GB486041A - Improvements in or relating to electrical time base circuits - Google Patents

Abstract

486,041. Valve generating circuits ; electron beam valves ; television. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., PLAISTOWE, D. L., and FEWINGS, D. J. Nov. 30, 1936, No. 32837. [Classes 39 (i), 40 (iii), and 40 (v)] An electron beam valve is used for discharging the condenser of a relaxation oscillator for generating saw-tooth voltage. Series condensers 13, 14 are slowly charged from a source 11, 19 through a variable resistance 12, and are rapidly discharged by an electron beam passing from the cathode 2 to the outer anode 7 of the beam valve 1. The cathode 2 and an apertured electrode 3 form an electron gun, the beam from which strikes the inner anode 5 whilst the condensers 13, 14 are being charged. When the desired voltage is attained a side electrode 9 connected to the anode 7 through a switch 15, 20 deflects the beam so that it reaches an aperture 6 in the inner anode 5 and passes therethrough to strike the outer anode 7, thus discharging the condensers 13, 14. As the beam leaves the anode 5, a positive pulse is applied from this anode to a second deflecting-plate 8 through a condenser 21, thus maintaining temporarily the deflection of the beam. As the beam returns, the starting of current to the anode 5 gives a negative pulse to the plate 8 and accelerates the return movement of the beam. External synchronizing pulses may be applied to a deflecting-plate 10 lying opposite the plates 8, 9. When the oscillator is not required to be selfoscillatory, the switch 20 may be thrown over to the contact 16 so that the plate 9 is maintained at a fixed voltage by a tapping 17, the action then being dependent on the receipt of a synchronizing signal on the plate 10. When. synchronizing signals are of opposite polarity to picture signals, both may be applied to the plate 10 without preliminary separation. Potentiometer tappings 22, 25 apply normal positive voltages to the plates 8, 10.