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Area code

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The area code is a part of a telephone number normally occurring at the beginning of the number, that usually indicates a geographical area. It directs telephone calls to particular regions on a public switched telephone network (PSTN), where they are further routed by the local network.

Callers within the geographical area of a given area code usually do not need to include this particular area code in the number dialed, thereby giving the caller shorter local telephone numbers. In international phone numbers, the area code directly follows the country calling code.

While the E.164 standard regulates country codes at the international level, it is each country's responsibility to define the numbering within its own network. As a result, area codes may have:

  • A fixed length, e.g. 3 digits in the US; 2 digits in Australia.
  • A variable length, e.g. between 2 and 5 in Germany and in South Africa; between 1 and 3 in Japan.
  • Or be omitted altogether, as is the case in many countries, such as France or Norway, where the whole country is in effect a single "area".

In many cases the area codes determine the rate (price) of a call. For example, in the US calls to the 800, 888, 877, and 866 areas are free to the caller and paid by the receiver, while calls to the 900 area are "premium rate", which means "very expensive". Normally intra-area calls are charged lower than inter-area calls, but there are exceptions, e.g. in Israel both are charged at the same rate.

United States and Canada

In the United States and Canada, area codes are regulated by the North American Numbering Plan. Currently, all area codes in the NANP must have 3 digits. Many other countries have area codes that are shorter for heavily populated areas and longer for lightly populated areas. Area codes are also referred to as NPAs, for Numbering Plan Area.

Before 1995, North American area codes were of the form [2-9][0/1][0-9], with the prefix or NNX in the form [2-9][2-9][0-9]; that codespace filled up due to overallocation, and was extended to [2-9][0-8][0-9]-[2-9][0-9][0-9] (referred to as NPA-NXX).

Not all area codes correspond to geographical area. Codes 8xx with the last two digits matching, such as 800, 888, 877, 866, etc., are reserved for toll-free calls. Code 900 is reserved for premium-rate calls (also known as dial-it services).

There are a number of proposals for what the NANP should do when this larger space fills up. In one proposal, existing codes may be changed to "a9bc" (e.g. San Francisco 415 would become 4915); once that conversion is complete, the new second digit would be opened for a new range. Other proposals include reallocating blocks of numbers assigned to smaller long distance carriers or unused reserved services.

None(?) of these changes enable the existence of variable length area codes, which are commonplace outside the USA (See United Kingdom below). Also see [1]

There are two noteworthy peculiarities in the US numbering:

  • In some cases you need to dial the area code even when calling within the same area; this is usually the case in urban areas where a 'local' call may be in another time zone, or where two different zone codes are overlaid on the same area. This practice is known as ten-digit-dialing.
  • Mobile phones are allocated numbers within regular area codes, instead of special area codes. This, together with the lack of a single cellular standard in the US, is often cited as a reason for the relatively low penetration of cellular telephony in the US.

See also: List of North American area codes.

Another oddity of US telephone numbering is the popularity of alphabetic dialing. On most US telephones, three letters appear on each number button from 2 through 9. This accommodates 24 letters. Historically, the letters Q and Z were eliminated, though on most modern telephones, they are added, so that the alphabet is apportioned as follows:

2 = abc 3 = def 4 = ghi 5 = jkl 6 = mno 7 = pqrs 8 = tuv 9 = wxyz

No letters are allocated to the 1 or 0 keys.

Originally, this scheme was meant as a mnemonic device for telephone number prefixes. When telephone numbers in the US were standardized in the mid-20th century, they were six digits long, including a 2-digit prefix. The prefix was a word, and the first two letters of the word were dialed. Later, a 3rd, numeric character was added to prefixes. Thus, the famous Duke Ellington tune "Pennsylvania 6-5000" refers to a telephone number that would have been dialed 736-5000. Similarly, the classic Elizabeth Taylor film "Butterfield 8" refers to the section of New York City where the film is set, where telelphone prefixes were 288. The second letter was often also capitalized to emphasize what to dial. This author's childhood telephone number was MOhawk 5-6612.

Today this system has been abandoned, but alphabetic dialing remains as a commercial mnemonic gimmick, particularly when combined with toll-free numbers. For example, one can dial 1-800-FLOWERS to send flowers to someone. Sometimes, longer words are used - for example one might be invited to give money to a public radio station by dialing 1-866-KPBS-GIVE. The "number" is 8 digits long, but only the first seven need be dialed. If the eighth digit is dialed, the switching system will ignore it.

United Kingdom

In the United Kingdom, area codes are -- including the leading '0' which is dropped when calling UK numbers from overseas -- three or four or five digits long, with larger towns and cities having shorter area codes permitting a larger number of telephone numbers in the ten digits used. Area codes are sometimes still called STD (Subscriber Trunk Dialling) codes.

A short list of examples, set out in the officially approved (Ofcom) number groups:

History

Area codes were first introduced in 1958, allowing a caller to call another telephone direct instead of via a manual telephone exchange, a process known as Subscriber Trunk Dialling (STD), although the process was not completed until 1979. The four-digit codes were originally assigned based on the first three letters of the respective place's name and the corresponding numbers on a telephone keypad. For example Aylesbury was given the STD code (0)296, where the letter (a) can be found on the number 2, the letter (y) on the number 9 and the letter (l) on the number 6. However as more and more places were given STD codes this system became unworkable.

The Director system was put in place in six cities, including London, where only a 2 or 3 digit code was used for the city, followed by a 3 digit code, represented by letters, to identify the local exchange.

In May 1990, growth of phone numbers in London caused the London area, so far (0)1, to be split into inner and outer (0)71 and (0)81.

Five years later in 1995, the whole country was running out of numbers, so nearly all local codes were given an extra initial 1. Thus, central London's (0)71 became (0)171.

Amid criticism for not having made adequate provision in 1995, on April 22, 2000, numbers in London, Portsmouth, Southampton, Cardiff, Coventry and Northern Ireland changed again to give an eight digit local number and a three digit area code - (0)20 in the case of London, for example. This was part of a larger restructuring of all UK codes.

Changes to numbering below the initial two digits will continue to occur from time-to-time.

Current Structure

Since April 28, 2001, the overall code structure in the UK is:

(0)1 Geographic area codes
(0)2 Geographic area codes (newly introduced in 2001)
(0)3 Reserved for area codes
(0)4 Reserved
(0)5 Reserved for corporate numbering
(0)6 Reserved
(0)7 "Find Me Anywhere" services (mobile phone, pager & personal numbers)
(0)8 Freephone (toll free), Local & National Rate numbers
(0)9 Premium Rate services and multimedia

Databases of current area codes are held at:

For other UK topics see UK topics.

Netherlands

In the Netherlands, the area codes are -- excluding the leading '0' -- one, two or three digits long, with larger towns and cities having shorter area codes permitting a larger number of telephone numbers in the ten digits used.

  • (0)10 : Rotterdam
  • (0)20 : Amsterdam
  • (0)30 : Utrecht
  • (0)40 : Eindhoven
  • (0)50 : Groningen
  • (0)6 : mobile phone number
  • (0)676 : internet access phone number
  • (0)70 : The Hague
  • (0)800 : toll free number
  • (0)900 : premium rate call
  • (0)906 : premium rate
  • 112 : emergency phone number

See Also