Skip to main content
BFI logo











Screenonline banner
TV Technology 10. Roll VTR by Richard G. Elen


Ampex VR1200B quadruplex recorder

Ampex VR1200B quadruplex recorder, late 1960s

Curiously enough, the beginnings of video recording go back to the beginnings of television itself, and where television begins, John Logie Baird is sure not to be far away.

In 1926, the very year that Baird first publicly demonstrated television, he applied for a patent on a system for video recording, which he called 'Phonovision'. The patent (324049), granted in 1928, described a device called a 'Phonovisor', designed to replay Phonovision discs. Baird managed to record images on disc, but he never publicly demonstrated playback, no doubt because the quality of the 30-line images is even worse than they were when broadcast. However, with the aid of modern digital processing technology, author Don McLean, a researcher who is at pains to give Baird no less than the recognition he deserves, has recovered the content from all the existing Phonovision and other 30-line disc recordings and made them available on his web site ( and on CD-ROM.

Phonovision used what was essentially a modified standard 78-rpm cutting lathe. It was possible to use this to record the 30-line images because the bandwidth was in the audible range - in fact, Baird's 30-line transmissions were made on medium wave (AM) where the frequency response hardly exceeded a few kilohertz. Even so, Baird had to drop the frame rate from the broadcast 12.5 images per second down to just four to capture the images on disc (three frames per disc rotation at 78-rpm), which caused loss of greys. There are some other differences between Baird's recording system and his broadcast system, notably the fact that the 7:3 aspect ratio portrait-style image is scanned with 30 vertical lines from right to left on the air, but left to right in Phonovision.

Due to the anti-intuitive 'flying spot' scanning system that Baird used, where a scanning beam was emitted from a fixed 'camera' and light reflected from the scene was captured by banks of photocells that could be moved or crossfaded to change the 'lighting', Baird 30-line transmissions and recordings demonstrate quite strange illumination.

The extant Phonovision discs have clearly visible radial striations across the disc surface, which suggest that they contain sync information and show how the frames were synchronised to disc rotation.

By around 1930 there was at least one commercially-available disc system designed for home audio recording. This was the Silvatone system, sold by Cairns & Morrison for £4 12s. A microphone was provided and six blank single-sided aluminium discs that could be recorded upon, once only, with a steel needle - a fibre needle was used to play them back. Each disc had a running time of about 4 minutes. An enterprising owner of this system in Ealing, West London, used it to record 30-line television broadcasts off-air, using a medium wave receiver connected to the audio input of the recorder and no synchronisation information. One disc survives, of part of a programme - the first-ever television revue - called 'Looking In', featuring dancing by the Paramount Astoria Girls and broadcast on 21 April 1933.

In 1934, the first publicly available videodisc was released. Advertised in Television magazine and sold through Selfridges, the disc, by the 'Major Radiovision Company', was sold in quite large numbers. It was in fact a 10in, double-sided 78-rpm test disc with 11 cartoon-like test images and one test pattern, designed to help 'lookers in' to adjust their Televisors. Viewers would hook up their record player to the Televisor's audio input and presumably synchronise the images by hand, there being no sync signals on the disc. It has been suggested that you would use the test disc to 'warm up' your Televisor before broadcasts came on the air, then switch over to the medium wave receiver and adjust the set to gain a synchronised image instead of starting from scratch at the beginning of a broadcast.

Eleven additional private off-air disc recordings of television broadcasts (The 'Marcus Games discs') from the period 1932-35 also exist and have been restored by Mr McLean. Television programmes were not to be recorded directly again for another twenty years.

