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нумерация телефонов

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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 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, some 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 and sets a maximum length limit on a full international phone number. 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 United States and Canada; 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, or price, of a call. Calls within an area are normally charged at a lower rate than outside the area. There are many exceptions, however. In a densely populated area in the United States, a call to a different area code may well be a local call. And in Israel, calls are charged at the same rate regardless of area. In North America calls to the 800, 888, 877, and 866, the "toll free" area codes, are free to the caller, with the receiving party paying the charges. On the other hand, calls to the 900 area code incur a special charge collected by the phone company on behalf of the receiving party. Such 900 numbers are usually used as a fee-based method of providing information or entertainment to the caller.