Definitions for "Dual-tone multifrequency"
A way of signaling consisting of a push-button or touch tone dial that sends out a sound consisting of two discrete tones that are picked up and interpreted by telephone switches (either PBXs or central offices).
"Signaling that uses a simultaneous combination of a lower and higher group of frequencies to represent each digit or character. The lower tones are 697
A signaling system that sends pairs of audio frequencies to represent digits on a telephone keypad. It is often used interchangeably with the term Touchtone (an AT&T trademark).