The concept of television is the work of many individuals in the late 19 th and

early 20th centuries. The first practical transmissions of moving images over
a radio system used mechanical rotating perforated disks to scan a scene
Into a time-varying signal that could be reconstructed at a receiver back into
an approximation of the original image. Development of television was
interrupted by the Second World War. After the end of the war, all-electronic
methods of scanning and displaying images became standard. Several
different standards for addition of color to transmitted images were
developed with different regions using technically incompatible signal
standards. Television broadcasting expanded rapidly after World War II,
becoming an important mass medium for advertising, propaganda, and
entertainment.[1]

Television broadcasts can be distributed over the air by VHF and UHF radio
signals from terrestrial transmitting stations, by microwave signals from
Earth orbiting satellites, or by wired transmission to individual consumers by
cable television. Many countries have moved away from the original analog
radio transmission methods and now use digital television standards,
providing additional operating features and conserving radio spectrum
bandwidth for more profitable uses. Television programming can also be
distributed over the Internet.

Television broadcasting may be funded by advertising revenue, by private or

governmental organizations prepared to underwrite the cost, or in some
countries, by television license fees paid by owners of receivers. Some
services, especially carried by cable or satellite, are paid by subscriptions.

Television broadcasting is supported by continuing technical developments

such as long-haul microwave networks, which allow distribution of
programming over a wide geographic area. Video recording methods allow
programming to be edited and replayed for later use. Three-dimensional
television has been used commercially but has not received wide consumer
acceptance owing to the limitations of display methods.
Facsimile transmission systems pioneered methods of mechanically scanning
graphics in the early 19th century. The Scottish inventor Alexander Bain
introduced the facsimile machine between 1843 and 1846. The English
physicist Frederick Bakewell demonstrated a working laboratory version in
1851. The first practical facsimile system, working on telegraph lines, was
developed and put into service by the Italian priest Giovanni Caselli from
1856 onward.[2][3][4]

Willoughby Smith, an English electrical engineer, discovered the

photoconductivity of the element selenium in 1873. This led, among other
technologies, towards telephotography, a way to send still images through
phone lines, as early as in 1895, as well as any kind of electronic image
scanning devices, both still and in motion, and ultimately to TV cameras.

As a 23-year-old German university student, Paul Julius Gottlieb Nipkow

proposed and patented the Nipkow disk in 1884 in Berlin.[5] This was a
spinning disk with a spiral pattern of holes in it, so each hole scanned a line
of the image. Although he never built a working model of the system,
variations of Nipkow’s spinning-disk “image rasterizer” became exceedingly
common.[5] Constantin Perskyi had coined the word television in a paper
read to the International Electricity Congress at the World’s Fair in Paris on
August 24, 1900. Perskyi’s paper reviewed the existing electromechanical
technologies, mentioning the work of Nipkow and others.[6] However, it was
not until 1907 that developments in amplification tube technology, by Lee de
Forest and Arthur Korn among others, made the design practical.[7]

The first demonstration of transmission of images was by Augusto Bissiri: he

transmitted, in 1906, a photograph image from one room to another. In
1917, after other successful attempts by several independent inventors, he
transmitted an image from London to New York City. He patented his
apparatus in Los Angeles in 1928.[8][9][10][11][12]

The first demonstration of instantaneous transmission of images was by

Georges Rignoux and A. Fournier in Paris in 1909. A matrix of 64 selenium
cells, individually wired to a mechanical commutator, served as an electronic
retina. In the receiver, a type of Kerr cell modulated the light and a series of
variously angled mirrors attached to the edge of a rotating disc scanned the
modulated beam onto the display screen. A separate circuit regulated
synchronization. The 8×8 pixel resolution in this proof-of-concept
demonstration was just sufficient to clearly transmit individual letters of the
alphabet. An updated image was transmitted “several times” each second.
[13]

In 1911, Boris Rosing and his student Vladimir Zworykin created a system
that used a mechanical mirror-drum scanner to transmit, in Zworykin’s
words, “very crude images” over wires to the "Braun tube" (cathode-ray tube
or “CRT”) in the receiver. Moving images were not possible because, in the
scanner, “the sensitivity was not enough and the selenium cell was very
laggy”.[14]

