International direct dialing (IDD) or international subscriber dialling (ISD) is placing an international telephone call, dialed directly by a telephone subscriber, rather than by a telephone operator. Subscriber dialing of international calls typically requires an

international call prefix International direct dialing (IDD) or international subscriber dialling (ISD) is placing an International call, international telephone call, dialed directly by a telephone subscriber, rather than by a switchboard operator, telephone operator. Sub ...

(international dial-out code, international direct dial code, IDD code) to be dialed before the country code. The term ''international subscriber dialling'' was used in the United Kingdom and Australia until the terminology was changed to ''international direct dialling''. Since the late 20th century, most international calls are dialed directly. Calls are initiated by dialing the international call prefix for the originating country, followed by the

country calling code Telephone country codes are telephone number prefixes for reaching subscribers in foreign countries or areas by international direct dialing (IDD). Country codes are defined by the International Telecommunication Union (ITU) in ITU-T standards ...

for the destination country, and finally the national

telephone number A telephone number is the address of a Telecommunications, telecommunication endpoint, such as a telephone, in a telephone network, such as the public switched telephone network (PSTN). A telephone number typically consists of a Number, sequ ...

of the destination. For example, a landline subscriber in the UK wishing to call Australia would first dial the following sequence: ''00'' (the call prefix used in the UK to access the international service), followed by ''61'' (the country calling code for Australia), followed by the national subscriber number (without the

trunk prefix A trunk prefix is a digit sequence to be dialled 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) teleph ...

''0'' used for dialing within Australia).

International call prefix

An "international call prefix", "international dial-out code" or "international direct dial code" (IDD code) is a

that indicates an international phone call. In the dialling sequence, the prefix precedes the

(and, further, the carrier code, if any, and the destination

). The international call prefix is defined in 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, reach ...

of every country or telephone administration. The

International Telecommunication Union The International Telecommunication Union (ITU)In the other common languages of the ITU: * * is a list of specialized agencies of the United Nations, specialized agency of the United Nations responsible for many matters related to information ...

(ITU) recommendation E.164 specifies the sequence ''00'' as a standard for the international call prefix and this has been implemented by the majority of countries. Member countries of the

North American Numbering Plan The North American Numbering Plan (NANP) is an integrated 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, World Numbering Zone ...

(NANP) use ''011''. Certain

post-Soviet states The post-Soviet states, also referred to as the former Soviet Union or the former Soviet republics, are the independent sovereign states that emerged/re-emerged from the dissolution of the Soviet Union in 1991. Prior to their independence, they ...

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 prefix ''00'' is followed immediately by the so-called carrier selection code, i.e., a numeric code that routes the call via a specific provider for international connectivity. Some 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.

Example

The fictitious telephone number ''(02) 3456 7890'', as published locally in Sydney, Australia, is published in the form ''+61 2 3456 7890'' for international use. In countries participating in the North American Numbering Plan, such as the United States or Canada, this number is dialed as ''011 61 2 3456 7890'', with ''011'' being the international call prefix in the NANP and ''61'' being the country code of Australia. From most of the rest of the world, the international access code is ''00'', so that the call is dialed as ''00 61 2 3456 7890'', as recommended by the ITU standards.

References

{{Telecommunications International telecommunications Teletraffic

International call prefix

Example

See also

References