Methods and apparatuses to identify devices

• US 8,102,244 B2
• Filed: 08/09/2004
• Issued: 01/24/2012
• Est. Priority Date: 08/09/2003
• Status: Active Grant

• Current Assignee: RUIZHANG TECHNOLOGY LIMITED COMPANY
• Original Assignee: Alien Technology Corporation
• Inventors: Smith, John Stephen
• Primary Examiner(s): Nguyen, Nam V
• Application Number:
  US10/915,725
• Publication Number:
  US 20050263591A1
• Time in Patent Office: 2,724 Days
• Field of Search: 340/10.2, 340/10.1, 340/10.33, 340/10.4, 340/10.5, 340/870.2, 340/572.1, 235/385, 235/375, 235/380, 370/312, 370/328, 370/349, 713/202, 455/515
• US Class Current: 340/10.2
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10039 interrogator driven, i.e. synchronous
• CPC Class Codes: G06K 7/10059 transponder driven
• CPC Class Codes: G06K 7/10346 the antenna being of the far field type, e.g. HF types or dipoles
• CPC Class Codes: G06K 7/10366 the interrogation device being adapted for miscellaneous applications
• CPC Class Codes: G08B 13/2485 Simultaneous detection of multiple EAS tags

Abstract

An apparatus and method to identify devices including a first set of commands to identify devices in a first state and a second set of commands to identify devices in a second state, wherein devices identified in the first state are placed in the second state and devices identified in the second state are placed in the first state.

Claims

1. A method for identifying tags, the method comprising:

issuing a first set of commands to identify a first plurality of tags in a first state, wherein, as a result of identifying the first plurality of tags in the first state, the first plurality of tags which are identified in the first state are placed in a second state; and

issuing a second set of commands to identify a second plurality of tags in the second state, wherein, as a result of identifying the second plurality of tags in the second state, the second plurality of tags which are identified in the second state are placed in the first state, wherein at least one of the first set of commands that contains a first parameter associated with the first state causes the first plurality of tags to perform an operation that is identical to the operation performed by the second plurality of tags in response to at least one of the second set of commands that contains a second parameter associated with the second state, wherein the first state and the second state are not the same.

2. A method as in claim 1 wherein issuing the first set of commands and issuing the second set of commands is performed without requiring that an interrogator know that it has placed certain tags in the first state or the second state.

3. A method as in claim 1, wherein the first set of commands is transmitted in a radio frequency band between 902-928 MHz.

4. A method as in claim 1, wherein the issuing the first set of commands comprises frequency hopping.

5. A method as in claim 1, wherein the issuing the first set of commands includes initiating a half-duplex communication.

6. A method for identifying tags, the method comprising:

issuing a set of commands capable of being received by a group of tags, the set of commands including at least a first command which causes an identified tag which is in a first state to be placed into a second state and a second command which causes an identified tag which is in the second state to be placed into the first state;

receiving identification information from at least one tag in response to the set of commands wherein the issuing is performed without attempting to place the group of tags in a state upon initially issuing the set of commands, wherein at least one of the set of commands containing a first parameter associated with the first state causes at least one tag in the first state to perform an operation that is identical to the operation performed by at least one tag in the second state in response to at least one of the set of commands containing a second parameter associated with the second state wherein the first state and the second state are not the same.

7. A method as in claim 6 wherein the identification information comprises an electronic product code.

8. A method as in claim 6 wherein the identification information comprises a checksum.

9. A method as in claim 6 wherein the identification information comprises a pseudorandom number.

10. A method of identifying tags, the method comprising:

issuing a first set of commands of a first type to identify tags in a first group of tags which are in a first state, wherein a first command in the first set of commands of the first type causes addressed tags to be placed in a second group of tags, which are in a second state, which are addressable by a second set of commands of a second type, wherein the first group of tags do not respond to the second set of commands of the second type; and

issuing the second set of commands of the second type to identify tags in the second group of tags in the second state, wherein a second command in the second set of commands of the second type causes addressed tags to be placed in the first group of tags which respond to the first set of commands of the first type and wherein the second group of tags do not respond to the first set of commands of the first type, wherein at least one of the first set of commands of the first type to identify tags in the first group of tags that contains a first parameter associated with the first state causes the first group of tags to perform an operation that is identical to the operation performed by the second group of tags in response to at least one of the second set of commands that contains a second parameter associated with the second state, wherein the first state and the second state are not the same.

