Telephone number

A telephone number is a string of decimal digits that uniquely indicates the network termination point. The number contains the information necessary to route the call to this point. Telephone numbers are often assigned to lines that have other devices hooked to them such as faxes, modems, subscribers and network services. Each such endpoint must have a unique number within the public switched telephone 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. Some special services have their own short numbers (e.g. 9-1-1, 4-1-1 and 1-1-2).

Related Topics:
String - Decimal - Fax - Modem - Subscriber - Public switched telephone network - 9-1-1 - 4-1-1 - 1-1-2

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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.

Related Topics:
International telephone network - ITU-T - E.164 - Country prefix - Area code - Telephone switch - E.123

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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 overseen by NeuStar Inc.) See Telephone numbering plan.

Related Topics:
Format - NANPA - NeuStar Inc.

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

Related Topics:
Telephone call - Dial - Calling party - Caller - Called party - Caller ID

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