| 摘要 |
PURPOSE:To prevent the generation of distortions during a muting time and to improve the S/N by changing the aperture ratio of an aperture signal in response to a mute control signal which is separately supplied. CONSTITUTION:The aperture ratio is controlled by the level of a mute control signal (c), and as a result, a PAM signal (f) is delivered with no muting in a high level period of the signal (c). While the signal (f) is muted completely in a low level period of the signal (c) and not delivered. The soft muting is performed in a transition period. Thus a muting circuit is constituted just with addition of a pulse generating circuit 7 and an AND circuit 5. This circuit amplifies greatly the circuit constitution. In addition, no increment of distortions nor deterioration of S/N is never caused since no analog signal system is operated. |
