| 摘要 |
PURPOSE:To suppress a carrier with optional suppression when a voice signal is not detected by a voice signal detector by using a DC voltage applied from a suppressing amount setting circuit so as to change the attenuation (suppressing amount) of a voltage variable type attenuator provided at the post-stage of a modulator. CONSTITUTION:The carrier inputted from a terminal T12 is modulated by a voice signal inputted from a terminal T11 and the result is fed to a voltage variable type attenuator 13. For example, a digital signal outputted from a suppressing amount setting device 14 is converted into a DC voltage by a D/A converter 14a, fed to the voltage variable type attenuator 13 to control the suppressing amount. When the voice signal Vs is detected by a voice signal detector 11, the output voltage controls a suppressing amount setting device 14b so that the attenuation of the voltage variable type attenuator 13 is almost zero, and when the voice signal Vs is not detected by a voice signal detector 11, the carrier is suppressed by a prescribed amount or completely by the voltage variable type attenuator 13 according to the setting value of the suppressing amount setting device 14b.
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