A battery-less terminal (1) has means (21) for photoelectrically converting an optical signal from an information transmission device (2), means (12) for outputting the electric signal generated by the photoelectric conversion means (21) as sound, means (13) for reflecting infrared light for position emitted by a position detection device (3), a light source (14) for infrared light for ID, means (15) for storing ID data, and means (16) for modulating the infrared light for ID in accordance with the ID data. The information transmission device (2) has a light source (21) for an optical signal and means (22) for modulating the strength of the optical signal in accordance with the electric signals of sound information. The position detection device (3) has a light source (31) for the infrared light for position, means (32) for imaging the infrared light for position reflected by the battery-less terminal (1), and means (33) for detecting the position of the battery-less terminal (1) based on the infrared image by the infrared imaging means (32). An ID detection device (4) has an infrared sensor (41) receiving infrared light for ID from the battery-less terminal (1) and outputting ID data.