| 摘要 |
<p>PURPOSE:To switch the running speed of magnetic tape and the number of revolutions of video head to a state suitable for the types of video signals, by detecting the horizontal scanning frequency of reproduced video signals. CONSTITUTION:If the number of revolutions of a video head 13 and the types of video signals recorded in a magnetic tape 14 are different, the video signal in FM demodulation 18 is applied to a frequency discriminator 19. Further, the horizontal scanning frequency component passes through a discriminator 19 and is detected 20. This detected output is applied to a bistable multivibrator 21, the output is inverted, the running speed of the magnetic tape 14 and the number of revolutions of the head 13 are made to a state suitable for the reproduction of NTSC signal, PAL or SECAM signal via a cylinder motor control circuit 22 and a capstan motor control circuit 23. On the other hand, if the relation between a recorded signal and the number of revolution of the head 13 is normal, the horizontal scanning frequency does not pass through the discriminator 19 and the running speed of the head 13 and the tape 14 is unchanged.</p> |
