GB828783A - Improvements in or relating to circuit arrangements for operating electric lamps - Google Patents

Abstract

828,783. Dimming lamps. GENERAL ELECTRIC CO. Ltd. Aug. 13, 1958 [Aug. 29, 1957], No. 27295/57. Class 38 (4). In an electric circuit arrangement for varying the brightness of one or more electric lamps comprising reverse-parallel thyratrons in series with an A.C. supply, an electronic pulse-forming circuit is arranged to control the thyratrons by means of alternate positive and negative voltage pulses the timing of which may be adjusted with respect to the phase of the supply voltage. The capacitor 14 is charged and discharged in a cyclic manner by the variable resistors 15, 22 under the control of the valve 23 and the relay 24. The triangular voltage thus obtained is amplified by the valve 25 and fed to the non-linear resistor 26 which together with the capacitor 28 forms a phase-shift circuit. The value of the resistor 26 varies in accordance with the triangular wave voltage and hence varies the phase of a current supplied from the transformer secondary 13. A corresponding phase varying voltage is fed via the transformer T2 to the cathodecoupled multivibrator 34, 35, an output of which is differentiated. The sharp pulses so formed are amplified in the valve 43 and passed to the thyratron control grids, each being connected to its own winding 49 or 50 of the transformer T3. Additional switching means may be used to interchange lamps connected to the dimming circuit with other lamps on full or zero brightness so as to give a sequence of lamps of various colours. Specification 828,784 is referred to.