11. A method as in claim 10 wherein a third group of tags in a third state are responsive to either the first set of commands of the first type or the second set of commands of the second type, the method further comprising:

issuing the first set of commands of the first type to identify tags in the third group of tags which are in the third state, wherein the first command in the first set of commands of the first type causes addressed tags to be placed in the second group of tags in the second state; and

issuing the second set of commands of the second type to identify tags in the third group of tags which are in the third state, wherein the second command in the second set of commands of the second type causes addressed tags to be placed in the first group of tags in the first state.

12. A method as in claim 10, further comprising:

issuing a third command in the first set of commands of the first type to address tags in the first group of tags in the first state, wherein the third command in the first set of commands of the first type causes addressed tags to be placed in the third group of tags in the third state; and

issuing a fourth command in the second set of commands of the second type to address tags in the second group of tags in the second state, wherein the fourth command in the second set of commands of the second type causes addressed tags to be placed in the third group of tags in the third state.

13. A method as in claim 12 wherein the third command in the first set of commands causes only a single addressed tag in the first group of tags to be placed in the third group of tags and the fourth command in the second set of commands causes only a single addressed tag in the second group of tags to be placed in the third group of tags.

14. A method as in claim 10 wherein the first command in the first set of commands causes only a single addressed tag in the first group of tags to be placed in the second group of tags and the second command in the second set of commands causes only a single addressed tag in the second group of tags to be placed in the first group of tags.

15. A method for identifying items, comprising:

sending a first interrogation signal of a first type to a plurality of items to be identified, the plurality of items in a first state;

classifying those of the plurality of items to be identified which respond to the first interrogation signal of the first type;

sending one or more subsequent interrogation signals of the first type to at least some of those of the plurality of items to be identified which responded to the first interrogation signal of the first type;

sub-classifying those of the plurality of items to be identified which respond to the one or more subsequent interrogation signals of the first type until each sub-class has a single member;

identifying each of those of the plurality of items to be identified which is the single member of the each one of the sub-classes;

changing the state of the identified items to a second state, the second state preventing the identified items from responding to interrogation signals of the first type and enabling the identified items to respond to interrogation signals of a second type, wherein at least one of the interrogation signals of the first type containing a first parameter associated with the first state causes the plurality of items in the first state to perform an operation that is identical to the operation performed by the plurality of items in the second state in response to at least one of the interrogation signals of the second type that contains a second parameter associated with the second state, wherein the first state and the second state are not the same;

interrogating, classifying and identifying those of the plurality of items to be identified which remain in the first state, with interrogation signals of the first type; and

returning the plurality of items in the second state to the first state.

16. A method performed by a tag, the method comprising:

receiving at the tag in a first state, a first set of commands to identify the tag in the first state, wherein, as a result of being identified, the tag in the first state is placed in a second state;

receiving at the tag in the second state, a second set of commands to identify the tag in the second state, wherein, as a result of being identified, the tag in the second state is placed in the first state, wherein at least one of the first set of commands that contains a first parameter associated with the first state causes the tag to perform an operation that is identical to the operation performed by the tag in the second state in response to at least one of the second set of command that contains a second parameter associated with the second state, wherein the first state and the second state are not the same.

17. A method as in claim 16, wherein the first set of commands is received in a radio frequency band between 902-928 MHz.

18. A method as in claim 16, wherein the first set of commands is received in a frequency hopping band of 902-928 MHz.

19. A method as in claim 16, wherein the tag comprises a single chip.

20. A method performed in a tag, the method comprising:

receiving at a tag in a first state a first set of commands of a first type to identify the tag in a first group of tags in the first state, wherein a first command in the first set of commands of the first type causes the tag in the first state to be placed in a second state in a second group of tags in the second state, which are addressable by a second set of commands of a second type, wherein the second group of tags in the second state do not respond to the first set of commands of the first type; and

receiving at a tag in the second state the second set of commands of the second type to identify the tag in the second group of tags in the second state, wherein a second command in the second set of commands of the second type causes the tag in the second state to be placed in the first state in the first group of tags in the first state, which are addressable by the first set of commands of the first type, wherein the first group of tags in the first state do not respond to the second set of commands of the second type, wherein at least one of the first set of commands that contains a first parameter associated with the first state causes the first group of tags to perform an operation that is identical to the operation performed by the tags in the second state in response to at least one of the second set of commands containing a second parameter associated with the second state, wherein the first state and the second state are not the same.

