Randomized tag to portal communication system

A tag circuit for communicating with and furnishing identification to a monitoring station whenever said tag circuit comes within range of said monitoring station and independent of the simultaneous presence within said range of another tag circuit, said tag circuit comprising means for receiving from said monitoring station an interrogating signal containing a first code pattern when in range of said station, and means for responding to said interrogating signal, said last mentioned means comprising means for radiating a series of response signals each containing a predetermined second code pattern different from said first code pattern and identifiable with said tag circuit, and means for varying in at least a pseudorandom manner the intervals between successive response signals.

A tag circuit for communicating with and furnishing identification to a monitoring station whenever said tag circuit comes within range of said monitoring station and independent of the simultaneous presence within said range of another tag circuit, said tag circuit comprising means for receiving from said monitoring station an interrogating signal containing a first code pattern when in range of said station, means for testing said interrogating signal to determine whether or not said first code pattern corresponds to a preset interrogation code pattern, and means for responding to said interrogating signal only if said testing establishes such correspondence, said last mentioned means comprising means for radiating a series of response signals each containing a predetermined second code pattern different from said first code pattern and identifiable with said tag circuit, and means for varying in at least a pseudorandum manner the intervals between successive response signals.

A communication system for detecting whenever one or more of a plurality of independent tag circuits comes within range of a monitoring station and identifying such tag circuits as come within said range even though more than one tag circuit may come within said range at the same time, said system comprising means for disposition at said monitoring station for radiating an interrogating signal identifiable with said monitoring station;

• a plurality of tag circuits each containing means for receiving said interrogating signal whenever the respective tag circuit is within range of said monitoring station, and means for responding to said interrogating signal, said last mentioned means comprising means for radiating a series of response signals each containing a predetermined code pattern identifiable with the respective tag circuit, and means for varying in at least a pseudorandum manner the intervals between the successive response signals from each tag circuit;
• and further means for disposition at said monitoring station for receiving any signals that are within range of said station and rejecting any of said response signals that arrive at said monitoring station from one tag circuit at the same time as a response signal from another tag circuit.

A communication system for establishing simultaneous communication between an interrogating station and a plurality of transponder circuits, said system comprising means for disposition at said interrogating station for transmitting an interrogating signal;

• a plurality of transponder circuits each containing means for receiving said interrogating signal, and means for responding to said interrogating signal, said last mentioned means comprising means for transmitting a series of response signals each containing a predetermined code pattern associated with the respective transponder circuit, said code pattern being based upon a keying format such that if two different code patterns are summed at least some of the self-contained clock rate transitions disappear, and means for varying in at least a pseudorandom manner the intervals between the successive response signals from each transponder circuit;
• and further means for disposition at said interrogating station for receiving any signals that are transmitted by a transponder circuit and rejecting any of said response signals that arrive at said interrogating station from one transponder circuit at the same time as a response signal from another transponder circuit.