Science Fair Project Encyclopedia
Telephone numbering plan
A telephone numbering plan is a system that allows subscribers to make and receive telephone calls across long distances.
The area code is that part of the dialed telephone number that specifies a telephone exchange system. Telephone numbering plans assign area codes to exchanges, so that dialers may contact telephones outside their local system. Normally occurring at the beginning of the number, area codes usually indicate geographical areas. Together, numbering plans and their component area codes direct 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.
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, many 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. 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 US; 1 digit in Australia.
- A variable length, e.g. between 2 and 5 in Germany and in Austria; between 1 and 3 in Japan; 1 or 2 in Israel.
- 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 dialled, as in Belgium, Switzerland and South Africa.
In many cases the area codes determine the rate (price) of a call. For example, in North America 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 "more 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.
Open numbering plans
An open numbering 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 only dial 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 Amsterdam in the Netherlands for example:
xxx xxxx (within Amsterdam- no area code required) (020) xxx xxxx (outside Amsterdam) +31 20 xxx xxxx (outside the Netherlands)
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 (mobile phones within NANP) +1 415 xxx xxxx (outside NANP)
However, in parts of North America, especially where a new area code overlays an older area code, dialing 1 + 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 that the area code is always necessary, but not the trunk code; this is true regardless of the phone's area code.
Closed numbering plans
A closed numbering plan is one in which the subscriber's number is a standard length, and 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 +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)
Paris 01 xxxx xxxx (outside France +33 1 xxxx xxxx) Brussels 02 xxx xxxx (outside Belgium +32 2 xxx xxxx) Geneva 022 xxx xxxx (outside Switzerland +41 22 xxx xxxx) Cape Town 021 xxx xxxx (outside South Africa +27 21 xxx xxxx)
While the use of full national dialing is less user-friendly than only using 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:
+420 2 xxxx xxxx formerly: 02 xxxx xxxx (inside Czech Republic) +420 2 xxxx xxxx (outside Czech Republic)
Numbering plans by country
Main article: Argentine telephone numbering plan
Country Code: 54
Main article: Australian telephone numbering plan
Country Code: 61
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, some of which covering more than one state and territory. 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 six digits in other areas with a two-digit area code. There were more than sixty such codes by 1990, spurring the reorganization.
02 New South Wales and Australian Capital Territory 03 Victoria and Tasmania 04 Mobile phone services 07 Queensland 08 Western Australia (including Christmas Island and Cocos Keeling Islands), South Australia and Northern Territory.)
The system is not perfect; the codes do not strictly follow state borders. For example, Broken Hill in New South Wales is in the 08 area code, due to its proximity to the South Australian border.
The main international prefix is 0011. 000 is the emergency telephone number in Australia, but the internationally accepted GSM mobile emergency telephone number 112 also works on mobile phones.
Telephone numbers within Australia are allocated by the Australian Communications Authority.
Country Code: 55
In Brazil, long distance and international dialling requires the use of carrier selection codes, after the trunk code or international access code.
For example, to call Rio de Janeiro from another city in Brazil, one would dial the trunk code '0', a two-digit code, the area code '021' and the subscriber's number. Consequently, a Rio de Janeiro number would be displayed in Brazil as
0xx21 nnnn nnnn.
A few areas use nnn-nnnn in lieu of nnnn nnnn, such as such as Natal (area code for that state is '84', in the state of Rio Grande do Norte, in northeastern Brazil. However, this practice will be phased out in 2006.
xx is the two-digit Operator Code for long distance calls:
- 15 for Telefónica
- 21 for Embratel
- 23 for Intelig
and some others.
Outbound international dialing in Brazil
00xx 1 212 xxx xxxx.
The current carriers (the two digits you should dial after the "0") are:
Embratel : 21 Intelig : 23 Telemar: 31 Brasil Telecom *: 14 Telefônica : 15 Claro**: 36 TIM**: 41 CTBC*: 12 GVT*: 25 Vesper São Paulo*: 89 Vesper Norte-Leste*: 85 Sercomtel*: 43
Those marked with an asterisk (*) are only avalaible to certain areas. The ones with "**" are to be used with mobile phones only.
Area codes are distributed geographically. See List of Brazilian area codes.
