A RFID-tag is a microelectronic circuit with transmit- and
receive-antenna, with a control-unit and a data- and energy-memory.
These circuits exist in several types of housings, for example as
stick-label, button, chip-card, stick, bracelet, screw or badge. The
housing is hermetically sealed and are very robust and resistant
against shock, vibration, pressure , chemicals and temperature.
There are two different systems of data medium: The first type can
be programmed only once (unique), the second one allows an exchange
or overwriting of the stored information (programmable transponder).
Additionally RFID-tags can be distinguished between active and
passive systems. Active systems take the required energy for the
transmission of information from a battery, passive ones from a
electromagnetic field (battery-free systems).
