| 摘要 |
PURPOSE:To prevent undesired noise from being invaded into the telephone set. CONSTITUTION:A PCM signal separated by a line interface circuit 11 is inputted to a photoelectric conversion circuit 13, in which the signal is converted into an infrared ray subjected to optical modulation and the infrared ray radiates into space through an optical system lens 14. When the infrared ray is inputted to an optical system lens 21 of a head set 20, an photoelectric conversion circuit 22 demodulates the infrared ray into a digital voice signal, a CODEC 23 converts the digital voice signal into an analog voice signal and the signal is outputted from a receiver 24 as an audible voice signal. The analog voice signal outputted from a transmitter 25 of the head set 20 is converted into a PCM signal by the CODEC 23 and given to the photoelectric conversion circuit 22, from which the signal is converted into the infrared ray subjected optical modulation and the infrared ray is made incident in the photoelectric conversion circuit 13 from the optical system lenses 14,21 through space and converted into the digital voice signal and it is inputted to the line interface circuit 1. |
