Abstract

An electromagnetic detector having plural loop coils arranged in parallel with one another in a position detecting direction determines a position coordinate value designated by a position indicator having at least a coil. One loop coil in each of plural groups is selected simultaneously from plural loop coils of the group so not less than a predetermined number of the relative positions of these selected loop coils are not the same or are a symmetric in each group and over a plurality of groups. A loop coil on which the position indicator is positioned is determined in response to a signal amplitude pattern obtained by the loop coil selection. This makes it unnecessary to select all loop coils at the time of starting a position detecting operation, to reduce the time required to determine the coordinate value. When the coordinate value is determined, digital data corresponding to an arbitrary AC signal are converted into an analog signal, and a reception signal sampled at a predetermined cycle to convert the AC signal into digital data. These digital data are subjected to predetermined computation to calculate amplitude and phase angle with respect to an arbitrary frequency component in the reception signal, whereby the concurrent use of a plurality of coordinate indicators is effected easily.