| CPC G06K 19/07773 (2013.01) [G06K 19/0709 (2013.01)] | 14 Claims | 

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               1. A radio tag comprising: 
            a sensor input for receiving a sensed condition signal; 
                at least one antenna for receiving and/or transmitting radio power; 
                an energy harvesting circuit communicating with the at least one antenna to harvest radio power from the antenna and store the same; 
                a radio receiver communicating with the at least one antenna for extracting a query signal; and 
                a radio transmitter communicating with the at least one antenna to transmit an answer signal deriving power from the harvested radio power, the answer signal containing a value that changes based on the sensor input and the query signal. 
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