This International Standard applies to interfaces between low-voltage switchgear, controlgear, and controllers (e.g. programmable controllers, personal computers, etc.). This standard does not apply to higher level industrial communication networks that have become known as fieldbuses and are considered by IEC subcommittee 65C. The purpose of this standard is to harmonize and define rules, components and requirements of a general nature applicable to industrial CDIs. Those features of the various CDI standards which can be considered as general have therefore been brought together in this part of IEC 62026.