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May, 1933]
TELEVISION OUT OF DOORS
439
TELEVISION TRANSMISSION BY FILM
A description of the apparatus as actually operated at the Radio Exposition in Berlin follows:
Fig. 1 gives the general arrangement of the apparatus represented in the photograph. The film used for taking the scene is contained in the magazine, 1, and enters by a light-tight passage into a camera of a current model. The exposed film passes by a covered passage (with or without means of guiding) into a light-tight cabinet, 3, containing the photographic solutions.
Once the film is developed and fixed, it passes into the television scanning apparatus, 5. Then the film is rolled up on the drum, 6. In Fig. 1, the film is indicated by 4. The variations of potential effected in a photoelectric cell by the variations of brightness are amplified in the usual manner by the amplifier, 8, and sent by the transmitter, 9.
The possibility of the practical operation of the entire process
3
4
5
J
FIG. 1.
Diagram of the television transmitter employing an intermediate film (Fernsehen, 1932, No. 3).
depends upon the minimum time necessary for the photographic processing. Assuming that 25 images per second are employed, and that the height of each image is 18 millimeters (standard film), a rate of motion of 0.45 meter per second is required for the film. If the photographic processing requires, for example, 3 minutes, it is necessary to pass into the cabinet, 3, 81 meters of film before getting any results, which is a great disadvantage especially if the apparatus is to be portable. Even the use of a film of reduced dimensions hardly simplifies the problem.
From these considerations and to render the process practicable, it follows that it is necessary to reduce considerably the time necessary to develop and, above all, to fix the film. The attempts in this direction have been made in close collaboration with the motion picture section of the Zeiss Ikon A. G., Berlin-Zellendorf.