| 摘要 |
PURPOSE:To prevent the production of unpleasant sound due to noise component, by providing a switch circuit at the pre-stage of mechanical filter and performing control of conduction and interruption according to the stereo-other type of audio pilot signal. CONSTITUTION:The pilot carrier signal at an input terminal 10 is detected at a pilot signal detecting circuit 42, a stereo pilot signal and other type of audio pilot signal are appeared, and they are fed to mechanical filters 43, 44 via a switch circuit 45 which is conducted or interrupted with a switch control circuit 46. When the stereo pilot signal appears at the output of the filter 43, a switch 25 of a demodulation circuit of a receiver is turned on to change over to the stereo reception. If other type of autio pilot signal appears at the output of the filter 44, switches 28, 31, 32 of the demodulation circuit are changed over to the fixed terminal b, for change-over to other type of autio reception. |
