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What Is an RFID Transponder?

A key with an RFID transponder.
An RFID transponder can replace the hassle of stopping and paying tolls to access some roadways.
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  • Written By: Jeremy Laukkonen
  • Edited By: Allegra J. Lingo
  • Last Modified Date: 02 October 2014
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Radio frequency identification (RFID) can be used for a variety of different purposes, including supply chain management and collecting road tolls. An RFID transponder is typically designed to detect a radio signal from another device and return an expected response. In an RFID system, the transponder may be known as a tag, and the device that communicates with it is called a reader. There are three main types of RFID transponder, including passive, semi-passive and active. The main difference between these types of RFID transponder is that some can operate without a battery, while others require an internal source of power.

One benefit of RFID transponders is that they can be read indirectly, without any physical contact or even visual contact. Both readers and tags use radio signals, which are generally limited by distance rather than line of sight. A reader device will typically send an interrogation signal, which any tag in range can receive, process, and then reply to. This can allow for inventory management without the need to physically catalog items, or create a record of a driver passing through a toll zone without the car ever needing to stop.

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Passive RFID tags are typically able to operate without any internal battery source. This type of RFID transponder may be switched on and powered up by the electromagnetic radio waves sent by a reader. The power can then be used to process the signal and return a response. Since there is no battery source present in a passive RFID transponder, there may be less concern about the tag having a short operational lifespan.

Both semi-passive and active tags use some form of internal power source. Semi-passive tags typically require an external signal from a reader to activate, in much the same way as a passive RFID transponder. The presence of a battery source may greatly extend the transmission power, increasing the range and reducing the possibility of the tag being missed by a reader. Active tags also use an internal power supply, and will typically look for a reader signal in order to respond when needed.

Despite the potential benefits to supply chain management, transportation, payment systems, and other areas, there are potential problems with RFID transponders. Many people have raised concerns over security issues, especially in cases where an RFID transponder may be used to identify a person. Since communication between the tag and reader occurs over radio waves, the potential for signal interception and identify theft may be a possibility.

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