An international call prefix, international dial-out code or international direct dial code (IDD code) is a
trunk prefix
A trunk prefix is a digit sequence to be dialed before a telephone number to initiate a telephone call for the purpose of selecting an appropriate telecommunications circuit by which the call is to be routed.
Making a domestic (national) telephone ...
that indicates an
international phone call. In the dialling sequence, the prefix precedes the
country calling code (and, further, the carrier code, if any, and the destination
telephone number
A telephone number is a sequence of digits assigned to a landline telephone subscriber station connected to a telephone line or to a wireless electronic telephony device, such as a radio telephone or a mobile telephone, or to other devices f ...
).
The international call prefix is part of the
telephone numbering plan
A telephone numbering plan is a type of numbering scheme used in telecommunication to assign telephone numbers to subscriber telephones or other telephony endpoints. Telephone numbers are the addresses of participants in a telephone network, re ...
of every country.
Standardisation
The
International Telecommunication Union
The International Telecommunication Union is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established on 17 May 1865 as the International Telegraph Unio ...
(ITU) recommends the sequence 00 as a standard for an international call prefix, and this has been implemented by the majority of countries.
A significant number of countries, however, use 011 as the international call prefix – mainly countries that follow the
North American Numbering Plan
The North American Numbering Plan (NANP) is a telephone numbering plan for twenty-five regions in twenty countries, primarily in North America and the Caribbean. This group is historically known as World Zone 1 and has the international calling ...
. Certain
post-Soviet states
The post-Soviet states, also known as the former Soviet Union (FSU), the former Soviet Republics and in Russia as the near abroad (russian: links=no, ближнее зарубежье, blizhneye zarubezhye), are the 15 sovereign states that wer ...
continue to use 810 which was the universal IDD code across the Soviet Union. Other prefixes (000, 001, 0011, 119, etc.) are also in use in a small number of countries.
Some countries require that the 00 prefix is followed immediately by the so-called carrier selection code, i.e., a numeric code that routes the call via a specific provider of international connectivity. Other countries may require that any carrier selection codes precede the international call prefix.
Some countries also offer simplified dialling arrangements for calls to neighbouring countries, usually by removing the need of dialling an international call prefix and the country code.
To avoid confusion especially in international context, a plus sign (+) is often used as a graphic symbol of the international access code; it informs the caller to replace it with the prefix code appropriate for their country.
Additionally, the
GSM
The Global System for Mobile Communications (GSM) is a standard developed by the European Telecommunications Standards Institute (ETSI) to describe the protocols for second-generation ( 2G) digital cellular networks used by mobile devices such ...
mobile telephony standard allows the use of the plus sign in place of the international call prefix; the mobile operator then automatically converts the plus sign to the correct international prefix, depending on the location where the phone is being used. This enables callers to use the same stored number when calling from any country.
Examples
Calling +64 3 477 4000, which is the number of
Dunedin City Council
The Dunedin City Council ( mi, Kaunihera ā-Rohe o Ōtepoti) is the local government authority for Dunedin in New Zealand. It is a territorial authority elected to represent the people of Dunedin. Since October 2022, the Mayor of Dunedin is Jul ...
in New Zealand (country code: 64), from outside New Zealand:
See also
*
International direct dialing
*
List of international call prefixes
The following is a list of different international call prefixes that need to be dialled when placing an international telephone call from different countries.
Countries by international prefix
Countries using optional carrier selection code ...
References
{{reflist
Telecommunications
Telephony