| 摘要 |
PURPOSE:To shorten the period when no contact is secured between a rotary head and a magnetic tape and to increase the quantity of information read out during a unit time, by accelerating and decelerating the drum revolution for the period when the rotary head has no contact with the magnetic tape in a high-speed search mode. CONSTITUTION:In a high-speed mode the maximum voltage is applied to a motor 9 for a period between t1 and t2 when the rotary heads 10 (10A, 10B) have no contact with a magnetic tape 11. Thus the motor 9 is accelerated. While the motor 9 is decelerated with the minimum voltage applied to the motor 9 for a period between t2 and t3. The drum revolving angle is set at 90 deg. for a period between t1 and t3 after the pulses supplied from a frequency generator set at the drum of the revolving side. While the angular revolutional frequency is kept at omega1(t1)=omega2(t3)=omega0 by a drum servo circuit. In such a way, the time t1 needed for 90 deg. revolutions of a fixed speed is reduced down to t3-t1=tx. As a result, the section T1 where the head 10 has a contact with the tape 11 is increased in a rewind mode with a no-contact section T2 reduced respectively. In such a way, the quantity of the read-out information per unit time is increased.
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