A head retracting/latching apparatus for a hard or floppy disc drive includes a prong which is held during power-on conditions by an electromagnet at an unlatched position out of contact with the head assembly. When power is interrupted, the head assembly is energized to move the heads to a retracted...http://www.google.fr/patents/US4903157?utm_source=gb-gplus-shareBrevet US4903157 - Electromagnet-actuated head latching apparatus
