GB497457A - Improvements in and relating to electric discharge devices - Google Patents

Abstract

497,457. Discharge apparatus ; valve circuits. BRITISH THOMSON-HOUSTON CO., Ltd. Sept. 17, 1937, No. 25305. Convention date, Sept. 18, 1936. [Classes 39 (i) and 40 (v)] In light - sensitive relay apparatus, a photo - electric control electrode 3 connected to the incandescent or other cathode 1 through a potential source 5 and high resistance 4 receives primary electrons from the cathode 1 and emits secondary electrons to the anode 2. The voltage of the source 5 is so adjusted that the discharge is stable when the illumination is below a predetermined amount and becomes unstable when this amount is exceeded, giving a sudden large increase in secondary emission from the electrode 3, and so in the anode current, to operate a relay &c. in the circuit 6. Grids 7, 8 may be provided and the device may be adjusted to respond at different illuminations by varying the primary electron current, this being effected by grid control or by control of the cathode heating current. The sudden increase in current when the relay operates temporarily interrupts or decreases the primary electron current to restore the device to its initial, stable condition. The electrons flowing to the electrode 3 may be produced by an electron multiplier ; this is adjusted by detuning means and has a final amplification independent of the initial emission which may be produced by light scattered from the electrode 3. The apparatus may be placed at the focal point of a concave mirror or behind a wide-apertured lens. Specification 333,548, [Class 39 (i)], is referred to.