Signal coding for telephone communication system

Abstract

A telephone communication system reversibly converts input signals into adaptive delta modulated (hereafter ADM) signals and then into pulse code modulated signals. In one embodiment, a path for sending signals from a subscriber switch to a central office of a telephone communication system receives analog signals, for example voice signals, in a comparator which also receives an analog signal from an integrator for periodically providing ADM signals. The ADM signals are provided to means responsive to patterns of the ADM signals for providing a pattern controlled signal to the integrator which then generates the analog signal compared with input signal for forming the ADM signals. The ADM signals are also transmitted to digital means detecting the patterns of the ADM signals and responsive to each ADM signal and the detected patterns of the ADM signals for providing a linear pulse code modulated (hereafter LPCM) signal representing a signal increment corresponding to that represented by the ADM signal. Each LPCM signal increment is then added to the total of each preceding LPCM signal increment to form LPCM signals representing the input analog signal. The LPCM signals are then periodically sampled and each sampled LPCM signal converted into a corresponding compressed pulse code modulated (hereafter CPCM) signal for switching and further transmission. In a receiving path of the embodiment a converter converts input CPCM signals into LPCM signals. Each LPCM signal together with a locally generated signal representing the preceding LPCM signal is provided to a digital comparator which forms an ADM signal encoded in response to the relative magnitudes of the input and generated LPCM signals. The ADM signals are then provided to further means controlled by patterns of the ADM signals for providing a pattern controlled signal to an integrator which integrates the pattern controlled signal into an analog signal corresponding to the CPCM signal input to the receiving path of the embodiment.

Dependencies are inferred from the claim text.