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The North American numbering plan expansion is a proposed expansion of the North American Numbering Plan to accommodate future needs beyond the current 10-digit limitations used in telephone numbers. ==History== The North American Numbering Plan has been in use since 1947, and has endured that time with only minor changes. So far, unlike many countries outside of North America, it has not been necessary to lengthen phone numbers to accommodate expansion. To date, the accommodation of demand has been achieved by adding area codes (NPAs) for relief (either as a split or as an overlay plan), a few isolated instances of rate centre consolidation and (in the US) number pooling which allowed the reclamation of many unused numbers. The addition of area codes has required ten digit dialing for some local calls, and dialing ''1'' before a long-distance call in order to distinguish identical number sequences in local exchange prefixes and area codes. Although the plan provides for a potential of 6.4 billion telephone numbers, a considerable percentage of these numbers will remain unused when the last available NPA code is assigned, as thousands of numbers will not be in use in exchanges that serve only a small population center, the exchange being served by a single NPA-NXX combination in non-competitive markets. More combinations would be partially unused in the event that a small market has competitive providers. As a result, as the supply of unassigned NPA codes dwindles, it will be necessary for telephone carriers in North America to implement expansion beyond the 10-digit format. Expansion has been a matter of discussion by industry forums for several years, and although a recommendation has been made, that expansion plan format has not been approved by the regulatory authorities, i.e. the Federal Communications Commission in the United States and the Canadian Radio-Television and Telecommunications Commission and the regulators may choose a different expansion plan. The industry forum considered dozens of potential options and identified the difficulties with each option. NANPA regularly performs exhaustion analyses. The 2014 analysis anticipates exhaustion after 2044.〔() April 2014 NANP Exhaust Analysis〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「North American Numbering Plan expansion」の詳細全文を読む スポンサード リンク
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