!!! Overview[1]
[{$pagename}] is an [ITU-T] recommendation, titled The international public telecommunication numbering plan, that defines a numbering plan for the world-wide [Public Switched Telephone Network] ([PSTN]) and some other data networks.

[{$pagename}] defines a general format for [International Telephone Number]s. Plan-conforming [Phone Numbers] are limited to a maximum of 15 digits, excluding the [International Direct Dialling] ([IDD]).

The presentation of a [Phone Number] is usually prefixed with the plus sign (+), indicating that the [Phone Number] includes the [Number Plan Area]. When dialing, the [Phone Number] must typically be prefixed with the appropriate international call prefix (in place of the plus sign), which is a [Trunk Code] to reach an international circuit from within the country of call origination.

The title of the original version and first revision of the [{$pagename}] standard was "Numbering Plan for the [ISDN] Era".

!! [{$pagename}] [International Telephone Number] formats
[{$pagename}] Numbering formats are limited to a total of 15 [Digits] and defined into the following categories:
* Geographic Areas
* Global Services - [Global Subscriber Number]
* [Networks]
* Groups of Countries

[{$pagename}] is a number is designed to include all of the necessary information to successfully route a call to an individual subscriber on a nation's public telephone network. Here's how the E.164 numbering plan works:
* [Phone Number] can have a maximum of 15 [digits]
* [Country Calling Code] (one to three digits)
** any leading '0' is removed.
* [National Destination Code] ([NDC])
* [Subscriber Number] (SN)
* all punctuation is removed: spaces, dashes ['-'] and parentheses [[ '(' and ')' ] are removed, except the leading '+' all characters [SHOULD] be numeric.   
[National Destination Code] and [Subscriber Number] together are collectively called the [National Significant Number]

[{$pagename}] allows each [country] to decide how many digits should be in the [National Destination Code] and the [Subscriber Number]. 

The possibilities are nearly endless. A 15-digit number allows for 100 [trillion] different Numbers. (enough for each person on earth to have 10,000 phone numbers)

[{$pagename}] numbers can be mapped to a [Uniform Resource Identifier] ([URI]) the use of the [Domain Name System] ([DNS]) and the [Dynamic Delegation Discovery System] ([DDDS]) as described in [RFC 6116]

!! [Example] [{$pagename}] Number
An [Example] [{$pagename}] Number you might use as  +1 (804)-222-1111 x1234. This number would be defined as:
Parsing Result (parseAndKeepRawInput())
* [Country Calling Code]:	1
* [National Significant Number]: 8042221111
* extension: 1234
* country_code_source	FROM_NUMBER_WITH_PLUS_SIGN
* italian_leading_zero	false
* raw_input: +1 (804)-222-1111 x1234
* Phone Number region: [US]
* Number Type: FIXED_LINE_OR_MOBILE
* __[{$pagename}] format: +18042221111__
* Original format: +1 804-222-1111 x1234
* National format: (804) 222-1111
* International format: +1 804-222-1111
* Out-of-country format from US: 1 (804) 222-1111
* Out-of-country format from CH: 00 1 804-222-1111
* Phone Number Off-line [Geolocation]: Richmond, VA
* Time zone(s):	America/New_York
* Carrier:

!! [{$pagename}] [Regular expression]
[{$applicationname}] has used this [Regular expression] for testing strings as proper formatted of [{$pagename}] [Phone Numbers]:
{{{
^\+?[1-9]\d{1,14}$
}}}


!! More Information
There might be more information for this subject on one of the following:
[{ReferringPagesPlugin before='*' after='\n' }]
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* [#1] - [E.164|Wikipedia:E.164|target='_blank'] - based on data observed:2015-05-18