| 摘要 |
PURPOSE:To apply muting in an assured way with a simple circuit, by deciding both the muting delay time and the muting time based on the charge/discharge time of a capacitor. CONSTITUTION:Changeover switches 16-19 are provided. The switch 17, for example, is pushed to deliver a switch signal Bi. An FF24 is set by the signal Bi, and an FET26 is turned on to start the discharging of a capacitor 27. The output of the FF24 is applied to a TR12 via an OR32, and the TR12 is turned on to start a muting action. When the terminal voltage VCR of the capacitor 27 is less than the threshold level of an inverter 30, the FF24 is reset. Then the FET26 is turned off to start the charging of the capacitor 27. When the voltage VCR exceeds the threshold level of a Schmitt inverter 31, the output G2 is set at an L level. Then the TR12 is turned off to complete the muting action. |
