Abstract: Apparatus for actuating a security system which includes an actuator element, such as a key, in which is embedded a plurality of "Wiegand effect" magnetic rods forming at least one track of magnetically coded information. When the actuator element is inserted into a complementary element, a conditioning permanent magnet of a given polarity at the entrance of the complementary element switches each magnetic rod into a first magnetic state, then a drive permanent magnet of an opposite polarity disposed inwardly of the conditioning magnet switches each magnetic rod into a second magnetic state as the magnetic rod moves past it, causing a sharp voltage pulse to be generated within a sensor coil disposed close to the drive magnet and the magnetic rod being switched.