Nummerplaner

Nummerplaner are systems used in telecommunications to allocate telephone numbers within a country or region. They define the structure, length, and allocation rules of numbers, enabling routing of calls, service identification, and number portability. A nummerplan typically specifies the international country calling code, the national destination codes or area prefixes, and the length of the subscriber number. It distinguishes geographic numbers from non-geographic numbers such as mobile, toll-free, premium-rate, and short codes, and it designates how numbers are dialed domestically and internationally.

National numbering plans are administered by regulators or dedicated numbering authorities. They allocate ranges to operators, set digit-pattern rules, and manage capacity to avoid exhaustion. They also provide for emergency services, number portability, and the introduction of new services within the national framework. The international layer is coordinated through ITU-T E.164, which defines the structure of country codes and the format of international numbers. National plans must align with E.164 while preserving routing efficiency and service accessibility.

Implementation considerations include balancing growth and conservation of number resources, ensuring portability, and integrating new technologies such as mobile and VoIP. Plans may be revised to accommodate changes in usage patterns or to introduce new prefixes for emerging services.

See also: ITU-T E.164, National numbering plan, Number portability, Emergency numbers.