In the latest version of the 902 atlas, 902 represents the version number of the atlas. According to the query of relevant public information, the 902 atlas is an electrical engineering atlas, which contains graphic symbols and schematic diagrams of various electrical components, equipment and circuits commonly used in power systems. In the 902 atlas, 902 represents the diagram The version number of the set. Atlases 903 and 904 are also electrical engineering atlases, representing different version numbers respectively.