| 摘要 |
An operating control for displacing at least one indicating mark inserted on the screen of a radar or sonar device, by means of a manually controllable roller ball and a bearing device fixing the roller ball with two degrees of freedom, in which, for the purpose of extensive vibration resistance, insensitivity to dirt and temperature independence with at the same time ease of movement of the roller ball in all directions of movement, the bearing device exhibits a bearing ring, enclosing the roller ball at a distance, with three roller bearings offset with respect to one another by 120 DEG and each roller bearing exhibits a roller element adjoining the roller ball. The roller element is arranged in such a manner that the line connecting the points of rotation of roller element and roller ball encloses an angle of between 45 DEG and 90 DEG , preferably 80 DEG , with the centre axis of the bearing ring. Another roller element is arranged above the first roller element, approximately symmetrically with respect to the latter, and rests against the roller ball under spring pressure.
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