Digital Multiplex System
Encyclopedia
- Not to be confused with DMX512.
Digital Multiplex System (DMS) is the name shared among several different telephony
Telephony
In telecommunications, telephony encompasses the general use of equipment to provide communication over distances, specifically by connecting telephones to each other....
product lines from Nortel Networks for wireline and wireless operators. Among them are the DMS-1 (originally named the DMS-256) Rural/Urban digital loop carrier
Digital loop carrier
A digital loop carrier is a system which uses digital transmission to extend the range of the local loop farther than would be possible using only twisted pair copper wires...
, DMS-10 telephone switch, the DMS SuperNode family of telephone switches (DMS-100
DMS-100
The DMS-100 Switch is a line of Digital Multiplex System telephone exchange switches manufactured by Nortel Networks.The purpose of the DMS-100 Switch is to provide local service and connections to the PSTN public telephone network. It is designed to deliver services over subscribers' telephone...
, 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 (Ottawa, Canada) in 1971. The first Class 5 switch, the DMS-10, began service on 21 October 1977 in Fort White, Florida
Fort White, Florida
Fort White is a town in Columbia County, Florida, United States named after a military fort built in the 1830s. It is the closest town to the Ichetucknee Springs State Park. The Fort White Public School Historic District is located within the town's borders. As of 2010, the population recorded by...
and the first toll switch
Class 4 telephone switch
A Class 4, or Tandem, telephone switch is a U.S. telephone company central office telephone exchange used to interconnect local exchange carrier offices for long distance communications in the Public Switched Telephone Network....
, the DMS-200, entered service in 1979 in Ottawa, Canada. 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.
Previously, new technology had entered the telecommunications industry slowly, with the telephone companies amortizing
Amortization
Amortization is the process of decreasing, or accounting for, an amount over a period. The word comes from Middle English amortisen to kill, alienate in mortmain, from Anglo-French amorteser, alteration of amortir, from Vulgar Latin admortire to kill, from Latin ad- + mort-, mors death.When used...
equipment over periods as long as forty years. AT&T
AT&T
AT&T Inc. is an American multinational telecommunications corporation headquartered in Whitacre Tower, Dallas, Texas, United States. It is the largest provider of mobile telephony and fixed telephony in the United States, and is also a provider of broadband and subscription television services...
was intending to delay the introduction of 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
Telecommunications Hall of Fame
Canada's Telecommunications Hall of Fame is a Canadian not-for-profit foundation that seeks to foster a greater awareness of Canada's role in developing and innovating telecommunications...
for its role in pioneering digital communications with the Digital Multiplex System.
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 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
Cable telephony
Cable telephony is a form of digital telephony over cable TV networks. A telephone interface installed at the customer's premises converts analog signals from the customer's in-home wiring to a digital signal, which is then sent over the cable connection to the company's switching center. The...
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 Regional Bell Operating Companies, Bell Canada
Bell Canada
Bell Canada is a major Canadian telecommunications company. Including its subsidiaries such as Bell Aliant, Northwestel, Télébec, and NorthernTel, it is the incumbent local exchange carrier for telephone and DSL Internet services in most of Canada east of Manitoba and in the northern territories,...
and independent telephone companies as well as the US Military
Autovon
AUTOVON, short for Automatic Voice Network, was an American military phone system built in 1963 to survive nuclear attacks. AUTOVON was first established in the United States, using the Army's SCAN system. Around the mid-1970s AUTOVON expanded to the United Kingdom, Asia, the Middle East, and Panama...
. 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 carriers because it combines DMS-100 and 250 capabilities.
DMS switches run a proprietary multitasking operating system which consists of a series of multi-level menus called 'MAPCI' and subprograms known as 'Overlays' and usually accessed from a connected VT100 compatible dumb terminal or terminal emulator. Each overlay performs different functions. For example, the alarm overlay (invoked by typing OVLY ALO on a terminal connected to a DMS-10) allows you to enter commands to display and clear alarms. Similarly, OVLY LIT permits running metallic Line Isolation Testing on cable pairs to determine line resistance, voltage, capacitance, etc... DMS switches are also capable of running a specialized version of UNIX.