The CCITT, recommends that the various ITU organs, as well as Administrations and recognized private operating agencies should use in their mutual relations: the units of the international system of units (SI) adopted by the General Conference of Weights and Measures (CGPM) and supported by the International Organization for Standardization (ISO); this systemis based on the rationalized form of electromagnetic and electrotechnical relations.
ITU-T B.3-1993 history
1993ITU-T B.3-1993 USE OF THE INTERNATIONAL SYSTEM OF UNITS (SI)