| 摘要 |
PURPOSE:To improve the operating time of a squelch circuit against stepwise changes in input, by utilizing a property that the response characteristic of an automating gain controlling circuit is sufficiently faster than that of the smoothing circuit which smooths unnecessary demodulation outputs. CONSTITUTION:By utilizing a property that the response characteristic of an automatic gain controlling circuit is sufficiently faster than that of a smoothing circuit 5 which smooths unnecessary demodulation outputs, conventional unnecessary demodulation outputs are detected, and by keeping the function which operates a squelch circuit as it is, the operating time of the squelch circuit against stepwise changes in input power corresponding to the transmission starting and stopping times of a transmission station, is shortened. Moreover, by operating a circuit 13 which generates a pulse voltage for a fixed time at the leading edge of the input signal, the time in which a switch 8 does not close and excessive noises are outputted due to the influence of the charging time of a conventional smoothing circuit 5, is sharply shortened and the demodulation output is normally outputted. |
