Telephone numbering plan

Overview of telephone numbering plans

Overview

A telephone numbering plan is a type of numbering scheme used in telecommunications to assign telephone numbers to subscriber telephones or other telephony endpoints. Telephone numbering plans are defined by the International Telecommunication Union (ITU) and are implemented by national or regional telecommunications authorities.

Structure of Telephone Numbers

Telephone numbers are structured according to a specific format that includes several components:

• Country Code: A numerical prefix that identifies a specific country or region. For example, the country code for the United States is +1.
• Area Code: A segment of the telephone number that designates a specific geographic region within a country.
• Local Number: The unique number assigned to an individual subscriber within an area code.

Types of Numbering Plans

Open Numbering Plan

An open numbering plan allows for variable length of telephone numbers. This type of plan is often used in countries with a large number of subscribers and a diverse range of geographic regions.

Closed Numbering Plan

A closed numbering plan uses a fixed length for all telephone numbers. This type of plan is typically used in countries with a smaller population or a more centralized telecommunications infrastructure.

International Numbering Plan

The International Telecommunication Union (ITU) has established the E.164 standard for international telephone numbering. This standard defines a maximum length of 15 digits for international telephone numbers, including the country code.

Implementation

Telephone numbering plans are implemented by national or regional telecommunications authorities. These authorities are responsible for assigning area codes and local numbers, as well as managing the allocation of numbers to telecommunications providers.

Challenges and Considerations

Number Portability

Number portability allows subscribers to retain their telephone numbers when switching service providers. This requires coordination between telecommunications providers and regulatory authorities.

Number Exhaustion

As the demand for telephone numbers increases, numbering plans must be managed to prevent exhaustion of available numbers. This may involve introducing new area codes or restructuring existing numbering plans.

Related pages

• Telephone number
• Area code
• International Telecommunication Union
• E.164

A historical example of a telephone card, illustrating the use of telephone numbers in communication.