| 摘要 |
A portable fluorescent lamp arrangement operated from a low voltage source by a D.C. to A.C. blocking oscillator inverter has switching means by which either one low-voltage tube, or two low-voltage tubes, can be used to give different levels of illumination. Difficulties in using a blocking oscillator inverter have been overcome by connecting one filament of one tube in series with the feedback winding of the oscillator whereby this filament is preheated by the collector current, and arranging the switching means so that 1. WHEN ONE TUBE ONLY IS TO BE ENERGISED THE SECONDARY WINDING IS CONNECTED ACROSS THE SAID PREHEATED FILAMENT AND THE OTHER FILAMENT OF THAT TUBE, AND 2. WHEN BOTH TUBES ARE TO BE ENERGISED THE ENDS OF THE SECONDARY WINDING ARE CONNECTED ONE TO THE NON-PREHEATED FILAMENT OF THE SAID ONE TUBE, AND THE OTHER END OF THE WINDING TO ONE FILAMENT OF THE SECOND TUBE, THERE BEING A SERIES PATH FOR THE LIGHTING CURRENT THROUGH BOTH TUBES.
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