RFID Reader: Radio Frequency Identification Technology

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. Passive tags do not have batteries and operate using the energy they receive from signals sent by a reader. " ...