There are three types of RFID tags available. The first type is Active Tags. Active tags have a power source (battery) that periodically sends its ID to the reader. These tags are used for extremely long range applications (for example on shipping containers) where consistent inventory needs to be maintained. Active tags have a life span, typically a few years depending on the type of battery installed, and are the most costly of the tag types. The second type is called Semi-Passive Tags. Semi-Passive Tags are a combination of both technologies. They are smaller, light weight, and use a battery to power the electronic logic and they reflect the reader signal in order to transmit data.  Semi-passive tags may also be used as data loggers to capture data over a predetermined time period. They have a longer battery life than active tags, but shorter read range (typically only 20-200 ft). The last type is Passive Tags. Passive tags have no battery so they rely on energy from the reader to send and receive a signal. The reader sends electromagnetic waves to the tag’s antenna. Using energy from these waves, tags broadcast a signal known as backscatter back to the reader. Passive tags are used in a wide variety of applications due to their low cost and variety of tag options that are available.