Abstract: A digital tone generator (1110) includes a digital signal generator (1138) which generates a digital waveform data sequence which is representative of a tone having a predetermined waveform, and an adaptive duty cycle pulse-width modulator (1132) which is responsive to the digital waveform data sequence for generating an an adaptive duty cycle period characterized by a pulse-width modulated digital tone signal having a variable frequency and duty cycle which is generated by selecting a variable number of clock pulses of a predetermined reference clock (31).

Abstract: A digital tone generator (1110) includes a digital signal generator (1138) which generates a digital waveform data sequence which is representative of a tone having a predetermined waveform, and a pulse-width modulator (1132) which provides an adaptive duty cycle period (622, 630) which is responsive to the digital data waveform data sequence for selecting clock pulses of a number sufficient to generate a pulse-width modulated digital tone signal. The digital tone generator (110) can also include a low pass filter (36) which processes the pulse-width modulated digital tone signal to generate an analog tone signal. The digital waveform sequences generated by two digital tone generators (38, 40) can be digitally added by a digital adder (28) to provide a composite tone data signal, which can be processed by the adaptive pulse-width modulator (700) to produce a pulse-width modulated tone signal representative of a DTMF tone.