. The Bell System technical journal. Telecommunication; Electric engineering; Communication; Electronics; Science; Technology. THE CATHODE RAY OSCILLOGRAPH 17 of the tube. In the 224 tube, with argon at the pressure of .01 mm. the focusing occurs at about 20 microamperes in the beam. Less cur- rent makes a large unfocused spot; more current produces a focus before the screen is reached, with consequent spreading of the spot again. Hence it is that the spot on the fluorescent screen is focused by adjusting the heating current of the Fig. 21—General Electric, ; Besides focusi
. The Bell System technical journal. Telecommunication; Electric engineering; Communication; Electronics; Science; Technology. THE CATHODE RAY OSCILLOGRAPH 17 of the tube. In the 224 tube, with argon at the pressure of .01 mm. the focusing occurs at about 20 microamperes in the beam. Less cur- rent makes a large unfocused spot; more current produces a focus before the screen is reached, with consequent spreading of the spot again. Hence it is that the spot on the fluorescent screen is focused by adjusting the heating current of the Fig. 21—General Electric, ; Besides focusing the electrons and preventing the accumulation of charges in the tube, the gas plays various other roles. One very curious effect of the gas is that it decreases the sensitivity of the tube at small deflecting voltages. When uniformly varying voltage is ap- plied to a pair of deflector plates so as to move the spot across the screen, the spot seems to hesitate for an instant at the centre of the screen, appearing to be brighter there. The effect has always been observed but particular attention has recently been given to it by Professor Bedell.^o The explanation has to do with space charge be- " Lee, E. S., G. E. Rev., 31, p. 404, 1928. 20 Bedell, F. & Kuhn, J., Phys. Rev. 36, p. 993, Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original American Telephone and Telegraph Company. [Short Hills, N. J. , etc. , American Telephone and Telegraph Co. ]
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