| 摘要 |
Safety device used in the detection of a conductive liquid in an enclosure to be monitored, in which the variation of the resistance as a result of the presence of the liquid between electrodes triggers an electrical alarm circuit, wherein it comprises in combination: a liquid detecting member constituted by two spaced electrodes and forming four contacts; a first field effect transistor, whose gate, source and drain terminals are connected to a power supply and to the four aforementioned contacts in such a way that the first field effect transistor is non-conducting when the conductive liquid is absent and where there is no deterioration to any one of the connections connecting the terminals of the first transistor to one or other of the said contacts; and a second field effect transistor, whose source and drain terminals are connected to a second power supply and whose gate terminals are connected to the drain terminal of the first field effect transistor in such a way that the second transistor is conductive under the aforementioned conditions in which the conductive liquid is absent and when there is no deterioration to one of the connections of the circuit, and supplies current to an alarm, signalling and control circuit of an enclosure to be monitored, the respective conduction and non-conduction states of the first and second field effect transistors being reversed when one and/or the other of the aforementioned conditions changes state.
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