| 摘要 |
<p>PURPOSE:To ensure a stable shift without generation of noise for a helical scan type VTR, by detecting the position of a magnetic head which reproduces the signal of a recording track and carrying out the rotary driving synchronously with the detected position. CONSTITUTION:A magnetic tape 1 is driven toward an arrow 5 by a capstan shaft 2, and themagnetic heads A and B of a rotary drum 4 are alternately set opposite to the tape face to carry out the helical scan. The time positions of the heads A and B are detected by a position detecting circuit 6 and then fed to a phase locking circuit 7. The circuit 7 consists of an FF circuit containing the transistors TR1 and R2 plus resistances R2-R5. A static picture command signal Vs is supplied to the base of the TR1, and at the same time an output VPG of the circuit 6 is fed to said base via a diode D1 and a capacitor Cx. An output Ec is fed to a motor driving control circuit 8 from a collector of the TR2, and a capstan motor 3 is controlled. In such way, the reproduction is possible with no noise although the mode switching is instructed in the course of a video track.</p> |
