JPH0434173B

PURPOSE:To prevent the output of the inaccurate coordinate value by enclosing an area out of a valid area by a deciding lead wire and deciding based on the output of said lead wire whether a coordinate indicator is set in the valid area or not. CONSTITUTION:A lead wire 20 is set on an insulated substrate 9 and at the same time a deciding lead wire 21 is set on a substrate 19 with insulation se cured from the wire 20. The inner edge line 21i of the wire 21 is set on the fringe of a valid area on a tablet 5'. While the outer edge line 21u of the wire 21 is set at the outer edge of the substrate 9. An area A enclosed by the line 21i shows a valid area; while an area B enclosed by both lines 21u and 21i shows an invalid area. An energizing coil 4 incorporated in anpointing device is energized a reduction pulse given from an oscillator and generates a magnetic field. A data processor 13 controls a switch 6 to calculate the coordinates of the position of the pointing device and at the same time to decide based on the output of a phase comparator 12 whether the pointing device exists in the area A or B. Then the processor 13 delivers the calculated coordinates when the pointing device is kept within the area A.