The Standard
Dual Tone Multi Frequency (DTMF) signalling is widely used in telephony. DTMF signals consist of two sinusoidal signals, one sinusoid from the high frequencies (1209, 1336, 1477 and 1633Hz) and the other from low frequencies (697, 770, 852 and 941Hz). Four frequencies from each group gives a total of 16 combinations, and are represented for digits 0 to 9, A to D, * and #.
The function of the DTMF generator is to generate the corresponding DTMF signal for a given digit, where as the DTMF detector identifies the digit from the given signal samples.
