RFID tags can be classified into two categories such as active and passive tags. Active tags have built-in batteries but passive tags do not include their own power supply. When electrical signal enters into the antennas, it provides the passive tags with the power to transmit a response.
The response of the passive tag is brief. It is just an ID number. Lack of an on-board power supplies denotes that the device is very small. You may search for the RFID chip timing New Haven Connecticut on the Internet to get more information on this regard.