| Date | Text | |
|---|---|---|
17 Jan 1882
Telephone switchboard |
Telephone switchboard In 1882, a telephone switchboard was issued a U.S. patent to Leroy Firman of Chicago, Illinois (No. 252,576), which was assigned to the Western Electric Manufacturing Co. also of Chicago. With his invention of a “multiple switchboard for telephone exchanges,” Firman addressed the problem of increasing numbers of subscribers. Previously, single switchboards, each with an attendant, served their group of individual lines. A large exchange was thus divided up into a number of internal exchange switchboards which were worked together as necessary, with trunk lines between the boards. Firman devised an arrangement to handle an exchange of a thousand or more subscribers with line status information exchanged between switchmen. |
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17 Jan 1882
Edison patent |
Edison patent In 1882, Thomas A. Edison was issued a patent for an improvement to the telephone (No. 252,442). It described a carbon microphone. Finely divided conducting material, such as carbon, between metal cups mounted on arms is attached to the mouthpiece diaphragm. As sound waves directed through the mouthpiece move the diaphragm, the arms change the pressure on the carbon button which in turn varies an electric current passing through the carbon button. Changes in the current correspond to the pitch and amplitude of the sound. One arm conducts the electrical current to the carbon button, and the the other from it. |
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