Area code split
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In telecommunications, an area code split is the practice of introducing a new telephone area code by geographically dividing an existing numbering plan area (NPA), and assigning area codes to the resulting divisions, while retaining the existing area code only for one of the divisions. The purpose of this practice is to provide more central office prefixes, and therefore more telephone numbers, in an area with high demand for telephone services, and prevent a shortage of telephone numbers.
An increasing demand for telephone numbers has existed since the development of automatic telephony in the early 20th century, but was spurned especially since the 1990s, with the proliferation of fax machines, pager systems, mobile telephones, computer modems, and finally smart phones.
When an area code split is implemented, the telephone numbers in the affected area are typically changed to a new area code only, but this still requires the printing of new stationery, advertisements, and signage for many customers, and the dissemination of the new area code to family, friends, and customers. Computer systems, and telephone equipment may require updates in address books, and for speed dialing.
The area that retains the existing area code is typically the largest, or historically more more established or developed place.
Area code splits are typically planned well ahead of actual changes and are typically designed with respect to local municipal boundaries and the goal of providing stability in the numbering of an area for a period of ten years, if possible. Nevertheless, rapid growth in some areas has resulted in several splits within a much short time period.
As a result, in the mid-1990s, the North American Numbering Plan Administrator introduced another method for exhaustion relief, called area code overlay. This method assigns multiple area codes to the same numbering plan area, so that existing subscribers can keep established telephone numbers. Only new accounts and extra lines receive telephone numbers with the new area code. This method requires ten-digit dialing for customers of both area codes, even for local calls. Since 2007, most territories use overlays for mitigating numbering shortages.