| 摘要 |
PURPOSE:To reduce noise without feeling of disorder by setting an operating state optimized to each mode corresponding to the sound multiplex mode. CONSTITUTION:Only a voltage controlled attenuator (VCA) 15 is used at the maximum attenuation infinity at stereo mode, and in case of the two-language mode, a voltage controlled filter (VCF) 18 is operated at first by making the feeling of disorder important. When an electric field is decreased, the VCA 15 is used at a less attenuation or not operated entirely. The VCA 15 and the VCF 18 are provided independently and it is substantially equivalent that the VCF 18 is replaced with a CR circuit in the attenuation circuit in the VCA 15. Thus, the circuit is constituted that a switch in the VCA is turned at the stereo mode as the VCA with the maximum attenuation infinity and the switch is turned off as the VCF at the 2-language mode. Thus, the VCA 15 is replaced with the VCF 18 to use one circuit switchingly according to the mode.
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