An endovascular laser treatment device designed to be used with an optical fiber to treat venous diseases such as varicose veins is provided. The buoyant structure having a main deck, a moon pool, and propellers attached to the planar keel, which are operated by a motor or a generator. The differential amplifier amplifies a difference between the voltage received by the one input terminal and the voltage received by the other and output as a control voltage. To facilitate the throughput of data, the non-selected peripheral devices may only provide logic zero to the OR gate. A measure for the rounding for velocity profiles may be predefined separately for the angle axes and the linear axes. The inner member and the outer member include guide surfaces through which the outer member is guided to move in the axial direction through the balls.