(57) The invention relates to a ball lock, for instance for use in anti-shoplifting labels, which ball lock is uncoupled from the protective needle (9) by applying a composite magnetic field produced by two or more magnets(10) which, in a specific position and polarization, must be brought near the wafer, so as to exert a force perpendicular to an uncoupling part (3). When a magnetic field is applied at the wafer, produced by one or more magnets (10) which have not been properly placed or polarized, the ball lock will not uncouple the protective needle (9), because the uncoupling part (3) is then drawn askew.
In this ball lock the wafer need not be placed so as to be directed to this composite magnetic field of two or more magnets, because the uncoupling part (3) in the wafer can rotate such that the metal parts or the magnets (10) fastened thereon come to lie precisely opposite the proper magnets (10).