Area code split: Difference between revisions

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{{short description|Method of central office code relief in the NANP}}

{{Unreferenced|date=July 2008}}

{{more citations needed|date=May 2021}}

In [[telecommunications]], aan '''splitarea plancode split''' is the practice of introducing a new telephone [[area code]] by geographically dividing an existing [[numbering plan area]] (NPA), and assigning a new area codecodes to one of the resulting divisions, andbut retaining the existing area code only for one area, which is typicallyof the traditionally more developed or established placedivisions. The practice serves the purpose of preventingthis telephonepractice numberis exhaustionto inprovide regionsmore of[[central highoffice growth.prefix]]es, Theand increasingtherefore demand formore [[telephone numbers has been primarily caused by increasenumber]]s, in usean ofarea pagers,with faxhigh machinesdemand duringfor thetelecommunication 1990sservices, and proliferationprevent ofa cellphonesshortage andof [[smarttelephone phone]]s sincenumbers.

An increasing demand for telephone numbers has existed since the development of automatic telephony in the early 20th century, but was spurred especially since the 1990s, with the proliferation of fax machines, pager systems, mobile telephones, computer modems and, eventually, [[smart phone]]s.

After a numbering plan split is implemented, the telephone numbers in the affected area are changed to a new area code, which requires the printing of new stationery, advertisements, and signage; the dissemination of the new numbers to family, friends, and customers; and the subsequent need to update speed dial programming and address books. Auxiliary devices, such as cellphones, pagers, and fax machines, must be reprogrammed when an area code splits. In a number of areas, rapid growth during the late decades of the 20th century resulted in several splits within a short time, in some cases within a decade.

The implementation of an area code split typically involves the establishment of a [[Class-4 telephone switch|Class-4 toll switching center]] for each division of the existing numbering plan area that receive a new area code. The local seven-digit telephone numbers in any of the areas are typically not changed. The existing central office prefixes are maintained and only the central offices of the new divisions are reassigned to a new area code. The impact of a split on the general public involves 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, speed dialing directories, and other automated equipment.

As a result, in the mid-1990s, the [[North American Numbering Plan]] Administrator introduced another method called [[overlay plan]], which assigns multiple area codes to the same numbering plan area. This permits customers to keep existing telephone numbers, but it requires [[ten-digit dialing]] for customers of both area codes. Since 2007, most territories use overlays for mitigating numbering shortages.

Since area code splits have substantial impact in the involved communities, and involve substantial cost in telephone plant and exchange equipment, they are planned carefully well ahead of implementation with the intent that an area is not again affected by a subsequent realignment for at least a decade.<ref name="notes1975">AT&T, ''Notes on the Network'' (1975), Section 2</ref>

The new boundaries of the numbering plan areas are drawn in a manner that minimizes splitting communities and should coincide with political subdivision where practical.<ref name="notes1975" /> Other geographic features, such as rivers and bodies of water, mountain ranges, or highways may serve as guides for boundary placements. Tributary toll telephone routes should not be unduly cut, so prevent rerouting to new toll center switching systems.

The area that retains the existing area code is typically the largest, or historically more established or developed place, but the locations of large government bodies or other criteria may affect this decision.

==Area code overlays==

{{main|Overlay complex}}

Not withstanding the desire for long-term stability of the local numbering plan and customer understanding, rapid growth in some areas has resulted in many splits within just a few years.

As a result, in the early 1990s, the [[North American Numbering Plan Administrator]] (NANPA) introduced another method for exhaustion relief: the 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]] of local calls for customers of both area codes. Since 2007, most territories use overlays for mitigating numbering shortages. Most area code relief plans today do not even consider splits as relief options.<ref>{{Cite report |url=https://www.nationalnanpa.com/reports/2021_NANPA_Annual_Report.pdf |title=2021 NANPA Annual Report |last=North American Numbering Plan Administrator |date=March 2022}}</ref>

==See also==

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*[[Number pooling]]

*[[Permissive dialing]]

*[[sevenSeven-digit dialing]]

*[[Telephone exchange]]

==References==

{{reflist}}

[[Category:Telephone numbers]]