21. The method of claim 20 further comprising:

receiving at a tag in a third state the first set of commands of the first type to identify the tag in a third group of tags in the third state, wherein the first command in the first set of commands of the first type causes the tag in the third state to be placed in the second state in the second group of tags; and

receiving at the tag in the third state the second set of commands of the second type to identify the tag in the third group of tags which are in the third state, wherein the second command in the second set of commands of the second type causes the tag to be placed in the first state in the first group of tags.

22. The method of claim 20, further comprising:

receiving at the tag in the first state a third command in the first set of commands of the first type, wherein the third command in the first set of commands of the first type causes the tag to be placed in the third state in the third group of tags; and

receiving at the tag in the second state a fourth command in the second set of commands of the second type, wherein the fourth command in the second set of commands of the second type causes the tag to be placed in the third state in the third group of tags.

23. A method performed in a tag, comprising:

receiving a radio frequency signal from a reader, the signal being modulated with interrogation data comprising identification data, wherein

the interrogation data comprises a first set of commands of a first type to identify tags in a first group of tags which are in a first state, wherein a first command in the first set of commands of the first type causes addressed tags to be placed in a second group of tags, which are in a second state, which are addressable by a second set of commands of a second type, wherein the first group of tags do not respond to the second set of commands of the second type; and

wherein

the interrogation data further comprises the second set of commands of the second type to identify tags in the second group of tags in the second state, wherein a second command in the second set of commands of the second type causes addressed tags to be placed in the first group of tags which respond to the first set of commands of the first type and wherein the second group of tags do not respond to the first set of commands of the first type, wherein at least one of the first set of commands of the first type containing a first parameter associated with the first state causes the first group of tags in the first state to perform an operation that is identical to the operation performed by the second group of tags in the second state in response to at least one of the second set of commands of the second type that contains a second parameter associated with the second state, wherein the first state and the second state are not the same, and wherein the identification data are associated with at least a portion of an identification code;

detecting the identification data associated with at least the portion of the identification code;

comparing the identification data to determine if the identification data matches the at least the portion of the identification code imbedded in a memory in the tag;

generating a response code if the identification data matches the at least a portion of the identification code imbedded in the memory of the memory in the tag;

modulating the response code onto a radio frequency signal; and

transmitting the response code to the reader.

24. An identification system, comprising:

a plurality of identification tags in a first state, each of the plurality of identification tags comprising;

a memory having an imbedded identification code;

a first receiver to receive a first interrogation signal of a first type, to receive one or more subsequent interrogation signals of the first type, and to receive a state command which places the identification tag in a temporary second state wherein the identification tag is not responsive to interrogation signals of the first type and is only responsive to interrogation signals of a second type, the first interrogation signal having first identification data;

a correlator to compare the first identification data in the first interrogation signal of the first type with at least a portion of the imbedded identification code, and to compare second identification data in the one or more subsequent interrogation signals of the first type with one or more greater portions of the imbedded identification code;

a first controller to determine when to send a first response signal if the first identification data in the first interrogation signal of the first type matches the at least a portion of the imbedded identification code, and to determine when to send one or more subsequent response signals if the second identification data in the one or more subsequent interrogation signals of the first type match the one or more greater portions of the imbedded identification code; and

a first transmitter to send the first response signal and to send the one or more subsequent response signals; and

a reader, comprising;

a second transmitter to send the first interrogation signal of the first type to the plurality of identification tags, to send the one or more subsequent interrogation signals of the first type to the plurality of identification tags, and to send the state command to the plurality of identification tags which places at least some of the plurality of identification tags in the temporary second state wherein the at least some of the plurality of identification tags are not responsive to encoded interrogation signals of the first type and are only responsive to encoded interrogation signals of a second type;

a second receiver to receive a plurality of the first response signals from the at least some of the plurality of identification tags, the plurality of the first response signals being grouped into a first plurality of time periods, the second receiver to receive a plurality of each of the one or more subsequent response signals from the at least some of the plurality of identification tags, each of the plurality of the one or more subsequent response signals being grouped into one or more subsequent pluralities of time periods;

