IBM 1750, 2750 and 3750 Switching Systems

In 1969 IBM started marketing in five European countries the IBM 2750 Switching System – worldwide, the first stored-program-controlled PABX (Private Automatic Branch Exchange). Previously onlyelectromechanical Strowger and Crossbar PABXs were available.

The 2750 was sold in France, Germany, Italy, and Belgium. The other systems were sold in these countries and the United Kingdom. The Netherlands installed some in IBM sites.

The family of IBM 1750, 2750 and 3750 Switching Systems was developed from the IBM 1800 by the IBM La Gaude Research Laboratory near Nice, France for European markets only. Each system included twin stored-program controllers (each with some 600,000 lines of code, and nightly automatic switchover), twin disks, and solid-state switching. Extension, trunk and tie lines were connected by discrete transistors on plug-in panels.

SystemYear first marketedExtensionsTrunks + tie linesOperator desks
IBM 2750 Switching System1968100-500?
IBM 3750 Switching System1970250-2200?300 Max?
IBM 1750 Switching System1979100 - 7600 - 961 - 5

The systems all had both voice and data functions – the marketplace largely bought them for their then-new voice and management functions. Early-1960s computers had hardly any typewriter-like terminals and no screens – the IBM Switching Systems introduced the novelty of simple data capture from touch-tone telephones.


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