| 摘要 |
PURPOSE:To instantaneously cope with the trouble of a ball tap and to prevent the overflow of water from a water receiving tank, by controlling the water level so that a solenoid valve is closed and opened when the water level is higher and lower than a higher electrode and a lower electrode for control of the solenoid valve respectively. CONSTITUTION:A solenoid valve control circuit 8E in a liquid level control circuit 8' starts the opening drive of a constantly open type solenoid valve 12 when the area between a common electrode 6A and a solenoid controlling higher electrode 6F is changed to a conductive state from an open state by water. Then the closing drive of the valve 12 is stopped when the area between both electrodes 6A and 6E is switched to an open state from a conductive state by water. Thus it is possible to prevent the overflow of water from a water receiving tank 1 when a ball tap 2 has a trouble. In addition, a full-water pilot lamp 9D for the tank 1 is kept turned on and a buzzer 10 is actuated while the valve 12 is kept closed.
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