Northern Telecom/Nortel Digital Central Office Switches


Information and pictures on modern Nortel (Northern Telecom / Northern Electric) electronic and digital central office switching systems.

Northern Telecom (formerly Northern Electric, later Nortel) originally licensed telephone switch technology from Western Electric in the United States. In the 1960s, Northern Telecom decides to strike out on their own to design and build their own line of telephone switching equipment. The successor company Nortel went bankrupt in 2013.

Early Developments: SP1, SG-1 & SL-1

In the late 1960s, Northern Electric developed their own version of an electronically controlled analog telephone switch, similar to the Western Electric #1ESS. This switch, developed in 1969 was the SP1 (Stored Program 1) switch which used mini crossbar switches with electronic stored program control. Sub-varieites of this switch included the SP-1 2-Wire (local end office) and SP1 4-Wire (toll tandem). An update to this switch was the SP1E which used the NT40 processor.

Northern Electric and Bell Canada merged their research & development activities into Bell Northern Research (BNR) in 1971. By late 1972, Northern Telecom had its first electronically controlled analog switch on the market, the SG-1 (also known as the PULSE PBX or Private Branch eXchange). Within three years, some 6,000 had been sold. In 1975, Northern Telecom developed the SL-1, the first fully digital PBX system for businesses.

DMS Local End Offices

Becoming Northern Telecom in 1976, BNR continues its development of their groundbreaking work on a fully digital local central office. In 1977, Northern Telecom releases their first of their infamoux DMS (Digital Multiplex Switch) line of switching equipment with the DMS-10 digital central office switch for small communities. Though the DMS-10 was not the first developed and demonstrated digital central office switch, it was the first production local central office (Class 5) digital switch installed in the public switched telephone network.

Nortel DMS-10 switch (Photo: Telcordia)

In 1979, Northern Telecom develops the DMS-100, a full-featured local end office digital switch to serve medium & large communities, supporting up to 100,000 lines.

Nortel DMS-100 switch (Photo: Telcordia)

There are a number of sub-varieties and remote switching modules for the DMS series of local central office switch. See the List of Nortel Electronic & Digital Switches below for more details.

DMS Tandem Offices

The DMS line of digital switches also includes various tandem switches for various features. See the List of Nortel Electronic & Digital Switches below for more details.

List of Nortel Electronic & Digital Switches

The following is a list of Nortel’s electronic & digital switches. Note: this list does not include their new line of packet switching systems.

Early Electronic Switches

  • NE-1ESS (Licensed version of Western Electric #1ESS) (mid-1960s)
  • SP1 (Electronic Stored Program Control using mini-bar switches) (1969)
  • SP1 2-Wire (Local)
  • SP1 4-Wire (Toll)
  • SP1E (used NT40 processor)
  • SG-1 (Electronic PBX) (1972)
  • SL-1 (Digital PBX) (1975)

DMS-10 Local End Office Switches

  • DMS-10 (Small local digital) (1977)
  • DMS-10S (super small DMS-10 for very small exchanges <640 lines)
  • DMS-10M (prepackaged DMS-10, a CDO in a “box”)

DMS-100 Local End Office Switches

  • DMS-100 (Large Local Digital) (1979)
  • DMS Remote Switching Modules
  • RLCM (640 line remote)
  • RSLE (520 line remote)
  • RSLM (640 line remote)

DMS Tandems

  • DMS-200 (Digital medium capacity long-haul toll digital)
    (often combined with a DMS-100 – DMS-100/200)
  • DMS-250 (Digital long-haul toll)
  • DMS-300 (Digital international Gateway Switch)
  • DMS-500 (Combined DMS-100/200/250)

Cellular Switches

  • DMS-MTX (Cellular MTSO)

Though the DMS family of “Supernode” switches are no longer being manufactured, they are still in widespread use throughout Canada, the United States and in many countries throughout the world.

More Details

Nortel History (Wikipedia)
Wikipedia List of Telephone Switches

Modern Telephone Switching Systems Index

Overview & Background of Modern (Electronic & Digital Switching) Systems
Automatic Electric Modern Switching Systems
Northern Telecom (Nortel) Modern Switching Systems
TRW-Vidar Switching Systems
Other Modern Switching Systems of Note
Western Electric/Lucent Technologies
Packet Switching/Softswitches

Telephone Switching Systems of North America

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