JPS5719884A - Coordinates detector - Google Patents

Abstract

PURPOSE:To detect pen down and to improve stability in action of a coordinates de- tector by a delay time detecting system by detecting zero crossing of a plate wave elastic wave and by comparing the plate wave elastic wave with two threshold values that are high or low in level. CONSTITUTION:A detected signal Vs that was converted to an electric signal by a voltage element inside an input pen and was amplified in an amplifier 11 is inputted to comparators 51, 52 and 56 and the crossing point of leading and trailing of zero of the plate wave elastic wave is detected in the comparator 51 and a single pulse Ve is outputted by a signal pulse generator at a trailing point of a pulse train detected above. Further reference potentials E1, E2 as two threshold values in low and high are compared with a signal Es in comparators 52, 56 respectively and through FF circuits 53, 54 and an AND circuit, a detected pulse Vd is sent to a circuit by which coordinates are counted. Further, to the AND circuit which takes an output of the comparator 56 as an input, a detected pulse Vd is added, through a monostable multiplier 55, and from the AND circuit, a signal that indicates that pen down was done is outputted, thereby allowing an action of a coordinates detector by a delay time detecting system is stabilized.