- This Recommendation provides the number structure and functionality for the four categories of numbers used for international public telecommunication geographic areas, global services, Networks and Groups of Countries (GoC). For each of the categories, it details the components of the numbering structure and the digit analysis required to successfully route the calls. Annex A provides additional information on the structure and function of international public telecommunication numbers (hereafter referred to as international E.164-numbers). Annex B provides information on network identification, service parameters, calling/connected line identity, dialling procedures and addressing for geographic-based ISDN calls. Specific E.164-based applications, which differ in usage, are defined in separate Recommendations.