GB403987A - Improvements in and relating to control of electric relays by means including electric discharge devices - Google Patents

Abstract

403,987. Valve circuits. BRITISH THOMSON - HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Cockrell, W. D. ; 1, Rugby Road, Schenectady, New York, U.S.A.) March 31, 1932, No. 9293. Convention date, March 31, 1931. [Class 40 (v).] A variable impedance 17, e.g. a photo-electric cell, controls the impedance of a valve 22 supplied with A.C. in whose anode circuit a reactance 23 displaces the phase of current variations with respect to the anode voltage and the displaced current is superposed on an A.C. bias voltage which normally renders an are discharge tube, also supplied with A.C., nonconducting. At a predetermined critical value of the impedance 17 the grid voltage of the device 1, when its anode voltage is at zero and rising positively with respect to the cathode, is rendered positive by the pulsating current from the condenser reactance 23 and associated potentiometer 10, so that the tube 1 trips and is made conducting throughout the positive half cycle so as to energise a relay 3 closing a local circuit 4. The tube 1 is therefore either fully conducting or fully non conducting according to the state of the impedance 17. The arrangement may be used to switch on or off street lighting in response to daylight or a predetermined intensity of daylight. Specification 319,286, [Class 40 (v), Wireless signalling &c.], is referred to.