What are the DTMF tone frequencies?

DTMF stands for Dual Tone Multi Frequency.

DTMF tones are the tones you hear when you press a key on a standard telephone keypad.

The tone of each button is the sum of the column and row tones. This is why it is called "dual tone."

The ABCD keys do not exist on standard telephones.

DTMF Tone Frequencies

1209hz 1336hz 1477hz 1633hz

697hz 1 2 3 A

770hz 4 5 6 B

852hz 7 8 9 C

941hz * 0 # D

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