Patent ID: 7675507

Claim:
A position detecting system comprising: a position indicator which has at least one coil and which indicates a position; and a position detecting apparatus for detecting the position indicated by the position indicator by transmitting/receiving signals to/from the position indicator by electromagnetic coupling, wherein the position detecting apparatus comprises: a first transmission coil for transmitting position detecting signals to the position indicator; a second transmission coil concentrically surrounding said first transmission coil for transmitting position detecting signals to the position indicator, said second transmission coil being connected in series to said first transmission coil and wound in the opposite direction; a plurality of sensor coils for receiving signals from the position indicator, said sensor coils being different than said first and second transmission coils; a signal transmitter operatively associated with and driving the first and second transmission coils so that the first and second transmission coils transmit position detecting signals of opposite phases; a receiver for sequentially selecting the plurality of sensor coils and for receiving the signals from the position indicator; and a position detecting unit for detecting the position indicated by the position indicator based on the signals received by the receiver.