TV: A 20th-Century Epiphany
Some technologies take the world by surprise. Nobody knew
they needed a microwave oven, for instance, until they were on dealers' shelves. But
television was never like that: From the moment people started sending messages over long
distances by wire, and later by radio, it was generally assumed that someone would
eventually figure out how to send moving pictures that way. The word
"television" was coined long before it was a reality.
The problem the early developers had to face was how to
turn a parallel process into a sequential one. When we view an object, millions of sensors
in the back of our eyes react to it, and send their information to our brains
simultaneously. It would be theoretically possible to devise a television system that uses
numerous light sensors, each connected by its own circuit to a corresponding light emitter
in the receiver, but that would hardly be practical.
Instead, the transmitter has to be break up the image into
smaller areas, and "read" the amount of light each area reflects in a fixed
pattern. The transmitter then sends the sequence of changing voltage over a single
circuit, and the receiver reassembles it. For this to work, the transmitter must read a
large enough number of points of light for the image to be clear, and the process has to
repeat often enough for the movement to appear smooth, without the image flickering.
The process is called "scanning," and German
engineer Paul Nipkow proposed a method of accomplishing it as early as 1884. He suggested
a spinning disc with a spiral of small holes in it. As each hole passed the object, the
hole would trace a horizontal line across the object, exposing changes of light along that
line to a photosensitive device on the other side of the disc. The receiver would have a
similar disc, which would "paint" the image for the viewer.
A Scottish electrical engineer named John Logie Baird
actually made this work. In 1924, he was able to transmit the outlines of objects, then
recognizable faces. Within two years, he succeeded in producing moving images -- the first
true television pictures. Baird's original disc had 30 holes, which yielded a vertical
resolution of only 30 lines. Eventually he increased this to 240 lines, but in the end, an
all-electronic system was chosen for Britain.
The real father of television, at least in the UK, was Sir
Isaac Schoenberg, a radio expert from the Soviet Union. From 1931 on, he headed a research
effort to create a television system based on the Emitron camera tube and a cathode-ray
display. The first broadcasts using Schoenberg's standard went on the air in 1936; it
became the exclusive standard the next year when the BBC dropped Baird's mechanical
system, and remained so until the 1960s.
Crucial to that development was the cathode-ray picture
tube, the first practical commercial version of which Allen B. Du Mont had perfected in
the United States. Du Mont went on to be the first manufacturer of television sets in the
US in 1937, two years before TV broadcasting began.
The real push for television in North America came when
Vladimir K. Zworykin teamed up with RCA. Zworykin was born and educated in Russia but
immigrated to the United States after the First World War. He worked initially for
Westinghouse, where he developed the iconoscope -- the pickup tube used in all early TV
cameras -- and the kinescope, which is the basis of conventional television picture tubes
to this day. In 1929, some officials at RCA saw a demonstration of Zworykin's system and
hired him.
RCA's subsidiary, NBC, produced the first American
television broadcast at the New York World's Fair in 1939, and by the next year, almost
two dozen stations were on the air, serving some 10,000 viewers. But everything ground to
a halt, in both Britain and the US, when the Second World War came. The factories that
otherwise might make TV sets were occupied making military electronics, such as radar
sets.
Things picked up quickly after the war, however, and by
1946 both the BBC in the UK and the American stations were back on the air. In the US,
there were some 10 million sets in use by 1951, and 50 million by the end of the decade.
Similar growth occurred in Britain. Canadian television broadcasting began in September
1952 in Montreal and Toronto.
All of this activity was monochromatic, of course, but just
as television itself had been inevitable, so was color TV. In fact, both Baird and
Zworykin had developed color systems as far back as 1928.
Neither of those came to anything, but in 1940 Peter
Goldmark demonstrated a color technology that would briefly have official status after the
war. Goldmark was a Hungarian-born American engineer who would later gain renown as the
man behind the vinyl LP. His initial development was the first commercial color television
system, which used a spinning disc that contained three color filters. Each successive
frame would be filtered through one of these, and a corresponding filter would be in the
receiving set.
In the end, just as mechanical means had been rejected for
television itself, mechanical color was mostly a curiosity as well. Even as Goldmark's
disc was being demonstrated, an all-electronic alternative did exist. France's George
Valensi patented a system in 1938 that would form the basis for compatible color --
signals that, without modification, would reproduce properly on both color and
black-and-white sets.
By 1950, serious efforts were being made to find a color
system for North America, and the National Television System Committee (NTSC) -- an
industry body -- set itself the task of choosing a standard. By 1953, they had approved a
scheme developed by RCA, which was accepted by the American broadcast regulators that
year. It was called NTSC after the committee and has remained unchanged to this day.
Although the standard was established in the early 1950s, a
majority of US programming was not in color until the late 1960s. Other countries were
even slower off the mark. In Europe, for instance, two color systems emerged --
incompatible with each other and with NTSC -- but they weren't universally accepted until
the 1970s.
Telefunken developed the more common system in Germany, and
called it "phase alternating line" or PAL. It was based on the NTSC system but
with improved color stability. France adopted a system named SECAM (système électronique
couleur avec mémoire), which further enhanced color performance. Both were based on the
European standard of 625 scanning lines and 25 frames per second, rather than NTSC's 525
lines and 30 frames. North America and Japan use the NTSC system, while France and most of
the former Communist states of Eastern Europe use SECAM, and practically everybody else
uses PAL.
One remarkable aspect of television technology is that,
except for the addition of color, it hasn't changed in more than half a century. A set
bought in 1946 would work with today's signals. What has changed dramatically is the way
TV pictures are delivered. Cable TV has been around from the beginning, originally to
provide service to communities where distance or topography made reception difficult. It
took off in Canada in the 1960s as a means of delivering relatively noise-free color
pictures from US stations. Its progress south of the border was slower. It became a mass
item when specialty channels delivered only on cable -- movies and sports, mainly -- were
introduced. Cable now serves the majority of households in both countries.
The main competitor to cable is the direct-to-home (DTH)
digital satellite, which arrived in the US in 1994, and in Canada two years later. Able to
deliver more channels and better quality than conventional analog cable, DTH has prompted
the main cable systems to introduce digital versions of their premium signals.
The end is coming for this 60-plus-year-old technology, of
course, as digital television picks up steam around the world -- its first true upgrade
ever -- but the familiar TV systems have had a remarkable run.
...Ian G. Masters
ian@mastersonaudio.com
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