DSPLab for Delphi

DTMF demo

DTMF means Dual Tone Modulation Frequency. This systems is intended to transmit keys pressed on a keyboard through an audio channel such as a telephone line or a radio connection. For each pressed key two audio frequencies are emitted: one (higher) corresponds to the column in which the key is in, and the other (lower) corresponds to the row. This encoding handles a maximum of 4 rows and 4 columns, that means 16 keys (from 0 to 9, *, #, and from A to D).

The DTMF demo shows how to decode the DTMF-frequencies using TdspFFT component.

download sources (zip, ~6K)
download executable (zp, ~174K)

download sample wav-files (zip, ~330K)