A Delta-Sigma DELTA SIGMA modulator for one-bit analog to digital conversion of a signal, such as a telephone voice channel switch to digital form is disclosed. The circuit incorporates integration operative as low-pass filtering. The voice signal is sampled at a rate high compared to the highest voice channel frequency component. Sampled instantaneous signal values are integrated, re-sampled and again integrated to reduce encoding noise. Finally, a bi-level sense identifying circuit links the second integrator output to a D type flip-flop providing the one-bit encoded output. The sampling and integrator control is effected by switching in a capacitor charge shifting arrangement under clock control and feedback is applied as a capacitor switching program modifications.
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