Detecting and correcting error in transmission

(1) retransmit multiple times (based on the error rate if the line) and for each byte, pick the pattern that appear most. Based on probability, the right pattern would be picked but there is no guarantee. 

(2) encode each byte with additional bits. The received bits can match against the encoding pattern.  The closest matching pattern is the transmitted byte. This is how hamming code works. 

(3) two dimensional parity ones the text in 2 dimensional block. Then take a checksum across the row and down the column. This allows to pinpoint the byte that has changed (error). The byte can be recomputed from the vertical and horizontal checksum. In reverse.