DIRECT TELEVISION from ALEXANDRA PALACE by Arthur Dungate . Philips-Miller recording system

BBC Engineering 1922-1972 by Edward Pawley, Ch 3.9 p191-2 --

... A new kind of film recording developed by Philips, which had the great advantage that the recording could be played back immediately without any processing. This was the Philips-Miller system. A variable-width track was cut with a sapphire in a thin opaque layer on the film, the recording being reproduced by means of a photo-electric cell, in the same way as a variable-area photographic track. The film was coated with a layer of gelatine to which was applied a fine skin, about three microns thick, of black mercuric sulphide, The cutter was V-shaped, the apex angle being 174°.

The modulation thus appeared as a symmetrical push-pull* transparent track down the centre of the opaque film. Each equipment consisted of two combined recording and reproducing machines placed side by side in a single unit to form a complete channel capable of continuous recording and reproduction.

... In 1931 J. A. Miller of Flushing, NY, devised the Millerfilm system, which was the basis of the Philips-Miller equipment. Miller used a cutter that moved vertically instead of laterally, so that it produced a variable-width track by removing the black surface so as to leave a transparent track. By making the cutter in the form of a wedge with an obtuse angle, a considerable amount of mechanical amplification was achieved and this proved to be the secret of the success of Miller’s system.

The film ran at 32cm/s. The overall amplitude-frequency characteristic: within ± 2.5 dB between 50 and 7000 Hz and within ± 6 dB between 30 and 8000 Hz with reference to the amplitude at 1000 Hz. Total distortion at 30 per cent modulation: 32 per cent at 60 Hz, 3.5 per cent at 1000 Hz, and 6.0 per cent at 4000 Hz. Noise: at least 50 dB below the output level at full modulation.