| 摘要 |
PURPOSE:To prevent interception of a voice signal by sending a modulated optical signal corresponding to a sound from a sound source and converting the optical signal into a radio wave corresponding to the sound of the sound source and relaying the converted signal so as to reduce leakage electric field strength. CONSTITUTION:A voice output signal of a movie enters an amplification modulator 12 from a movie set 11, in which the signal is amplified and modulated and the result is sent to an infrared ray transmitter 13. The infrared ray transmitter 13 emits a modulated infrared ray signal 22 and gives the signal 22 to a relay pole 25. The signal is converted into a voice output signal corresponding to the voice output signal of the sound source by the converter and sent to an FM car radio set 50 as an FM radio wave 90. Then a movie voice is reproduced from the FM car radio set 50. Thus, leaked electric field due to leakage of a radio wave between the sound source and the relay means is reduced and interception is prevented. |
