| 摘要 |
PURPOSE:To secure synthetic safety of gas supplying by a method wherein a shut-off valve is closed automatically by transmitting the flowing of electric current to a valve driving unit through a resistance when the power source voltage of a micro-computer decreases abnormally, or when an abnormal consumed electric current flows to the micro-computer. CONSTITUTION:In case the micro-computer 5 is under a normal condition, the current flowing into the point (a) of a back-up resistance 8 is small and the voltage of the back-up resistance 8 hardly drops, and the voltage thereof is almost same as the voltage of a capacitor 6. However, the micro-computer becomes abnormal due to noise and aging stress or the like for example and the electric current thereof increases; as a result, the voltage drop of the back-up resistance 8 becomes large and the potential at the point (a) decreases. Then, the base potential of a transistor 12 drops through a resistance 14 to put ON the transistor 12 and the shut-off valve may be operated. |
