E.164 defines the components of a telephone number and how many digits it can contain. The international area codes (such as 41 for Switzerland, 43 for Austria and 49 for Germany) are also specified.
Complete E.164 numbers in the international notation according to E.123 are sometimes referred to as Fully Qualified Telephone Numbers ( FQTN ) in connection with ENUM , because they uniquely designate a telephone connection worldwide. The term is formed parallel to Fully Qualified Domain Name (FQDN): " [ENUM] is the name of a protocol that resolves fully qualified telephone numbers to fully qualified domain name addresses using a DNS-based architecture. "
- FAQ of the former enum.org (accessed October 23, 2009)
- ITU-T E.164 International Numbering Plan
- ITU-T E.164 Appendix: List of assigned country codes. (PDF) December 15, 2016, accessed January 30, 2020 .