a processor to determine if more than one of the plurality of first response signals from the at least some of the plurality of identification tags have been received during a single time period of the first plurality of time periods and to determine if more than one of the plurality of one or more subsequent response signals from the at least some of the plurality of identification tags have been received during a single time period of the subsequent plurality of time periods of each of the one or more subsequent response signals from the at least some of the plurality of identification tags, wherein

the second transmitter sends the one or more subsequent interrogation signals of the first type to the at least some of the plurality of identification tags whose first encoded response signal has been received during the single time period of the plurality of time periods, the subsequent interrogation signal of the first type being adapted to evoke the subsequent response signals from all of the at least some of the plurality of identification tags which are separated in time, wherein

the processor uniquely identifies the all of the at least some of the plurality of identification tags whose subsequent response signals have been separated in time, and wherein

the second transmitter sends the command signal which places the identification tags in the temporary second state, to the all of the at least some of the plurality of identification tags which have been uniquely identified, wherein at least one of the interrogation signals of the first type containing a first parameter associated with the first state causes the plurality of identification tags in the first state to perform an operation that is identical to the operation performed by the plurality of identification tags in the temporary second state in response to at least one of the interrogation signals of the second type containing a second parameter associated with the temporary second state, the first state and the second state are not the same.

25. An apparatus to identify tags, the apparatus comprising:

a processor;

a transmitter coupled with the processor, the transmitter to impress identification data upon a signal that may be transmitted to a plurality of tags;

an antenna coupled with the transmitter, the antenna adapted to transmit the identification data to the plurality of tags, the identification data to compare with at least a portion of an identification code, wherein

the transmitter is configured to issue a first set of commands of a first type to identify tags in a first group of tags which are in a first state, wherein a first command in the first set of commands of the first type causes addressed tags to be placed in a second group of tags, which are in a second state, which are addressable by a second set of commands of a second type, wherein the first group of tags do not respond to the second set of commands of the second type; and

wherein

the transmitter is configured to issue the second set of commands of the second type to identify tags in the second group of tags in the second state, wherein a second command in the second set of commands of the second type causes addressed tags to be placed in the first group of tags which respond to the first set of commands of the first type and wherein the second group of tags do not respond to the first set of commands of the first type, wherein at least one of the first set of commands that contains a first parameter associated with the first state causes the first group of tags to perform an operation that is identical to the operation performed by the second group of tags in response to the second set of commands containing a second parameter associated with the second state, wherein the first state and the second state are not the same;

a receiver coupled with the processor, the receiver to receive at least one response from the plurality of tags, and wherein

the processor is configured to identify the at least one response from the plurality of tags.

26. A tag, comprising:

an antenna to receive a radio frequency signal from a reader;

the signal being modulated with interrogation data comprising first identification data from the reader;

a receiver coupled with the antenna to detect the interrogation data comprising the first identification data from the reader;

a memory containing an identification code;

a processor coupled with the receiver and the memory, the processor to process the identification data and determine if the first identification data in the interrogation data matches at least a portion of the identification code contained in the memory, wherein the processor generates a response code; and

a transmitter coupled with the processor, the transmitter adapted to modulate the response code onto a radio frequency signal, wherein the tag transmits the response code to the reader and wherein

the processor is configured to respond to a first set of commands of a first type to identify tags in a first group of tags which are in a first state, wherein a first command in the first set of commands of the first type causes addressed tags to be placed in a second group of tags, which are in a second state, which are addressable by a second set of commands of a second type, wherein the first group of tags do not respond to the second set of commands of the second type; and

wherein

the processor is configured to respond to the second set of commands of the second type to identify tags in the second group of tags in the second state, wherein a second command in the second set of commands of the second type causes addressed tags to be placed in the first group of tags which respond to the first set of commands of the first type and wherein the second group of tags do not respond to the first set of commands of the first type, wherein at least one of the first set of commands that contains a first parameter associated with the first state causes the first group of tags to perform an operation that is identical to the operation performed by the second group of tags in response to at least one of the second set of commands containing a second parameter associated with the second state, wherein the first state and the second state are not the same.

