PURPOSE: To prevent detour and mutual interference by using a radio wave for the transmission of one way and using light for the transmission of the other way.
CONSTITUTION: A sound signal from a microphone 1 passes through an amplifier 2, a modulator 3, and a BPF4 and is transmitted as a radio wave from an antenna 5. This radio wave is received at an antenna 6 and the sound is outputted from a speaker 10 through a BPF7, a demodulator 8 and an amplifier 9. Further, the sound signal from a microphone 21 passes through an amplifier 22, an optical modulator 23 and a photodetector drive circuit 24 to apply luminance modulation to an optical of a light emitting element 25. This optical output is received at a photodetector 26, and the sound is outputted from a speaker 30 through an optical front end 27, an FM modulator 28 and an amplifier 29.
TOYOSHIMA MASAKATSU
OSAKABE YOSHIO
