Radio Frequency Identification (RFID) is used to track parts during manufacturing, in shops, and for equipment identification. They are also used for animal identification. A RFID system has two components: an RFID tag containing information and an RFID reader that can read the information. RFID components may use one of a number of frequencies, including the unregulated 120-150 kHz range that is commonly used for data collection in factories and animal identification, along with several radio frequencies in the ISM range. Another commonly used frequency for RFID tags is the 13.56 MHz band. RFID tags are usually passive and only activate when energized by a signal, but it is also possible to use powered tags that periodically broadcast an identification signal. Apart from discrete tags, RFID tags are also available on cards similar to credit cards or as key fobs used for personnel identification. Tags may be read only or have a read/write function that allows data to be added to the tag by the reader. RFID readers are commonly supplied in PCB form for incorporation into other equipment. Alternatively, customers can order a RFID housing designed to accommodate standard-size readers along with a small antenna. Manufacturers of RFID equipment include iDTRONIC and Codatex.