Abstract
It was recognized in the early days of television that a modified form of cathode-ray oscillograph might be used as a transmitting device, the electron beam serving as a means for exploring rapidly the image to be transmitted. A. A. Campbell Swinton(1) was amongst those who foresaw this future use of the cathode-ray tube and he attempted, though unsuccessfully, to produce a transmitting tube by replacing the fluorescent screen by a layer of light-sensitive selenium(2). Several variations have been suggested in patents(3) but no successful television transmitter using the photoconductive effect has appeared. The present paper describes some investigations into this method of producing picture signals, in which a number of light-sensitive materials were examined.* During its preparation two accounts have appeared in which the same method of signal-production has been investigated and results of a similar nature have been observed(4, 5).