Abstract: A synchronized communication system for communicating signals into and from a medium is disclosed. The communication system utilizes a transmitter located at a central station external to the medium, which transmits a low frequency synchronization signal into the medium. Transceivers located within the medium receive the low frequency synchronization signal and send information radio signals synchronized with the low frequency synchronization signal to a receiver located at the central station. Zone transceivers are located within the medium to receive and retransmit the synchronization signal at the low frequency within a zone. The zone transceivers also receive information signals from transceivers in the zone and transmit zone information radio signals to the central station containing information corresponding to the information received from the transceivers in the zone.

Abstract: A radio frequency identification (RFID) system is disclosed. The RFID system may include a plurality of antenna systems. Each pair of antenna systems may form an interrogation zone or write zone. A power splitter, switch, multiplexer or the like may alternately drive each antenna system of each pair of antenna systems to expand the interrogation zone or write zone for a selected or given power or to reduce a signal strength or power to transmit over a predetermined range of the interrogation or write zone.

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