In this next part in our series on the history of the telephone, we're going to pick up with the construction of the first regular telephone line.

After Bell's completion of the telephone in 1876 the next step was making it so that this invention could be used by everybody. So in 1877, construction of the first regular telephone line, which ran from Boston to Somerville, Massachusetts, was finished. By the end of 1880 there were over 47,900 telephones in the United States and in 1881 a telephone service from Boston to Providence was set up. Then in 1892, they started a service between New York and Chicago. Two years later, in 1894, a service began between New York and Boston but it wasn't until 1915 that transcontinental service by overhead wire was created. Backtracking a bit, the first switchboard, what we now call 411 service, was set up in Boston in 1877. Then on January 17, 1882, Leroy Firman got his first patent for a telephone switchboard.

The first telephone exchange was set up in New Haven in 1878. The first telephones were leased to people in pairs. Each person was required to put up his own line in order to connect with another. Finally, in 1889, a Kansas City undertaker by the name of Almon B. Strowger invented a switch that could connect one line to any one of 100 lines using a series of relays and sliders. This switch came to be known as the Strowger Switch and it was still being used by telephone offices over 100 years later. Strowger was given a patent in 1891 for his first automatic telephone exchange.

The very first exchange that used the Strowger Switch was set up in La Porte, Indiana in 1892. At first, subscribers to the service had a button on their telephone that produced the required number of pulses by tapping on it. It wasn't until 1896 that one of Strowger's assistants invented the rotary dial. This ultimately replaced the button and is still in use on telephones today, mostly for novelty purposes. In 1943, Philadelphia was the last city to give up dual service for both button and pulse dialling.

The first touch tone system, which used tones in the voice frequency range instead of pulses used by rotary dials, was installed in Baltimore, Maryland in 1941. Operators in a central switching office pushed the buttons to make this work. The problem was, it was just too expensive for general use by the public, but the Bell Telephone Company, named after the man credited with the invention of the phone, was still interested in the touch tone system because it increased the speed of dialling.

The answer to this problem came in the 1960s when low cost transistors and circuit components made the cost effective use of touch tone telephones in a person's home a real possibility. Through much testing, positioning of the buttons limited errors and increased dialling speed even more. The touch tone phone got its big preview at the 1962 Seattle World's Fair, where it was a huge success.