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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 call usually requires the dialing of a single or two-digit national trunk prefix preceding any area codes and the destination subscriber number. In most countries, such as Australia, China, France, Germany, Indonesia, Japan, the Netherlands, Sweden, and the United Kingdom, the trunk prefix is 0. In the North American Numbering Plan (NANP) states, such as the U.S. and Canada, it is 1.
For international telephone calls, the national trunk prefix is not dialed; instead, an international trunk prefix (or "+") is typically required, followed by the destination's country code.
Assume that a call is to be made to a customer in the Australian Area/State of Queensland with the local number of 3333 3333 and the area code 7.
A caller from outside Australia must dial the international call prefix of the originating country, plus the country calling code (61 in the case of Australia), plus the area code (7 in this case), and then the local subscriber number. Therefore, a caller in the UK must dial 00 61 7 3333 3333, while a caller in the US must dial 011 61 7 3333 3333.
Calling inter-area (within Australia) (e.g. from Western Australia—area code 8), a caller need not dial an international trunk prefix or a country code. However, the caller must at least dial the Australian trunk prefix (0) followed by the area code (7) and then the local subscriber number: 07 3333 3333. Calling from within the Queensland (7) area, a caller need only dial the telephone number: 3333 3333.
However, since the early 21st century, the majority of telephone systems worldwide are able to recognize the area of origin of the call, its direction and destination in order to facilitate communication faster. If the full international number is used, then this full international number may be dialed from nearly any telephone within a recognizable landline or mobile network. This has become particularly vital for users of mobile phones.
When conducting business, e.g., for display on business cards or stationery, the number would be +61 7 3333 3333 instead, and include only the digits that must be dialed from internationally. The plus sign is used to indicate that an international trunk prefix is first dialed and, therefore, a country code then follows. It has become common (but incorrect) practice to write the number with the national trunk prefix in parentheses,for example: +61 (0) 7 3333 3333. However, someone calling this number from the U.S. may mistake the national trunk code for a single-digit area code, as NANP area codes are often written in parentheses, dial all the digits and result in a misdirected or failed call. ITU-T Recommendation E.123 states that parentheses should not be used in the international notation to avoid such confusion.
The number next to the country in the list below denotes the country's national trunk prefix.
The North American Numbering Plan (NANP) is a telephone numbering plan for World Zone 1, which comprises twenty-five distinct regions in twenty countries primarily in North America, including the Caribbean. Some North American countries, most notably Mexico, do not participate in the NANP.
A toll-free telephone number or freephone number is a telephone number that is billed for all arriving calls instead of incurring charges to the originating telephone subscriber. For the calling party, a call to a toll-free number from a landline is free of charge.
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, reachable by a system of destination code routing. Telephone numbering plans are defined in each of administrative regions of the public switched telephone network (PSTN) and they are also present in private telephone networks. For public number systems, geographic location plays a role in the sequence of numbers assigned to each telephone subscriber.
The Australian telephone numbering plan describes the allocation of phone numbers in Australia. It has changed many times, the most recent major reorganisation by the Australian Communications and Media Authority taking place between 1994 and 1998.
Telephone numbers in the Netherlands are administered by the Ministry of Economic Affairs, Agriculture and Innovation of the Netherlands and may be grouped into three general categories: geographical numbers, non-geographical numbers, and numbers for public services.
In the United States and Canada, ten-digit dialing is the practice of including the area code of a telephone number when dialing to initiate a telephone call. When necessary, a ten-digit number may be prefixed with the trunk code 1, which is referred to as 1+10-digit dialing or national format.
Numbers on the Irish telephone numbering plan are regulated and assigned to operators by ComReg.
Area code 246 is the telephone area code in the North American Numbering Plan (NANP) for Barbados. Telecommunication services in Barbados are regulated by the Government of Barbados's telecommunications unit. The number 246 spells BIM on an alpha-numeric telephone keypad, a nickname for the island.
Widespread UK telephone code misconceptions, in particular brought on by the Big Number Change in 2000, have been reported by regulator Ofcom since publication of a report it commissioned in 2004.
The dialling plan for mobile networks and new landline operators is closed; all subscriber numbers must be dialled in full. For landline numbers starting with 02, the dialling plan used to be open; the trunk digit and area code could be omitted if the caller was in the same area code as the callee. However, starting May 3, 2008, all landline numbers must be dialled in full.
The New Zealand telephone numbering plan describes the allocation of telephone numbers in New Zealand and the Pitcairn Islands.
Telephone numbers in Italy are managed by the Autorità per le Garanzie nelle Comunicazioni (AGCOM), a national regulatory authority for the communication industry located in Rome.
Telephone numbers in Canada follow the fixed-length Bell System format, consisting of the country code +1, followed by a three-digit area code, a three-digit central office code and a four-digit station code. This is represented as 1 NPA NXX XXXX, in which the country code is "1".
A telephone number in Belgium is a sequence of nine or ten digits dialed on a telephone to make a call on the Belgian telephone network. Belgium is under a closed telephone dialing plan, meaning that the full national number must be dialed for all calls, but it retains the trunk code, '0', for all national dialling.
The national conventions for writing telephone numbers vary by country. While international standards exist in the form of the International Telecommunication Union sector ITU-T issued recommendation E.123, national telephone numbering plans define the format and length of telephone numbers assigned to telephones.
A telephone number is a sequence of digits assigned to a fixed-line 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 for data transmission via the public switched telephone network (PSTN) or other public and private networks.