Near the end of WWII, British radio monitoring stations had been bemused to hear Hitler making speeches in several different cities sufficiently close together in time that he could hardly have made the journey himself, and they suspected recordings were being used, but they were audio recordings of a much higher quality than was generally believed possible from the disc recording systems of the time. As the Allies pushed across Germany, they discovered several sound recording machines using paper tape coated with a black iron oxide - magnetic tape - but their recording quality was limited. However, American soldiers were informed that a radio station in Frankfurt had rather different Magnetophon machines with an extra piece of electronics on them. On examination, it turned out that these were AC-biased machines that offered far higher quality than the previous DC-biased recorders ('biasing' is a method of making the tape work with lower distortion). It's generally believed that two of these machines, and tape to use on them, were brought to the US after the war by Jack Mullin. He demonstrated the recording system to singer Bing Crosby who, impressed, helped with funding and led to the setting up of the Ampex Corporation and the launch of its first audio recorder, the Model 200, which was first used on the air in 1948.

At this time, as it had been since the BBC's 405-line Television Service opened in 1936, apart from films, all television was live (and the expense of film made it unusual for the production of television programmes in the UK). If a programme was to be repeated, it required a second performance. There was a way of recording television images, but only by shooting a television monitor with a specially-modified synchronised, usually 35mm, film camera. The results from the 'kinescope', as this system was called, were considered by and large acceptable (although there were significant problems with the image quality) and the process reliable, but by the 1950s in the United States, where time-shifting across the continent was a way of life - a live network show broadcast to New York had to go out three hours later on the West coast - the 35mm kinescopes of the networks and their 16mm backups ate up more film in a year than the entire Hollywood film industry: NBC is estimated to have used over a million feet a month, and the costs were astronomical, including requiring extremely rapid processing turnarounds.

There was obviously a market for an alternative recording medium, and magnetic tape showed promise. But unlike the narrow-bandwidth Baird transmissions, a 405- or 525-line video signal needed much wider bandwidth than audio - as much as around four megahertz. To record higher frequencies required a higher tape-to-head speed - much higher. And while some systems tried to achieve this goal by simply running the tape faster, this initially meant that lower frequencies (which contribute to the rendering of greyscales) were not recorded as well. An early attempt at overcoming these obstacles was the BBC's VERA (Vision Electronic Recording Apparatus), designed by a team led by Dr Peter Axon, which, starting in 1952, offered broadcast-quality capability by 1958 when it was used on the air. VERA spun tape at 16 feet per second, offering just 15 minutes of recording time on a 21-inch reel. High frequencies (100 kHz-3MHz) were recorded on one track with AM, while low frequencies were frequency modulated on another. The unit included a number of other innovations such as a closed-loop drive mechanism locked to external sync. Another example of this 'longitudinal' recording approach was the machine that Jack Mullin produced for Crosby Enterprises, which multiplexed the signal across ten tracks on half-inch tape running at 120 in/s. The technology was subsequently acquired by 3M, who applied the concept to data instrumentation recording.

However, it became evident that longitudinal recording was not the way to go. Instead of running tape at high speed, the idea was put forward of moving the tape head past the tape at high speeds, putting the head on a disc or drum and spinning it across the tape while moving the tape forward, to create a transverse recording pattern. This needed multiple heads so that one head met the tape just before another left so a continuous signal could be reassembled - two or four were needed. The first attempt at this kind of recording used heads on a vertical disc spun alongside the tape, producing a pattern of adjacent arcs ('arctuate' recording). A better approach was developed by a 6-man team at Ampex, including the now-famous Ray Dolby, in the form of what ultimately became known as the 'quad' or quadruplex recorder, where four heads on a drum at right angles to the tape were spun against it to produce almost straight transverse paths on the tape.

By the mid-1950s, the Ampex team was still bedevilled by problems, and switched from AM to FM recording with immediate improvements. Results were shown to management in early 1955 and although the resolution was still only 1.5MHz or so, the team under Charles Ginsburg was given the go-ahead. A year later, in February 1956, a demonstration was held using what was their Mark III machine, and the team received a standing ovation. It was shown to major broadcasters and a Mark IV was built to show at the upcoming Chicago broadcaster's convention. The machine was unveiled on 14 April 1956 at a CBS affiliates meeting the day before the show opened. Manager William Lodge delivered the annual report, his speech visible live around the room on a number of video monitors. As soon as it had finished, the Ampex team rewound and replayed the tape they had just made back via the same monitors, to the astonishment of attendees. The word spread and the Ampex booth at the Convention was crowded. Many orders were taken - but the prototype machines then had to be developed into production products that could be sold to meet those orders.

