When a direct current is laid on the solenoid coil, the solenoid shaft carries out a rotation by an angle preset by the system, the positioning angle. The size of this positioning angle does not depend on the length of the pulse, but is conditioned by the mode of construction. The shaft is fixed into the position reached by a built-in engagement mechanism even when the direct current is taken away. When the next pulse comes, the shaft rotates out of its current position of rest into the next position of engagement. The electrical positioning can take place in one or two directions of rotation. With a phased control a gradual rotational movement of the magnet shaft in one or two directions can be attained. A gradual manual adjustment by hand is always possible in both directions as long as there is no voltage.