Abstract: An identification system to be used in association with a set of objects or persons whereby any member of the set may be automatically identified while the member is located within a predetermined interrogation zone, wherein the system has an oscillator and field coils by which an oscillating electromagnetic field is established in the interrogation zone, an identification tag associated with each member of the set of objects or persons, each tag having a core strip of magnetically responsive material of a type which abruptly reaches saturation at a predetermined level of magnetic field, an electromagnetic coil wrapped around the strip, a switch connected with the coil, electronic circuitry for controlling the opening and closing of the switch according to a sequence in timed relation to the half cycles of the electromagnetic field, which sequence defines an identification code for the tag, and a first antenna connected to the circuitry where the circuitry may be operated by power derived from the electromagn