| 摘要 |
PURPOSE:To eliminate the ambiguous display of a display device by crosswise connecting preheating circuits and disabling the other discharge lamp to be lighted when one discharge lamp is disabled to be lighted. CONSTITUTION:When the filament F1 or a discharge lamp A is opened at the terminal stage of its life, even if a switch S1 is turned on after a power source is turned on, the passage of the preheating current flowing through a filament F4 is cut off by the opened filament F1. The discharge lamp A is not started and lighted, and also a discharge lamp B is not started and lighted. When any one of other filaments F2, F3, F4 is opened as well as the filament F1, no preheating current flows through the filament of the other discharge lamp, thus both discharge lamps are concurrently disabled to be started and lighted. When one of the discharge lamps A and B is removed, no preheating current flows through the filament of the other discharge lamp, thereby the other discharge lamp is not started and lighted. |
