Abstract: The locking device for locking of two relative to each other longitudinally moveable elements comprises an electromagnet including a magnetic yoke, an operating winding and a magnet armature. The operating winding and magnetic yoke are positionally fixed on the first element, while the magnet armature is fixed on the second element in respect to the longitudinal movement direction X. The magnet armature presses with one of its walls via a spring device against an opposing wall of the magnetic yoke. The walls of the magnet armature and magnetic yoke which lie opposed to each other are provided with an at least approximately form fitting register contour, so that magnet armature and magnetic yoke can be held in a locked position with respect to each other. For locking, the electromagnet is activated in the register position. Upon application of a predetermined amount of force in the longitudinal direction upon the first or second element the locking position can be release or disengaged.