Telegraphy – Systems – Position coordinate determination for writing
Patent
1993-10-25
1995-04-18
Chin, Stephen
Telegraphy
Systems
Position coordinate determination for writing
345179, G08C 2100
Patent
active
054080550
ABSTRACT:
A device for indicating the phase of the a full-frequency alternating current (AC) magnetic field signal transmitting from the pointing device of a cordless digitizer and for determining if the phase of a half-frequency alternating current (AC) magnetic field signal transmitting from the pointing device is approximately the same or approximately inverted from an immediately preceding half-frequency signal from the pointing device. The indication of the phase of the full-frequency pointing device signal is used by the digitizer logic circuits to determine the location of the pointing device on the tablet's sensing surface. The information concerning the change in phase of the half-frequency signal is used by the digitizer logic circuits to decode the status of various pointing device buttons. If the phase in the induced half-frequency signal is unchanged from the last, this no-change condition represents one binary state. If the phase has changed, the condition represents the other binary state. Accordingly, a binary encoded message may be transferred from the pointing device to the digitizer tablet for decoding via this phase change method.
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Harris Andrew M.
Watson James
CalComp Inc.
Chin Stephen
Kim Kevin
Porter, Jr. Wm. F.
Streck Donald
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