E.123

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ITU-T Recommendation E.123, or the Notation for national and international telephone numbers Recommendation E.123 defines a standard way to write telephone numbers, e-mail addresses, and web addresses. It recommends the following formats (when dialling the area code is optional for local calling):

   Telephone number, national notation:      (042) 123 4567
   Telephone number, international notation: +31 42 123 4567
   E-mail address:                           name@example.com
   Internet address / URL:                   www.example.com

E.123 recommends that only spaces be used to visually separate groups of numbers, "...unless an agreed upon explicit symbol (e.g. hyphen) is necessary for procedural purposes..." in national notation. Only spaces should be used to visually separate groups of numbers in international notation. In national notation, parentheses are used to indicate digits that are sometimes not dialled. Parentheses should not be used in the international notation. A slash (/) may be used to indicate alternate numbers.

[edit] In case of emergency

A standardized language-independent way to identify a next-of-kin (or other emergency contact) in a mobile handset’s directory, in case of an emergency, has in May 2008 been adopted as a new clause in Recommendation E.123.

It proposes to store emergency contact numbers in the form “0nx”, where “n” is a digit from 1 through 9 and “x” is any meaningful descriptive character string in any language or script (e.g. “Anna” or “Spouse”).

In the handset's directory this would be displayed as "01Anna" or "01Spouse" enabling easy identification by the emergency services. The handset’s directory entry (in the “contact number” field) would contain the actual number of the person to call in case of emergency.^[1]

This scheme is a language-independent version of the ICE scheme that became popular in certain parts of the world from 2005 onwards.^[2]