| 摘要 |
PURPOSE:To effectively utilize the frequency band of a transmission line, by respectively providing sound signal delaying circuits, a means which designates delaying time, and circuits which mix two sound signals to a privacy processing circuit and a privacy restoring circuit. CONSTITUTION:The privacy processing circuit on the transmission side (a) is provided with the 1st designating means 3, 1st delaying circuit 2 which delays input sound signals by a delaying time T1 designated by the means 3 and, at the same time, outputs the sound signals after multiplying the sound signals by (a1), and the 1st mixing circuit 4 which has two input terminals I1 and I2, adds the r1 times of an I1 input and r2 times of an I2 input to each other, and outputs the added results. Sound signals inputted from a sound signal input terminal 1 are supplied to the I1 terminal of the 1st mixing circuit 4. The output of the 1st mixing circuit 4 is fed back to the I2 terminal through the 1st delaying circuit 2. The output to a privacy sound signal output terminal 5 is fetched from the input terminal, a midway stage, or the output terminal of the 1st delaying circuit 2. The receiving side (b) is also constituted of a delaying circuit and mixing circuit.
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