1,000,000 Years B.C. (Before Cassette) |
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Television began in the 1930s, though UK
broadcasts were
suspended during World War II. It boomed in the 1950s,
and there was soon an urgent need to find some way of
recording television programs - particularly in the
United States, where the country spanned several
time-zones, and the evening news in New York would be
received in the mid-afternoon in California. The first solution was TeleCine, pointing a film camera at a TV monitor and filming the picture directly. But this was slow (since the film had to be developed) poor quality, and prone to distortion. Magnetic tape recording was an obvious solution, but the high-bandwidth signals used by television requires a very high head-to-tape speed; the first machines needed to have tape speeds measured in metres per second - the equivalent of 150 kph (90 mph), in one case. This was clearly impractical (and dangerous!), but Ampex solved the problem in 1956 with the Quadruplex format, which mounted the recording heads on a spinning disc so that they passed at high speed across the width of the slow-moving tape, writing short tracks across it rather than one long track along it:
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As each of the four heads reached the bottom of the tape, the next one was ready to start at the top. The heads each wrote 1/10 of a frame (about 52 lines, for a PAL machine), but since the heads had to be switched during a picture, head matching and alignment was critical to avoid disturbance on the image. The famous "Normal service will be resumed as soon as possible" message often covered some frantic head-cleaning and re-alignment of these notoriously finicky machines.
This approach was later developed into the helical scanning system, where two heads are mounted on a spinning drum, so that they each write a whole field at a shallow angle to the tape. This was more practical as it required much less precise alignment, and the head-switch occurred between fields. | ![]() |
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It also allowed a still-frame to be
produced, as the same field could be read reapeatedly
when the tape was stopped. Helical scanning made small VTRs practical, and throughout the 60's they became popular for all manner of presentation, security and training uses. A typical reel-to-reel helical VTR from the late sixties. The tape had to be laced by hand, around the various guides, rollers and the large head drum in the centre. |
By the end of the decade a standard had emerged, EIAJ, which meant that most (though not all) VTRs were compatible, and cassette and cartridge loading systems helped to avoid the complexity and potential tape-damage of manual lacing.
But these machines were more at home in a small studio than the home, and required some technical knowledge to own and run . A true home video system was elusive, and the few attempts made to market one at this time - such as the linear Wesgrove system sold as a kit in 1962 - failed to make any significant impact.
Background articles:
Below are some background displays, covering the technology behind television, broadcasting and magnetic recording. These are not strictly part of the story of home video, but are relevant because they define the problems which had to be overcome in order to produce a workable video recorder.
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