| 摘要 |
PURPOSE:To eliminate a malfunction due to a weak electric field or a buzz or the like by switching and selecting the respective outputs of a sound detecting circuit according to a noise component included in the respective outputs of the sound detecting circuit corresponding to plural sound carriers. CONSTITUTION:The sound detecting circuits 3, 4 detect respectively the inputted sound carriers to obtain an audible frequency signal. Noise detecting circuits 10, 11 detect the noise component included in the audible frequency signal from the respective sound detecting circuits 3, 4. A comparator 12 compares the respective outputs from the noise detecting circuits 10, 11 to control a switching circuit 13 by the comparison output and output the audible frequency signal little in the noise component.
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