Abstract: A vibration generator (9) for a drilling installation comprises a housing (16), at least one rotation body (17), a suspension (24) by means of which the rotation body is suspended rotatably within the housing, the mass centre of the rotation body (17) being eccentric with respect to the rotation axis of the suspension, and a drive (18) for rotating the rotation body. The housing (16) holds a fluid (15) which is in contact with the rotation body (17) whereby relative rotation between the rotation body and the fluid generates a flow resistance and in that the rotation body comprises flow resistance reduction means (25).

Abstract: A vibration generator (9) for a drilling installation comprises a housing (16), at least one rotation body (17), a suspension (24) by means of which the rotation body is suspended rotatably within the housing, the mass centre of the rotation body (17) being eccentric with respect to the rotation axis of the suspension, and a drive (18) for rotating the rotation body. The housing (16) holds a fluid (15) which is in contact with the rotation body (17) whereby relative rotation between the rotation body and the fluid generates a flow resistance and in that the rotation body comprises flow resistance reduction means (25).

Abstract: The electronic device (1) of the invention contains a control unit (5) which is able to receive from a detector (9) a signal indicating insertion of an object (23) into an object holder (21) and/or removal of the object from the object holder (21). The control unit (5) is further able to use a reproduction means (7) to start reproduction of content in dependency on the signal from the detector (9). The object holder (21) of the invention contains a detector which is able to detect an insertion of an object into the object holder (21) and/or a removal of the object (23) from the object holder (21). The detector (9) is further able to generate a signal indicating the insertion and/or the removal and containing an identifier identifying the object and/or a further identifier identifying the object holder (21) and/or a position in the object holder (21). The system of the invention comprises the electronic device (1) and the object holder (21).