| 摘要 |
A control device provides a variable control signal to electrical apparatus and has a control member, such as a stylus or a turnable or slidable member, that is manipulated to vary the signal. Photoelectric sensors detect and track movement of the control member. The control member is disposed at the face of an electronic image display screen which can display calibration marks, identifying labels, current setting and/or other graphics pertinent to operation of the control device. The display screen also operates as the light source for the photoelectric sensors.
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