Just Don't Call it A Dictaphone
Edison and the manufacturer of the Graphophone dictation machines nearly went out of business in the 1890s, but gradually the dictation machine market gained momentum. Technical improvements came at a steady pace.
Dictation's most prominent promoter was Edison himself, who kept one at his desk.
By about 1910, the Thomas A. Edison Company (the name of the firm that made dictation equipment changed several times over the years) and the Columbia Phonograph Company split the U.S. market. About this time they began promoting their brand names; Columbia began to advertise its Dictaphone, while Edison countered with the Ediphone. "Dictaphone" would become the generic term for dictation equipment, to the chagrin of the Edison interests.
Dictaphones and Ediphones of the period from the 1920s through the 1940s were in a constant state of technical refinement.
Ediphone secretarial model
Electric motors, which had been tried and mostly abandoned in the 1880s, replaced clockwork motors following the widespread adoption of electric power in businesses after 1900. Mechanical details were changed to improve starting and stopping; this was especially important for the secretarial models, which were operated with foot pedals for transcription purposes.
But other features remained remarkably constant. Neither company attempted to change the basic recording medium, which was a "wax" (actually a synthetic product) cylinder long after both Edison and Columbia had shifted to discs for entertainment recordings. Electronics and microphones, both well-advanced by the 1920s, were not used at all in dictation until the late 1930s, and even then the "acoustic" models were still in use for many years. But the coming of World War II would see rapid change.