Double-proportional, two-magnet solenoids are used to effect strokes from the central position to the left or right end position. The armature's stroke motion happens the result of the electromagnetic force of the respective solenoid. External forces will reset the solenoids back into the central position. A double-proportional solenoid achieves twice the stroke (in mm) of a solenoid at the same size. The force of standard solenoids is flat to slightly rising during the first 80 percent of travel and rises to double the initial force in the final 20 percent of travel. The power transfer should be only in axial direction; lateral loads are to be avoided.