| 摘要 |
A control device for a film or tape transport comprises a control knob (10) having a spindle (12) which forms the rotor of an electric motor (14). The control knob is spun by the operator to generate a drive signal to advance or retard the film or tape driven by the transport system at a speed dependent on the speed of rotation. The rotational speed is sensed and a signal dependent thereupon is produced by a speed detector (16) to control a servo-loop which drives the electric motor. The motor drives the control knob at substantially the same speed imparted by the operator without any further input by the operator. The control knob continues to be driven at this speed until the operator manually accelerates or decelerates the control knob. The speed detector (16) may detect the back emf generated in the motor or may (Fig 2 not shown) include a conventional shaft encoder. <IMAGE> |
