Primarily because of the rapid growth in the use of cellular phones, the number
ID: 2982633 • Letter: P
Question
Primarily because of the rapid growth in the use of cellular phones, the number of available
phone numbers had to be increased. This was accomplished by increasing the number
of available area codes in the United States. Investigate how this was done by completing
the following, remembering that an area code cannot begin with a 0 or a 1.
1. Prior to 1995, all area codes had a 0 or a 1 as the middle digit. How many area
codes were available then?
2. Consult nanpa.com to see the one number that is still not used as the middle of an
area code.
3. Assuming that all the middle-digit restrictions except the one mentioned in Question 2
were removed in 1995, how many additional area codes became available?
4. What further changes could be made to the area code (other than adding a fourth
digit) that would increase the available phone numbers? How many times more numbers
would be available?
5. After the area code, every number mentioned on television dramas has 555 as its
first three digits. How many phone numbers are available in each area code of TV
Land?
6. Find how many area codes Los Angeles has, then determine how many different
phone numbers are available in TV Land
Explanation / Answer
The area served by the NANP is divided into smaller Numbering Plan Areas (NPAs), each identified by a three-digit NPA code, commonly called an area code.
For quick information about a specific area code, use the area code search. You can also find the area code for a city or town with population greater than 20,000. The site also provides area code maps.
NANPA provides a variety of NPA Reports. These reports include identification of geographic area codes (i.e., area codes that designate specific geographic areas) and non-geographic area codes (i.e., designate specific services such as "toll-free"). In addition, there is a report that identifies those planned area codes not yet in service. It lists anticipated in-service dates if they are known. The "status" column provides additional information. A status of "suspended" indicates that the state public utility commission has suspended introduction of the new area code. A status of "pending" indicates that the new area code will be introduced "just in time" to preclude number exhaust.
NANPA also provides for download an area code database (zip) in Microsoft Access format. Use this database to generate custom queries and reports to meet your needs. Database field definitions (xls) are available. The file has been "zipped" to reduce download time.
NANPA uses NPA Allocation Plan and Assignment Guidelines prepared by the ATIS-sponsored Industry Numbering Committee to administer area codes.
More about area codes...
The format of an area code is NXX, where N is any digit 2 through 9 and X is any digit 0 through 9. Initially, the middle digit of an area code had to be "0" or "1". When this restriction was removed in 1995, additional area code combinations became available. There are 800 possible combinations associated with the NXX format. Some of these combinations, however, are not available or have been reserved for special purposes
Among them are the following:
Canada and the United States have experienced rapid growth in the number of area codes, particularly between 1990 and 2005. There are two main reasons for this. First, there is the increasing demand for telephone services (particularly resulting from widescale adoption of fax, modem, and mobile phone communications).
The second and more important reason is the telecom deregulation of local telephone service in the US beginning in the early to mid-1990s. At that time, the Federal Communications Commission began allowing telecommunication companies to compete with the incumbent local exchange carrier (usually by forcing the existing monopoly service provider to lease infrastructure to other local providers who then resold the service to consumers). However, because of the original design of the numbering plan and telephone switching network that assumed only a single provider, number allocations had to be made in 10,000-number blocks.
Thus, whenever a new local service provider entered a given market, it would be allocated 10,000 numbers by default, even if the provider only obtained a few customers. As more companies began requesting numbering allocations, this caused many area codes to begin exhausting their supply of available numbers (code "in jeopardy" in telecom jargon), and additional area codes were needed. In reality, many of the new telecom ventures were not successful; while the number of area codes started increasing rapidly, this did not necessarily translate to a much larger number of actual telephone subscribers as large blocks of numbers lay unassigned to any "real" subscribers because of the 10,000-number block allocation requirement. When these telecom ventures were merged or bought or liquidated, their blocks went to the successor or went unused. No regulatory mechanism existed to reclaim and reassign these underutilized blocks.
In general, area codes were added either as "splits" (in which an area code was divided into two or more regions, one retaining the older area code and the other area(s) receiving a new code), or "overlays", in which multiple codes are assigned to the same geographical area. Subtle variations of these techniques have been used as well, such as "dedicated overlays", in which the new overlaid code was reserved for a particular type of service, such as cellular phones and pagers (the only true example of this was area code 917 in New York City), and "concentrated overlays", in which a part of the area retained a single code while the rest of the region received an overlay code.
Area codes of the form N10, originally reserved for AT&T's Teletypewriter eXchange service, were transferred to Western Union in 1969 and were freed up other use in 1981 after conversion to Telex II service was complete. These eight "new" area codes were used for telephone area code splits in the late 1980s and early 1990s, as all other area codes under the original plan had been consumed.