In May 1914, Archibald Low gave the first demonstration of his television
system at the Institute of Automobile Engineers in London. He called his
system ‘Televista’. The events were widely reported worldwide and were
generally entitled Seeing By Wireless. The demonstrations had so impressed
Harry Gordon Selfridge that he included Televista in his 1914 Scientific and
Electrical Exhibition at his store.[15][16] It also interested Deputy Consul
General Carl Raymond Loop who filled a US consular report from London
containing considerable detail about Low’s system.[17][18] Low’s invention
employed a matrix detector (camera) and a mosaic screen (receiver/viewer)
with an electro-mechanical scanning mechanism that moved a rotating roller
over the cell contacts providing a multiplex signal to the camera/viewer data
link. The receiver employed a similar roller. The two rollers were
synchronised. It was unlike any other TV system of the 20 th Century and in
some respects, Low had a digital TV system 80 years before modern digital
TV. World War One began shortly after these demonstrations in London and
Low became involved in sensitive military work, and so he did not apply for a
patent until 1917. His “Televista” Patent No. 191,405 titled “Improved
Apparatus for the Electrical Transmission of Optical Images” was finally
published in 1923; delayed possibly for security reasons. The patent states
that the scanning roller had a row of conductive contacts corresponding to
the cells in each row of the array and arranged to sample each cell in turn as
the roller rotated. The receiver’s roller was similarly constructed and each
revolution addressed a row of cells as the rollers traversed over their array of
cells. Loops report tells us that… “The receiver is made up of a series of cells
operated by the passage of polarized light through thin slats of steel, and at
the receiver the object before the transmitter is reproduced as a flickering
image” and “The roller is driven by a motor of 3,000 revolutions per minute,
and the resulting variations of light are transmitted along an ordinary
conducting wire.” And the patent states “into each… space I place a
selenium cell”. Low covered the cells with a liquid dielectric and the roller
connected with each cell in turn through this medium as it rotated and
travelled over the array. The receiver used bimetallic elements that acted as
shutters “transmitting more or less light according to the current passing
through them…” as stated in the patent. Low said the main deficiency of the
system was the selenium cells used for converting light waves into electric
impulses, which responded too slowly thus spoiling the effect. Loop reported
that “The system has been tested through a resistance equivalent to a
distance of four miles, but in the opinion of Doctor Low there is no reason
why it should not be equally effective over far greater distances. The patent
states that this connection could be either wired or wireless. The cost of the
apparatus is considerable because the conductive sections of the roller are
made of platinum…”

In 1914, the demonstrations certainly garnered a lot of media interest, with

The Times reporting on 30 May:

An inventor, Dr. A. M. Low, has discovered a means of transmitting visual

images by wire. If all goes well with this invention, we shall soon be able, it
seems, to see people at a distance.

In 1927, Ronald Frank Tiltman asked Low to write the introduction to his book
in which he acknowledged Low’s work, referring to Low’s related patents with
an apology that they were of ‘too technical a nature for inclusion’.[19] Later
in his 1938 patent Low envisioned a much larger ‘camera’ cell density
achieved by a deposition process of caesium alloy on an insulated substrate
that was subsequently sectioned to divide it into cells, the essence of today’s
technology. Low’s system failed for various reasons, mostly due to its
inability to reproduce an image by reflected light and simultaneously depict
gradations of light and shade. It can be added to the list of systems, like that
of Boris Rosing, that predominantly reproduced shadows. With subsequent
technological advances, many such ideas could be made viable decades
later, but at the time they were impractical

