This part of ISO 18185 specifies the air interface between electronic container seals and Reader/Interrogators of those seals. It is to be used in conjunction with the other parts of ISO 18185. This part of ISO 18185 describes the physical layer for supply chain applications of RFID for freight containers in accordance with the ISO 18185 series and ISO 17363, since it is expected that the implementation of these standards will face the same international conditions. However, each of these standards has its own unique requirements other than the physical layer. It is expected that RFID Freight Container Identification (as specified in ISO 10374 and ISO 17363), and electronic seals (as specified in the ISO 18185 series) will be able to use the same infrastructure, while recognizing that that there may be requirements for different frequencies for passive devices as opposed to the active devices identified in this part of ISO 18185. This part of ISO 18185 is applicable to all electronic seals used on freight containers covered by ISO 668, ISO 1496 (parts 1 to 5) and ISO 830 and should, wherever appropriate and practicable, be applied to freight containers other than those covered by the aforementioned International Standards.