| 摘要 |
PURPOSE:To switch a switch periodically and inverting the polarity of a power source and to prolong the life of a filament lamp by providing a switch circuit which inverts the polarity of a power source supplying electric power to the filament lamp of an eraser. CONSTITUTION:The GND-polarity output of the DC power source 1 is connected to a common terminal C1 of the twin two-contact switch 2 and the plus-polarity output is connected to a common terminal C2. Terminals L2 and R2 of the switch 2 are connected to a terminal (b) of the filament lamp 3 and terminals L2 and R1 are connected to a terminal (a) of the switch 3. When the switch 2 is placed on the side L, the plus polarity of the DC power source 1 is connected to the terminal (a) of the lamp 3 and the GND polarity is connected to the terminal (b), so that the current flows from the terminal (a) of the lamp 3 to the terminal (b). When the switch 2 is placed on the side R, on the other hand, the GND polarity is connected to the terminal (a) of the lamp 3 and the plus polarity is connected to the terminal (b), so that the current flows from the terminal (b) of the lamp 3 to the terminal (a). Thus, the switch 2 is placed on the side L or R to change the current direction of the lamp 3 optionally. The switch 2 is switched periodically. |
