DTMF receiver

What does it do?

The DTMF receiver detects the standard DTMF digits. It is compliant with ITU-T Q.23, ITU-T Q.24, and the local DTMF specifications of most administrations. Its passes the test suites. It also scores *very* well on the standard talk-off tests.

The current design uses floating point extensively. It is not tolerant of DC or dial tone. It is expected that a DC restore stage will be placed before the DTMF detector. Whether dial tone tolerance matter depends on your application. If you are using the code in an IVR application you will need proper echo cancellation to get good performance in the prescence of speech prompts.

How does it work?

Like most other DSP based DTMF detector's, this one uses the Goertzel algorithm to look for the DTMF tones. What makes each detector design different is just how that algorithm is used.

Basic DTMF specs:

TODO:


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