Strowger Switch - Further Development

Further Development

Later systems cascaded Strowger switch stages, enabling connection among many more subscribers. Rather than dedicating a single, expensive, first-stage switch to each subscriber, provision was made to connect the subscriber to any available first-stage switch. This was done either by the use of linefinders in the case of low-calling-rate domestic subscribers, or by the use of subscribers' uniselectors in the case of either commercial subscribers or, later, for any subscriber connected to a director exchange. Another enhancement was the inclusion of circuits to detect busy connections and return a busy signal to the calling subscriber.

It is this fundamental modularity of the system combined with its step-by-step (hence the alternative name) selection process and an almost unlimited potential for expansion that gives the Strowger system its technical advantage: Previous systems had all been designed for a fixed number of subscribers to be switched directly to each other in a mesh arrangement. This became quadratically more complex as each new customer was added, as each new customer needed a switch to connect to every other customer. In modern terminology, the previous systems were simply not "scalable".

While Almon Strowger may have devised the concept, he was not alone in his endeavors and sought the assistance of his brother Arnold, nephew William and others with a knowledge of electricity and money to realize his concepts. With this help the Strowger Automatic Telephone Exchange Company was formed and it installed and opened the first commercial exchange in his then-home town of La Porte, Indiana on November 3, 1892, with about 75 subscribers and capacity for 99.

He married Susan A. (1846–1921) from Massachusetts in 1897 as his second wife. The patents were exclusively licensed to Automatic Electric Company, another company Strowger helped found. Strowger sold his patents in 1896 for US$1,800 and sold his share in Automatic Electric for US$10,000 in 1898. His patents subsequently sold for US$2.5 million in 1916.

The company's engineers continued development of Strowger's designs and submitted several patents in the names of its employees. It also underwent several name changes. Strowger himself seems to have not taken part in this further development. He subsequently moved to St. Petersburg, Florida and appears to have returned to being an undertaker, as H. P. Bussey Funeral Home records report an unidentified body being moved "for Mr. Strowger" in December 1899. The same funeral home subsequently buried Strowger himself.

Strowger was a man of some wealth at his death and was reported as owning at least a city block of property.