| 摘要 |
<p>PURPOSE:To rapidly retrieve the specified recording position of magnetic tape by so arranging the device that the servo gain of the reel servo system is changed over according to the changing-over of the intermittent feeding and rapid feeding of the tape. CONSTITUTION:The respective output signals of photo diodes 42a are respectively supplied to a detection circuit 50 which is so arranged as to provide the square wave signal of the width corresponding to the number of the photo diodes to which the light from a light source 42i is being radiated. These are then supplied to the respective input sides of the first and second DC amplifier circuits 52 and 53 which determine the servo gain of this reel servo system. Here, the second DC amplifier circuit 53 is made relatively large in its gain, i.e., relatively small in its time constant so that when the second Dc amplifier circuit 53 is connected to the reel servo system becomes high, whereby the follow-up characteristic to the change of tape quantity in a vacuum column 13 is enhanced.</p> |