27. An identification system, comprising:

a plurality of identification tags in a first state, each of the plurality of identification tags comprising;

means for imbedding an identification code;

means for receiving a first interrogation signal of a first type having first identification data;

means for determining if a match exists between the first identification data in the first interrogation signal of the first type and at least a portion of the imbedded identification code;

means for determining when to send a first response signal when the first identification data in the first interrogation signal of the first type matches the at least a portion of the imbedded identification code;

means for sending the first response signal;

means for receiving a subsequent interrogation signal of the first type having second identification data to compare with a greater portion of the imbedded identification code;

means for determining if a match exists between the second identification data in the subsequent interrogation signal of the first type and the greater portion of the imbedded identification code;

means for determining when to send a subsequent response signal if the subsequent interrogation signal of the first type matches the greater portion of the imbedded identification code;

means for sending the subsequent response signal;

means for receiving an command which places the identification tag in a temporary second state wherein the identification tag is not responsive to interrogation signals of the first type and is only responsive to interrogation signals of a second type; and

means for automatically returning the identification tag to the first state; and

a reader, comprising;

means for sending the first interrogation signal of the first type to the plurality of identification tags;

means for receiving a plurality of the first response signals from at least some of the plurality of identification tags, the plurality of the first response signals being grouped into a plurality of time periods;

means for determining if more than one of the first response signals from the at least some of the plurality of identification tags has been received during a single time period of the plurality of time periods;

means for sending a subsequent interrogation signal of the first type to the at least some of the plurality of identification tags whose first response signal has been received during the single time period of the plurality of time periods, the subsequent interrogation signal of the first type being adapted to evoke subsequent responses from all of the at least some of the plurality of identification tags which are separated in time;

means for uniquely identifying the all of the at least some of the plurality of identification tags whose subsequent responses have been separated in time;

means for sending the command signal which places the identification tags in the temporary second state, to the all of the at least some of the plurality of identification tags which have been uniquely identified, wherein at least one of the interrogation signals of the first type that contains a first parameter associated with the first state causes the plurality of identification tags in the first state to perform an operation that is identical to the operation performed by the identification tags in the temporary second state in response to at least one of the interrogation signals of the second type containing a second parameter associated with the second state, wherein the first state and the second state are not the same.

28. An apparatus to identify tags, the apparatus comprising:

means for issuing a first set of commands to identify tags in a first state, wherein, as a result of identifying the tags in the first state, the tags which are identified in the first state are placed in a second state; and

means for issuing a second set of commands to identify tags in the second state, wherein, as a result of identifying the tags in the second state, the tags in the second state are placed in the first state, wherein at least one of the first set of commands that contains a first parameter associated with the first state causes the plurality of tags to perform an operation that is identical to the operation performed by the second plurality of tags in response to at least one of the second set of commands that contains a second parameter associated with the second state, wherein the first state and the second state are not the same.

29. The apparatus as in claim 28 wherein the means for issuing the first set of commands and the means for issuing the second set of commands have no memory of which tags have been placed in the first state or the second state.

30. An apparatus to identify tags, the apparatus comprising:

means for issuing a set of commands capable of being received by a group of tags, the set of commands including at least a first command which causes an identified tag which is in a first state to be placed into a second state and a second command which causes an identified tag which is in the second state to be placed into the first state;

means for receiving identification information from at least one tag in response to the set of commands wherein the issuing is performed without attempting to place the group of tags in a state upon initially issuing the set of commands, wherein at least one of the set of commands containing a first parameter associated with the first state causes at least one tag in the first state to perform an operation that is identical to the operation performed by at least one tag in the second state in response to at least one of the set of commands containing a second parameter associated with the second state, wherein the first state and the second state are not the same.

31. An apparatus to identify tags, the apparatus comprising:

means for processing interrogation data;

means for impressing the interrogation data upon a signal that may be transmitted to a plurality of tags;

means for transmitting the interrogation data to the plurality of tags, the interrogation data comprising first identification data associated with at least a portion of an identification code, wherein

the interrogation data comprises a first set of commands of a first type to identify tags in a first group of tags which are in a first state, wherein a first command in the first set of commands of the first type causes addressed tags to be placed in a second group of tags, which are in a second state, which are addressable by a second set of commands of a second type, wherein the first group of tags do not respond to the second set of commands of the second type; and

wherein

the interrogation data further comprises the second set of commands of the second type to identify tags in the second group of tags in the second state, wherein a second command in the second set of commands of the second type causes addressed tags to be placed in the first group of tags which respond to the first set of commands of the first type and wherein the second group of tags do not respond to the first set of commands of the first type, wherein at least one of the first set of commands containing a first parameter associated with the first state causes at least one tag in the first state to perform an operation that is identical to the operation performed by at least one tag in the second state in response to at least one of the second set of commands containing a second parameter associated with the second state, wherein the first state and the second state are not the same;

means for receiving at least one response from the plurality of tags.

