Technology RFID History RFID has a long history with the first practical application being developed in World War II, due to the need to remotely identify planes. This system was called IFF (Identification Friend or Foe) and embodied all the basic features of RFID. Civilian avaition has continually developed this technology to the point that aircraft can be automatically identified on radar screens with information about height, speed and direction able to be ascertained. It took the development of silicon circuits that were high speed, low cost and low power to widen the market for RFID technology. RFID tags contain an embedded microchip and radio transmitter. The microchip stores basic information about the tagged object, which is usually a product code and a unique serial number. In a typical situation, a reader transmits a request to a tag which replies with its identity, and any other relevant information. The data is then transmitted to a software application which analyzes the data. Passive and Active tags There are two main types of RFID tags: active and passive. Whether active or passive, a tag contains a digital identification code on a microchip which can be scanned by a reader. The difference in the tags comes from how the reading occurs. A passive tag is read when the RFID reader emits a signal which activates the tag. The tag is then able to respond to the reader. In contrast to this, an active tag (see image below) contains a battery continuously powering the tag. The battery allows the active tag to be able to emit a signal without having to be activated by the reader. 
Passive tags can have no battery (called pure passive), or a small one purely for running the electronics but not powering the transmitter (called active/passive). Both passive and active/passive tags have a short range, because of their reliance on energy in the reader's radio signal to power the transmitted reply. However, the advantages of purely passive tags are that they require no maintenance, are very robust and can be manufactured much more cheaply than the active type. The abilities of active tags can vary, but it is possible for an active tag to be programmable, reusable and able to store more data. However, these features increase the cost of the tags significantly. Active tags are required for applications that require data to be transmitted over long distances, or for more complex data to be stored and supplied.
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