| 摘要 |
<p>PURPOSE:To stabilize an access signal during high-speed retrieving with economical constitution by variably controlling the revolutionary speed of a drum with use of the envelope of a reproduction signal varying associatively with the tape speed so as to keep the relative speed of a head and the tape constant. CONSTITUTION:In the normal reproduction operation, a switch 39 turns on, the output of a differential amplifier 41 is zero because the output from an envelope detection circuit 37 is inputted to both of first and second peak holder circuits 38 and 40, and hence no control voltage is supplied to a servo system. Therefore, a drum motor 43 rotates at a constant speed. On the contrary, the switch 39 turns off during the high-speed retrieving, and the output from the detection circuit 37 is inputted to the first peak holder circuit 38, but in the second peak holder circuit 40 is an envelope peak level value during the normal reproduction operation held. These peak level values are compared by the amplifier 41, and its result is amplified to be supplied to the servo system. Accordingly, the servo system controls the motor drive circuit 42 with the voltage that includes the said differential voltage. As a result, a stable signal of a value approximately equal to that during the normal reproduction operation is obtained.</p> |
