For HF few standards have to be considered. ISO/IEC 18000-3 defines three HF RFID systems as Modes 1, 2 and 3. Mode 1 is based on ISO/IEC 15693 and common in use. Mode 2 is far less important and rarely used. Mode 3 is based on the memory and command structures of ISO/IEC 18000-63. Further, the standard ISO/IEC 14443 is prevalently in use for identification cards. NFC transponders are transponders using the ISO/IEC 14443 (type 1, 2 and 4 tags) standard or the ISO/IEC 15693 standard (type 5 tags). NFC tags can be accessed with the same commands as ISO/IEC 14443 tags.