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Amusing Concepts in Telephone Switching


Keith's Strowger version (A. Keith 1899 patent), Rotary, Panel, Ericsson 500-point selector, and Crossbar switches were massive successes compared to the countless switching inventions that went nowhere.


In 1879, three years after Alexander Graham Bell's invention, the first patent was filed relating to automated switching and apparatus – US 222,458 patent by the Connolly brothers and McTighe.


The crude switching mechanism was not successful but was the beginning of a long line of research and invention. From then until 1929, about 2,500 US patents were issued related to automated switching.


As an example of a whimsical switch, Moise Freudenberg invented such a mechanism, US patent number 556,007, March 1896. The general features are illustrated in the figure below (from the patent). It utilized some of the principles of a railway system. The switch was controlled by the subscriber but not using a dial (not invented yet). It was a rudimentary XY cross-point switch with a crude semblance to a crossbar switch but with stationary bars.  




For a deeper look at the train car concept, and other unusual switches, see the article “Curious Patents in Mechanical Switching” from March 1929 issue of Bell Laboratories Record, page 267.

See also US511874A (1894) patent by R. Callender. This was the first "ball-based" switch. Some inventors were seemingly drawn to using balls to create a switching action in the early days. This gives us a hint at how difficult the switching problem was that inventors resorted to routing rolling balls to switch a call.  

telephone switch mechanism by Moise Freudenberg 1896 , Moise Freudenberg
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