After the remaining valid area codes were used up by expansion, in 1995 the rapid increase in the need for more area codes (both splits and overlays) forced NANPA to allow the digits 2 through 8 to be used as a middle digit in new area code assignments, with 9 being reserved as a "last resort" for potential future expansion. At the same time, local exchanges were allowed to use 1 or 0 as a middle digit. The first area codes without a 1 or 0 as the middle digit were area code 334 in Alabama and area code 360 in Washington, which both began service on January 15, 1995. This was quickly followed by area code 520 serving Arizona on March 19, 1995.
Codes ending in double digits are reserved as easily recognizable codes (ERCs), to be used for special purposes such as toll-free 800, 888, 877, 866 and 855, personal 700 numbers, and high-toll 900 numbers, rather than for geographic areas. (Nevada was denied 777 for this reason; it received 775 instead when most of Nevada split from 702, which continues to serve the Las Vegas metropolitan area.)
Easily Recognizable Codes When the second and third digits of an area code are the same, that code is called an easily recognizable code (ERC). ERCs designate special services; e.g., 888 for toll-free service. N11 These 8 ERCs, called service codes, are not used as area codes. N9X The 80 codes in this format, called expansion codes, have been reserved for use during the period when the current 10-digit NANP number format undergoes expansion. 37X and 96X Two blocks of 10 codes each have been set aside by the INC for unanticipated purposes where it may be important to have a full range of 10 contiguous codes available.Canada and the United States have experienced rapid growth in the number of area codes, particularly between 1990 and 2005. There are two main reasons for this. First, there is the increasing demand for telephone services (particularly resulting from widescale adoption of fax, modem, and mobile phone communications).
The second and more important reason is the telecom deregulation of local telephone service in the US beginning in the early to mid-1990s. At that time, the Federal Communications Commission began allowing telecommunication companies to compete with the incumbent local exchange carrier (usually by forcing the existing monopoly service provider to lease infrastructure to other local providers who then resold the service to consumers). However, because of the original design of the numbering plan and telephone switching network that assumed only a single provider, number allocations had to be made in 10,000-number blocks.
Thus, whenever a new local service provider entered a given market, it would be allocated 10,000 numbers by default, even if the provider only obtained a few customers. As more companies began requesting numbering allocations, this caused many area codes to begin exhausting their supply of available numbers (code "in jeopardy" in telecom jargon), and additional area codes were needed. In reality, many of the new telecom ventures were not successful; while the number of area codes started increasing rapidly, this did not necessarily translate to a much larger number of actual telephone subscribers as large blocks of numbers lay unassigned to any "real" subscribers because of the 10,000-number block allocation requirement. When these telecom ventures were merged or bought or liquidated, their blocks went to the successor or went unused. No regulatory mechanism existed to reclaim and reassign these underutilized blocks.
In general, area codes were added either as "splits" (in which an area code was divided into two or more regions, one retaining the older area code and the other area(s) receiving a new code), or "overlays", in which multiple codes are assigned to the same geographical area. Subtle variations of these techniques have been used as well, such as "dedicated overlays", in which the new overlaid code was reserved for a particular type of service, such as cellular phones and pagers (the only true example of this was area code 917 in New York City), and "concentrated overlays", in which a part of the area retained a single code while the rest of the region received an overlay code.
Area codes of the form N10, originally reserved for AT&T's Teletypewriter eXchange service, were transferred to Western Union in 1969 and were freed up other use in 1981 after conversion to Telex II service was complete. These eight "new" area codes were used for telephone area code splits in the late 1980s and early 1990s, as all other area codes under the original plan had been consumed.
After the remaining valid area codes were used up by expansion, in 1995 the rapid increase in the need for more area codes (both splits and overlays) forced NANPA to allow the digits 2 through 8 to be used as a middle digit in new area code assignments, with 9 being reserved as a "last resort" for potential future expansion. At the same time, local exchanges were allowed to use 1 or 0 as a middle digit. The first area codes without a 1 or 0 as the middle digit were area code 334 in Alabama and area code 360 in Washington, which both began service on January 15, 1995. This was quickly followed by area code 520 serving Arizona on March 19, 1995.
Codes ending in double digits are reserved as easily recognizable codes (ERCs), to be used for special purposes such as toll-free 800, 888, 877, 866 and 855, personal 700 numbers, and high-toll 900 numbers, rather than for geographic areas. (Nevada was denied 777 for this reason; it received 775 instead when most of Nevada split from 702, which continues to serve the Las Vegas metropolitan area.)
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