| 摘要 |
PURPOSE:To discriminate automatically the tape speed during recording by reproducing plural pilot signals of different frequencies by a rotary magnetic head, extracting and detecting the signal components for the frequency difference from the frequency of a carrier signal and comparing the same with a set threshold value. CONSTITUTION:The pilot signals of the frequencies f1-f4 are superposed on a video signal and are recorded in the diagonal tracks on a magnetic tape by a rotary magnetic head 8 in synchronization with the head switch signal to be inputted to a terminal 1. A selection switch 6 is set to the play side and the signal component for the frequency difference between the detected pilot signals and the frequency of the carrier signal is obtd. from a mixer 11 and is detected with BPFs 12, 13 in the stage of reproducing. The detected output is passed through a subtractor 16 and is made into the tracking error signal from a terminal 19. Said output is also supplied via gate circuits 30, 31 to comparators 21, 22 by which the output is compared with the set threshold value. A relational discrimination circuit 24 can discriminate the tape speed from the speed generator signal from a capstan motor inputted to a terminal 25 and the outputs from the comparators 21, 22.
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