| 摘要 |
The invention provides a novel key-board switching unit used, for example, in pocketable electronic calculators for producing binary-coded signals corresponding to contacting of movable contact points on the bottom surface of a keyboard covering pad and fixed contact points on the printed circuit board on which the covering pad is mounted when pushed with a finger tip or a pushing means. The printed circuit board in the inventive switching unit has a so fine and complicated circuit pattern that, in the prior art, one or more of jumping circuits crossing over a printed base pattern are indispensable resulting in much increased production costs while, in the inventive switching unit, the circuit pattern on the circuit board per se may be incomplete by the lack of such jumping circuits and, instead, the covering pad is provided with conductive connections corresponding to the lacking jumping circuits on the circuit board to form necessary jumping circuits when the covering pad is mounted on the circuit board.
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