at a given frequency and bandwidth. Most often, this is used on broadcast satellites to indicate that radio stations are not multiplexed as subcarriers onto a single video carrier ...
modes for
broadcast network A terrestrial network (or broadcast network in the United States) is a group of radio stations, television stations, or other electronic media outlets, that form an agreement to air, or broadcast, content from a centralized source. For example, ...
feeds, as well as for direct broadcast satellite services like
Sky The sky is an unobstructed view upward from the surface of the Earth. It includes the atmosphere and outer space. It may also be considered a place between the ground and outer space, thus distinct from outer space. In the field of astronomy, ...
and Freesat in the British Isles, Sky Deutschland and HD+ in Germany and Austria, TNT SAT/FRANSAT and
CanalSat Canal+ is a French subscription provider associated to the channel of the same name. It is owned by Vivendi (owner of Canal+) with a hundred percent share. History In 1992, Canalsatellite was launched, the shareholders were Canal+ Group (66 p ...
in France,
Dish Network DISH Network Corporation (DISH, an acronym for DIgital Sky Highway) is an American television provider and the owner of the direct-broadcast satellite provider Dish, commonly known as Dish Network, and the over-the-top IPTV service, Sling TV ...
in the US, and
Bell Satellite TV Bell Satellite TV (french: Bell Télé; formerly known as Bell ExpressVu, Dish Network Canada and ExpressVu Dish Network and not to be confused with Bell's IPTV Fibe TV service) is the division of BCE Inc. that provides satellite television s ...
in Canada. The MPEG transport stream delivered by DVB-S is mandated as MPEG-2. DVB-C stands for Digital Video Broadcasting - Cable and it is the DVB European consortium standard for the broadcast transmission of digital television over cable. This system transmits an MPEG-2 family digital audio/video stream, using a
QAM Quadrature amplitude modulation (QAM) is the name of a family of digital modulation methods and a related family of analog modulation methods widely used in modern telecommunications to transmit information. It conveys two analog message signa ...
modulation with
channel coding In computing, telecommunication, information theory, and coding theory, an error correction code, sometimes error correcting code, (ECC) is used for controlling errors in data over unreliable or noisy communication channels. The central idea is ...
.


ISDB

ISDB is very similar to DVB, however it is broken into 13 subchannels. Twelve are used for TV, while the last serves either as a guard band, or for the
1seg is a mobile terrestrial digital audio/video and data broadcasting service in Japan, Argentina, Brazil, Chile, Uruguay, Paraguay, Peru and the Philippines. Service began experimentally during 2005 and commercially on April 1, 2006. It is designe ...
(ISDB-H) service. Like the other DTV systems, the ISDB types differ mainly in the modulations used, due to the requirements of different frequency bands. The 12 GHz band ISDB-S uses PSK modulation, 2.6 GHz band digital sound broadcasting uses CDM and ISDB-T (in VHF and/or UHF band) uses COFDM with PSK/QAM. It was developed in Japan with MPEG-2, and is now used in Brazil with MPEG-4. Unlike other digital broadcast systems, ISDB includes
digital rights management Digital rights management (DRM) is the management of legal access to digital content. Various tools or technological protection measures (TPM) such as access control technologies can restrict the use of proprietary hardware and copyrighted works ...
to restrict recording of programming.