A note about mobile telephony in Brazil
Mobile phone numbers are usually prefixed with the digit '7', '8' or '9'. '7' is used mainly for radiophone use (iDEN technology).
Numbers with an '8' are always GSM Mobiles, while '9' can be mostly analogue (AMPS), TDMA and CDMA mobiles. The prefix number in mobile telephony is related to the license the carrier has. On newer licenses, use of the '8' digit is mandatory, while the previously state-onwned mobile operators always uses '9'(or '7', in some cases in São Paulo area). Some GSM mobiles can be prefixed with a '9' because the now privatized operators decided to overlay using this technology.
Mobile phone numbers generally have eight digits. Exceptions exist in Brasilia.
Country Code: 86
Main article: Colombian telephone numbering plan
Country Code: 57
East Timor (Timor Leste)
Country Code: 670
The only authorized telephone and data carrier in East_Timor is Timor_Telecom , a company owned by Portugal_Telecom with 50.1% of the shares (source: Telecommunications Research Project at the University of Hong Kong).
The services are very limited and very, very expensive. According to a press-release issued by Portugal_Telecom , the total number of fixed phones (landline) are 2,100, mobile_cellular are 25,000, 500 Dial-up_access users and 30 broadband users (as of October 2004).
Portugal_Telecom signed a 15-year contract in 2002 to invest US$ 29 million to rebuild and operate the phone system. The contract could be extended by 10 more years, totalling 25 years of monopoly. 2003 gross revenue totalled € 10.5 million.
Telephone numbering plan in East Timor are as follows: Mobile: 670 72X-YYYY, where X could be 3, 4, 6 or 7 Service Numbers: 670 721-XXXX Fixed: 670 32X-YYYY, where X could be 2 or 3. Also refered as 670 390 32X-YYYY
Emergency Numbers: Ambulance Service: 110 Fire Dept: 115 Emergency: 112
European Union (1996 proposal)
Proposed Country Code: 3
In 1996, the European Commission proposed the introduction of a single telephone numbering plan, in which all European Union member states would use the code '3'. Calls between member states would no longer require the use of the international acces code '00'. This proposal would have required countries like Germany, the United Kingdom, Denmark and others, whose country codes began with the digit '4', to return these to the International Telecommunication Union. For example, to call a number in Berlin, in Germany:
xxxx xxxx (within Berlin) 030 xxxx xxxx (within Germany) 1 4930 xxxx xxxx (within the EU) +3 49 30 xxxx xxxx (outside the EU)
xxxx xxxx (within Dublin) 01 xxxx xxxx (within Ireland) 1 53 1 xxxx xxxx (within the EU) +3 53 1 xxxx xxxx (outside the EU)
A Green Paper on the proposal was published, but it was felt by many in the industry that the disruption and inconvenience of such a scheme would outweigh any advantages.
The EU proposal should not be confused with the European Telephony Numbering Space (ETNS) scheme, which uses the code +388, and is intended to complement, rather than replace, existing national numbering plans.
Country Code: 358
Before 1996: 90' xxx xxx within Finland +358 0 xxx xxx outside Finland
After 1996: 09' xxx xxx within Finland +358 9 xxx xxx outside Finland
The default international access code became 00, although other codes such as 999 are also still used.
Main article: French telephone numbering plan
Country Code: 33
In 1996, France changed to a ten-digit numbering scheme, as follows:
01 Paris 02 Northeast France 03 Northwest France 04 Southeast France 05 Southwest France 06 Mobile phone services 08 Freephone (numéro vert) and shared cost services.
Country Code: 49
Following German reunification in 1990, the former East Germany's code +37 was relinquished and returned to the ITU for reallocation. Similarly, the digit '3' is the initial digit for the new area codes in the former East Germany, while the area code 030 for West Berlin was used for the reunified city.