32. A tag, comprising:

means for receiving at a tag in a first state, a first set of commands to identify the tag in the first state, wherein, as a result of being identified, the tag in the first state is placed in a second state

means for receiving at the tag in the second state, a second set of commands to identify the tag in the second state, wherein, as a result of being identified, the tag in the second state is placed in the first state, wherein at least one of the first set of commands containing a first parameter associated with the first state causes at least one tag in the first state to perform an operation that is identical to the operation performed by at least one tag in the second state in response to at least one of the second set of commands containing a second parameter associated with the second state, wherein the first state and the second state are not the same.

33. A tag, comprising:

means for receiving a set of commands capable of being received by a group of tags, the set of commands including at least a first command which causes an identified tag which is in a first state to be placed into a second state and a second command which causes an identified tag which is in the second state to be placed into the first state, wherein at least one of the set of commands containing a first parameter associated with the first state causes at least one tag in the first state to perform an operation that is identical to the operation performed by at least one tag in the second state in response to at least one of the set of commands containing a second parameter associated with the second state, wherein the first state and the second state are not the same;

means for sending identification information from in response to the set of commands wherein receiving the set of commands is performed without attempting to place the tag in an initial state before receiving the set of commands.

34. A tag, comprising:

means for receiving a radio frequency signal from a reader;

the signal being modulated with interrogation data having first identification data from the reader, wherein

the interrogation data comprises a first set of commands of a first type to identify tags in a first group of tags which are in a first state, wherein a first command in the first set of commands of the first type causes addressed tags to be placed in a second group of tags, which are in a second state, which are addressable by a second set of commands of a second type, wherein the first group of tags do not respond to the second set of commands of the second type, and wherein

the interrogation data further comprises the second set of commands of the second type to identify tags in the second group of tags in the second state, wherein a second command in the second set of commands of the second type causes addressed tags to be placed in the first group of tags which respond to the first set of commands of the first type and wherein the second group of tags do not respond to the first set of commands of the first type, wherein at least one of the first set of commands containing a first parameter associated with the first state causes at least one tag in the first state to perform an operation that is identical to the operation performed by at least one tag in the second state in response to at least one of the second set of commands containing a second parameter associated with the second state, wherein the first state and the second state are not the same;

means for detecting the interrogation data having the first identification data from the reader;

means for imbedding an identification code;

means for processing the interrogation data to determine if the first identification data in the interrogation data matches at least a portion of the identification code imbedded in the memory, wherein the processing generates a response code;

means for modulating the response code onto a radio frequency signal which may be transmitted to the reader;

means for transmitting the response code to the reader.

35. A machine recordable medium storing executable computer programming instructions, which when executed by a data processing system, cause the data processing system to perform a method for identifying tags, the method comprising:

issuing a first set of commands to identify tags in a first state;

issuing a second set of commands to identify tags in a second state, wherein, as a result of identifying tags in the first state, the tags which are identified in the first state are placed in the second state and wherein, as a result of identifying tags in the second state, the tags which are identified in the second state are placed in the first state, wherein at least one of the first set of commands containing a first parameter associated with the first state causes at least one tag in the first state to perform an operation that is identical to the operation performed by at least one tag in the second state in response to at least one of the second set of commands containing a second parameter associated with the second state, wherein the first state and the second state are not the same.

36. A machine recordable medium as in claim 35 wherein the issuing of commands is performed without requiring that an interrogator know that it has placed certain tags in first state or the second state.

37. A machine recordable medium storing executable computer programming instructions, which when executed by a data processing system, cause the data processing system to perform a method for identifying tags, the method comprising:

issuing a set of commands capable of being received by a group of tags, the set of commands including at least a first command which causes an identified tag which is in a first state to be placed into a second state and a second command which causes an identified tag which is in the second state to be placed into the first state, wherein at least one of the set of commands containing a first parameter associated with the first state causes at least one tag in the first state to perform an operation that is identical to the operation performed by at least one tag in the second state in response to at least one of the set of commands containing a second parameter associated with the second state, wherein the first state and the second state are not the same;

receiving identification information from at least one tag in response to the set of commands wherein the issuing is performed without attempting to place the group of tags in a state upon initially issuing the set of commands.

