| 摘要 |
A magnetic-tape apparatus (1) comprises at least two buttons (9, 10, 11) for selecting modes of operation of the apparatus and at least one apparatus part (37) to be positioned in conformity with the modes selected by actuation of the button. For positioning the apparatus part (37) the apparatus comprises a servo mechanism (50) which can be driven by a motor (27), which mechanism comprises a first eccentric means (71) arranged on a servo wheel (52), a drive member (73) which is movable by this eccentric means (71), and an actuating member (85) which is movable by the drive member (73) for positioning the apparatus part (37). Depending on the selected mode of operation, the actuating member (85) can be set to different positions defined by stops (20, 21 23) associated with the buttons (9, 10, 11) by means of a control device (86) which comprises a second eccentric means (87) which can be driven by the motor (27) and at least one scanning element (89, 90, 91) for scanning the stops (20, 21, 23) associated with the buttons (9, 10, 11), which cooperates with the actuating member (85) and which moves this member to the various positions. The servo disc (52) comprises a disc-shaped axially projecting portion (58) on one of its radial surfaces, which portion carries a circumferential cam (87). The cam (87) constitutes the second eccentric means and in the disc-shaped portion (88) at the deck side a groove (71) is formed which constitutes the first eccentric means.
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