There are no standard lengths for either area codes or subscribers' numbers in Germany, meaning that some subscribers' numbers may be as short as three digits. Larger towns have shorter area codes permitting larger telephone numbers in that area. Some examples:
- (0)1*: service numbers and cell phones
- (0)30: Berlin
- (0)40: Hamburg
- (0)421: Bremen
- (0)89: München
- (0)800: toll free
- (0)900: premium rate
The default length for newly assigned numbers (area code without 0 + subscriber number) is 10 or 11 digits, but older shorter numbers will not be replaced, but not reassigned if given back. The Area Codes are, if not counting the national thunk prefix '0', from 2 Digits (only for Berlin +49 30, Hamburg +49 40, Frankfurt +49 69 and Munich +49 89) to 5 Digits in the former East Germany in +49 3. Area Codes in +49 2, +49 4 to +49 9 are up to 4 digits. 3 digit area codes of the form +49 XY1 where assigned to the cities, where the former central switching bords where placed (usually bigger cities). Exceptions from the numbering sceme exists in the rhein-ruhr-area, where many big cities can be found and in the former east.
Non-geographic numbers, including mobile phone services, are prefixed with '01' (+49 1 internationally). 0130 was originally used for toll-free numbers, but this has been changed to 0800. The prefix 0180 is used for shared cost services while 0700 is for personal numbers. Premium rate numbers use the prefix 0900 (the older prefix 0190 is being phased out); these are not accessible from outside Germany. Mobile numbers have area codes from (+49 15XX to +49 17X).
Geographic codes beginning with '02' (+49 2 internationally) are placed in the western part of the country, e.g. '0221' for Cologne (+49 221 internationally) or '0211' for Düsseldorf (+49 211 internationally), '03' (+49 3 internationally) as stated above in the former East Germany, '04' (+49 4 internationally) numbers in the north (e.g. Hamburg +49 40 oder Bremen +49 421), '05' (+49 5 internationally) numbers in the middle-north (e.g. +49 511 for Hanover or +49 521 for Bielefeld), '06' (+49 6 internationally) in the central parts (e.g. +49 69 for Frankfurt or +49 611 for Wiesbaden), '07'(+49 7 internationally) in the south-west (e.g. +49 711 for Stuttgart oder +49 721 for Karsruhe), '08' (+49 8 internationally)for the south-east (e.g. +49 89 for Munich oder +49 821 for Augsburg) and '09' (+49 9 internationally) in the south-east (e.g. +49 911 for Nuremberg or +49 921 for Bayreuth).
The international access code and the emergency services number are the European standard 00 and 112, respectively.
Country Code: 30
During 2001-2002, Greece moved to a closed ten-digit numbering scheme in two stages, with the result that subscribers' numbers changed twice. For example, before the change, a number in Athens would have been dialed as follows:
xxx xxxx (within Athens) (01) xxx xxxx (within Greece) +30 1 xxx xxxx (outside Greece)
In 2001, a '0' was added after the area code, which was incorporated into the subscriber's number:
010 xxx xxxx (within Greece, including Athens) +30 10 xxx xxxx (outside Greece)
Finally, in 2002, the leading '0' was changed to a '2' (for geographic numbers) :
210 xxx xxxx (within Greece, including Athens) +30 210 xxx xxxx (outside Greece)
Mobile phone numbers were similarly prefixed with the digit '6'.
Country Code: 852
Main article: Hong Kong telephone numbering plan
Country Code: 353
Telephone numbers in Ireland are similar in format to those in the United Kingdom, with only the subscriber's number being required for local dialing. The trunk prefix is '0' followed by an area code, the first digit indicating the geographical area.
01 Dublin 02 Cork (021) and South 04 Drogheda (041) and East 05 Waterford (051) and South East 06 Limerick (061) and South West 07 Sligo (071)and North West 09 Galway (091) and West
Area codes have varied in length, between one and three digits, and subscribers' numbers between five and seven digits but there is now a migration to a standard format, as follows:
(0xx) xxx xxxx
Dublin numbers are seven digits, but may change to eight digits in the future. The 08 numbering range was originally used for calls to Northern Ireland, but following the UK's renumbering of Northern Ireland in 2000, this changed, so to call a number in Belfast from the Republic:
Before 2000: (080) 1232 xxx xxx After 2000: (048) 90xx xxxx; or via the UK numbering plan; 00 44 28 90xx xxxx
Before 1992: 030 xxx xxx xxx After 1992: 00 44 xxx xxx xxx
Mobile phones use the prefixes 086, 087 and 088, with 0818 being used for 'find me anywhere' services. Freephone services use the prefix 1800, while shared cost or Lo-Call numbers use the prefix 1850. Internet access numbers use the prefix 1891, 1892 and 1893.
