| 摘要 |
The system (1) has a positioning device including a rotating unit for rotating a hollow spherical support element (3) with an electronic transmitter. The element is held on the positioning device by gravity on three bearing points (P, P`, P``). Two bearing points are constituted by two ball joints (30, 40), respectively, whose ball is placed free of rotation in a housing of the joint (30), so that a portion of the ball is emerged by an upper opening of the housing for contacting an exterior surface of the element. Figures in the form of circular bar codes (10) are disposed on the surface.
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