Strowger switch

The Strowger switch is the first commercially successful electromechanical stepping switch telephone exchange system. It was developed by the Strowger Automatic Telephone Exchange Company founded in 1891 by Almon Brown Strowger. Because of its operational characteristics, it is also known as a step-by-step (SXS) switch. Strowger, an undertaker, was motivated to invent an automatic telephone exchange after having difficulties with his telephone service. He became convinced that the manual telephone exchange operators were deliberately interfering with his calls, leading to loss of business. According to the local Bell Telephone Company manager Herman Ritterhoff, Strowger swore to "get even" with the telephone operators and "put every last one of them out of a job." Ritterhoff claimed that the real cause of Strowger's difficulties was a metal sign hung on his wall over his telephone, causing an intermittent short circuit when blown by the wind. Strowger conceived his invention in 1888, and was awarded a patent for an automatic telephone exchange in 1891. The initial model was made from a round collar box and some straight pins. While Almon Strowger devised the initial 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 financing to realize the concept. The Strowger Automatic Telephone Exchange Company was founded in 1891. In the original design patent, four keys were added near the telephone, one each for thousands, hundreds, tens and units, with each key having an additional wire connection to the central exchange. Each key had to be tapped the correct number of times to step the switch and make the desired connection. To connect to number 1256, the user would press the first key once, the second key twice, the third key five times and the final key six times. The company installed and opened the first commercial exchange in his then-home town of La Porte, Indiana on November 3, 1892. The exchange had around 75 subscribers.