DTMF

Decoding

DTMF was originally decoded by tuned electrical filter banks. By the end of the 20th century, digital signal processing became the predominant technology for decoding. DTMF decoding algorithms typically use the Goertzel algorithm, although application of the MUSIC algorithm to DTMF decoding has been shown to outperform Goertzel and being the only possibility in cases when the number of available samples is limited. As DTMF signaling is often transmitted in-band with voice or other audio signals present simultaneously, the DTMF signal definition includes strict limits for timing (minimum duration and interdigit spacing), frequency deviations, harmonics, and amplitude relation of the two components with respect to each other (twist).