| 摘要 |
The present invention provides a coordinate data entry device comprising a plurality of receivers disposed in the vicinity of a board surface, and a position indicator to transmit signals, at least one of which employs ultrasonic waves, to the receivers, thereby detecting the position of the position indicator on the board surface and making the coordinate position thereof available for entry, in which the signal employing ultrasonic waves is transmitted at an arbitrary time interval, and an ultrasonic oscillating circuit transmitting the signal employing ultrasonic waves comprises a resonant circuit formed of an ultrasonic resonator and a coil, which are connected in parallel with each other, and the amplitude of a start current of the ultrasonic resonant circuit is made variable according to the lapse of time, thus allowing the variations in performance of the resonant circuit including the ultrasonic resonator to be smoothed out and making stabilized positional detection possible.
|
