It didnt happen overnight
Every image we see with our own eyes is made up of variations of light intensity
(tones) and wavelengths (colour). Light is reflected from what we are looking at to
millions of tiny filaments in our retinas. From there, each bit of light, in the
form of an electric current, is sent through the optic nerve to the brain. The brain
co-ordinates these bits and we see the total image. At its most basic level television
too gathers bits of light, organizes them, and sends them to your television set
where they are reassembled and appear at the click of a button.
Television was not invented by a lone genius in a moment of inspiration.
It evolved over decades through the contributions of many. The early contributors
to its development were visionaries frequently working alone or with a few colleagues,
without big laboratories or big money. These television pioneers struck out in two
different directions: mechanical and electronic. Electronic would ultimately win,
in large part due to later work by large corporate research laboratories, but in
the beginning the mechanical approach had the advantage because of its greater simplicity.
In 1884 Paul Nipkow, a young German scientist, was the first to try to transmit a moving
image along wires. His theory combined two important principles: the photoelectric effect,
discovered by Joseph May in 1873, and the persistence of vision. Persistence of vision is
the phenomenon by which the brain continues to see an image for a split second after it
is gone, so that a series of separate but rapidly changing images are perceived as continuous.
Nipkows breakthrough was the scanner. He punched holes in the shape of a spiral in a
metal disc. As it rotated between the subject and a light source it broke down the image
into a series of lines of varying intensity. These lines, converted into electricity by
a photoelectric cell, were sent to a receiver. There, a light reacted to the changing signal,
shone through another disc rotating synchronously and created a series of images. Nipkows
discs scanned 24 lines per picture and rotated 10 times per second. The Museums collection
contains two examples of scanning discs (701455, 690981*) as well as components of a mechanical
television camera (700232).
|Nipkow scanning disc (690981), used to break an image into a series of lines. (CSTM/Peter Lindell)|
The first television system to be used for regular broadcast was developed by John Logie Baird.
It was based on Nipkows disc with a transmitter and receiver built around it. In 1926 the Britsh
Broadcasting Corporation (BBC) transmitted his 50-line picture signals, the first experimental TV
broadcast in Britain. Baird improved his system bringing it to a peak of 240 lines and 25 pictures
per second. Using his equipment, the BBC inaugurated a television service in 1932.
In 1931 radio station CKAC in Montreal broadcast the very first TV signals to go on the air
in Canada. The picture was red and black and about 40 mm by 40 mm in size. A year later, Canadian
Television Ltd (CTL) was founded by Douglas West. In July of that year, with Leonard Spencer,
Chief Engineer of CKAC, West produced Canadas first live TV broadcast: a violinist, a singer
and a cartoonist. They continued to broadcast programs twice a week but there were only about
twenty receiver sets and the experiment proved to be ahead of its time. During its short life
CTL hired a young engineer, J. Alphonse Ouimet, later to become President of the CBC, who built
a mechanical receiver that is now in the collection (691044).
|Mechanical television (691044), designed by Alphonse Ouimet, Montreal, 1932. (CSTM/Peter Lindell)|
In 1908, A. A. Campbell-Swinton, a British engineer, proposed a scanning system that used
an electron beam generated by cathode-ray tubes (CRTs) in both the transmitting and the receiving
ends. As early as 1897, Ferdinand Braun had directed a stream of electrons at the fluorescent
inner surface of a CRT. He found that he could deflect the spot of light created on the face
of the tube using magnetic fields outside the tube. This was the basis of the oscilloscope
and later, the picture tube. The Museums collection contains many examples of CRTs.
A viable electronic system would also need a camera tube. The race to create this essential
component had three main competitors, the British team at EMI led by Isaac Schoenberg,
and in America, Vladimir Zworykin at Westinghouse and later RCA (Radio Corporation of America), and Philo Farnsworth,
an independent inventor.
||Iconoscope tube (670824), ca 1940, used in first commercial TV cameras in North America. (CSTM/Peter Lindell)
Zworykin demonstrated his solution, the iconoscope (670824) in 1928. Farnsworth patented
his image-dissector in 1930. In 1932 EMI introduced the emitron camera tube, which out-performed
Bairds mechanical system. The electronic die was cast.
In Britain in 1937, a system built around EMIs emitron provided the first regular high
definition (for that time) television broadcast service in the world. The British standard
was set at 405 lines and 25 pictures per second (replaced by a 625 line standard in 1964).
The museum has one example of a 1938 EMI receiver built to the 405 line standard (750621).
|EMI receiver (750621), 1938. Britain launched the worlds first regular electronic television service in 1937. (CSTM/Peter Lindell)|
Of the two American devices, the iconoscope and the image-dissector, the iconoscope proved
more workable. In 1939, RCAs National Broadcasting Company (NBC) kicked off experimental
broadcasts with a live program from the New York Worlds Fair. The Museums collection contains
an RCA TRK-12 receiver from this period in which the tube is vertical and the image is reflected
in a mirror for viewing (710663). Our example was used by the National Research Council of Canada
for wartime radar research.
|RCA TRK-12 receiver (710663), introduced at New York Worlds Fair, 1939. (CSTM)|
In 1941 the United States government set the American broadcast standard at 525 lines and
30 pictures per second (where it remains today) but the Second World War halted commercial development.
Regular scheduled broadcasting began in the United States in 1947 and in Canada, using
the same standard, in 1952.
* The numbers in brackets are the accession numbers of artifacts held by the Museum.