38. A machine recordable medium storing executable computer programming instructions, which when executed by a data processing system, cause the data processing system to perform a method for identifying tags, the method comprising:

issuing a first set of commands of a first type to identify tags in a first group of tags which are in a first state, wherein a first command in the first set of commands of the first type causes addressed tags to be placed in a second group of tags, which are in a second state, which are addressable by a second set of commands of a second type, wherein the first group of tags do not respond to the second set of commands of the second type;

issuing the second set of commands of the second type to identify tags in the second group of tags in the second state, wherein a second command in the second set of commands of the second type causes addressed tags to be placed in the first group of tags which respond to the first set of commands of the first type and wherein the second group of tags do not respond to the first set of commands of the first type, wherein at least one of the first set of commands containing a first parameter associated with the first state causes at least one tag in the first state to perform an operation that is identical to the operation performed by at least one tag in the second state in response to at least one of the second set of commands containing a second parameter associated with the second state, wherein the first state and the second state are not the same.

39. A machine recordable medium storing executable computer programming instructions, which when executed by a data processing system, cause the data processing system to perform a method of identifying items, the method comprising:

sending a first interrogation signal of a first type to a plurality of items to be identified, the plurality of items in a first state;

classifying those of the plurality of items to be identified which respond to the first interrogation signal of the first type;

sending one or more subsequent interrogation signals of the first type to at least some of those of the plurality of items to be identified which responded to the first interrogation signal of the first type;

sub-classifying those of the plurality of items to be identified which respond to the one or more subsequent interrogation signals of the first type until each sub-class has a single member;

identifying each of those of the plurality of items to be identified which is the single member of the each one of the sub-classes;

changing the state of the identified items to a second state, the second state preventing the identified items from responding to interrogation signals of the first type and enabling the identified items to respond to interrogation signals of a second type, wherein at least one of the interrogation signals of the first type containing a first parameter associated with the first state causes at least one tag in the first state to perform an operation that is identical to the operation performed by at least one tag in the second state in response to at least one of the interrogation signals of the second type containing a second parameter associated with the second state, wherein the first state and the second state are not the same;

interrogating, classifying and identifying those of the plurality of items to be identified which remain in the first state, with interrogation signals of the first type; and

returning the plurality of items in the second state to the first state.

40. A machine recordable medium storing executable computer programming instructions, which when executed by a data processing system, cause the data processing system to perform a method of identifying a plurality of tags in a first state, the method comprising:

receiving at the plurality of tags a first interrogation signal of a first type having first identification data;

determining if a match exists between the first identification data in the first interrogation signal of the first type and a first segment of the unique identification codes in at least some of the plurality of tags;

sending a plurality of first response signals from the at least some of the plurality of tags when the first identification data in the first interrogation signal of the first type matches the first segment of the unique identification codes in the at least some of the plurality of tags, the plurality of first response signals distributed in a first plurality of time periods, each of the first plurality of time periods corresponding to a second segment of the unique identification codes in the at least some of the plurality of tags;

receiving at the at least some of the plurality of tags a subsequent interrogation signal of the first type having second identification data to compare with a greater segment of the unique identification codes in the at least some of the plurality of tags;

determining if a match exists between the second identification data in the subsequent interrogation signal of the first type and the greater segment of the unique identification codes in the at least some of the plurality of tags;

sending a plurality of subsequent response signals from the at least some of the plurality of tags when the second identification data in the subsequent interrogation signal of the first type matches the greater segment of the unique identification codes in the at least some of the plurality of tags, the plurality of subsequent response signals distributed in a plurality of subsequent time periods, the plurality of subsequent time periods corresponding to subsequent segments of the unique identification codes in the at least some of the plurality of tags;

detecting when only one of the plurality of subsequent response signals is sent in one of the plurality of subsequent time periods;

determining the unique identification code of the one of the plurality of tags whose subsequent response has been detected in one of the plurality of subsequent time periods;

placing the one of the plurality of tags whose unique identification code has been determined into a second state wherein the tag is not responsive to interrogation signals of the first type and is only responsive to interrogation signals of a second type, wherein at least one of the interrogation signals of the first type containing a first parameter associated with the first state causes at least one tag in the first state to perform an operation that is identical to the operation performed by at least one tag in the second state in response to at least one of the interrogation signals of the second type containing a second parameter associated with the second state, wherein the first state and the second state are not the same; and

returning the one of the plurality of tags to the first state.

