Adaptive delta modulation systems for speech encoding-a survey

Linear delta modulation systems use a fixed step size for the 'staircase' approximation of the input signal. Small values of the step size introduce slope overload distortion during bursts of large signal slope. With large values of step size input signals of low amplitude were quantized very coarsely. This results in an inadequate dynamic range. To increase the dynamic range, the step size must be controlled from the time-varying slope characteristic of the input signal.