Definição do conceito
[ENG] Philips-Miller | The Philips-Miller Film Recorder | One of the methods developed in the 1920s for recording audio for movies was the variable area optical sound track. Photographic film stock was exposed to light modulated by the signal to be recorded. When a positive was printed the result was a clear area of varying width. The photo actually shows a piece of film recorded by the Philips-Miller, apparently a recording of a constant frequency. Playback is achieved by projecting a narrow slit of light onto the film and detecting the amount of light passing through using a photo-electric cell. A recording method like that used for cinema films, which required time for the photographic film to be processed before the recording could be played, would not have been suitable for broadcast use. Instead of using the optical/chemical method the Philips-Miller machine recorded mechanically. | The cutterThe film was 7mm wide, 0.18mm thick and consisted of three layers. The celluloid base was coated with a layer of gelatine on which was applied a very thin opaque coating of mercuric sulphide. A sapphire cutter with an obtuse tip angle (174 degrees) moved vertically, cutting through the opaque layer into the gelatine. The deeper it cut the wider was the amount removed from the opaque layer. The resulting recording was played optically, just like a cinema film. | Some early experimenters had attempted to record on film using lateral cuts, but it was J. A. Miller of Flushing, N.Y. who developed the vertical cut idea in 1931. The following year he reached an agreement with the Philips research laboratory at Eindhoven on the use of his patents and further development work. | Philips provided some experimental equipment for the BBC to test in November 1934 and a preliminary quotation was made the following January. The equipment was priced at £4500 and the running costs would have been £20 per hour. In February 1936, and after some negotiating, a six month trial of a machine at Maida Vale was agreed. For this the BBC would pay £1,000. The initial film width of 17mm was reduced to 7mm which helped get the running costs down to £7 per hour.Tests conducted at Eindhoven were very encouraging. The performance figures included a frequency response of +/-2.5dB between 50Hz and 7kHz, total distortion of 3.5% at 30% modulation at 1kHz and noise at least 50dB below full modulation. The equipment was installed in Room 21, Maida Vale and formally handed over on 1 June 1936. | SOURCE : OLD BBC RADIO BROADCASTING EQUIPEMENT AND MEMORIES - ORBEM Available at : http://www.orbem.co.uk/tapes/pm.htm Accessed : 26 nov. 2022
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