| 摘要 |
PURPOSE:To build in one receiver receiving circuits differing in modulation system, by using a signal obtained by rectifying a noise from an FM detecting circuit when no signal or small input arrives or by using a voltage from an AGC circuit when large input. CONSTITUTION:When no signal or small input arrives, a noise generated in FM detecting circuit 14 is led to active band-pass filter 21 and negatively rectified by diode D3, whose output is applied to the input terminal of squelching switching circuit 24. When large input arrives, on the other hand, fluctuations of an AGC voltage or a voltage fluctuating under the control of the AGC voltage are supplied to transistor Q3, which provides inverted DC amplification and its output positive voltage is applied to the input terminal of squelching switching circuit 24. Thus, the variable range of the squelch operation point is expanded. |
