To establish an electronic pen communication method with low power consumption.

A handwriting input system is an electronic pen that has one or more ultrasonic-electromagnetic wave emission circuit and an ultrasonic emission element which emit an ultrasonic signal and an electromagnetic wave signal for detecting position coordinates and a pen switch which is a sensor for detecting handwriting state and function keys; and emits an ultrasonic signal and an electromagnetic wave signal based on a signal table in which emission time intervals are predetermined. The handwriting input system having receiving device that includes an electromagnetic wave receiving element and at least two or more ultrasonic receiving elements for receiving the ultrasonic signal and the electromagnetic wave signal emitted by the electronic pen during handwriting and float writing to detect position coordinates of the electronic pen based on a difference in arrival time between the electromagnetic wave signal and the ultrasonic signal during handwriting and float writing. Time intervals of electromagnetic wave emission signals for obtaining position coordinates of the electronic pen are varied, and the variation of the time intervals of the electromagnetic wave signals is collated with a predetermined signal table on the receiving device side, and thereby ON/OFF information of the pen switch and the function keys is obtained.