{HEAD ~ RFID reader systems}, readers, components, software and {TAIL ~ methods} cause RFID tags to backscatter a combination made from at least portions of a first code and a second code, without transmitting any commands in the interim 
{ HEAD ~ RFID reader systems } , readers , components , software and { TAIL ~ methods } cause RFID tags to backscatter a combination made from at least portions of a first code and a second code , without transmitting any commands in the interim
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