| 摘要 |
PURPOSE:To avoid giving the feeling of physical disorder to the listener by switching the demodulation output from stereo to monaural mode in steps and thus improving the S/N in accordance with the field intensity. CONSTITUTION:When the field intensity is reduced, the signal applied to the control terminal decreases along with the switching signal of 38kHz decreased as well. As a result, the right-left separation of the stereo signals is deteriorated. When the field intensity reaches the prescribed level, the monaural signals are obtained through output terminals 33 and 34. At this moment, the mode transfers from stereo to monaural in sequence according to the deterioration of S/N, and thus the feeling of physical disorder caused by the improvement of S/N is not given to the listener. When the field intensity lowers down more, the value becomes approximate to each other between control signals t1 and t2 which are applied to 1st and 2nd sum signal circuits 21 and 21'. As a result, the signal being to flow to high-band cutting circuit 31 to cut the high band of the demodulation output, thus improving the S/N. |
