DTMF is by far the most popular system. Apparently Adobe Audition (formerly Cool Edit Pro) includes DTMF and another set of tones called "MF Signals (CCITT R1)"

DTMF is by far the most popular system. Apparently Adobe Audition (formerly Cool Edit Pro) includes DTMF and another set of tones called "MF Signals (CCITT R1)", which I'll assume is quite obscure. The "MF Signals" could be used in creative exploration. Example: https://fun--tutorial.blogspot.com/2012/02/create-dtmf-telephone-tone.html https://fun--tutorial.blogspot.com/2012/02/create-dtmf-telep...