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Telephone number

A telephone number is a sequence of decimal digits (0-9) that is used for identifying a destination telephone or in a telephone network[?]. In fact, not only telephones but also faxes, modems, subscribers and network services can have telephone numbers. Each such endpoint must have a unique number within the network, and the number of endpoints determine the necessary length of the telephone number. It is also possible for each subscriber to have a set of shorter numbers for the endpoints most often used. These "shorthand" numbers are automatically translated to unique telephone numbers before the call can be connected.

Most telephone networks nowadays are interconnected in the international telephone network, where the format of telephone numbers is standardized by ITU-T in the recommendation E.164, which specifies that the entire number should be 20 digits or shorter, and begin with a country prefix. In most countries, this is followed by an area code or city code and the subscriber number, which might consist of the code for a particular telephone switch. ITU-T recommendation E.123 describes how to represent an international telephone number in writing or print, starting with a plus sign ("+") and the country code.

Before a telephone call is connected, the telephone number must be dialed by the calling party or caller. The receiving party or callee[?] might have equipment that presents caller ID before the call is answered.

Table of contents

History After Alexander Graham Bell invented the telephone in 1876, it was soon used as a subscription service[?] with the invention of the telephone switch or central office. Such an office was manned by an operator that connected the calls by personal names.

The latter part of 1879 and the early part of 1880 saw the first use of telephone numbers at Lowell, Massachusetts. During an epidemic of measles, Dr. Moses Greeley Parker[?] feared that Lowell's four telephone operators might succumb and bring about a paralysis of telephone service. He recommended the use of numbers for calling Lowell's more than 200 subscribers so that substitute operators might be more easily trained in the event of such an emergency. Parker was convinced of the telephone's potential, began buying stock, and by 1883 he was one of the largest individual stockholders in both the American Telephone Company[?] and the New England Telephone and Telegraph Company[?].

North America

The United States, Canada, and several countries in the Caribbean constitute the North American Numbering Plan, and share a common telephone numbering format. The discussion below focuses on the United States, but is equally valid in other countries in the region.

Aside from access codes, such as outside line, long distance, or international calling, a telephone number in the United States consists of three parts. An example might be 303-555-1212.

The area code or NPA[?] (Numbering Plan Area) is a three digit number (the 303 above) which allows the system to route calls into a small geographic area. NPAs are defined by the North American Numbering Plan, originally administered by Bellcore but now by the North American Numbering Plan Administrator (http://www.nanpa.com) (www.nanpa.com).

Within each area code are individual exchange numbers[?], represented by the second three digits, 555 in the above example. This usually represents a specific central office switching machine (or telephone switch). This local machine may actually operate with several exchange numbers, such as 555, 554, 553 and 552 (the numbers need not, however, be consecutive). Exchange numbers are also known as NXXs - not an abbreviation but a code where N=2..9 and X=0..9.

The final four digits are the subscriber number[?] or line number, 1212 in the example above. This number connects to a specific telephone circuit within the exchange.

It is traditional in American television and film to have all fictitious phone numbers begin with 555, as in 555-3245 (also known as KLondike-5 in older movies). This exchange number is typically unused by phone companies, avoiding innocent people being bombarded with unwanted phone calls. An exception is the number 555-1212 which is directory service in the US for each area code, it is basically the 411 service outside the local area code. Some regional services such as PacBell in California are now (as of 2001) converted to provide nationwide directory service via the 411 numbers which makes the (???) 555-1212 number unnecessary within California.

Some common special numbers in the United States system:

   0 - operator assist
  00 - Long Distance Operator Assist
 311 - non-emergency police matters (in some cities)
 411 - local directory service
 611 - telephone line repair service
 911 - emergency dispatcher for fire, ambulance, police etc.

 (area code) 555-1212 - non-local directory service.

Not all countries use the same numbering system. The emergency telephone number is often different from country to country.

see also country calling codes, ANAC


Presently, telephone numbers in Australia consist of a single digit area code and eight-digit local numbers, the first four of which generally specify the exchange, and the final four a line at that exchange. (Most exchanges though have several four-digit exchange codes.)

Australia is divided geographically into a few large area codes, frequently covering more than one state. The long distance prefix is '0', while the main international prefix is '0011' (there are others for special purposes, such as charging in half-hour blocks).

