| 摘要 |
<p>PURPOSE:To obtain a high-quality slowmotion picture with no noise caused on a TV picture receiver, by setting the period during which the level of the reproduced picture signal is lowered at a position near a vertical synchronizing signal. CONSTITUTION:A period during which the level of the reproduced signal is lowered occurs before the trailing phase of a head switch pulse (a). Accordingly a waveform (j) is obtained by a noise level detecting circuit 14. Then the output (i) of an adverse sawtooth wave generating circuit 12 showing the phase of the pulse (a) is sample-held 15. Thus the DC voltage (k) corresponding to the phase of the pulse (a) against the noise position of a static envelope is obtained and then supplied to a plus terminal in the form of the threshold voltage of a comparator 17 to deliver a signal (f). The signal (f) is fed to a mono-multi 18, and accordingly a brake is applied for a certain time duration (g) to a capstan 22 by a motor braking circuit 19. Thus the shift of a magnetic tape is stopped. In such way, the period during which the level of the reproduced signal is lowered can be set at a position near a vertical synchronizing signal.</p> |
