I.M.R.C.- Duo-trac.

Some time ago the International Marine Radio Company, in collaboration with British Ozaphane, set out to devise a system of recorded sound reproduction for use in ships; this has now made its appearance as the I.M.R.C.- Duo-trac.

The system is one of sound-on-film recording, but whereas on ordinary sound-track film the photographic image is carried in an emulsion spread over a film base of celluloid or other material, on the I.M.R.C.- Duo-trac sound film the image is actually dyed straight into the Ozaphane ribbon, and therefore cannot become worn or blurred.

The film, only an eighth of an inch wide, carries two parallel soundtracks. The track, with its varying black and white shapes, passes in front of a powerful lamp so that continually varying areas of light pass through the track and play upon a light-sensitive photo-electric cell which translates the light back into electrical impulses. Half of a recording is carried on each of the two parallel soundtracks, the upper track being played in the forward direction, and when the end of the film is reached the ribbon automatically reverses, the beam of light is re-focused on to the lower track, which is then played in the reverse direction without any human intervention.

The instrument, which was installed and demonstrated on board the S.S. Erin, of the Standard Fruit Steamship Co., lying in the Royal Albert Dock, incorporated a Scott-Phantom receiver.

Various modifications of the standard British Ozaphane Duotrac reproducer were necessary. Metal parts had to be treated to withstand the effects of the sea air, and a mercury switch, which normally operates the reversing of the sound reels, had to be replaced by a micro-relay switch as every roll of the ship reversed the record!

Some of the advantages for marine use of the I.M.R.C.- Duo-trac system are its freedom from surface noise, as there is no emulsion used; the recordings do not deteriorate after countless playings, they are non-inflammable and, above all the playing of the record is un-affected by the motion of the ship.

Here you find 4 models, 2 with images and 0 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.
All listed radios etc. from Duo Trac Cell-o-phone (Brand), British Ozaphane Ltd.; London