| 摘要 |
PURPOSE:To prevent the generation of noise by an excess of compensation by judging that a frequency of a generation of a drop out is high when an interval of the drop out is shorter than a predetermined period, and muting a modulation signal for a longer period than that period. CONSTITUTION:By a first transition of a drop out detecting circuit 7, a monostable multivibration (MM) MM 23 generates a pulse of a narrow width. This pulse is fed to an MM 24 and an AND gate 25, and the MM is triggered by a last transition of the pulse and the output thereof holds an H level for a predetermined period after triggering. When during this period, a next trigger pulse g is fed the H level is held for a further constant period. The pulse g generated from the MM during an output of the MM 24 being H is extracted out at the AND gate 25 and fed to an MM 26. An output of the MM 26 becomes a control input of a switching circuit 22, and the circuit 22 is connected to a terminal of the H side during an output of the MM 26, and an output of a muting circuit 21 is outputted to a terminal 14. Thereby, a generation of noises by an excess of a compensation of the dropout can be prevented. |
