| 摘要 |
PURPOSE:To eliminate the interference to the sound signal by increasing the recording level of the sound signal which works synchronously with the vertical blanking pulse of the luminance signal and receives the modulation of frequency during a working period. CONSTITUTION:A pulse generating circuit 16 is connected to a vertical synchronizing separator 17 and produces a pulse synchronous with a vertical blanking pulse. This pulse is supplied to a changeover switch 15c of a pre-emphasizing circuit 15, and buffer circuit 13 and 14 are connected via a signal line 15a during a vertical blanking period. Therefore the sound signal produces a difference of amplitude equivalent to a gain drop set at an attenuator 15d between the blanking period and other periods. Thus it is possible to avoid the S/N reduction due to the interference of the leaked signal even though the video sweep signal, etc. are partially leaked into the band of the sound signal. |
