| 摘要 |
PURPOSE:To detect the accurate traveling length of a magnetic tape and to realize superior operability in its editing operation, etc., by operating the magnetic tape by a stationary magnetic head and detecting periodic variation based on whether or not a reproduction signal has azimuth loss at the time of fast for warding and rewinding of the magnetic tape where information is recorded on an azimuth basis. CONSTITUTION:Magnetic heads 21 and 22 which has a positive and a negative azimuth angle are mounted on both radial ends of a rotary cylinder 1. Then the magnetic tape 2 is wound around the side face of the cylinder 1 partially spirally. Further, one of the heads 21 and 22 contacts the tape 2 throughout fast-forwarding rewinding operation to reproduce the information recorded on the tape 2. Its reproduction signal is amplified by a head amplifier 3 and sent to a detector 4. Its output signal is waveform-shaped by a comparator 5, counted 6, and processed 7. Then a processing circuit 7 detects the periodic variation based on whether or not the reproduction signal has azimuth loss from alternate records of the heads 21 and 22 having the positive and negative azimuth angles and the traveling length of the tape 2 is calculated from the variation.
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