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.

In most countries, making a domestic telephone call requires the dialing of a single digit preceding any area codes and the destination subscriber number. In most countries, such as Australia, Germany and the United Kingdom, the trunk prefix is 0. In the North American Numbering Plan it is 1. When the same telephone number is called from another country, the national trunk prefix is not dialed; instead, for international calls, an international trunk access code is typically required. Many countries use the sequence 00, but in the member states of the NANP, such as the US and Canada, it is 011.