source file: m1381.txt
Date: Fri, 10 Apr 1998 20:48:41 -0500 (CDT)

Subject: Re: Telephone Touch Tones

From: mr88cet@texas.net (Gary Morrison)

>Note that the tones were specifically designed to avoid harmonics.

   Ivor Darreg claimed that "DTMF" pitches coincided *fairly* well with 14TET.

   Also, there is a tone for each row and a tone for each column.  Each
button sounds two (ideally) sine waves, and one of the two tones is
identical for each button on the same row, or on the same column.

   Military phones have a fourth column, by way.