!!! Overview
[{$pagename}] ([NDC] or [NXX]), commonly referred to as an International City Code or [Number Plan Area] or [Area Code] or significant leading digits of [National Significant Number], is specified in [ITU-T] [E.164]. 


[{$pagename}] identifies the [Number Plan Area] that is to be used.

[{$pagename}] optional code field which determined by each specific [Telephone Numbering Plan].

[{$pagename}] when combined with the [Subscriber Number] (SN) - will constitute the [National Significant Number] within the international [E.164]-number for geographic areas.

!! [{$pagename}] [North American Numbering Plan] ([NANP]) 
[North American Numbering Plan] ([NANP]) [{$pagename}] values are available.[2]

The following 555-XXXX [{$pagename}] line numbers remain in use:
* 555-1212 Directory Assistance National use
* 555-4334 Assigned National use
* 555-0100 through 555-0199 are  __fictitious non-working numbers__ reserved for entertainment/advertising.

!! More Information
There might be more information for this subject on one of the following:
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* [#1] - [Telephone_numbering_plan|Wikipedia:Telephone_numbering_plan|target='_blank'] - based on information obtained 2017-12-19- 
* [#2] - [Central Office Code Assignment Records|https://www.nationalnanpa.com/reports/reports_cocodes_assign.html|target='_blank'] - based on information obtained 2019-08-15 
* [#3] - [555 NXX Line Number Reference Document|https://www.nationalnanpa.com/pdf/NRUF/ATIS-0300115.pdf|target='_blank'] - based on information obtained 2019-08-15