Coordinate inputting system with provision for erroneous input detection

In this coordinate inputting system, a coordinate inputting sheet is provided for detecting an axial coordinate, and this includes a sheet body with a resistive surface laid over one of its sides, a pair of mutually substantially parallel edge electrodes extending along opposite edges of this resistive surface which are for having voltage applied between them, and several intermediate electrodes, substantially mutally parallel and substantially parallel to the pair of edge electrodes, and extending along the resistive surface between the pair of edge electrodes in a mutually spaced relationship. Also, there are provided a device for processing information by obtaining voltage divided at an input point selected by pen contact against the coordinate inputting sheet as axial coordinate information, a device for storing in advance reference information relating to the voltages on the electrodes when the voltage is applied between the edge electrodes, a device for detecting which of the electrodes straddle the input point by comparing the axial coordinate information obtained from the information processing device with the reference information, and a device for determining the validity of input operation according to the result of comparison between the voltages upon the electrodes which straddle the input point and the reference information. Optionally, the reference information may include the voltages on the electrodes when the voltage is applied between the edge electrodes, and the voltage differences between neighboring ones of the electrodes.