Comparison of digital terrestrial television systems


Line count

As interlaced systems require accurate positioning of scanning lines, it is important to make sure that the horizontal and vertical timebase are in a precise ratio. This is accomplished by passing the one through a series of electronic divider circuits to produce the other. Each division is by a prime number. Therefore, there has to be a straightforward mathematical relationship between the line and field frequencies, the latter being derived by dividing down from the former. Technology constraints of the 1930s meant that this division process could only be done using small integers, preferably no greater than 7, for good stability. The number of lines was odd because of 2:1 interlace. The 405 line system used a vertical frequency of 50 Hz (Standard AC mains supply frequency in Britain) and a horizontal one of 10,125 Hz (50 × 405 ÷ 2) * 2 × 3 × 3 × 5 gives 90 lines (non interlaced) * 2 × 2 × 2 × 2 × 2 × 3 gives 96 lines (non interlaced) * 2 × 2 × 3 × 3 × 5 gives 180 lines (non interlaced) (used in Germany in mid-1930s before switch to 441-line system) * 2 × 2 × 2 × 2 × 3 × 5 gives 240 lines (used for the experimental Baird transmissions in Britain ee Note 1/small>) * 3 × 3 × 3 × 3 × 3 gives 243 lines * 7 × 7 × 7 gives 343 lines (early North American system also used in Poland and in Soviet Union before WW2) * 3 × 5 × 5 × 5 gives 375 lines * 3 × 3 × 3 × 3 × 5 gives
405 lines The 405-line monochrome analogue television broadcasting system was the first fully electronic television system to be used in regular broadcasting. The number of television lines influences the image resolution, or quality of the picture. It was ...
System A (used in Britain, Ireland and Hong Kong before 1985) * 2 × 2 × 2 × 5 × 11 gives 440 lines (non interlaced) * 3 × 3 × 7 × 7 gives
441 lines __NOTOC__ Year 441 ( CDXLI) was a common year starting on Wednesday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Seleucus without colleague (or, less frequently, year ...
(used by
RCA The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric (GE), Westinghouse, AT&T Corporation and United Fruit Com ...
in North America before the 525-lines NTSC standard was adopted and widely used before WW2 in Continental Europe with different frame rates) * 2 × 3 × 3 × 5 × 5 gives 450 lines (non interlaced) * 5 × 7 × 13 gives 455 lines (used in France before WW2) * 3 × 5 × 5 × 7 gives
525 lines 525-lines is a standard-definition television resolution used mainly in the context of analog systems. Analog broadcast television standards The following International Telecommunication Union standards use 525-lines: * CCIR System J * CCIR Sys ...
System M A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment, is described by its boundaries, structure and purpose and expresse ...
(a compromise between the RCA and Philco systems. Still used today in most of the Americas and parts of Asia) * 3 × 3 × 3 × 3 × 7 gives 567 lines (Developed by Philips used for a while in the late 1940s in the Netherlands) * 5 × 11 × 11 gives 605 lines (proposed by Philco in North America before the 525 standard was adopted) * 5 × 5 × 5 × 5 gives
625 lines 625-lines is a standard-definition television resolution used mainly in the context of analog systems. It was first demonstrated by Mark Iosifovich Krivosheev in 1948. Analog broadcast television standards The following International Telecommunic ...
(
576i 576i is a standard-definition digital video mode, originally used for digitizing analog television in most countries of the world where the utility frequency for electric power distribution is 50 Hz. Because of its close association with t ...
) (designed by SovietOn the beginning of broadcast in 625-lines 60 year s ago, ''625'' magazine (in Russian).
engineers during the mid-late 1940s, introduced to Western Europe by German engineers.) * 2 × 3 × 5 × 5 × 5 gives 750 lines at 50 frames (used for
720p50 720p (1280×720 px; also called HD ready, standard HD or just HD) is a progressive HDTV signal format with 720 horizontal lines/1280 columns and an aspect ratio (AR) of 16:9, normally known as widescreen HDTV (1.78:1). All major HDTV broadcas ...
ee Note 2/small>) * 2 × 2 × 2 × 2 × 3 × 3 × 5 gives 720 lines at 60 frames (used for
720p60 720p (1280×720 px; also called HD ready, standard HD or just HD) is a progressive HDTV signal format with 720 horizontal lines/1280 columns and an aspect ratio (AR) of 16:9, normally known as widescreen HDTV (1.78:1). All major HDTV broadcast ...
ee Note 2/small>) * 3 × 3 × 7 × 13 gives 819 lines ( 737i) (used in France in the 1950s) * 3 × 7 × 7 × 7 gives 1,029 lines (proposed but never adopted around 1948 in France) * 3 × 3 × 5 × 5 x 5 gives 1,125 lines at 25 frames (used for
1080i25 1080i (also known as Full HD or BT.709) is a combination of frame resolution and scan type. 1080i is used in high-definition television (HDTV) and high-definition video. The number "1080" refers to the number of horizontal lines on the screen. ...
but not
1080p25 1080p (1920×1080 progressively displayed pixels; also known as Full HD or FHD, and BT.709) is a set of HDTV high-definition video modes characterized by 1,920 pixels displayed across the screen horizontally and 1,080 pixels down the screen verti ...
ee Note 2/small>) * 3 × 3 × 5 × 5 x 5 gives 1,125 lines at 30 frames (used for 1080i30 but not 1080p30 ee Note 2/small>) ;Notes # The division of the 240-line system is academic as the scan ratio was determined entirely by the construction of the mechanical scanning system used with the cameras used with this transmission system. # The division ratio though relevant to CRT-based systems is largely academic today because modern LCD and
plasma display A plasma display panel (PDP) is a type of flat panel display that uses small cells containing plasma: ionized gas that responds to electric fields. Plasma televisions were the first large (over 32 inches diagonal) flat panel displays to be release ...
s are not constrained to having the scanning in precise ratios. The 1080p high definition system requires 1126 lines in a CRT display. # The System I version of the 625-line standard originally used 582 active lines before later changing to 576 in line with other 625-line systems.