In 1923, Scottish inventor John Logie Baird envisaged a complete television

system that employed the Nipkow disk. Nipkow's was an obscure, forgotten
patent and not at all obvious at the time. He created his first prototypes in
Hastings, where he was recovering from a serious illness. In late 1924, Baird
returned to London to continue his experiments there. On March 25, 1925,
Baird gave the first public demonstration of televised silhouette images in
motion at Selfridges department store in London.[20] Since human faces had
inadequate contrast to show up on his system at this time, he televised cut-
outs and by mid-1925 the head of a ventriloquist's dummy he later named
"Stooky Bill", whose face was painted to highlight its contrast. "Stooky Bill"
also did not complain about the long hours of staying still in front of the
blinding level of light used in these experiments. On October 2, 1925,
suddenly the dummy's head came through on the screen with incredible
clarity. On January 26, 1926, he demonstrated the transmission of images of
real human faces for 40 distinguished scientists of the Royal Institution. This
is widely regarded as being the world's first public television demonstration.
Baird's system used Nipkow disks for both scanning the image and
displaying it. A brightly illuminated subject was placed in front of a spinning
Nipkow disk set with lenses that swept images across a static photocell. At
this time, it is believed that it was a thallium sulphide (Thalofide) cell,
developed by Theodore Case in the US, that detected the light reflected from
the subject. This was transmitted by radio to a receiver unit, where the video
signal was applied to a neon bulb behind a similar Nipkow disk synchronised
with the first. The brightness of the neon lamp was varied in proportion to
the brightness of each spot on the image. As each lens in the disk passed by,
one scan line of the image was reproduced. With this early apparatus, Baird's
disks had 16 lenses, yet in conjunction with the other discs used produced
moving images with 32 scan-lines, just enough to recognize a human face.
He began with a frame-rate of five per second, which was soon increased to
a rate of 121⁄2 frames per second and 30 scan-lines.
In 1927, Baird transmitted a signal over 438 miles (705 km) of telephone line
between London and Glasgow. In 1928, Baird's company (Baird Television
Development Company/Cinema Television) broadcast the first transatlantic
television signal, between London and New York, and the first shore-to-ship
transmission. In 1929, he became involved in the first experimental
mechanical television service in Germany. In November of the same year,
Baird and Bernard Natan of Pathé established France's first television
company, Télévision-Baird-Natan. In 1931, he made the first outdoor remote
broadcast, of the Derby.[21] In 1932, he demonstrated ultra-short
wave television. Baird Television Limited's mechanical systems reached a
peak of 240 lines of resolution at the company's Crystal Palace studios, and
later on BBC television broadcasts in 1936, though for action shots (as
opposed to a seated presenter) the mechanical system did not scan the
televised scene directly. Instead, a 17.5mm film was shot, rapidly developed,
and then scanned while the film was still wet.
The Scophony Company's success with their mechanical system in the 1930s
enabled them to take their operations to the US when World War II curtailed
their business in Britain.
An American inventor, Charles Francis Jenkins, also pioneered the television.
He published an article on "Motion Pictures by Wireless" in 1913, but it was
not until December 1923 that he transmitted moving silhouette images for
witnesses. On June 13, 1925, Jenkins publicly demonstrated the synchronized
transmission of silhouette pictures. In 1925, Jenkins used a Nipkow disk and
transmitted the silhouette image of a toy windmill in motion, over a distance
of five miles (from a naval radio station in Maryland to his laboratory in
Washington, D.C.), using a lensed disk scanner with a 48-line resolution. [22]
[23]
He was granted U.S. patent 1,544,156 (Transmitting Pictures over
Wireless) on June 30, 1925 (filed March 13, 1922). [24]
On December 25, 1926, Kenjiro Takayanagi demonstrated a television
system with a 40-line resolution that employed a Nipkow disk scanner
and CRT display at Hamamatsu Industrial High School in Japan. This
prototype is still on display at the Takayanagi Memorial Museum at Shizuoka
University, Hamamatsu Campus.[25] By 1927, Takayanagi improved the
resolution to 100 lines, which was not surpassed until 1931. [26] He is the man
who completed the first all-electronic television. [27] His research toward
creating a production model was halted by the US after Japan lost World War
II.[25]
On April 7, 1927, a team from Bell Telephone Laboratories demonstrated
television transmission from Washington, D.C. to New York City, using a
