The Siemens DCO (digital central office) electronic telephone switch was introduced in 1977 by

Stromberg-Carlson Stromberg-Carlson was a telecommunications equipment and electronics manufacturing company in the United States. It was formed in 1894 as a partnership by Swedish immigrants Alfred Stromberg (1861 Varnhem, Sweden - 1913 Chicago) and Androv Ca ...

, having been conceived by its new president, Leonard A. Muller, an ex IBM senior executive who infused Stromberg with his new digital awareness learned in IBM. In a revolutionary project headed by lead engineer and chief of project development, Mick Richmond, the Stromberg-Carlson DCO was the one of the first digital

class 5 telephone switch {{No footnotes, date=August 2008 A class-5 telephone switch is a telephone exchange in the public switched telephone network (PSTN) that directly serves subscribers and manages subscriber calling features. Class-5 services include basic dial-tone, ...

es ever installed in the World's telecommunications network, Muller was quick to recognize the value digital technology brought to the science of electronic switching and commenced a major digital development program shortly after taking over management of Stromberg in 1974. Stromberg-Carlson put their switch into service in July 1977 in a

telephone exchange A telephone exchange, telephone switch, or central office is a telecommunications system used in the public switched telephone network (PSTN) or in large enterprises. It interconnects telephone subscriber lines or virtual circuits of digital syst ...

Richmond Hill, Georgia Richmond Hill is a city in Bryan County, Georgia. The population was 16,633 at the 2020 U.S. Census, an increase of almost 80% from the 2010 population of 9,281. Richmond Hill is part of the Savannah Metropolitan Statistical Area. History Rich ...

. The DCO came as DCO-SE (Digital Central Office - Small Exchange) for line side Central Office operation and the DCO-CS (DCO-Carrier Switch) for

Long Distance carrier An interexchange carrier (IXC), in U.S. legal and regulatory terminology, is a type of telecommunication Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagn ...

services. A few DCO's were created for the

cellular phone A mobile phone, cellular phone, cell phone, cellphone, handphone, hand phone or pocket phone, sometimes shortened to simply mobile, cell, or just phone, is a portable telephone that can make and receive calls over a radio frequency link whil ...

networks, but this was very limited. In 1990 Siemens purchased Stromberg Carlson and moved its

EWSD The Elektronisches Wählsystem Digital (EWSD), translated to ''Electronic Digital Switching System'' in English, is a widely installed German telephone exchange system, originally introduced in 1975 by Siemens AG, but discontinued in 2017. EWSD ...

production to the Lake Mary,

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

production facility in 1991. In the next few years Siemens slowly phased out the DCO as a line side central office switch. The DCO-CS was continued through the 1990s to support regional LD companies. The DCO-CS was small on port capacity (just under 10,000), but was robust on features, more than most other carrier switches. As the 1990s came to a close, many regional long distance companies were being bought up, or going out of business as their profitability had diminished. This also brought an end to DCO production as Siemens-Stromberg Carlson focused on marketing the

. In 2006 the entire Siemens DCO line was sold to

Genband Ribbon Communications US LLC is a public company that makes software, IP and optical networking solutions for service providers, enterprises and critical infrastructure sectors. The company was formed in 2017, following the merger of Genband and S ...

, originally a VoIP gateway / softswitch company from Texas, USA.

References

External links

Siemens DCO Homepage
{{Telephone Switches Telephone exchange equipment Siemens products