Patent ID: 8159332

Claim:
A radio-frequency identification (“RFID”) transponder the RFID transponder comprising: a receiver for receiving a plurality of temporally spaced interrogating signals from an RFID interrogator, wherein each of the plurality of temporally spaced interrogating signal includes a respective identifier; a memory array for storing first data, wherein the first data comprises a time stamp number of a first instance the RFID transponder was interrogated by the RFID interrogator and wherein the first data is indicative of an order of the temporally spaced interrogating signals; a signal processor that extracts the respective identifier; wherein the signal processor determines if the extracted identifier is different than the first data and if the RFID transponder was previously interrogated by the RFID interrogator; responsive to a determination that the extracted identifier is different than the first data and that the RFID transponder was previously interrogated by the RFID interrogator, the first data remains unchanged: and responsive to a determination that the extracted identifier is different than the first data and that the RFID transponder was not previously interrogated by the RFID interrogator, the first data is overwritten.