ISO/IEC 18000-2:2009定义了在135 kHz以下工作的射频识别（RFID）设备的空中接口。ISO/IEC 18000-2:2009旨在为制定RFID应用标准的ISO委员会提供RFID设备的通用技术规范。ISO/IEC 18000-2:2009旨在实现兼容性，并鼓励产品在国际市场上的互操作性。ISO/IEC 18000-2:2009定义了用于询问器和标签之间通信的物理层，并进一步定义了空中接口中使用的通信协议。 ISO/IEC 18000-2:2009定义了两种类型的标签:A型和B型，它们仅因物理层不同而不同。两者都支持相同的资源清册（防冲突）和协议。 A类标签由询问器永久供电，包括在标签期间- 用于询问传输，并在125 kHz下运行。 B型标签由询问器供电，但在标签到询问器传输期间除外，其工作频率为125 kHz或134,2 kHz。

ISO/IEC 18000-2:2009 defines the air interface for radio frequency identification (RFID) devices operating below 135 kHz. The purpose of ISO/IEC 18000-2:2009 is to provide a common technical specification for RFID devices that can be used by ISO committees developing RFID application standards. ISO/IEC 18000-2:2009 is intended to allow for compatibility and to encourage inter-operability of products in the international marketplace. ISO/IEC 18000-2:2009 defines the physical layer used for communication between the interrogator and the tag and further defines the communications protocol used in the air interface. Two types of tag are defined by ISO/IEC 18000-2:2009: Type A and Type B, which differ only by their physical layer. Both support the same inventory (anti-collision) and protocol. Type A tags are permanently powered by the interrogator, including during the tag-to-interrogator transmission, and operate at 125 kHz. Type B tags are powered by the interrogator, except during the tag-to-interrogator transmission, and operate at 125 kHz or 134,2 kHz.