The touch tone telephone was invented to replace the rotary phone. The rotary, or "pulse" phone, invented by Almon B. Strowger, replaced the older system of "dual service", under which each phone connected to only one other phone, over a private line. A rotary dial consists of a wheel with the numbers zero through nine. When dialing, the user spins the wheel until the number he desires is pressed against the stop pin. By releasing the wheel at this point, it strikes a ratchet X times, where X is the digit that was chosen. This is repeated for each digit in the phone number.

However, rotary phones were tough on weak fingers and took a long time to dial. Hence, the touch tone phone. The touch tone was invented in 1941 in Baltimore, Maryland, where it was used in a central switching office to save time. It was not until 1962, when transistors became cheap and plentiful, that the touch tone was available for mass usage. It was introduced at the 1962 World's Fair, and soon spread across the globe.

The * and # (pound) keys did not appear on the original touch tone phone, but were added at a later point in time.

A touch tone phone orients the numbers in rows, rather than in a circle. Each time a number is pressed, the phone produces two separate tones, which combine to form the sound that you here. The tones for each digit are as follows:

  • 1: 697 Hz and 1209 Hz
  • 2: 697 Hz and 1336 Hz
  • 3: 697 Hz and 1477 Hz
  • 4: 770 Hz and 1209 Hz
  • 5: 770 Hz and 1336 Hz
  • 6: 770 Hz and 1336 Hz
  • 7: 852 Hz and 1209 Hz
  • 8: 852 Hz and 1336 Hz
  • 9: 852 Hz and 1477 Hz
  • *: 941 Hz and 1209 Hz
  • 0: 941 Hz and 1336 Hz
  • #: 941 Hz and 1477 Hz

Most modern touch tone phones have an option which allows them to operate as a rotary phone would, producing a series of clicks instead of tones. Most major phone companies still support the rotary dial.

On a less relevant note, department stores such as Target are taking advantage of rotary phone nostalgia; they recently produced a touch-tone phone which looks like a rotary phone; in other words, the numbers are on a wheel, but they are buttons and the wheel does not turn.


This needed to be noded before it was erased from the non-Twilight Zone-watching human consciousness.

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