Why a Phone Number Pad is Laid Out Like It Is

This is a video by video journalist Brady Haran. For more great videos like this, be sure to subscribe to Brady’s great Youtube channel Numberphile.

Also, don’t forget to check out TodayIFoundOut’s YouTube channel here, which very soon will start being updated weekly as our video person switches to doing this full time instead of almost never-time. ;-)

If you liked this video, you might also enjoy:

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One comment

  • The engineering factor was most likely the dual tone multi-frequency (DTMF) technology used for creating “touch tones”. To create 10 tones you need at least 7 frequencies (6 frequencies maxes out at 3 low and 3 high for only 9 combinations). With 7 frequencies, you can get 10 tones (5×2) but the max is 12 tones (3×4). The chosen design allowed engineers to add two buttons (* and #) to allow the maximum flexibility.

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