Current Listings

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Suspended Relief Activity 

Activation Dates Pending

 

Types of Area Code Relief

split.gif (915 bytes)  NPA Split

For over fifty years, this was the traditional form of NPA relief. A portion of an existing NPA is given a new NPA, with a new geographic boundary separating the two. All existing numbers in the split area must change to the new area code. There is usually a "permissive dialing" period during which numbers in the split area may be reached using either the old or the new area code. Once the split becomes mandatory, however, dialing a number in the split area by using the old area code will either reach an intercept recording, or reach a wrong number once the prefix is reassigned in the old area code. In the example above yellow is split into yellow and red codes.
 

3waysplit.gif (924 bytes)  Three-Way NPA Split

This relief plan is a simple variation on the traditional geographic split. The only difference is that two new area codes are introduced simultaneously. In the example above yellow is split into yellow, blue and red codes.
 

realignment.gif (913 bytes)  Boundary Realignment

In a realignment, a portion of one NPA is moved into an adjacent NPA. This technique does not provide significant long-term relief, since it simply shifts the problem from one NPA to another. However, it has been used in conjunction with other relief methods. In the example above yellow exchanges are shifted into the adjacent green NPA code.
 

overlay.gif (893 bytes)  NPA Overlay

In this method, a new area code is introduced into exactly the same geographic territory currently served by an existing area code. New prefixes from the new area code are assigned right alongside existing prefixes in the old area code. Existing numbers do not change. However, to minimize customer confusion, all calls within an overlay area -- even local calls within the same area code -- must be dialed with the area code. Also, the possibility exists that two phone lines in the same building may have different area codes. Once an overlay is instituted in a given geographic area, any further expansion is accomplished simply by adding further overlay area codes to the same territory. In the example above yellow is overlain with red, creating a possibility of an "orange household" comprised of two area codes.
 

concentrate.gif (906 bytes)  Concentrated NPA Overlay

A variation on the overlay, this method overlays only a portion of the existing NPA. While people in the overlay area are obligated to dial the entire number, people outside the overlay area (but still in the same NPA) can get away with dialing exchange and number. In the example above yellow is only partially overlain by red.
 

moverlay.gif (937 bytes)  Multiple NPA Overlay

In this overlay method, a new area code is introduced into exactly the same geographic territory currently served by TWO existing adjacent area codes. Generally, the entire boundary line between the two old codes is erased, creating a three-code overlay. In the example above yellow and red are overlain with a third blue code.
 

combo.gif (924 bytes)  Combination Split / Overlay

As the name implies, this is a complex relief method that involves elements of a split and overlay. A section of the existing code is split off to a new code, while the remainder is overlain. This can involve either a single code for both activities (as is the case in 407/321 in Florida), or two new codes (as is the case in the 909/752/951). In the example above yellow is split into yellow and red codes, while the remaining yellow is overlain by a third green code..
 

Area Code / Central Office Relief Lists

Most of the lists contained herein are regularly updated from various sources, including (but not limited to):

  • BellCore / Lockheed Martin / NANPA / Neustar

  • Local Exchange Carriers (LECs)

  • Regional Bell Operating Companies (RBOCs)

Additional thanks go out to the following for submitting new information, as well as supplying historical data that makes this list the most complete compilation available today.