| 摘要 |
PURPOSE:To provide a rotation control device which synchronizes the rotation of a rotating body against the periodic signals reproduced by a head, eliminates an instability in the control and brings its control effectiveness into full play utilizing the periodic signals. CONSTITUTION:An amplifier.filter 19 controls drum rotation by employing a speed control section 5 which controls a drum rotational speed, a phase control section 6 which controls a drum rotational phase and horizontal synchronization signals reproduced by a head 1 from a magnetic tape T. Furthermore, a switching control block 10 switches an operation and no operation of the control by using the horizontal synchronization signals and the block 10 expands the control pull-in region of the speed control section 5 and the phase control section 6. And the block 10 detects whether the period of horizontal synchronization signals is within a prescribed region or not and whether the reproduction signal level from the head 1 exceeds a prescribed level or not and the above mentioned operation and no operation are switched in accordance with the detection results. |
