ISO/IEC 15693

ISO/IEC 15693 is an international standard that defines the communication protocol for vicinity cards, which are contactless identification cards designed for longer read ranges compared to their close-coupling cousins. Ratified by the International Organization for Standardization and the International Electrotechnical Commission, this standard operates in the high-frequency band at 13.56 MHz, the same frequency used by many other RFID and NFC standards but optimized for different performance characteristics. The physical layer of ISO/IEC 15693 uses magnetic induction coupling between the reader antenna and the card. The reader generates an electromagnetic field that powers the passive tag and enables bidirectional communication. Data transmission from reader to card uses amplitude shift keying or pulse position modulation at rates of 1.65 kbit/s or 26 kbit/s, while the card responds back to the reader using load modulation at 6.62 kbit/s or 26 kbit/s. This asymmetric communication allows the system to balance power transfer with data throughput efficiently. One of the key features of ISO/IEC 15693 is its anticollision mechanism, which allows multiple cards to be read simultaneously within the reader's field. The standard implements a slotted approach where the reader can inventory multiple tags by using unique identifier-based arbitration. When multiple tags respond, the reader systematically identifies each one by progressively narrowing down which tags should respond in subsequent time slots, ensuring all cards in the field can be reliably detected without interference. Typical read ranges for ISO/IEC 15693 systems extend up to 1.5 meters, though practical implementations often achieve 30 to 50 centimeters depending on antenna design and power output. This longer range compared to ISO/IEC 14443 proximity cards makes vicinity cards ideal for applications where users cannot easily present their card directly to a reader. Common applications include library book management systems, supply chain tracking, ski lift access control, industrial asset tracking, and pharmaceutical authentication. The standard's robust anticollision capabilities make it particularly suitable for scenarios where multiple items need to be scanned quickly, such as inventory counts or batch processing in warehouses.