Split plan

split
In telephony, a split plan is the practice of introducing a new area code by dividing an existing area code's territory and applying the new area code to one of the resulting divisions, replacing the existing area code within that section.wikipedia
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Overlay plan

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

Ten-digit dialing

10-digit dialingten-digit diallingten digits
They allow customers to keep existing phone numbers, but require 10-digit dialing in the affected area.
Code protection is not possible for calls across area code boundaries within split plan cities where area codes have been added due to a shortage of available local numbers; these local calls became ten digits when the code was split.

Number pooling

Number pooling
The new area codes brought an initial flood of split plans which changed millions of existing numbers.

Permissive dialing

permissive dialling
Permissive dialing
When an area is given a new area code under a split plan, the area's previous area code would no longer be valid for calls in the area, so calls to numbers using the old area code will not work.

Telephony

digital telephonytelephonedigital
In telephony, a split plan is the practice of introducing a new area code by dividing an existing area code's territory and applying the new area code to one of the resulting divisions, replacing the existing area code within that section.

Telephone numbering plan

Area codeCalling codearea codes
In telephony, a split plan is the practice of introducing a new area code by dividing an existing area code's territory and applying the new area code to one of the resulting divisions, replacing the existing area code within that section.

Stationery

stationerschool suppliesstationers
After a split plan is implemented, the telephone numbers in an affected area are changed to a new area code, requiring printing of new stationery, advertisement, and signage, and the dissemination of new numbers to family, friends, and customers and their subsequent need to update speed dial programming and address books.

North American Numbering Plan

Area codeArea codesArea code(s)
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 codes 905, 289, and 365

905 and 289905905, 289, 365
Area code 905 was assigned on October 4, 1993, as a split from area code 416.

Area code 850

850
Area code 904 was used for all of North Florida from 1965, when 904 split from 305, until 904 itself was split in the mid-1990s.

North American Numbering Plan expansion

until it was split in 1958
Assigning a new area code requires either geographically splitting an existing numbering plan area (split plan) and reassigning the subscribers in the new, smaller area to a new area code, or assigning an additional area code to an existing numbering plan area, which is called an overlay plan.

809 scam

Caribbean or other international numberspremium calls to Caribbean or foreign numbers within the NANP
Adding to the confusion, the 809 code was split into multiple new area codes in 1997.

Rate center

rate centre
This inefficient use of numbering resources leads to shortages of available prefixes, which then prematurely require introduction of split plan or overlay plan area codes.

Area code 906

906
906 was created as a split from 616 on March 19, 1961, as a flash-cut, with no official permissive dialing.

Central office code protection

exchange code protectioncode protection
Severing the border community from its exhausted home area code using a split plan may prolong the life of a seven-digit exchange code protection scheme if the piece being split off is outside the extended local calling area.

Area code 727

727
With this in mind, GTE (now part of Frontier Communications), the dominant carrier in most of the Tampa Bay Area, switched the proposal to a split plan.

Linked numbering scheme

linked-number area
Some local calls require ten-digit dialling, either across area code boundaries in a split plan or within the same community in an overlay plan.