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564 is a proposed area code for the state of Washington covering all of Western Washington, including Seattle. It would be an overlay plan for area codes 206, 253, 360 and 425. As of May 2015, it has not been implemented. In 1999, area code 564 was proposed as an overlay of area code 360, which serves areas of Western Washington outside of the Seattle Tacoma metropolitan area. This version of the overlay was slated for implementation on July 29, 2000. Later, the Washington Utilities and Transportation Commission (WUTC) determined that the actual increase in need for new numbers in 360 had fallen short of projections, and postponed the overlay until at least February 2001. In May 2000, the commission projected that the metropolitan Seattle area codes (206, 253 and 425) would also soon exhaust their number pools, and expanded the 564 plan to include those areas as well. By the summer, however, this was determined to be not immediately necessary. The overlay was then planned for application on October 20, 2001. On August 22, 2001, the WUTC announced that, due to increased efficiency in the reuse of the existing number pool, the immediate need for the new area code had subsided. Part of this was also attributed to a downturn in the telecommunications sector. The commission put off implementation until no earlier than October 20, 2002. Since the development of the initial plan for the area code, the WUTC and the NANPA have rebuffed the telephone companies' request for a new area code and instead directed them to actively share and efficiently use the number blocks already assigned. This mainly refers to the practice of number pooling, which divides telephone exchange prefixes for more efficient allocation as 10 blocks of 1,000 numbers, instead of assigning a prefix's whole numbering space (10,000 numbers) to one carrier in the one rate centre. The WUTC has taken further steps to decrease the need for new number blocks in 360 and 509 and head off the need for new area codes, including aggressive reclamation of unused and underused number blocks and exchanges. The introduction of mandatory local and wireless number portability (a prerequisite for number pooling) has also served to stem the demand for new numbers and thus new area codes.〔http://www.utc.wa.gov/regulatedIndustries/utilities/telcom/Pages/areaCodes.aspx〕 According to the WUTCs estimate as of 2013, the earliest projection for any Western Washington area code to be exhausted is 2017, for area code 360.〔http://www.utc.wa.gov/regulatedIndustries/utilities/telcom/Pages/areaCodes.aspx〕 If and when area code 564 goes into effect, it will require 10-digit dialing for all local phone calls in Western Washington. Currently, local calls within a Numbering Plan Area can use 7-digit dialing. ==External links== *(WUTC delays need for new area code and 10-digit local dialing in Western Washington ) November 18, 2008 *(WUTC postpones area code 564 overlay and mandatory 10-digit dialing ) August 22, 2001 *(WUTC to consider delaying introduction of new 564 area code ) August 17, 2001 *(WUTC orders telephone companies to share prefixes in area code 360 ) *(WUTC orders additional steps to extend the life of area codes 360 and 509 ) October 23, 2002 〔 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「Area code 564」の詳細全文を読む スポンサード リンク
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