Country Code: 39
Italy changed to a closed numbering plan in 1998, with callers being told in to fissa il prefisso ("fix the prefix"). Unlike in other closed numbering plans the trunk code '0' was simply incorporated into subscribers' landline numbers; e.g. a number in Rome:
06 xxx xxxx (within Rome - after 1999) 06 xxx xxxx (within Italy) +39 06 xxx xxx (outside Italy - after 1998)
Calls to mobile phone numbers within Italy were also affected, deleting the previously used prefix '0' (as it was already happening for oversea callers); e.g. for Omnitel-Vodafone provider in Italy:
0347 xxx xxx (within Italy - before 1999) 347 xxx xxx (within Italy - after 1999) +39 347 xxx xxx (outside Italy)
Until 1996, San Marino was part of the Italian numbering plan, using the Italian area code 0549 but in that year it adopted its own international code 378. However,instead of using international dialing codes, dialling arrangements between San Marino and Italy continued as before. In 1998, San Marino incorporated the 0549 area code into its subscribers' numbers, following the Italian format:
0549 xxx xxx (San Marino from Italy) +378 0549 xxx xxx (San Marino from rest of the world) +39 0549 xxx xxx (San Marino via Italy)
Country Code: 81
Main article: Japanese telephone numbering plan
Country Code: 52
In 1999 Mexico introduced the following new prefixes long distance calls for long distance and international calls:
00 - international direct dialing (00 + country code + nat'l number)
including USA and Canada. 01 - domestic direct dialing (01 + area code + number) 02 - domestic person-to-person (02 + area code + number) 09 - international person-to-person (09 + country code + number)
including USA and Canada.
This did not affect calls from outside Mexico, which continued to be dialed in the same format, for example, to call a number in Mexico City:
+52 55 xxxx xxxx
Country Code: 31
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. Since renumbering in 1996, subscribers' numbers are now either six digits long, or in the larger towns and cities, seven digits.
010: Rotterdam 020: Amsterdam 030: Utrecht 040: Eindhoven 050: Groningen 06x: mobile phone number 0676: internet access number 070: The Hague 0800: toll free number 0900: premium rate call 0906: premium rate 112: emergency services number
Previously, 06 was used for toll-free and premium rate numbers, while 09 was used as the international access code, before this changed to 00.
Country Code: 64
Since 1993, land-line telephone numbers in New Zealand consist of a single-digit area code and seven-digit local numbers, the first three of which generally specify the exchange and the final four a line at that exchange. The long distance prefix is '0'.
There are five regional area codes, which must be used when calling outside the local dialing area, for example from Christchurch to Dunedin in the South Island, the '03' prefix must be dialed first. In many parts of the country, the old area code was incorporated into the new number, hence Nelson (055) xx xxx became (03) 55x xxxx .
03 the South Island and the Chatham Islands 04 Wellington Region except the Wairarapa and Otaki 06 the remaining southern and eastern North Island: - Taranaki - Manawatu-Wanganui except Taumarunui - Hawke's Bay - Gisborne - the Wairarapa and Otaki 07 the Waikato, the Bay of Plenty and Taumarunui 09 Auckland and Northland
Mobile phone numbers are prefixed with 02, followed by one digit and the subscriber's number, which is either six or seven digits, dialled in full, e.g. 025 xxx xxx or 027 xxx xxxx. Free call services generally use the prefix 0800 (although some use 0508) while local rate (usually internet access numbers) have the prefix 08xx. Premium rate services use the code 0900 followed by five digits.
The main international prefix is '00' (there are others for special purposes, such as 0161, for discounted rates). The emergency services number is '111'.
Country Code: 51
Also on that date, '9' was prepended to existing cellular/mobile numbers. Mobile subscriber numbers are now 8 digits in Lima (+51 1 9xxxxxxx) and 7 digits elsewhere (+51 xx 9xxxxxx).
