a system for tracking items using passive rfid tags utilizes separate data and power frequencies . within an area in which the items are located , one or more data readers are provided but many more separate power modules are distributed through the space , for powering up the tags . with the power nodes distributed , the tags are powered from a relatively short distance , enabling the tags to transmit through a greater distance . one or more of the readers can include a power - node control which sends an rf signal to control on / off status of specific power nodes within the area , so that power nodes can be activated zone by zone , to thereby permit the reader to determine location by zone of products as their rfid tags are read .