Passive RFID System Explained ...

DHS | Department of Homeland Security | Fact Sheet: Radio Frequency Identification Technology

... "In its simplest form in common use today, a passive RFID system works as follows: an RFID reader transmits via its antenna an electromagnetic radio frequency signal to a passive RFID tag. The reader receives information back from the tag and sends it to a computer that controls the reader and processes the information that has been retrieved from the tag. " ...