| 摘要 |
A stationary flat horizontal support member has an active circular area with a center point which defines a zero point of intersecting orthogonal X and Y axes. A first flat horizontal plate is disposed above and spaced from the member. The first plate is movable along either or both X and Y axes which are vertically aligned with the corresponding X and Y axes of the member. The first plate has an active circular area with a center and having a home position at which the center of the first plate is vertically aligned with the center point. The first plate is supported above the member in such manner that the first plate can be moved and held in an position with respect to either one or both of the X and y axes by an operator in an almost frictionless manner. Once the operator releases the hold, the first plate is automatically returned to zero position. A first dispacement signal monatonically related to the displacement of the center of the first plate from the center point of the member along the X axis and a second displacement signal monatonically related to the displacement of the center of the first plate from the center point of the member along the Y axis are both produced.
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