Conversion from one system to another system

Converting between different numbers of lines and different frequencies of fields/frames in video pictures is not an easy task. Perhaps the most technically challenging conversion to make is from any of the 625-line, 25-frame/s systems to system M, which has 525-lines at 29.97 frames per second. Historically this required a frame store to hold those parts of the picture not actually being output (since the scanning of any point was not time coincident). In more recent times, conversion of standards is a relatively easy task for a computer. Aside from the line count being different, it's easy to see that generating 59.94 fields every second from a format that has only 50 fields might pose some interesting problems. Every second, an additional 10 fields must be generated seemingly from nothing. The conversion has to create new frames (from the existing input) in real time. There are several methods used to do this, depending on the desired cost and conversion quality. The simplest possible converters simply drop every 5th line from every frame (when converting from 625 to 525) or duplicate every 4th line (when converting from 525 to 625), and then duplicate or drop some of those frames to make up the difference in frame rate. More complex systems include inter-field
interpolation In the mathematical field of numerical analysis, interpolation is a type of estimation, a method of constructing (finding) new data points based on the range of a discrete set of known data points. In engineering and science, one often has a ...
, adaptive interpolation, and phase correlation.


See also

* Characteristics of television systems. International Telecommunication Union, ITU-R Recommendation BT.470-2. Transmission technology standards *
Amateur television Amateur television (ATV) is the transmission of broadcast quality video and audio over the wide range of frequencies of radio waves allocated for radio amateur (Ham) use. ATV is used for non-commercial experimentation, pleasure, and public service ...
* Broadcast safe *
Channel (broadcasting) In broadcasting, a channel or frequency channel is a designated radio frequency (or, equivalently, wavelength), assigned by a competent frequency assignment authority for the operation of a particular radio station, television station or televis ...
*
Display resolution The display resolution or display modes of a digital television, computer monitor or display device is the number of distinct pixels in each dimension that can be displayed. It can be an ambiguous term especially as the displayed resolution is ...
*
Lists of television channels This article is a list containing lists of television channels. Lists of television channels by continent * Africa * Asia * Europe * North America * Oceania * Latin America Lists of television channels by country * Afghanistan * Austra ...
for lists by country and language. *
North American cable television frequencies The Pan-American television frequencies are different for terrestrial and cable television systems. Terrestrial television channels are divided into two bands: the VHF band which comprises channels 2 through 13 and occupies frequencies between 54 a ...
*
Television channel frequencies The following tables show the frequencies assigned to broadcast television channels in various regions of the world, along with the ITU letter designator for the system used. The frequencies shown are for the analogue video and audio carriers. ...
Defunct analog systems *
405 line 4 (four) is a number, numeral and digit. It is the natural number following 3 and preceding 5. It is the smallest semiprime and composite number, and is considered unlucky in many East Asian cultures. In mathematics Four is the smallest ...
s *
441 line __NOTOC__ Year 441 ( CDXLI) was a common year starting on Wednesday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Seleucus without colleague (or, less frequently, year ...
s *
819 line 819-line was an analog monochrome TV system developed and used in France as television broadcast resumed after World War II. Transmissions started in 1949 and were active up to 1985, although limited to France, Belgium and Luxembourg. It is asso ...
s * MUSE an
analog high-definition television system Analog high-definition television has referred to a variety of analog video broadcast television systems with various display resolutions throughout history. Pre-1940 On 2 November 1936 the BBC began transmitting the world's first public reg ...
