What's RFID

RFID is a radio frequency identification device. RFID's commonly used to identify products, people, equipment or anything that needs a unique identification.

RFID comes in active and passive tags. Passive RFID tags does not require any power to work and active tags require some kind of battery or other power source to work. The advantage of active tags is the range for which it can be used. The problem with active tags is that it is limited to some enviroments due to the fragile setup.

The RFID tag requires a special reader to get the ID out of the tag. The reader is composed of electronics that drives an antenna to read the RFID tags.

The reading range of the reader determines the price of the reader. RFID reader with a range of 80cm could easily cost 2000USD with antenna.

RFID tag costs from 1USD and up. Active tags are much expeciver than passive tags. RFID tags can be found in all kinds of configurations: Keychain, implantable, wrist watch, access cards and much more.

RFID tags comes in different driving frequency. Ranging from 125Khz to high frequncy like 13.56Mhz. Its important that the RFID tags and the reader is talking the same "frequency".

You can read more about RFID tags on wikipedia.