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Abstract

A speech processing system having an encoder comprising apparatus for receiving successive samples of PCM (pulse code modulated) encoded speech signals and apparatus, for applying sequential groups of the PCM encoded speech signals as primary vector signals to an encoder code book memory for selecting code words stored in the memory most closely approximating the vector signals. Apparatus is included for outputting to an output line the selected code words at a first bit rate. Further apparatus connects the selected code words to converted vector signals. The primary vector signals and converted vector signals are compared and difference signals result. The difference signals are quantized error signals are provided thereby. The quantized error signals are applied to the output line at the first or at a second bit rate to enable the processing system to transmit the speech signals at an effective bit rate constituting double the first bit rate or the sum of the first and second bit rate, or the quantized error signals is inhibited from being applied to the line. The processing system can thereby transmit the speech signals at an effective rate of the first bit rate thus incressing the traffic carrying capacity of the line.

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First Claim