Abstract: A medical instrument holding device for holding instrument of different axial cross sections comprising a holding site unit, comprising a plurality of holding sites at predefined holding angles around an axis, the holding sites comprising different holding sizes for holding parts of instruments of different axial cross sections; and a coupling unit constituted to define a plurality of coupling angles around the axis with respect to a device support, the coupling unit being constituted to block rotational movement around the axis and to allow coupling of the holding site unit to the device support only at the plurality of coupling angles, when coupled to the device support.

Abstract: A swivel arm includes a fixing device for an instrument and at least one pivot, such that the swivel arm can be moved. At least one sensor on at least one pivot detects the position and/or movement of the at least one pivot. A controllable, passive actuator for the at least one pivot can brake and/or prevent a movement of the pivot. A control device guides the controllable, passive actuator on the basis of the position data and/or movement data transmitted from the at least one sensor and based on data of the target object. The passive actuator can be guided in such a way that an instrument connected to the swivel arm can perform only one or a number of predetermined movements.