. Analog television systems * Intercarrier method * NTSC (525/60) * PAL (color encoding usually used with 625/50 systems) * PAL-M *
PAL-N Phase Alternating Line (PAL) is a colour encoding system for analogue television. It was one of three major analogue colour television standards, the others being NTSC and SECAM. In most countries it was broadcast at 625 lines, 50 fields (25 ...
* PALplus *
SECAM SECAM, also written SÉCAM (, ''Séquentiel de couleur à mémoire'', French for ''color sequential with memory''), is an analog color television system that was used in France, some parts of Europe and Africa, and Russia. It was one of th ...
*
Transposer In broadcasting, a transposer or translator is a device in or beyond the service area of a radio or television station transmitter that rebroadcasts signals to receivers which can’t properly receive the signals of the transmitter because of a p ...
s *
TV transmitters A television transmitter is a transmitter that is used for terrestrial (over-the-air) television broadcasting. It is an electronic device that radiates radio waves that carry a video signal representing moving images, along with a synchronized au ...
Analog television system audio *
BTSC Multichannel Television Sound, better known as MTS, is the method of encoding three additional audio channels into an analog NTSC-format audio carrier. It was developed by the Broadcast Television Systems Committee, an industry group, and somet ...
*
NICAM Near Instantaneous Companded Audio Multiplex (NICAM) is an early form of lossy compression for digital audio. It was originally developed in the early 1970s for point-to-point links within broadcasting networks.Croll, M.G., Osborne, D.W. and Sp ...
(digital, analog pre-emphasis curve) *
Zweiton Zweikanalton ("two-channel sound") or A2 Stereo, is an analog television sound transmission system used in Germany, Austria, Australia, Switzerland, Netherlands and some other countries that use or used PAL-B or PAL-G. TV3 Malaysia formerly us ...
* The defunct MUSE system had a very unusual digital audio subsystem completely unrelated to
NICAM Near Instantaneous Companded Audio Multiplex (NICAM) is an early form of lossy compression for digital audio. It was originally developed in the early 1970s for point-to-point links within broadcasting networks.Croll, M.G., Osborne, D.W. and Sp ...
. Digital television systems * HDTV systems all use MPEG transport technology *
ATSC standards Advanced Television Systems Committee (ATSC) standards are an American set of standards for digital television transmission over terrestrial, cable and satellite networks. It is largely a replacement for the analog NTSC standard and, like that ...
*
DVB-T DVB-T, short for Digital Video Broadcasting – Terrestrial, is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in Singapore in Feb ...
and DVB-T2 *
ISDB Integrated Services Digital Broadcasting (ISDB; Japanese: , ''Tōgō dejitaru hōsō sābisu'') is a Japanese broadcasting standard for digital television (DTV) and digital radio. ISDB supersedes both the NTSC-J analog television system and ...
and ISDB-T International (SBTVD) *
DTMB DTMB (Digital Terrestrial Multimedia Broadcast) is the digital TV standard for mobile and fixed devices, developed in the People's Republic of China. It is used there and in both of their special administrative regions (Hong Kong and Macau), and ...
used in People's Republic of China, Hong Kong and Macau. History * History of television *
Oldest television station This is a list of pre-World War 2 television stations of the 1920s and 1930s. Most of these experimental stations were located in Europe (notably in the United Kingdom, France, Germany, Italy, Poland, the Netherlands, and Russia), Australi ...
*
Television systems before 1940 A number of experimental and broadcast pre World War II television systems were tested. The first ones were mechanical based (mechanical television) and of very low resolution, sometimes with no sound. Later TV systems were electronic (electronic t ...


References


External links


ITU, Characteristics of television systems

FARWAY IRFC, TV and Radio Transmission, Radio Data System Encoders, Broadcasting Technologies


by Alan Pemberton

by Paul Schlyter

a scan from a 1932 French magazine {{DEFAULTSORT:Broadcast Television Systems Broadcasting standards History of television Television technology Television terminology Television transmission standards