ANSWERS: 2
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1962 The first commercial touch-tone phones were a big hit in their preview at Seattle World's Fair.
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4-1-2017 DTMF, Dual Tone Multi Frequency, was invented by Nikola Tesla to demonstrate a radio controlled boat in 1895. The system was applied to the telephone system slowly, from the 60s to the 80s. (Because the phone company insisted on charging extra for touch-tone.)
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