Method for error correction

An improved method of error correcting words of pulse code modulated data which are encoded in first and second error correcting blocks, said first error correcting block containing said words of data in a plurality of channels forming a first arrangement state and first check words associated therewith and said second error correcting block containing said first arrangement state and first check words, delayed at each channel by different delay times to form a second arrangement state, and second check words associated therewith;

• and in which said encoded data is decoded by initially decoding said second error correcting block in a first stage, delaying each channel of said second arrangement state by different delay times so as to reform said first error correcting block and subsequently decoding the reformed first error correcting block so as to again place said data in said first arrangement state:
• said improved method of error correcting comprising the steps of
• correcting at least one word errors and detecting more than two word errors contained in said second error correcting block during said initial decoding;
• adding indicators of at least first and second kinds which respectively indicate correction of one word errors and detection of errors of more than two words, said indicators being added to at least corresponding erroneous words within said second error correcting block during said initial decoding;
• correcting at least one word errors contained in said first error correcting block during said subsequent decoding;
• and
• determining the kinds of said pointers and their respective numbers thereof contained in said first error correcting block during said subsequent decoding so that in accordance with the results of said determination all remaining errors are detected and corrected and erroneous error correction is avoided.