| 摘要 |
PURPOSE:To prevent malfunction by noise and to easily demodulate each of SIF signals by performing identification detection of sound inter-carrier frequency (SIF) signals by FM detection in performing demodulating reproduction of each of SIF signals whose frequency is different. CONSTITUTION:SIF signals of 6.5MHz, when led out from inter-carrier detection circuit 1, are inputted through filter 11a into FM detecting IC12 and are detected. The same is applied to SIF signals of 6.0MHz. In case of SIF signals of 5.5MHz, they are not inputted into IC12 and a detection is not conducted. Switch signal generator 17 relative to each SIF signal input outputs switch signals Sa, Sb, and Sc, by which switch circuit 3 and oscillation circuit 6 are controlled based on its detection input. As a result, outputs of mixed circuit 5 are made as SIF signals of 5.5MHz and inputted through ceramic filter 7 into IC2 to be sound detected.
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