In-Band Signaling: Dual-Tone Multifrequency Dialing

One late night many decades ago, I chanced upon a technical description of the Touch-Tone system. The book I was reading had an explanation of how each key on a telephone sends a combination of two to

Dual-tone Multi-Frequency (DTMF) – Explanation and common issues - WHYPAY?

In-band Signaling

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Infographic explaining what is DTMF.

Touch tone phone pitches DTMF

What Is DTMF?

Dtmf, Hackaday

DTMF

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Goertzel Algorithm - Evaluating DFT without DFT

Touch-Tone Telephone Dialing » Cleve's Corner: Cleve Moler on Mathematics and Computing - MATLAB & Simulink

Dual tone multiple frequency

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