| 摘要 |
<p>PURPOSE:To make phases of a head switch signal and a reference phase signal coincide and pull in a phase synchronization of a drum at high speed by resetting a reference phase signal during a change over of an ordinary reproduction and a specific reproduction or during a change over of a standard reproducing mode and a long time reproducing mode. CONSTITUTION:A drum rotating phase controller of a VTR is constituted by a rest circuit 11, a reference signal generating circuit 7 and a phase control circuit 20 connected between them and a drum motor 4. In the circuit 20, a rotating position detector 5, a waveform shaping circuit 6, a phase comparator 8, a phase compensating circuit 9, and an amplifier 10 are incorporated. When a reproducing mode is changed from an ordinary mode to a specific mode by constituting in this manner, as shown in a time chart (e), a head switch signal is changed over to a phase delay of 90 deg., reversed in the circuit 11 and a reset signal (f) is generated by synchronizing with a rise of the signal (e). Then, it is inputted to the circuit 7 to obtain a reference phase signal (d) and make coincide the signal (d) with the signal (e).</p> |
