Technikatörténeti szemle 20. (1993)

TANULMÁNYOK - Tihanyi Glass, Katalin: The Iconoscope: Kalman Tihanyi and the Development of Modern Television

Swinton, the first proposal suggesting the use of cathode ray tubes at both the transmitting and receiving side, thus what is commonly thought of as ..electronic" television: ..DISTANT ELECTRIC VISION Referring to Mr. Shelford Bidwell's illuminating communication on this subject published in Nature on June 4, may I point out that though, as stated by Mr. Bidwell, it is wildly impracticable to effect even 160,000 synchronized operations per second by ordinary mechanical means, this part of the problem of obtaining distant electric vision can probably be solved by the employment of two beams of kathode rays (one at the transmitting and one at the receiving station) synchronously deflected by the varying fields of two electromagnets placed at right angles to one another and energized by two alternating electric currents of widely different frequencies, so that the moving extremities of the two beams are caused to sweep synchronously over the whole of the required surfaces within the one-tenth of a second necessary to take advantage of visual persistence. Indeed, as far as the receiving apparatus is concerned, the moving kathode beam has only to be arranged to impinge on a sufficiently sensitive fluorescent screen, and given suitable variations in its Intensity, to obtain the desired results. The real difficulties lie In devising an efficient transmitter which, under the influence of light and shade, shall sufficiently vary the transmitted electric current so as to produce the necessary alterations in the intensity of the cathode beam of the receiver, and further in making this transmitter sufficiently rapid in its action to respond to the 160,000 variations per second that are necessary as a minimum. Possibly no photoelectric phenomenon at present known will provide what is required In this respect, but should something suitable be discovered, distant electric vision will, I think, come within the region of possibility." On December 7, 1911, A.A. Campbell Swinton returned to the subject in an article published, again, in Nature (22). This time, he gave a detailed description of the all-electronic television system he had in mind, specifying two Crookes tubes filled with gas or sodium vapor which, it had been proven, would conduct the negative electrons discharged by the photosensitive layer of the screen under the