PCM telecommunication system with merger of two bit streams along a common signal path

A system for transmitting two groups of digitized message samples derived from voice signals, arriving simultaneously at a first terminal in the shape of two sets of 2n-bit code words respectively forming part of recurrent frames in two original bit streams, to a second terminal via a common PCM signal path linking said terminals, comprising:

• first transcoding means including an adaptive differential quantizer at said first terminal for converting 2n-bit code words into substantially equivalent n-bit code words;
• first circuit means at said first terminal for feeding the 2n-bit code words from said original bit streams to said first transcoding means;
• first synthesizing means at said first terminal connected to said first transcoding means for interleaving n-bit words derived from the 2n-bit code words of said original bit streams in frames of a composite bit stream having the same length as the frames of said original bit streams, said first synthesizing means being coupled to said common signal path for transmitting said composite bit stream to said second terminal;
• second transcoding means at said second terminal complementary to said first transcoding means for reconverting n-bit words into substantially equivalent 2n-bit code words;
• second circuit means at said second terminal coupled to said common signal path for feeding the n-bit code words of said composite bit stream to said second transcoding means for reconversion into 2n-bit code words substantially corresponding to the 2n-bit code words of said original bit streams;
• second synthesizing means at said second terminal connected to said second transcoding means for assembling the reconverted 2n-bit code words into frames forming part of two reconstituted bit streams substantially replicating said original bit streams;
• a code expander in said first circuit means upstream of said differential quantizer;
• and
• a complementary code compressor inserted between said second transcoding means and said second synthesizing means.

A method of transmitting two groups of digitized message samples, arriving simultaneously at a first terminal in the shape of two sets of 2n-bit code words respectively forming part of recurrent frames in two original bit streams, to a second terminal via a common PCM signal path linking said terminals, comprising the steps of converting each 2n-bit code word at said first terminal into a substantially equivalent n-bit code word, interleaving the n-bit code words from original bit streams in frames of a composite bit stream having the same length as the frames of said original bit streams, transmitting said composite bit stream over said signal path to said second terminal, separating the interleaved n-bit code words of said composite bit stream at said second terminal, reconverting the separated n-bit code words into 2n-bit code words substantially corresponding to the 2n-bit code words of the original bit streams, and assembling the reconverted 2nbit code words into frames forming part of two reconstituted bit streams substantially replicating said original bit streams, the frames of said original, composite and reconstituted bit streams being identically structured and being each divided into m message time slots assigned to said code words and k supplemental time slots reserved at least in part for supervisory signal codes, the message time slots of said composite bit stream being split into halves for accommodating respective n-bit code words derived from 2n-bit code words occupying homologous time slots in said original bit streams, at least some supervisory signal codes being transferred substantially unchanged from supplemental time slots of said original bit streams via supplemental time slots of said composite bit stream to supplemental time slots of said reconstituted bit streams.

A method of transmitting two groups of digitized message samples, arriving simultaneously at a first terminal in the shape of two sets of 2n-bit code words respectively forming part of recurrent frames in two original bit streams, to a second terminal via a common PCM signal path linking said terminals, comprising the steps of converting each 2n-bit code word at said first terminal into a substantially equivalent n-bit code word, interleaving the n-bit code words from said original bit streams in frames of a composite bit stream having the same length as the frames of said original bit streams, transmitting said composite bit stream over said signal path to said second terminal, separating the interleaved n-bit code words of said composite bit stream at said second terminal, reconverting the separated n-bit code words into 2n-bit code words substantially corresponding to the 2n-bit code words of the original bit streams, and assembling the reconverted 2n-bit code words into frames forming part of two reconstituted bit streams substantially replicating said original bit streams, the frames of said original, composite and reconstructed bit streams being identically structured and being each divided into m message time slots assigned to said code words and k supplemental time slots reserved at least in part for supervisory signal codes, the message time slots of said composite bit stream being split into halves for accommodating respective n-bit code words derived from 2n-bit code words occupying homologous time slots in said original bit streams, one of said supplemental time slots occurring at the beginning of each frame and containing a synchronization code which is locally generated at said first terminal for said composite bit stream and at said second terminal for each of said reconstituted bit streams.

A system for transmitting two groups of digitized message samples, arriving simultaneously at a first terminal in the shape of two sets of 2n-bit code words respectively forming part of recurrent frames in two original bit streams, to a second terminal via a common PCM signal path linking said terminals, comprising:

• first transcoding means at said first terminal for converting 2n-bit code words into substantially equivalent n-bit code words;
• first circuit means at said first terminal for feeding the 2n-bit code words from said original bit streams to said first transcoding means;
• first synthesizing means at said first terminal connected to said first transcoding means for interleaving n-bit code words derived from the 2n-bit code words of said original bit streams in frames of a composite bit stream having the same length as the frames of said original bit streams, said first synthesizing means being coupled to said common signal path for transmitting said composite bit stream to said second terminal;
• second transcoding means at said second terminal complementary to said first transcoding means for reconverting n-bit code words into substantially equivalent 2n-bit code words;
• second circuit means at said second terminal coupled to said common signal path for feeding the n-bit code words of said composite bit stream to said second transcoding means for reconversion into 2n-bit code words substantially corresponding to the 2n-bit code words of said original bit streams;
• and
• second synthesizing means at said second terminal connected to said second transcoding means for assembling the reconverted 2n-bit code words into frames forming part of two reconstituted bit streams substantially replicating said original bit streams;
• the frames of said original, composite and reconstituted bit streams being divided into a predetermined number of time slots identical for all frames, each time slot encompassing 2n-bit periods, said first circuit means comprising a pair of memories for respectively storing the code words of any frame of said original bit streams, counting means for successively reading out the code words of each frame stored in said memories, and switch means for alternately feeding the read-out code words from said memories to said first transcoding means, said frames being identically structured and being each divided into m message time slots assigned to said code words and k supplemental time slots reserved at least in part for supervisory signal codes, said first circuit means including a pair of first branches bypassing said first transcoding means and extending from said memories to said first synthesizing means for transferring supervisory signal codes substantially unchanged from supplemental time slots of said original bit streams to supplemental time slots of said opposite bit stream, said second circuit means including a pair of second branches bypassing said second transcoding means and extending from said common signal path to said second synthesizing means for further transferring said supervisory signal codes substantially unchanged to supplemental time slots of said reconstituted bit streams.