International direct dialing

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International direct dialing (IDD) or international subscriber dialing (ISD) is the process of an international telephone call being placed by the caller (the subscriber) rather than by an operator. The term international subscriber dialing was used in the United Kingdom and Australia until the terminology was changed to international direct dialing.[when?] Since the late 20th century, most international calls are dialed directly.

Calls are made by dialing the international call prefix for the country one is in, followed by the country calling code for the country one wishes to call, followed by the phone number within that country. When phone numbers are published for use abroad they typically include the country calling code, but replace the international call prefix with "+" to signify that the caller should use the prefix appropriate for their country. For mobile phones, the plus sign (+) can be used instead of the prefix.[1]


A (fictitious) number dialed locally in Sydney, Australia as 3456 7890 would be dialed outside of its local area, but still in its country (Australia), as 02 3456 7890.

In the United States, this number would be dialed as 011 61 2 3456 7890, with 011 being the international call prefix used in the USA and 61 being the country calling code of Australia.

On business cards for local use, this number would be given as 3456 7890, for national (Australia-wide) use as 02 3456 7890 or perhaps (02) 3456 7890, and for international use +61 2 3456 7890. The + represents the international call prefix, which varies from country to country, is specific to the country from which the call is being made, and is 011 in the USA. The leading 0 in the national number 02 3456 7890 is dropped for international calls.

See also[edit]


  1. ^ How to call abroad Retrieved 2011-10-20.