Radio frequency identification

RFID is a means of uniquely identifying an item using radio waves. Data is exchanged between tags and readers and depending on the frequency, may or may not require line of sight. Common uses in today’s world include library books, toll passes and access ID cards.
Its use in the supply chain has been limited until recently. However, highprofile projects within the US military, Asda, Walmart and Tesco have increased awareness.
The system enables the simultaneous reading of multiple items as opposed to barcodes, which need to be read individually.

There are two types of RFID tags: those that are passive, have no power source, limited data storage capacity, are read only and have a limited read range, and those that are active, have their own power source, have a larger data-storage capacity, have a read/write capability and are readable from a greater distance. 

Passive tags hold little actual data but are able to identify an item to a database where more comprehensive data is stored. For example, a conveyor-based sortation system can identify the item and interrogate the database to receive routing instructions.