Radio frequency identification (RFID) is a short-range wireless technology able to track, mark, and identify everything from people to products. Available in several formats, each tag contains a single chip with a unique identification number and a radio transponder or receiver. The ubiquitous bar codes require line-of-sight scan, but RFID tags do not, so scan time is much faster. Another time-saver is the ability to read or scan multiple items at the same time. Readers, or interrogators, can be fixed in place or handheld, but their range is usually within several inches. Larger antennas and active tags with a battery to boost transmit power to a reader can be tracked from hundreds of feet away. Although RFID have many advantages over bar codes, the remaining barrier is cost. Passive tags can be purchased for as little as 25 cents in large quantities, but RFID cannot replace bar codes until the cost drops to five cents apiece, a prospect about which industry observers are skeptical. Nevertheless, RFID uses are continuing to expand across everyday uses. Motor vehicle departments in California and other states are offering RFID devices that, when affixed inside a windshield, automatically withdraw highway tolls from a credit card or bank account. Many trucks and cars use tag keys coded to work with the ignition lock on that vehicle, preventing theft. The U.S. government began integrating an RFID chip in all passports as of 2005, and it may not be long before drivers licenses carry such devices.