<p>A coordinates input apparatus such as a digitizer has: vibration propagation medium such as a transparent glass plate for allowing a vibration to propagate therethrough; an input pen for applying vibration (50) to the vibration propagation means; vibration detecting means for detecting vibration (51) applied by the input pen; envelope output means for producing an envelope signal (52) representing the envelope of the vibration detected by the vibration detecting means; differentiation means for conducing a differentiation (53) of the envelope signal produced by the envelope output means so as to determine the peak (at time Tg); control means adapted for determining, as the time of arrival of the vibration, a zero-cross point of the vibration (51) detected by the vibration detecting means located in the vicinity of a zero-cross point of the signal (53) from the differentiation means; and computing means for computing the distance between the input pen and the vibration detection means from the time determined by the control means. <IMAGE></p>
