| 摘要 |
<p>1376449 Automatic tension control SONY CORP 17 Dec 1971 [19 Dec 1970] 58683/71 Heading G3R In video recording apparatus having video signals recorded on magnetic tape using oblique tracks, the tape tension is controlled according to a measured time interval between the passage of the end of one track and the start of a subsequent track. As shown, the signals are scanned by magnetic heads 2, 3 on a rotary assembly 1, and pass through a mixer 16 and demodulator 17 to terminal 19 via output circuit 18, and to separators 20, 21. From separator 21, horizontal synchronizing pulses are counted by counter 22, which gives an output pulse after a predetermined number, and which is reset at the start of a subsequent track by a vertical synchronizing pulse from separator 20. The output of counter 22 triggers monostable multivibrator 23, whose output is integrated and passes to gate 25, which is opened by vertical synchronizing pulses via monostable multivibrator 26, to give an output proportional to the period between adjacent tracks. Alternate pulses of this output are fed via gate 27 and associated trigger 28 to controller 29 to control the tape tension either using the supply reel motor 30 or the drive to the capstan 8. In an alternative Fig. 3 (not shown) the multivibrator is bi-stable, trigger 28 omitted and gate 25 is only opened by alternate vertical synchronizing signals. A known control system, to synchronize the position and speed of the magnetic heads relative to the oblique tracks on the tape, compares a tape speed signal, measured by a fixed magnetic head from signals recorded on the tape, and a signal indicative of the speed and phase of the rotary magnetic heads, as measured by detector 11, to control the rotary head assembly drive motor 4.</p> |
