Overlay plan

overlayoverlaidoverlay area codeoverlay codeconcentrated overlayarea code overlayoverlayssharing the service areacode overlaycover the same geographic region
In telecommunications, an overlay plan is a telephone numbering plan that assigns multiple area codes to a geographic numbering plan area (NPA).wikipedia
245 Related Articles

Area codes 613 and 343

613613, 343343
It shared the same calling area as Hull, its twin city in Quebec, even though Ottawa was in area code 613 and Hull was in area code 819.
Area code 613 and overlay area code 343 are area codes for Ottawa and surrounding Eastern Ontario, Canada, in the North American Numbering Plan (NANP).

Telephone numbering plan

Area codeTelephone codearea codes
In telecommunications, an overlay plan is a telephone numbering plan that assigns multiple area codes to a geographic numbering plan area (NPA).
In North America ten-digit dialing is required in areas with overlay plans.

Central office code protection

exchange code protectioncode protection
The entire area implemented a system of central office code protection in which no central office code was duplicated in the entire area.
It has been declining in use as inefficient allocation of numbering resources to the growing number of competitive local exchange carriers has caused depletion of available number prefixes, often requiring ten-digit local calls or overlay plans where multiple area codes serve the same geographic location.

Area code 206

206area code
For example, the original area code for the entire state of Washington was 206, which, however, now applies only to the city of Seattle and the immediate vicinity.
As of January 2017, this numbering plan area was one of the last urbanized areas in the North American Numbering Plan without a code overlay, meaning telephone calls within Seattle could still be originated by seven-digit dialing.

Split plan

split
The practice became known as a split plan.
As a result, in the mid-1990s, the North American Numbering Plan introduced overlay plans, which apply multiple area codes to the same area.

Area code 917

917
The first use of that solution was in New York City, where area code 917 was overlaid onto Manhattan's 212 and the outer boroughs' 718.
It is an overlay code to all numbering plan areas (NPAs) in the city, and was intended to serve cellular, pager, and voicemail applications in the city, a restriction that was subsequently ruled impermissible by the Federal Communications Commission (FCC) while grandfathering that use in New York City.

Area codes 212, 646, and 332

212, 332, 646212area code 212
The first use of that solution was in New York City, where area code 917 was overlaid onto Manhattan's 212 and the outer boroughs' 718.
In 1992, the entire city was overlaid with area code 917, which originally had been planned for only the Bronx and mobile service.

Local call

local phone calls
Most overlay plans introduced the inconvenience of mandatory ten-digit dialing in which the area code must always be included even for local calls.
However, this is not true in parts of the United States and Canada that are subject to overlay plans or many countries in Europe that require closed dialing plans.

List of California area codes

Area code(s)Area codes in CaliforniaCalifornia
Connecticut, Illinois, Oregon, New Jersey, Massachusetts, Maryland, Pennsylvania, Texas, and, more recently, California have also implemented many overlays.

List of Georgia area codes

Area codes in the state of GeorgiaGeorgialist
For example, much of Ohio is covered by large overlay complexes, as is northern Georgia.
678 was given to both the city and its suburbs in January 1998, becoming the first overlay area code in the state, and forcing mandatory ten-digit dialing for all calls.

List of Pennsylvania area codes

listPennsylvania
Connecticut, Illinois, Oregon, New Jersey, Massachusetts, Maryland, Pennsylvania, Texas, and, more recently, California have also implemented many overlays.
223: An overlay of 717

Area codes 208 and 986

208986area code 208
Idaho followed that precedent in 2017 by overlaying area code 208 with 986.
It was Idaho's sole area code until 2017, when 986 was added as an overlay plan for the entire state.

Area codes 514 and 438

514 and 438(514) and (438)514
Those are some of the reasons that the numbering plan areas corresponding to four of the five largest Canadian markets (416 in Toronto, 514 in Montreal, 604 in Vancouver, and 403 in Calgary) were split in the 1990s.
The area codes are assigned in an overlay plan to a territory that includes the Island of Montreal, Île Perrot, and Île Bizard in the province of Quebec.

Ten-digit dialing

10-digit dialingten-digit diallingten digits
Most overlay plans introduced the inconvenience of mandatory ten-digit dialing in which the area code must always be included even for local calls.
The introduction of overlay plans as a means to reduce the need for phone numbers to change as a result of adding new area codes meant that one geographic area could be associated with more than one area code.

Area codes 905, 289, and 365

905 and 289905905, 289, 365
The area code for Metro Toronto, 416, was on the verge of exhaustion only five years after the suburbs had split off as area code 905 in 1993.
905 is the main area code, while 289 and 365 are overlay codes covering the same territory.

Area codes 304 and 681

304 & 681304304/681
The first example of an entire state served by only a single until it was overlaid is West Virginia, which had been served with area code 304 since the inception of the North American Numbering Plan.
It was overlaid with area code 681, effective March 28, 2009.

Area codes 416, 647, and 437

416416, 647416, 647, 437
Those are some of the reasons that the numbering plan areas corresponding to four of the five largest Canadian markets (416 in Toronto, 514 in Montreal, 604 in Vancouver, and 403 in Calgary) were split in the 1990s.
Another option was an overlay area code covering the same area as 416.

Area code 807

807
By 2013, seven-digit dialing had been eliminated in every Canadian numbering plan area except in the country's three Arctic territories (area code 867), a large but sparsely-populated area in northwestern Ontario (area code 807), New Brunswick (area code 506), and Newfoundland and Labrador (area code 709).
In the early 21st century, as 705 neared exhaustion, CNAC briefly considered "erasing" the 807-705 boundary and turning 807 into an overlay for all of Ontario north and west of the Golden Horseshoe.

Area code 604

604+1-604area code
Those are some of the reasons that the numbering plan areas corresponding to four of the five largest Canadian markets (416 in Toronto, 514 in Montreal, 604 in Vancouver, and 403 in Calgary) were split in the 1990s.
On November 3, 2001, area code 778 was implemented as a concentrated overlay for the two largest regional districts in the Lower Mainland, Metro Vancouver and the Fraser Valley Regional District.

Area codes 778, 236, and 672

778236672
Area codes 778, 236, and 672 are overlay area codes for the Canadian province of British Columbia.

Area codes 587 and 825

587+1-587587, 825
The new area codes overlay 403 and 780 simultaneously, covering the entire province, and make 10-digit dialing necessary throughout Alberta.

Area code 312

312312 area codearea code
Both area codes are overlaid with area code 872.

Area codes 713, 281, 346, and 832

281713832
713 is the main area code, while 281, 832 and 346 are overlay codes covering the same area.

Area code 564

564
Area code 564, originally planned for introduction in October 2001, was canceled in August 2001 after state regulators determined that the use of number pooling had allowed existing numbers in western Washington to be used more efficiently.
It is an overlay plan for area codes 206, 253, 360, and 425.

List of area code overlays

The North American Numbering Plan Administration maintains the definitive list of overlay plans of area codes in the United States.