Patent GB-368309-A (GB)
Title: Television apparatus and process
IPC: H01J31/42
Filed: 1930-08-27
Abstract: 368,309. Television. TRIGGS, W. W., 57, Lincoln's Inn Fields, London. - (Television Laboratories, Inc. ; 202, Green Street, San Francisco, U.S.A.) Aug. 27, 1930, No. 25604. [Classes 39 (i), 40 (iii), and 40 (v).] An image of an object 2, Fig. 1, is projected on a photo-electric surface 6 producing an electron stream whose density varies with the light and shade of the image, and oscillations of straight line wave form are applied to condenser plates 13 .. 16, or solenoids, to traverse the electron stream over an electrode 10 producing an energy train varying according to the intensity of light of elementary areas of the image. At the receiver the energy train is converted into light and preferably distributed over a screen by means of straight line wave form oscillations. Producing straight line wave form oscillations. A valve 20, Fig. 1, has a grid leak 21, a choke 25<1> and a battery 26<1> connecting its plate and filament and a condenser 281 and inductance 27 connecting its grid and plate, the inductance being shunted by condensers 28, 29 in series. This circuit produces oscillations of a frequency of say 10, as in Fig. 5, which are applied to the plate of a valve 32 oscillating at a frequency such as 500 kilocycles. The valve 32 generates oscillations when its plate voltage is positive and since the voltage of the first oscillator is above the value required for maximum plate current the current generated by the valve 32 will be as in Fig. 6. These oscillations are fed to the grid of a valve 48 through a transformer 51 and a grid leak 50. The valve 48, owing to the grid leak 50, accumulates a charge during the passage of each wave train of Fig. 6, which leaks off during the interval between successive trains so as to produce a straight line wave form oscillation as in Fig. 7. A similar oscillator comprising valves 20a, 32a, 48a produces similar oscillations of a higher frequency such as 5000, and the two oscillations are applied to the pairs of deflecting condenser plates 15, 16 and 13, 14 respectively. A valve 59 modulates the lower frequency upon the high frequency oscillation. Transmission. The circuit through the photo-electric cell formed by the plate 6 and the electrode 10, includes a battery 67 and a resistance 69. The varying potential across the resistance 69 is applied to a valve 72 which amplifies the image currents and modulates a first carrier frequency of about 500 kilo-cycles generated by a valve 73. The resulting potential is applied to a valve 94 and modulates a second carrier frequency of about 1500 kilocycles, produced by an oscillator 95. This carrier wave is also modulated by the deflecting potentials from the valve 59 through a resistance 58a and the valve 94 and is transmitted from an aerial 117. Reception. The received signals are rectified by a valve 159, Fig. 2, and are applied to inductances 162, 169. The inductance 162 passes the first carrier frequency to a detector 164 and the picture signals are applied to the control grid 123 of a cathode ray tube 120. The inductance 169 passes the deflecting signals to a detector 173 which produces a low frequency oscillation applied to the deflecting coils 125, 126. The remaining portion of the received signals is applied directly to the deflecting coils 127. Photo-electric cells. The photo-electric cell comprises a photo-electric plate 8, Fig 3, an apertured anode 11 and a subsidiary anode 10. A further embodiment comprises a casing 220, Fig. 9, with a plane window 221, a photoelectric plate cathode 222 and an anode screen 223. Electrons emitted from the cathode pass through the anode 223 into an equipotential space formed by an earthed cylindrical shield 223<1> to an anode 226 within a tube 224 apertured at 225. This cell may be mounted within a solenoid to accelerate the electrons, and the electron stream is preferably traversed by the magnetic fields from solenoids. The tube 224 and the screen 223 being out of the focal plane, do not produce shadows upon the cathode 222.