GB816451A - Electrical stand-by unit arrangement for signal-radiating devices - Google Patents

Abstract

816,451. Switching systems for flashing lamp apparatus. SVENSKA AKTIEBOLAGET GASACCUMULATOR. May 30,1956 [June 3, 1955], No. 16731/56. Class 38 (4). [Also in Groups XXXVIII, XXXIX and XL (c)] A circuit for operating a flashing lamp 1 (see Group XL (c)) comprises a saturable reactor 22 connected in series with an alternating current supply and the lamp, the control windings of the reactor being connected in the collector circuit of a transistor 28. The lamp circuit also includes the primary winding of a feedback transformer 25, the voltage at 'the secondary winding of which is applied through a rectifier network 26 and a condenser resistance circuit 27, 29 to the base of the transistor. Due to the feedback circuit the transistor alternates between conductive and non-conductive states at a period dependent upon the time constant of capacitor 27 and resistor 29. The reactor is accordingly periodically saturated so that the lamp is caused to flash. The circuit may be arranged in an apparatus together with a similar circuit, each of which derives from a condenser smoothing circuit 30, 31 a blocking voltage which is applied to the other circuit so that when one is operating the other is blocked. On the occurrence of a failure of the working unit the stand-by unit is unblocked and commences to operate causing the previously working unit to be blocked. Alternative circuits are also described in which a transistor is used in the feedback circuit instead of a saturable reactor and either D.C. or A.C. supplies are provided.