![]() The word acoustic comes from the Greek akoustikos meaning hearing, as with hearing of sound waves in air. Acoustic telegraphy was similar in concept to present-day FDMA, or Frequency Division Multiple Access, used with radio frequencies. Some of Thomas Edison's devices used multiple synchronized tuning forks tuned to selected audio frequencies and which opened and closed electrical circuits at the selected audio frequencies. Their efforts to develop acoustic telegraphy, in order to reduce the cost of telegraph service, led to the invention of the telephone. Inventors who worked on the acoustic telegraph included Charles Bourseul, Thomas Edison, Elisha Gray, and Alexander Graham Bell. At the receiving end a device tuned to the same frequency resonated to the pulses but not to others on the same wire. ![]() The key pulses were transmitted as pulses of a specific audio frequency. A telegrapher used a conventional Morse key to tap out the message in Morse code. ![]() Attempt at multiplexing Morse code messages by assigning them different soundsĪcoustic telegraphy (also known as harmonic telegraphy) was a name for various methods of multiplexing (transmitting more than one) telegraph messages simultaneously over a single telegraph wire by using different audio frequencies or channels for each message. ![]()
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