| 摘要 |
An input device for a computer controlled visual display enables an operator to instruct the shift of a display element in a chosen direction by hand movement of the input device sensor in an analogous direction over a plane surface. The sensor includes a conventional piezoelectric audio pick-up 14 which produces a succession of unidirectional pulses when the stylus is drawn across a microscopically textured surface such as a sheet of paper, the polarity of the pulses being indicative of the direction of motion along a selected axis. A second pick-up 16 is arranged to give a maximum response to motion along an orthogonal axis and for the component of motion on each axis a bi-directional pulse counter enables the direction of motion to be determined by a comparison of the counts held in successive time intervals. <IMAGE>
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