DTMF – also called tone dialling – is when a phone number is being dialled by tones at a specific frequency. Each number key on the phone is assigned a combination of two specific tones that are played when the key is being pressed.
DTMF is a newer version of dialing over analog lines, compared to the older pulse dialing method.
DTMF playback controls, if your phone plays the characteristic tone for each.
If DTMF playback is enabled, every time you press a number key on your phone, you will hear the characteristic tone for that key.
If DTMF playback is disabled, you will not hear a DTMF tone while pressing the number keys on your phone.