Adaptive delta modulator for telephony

An adaptive version of the basic delta modulator employing full-width pulses and RC integration has been designed. A digital technique is used to sense the level of the input signal and to control the amplitude of the pulses supplied to the RC integrator in the feedback circuit. For an 800 Hz sinewave input a signal/quantisation-noise ratio of 32 dB has been obtained over a dynamic input range of 30 dB.