The Dawn of the Invention of the Telephone and Phonograph: Edison’s Formula for the Creation of Sound in the Acoustic Telegraph

Alexander Graham Bell made use of Edison’s work on the telephone; until the digital age, Edison’s invention was an integral part of telephone technology

Among the most important artifacts to ever reach the market from Edison’s early laboratory, 4 years before the invention of the light bulb

Thomas Edison played an instrumental role in the development of the telephone. In fact, until the system went digital, it was operating on a general principle that was first...

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The Dawn of the Invention of the Telephone and Phonograph: Edison’s Formula for the Creation of Sound in the Acoustic Telegraph

Alexander Graham Bell made use of Edison’s work on the telephone; until the digital age, Edison’s invention was an integral part of telephone technology

Among the most important artifacts to ever reach the market from Edison’s early laboratory, 4 years before the invention of the light bulb

Thomas Edison played an instrumental role in the development of the telephone. In fact, until the system went digital, it was operating on a general principle that was first discovered by Edison, that varying frequencies could produce sounds that were then sent out over one wire.

Edison had been working on methods for sending two messages simultaneously over a single wire for many years. In 1872, after Western Union adopted Joseph Stearns’s duplex for sending two messages in opposite directions, company president William Orton hired Edison to invent and patent other methods “as an insurance against other parties using them.” While working on duplex telegraphs, Edison realized that he could send four messages simultaneously by combining the duplex with a diplex for sending two messages in the same direction.

In 1875, with a contract from Western Union, Edison began work on the acoustic telegraph, which used tuning forks to send telegraphic messages at different frequencies at the same time. He would use this money to build Menlo Park. From this work on acoustic telegraphy, which he pursued at the same time as Alexander Graham Bell, came the telephone, which relied on Edison’s research, and the phonograph, which was inspired by the potential to replicate the sounds of acoustic telegraphy. It was Edison’s Carbon Microphone in the receiver that was licensed by Bell and remained in telephones for more than a century.

Charles Batchelor and John Kruesi were Edison’s chief lab assistants at this time. Batchelor was charged with coming up with the calculations to create the sound in the acoustic telegraph. Kruesi, a mechanic by trade, was in charge of putting them into effect.

Document in the hand of Charles Batchelor, 1875, Edison’s original formula for the variance of the sound in the acoustic telegraph, given to Kruesi for the experiments. This is the dawn of the invention of the telephone and led to the development of the phonograph, steps on the long path the smart phone. It is also a piece of the inventive process from Edison’s early, pre-Menlo lab.

This document was acquired by us from the direct descendant of John Kruesi and has never before been offered for sale.

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