Telephone numbering plan

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"Area Code" redirects here. For the song by Ludacris, see Area Codes (song).

A telephone numbering plan is a plan for allocating telephone number ranges to countries, regions, areas and exchanges and to non-fixed telephone networks such as mobile phone networks. Dialing plans should not be confused with numbering plans. A closed numbering plan, such as found in North America, features fixed length area codes and local numbers. An open numbering plan, as found in assorted countries that have not yet standardized, features variance in length of area code or local number, or both. The rules for dialing the numbers assigned by the numbering plan vary by defining which digits need not always be dialed (codes) and digits that must always be dialed (local number).

1 Structure
2 Standards
3 Open dialing plans
4 Closed dialing plans
5 Satellite phone numbering plans
6 Special services
7 Numbering plans by global regions
8 See also
9 References

[edit] Structure

Initially connections were made in the central office by telephone operators using "patch cords" to connect one party to another. If a person wanted to make a phone call, he or she would pick up a phone & wind a crank on the side. The crank was a small generator that would light a lamp at the central office. An operator would see the light and insert her patch cord into a socket & assist the customer with the call connection. The Operator would use patch cords to connect the caller to the person being called. If the party being called was in another exchange, the Operator would use a patch cord to connect to another exchange where an Operator elsewhere would finish the connection. As technology advanced computers were introduced and Operators used "rotary dials" to complete all calls.

Area codes were assigned based on the length of time a rotary dial phone took to dial the area code. Densely populated areas like New York City, Chicago and Los Angeles had huge call volume and were assigned numbers (212, 312, 213) that could be quickly dialed from a rotary dial phone. On a rotary dial phone low digits (1, 2, 3, 4) could dial quickly as the time the rotary dial took to return to the home position was minimal. High digit numbers (7, 8, 9, 0) on rotary dial phones took much longer to return to the home position and were usually used in less densely populated areas like Vermont (802), rural Texas (915), Tennessee (901), and the Canadian Maritimes (902). This system became unnecessary when touch-tone phones arrived, as the tone allowed instant entry of digits.

The structure is:

Access code (either international or national) - necessary only when dialing international and "national" (non-local domestic) calls. The national access code is often quoted as if it were part of the telephone number. The most common national access code is "0", and the most common international access code "00"; in the North American Numbering Plan (i.e. the United States and Canada), however, "1" is used internally within North America, and "011" is used if you need to dial a number outside that area (e.g. Europe, Africa, or Asia, etc).
Country code - necessary only when dialing to phones in other countries. In international usage, telephone numbers should always be quoted with the country code preceded by a "+", and with spaces in place of hyphens (e.g. "+XX YYY ZZZ ZZZZ"). This allows the reader to choose which Access Code they need to dial from their location. However, it is often quoted together with the international access code which must precede it in the dial string, especially in the United States and Canada (e.g. "011-XX-YYY-ZZZ-ZZZZ"). This can cause confusion as "011" may not be a valid Access Code where the reader is located. (On GSM networks, "+" is an actual character that may be used internally as the international access code, rather than simply being a convention.)
Area code - necessary (for the most part) only when dialed from outside the code area, from mobile phones, and (especially within North America) from within overlay plans. Area codes usually indicate geographical areas within one country that are covered by perhaps hundreds of telephone exchanges. It must usually be preceded in the dial string by either the national access code or the international access code and country code. For non-geographical numbers, as well as mobile telephones outside of the United States and Canada, the "area code" does not correlate to a particular geographic area.
Local number - must always be dialed in its entirety. The first few digits in the local number typically indicate smaller geographical areas or individual telephone exchanges. In mobile networks they may indicate a network provider in case the area code doesn't. Callers from a number with a given area/country code usually do not need to (but optionally may) include the particular area/country code in the number dialed, which enables shorter 'dial strings' to be used. Devices that dial phone numbers automatically can include the full number with area and access codes, since there is no additional annoyance related to dialing extra digits.

[edit] Standards

Although the International Telecommunication Union (ITU) has attempted to promote common standards among nation states, numbering plans take different formats in different parts of the world. For example, the ITU recommends that member states adopt 00 as their international access code. However, as these recommendations are not binding on member states, some have not, such as the United States, Canada, and other countries and territories participating in the North American Numbering Plan.

