Editing 5ESS Switching System (section)

==History==
The 5ESS came to market as the Western Electric No. 5 ESS. It commenced service in [[Seneca, Illinois]] on March 25, 1982, and was destined to replace the [[Number One Electronic Switching System]] (1ESS and 1AESS) and other electromechanical systems in the 1980s and 1990s. The 5ESS was also used as a [[Class-4 telephone switch]] or as a hybrid Class 4/Class 5 switch in markets too small for the [[4ESS]]. Approximately half of all US [[telephone exchange|central offices]] are served by 5ESS switches. The 5ESS was also exported, and manufactured outside the US under license.<ref name="Ukraine_Export">{{cite news |last1=Vandewater |first1=Bob |title=Ukraine Gets AT&T Phone Switch |url=https://www.oklahoman.com/story/news/1993/02/20/ukraine-gets-att-phone-switch/62467317007/ |access-date=18 January 2024 |work=The Oklahoman |date=1993-02-20}}</ref>

The 5ESS–2000 version, introduced in the 1990s, increased the capacity of the switching module (SM), with more peripheral modules and more optical links per SM to the communications module (CM).  A follow-on version, the 5ESS–R/E, was in development during the late 1990s but did not reach market. Another version was the 5E–XC.{{citation needed|date = June 2019}}

The 5ESS technology was transferred to the AT&T Network Systems division upon the 1984 breakup of the Bell System. The division was divested by AT&T in 1996 as [[Lucent Technologies]],<ref>{{Cite web|title=History of Lucent Technologies Inc.|url=http://www.fundinguniverse.com/company-histories/lucent-technologies-inc-history/|access-date=2022-01-27|website=FundingUniverse}}</ref> and after becoming [[Alcatel-Lucent]] in 2006,<ref>{{cite web|title=Alcatel and Lucent Technologies to Merge and Form World's Leading Communication Solutions Provider|url=http://www.alcatel-lucent.com/wps/portal/NewsReleases/DetailLucent?LMSG_CABINET=Docs_and_Resource_Ctr&LMSG_CONTENT_FILE=News_Releases_LU_2006/LU_News_Article_007765.xml|url-status=dead|archive-url=https://web.archive.org/web/20081225233306/http://www.alcatel-lucent.com/wps/portal/NewsReleases/DetailLucent?LMSG_CABINET=Docs_and_Resource_Ctr&LMSG_CONTENT_FILE=News_Releases_LU_2006%2FLU_News_Article_007765.xml|archive-date=2008-12-25|publisher=Alcatel-lucent.com}}</ref> it was acquired by [[Nokia]] in 2016.<ref>{{Cite web|last=Tonner|first=Andrew|date=2016-01-06|title=Nokia and Alcatel-Lucent Finally Seal the Deal|url=https://www.fool.com/investing/general/2016/01/06/nokia-and-alcatel-lucent-finally-seal-the-deal.aspx|access-date=2022-01-27|website=The Motley Fool|language=en}}</ref>

The 5ESS switch is still in widespread use in the public switched telephone network (PSTN) in the United States and elsewhere, but they are being replaced with more modern packet switching systems. 5ESS switches in service in 2021 also included several operated by the United States Navy.<ref>{{Cite web|date=March 15, 2021|title=DEPT OF DEFENSE Issues Federal contract notice for " DG11 - REPAIR AND EXCHANGE SERVICE FOR LUCENT 5ESS "|url=http://link.gale.com/apps/doc/A655147244/STND?u=wikipedia&sid=ebsco&xid=150b1867|url-access=registration|access-date=27 January 2022|website=US Official News|via=Gale OneFile}}</ref>