This International Standard specifies the structure of the radio-frequency (RF) identification code for animals. RF identification of animals requires that the bits transmitted by a transponder are interpretable by a transceiver. Usually, the bit stream contains data bits, defining the identification code and a number of bits to ensure correct reception of the data bits. This International Standard specifies the structure of the identification code. This International Standard does not specify the characteristics of the transmission protocols between transponder and transceiver. These characteristics are the subject of IS0 11785. The structure may include a manufacturer’s code, the granting and use of a manufacturer’s code are the subject of ISO 24631.