The international numbering plan establishes country codes, that is, area codes that denote nations or groups of nations. The E.164 standard regulates country codes at the international level and sets a maximum length limit on a full international phone number. However, it is each country's responsibility to define the numbering within its own network. As a result, regional area codes may have:

A fixed length, e.g. 3 digits in the United States and Canada; 1 digit in Australia and New Zealand.
A variable length, e.g. between 2 and 5 in Germany, Argentina and in Austria; between 1 and 5 in Japan; 1 or 2 in Syria and Peru.
Or be incorporated into the subscriber's number, as is the case in many countries, such as Spain or Norway. This is known as a "closed" telephone numbering plan. In some cases a trunk code (usually 0) must still be dialed, as in Belgium, Italy, the Netherlands, Poland, Switzerland, South Africa, and some locations within the NANP.

Generally the area codes determine the cost of a call. Calls within an area code and often a small group of adjacent or overlapping area codes are normally charged at a lower rate than outside the area code. (This is often not the case in the United States where rates to call within a state [regulated by that state's public utilities commission] are often higher than rates to call across the country [generally determined by competition]. This has changed dramatically with the deregulation of local phone services.)^{[dubious – discuss]} Special area codes are generally used for free, premium rate, mobile phone systems (in countries where the mobile phone system is caller pays) and other special rate numbers. There are however some exceptions, in some countries (e.g. Egypt), calls are charged at the same rate regardless of area and in others (e.g. the UK) an area code is occasionally treated as two parts with different rates.

[edit] Open dialing plans

An open dialing plan is one in which there are different dialing arrangements for local and long distance telephone calls. This means that to call another number within the same city or area, callers need dial only the number, but for calls outside the area, an area code is required. The area code is prefixed by a trunk code (usually "0"), which is omitted when calling from outside the country. To call a number in Sydney, Australia for example:

xxxx xxxx (within Sydney, New South Wales - no area code required)
xxxx xxxx (all other locations within New South Wales - no area code required)

Note that calls originating within NSW but outside Sydney may be dialled as an 8-digit number without the area code, but this does not make them a "local call" or unit fee. Such calls will be charged at the caller's prevailing long-distance rates.

(02) xxxx xxxx (outside New South Wales - the area code is required)
+61 2 xxxx xxxx (outside Australia. Notice the dropped 0)

In the United States, Canada, and other countries or territories using the North American Numbering Plan (NANP), the trunk code is '1', which is also (by coincidence) the country calling code. To call a number in San Francisco, the dialing procedure will vary:

xxx xxxx (local calls, no area code required)
1 415 xxx xxxx (outside San Francisco)
415 xxx xxxx (optional for mobile phones within the USA)
+1 415 xxx xxxx (outside the NANP)

However, in parts of North America, especially where a new area code overlays an older area code, dialing the area code, or 1 + the area code, is now required even for local calls, which means that the NANP is now closed in certain areas and open in others. Dialing from mobile phones is different in the USA, as the trunk code is not necessary, although it is still necessary for calling all long distance numbers from a mobile phone in Canada. (Most mobile phones today can be programmed to automatically add a frequently-called area code as a prefix, allowing calls within the desired area to be dialed by the user as seven-digit numbers, though sent by the phone as 10-digit numbers.)

New Zealand has a special case of an open dialling plan. While most nations require the area code to be dialled only if it is different, in New Zealand, one needs to dial the area code if the phone is outside your local calling area. For example, to call a phone number in Auckland City:

xxx xxxx (within Auckland, Waitakere, North Shore, and Manukau)
09 xxx xxxx (within the 09 area code, but not within Auckland, Waitakere, North Shore, and Manukau)
09 xxx xxxx (within New Zealand, outside the 09 area code)
+64 9 xxx xxxx (outside New Zealand)

The same rule also applies in many parts of the NANP, including all areas of Canada that still have an open dialing plan. This is not universal, as there are locations within the United States that allow long distance calls within the same area code to be dialed as seven digits. In Canada, the trunk code (also known as the long distance access code) must also be dialed along with the area code for long distance calls even within the same area code. For example, to call a number in Regina:

xxx xxxx (within Regina, Lumsden and other local areas)
1 306 xxx xxxx (within the 306 area code, but not within the Regina local calling area (e.g. Saskatoon)
1 306 xxx xxxx (anywhere within the NANP outside the 306 area code)
+1 306 xxx xxxx (outside NANP)

Open and closed dialing plan should not be confused with open and closed numbering plans. A closed numbering plan, such as found in North America, features fixed length area codes and local numbers. An open numbering plan, as found in assorted countries that have not yet standardized, features variance in length of area code or local number, or both. Closed dialing plans are rare where numbering plans are open.

