Editing Digital Multiplex System (section)

{{short description|Electronic telephone switch}}
{{More references|date=April 2020}}
[[Image:Nortel DMS10.jpg|thumb|right|250px|A [[DMS-10]] used as a lab trainer at [[Southeast Missouri State University]].]]
[[Image:Nortel DMS100 public voice exchange.jpg|thumb|right|250px|A [[DMS-100]] used by an operator to offer local and long distance services in [[France]].]]

'''Digital Multiplex System''' (DMS) is the name shared among several different [[telephony]] product lines from [[Nortel Networks]] for wireline and wireless operators. Among them are the DMS-1 (originally named the DMS-256<ref>{{cite web
| url=https://telephoneworld.org/telephone-switching-systems/overview-background-on-electronic-digital-switching-systems/
| title=Overview & Background on Modern Electronic & Telephone Digital Switching Systems
| publisher=Telephone World
| date=2009-04-03
| accessdate=2009-02-16}}</ref>) Rural/Urban [[digital loop carrier]], the DMS-10 telephone switch, the DMS SuperNode family of [[telephone switch]]es ([[DMS-100]], DMS-200, DMS-250, DMS-300, DMS-500, DMS-GSP, DMS-MSC, DMS-MTX), and the S/DMS optical transmission system.

Exploratory development on the technology began at Northern Telecom's [[Bell Northern Research Labs]] in [[Ottawa]], [[Ontario]] in 1971. The first [[Class 5 telephone switch|Class 5]] switch, the DMS-10, began service on 21 October 1977 in [[Fort White, Florida]] and the first [[Class 4 telephone switch|toll switch]] (Class 4), the DMS-200, entered service in 1979 in Ottawa. The DMS-10 was the first commercially successful Class 5 digital switch in the North American market and had a profound impact on the industry. Of the numerous digital switching products introduced in the North American telephone market in the late 1970s, only the Nortel DMS family is still in production.{{Citation needed|date=August 2011}} GENBAND (now [[Ribbon Communications]])<ref>{{cite web
| url=https://ribboncommunications.com/company/media-center/press-releases/sonus-networks-inc-announces-completion-sonus-and-genband-merger
| title=Ribbon Communications was formed in 2017 following the merger of Genband and Sonus Networks
| publisher=Ribbon Communications
}}</ref> acquired Nortel CVAS assets including the DMS line in 2011 and rolled it into its IP-based GENiUS platform. The GENiUS-750nt is the first product to include adaptive nano-tech compression and resynchronization modules from Ericsson, to replace the digital cross-connect (DCS) in place since the earliest DMS releases.

Previously, new technology had entered the telecommunications industry slowly, with the telephone companies [[amortization (accounting)|amortizing]] equipment over periods as long as forty years. [[AT&T Corporation|AT&T]] was intending to delay the introduction of [[Telephone exchange#Digital switches|digital switching]] until the 1990s. The DMS, with its introduction of digital technology, changed the industry and became one of the antecedents that encouraged the growth of the Internet.

On October 16, 2006, Nortel received a special recognition award from Canada's [[Telecommunications Hall of Fame]] for its role in pioneering digital communications with the Digital Multiplex System.<ref>{{cite web
| url=http://www.telecomhall.ca/tour/special-rec/2006/digital_world.htm
| title=Special Recognition Award - Digital World
| publisher=Canadian Telecommunication Hall of Fame
| accessdate=2008-10-13
| url-status=dead
| archiveurl=https://archive.today/20130115132034/http://www.telecomhall.ca/tour/special-rec/2006/digital_world.htm
| archivedate=2013-01-15
}}</ref>

The DMS name arose from a designation for a switching matrix design that was developed in the exploratory phase of the project. The Digital Multiplexed Switch was selected as the basic switching design for the project. The product was intended as a successor for Nortel's first electronic switch, the [[SP1 (telecommunications)|SP1]], and was to be called the SP2. However the DMS acronym was mellifluous and was eventually (1975) adopted as the designation for the DMS-10 and DMS-100 family of products, with the "S" standing for "system" rather than "switch". It was then applied to the entire digital switching family as well as the DMS-1 family of Digital Transmission Concentrators.

DMS is favoured by many European [[Cable telephony|cable]] operators as the switching platform for their voice networks. The DMS-10 is widely used by rural wireline providers. DMS-100 and 200 switches are widely deployed throughout the U.S. and Canada by [[RBOC|Regional Bell Operating Companies]], [[Bell Canada]] and [[independent telephone companies]] as well as the [[autovon|US Military]]. The DMS-250 is the backbone of a number of carriers' long-distance networks. The DMS-300 is an international gateway switch, and the DMS-500 is commonly deployed by [[competitive local exchange carrier]]s because it combines DMS-100 and 250 capabilities.

DMS switches run a proprietary multitasking operating system known as SOS.
<ref>{{cite book 
|editor1-first=A. 
|editor1-last=Danko 
|title="DMS Programming Model" 
|publisher=Nortel Networks (proprietery internal textbook)}}</ref> 
The user interface, called MAPCI, consists of a series of multi-level menus and is usually accessed from a connected VT100 compatible dumb terminal or terminal emulator. Each level or overlay performs different functions.

A working DMS 10 can be viewed at the [[Connections Museum]] in Seattle.