Error reduction speech communication system

An error reduction arrangement in a differential pulse code modulation communication system comprising transmitting means including means for receiving an input analog signal, means responsive to said analog signal for producing successive blocks of first coded sample signals, means for converting each block of first coded sample signals into a block of differential pulse code modulation coded signals and means for applying said differential pulse code modulation coded signals to a communication channel;

• and receiving means comprising means for converting each block of differential pulse code modulation coded signals into a block of second coded sample signals, and means responsive to the blocks of second coded sample signals for generating a replica of said analog signal
• CHARACTERIZED IN THAT
• said transmitting means further comprises feature signal generating means responsive to the blocks of differential pulse code modulation coded signals for generating a signal representative of a set of first features of the waveform of the analog signal and a signal corresponding to a set of second features of the waveform of said analog signal, and means for applying the sets of first and second waveform feature signals to said communication channel;
• and said receiving means further comprises means jointly responsive to said received first waveform feature signal and the blocks of second coded sample signals for detecting erroneous second coded sample signals, and means operative upon detection of each erroneous second coded sample signal jointly responsive to the received second waveform feature signal and the second coded sample signals for modifying the value of said detected erroneous second coded sample signal to reduce errors in said analog signal replica.

A method for reducing errors in a communication system comprising a transmitter including means for receiving an input signal, means for converting said input signal into blocks of coded signals, and means for applying said blocks of coded signals to a transmission medium;

• and a receiver for converting the coded blocks of signals from said transmission medium into a replica of said input signal;
• said method being CHARACTERIZED IN THAT:
• in the transmitter, a signal representative of a first set of features of the waveform of said input signal and a signal representative of a second set of features of the waveform of said input signal are generated responsive to said blocks of coded signals, and said first and second waveform feature signals are applied to said transmission medium;
• in said receiver, corrupted received coded signals are detected responsive to said first waveform feature signal and said received blocks of coded signals;
• and, jointly responsive to said second waveform feature signal and the received blocks of coded signals upon detection of a corrupted received coded signal, the value of the corrupted received coded signal is modified to reduce errors in said input signal replica.