[edit] Closed dialing plans

A closed numbering plan is one in which the subscriber's number is a standard length, and a closed dialing plan is one in which the subscriber's number is used for all calls, even in the same area. This has traditionally been the case in small countries and territories where area codes have not been required. However, there has been a trend in many countries towards making all numbers a standard length, and incorporating the area code into the subscriber's number. This usually makes the use of a trunk code obsolete. For example, to call Oslo in Norway before 1992, one would dial:

xxx xxx              (within Oslo - no area code required)
(02) xxx xxx         (within Norway - outside Oslo)
+47 2 xxx xxx        (outside Norway)

After 1992, this changed to a closed eight-digit numbering plan, eg:

22xx xxxx     (within Norway - including Oslo)   
+47 22xx xxxx (outside Norway)

In other countries, such as France, Belgium, Poland, Switzerland, South Africa, and some parts of North America where the dialing plan is closed, the trunk code is retained for domestic calls, whether local or national, eg:

Paris 01 xx xx xx xx (outside France +33 1 xxxx xxxx)
Brussels 02 xxx xxxx (outside Belgium +32 2 xxx xxxx)
Warsaw 022 xxx xxxx  (outside Poland +48 22 xxx xxxx
Geneva 022 xxx xxxx  (outside Switzerland +41 22 xxx xxxx) 
Cape Town 021 xxx xxxx (outside South Africa +27 21 xxx xxxx)
New York 1 212 xxx xxxx (outside the NANP +1 212 xxx xxxx)

Further, there are locations with closed dialing plans in the NANP that require the full phone number including area code to be dialed for all calls, but the trunk code is required for only long distance calls, even in the same area code.

While the use of full national dialing is less user-friendly than using only a local number without the area code, the increased use of mobile phones, which require full national dialing and can store numbers, means that this is of decreasing importance. It also makes easier to display numbers in the international format, as no trunk code is required--hence a number in Prague, Czech Republic, can now be displayed as:

2xx xxx xxx (inside Czech Republic)
+420 2xx xxx xxx (outside Czech Republic)
formerly (until September 21, 2002):^[1]    
                                                 
02/xx xx xx xx  (inside Czech Republic) 
+420 (0)2/xx xx xx xx (outside Czech Republic)

[edit] Satellite phone numbering plans

Satellite phones are usually issued with numbers in a special country calling code. For example, Inmarsat satellite phones are issued with codes +870 through +874, while Global Mobile Satellite System providers, such as Iridium, issue numbers in country code +881 ("Global Mobile Satellite System") or +882 ("International Networks"). Some satellite phones are issued with ordinary phone numbers, such as Globalstar satellite phones issued with NANP telephone numbers.

Inmarsat:
- +870: SNAC (Single Network Access Code)
- +871: Atlantic Ocean Region – East (AOR-E),
- +872: Pacific Ocean Region (POR)
- +873: Indian Ocean Region (IOR)
- +874: Atlantic Ocean Region – West (AOR-W)
ICO Global: +881 0, +881 1.
Ellipso: +881 2, +881 3.
Iridium: +881 6, +881 7.
Globalstar: +881 8, +881 9.
Emsat: +882 13.
Thuraya: +882 16.
ACeS: +882 20.

[edit] Special services

Some country calling codes are issued for special services, or for international/inter regional zones.

+388 – shared code for groups of nations

+388 3 – European Telephony Numbering Space – Europe-wide services

+800 – International Freephone (UIFN)
+808 – reserved for Shared Cost Services
+878 – Universal Personal Telecommunications services
+881 – Global Mobile Satellite System
+882 – International Networks
+979 – International Premium Rate Service
+991 – International Telecommunications Public Correspondence Service trial (ITPCS)
+999 – reserved for potential disaster relief service