| 摘要 |
PURPOSE:To prevent glitch from being generated by providing a muting circuit operated synchronizingly at the changeover of an electronic switch so as to operate the muting circuit near zero crossing of a sound signal outputted from an electronic circuit. CONSTITUTION:An electronic variable resistor 13 is not activated so far as a driving strobe 22 is inputted even if a data is given to a terminal 27 and a clock is inputted to a terminal 26. A sound signal subject to required attenuation is outputted at an output terminal 19 in this case. This is sampled by using it as a sampling signal 24 and a high level output 21 is inputted to a driving pulse generating circuit 15 when the voltage reaches the vicinity of zero volt by a zero cross detector 14. Then, the circuit 15 inputs a driving pulse 23 of a muting switch 16 to a switch 16 and inputs the driving pulse 22 to the electronic variable resistor 13. The variable resistor 13 is activated to change over the electronic switch, the switch 16 is grounded in synchronizing with it and a sound signal output is muted.
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