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Method and apparatus for efficiently querying and identifying multiple items on a communication channel

  • US 6,727,803 B2
  • Filed: 03/16/2001
  • Issued: 04/27/2004
  • Est. Priority Date: 03/16/2001
  • Status: Active Grant
First Claim
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1. A method for identifying each of a plurality of objects using an interrogation process on a single communication channel, wherein an interrogating device capable of simultaneously communicating with a plurality of objects to be identified has access to the single communication channel, each object to be identified contains within it an identification number in the form of a plurality of digits enumerated in a predetermined sequence, each object contains a push-counter capable of counting from zero up to at least the number of digits contained within the identification number times N−

  • 1, where N is the number of possible digit values, each object has the ability to communicate with the interrogating device and to provide predetermined responses to indicate the value of the digits contained in its respective identification number, wherein the responses for different values are such that they may be unambiguously discerned by the interrogating device even when two or more types of responses are returned simultaneously by the objects being interrogated, and wherein a response for a given value may be returned by two or more transponders and be distinguishable from the absence of any response, comprising the steps of;

    activating said plurality of objects, to enable them to participate in the interrogation process, interrogating a single digit within the predetermined sequence from all activated objects, to obtain a predetermined response from each of the plurality of objects indicative of the value of the digit being interrogated, recording the value of each predetermined response obtained in the step of interrogating, signaling each object with a non-zero push-counter value to add (N−

    1) to its push-counter when two or more possible response values are detected, signaling each object that responds with any but the highest valued currently available digit to add [(N−

    1)−

    digit value] to its push-counter when two or more possible response values are detected by the interrogating device, recording an incomplete sequence of identification digits received by the interrogating device since the last step of activating, signaling each object, which has a non-zero push-counter value to decrement its push-counter when one or more complete identification numbers are recorded and incomplete identification numbers remain to be completely identified, terminating the method if none of the objects respond to the interrogating device, recording complete identification numbers received, allowing each object to no longer respond to the interrogating device when complete identification is obtained, requiring each object with a zero push-counter value to respond to the interrogating device, and continuing the step of interrogating until a complete identification number is obtained for each object.

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