41. A machine recordable medium storing executable computer programming instructions, which when executed by a data processing system, cause the data processing system to perform a method of identifying tags, the method comprising:

transmitting the interrogation data to the plurality of tags, the interrogation data comprising first identification data associated with at least a portion of an identification code, wherein

the interrogation data comprises a first set of commands of a first type to address tags in a first group of tags which are in a first state, wherein a first command in the first set of commands of the first type causes addressed tags to be placed in a second group of tags, which are in a second state, which are addressable by a second set of commands of a second type, wherein the first group of tags do not respond to the second set of commands of the second type, and wherein

the interrogation data further comprises the second set of commands of the second type to identify tags in the second group of tags in the second state, wherein a second command in the second set of commands of the second type causes addressed tags to be placed in the first group of tags which respond to the first set of commands of the first type and wherein the second group of tags do not respond to the first set of commands of the first type, wherein at least one of the first set of commands of the first type containing a first parameter associated with the first state causes at least one tag in the first state to perform an operation that is identical to the operation performed by at least one tag in the second state in response to at least one of the second set of commands of the second type containing a second parameter associated with the second state, wherein the first state and the second state are not the same;

receiving at least one response from the plurality of tags; and

identifying the at least one response from the plurality of tags.

42. A machine recordable medium storing executable computer programming instructions, which when executed by a data processing system, cause the data processing system to perform a method in a tag, the method comprising:

receiving at a tag in a first state, a first set of commands to identify the tag in the first state, wherein, as a result of being identified, the tag in the first state is placed in a second state; and

receiving at the tag in the second state, a second set of commands to identify the tag in the second state, wherein, as a result of being identified, the tag in the second state is placed in the first state, wherein at least one of the first set of commands containing a first parameter associated with the first state causes at least one tag in the first state to perform an operation that is identical to the operation performed by at least one tag in the second state in response to at least one of the second set of commands containing a second parameter associated with the second state, wherein the first state and the second state are not the same.

43. A machine recordable medium storing executable computer programming instructions, which when executed by a data processing system, cause the data processing system to perform a method in a tag having an identification code, the method comprising:

receiving a radio frequency signal from a reader, the radio frequency signal being modulated with interrogation data comprising first identification data associated with at least a portion of an identification code, wherein

the interrogation data comprises a first set of commands of a first type to identify tags in a first group of tags which are in a first state, wherein a first command in the first set of commands of the first type causes addressed tags to be placed in a second group of tags, which are in a second state, which are addressable by a second set of commands of a second type, wherein the first group of tags do not respond to the second set of commands of the second type; and

wherein

the interrogation data further comprises the second set of commands of the second type to identify tags in the second group of tags in the second state, wherein a second command in the second set of commands of the second type causes addressed tags to be placed in the first group of tags which respond to the first set of commands of the first type and wherein the second group of tags do not respond to the first set of commands of the first type, wherein at least one of the first set of commands containing a first parameter associated with the first state causes at least one tag in the first state to perform an operation that is identical to the operation performed by at least one tag in the second state in response to at least one of the second set of commands containing a second parameter associated with the second state, wherein the first state and the second state are not the same;

detecting the interrogation data from the reader;

processing the first identification data in the interrogation data to determine if the first identification data in the interrogation data matches at least a portion of the identification code imbedded in the memory, wherein the processing generates a response code;

modulating the response code onto a radio frequency signal which may be transmitted to the reader; and

transmitting the response code to the reader.

44. A tag comprising:

an antenna; and

a processor, and a memory coupled to the processor, wherein the processor is configured to receive a first set of commands to identify the tag in a first state, wherein, as a result of being identified, the tag in the first state is placed in a second state, to receive a second set of commands to identify the tag in the second state, wherein, as a result of being identified, the tag in the second state is placed in the first state, wherein at least one of the first set of commands containing a first parameter associated with the first state causes at least one tag in the first state to perform an operation that is identical to the operation performed by at least one tag in the second state in response to at least one of the second set of commands containing a second parameter associated with the second state, wherein the first state and the second state are not the same, wherein the processor and the memory are on a single chip.