| 摘要 |
c A wireless coordinate input system for a display system includes a stylus that transmits ultrasonic energy to a plurality of ultrasonic receiving stations in a projection plane. The stylus includes one ultrasonic transmitter used for determination of three-dimensional coordinates of the stylus relative to the projection plane. The stylus also includes a second ultrasonic transmitter controlled by a pressure activated switch. When the stylus is pressed against the projection plane, the second transmitter turns on and is used for determination of two-dimensional coordinates of the stylus in the projection plane. The stylus also includes a higher frequency burst transmitter used to generate a time reference. One or more of the ultrasonic receiving stations also includes an ultrasonic transmitter for calibration.
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