| 摘要 |
PURPOSE:To prevent the waste of the energy consumption of the title device and to improve usability by providing a means to detect the sitting-down of a person at each seat, and turning off the power source of a receiving device when the seat is not occupied. CONSTITUTION:Pictures 3a to 3d are provided so as to face plural seats 2, and carriers, which are modulated by an acoustic signal individually corresponding to the pictures 3a to 3d, at mutually different frequencies are transmitted from a transmitting device 5 by radio waves. The respective seats are equipped with a receiving device 15, an operating means 14 to select a single acoustic signal and a detecting means of illuminating light. When the person is not seated at the time of the power source input to the receiving device 15, the detecting means 13 detects the illuminating light, and the after the passage of a fixed time, it turns off the power source of the receiving device 15. |
