| http://www.w3.org/ns/prov#value | - H0lh 35/00 capacitance detecting circuit which delivers a switch- [58] Field of Search 307/116; ZOO/DIG. 1; ing signal when the capacitance is increased by the ap- 340/258 C proach of a hand, wherein the improvement comprises that the switch remains unaffected by the approach of [56] References Cited all other substances, such as metals or insulating mate- 7 UNITED STATES PATENTS rials- 3,109,893
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