Stylus switch status determination in a digitizer tablet having a cordless stylus

摘要

A digitizer tablet with a cordless transducer which is capable of providing to the tablet information relating not only to the position of the pointing device but also with respect to the status of any button switches on the transducer. This is obtained by providing a plurality of oscillators, connected in circuits in which the relative ratio of the signal frequency outputs of the oscillators can be varied in response to activation of a switch while at the same time the sum of the amplitudes of the oscillating signals remain constant. Thus, the determination of the sum can be used as a indication of the position of the pointing device with respect to the tablet, whereas by determining the differences in the signal intensities of the different frequency oscillating signals, it is possible to determine the status of the button switches on the pointing device. The invention is typically used with a stylus or cursor driven tablet.