Country Code: 351
Portugal changed to a closed numbering plan in 1999. Previously, the trunk prefix was '0', but this was dropped, and the area code, prefixed by the digit '2' was incorporated into the subscriber's number, so that a nine-digit number was used for all calls, eg:
xxx xxxx (within Lisbon) (01) xxx xxxx (within Portugal) +351 1 xxx xxxx (outside Portugal) +351 21x xxx xxx (after 1999)
Mobiles similarly changed, with the digits '96' replacing the prefix '0936':
0936 xxx xxx (within Portugal) +351 936 xxx xxxx (outside Portugal) +351 96 xxx xxxx (after 1999)
Other new number ranges include:
10xx Carrier selection codes 700 xxx xxx Personal numbering 8xx xxx xxx Geographic expansion 800 xxx xxx Freephone 80x xxx xxx Shared cost
Russia and Commonwealth of Independent States
Country Code: 7
Under the Russian numbering plan, the trunk code is '8', with subscribers numbers being a total of ten digits long, e.g Moscow:
xxx xxxx (within Moscow) 8 095 xxx xxxx (within Russia and some CIS republics) +7 095 xxx xxxx (outside Russia and some CIS republics)
Following the break-up of the former Soviet Union, all former republics apart from Kazakhstan now have separate international from Russia, although from some republics, the old area codes are still used. The international access code is 8~10 - callers dial '8', wait for a tone, and then dial '10', followed by the number.
Country Code: 34
Spain changed to a closed numbering plan in 1998. Previously, the trunk prefix was '9', but this was incorporated into the subscriber's number, so that a nine-digit number was used for all calls, eg:
xxx xxxx (within Madrid) (91) xxx xxxx (within Spain) +34 1 xxx xxxx (outside Spain) +34 91x xxx xxx (after 1998)
Mobiles similarly changed, prefixed with the digit '6':
906 xxx xxx (within Spain) +34 06 xxx xxx (outside Spain) +34 606 xxx xxx (after 1998)
New numbering ranges have also since been introduced:
10xx Carrier selection codes 700 xxx xxx Personal numbering 8xx xxx xxx Geographic expansion 800 xxx xxx Freephone 80x xxx xxx Shared cost
Spain's international access code also changed from 07 to 00, but this did not affect dialing arangements for calls to Gibraltar, in which the provincial code 9567 is used instead of the international code 350, eg:
9567 xxxxx (Gibraltar from Spain) +350 xxxxx (Gibraltar from all other countries) +34 9567 xxxxx (Gibraltar via Spain)
Country Code: 46
In Sweden, 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 eight to ten digits used. Before the 1990s, ten-digit numbers were very rare, but they have become increasingly common because of the deregulation of telecommunications, the new 112 emergency number, which required change of all numbers starting with 11, and the creation of a single area code for the Greater Stockholm area. No subscriber number is shorter than five digits.
010: NMT mobile phones 01x(x): South Middle Sweden 020: toll free 0200: toll free 02x(x): North Middle Sweden 03x(x): Central South Sweden 031: Gothenburg 040: Malmö 04x(x): Southern Sweden 05x(x): Western Sweden 055: Grums 06x(x): Northern Sweden 070: GSM mobile phones 071: Premium rate calls 073: GSM mobile phones 0730: GSM mobile phones 074(x): Pagers 076: GSM mobile phones 07x(x): various non-geographical area codes 08: Greater Stockholm 09x(x): Far Northern Sweden and premium rate calls 112: emergency services number
Sweden adopted 00 as its international access code in 1999, replacing 009 and 007.
According to the postal and telecommunication services supervising authority Post- och Telestyrelsen, it seems possible that Sweden will adopt a closed numbering plan in the future.
Country Code: 41
In 2002, Switzerland adopted a closed numbering plan, but retained the use of the trunk code 0. The original plan was to dispense with the trunk code completely, so that all calls within Switzerland would only require a nine-digit number. However, this was modified on grounds of cost. The 01 prefix for numbers in Zurich is being phased out in favor of 044, with 043 being used for overlay numbers.
Until 1999, Liechtenstein formed part of the Swiss numbering plan, using the area code 075, but in that year it adopted its own international code 423, meaning that calls to and from Switzerland require international dialing.
The 07 number range is now used for mobile phone services.
