An RFID system has three basic components: tags, which contain tiny semiconductor chips and miniaturized antennas inside some form of packaging; readers, which are composed of an antenna that communicates with the RFID tags and an electronics module networked to the host computer; and a host computer, which processes the data readers collect from the tags. Correctional facilities in California, Michigan, Illinois, and Ohio are already using an RFID tracking system. Transmitters worn by inmates and officers send unique radio signals every 2 seconds, enabling the system to pinpoint the wearer's location and track and record inmate and staff movements in the facility. The U.S. Department of Homeland Security uses RFID technology to improve security at U.S. borders and ports of entry. RFID technology can locate, track, and authenticate the movements of people and objects as they enter and depart the United States. Under the Container Security Initiative announced in 2002, gamma or X-ray imaging and radiation detection equipment is being used to examine cargo containers before they are shipped to the United States. Although law enforcement agencies have not made extensive use of RFID technology because of privacy concerns, applications have been in three main areas: evidence handling and property control, tracking stolen vehicles, and enhancing officer safety by tracking officers' locations throughout their shifts. Privacy concerns have focused on secret and intrusive uses of RFID that jeopardize individual privacy, reduce or eliminate consumer anonymity, and threaten civil liberties. These issues are being addressed by legislators.