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Stromberg-Carlson was a telecommunications equipment and electronics manufacturing company in the United States. It was formed in 1894 as a partnership by Alfred Stromberg and Androv Carlson. It was one of five companies that controlled the national supply of telephone equipment until after World War II.[1]


In 1894, Alexander Graham Bell's patent for the telephone expired. Stromberg and Carlson, Chicago employees of the American Bell Telephone Company (later AT&T), each invested $500 to establish a firm to manufacture equipment, primarily subscriber sets, for sale to independent telephone companies.

Stromberg-Carlson was originally located in Chicago, with Carlson managing manufacturing and Stromberg responsible for marketing. Stromberg-Carlson quickly established a reputation for reliable equipment and stable prices.

In 1901, the temporary chief executive of the Kellogg Switchboard & Supply Company, Wallace De Wolf, assisted executives of rival telephone equipment manufacturer Western Electric in an attempt to take over Stromberg-Carlson. A bitter stockholder fight ensued, and the takeover attempt failed. Stromberg-Carlson reincorporated as a New York state corporation in 1902, where state law better protected the company from takeover efforts.[1][2]

1905 Stromberg-Carlson ad

In 1904, Stromberg-Carlson was purchased by Home Telephone Company, a relatively large service provider based in Rochester, New York. The new owners quickly relocated all Stromberg-Carlson operations to New York, mainly to the Rochester area. The company branched out to become a major manufacture of consumer electronics including home telephones, radio receivers and, after World War II, television sets. The company also became involved in the broadcasting industry, acquiring WHAM, the oldest station in Rochester, and rebuilding it into a high power station; one of the first three FM broadcasting stations in the United States and possibly the oldest still in operation, now known as WBZA, dating from 1939; and one of upstate New York's pioneer television broadcasters, now known as WROC-TV. In 1955, Stromberg-Carlson was purchased by General Dynamics. Within a year, all three of its broadcasting stations had been sold to different buyers.

In 1970, Stromberg delivered the first CrossReed PBX to the newly constructed Disney World in Orlando Florida. Over the next 10 years more than 7,000 CrossReeds were delivered globally.

During the 1970s, Stromberg developed what is arguably the first fully digital PBX, the DBX. The first DBX was installed at Export, Pennsylvania in 1977 and consisted of 960 ports. While this first field trial had limited success, Stromberg went on to develop the DBX-240, DBX-1200 and the DBX-5000. Also during this same period, Stromberg developed a number of leading edge technologies and products, including the first digital AUTOVON switching system and the first digital Command and Control communications system.

By 1980 General Dynamics was undergoing a significant change and in 1982, General Dynamics sold the Stromberg-Carlson operations in several parts. The Stromberg key-systems was sold to ComDial, the PBX/DBX division was sold to United Technologies and the Central Office division was sold to Plessey of the UK. Plessey eventually sold "Stromberg Carlson," the DCO business unit, to Siemens AG in 1991.

The new company, Siemens Stromberg-Carlson, became the third largest vendor of central office switches in the United States—with a combined installed base of 5 million access lines. They continued to manufacture the Siemens DCO as well as the Siemens EWSD out of the Lake Mary facility, moving production of the EWSD from New York to Florida.

In 2006 the DCO line of Siemens Stromberg-Carlson was sold to GENBAND, a Next Generation Networking company based in Texas.[3]


Switching systems[edit]

Stromberg-Carlson produced several unique switching systems, including:

