GB576685A - Improvements in means for producing flashes of light - Google Patents

Abstract

576,685. Electric supply to discharge lamps. GENERAL ELECTRIC CO., Ltd., FRANCIS, V. J., and THOMAS, E. R. March 17, 1939, No. 8546. Addition to 508,241. [Class 38 (iv)] Relates to means for producing flashes of light for signalling and other purposes by the over-energization of a high-pressure metalvapour discharge lamp which is connected in a circuit adapted to supply (1) a heavy " marking " current; (2) a small " spacing " current and (3) an intermediate " resting " current to ensure that the lamp discharge is maintained as described in the parent Specification. According to the invention, the small spacing current is supplied from a subsidiary supply of higher voltage than the main supply, for example, from a step-up stray field transformer fed from the normal supply, as described in Specification 493,634. As shown in Fig. 1, the lamp 1 is supplied from the A.C. source 9 in conjunction with the transformer 10, 11 through the signalling key 12 and the " resting " switch 17. With the key 12 in the neutral position, the switch 17 (which may be interlocked with the key) bridges contacts 18, 19 and the lamp is supplied with " resting " current from the source 9 through the chokes 6, 7. For the heavy current supply, the key 12 connects contacts 13, 14 and the switch the contacts 20, 21 so that the choke 7 is shortcircuited. For the small current supply, the contacts 15, 16 are interconnected so that the lamp is connected across the secondary 11 of the leakage transformer. In another arrangement, the secondary is always connected across the lamp.