Telephone numberwikipedia
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.
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Telephone numbering plan

Area codeCalling codearea codes
Telephone numbers are assigned within the framework of a national or regional telephone numbering plan to subscribers by telephone service operators, which may be commercial entities, state-controlled administrations, or other telecommunication industry associations.
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 exchange names

telephone exchange namescentral office nametelephone exchange
Over the course of telephone history, telephone numbers had various lengths and formats, and even included most letters of the alphabet in leading positions when telephone exchange names were in common use until the 1960s.
Each central office served a maximum of 10,000 subscriber lines identified by the last four digits of the telephone number.

Telephone

telephonephonetelephones
In addition to telephones, they have been used to access other devices, such as computer modems, pagers, and fax machines.
In addition, most telephones contain a ringer, which produces a sound to announce an incoming telephone call, and a dial or keypad used to enter a telephone number when initiating a call to another telephone.

Telephone line

telephone linephone lineline
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.
This is the physical wire or other signaling medium connecting the user's telephone apparatus to the telecommunications network, and usually also implies a single telephone number for billing purposes reserved for that user.

Vertical service code

vertical service codecalling featureservice feature
Telephone numbers are often dialed in conjunction with other signaling code sequences, such as vertical service codes, to invoke special telephone service features.
Some vertical service codes require dialing of a telephone number after the code sequence.

List of country calling codes

Country CodeDialing codeTelephone code
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.
Country codes are a component of the international telephone numbering plan, and are necessary only when dialing a telephone number to establish a call to another country.

Ten-digit dialing

ten-digit dialing10-digit dialingten-digit dialling
If the area has no area code overlays or if the provider allows it, seven-digit dialing may be permissible for calls within the area, but some areas have implemented mandatory ten-digit dialing.
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.

North American Numbering Plan

Area codeArea codes<span style="white-space:nowrap;">Area code(s)
The format and allocation of local phone numbers are controlled by each nation's respective government, either directly or by sponsored organizations (such as NANPA in the US or CNAC in Canada).
Each telephone is assigned a seven-digit telephone number unique only within its respective plan area.

Local number portability

local number portabilitynumber portabilityported
Local number portability (LNP) allows a subscriber to request moving an existing telephone number to another telephone service provider.
Local number portability (LNP) for fixed lines, and full mobile number portability (FMNP) for mobile phone lines, refers to the ability of a "customer of record" of an existing fixed-line or mobile telephone number assigned by a local exchange carrier (LEC) to reassign the number to another carrier ("service provider portability"), move it to another location ("geographic portability"), or change the type of service ("service portability").

List of international call prefixes

International call prefixinternational access code+
When calling an international number from a landline phone, the + must be replaced with the international call prefix chosen by the country the call is being made from.
The international dialing prefix must be dialed before the country calling code and the destination telephone number.

Mobile number portability

mobile number portabilitynumber portabilitycarry their original phone number with a new provider
In some places, such as the UK, whereas landlines are arranged by location, all cell phone numbers are in a different prefix ranges, which permits full mobile number portability, even between carriers, and calling party pays.
Mobile number portability (MNP) enables mobile telephone users to retain their mobile telephone numbers when changing from one mobile network carrier to another.

E.164

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In the international telephone network, the format of telephone numbers is standardized by ITU-T recommendation E.164.
E.164 defines a general format for international telephone numbers.

E.123

Microsoft's canonical address format
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.
It provides guidelines for the presentation of telephone numbers, email addresses, and web addresses in print, on letterheads, and similar purposes.

Request line

request linecontest line
Other special phone numbers are used for high-capacity numbers with several telephone circuits, typically a request line to a radio station where dozens or even hundreds of callers may be trying to call in at once, such as for a contest.
Although only one telephone number is usually announced, major stations typically have line hunting, with the same number being directed to any available one of several lines within the hunt group.

555 (telephone number)

555 (telephone number)555555 telephone number
The use of numbers starting in 555- (KLondike-5) to represent fictional numbers in U.S. movies, television, and literature originated in this period.
The telephone number prefix 555 is a central office code in the North American Numbering Plan, used as the leading part of a group of 10,000 telephone numbers, 555-XXXX, in each numbering plan area (NPA).

Telephone exchange

telephone exchangeexchangescentral office
Telephone numbers are entered or dialed by a calling party on the originating telephone set, which transmits the sequence of digits in the process of signaling to a telephone exchange.
For example, one switch might send only the last four or five digits of a telephone number.

Directory assistance

directory assistancedirectory enquiries118 500
The "555" prefix was reserved for telephone company use and was only consistently used for directory assistance (information), being "555-1212" for the local area.
In telecommunications, directory assistance or directory enquiries is a phone service used to find out a specific telephone number and/or address of a residence, business, or government entity.

Telephone call

telephone callcallphone call
A telephone number serves as an address for switching telephone calls using a system of destination code routing.
Fees depend on the provider of the service, the type of service being used (a call placed from a landline or wired telephone will have one rate, and a call placed from a mobile telephone will have a different rate) and the distance between the calling and the called parties.

PEnnsylvania 6-5000

telephone number
According to the hotel's website, PEnnsylvania 6-5000 is New York's oldest continually assigned telephone number and possibly the oldest continuously-assigned number in the world.
PEnnsylvania 6-5000 is a telephone number in New York City, written in the 2L+5N (two letters, five numbers) format that was common in the largest US cities from approximately 1930 into the 1960s.

Short code

short codeshortcodeCommon short code
Short codes, or short numbers, are short digit sequences, significantly shorter than telephone numbers, that are used to address messages in the Multimedia Messaging System (MMS) and short message service (SMS) systems of mobile network operators.

Rate center

rate centerrate centre
Number portability usually has geographic limitations, such as an existing local phone company only being able to port to a competitor within the same rate centre.

National conventions for writing telephone numbers

Telephone number formats
The presentation of telephone numbers in this article does not include any international dialing codes necessary to route calls via international circuits.

Automatic number announcement circuit

automatic number announcement circuitANACautomatic number announcement
An automatic number announcement circuit (ANAC) is a component of a central office of a telephone company that provides a service to installation and service technicians to determine the telephone number of a line.

Phoneword

phonewordmnemonicphone word
Phonewords are mnemonic phrases represented as alphanumeric equivalents of a telephone number.

Automatic number identification

automatic number identificationANIthe caller's number
Automatic number identification (ANI) is a feature of a telecommunications network for automatically determining the origination telephone number on toll calls for billing purposes.