| 摘要 |
PURPOSE:To improve the secrecy by adding a preemphasis circuit and a deemphasis circuit to the transmission side and the reception side respectively. CONSTITUTION:A preemphasis circuit 6 is added to the transmission side, and a deemphasis circuit 26 is added to the reception side. When an audio input signal is impressed to a terminal 1 in the transmission side, its frequency spectrums are inverted, and one of them is selected by the preemphasis circuit 6 and is superposed and transmitted. Consequently, the input audio signal of the transmission side cannot be reproduced faithfully in an output terminal 25 of the reception side unless frequency characteristics of the deemphasis circuit 26 are opposite to those of the preemphasis circuit 6. |