  • XY, a "flat motion" switch logically similar to Strowger switching. The "XY Selector" was not invented by SC, but licensed from L.M. Ericsson of Sweden in the late 40's and re-engineered for U.S. switching applications (Ericsson used it for PABX and a very small Rural Exchange application). XY was very popular with REA (RURAL ELECTRIFICATION ADMINISTRATION) funded independent telephone companies and out sold all other vendors in the less than 1000 line applications in the 50's. The largest XY ever in service was installed in Anchorage, AK by RCA Corporation for the U.S. Air Force. Later purchased by Anchorage Telephone Co, it eventually grew to over 10,000 lines.
  • CrossReed 400/800/1600, an electronically controlled, wired-logic PBX with expansion up to 2,400 ports; notable for its quick dial tone speed & first video telephone in the world.
  • ESC, an early electronic, wired logic, reed-switch with a matrix similar to the AE EAX. The ESC, was not however Stored Program Control and had more in common with crossbar switching than other SPC electronic switching systems. It was however notable for its quick dialtone speed. (ESC-1, ESC-2, ESC-3 and ESC-4)
  • DBX-288/1344/5136 & Excalibur, the first fully digital PBX. Used a LSI/PDP-11 microprocessor in the early models and grew up to over 32,000 ports & 128,000 directories in the Excalibur.
  • DCO (Digital Central Office), a time-division switch similar to DMS-10. The Stromberg-Carlson DCO was the first Class-5 digital local office switching system installed in the U.S. Stromberg-Carlson put their switch (lab-prototype)into service in July 1977 in Richmond Hill, Georgia. This switch was SC's "REA FIELD TRIAL" office, but was never accepted by the telephone company (Coastal Utilities Inc) and was replaced with a Northern Telecom DMS-10 in the early 80's.

Military, institutional and consumer electronics[edit]

In addition to telephone equipment Stromberg-Carlson produced military communications gear, institutional sound systems, and high-end stereophonic equipment. Many included Stromberg Carlsons "Acoustic Labyrinth" loudspeaker enclosure design, a forerunner of the modern transmission line loudspeaker enclosures.

Stromberg-Carlson also produced in the early 1960s the SC4020, a computer-controlled film recorder used chiefly for COM (Computer Output Microfilm) applications. The SC4020 could output graphics and text either to 16mm microfilm or hardcopy (using chemically-developed light-sensitive paper) utilizing a Charactron CRT as the heart of the recorder (with the microfilm camera pointed directly at the face of the Charactron inside a light-proof column inside the 4020). Some 4020s were fitted with a 16mm motion picture camera instead of the stock microfilm camera, in order to create some of the first computer-generated animation. This was first accomplished by Bell Telephone Laboratories in the early to mid-1960s, where a 4020 was interfaced to an IBM 7094 computer, running a language for motion graphics generation called BEFLIX. Several films were created with BEFLIX on the 4020 at Bell Labs, the first being a film simulating the orbit of a satellite around planet Earth produced in 1963 by Bell Labs scientist Edward E. Zajac. Other Bell Labs personnel at the time such as Ken Knowlton (who developed the BEFLIX language) and Lillian Schwartz also used the recorder and its corresponding computer to make their own computer-animated film experiments. The 4020 also played a role in creating some of the imagery used in the 1965-69 experimental film Cibernetik 5.3, produced by John Stehura.

Among Stromberg-Carlson's ventures were:

  • Radio and television receivers, loudspeakers, paging systems, commercial sound amplifiers, and microphones
  • The ubiquitous BC-348 HF radio, manufactured during World War II and for a decade after
  • Institutional intercom and public address systems
  • Ground-Air-Ground tactical communications, AUTOVON and secure systems used by various government agencies worldwide

Non U.S. branding[edit]

In Argentina, the brand was acquired by Gularo S.A., a manufacturer of MP3 players, DVDs, phones, GPS, MP4s, televisions and speakers.


  1. ^ a b Cohen, The Racketeer's Progress: Chicago and the Struggle for the Modern American Economy, 1900-1940, 2004.
  2. ^ Adams, and Butler, Manufacturing the Future: A History of Western Electric, 1999; "Kellogg Switchboard & Supply Co.," Dictionary of Leading Chicago Businesses (1820-2000), 2005.
  3. ^ Paula Bernier (2006-10-04). "GENBAND Acquires Technologies, DCO Product Line From Siemens Networks". 

Further reading[edit]

  • Adams, Stephen B. and Butler, Orville R. Manufacturing the Future: A History of Western Electric. New York: Cambridge University Press, 1999. ISBN 0-521-65118-2
  • Cohen, Andrew Wender. The Racketeer's Progress: Chicago and the Struggle for the Modern American Economy, 1900-1940. New York: Cambridge University Press, 2004. ISBN 0-521-83466-X
  • "Kellogg Switchboard & Supply Co." Dictionary of Leading Chicago Businesses (1820-2000). Chicago: Chicago Historical Society, 2005.
  • 100 Years of Telephone Switching (1878-1978: Part 1: Manual and Electromechanical Switching) (Pt. 1) by Robert J. Chapuis and Amos E. Joel

External links[edit]