DTMF (Dual Tone Multi-Frequency)

DTMF (Dual Tone Multi-Frequency) is the transmission of a selected number or symbol (*, #) via the generation of a specific pair of tones when that number’s or symbol’s button on a push button telephone is pressed. The tones are audible and transmitted within the voice band.

NENA-STA-027, NENA E9-1-1 PSAP Equipment Standards