DIGITIZER TABLET WITH CORDLESS POINTING DEVICE

摘要

A cordless digitizer system (10) is disclosed which comprises a digitizer tablet (11) and a cordless pointing device (12) which cooperate to provide to the tablet information relating not only to the position of the pointing device relative to the tablet, but also relative to the status of any switches (37, 38) on the pointing device. The pointing device (12) generates and radiates to the tablet (11) first and second signals (23, 24) of different frequencies. The first and second signals are radiated from the pointing device (12) at a third frequency (30) which contains information of the status of the switch. For example, one of the signals may be radiated relatively continuously or both of the signals may be alternatingly radiated at the third frequency in dependence upon the status of the switches. The first and second signals induce corresponding signals in the tablet which are processed to provide respective signals at the third frequency. These signals are then processed to obtain the status of the pointing device switches. Switch status information can also be binary encoded as a particular sequence of alternations of the first and second signals.