E.164 Format: Understanding and correct use of international telephone numbers

Posted on: 2023-03-03 | Categories: SIP

The E.164 format serves as a universal standard for international telephone numbers, providing crucial insights into their format, structure, and hierarchical organization. As part of “The International Public Telecommunication Numbering Plan,” an international standard, it establishes a numbering plan for the global public switched telephone network.

Understanding the E.164 format

E.164 represents a recommended format for international telephone numbers endorsed by the International Telecommunication Union. It ensures that each device within the Public Switched Telephone Network (PSTN) possesses a unique and identifiable number worldwide.

This adoption of globally unique telephone numbers facilitates accurate routing of calls and SMS to individual phones across the globe.

How to structure an E.164 format?

To properly utilize the E.164 format, it follows a specific structure:

  • Presence of the “+” sign.
  • Country calling code (international).
  • Local area code.
  • Local telephone number or subscriber number.

The structure can be summarized as follows: [+][country code][area code][subscriber number].

Example: E.164 Format Number in the United States

Telephone number: 415 123 4567
E.164 format number: +14151234567

  • Country code: +1
  • Area code: 415
  • Subscriber number: 1234567

Example: E.164 format number in the United Kingdom

Telephone number: 01234 123456
E.164 format number: +441234123456

  • Country code: +44
  • Area code: 1234
  • Subscriber number: 123456

Example: E.164 format number in Spain

Telephone number: 652 123 456

E.164 format number: +34652123456

  • Country code: +34
  • Area code: 652
  • Subscriber number: 123456

How to dial an E.164 phone number correctly

To ensure precise dialing and successful delivery of calls and SMS, it is crucial to keep the following considerations in mind:

  1. Avoid adding spaces between the elements (+ sign, country code, area code, and subscriber number) while entering the complete number.
  2. E.164 format numbers are limited to a maximum of 15 digits.
  3. Certain telephone numbers, such as Scottish numbers, begin with 0, which should be omitted as it is specific to national calls. Dialing from a foreign country with the 0 prefix will result in an error.

By adhering to the E.164 format, you can maximize the likelihood of your calls and SMS reaching the intended recipients.

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