Country Code: 44
Main article: UK Telephone Numbering Plan
Since April 28, 2001, the overall structure of the UK's National Numbering Plan is:
01 Geographic area codes 02 Geographic area codes (newly introduced in 2000) 03 Reserved for area codes 04 Reserved 05 Reserved for corporate numbering and VoiP services. 06 Reserved 07 "Find Me Anywhere" services (mobile phone, pager & personal numbers) 08 Freephone (toll free), Local & National Rate numbers 09 Premium Rate services and multimedia
A short list of examples, set out in the officially approved (Ofcom) number groups:
020 xxxx xxxx: London 028 xxxx xxxx: Northern Ireland 029 xxxx xxxx: Cardiff 0131 xxx xxxx: Edinburgh 01382 xxx xxx: Dundee, a typical area code
In the United Kingdom, area codes are — including the leading '0' which is dropped when calling UK numbers from overseas — three, four, or five digits long, with larger towns and cities having shorter area codes permitting a larger number of telephone numbers in the eleven digits used. Area codes are sometimes still called "STD" (subscriber trunk dialling) codes.
United States and Canada
- Main article: North American Numbering Plan
- See also: List of North American area codes
In the United States and Canada, area codes are regulated by the North American Numbering Plan. Currently, all area codes (officially called numbering plan areas) 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.
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). N11 codes (such as 911) are not eligible to be used as area codes.
Not all area codes correspond to a geographical area. Codes 8xx (excluding 811 and 899) 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, although such services also exist in some places on a local basis using a particular three-digit prefix following the area code, often "976"). Area code 710 has been reserved for the United States Government, although no lines other than the single telephone number 710-627-4387 ("NCS-GETS") had actually been connected on this code as of 2004.
None of these changes enable the existence of variable length area codes, which are commonplace outside North America. Also see .
There are several noteworthy peculiarities in the NANP:
- In many localities, all calls must include an area code, even when calling within the same area. For example in large urban areas, a 'local' call may be in another area code, or two area codes may overlay the same geography. In most cases a "1" needs to be dialed before the area code as well. As new area codes are being required, this is becoming more common.
- Mobile phones are allocated numbers within regular geographic area codes corresponding (usually) to the subscriber's home or work location, instead of within a distinctive subset of area codes (e.g. 07xxx in the UK).
Since a calling party cannot reliably distinguish between landline and mobile phone numbers, this forced NANP cellular telephone carriers into a charging model wherein the cellular subscriber usually pays for all airtime on his/her phone, whether placing or receiving a call, as opposed to the distinctive-subset model in which callers are usually charged at a higher rate ("caller-pays") for dialing mobile numbers than landlines. Some have cited this "receiver-pays" model as a reason for the US's relatively slow adoption rate of cellular telephony in the 1990s, compared to that in Europe and the Pacific Rim, though this has been largely countered by the post-2000 prevalence of free long-distance calling (to cellular or landline phones) on nearly all US cellular plans.
Alphabetic mnemonic system
Another oddity of NANP 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 omitted, though on some modern telephones, they are added, so that the alphabet is apportioned as follows:
2 = ABC 3 = DEF 4 = GHI 5 = JKL 6 = MNO 7 = P(Q)RS 8 = TUV 9 = WXY(Z)
No letters are allocated to the 1 or 0 keys (although some corporate voice mail systems are set up to count Q and Z as 1, and some old telephones assigned the Z to the digit 0).
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 made seven digits long, including a two-digit prefix, the latter expressed as letters rather than numbers. (Before World War II, many localities used three letters and four numbers, and in much of California during this period, phone numbers had only six digits — two letters followed by four numbers.) The prefix was a name, and the first two or three letters (usually shown in capitals) of the name were dialed. Later, the third letter (where previously used) was replaced by a number; this generally happened after World War II, although New York City did this in 1930. Thus, the famous Glenn Miller tune "PEnnsylvania 6-5000" refers to a telephone number 736-5000, the number of the Hotel Pennsylvania, which still bears the same number today. Similarly, the classic Elizabeth Taylor film "BUtterfield 8" refers to the section of New York City where the film is set, where the telephone prefixes include 288 (on the East Side of Manhattan between roughly 64th and 86th Streets). One Wikipedia 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 an eighth (or more) digit is dialed, the switching system will ignore it.
- World Telephone Numbering Guide
- Free Area Code Listing (US and Canada)
- North American Numbering Plan Administration (NANPA)
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details