GB526848A - Improvements in and relating to electric control systems - Google Patents

Abstract

526,848. Thermionic valves; electron multipliers. BRITISH THOMSON-HOUSTON CO., Ltd. March 27, 1939, No. 9510. Convention date, March 26, 1938. [Class 39 (i)] A device whereby a load circuit is energized by means of an electron current, but is cut off when the current falls below a certain value and needs to be specially restarted if the current increases again comprises an emissive cathode, a secondarily emissive electrode and an anode, the cathode and the electrode being connected through a resistance, so that if the emission from the cathode falls below a certain value the potential differences between the cathode and secondary electrode is too small for effective secondary emission. Fig. 2 shows a photoelectric cathode 10 connected to a secondary electrode 11 through a resistance 18 and to a grid-like anode 13 through a battery 14 and load circuit 15. A control grid 17 is also connected to the electrode 11. If the emission from the cathode 10 falls below a certain value the current through the resistance 18 is too small to permit of a sufficient potential difference between the cathode 10 and electrode 11 to permit of appreciable secondary emission, the grid 17 also hindering primary electrons from reaching the electrode 11. A thermionic cathode may be substituted for the electrode 10 and the electron flow controlled by a grid.