illustrated in fig1 in a de energized state if the electromagnet 1 is energized the armature 5 moves against the force of the resetting spring 7 towards the pole face 4 of the yoke body 1 1 and arrives into engagement therewith and is held there as long as the coil 1 2 is supplied with current if the electromagnet 1 is de energized and the electromagnet 2 is energized the armature moves first under the effect of the resetting force of the armed spring 7 in the direction of the pole face 4 of the yoke body 2 1 and thereafter as a result of its kinetic energy it moves beyond the position of equilibrium between the two resetting springs 7 and 8 subsequently the armature 5 in the course of its motion towards the pole face 4 of the yoke body 2 1 arrives under the effect of the magnetic force of the energized electromagnet 2 and is against the then effective force of the resetting spring 8 brought into engagement with the pole face 4 of the yoke body 2 1 corresponding to the cycle of the alternating energization of the electromagnets 1 and 2 the cylinder valve 9 may be accordingly opened and closed also referring to fig2 to prevent to a large extent the generation of eddy currents in the armature 5 made of a solid iron material the armature 5 is provided with a plurality of throughgoing apertures elongated slot shaped holes 10 whose depth dimension.