Abstract
ON May 15 a demonstration of the use of the cathode ray tube in television reception was given before the Electrical Association for Women at the showrooms of the Edison Swan Electric Co. Ltd., London. After a very clear and non-technical exposition of the basic principles had been given, the B.B.C. 30-line transmission was received. The results obtained suggested that the cathode ray tube is capable of giving as good an image as the limitations of the transmission will permit. There was very little flicker, owing to the large afterglow of the fluorescent material of the screen. The latter was of the usual type giving a green image; the use of white fluorescent screens is not considered desirable at the low picture frequency at present in use, as the afterglow with these is much less. The scanning is accomplished by means of two small oscillators giving voltages of saw-tooth wave-form and appropriate frequencies which are applied to the two pairs of deflecting plates; the incoming signals hold these oscillators in synchronism with the transmitter and also modulate the intensity of the electron beam. Difficulty was experienced in keeping the picture steady during the demonstration, but this was attributable to the exceptionally bad local reception conditions. It was stated that in normal circumstances the controls need not be touched during the whole transmission period of half an hour. The advantages claimed for the cathode ray tube are that it is noiseless, that signals of good headphone strength only are required to operate it, and that by the alteration of a few minor circuit components it can be easily adapted to suit transmissions of different numbers of lines and picture ratios. The last point is important in view of the uncertainty in the future Development of television. Suitable tubes can now be marketed at six guineas and this price could be substantially reduced if the demand became large enough. As the auxiliary apparatus required is not excessive, and can be assembled from standard components, the system is quite practicable for domestic use.
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Demonstration of Television. Nature 133, 789–790 (1934). https://doi.org/10.1038/133789d0
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DOI: https://doi.org/10.1038/133789d0