Coordinate reading system

Abstract

A coordinate reading system that allows the determination of coordinate values without scanning has a simplified tablet structure and increased coordinate calculation speed. A coordinate indicator contains a coil and generates an AC magnetic field by excitation signals received from an excitation signal generating circuit. Sense lines having unequal width (zigzag sense lines) and/or rectangular return sense lines are laid in the tablet to induce signals having amplitudes that correspond to positions of the coil on the tablet when the AC magnetic field is generated. A selecting circuit directs the induced signals sequentially to a signal processing circuit. The signal processing circuit generates envelope signals of the induced signals. A calculating circuit calculates the coordinate values from the envelope signals generated by the signal processing circuit.