For more information on Interrogator Commands, visit Gen2 Reader Commands and Q Parameter.
Generation 2 interrogators support these interrogator commands and also tag management functions, such as AB symmetry and sessions.
AB symmetry replaced the Gen 1 technique of “putting tags to sleep” after being interrogated. AB symmetry allows tags to be flagged with an identifier to ease counting. If a tag that was flagged as an A gets counted, it then becomes flagged with a B until it is counted again, at which time it will be flagged with an A. This technique eliminates problems with tags that cannot “wake up” or are slow to wake up for the next round of inventory.
Gen 2 tags support four sessions. This function is used when more interrogators or groups of interrogators interrogate the same group of tags. A tag would use each session to communicate with one interrogator or group of interrogators. This way, if a tag communicates with one interrogator and has been flagged with a B, for instance, a second interrogator communicating with the tag will use a second session with its own A and B flags. This will prevent the interrogators from interfering with each other’s inventory rounds and avoid confusion that may cause an interrogator to count a tag twice.