Radio-Frequency Identification

Radio-frequency identification, or RFID, is a technology that uses electromagnetic fields to automatically identify and track tags attached to objects, through a system of a small radio transponder tag, a reader and a transmitter; when an RFID reader's interrogation pulse triggers a tag, the tag transmits an identifying number back to the reader. The Soviet inventor Leon Theremin built an early passive, externally powered predecessor, a covert listening device called the Thing, in 1945, and the American engineer Mario Cardullo is credited with the first true ancestor of modern RFID, a patented passive transponder with onboard memory that he demonstrated to the New York Port Authority in 1971 for toll-collection use. Steven Depp, Alfred Koelle and Robert Freyman demonstrated modulated backscatter RFID tags at Los Alamos National Laboratory in 1973, a technique still used in contemporary RFID systems, and Charles Walton received the first patent explicitly associated with the RFID name in 1983.