A device for adjusting the armature stroke in a reversible linear drive unit comprising an excitation coil and an armature displaceable in the magnetic field of the excitation coil according to a linear oscillating motion at a predefined armature stroke. The device comprising systems for detecting the current armature position, systems for measuring the actual excitation coil current and systems for adjusting the excitation coil current in such a way that the armature is exactly supplied with electric energy for obtaining the aptitude of oscillations of the armature stroke during each half-wave of the armature motion.