Abstract: The device comprises an electromagnet to the movable armature of which is integral a metal strap that supports, cantilever fashion, a shank provided with a plate. One part of the edge of the said plate is inserted in a slit machined in one extremity of a rod subjected to elastic means, guided in a way in which it slides, by a plate. The other extremity of the rod carries means for selecting a metal strap.With the electromagnet de-energized, the selection means do not intercept a butt provided on the metal strap but with the electromagnet excited, the selection means intercept the said butt and this cause the said strap to be raised and subsequently sent into operation.