DTMF - DUAL TONE MULTI FREQUENCY signalling

Dual-tone multi-frequency is abbreviated as DTMF. This is the proper name of 'touch tone' technology, used in push-button phones and revolving around the sounds made by each key when pressed.

Dual-tone multi-frequency dialing refers to the fact that when a non-rotary phone dials, it sends two tones at the same time. When these tones are put together, a distinct sound is created, which is recognized by the switch at your phone service provider.

DTMF means Dual Tone Multi Frequency this is every key on your phone key pad, each key generates two tones over top of each other hence the Dual Tone of DTMF. This also applied to touch tone telephones that are hardwired in homes and businesses, they also use DTMF keying.

DTMF (Dual Tone Multi Frequency) usually called contact I.D. or SIA format in the alarm industry.