Dual tone multi-frequency (DTMF),

Definition of Dual tone multi-frequency (DTMF):

1. Touch tone used in non-rotary type dial (push button) phones. DTMF uses a combination of two (one low frequency and one high frequency) tones to identify the dialed number or a signal. Eight such frequencies are assigned to the four rows and four columns of a typical push-button type dial (keypad). All modern modems also generate DTMFs.