| 摘要 |
A variable resistor unit is provided which comprises a resistance element arranged in an annular configuration and a contact arm turnable on a shaft in sliding contact with the resistance element. The variable resistor unit with its shaft is supported by a support plate which is movable linearly as directed by guide means including a guide rod. A pulley is fixedly mounted on the shaft of the variable resistor unit, and a string wrapped around the pulley extends crosswise therefrom to have its ends tightly retained at both extremities of the stroke of the support plate. Hence, as the support plate is moved linearly by means of a knob affixed thereto, the pulley is turned by the string to cause the corresponding change in the angular position of the contact arm relative to the annular resistance element of the variable resistor unit.
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