Patent ID: 6674359
Filing Date: 2004-01-06
Classification: G06K

Abstract:
A method of identifying several transponders located in the interrogation zone of an interrogator, comprising the steps of:providing an interrogator and a plurality of transponders in an interrogation zone for the interrogator, each transponder including an incrementable device for generating a partial address and having a predetermined capacity; sending an RF interrogation signal from the interrogator to the transponders, the RF interrogation signal containing energy pulses for generating a supply voltage in the transponders, causing the transponders to generate a partial address; comparing the partial address in each of the transponders with a unique address stored in each transponder with a transponder having said unique address corresponding to said partial address sending a response to the interrogator and a data message having an address uniquely identifying that transponder; responsive to having received a transponder response, the interrogator sending an RF response signal containing a signal section to be recognized by the responding transponder as a code string characterizing its address and a data section; sending in the data section an instruction to the responding transponder which places it in the condition in which on receiving an RF interrogation signal containing its address it does not react by sending its response signal; and then, upon failure to receive a response from a transponder, sending an RF interrogation signal from the interrogator on timeout of a time period during which the transponder is waiting for a transponder response for implementing an identification procedure by the interrogator containing at least one pulse which is used in the transponders to increment the partial address in the transponders in sequence, each transponder reacting by sending a signal in response to the partial address generated therein only when the partial address agrees with a corresponding section of its address.