Dual-tone Multi-Frequency (DTMF) – Explanation and common issues - WHYPAY?
Figure 1 from 60-channel dual tone multi-frequency signaling receiver based on Goertzel algorithm on single 100MIPS TMS320C54 DSP platform | Semantic Scholar
Dual Tone Multi-Frequency signal generation and testing - YouTube
DTMF and RFC 2833 / 4733 | Tao, Zen, and Tomorrow
Black DTMF Decoding Algorithm
DTMF Signaling
What is DTMF? How Does Dual-Tone Multi-Frequency Work? - United World Telecom