prototype array of 50 lines containing 50 individual neon lights each against
a gold-appearing background, as a display to make the images visible to an
audience.[28] The display measured approximately two feet by three feet and
had 2500 total pixels (50x50).
Herbert E. Ives and Frank Gray of Bell Telephone Laboratories gave a
dramatic demonstration of mechanical television on April 7, 1927. The
reflected-light television system included both small and large viewing
screens. The small receiver had a 2 in (51 mm)-wide by 2.5 in (64 mm)-high
screen. The large receiver had a screen 24 in (610 mm) wide by 30 in
(760 mm) high. Both sets were capable of reproducing reasonably accurate,
monochromatic moving images. Along with the pictures, the sets also
received synchronized sound. The system transmitted images over two
paths: first, a copper wire link from Washington, D.C. to New York City, then
a radio link from Whippany, New Jersey. Comparing the two transmission
methods, viewers noted no difference in quality. Subjects of the telecast
included Secretary of Commerce Herbert Hoover. A flying-spot scanner beam
illuminated these subjects. The scanner that produced the beam had a 50-
aperture disk. The disc revolved at a rate of 18 frames per second, capturing
one frame about every 56 milliseconds. (Today's systems typically transmit
30 or 60 frames per second, or one frame every 33.3 or 16.7 milliseconds
respectively.) Television historian Albert Abramson underscored the
significance of the Bell Labs demonstration: "It was in fact the best
demonstration of a mechanical television system ever made to this time. It
would be several years before any other system could even begin to
compare with it in picture quality."[29]
In 1928, WRGB (then W2XCW) was started as the world's first television
station. It broadcast from the General Electric facility in Schenectady, New
York. It was popularly known as "WGY Television".
Meanwhile, in the Soviet Union, Léon Theremin had been developing a mirror
drum-based television, starting with 16-line resolution in 1925, then 32 lines
and eventually 64 using interlacing in 1926. As part of his thesis on May 7,
1926, Theremin electrically transmitted and then projected near-
simultaneous moving images on a five-foot square screen. [23] By 1927 he
achieved an image of 100 lines, a resolution that was not surpassed until
1931 by RCA, with 120 lines.[citation needed]
Because only a limited number of holes could be made in the disks, and
disks beyond a certain diameter became impractical, image resolution in
mechanical television broadcasts was relatively low, ranging from about 30
lines up to about 120. Nevertheless, the image quality of 30-line
transmissions steadily improved with technical advances, and by 1933 the
UK broadcasts using the Baird system were remarkably clear. [30] A few
systems ranging into the 200-line region also went on the air. Two of these
were the 180-line system that Compagnie des Compteurs (CDC) installed
in Paris in 1935, and the 180-line system that Peck Television Corp. started
in 1935 at station VE9AK in Montreal.[31][32]
Anton Codelli (22 March 1875 – 28 April 1954), a Slovenian nobleman, was a
passionate inventor. Among other things, he had devised a miniature
refrigerator for cars and a new rotary engine design. Intrigued by television,
he decided to apply his technical skills to the new medium. At the time, the
biggest challenge in television technology was to transmit images with
sufficient resolution to reproduce recognizable figures. As recounted by
media historian Melita Zajc, most inventors were determined to increase the
number of lines used by their systems – some were approaching what was
then the magic number of 100 lines. But Codelli had a different idea. In 1929,
he developed a television device with a single line – but one that formed a
continuous spiral on the screen. Codelli based his ingenious design on his
understanding of the human eye. He knew that objects seen in peripheral
vision don't need to be as sharp as those in the center. Codelli's mechanical
television system, whose image was sharpest in the middle, worked well, and
he was soon able to transmit images of his wife, Ilona von Drasche-Lazar,
over the air. Despite the backing of the German electronics giant Telefunken,
however, Codelli's television system never became a commercial reality.
Electronic television ultimately emerged as the dominant system, and Codelli
moved on to other projects. His invention was largely forgotten. [33][34]
The advancement of all-electronic television (including image dissectors and
other camera tubes and cathode ray tubes for the reproducer) marked the
beginning of the end for mechanical systems as the dominant form of
television. Mechanical TV usually only produced small images. It was the
main type of TV until the 1930s. The last mechanical television broadcasts
ended in 1939 at stations run by a handful of public universities in the United
States.