An
area code is a numerical code that directs
telephone calls to particular regions on a public switched network (
PSTN), where they are further routed by the local network.
While the E.164 standard regulates country codes at the international level, it is each country's responsibility to define the numbering within its own network. As a result, area codes may have:
- A fixed length, e.g. 3 digits in the US; 2 digits in Australia.
- A variable length, e.g. between 2 and 5 in Germany and in South Africa; between 1 and 3 in Japan.
- Or be omitted altogether, as is the case in many countries, such as France, where the whole country is in effect a single "area".
In many cases the area codes determine the rate (price) of a call. For example, in the US calls to the 800, 888, and 877 areas are free to the caller and paid by the receiver, while calls to the 900 area are "premium rate", which means "very 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.
There are two noteworthy peculiarities in the US numbering:
- In some cases you need to dial the area code even when calling within the same area.
- Mobile phones are allocated numbers within regular area codes, instead of special area codes. This, together with the lack of a single cellular standard in the US, is often cited as a reason for the relatively low penetration of cellular telephony in the US.