The first on-air use of the machines was on CBS on 30 November 1956, when the news was recorded on the west coast for rebroadcast, but for the first month the network ran kinescopes as a backup. Initial problems were ironed out and production of the new VR-1000 began the following year. Also that year, RCA's TRT-1A was unveiled, using the same recording system, RCA referring to the process as 'quadruplex' recording for the first time because of the four heads. The first machines cost around $50,000 and tape was $300 per one-hour reel - much cheaper than kinescope recording and not nearly as fraught. Colour recording followed in the early 1960s.

By the late 1950s, VTRs were being used regularly for time-shifting purposes, but as far as the recording of programmes on videotape was concerned, the problem was the lack of a simple editing capability. Although the first totally video-recorded show went out on CBS in 1958, programmes were primarily 'recorded as live'. Physical editing and splicing was possible, but only by 'developing' the magnetic pattern on the tape and cutting between TV frames. Early recorders added edit pulses to the control track on the tape to make these points more obvious. Even so, half a second of audio was lost at the edit point, requiring laying the audio back from a second machine. One technique was to edit a film copy made with a kinescope and then conform the video recording to it - early off-line editing. Editing with timecode was introduced in 1967 while the first computerised editing systems began to appear in the early 1970s.

Meanwhile, another recording technique had been invented, this time wrapping the tape most of the way around a large drum, the drum containing heads that rotated against the tape to produce a helical scan - an approach that eventually became dominant. This technique led to the first consumer video recorders, such as the Philips semi-pro EL3400 open reel recorder (1964) and the development of smaller and lighter recorders, such as the Sony 'Portapak', that could be used in the field. Then came the first cassette-based recorders with the introduction of Sony's popular 3/4in U-Matic recorder in 1971 (designed for home use but finding its true niche in the corporate and educational fields, and ultimately some broadcast applications), and the Philips N1500 consumer 'VCR' or videocassette recorder, introduced in 1973, which was capable of extremely good quality recordings on a one-hour VC60 cassette. Later versions reduced the tape speed and thus increased the recording time. Sony's consumer Betamax format arrived in 1975 and the technically inferior JVC VHS system a year later. But Sony was trapped in a court battle with Hollywood that gave VHS an unassailable edge.

At the broadcast end of the chain, quad machines persisted until around 1978, with the introduction, once more by Ampex, of Type C, 1in open reel recorders. Broadcast-quality camcorders became possible in the early 1980s, with CCD imaging devices and recording systems that instead of recording colour subcarriers (which were badly handled by helical scan systems) recorded full-bandwidth luminance (the black and white signal) on one track plus two bandwidth-limited FM colour difference signals on another, allowing tiny helical-scan recorders.

The next fundamental revolution was the introduction of D1 digital video recorders in 1986-87. High prices kept these out of all but the most well-heeled facilities until more affordable digital systems began to appear in the mid-1990s. Today, there is a proliferation of digital TV technologies, and the ability to store and edit digital video on modern computer-based systems has led to the introduction of video servers and other non-tape-based methods of working on and distributing television programmes.

Sources include:

Related Articles

Seeing by Wireless

Baird and the early experiments with television

Television on the Air

Baird and the BBC in uneasy alliance

High Definition

Baird v. Marconi-EMI: the rivals line up

Here's Looking at You

The BBC begins test transmissions

Magic Rays of Light

The new BBC Television Service greets its small audience

The 'Color War'

US television points the way to the colour future

An Independent Air

The beginning of the multi-channel age

Britain in Colour - and UHF

1960s technological revolutions

The Digital Age

Digital broadcasting via cable, satellite and terrestrial

Roll VTR

Broadcast video recording from Phonovision to DigiBeta