Prior to the introduction of eight-digit numbers in the early to mid-1990s, telephone numbers were seven digits in the major capital cities, with a single digit area code, and five digits in other areas with a two digit area code.

Australia also the free call area code 1800. This is copied from the U.S. prefix 1-800, but while in the U.S. the '1' is the long-distance prefix and '800' is the area code, '1800' in Australia is itself an area code (prior to the introduction of 8-digit numbers, the area code was '008'). Similarly, '190x' is the area code for charging services (i.e. recorded information, competition lines, psychics, phone sex, etc.). There are also '13' numbers, which work across large areas (up to across Australia) and only charge a local call, routing the call to the appropriate place in a given area. (For example, a company could have the number 139999 and have the telephone company set it up so that calls made in Melbourne would route to their Melbourne number, calls made in Brisbane to their Brisbane number, and calls made anywhere else in Australia route to their Sydney number, all at a local charge cost to the caller.)

Mobile phone numbers have three digit area codes, e.g. 412. The area codes are allocated per network, although with the introduction of number portability there is no longer a fixed relationship between the area code a mobile is in and the network it is attached to.

000 is the emergency telephone number in Australia, but the internationally accepted GSM mobile emergency telephone number 112 also works on mobile phones.

Phone numbers within Australia are allocated by the Australian Communications Authority.

United Kingdom The telephone service in the United Kingdom was originally provided by local city councils, until in 1912 all except the telephone service of Kingston-upon-Hull, Yorkshire, were bought out by the Post Office. Post Office Telephones was reorganised in the early 1970s as British Telecommunications (British Telecom, or BT), and was one of the first nationalised industries to be privatised by the Conservative government in the mid-1980s. The Hull Telephone Department was itself sold by Hull City Council as Kingston Communications in the late 1990s. Telephone services in the UK are regulated by Oftel, the Office of the Telecommunications Regulator.

The use of alphabetic exchange (area) codes was abandoned in the 1960s.

All calls within the same area code and geographically adjacent codes are local calls, more distant calls are charged at the national rate. All of London forms one large area code.

Currently, within the United Kingdom, the great majority of telephone numbers are 11 digits long. Following a series of number reorganisations in the late 1980s and 1990s the number space is organised as follows:

  • 01xxx xxxxxx - the commonest geographical number format, a five digit area code and six digit subscriber number.
  • 01x1 xxx xxxx - the geographical number format for the larger cities, a four digit area code, with a seven digit subscriber number where the first three digits identifies an area within the city.
    • - 0121 -- Birmingham
    • - 0131 -- Edinburgh
    • - 0141 -- Glasgow
    • - 0151 -- Liverpool
    • - 0161 -- Manchester
    • - 0191 -- Newcastle upon Tyne
    • 0171 and 0181 were formerly used for inner and outer London.
  • 011x xxxxxxx - the geographical number format for a second tier of large cities, a four digit area code, with a seven digit subscriber number, e.g. 0115 -- Sheffield.
  • 02x xxxx xxxx - a new geographical number format with an 8-digit subscriber number, introduced for areas which had run out of spare numbers using six or seven digit numbers, e.g.
    • - 020 -- London
    • - 026 -- Northern Ireland
    • - 029 -- Cardiff
  • 07xxx xxxxxx - mobile phones. Individual mobile phone companies are allocated different ranges within the 07xxx area codes.
  • 08xx or 08xxx -- various free, fixed-rate, or special rate services, e.g.
    • - 0800 -- free calls
    • - 0845 xxxxxxx or 08457 xxxxxx -- calls charged at the local rate, wherever the caller is, e.g. 08457 484950, the National Rail Enquiries number
    • - 0870 xxxxxxx -- calls charged at the national rate, wherever the caller is.
  • 09xxx xxxxxx - Premium rate services (no maximum call rate).

The few telephone numbers which are less than eleven digits long are mostly in the 0845 range, e.g. 0845 1111 the national Childline child abuse line, and 0845 4647 for NHS Direct medical advice.

The national emergency services call number is 999, although the international number 112 is also recognised.

The operator is obtained via 100, while directory enquiries, formerly 192 is now provided by different companies in the 118xxx range e.g. 118500, 11 88 88. International lines are accessed via the code 00. The leading zero of an area code indicates that the number being dialled is non-local.

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