| 摘要 |
PURPOSE:To prevent abnormal stereo demodulation with the sample pulse not in synchronizing with the pilot signal, by stopping stereo demodulation and outputting monaural when the stereo composite signal is weak. CONSTITUTION:When the IF level is low, PLL1 is impossible for the synchronism and the sample pulse not in synchronizing with the pilot signal is produced. Further, the IF level discrimination circuit 4 produces a fixed output. Thus, the sampling signal is not pulse but a fixed signal. With this sampling signal, the sample hold circuits 2, 3, are always in sample state with the output from the IF level discrimination circuit 4 independently of the sample pulse from PLL1, stereo demodulation is not made and the stereo demodulation signal is made, as it is, as right and left channel outputs. |
