| 摘要 |
PURPOSE:To simplify circuit constitution, to reduce the power consumption and to improve the degree of privacy of a privacy telephone circuit, by constituting an inverted privacy telephone circuit with an operational amplifier, analog switches and capacitors. CONSTITUTION:A voice signal from a voice signal input terminal 31 is applied to an input stage switched capacitor filter 25, the resistance of signal communication is changed with a clock from a clock signal input terminal 35 and the input of the voice signal is controlled. The frequency spectrum band of the sound signal is limited with the capacitors of the filter 25 and the operational amplifier, the output is applied to the analog switches 26-29 for spectrum inversion and non-inversion control, and the switches 26-29 are controlled with a clock frequency-divided at a 2n-frequency-division circuit 34. The sound signal outputted through the combination of the switches 26-29 is inputted to an output stage switched capacitor filter 30, a privacy telephone signal is outputted from a privacy telephone output terminal 32 with the clock from the terminal 33, the circuit constitution is simplified and the power consumption is reduced. |
