Method and system for detecting a predetermined number of unidirectional errors

In a data transmission system having a data source for producing an n-bit information code, a data sink for accepting a data word, and a data transmission channel for transmitting a data word from said data source to said data sink, a system for detecting at least t unidirectional errors in the transmission of said information code over said data transmission channel, comprising:

• (a) first code generation means, associated with said data source, for producing, for a given information code in a predetermined set of n-bit information codes produced by said data source, a first m-bit check code according to the criteria that for all possible pairs of (n+m)-bit data words formed by said predetermined set of n-bit information codes and corresponding m-bit check codes, either the pair of words is unordered or the Hamming distance between the data words of the pair is greater than or equal to t+1, and there is at least one pair of said data words which is unordered and whose Hamming distance is less than t+1;
• (b) transmission means for transmitting over said transmission channel a data word comprising an information code and its corresponding first check code;
• (c) second code generation means, associated with said data sink, for producing, for a given information code accepted by said data sink, a second m-bit check code according to said criteria;
• and
• (d) comparator means, associated with said data sink, for comparing, for a given data word accepted by said data sink, said first check code and said second check code and producing an indication of any disparity therebetween.