COMMUNICATION SYSTEM, PORTABLE COMMUNICATION DEVICE, OPPOSITE DEVICE, AND CONTROL METHOD

摘要

PROBLEM TO BE SOLVED: To facilitate finding of a portable communication device.SOLUTION: A communication system includes that: an opposite device 200 transmits predetermined wireless signal to a portable communication device 100 using wireless communication; the portable communication device 100 transmits ultrasonic signal, when receiving the wireless signal transmitted by the opposite device 200; and the opposite device 200 calculates distance between the opposite device 200 and the portable communication device 100 for notifying information indicating on a calculated distance based on a timing at which the opposite device 200 receives the ultrasonic signal transmitted by the portable communication device 100.