21. A communications network, comprising: a plurality of nodes, wherein information is transmitted between nodes in the form of a data word representing the information and a check word for error detection, wherein said data word and said check word include a plurality of code symbol groups; wherein as a data word symbol group is received at a node, said symbol group is modified to produce a modified data word symbol group; first means for processing said data word symbol group and said modified data word symbol group and for producing a comparison symbol group in response thereto; means for encoding said comparison symbol group to produce an encoded symbol group; second means for processing said encoded symbol group and said check word symbol group after each encoded symbol group is produced to produce a modified check word symbol group, wherein said modified check word symbol group conforms with said modified data word symbol group; and wherein said modified data word symbol group and said modified check word symbol group are transmitted to another node.
27. The communications network of claim 21 wherein when symbols of the data and the check words are binary numbers the second means includes an exclusive OR gate having a first input terminal responsive to each symbol of the encoded symbol group, and a second input terminal responsive to each symbol of the check word symbol group for performing the exclusive OR function on a bit-by-bit serial basis to produce each symbol of the modified check word symbol group at the output terminal thereof.