| 摘要 |
PURPOSE:To reduce the pop tone appeared at an output terminal, by locating a muting element producing pop tone before a leakage filter, in a muting circuit of an FM stereophonic radio receiver. CONSTITUTION:A composite signal being an output of a detector inputted to a stereophonic demodulator 7 of an FM stereophonic radio receiver is demodulated into left and right signals and inputted to an amplifier 8, and the output is applied to a filter 9 via resistors R18, R19 constituting the input impedance of a leakage filter. Taking the values of the resistor R18, R19, equal as a half of a resistor R15, pop tone produced at a muting transistor 17 controlled with a muting control circuit 102 is 2/3 at an output terminal 20 to be almost halved. The attenuation of a signal is -49.5dB and the attenuation when muting is operated is at -47dB, which gives deterioration of only 2.5dB, indicating almost no effect. |
