| 摘要 |
PROBLEM TO BE SOLVED: To prevent an erroneous operation of a shut-off magnetic detecting means and a reset magnetic detecting means by arranging a magnetic shut-off means made of a soft magnetic material between the shut-off magnetic detecting means for outputting a shut-off signal to a shut-off valve according to a magnetic field change and the reset magnetic detecting means for outputting a reset signal according to another magnetic field change. SOLUTION: When a control circuit 8 using a microcomputer receives a shut-off signal sent from a test switch 7 according to a magnetic field change of a test shut-off magnet 2, the circuit 9 outputs a shut-off valve close signal. When the circuit 8 receives a reset signal sent from a reset switch 9 according to a magnetic field change of a rest magnet 6 for giving the change to the switch 9, the circuit 8 outputs a shut-off valve open signal. Here, a shielding plate 10 is installed as a magnetic shut-off means having a shape covering the switch 9 and a thickness of, for example, about 1 mm made of a magnetic metal such as a steel sheet or the like is installed between the switch 7 and the magnet 6 and between the switch 9 and the magnet 2.
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