| 摘要 |
Electrodes S1, S2 for sensing a conductive liquid and/or an inductive field are coupled to an amplifier 1, 3 which controls a switching transistor 5. The amplifier 1, 3 is sensitive enough to be responsive not only to sea water but also to de-ionised tap water or reservoir water. The device may be attached to a life jacket so that transistor 5 turns on a light or radio beacon 9 when water connects electrodes S1, S2. Alternatively, the electrodes S1, S2 may act as aerials responsive to an inductive field developed by a human or an animal or by an active power circuit, the device being used as a trigger in alarm systems, for example. Amplifier transistor 3 may directly drive an additional low power load such as a lamp 11. A damping capacitor (19), (Fig. 2), may be included to prevent the device responding to an inductive field. <IMAGE>
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