E164norm

E164norm is a term sometimes used in telecommunications to refer to the normative aspects of the ITU-T E.164 standard in practice, or to the set of rules used to normalize, format, and validate E.164 numbers across systems. The official ITU-T recommendation for international numbering is E.164. It defines the structure of international public telecommunication numbers, consisting of a country calling code followed by the national significant number, for a maximum total length of 15 digits. Numbers are typically written in international notation with a leading plus sign, e.g., [phone], while older or local systems may use an international trunk prefix or no prefix at all.

E164norm, as a concept, encompasses the agreed normative rules applied when converting between representations, such as removing punctuation and spaces, ensuring the number contains only digits plus an international prefix, and validating length and dialability according to E.164 constraints. In practice, normalization is important for call routing, directory services, billing, and number portability, particularly in VoIP and mobile networks.

The standard is complemented by other ITU-T recommendations, notably E.123 for formatting and E.164 in combination with national numbering plans. While not an official ITU-T term, E164norm appears in some engineering and data-management contexts to denote the standardized, interoperable representation of telephone numbers in E.164 form.

Common characteristics include: total digit length up to 15; country code between 1 and 3 digits; national significant number that varies by country; canonical form usually starts with a plus sign followed by digits.

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