Abstract: A system for detection of errors in received data can also provide for the correction of errors so detected. The system has a FSK decoder section (10), an error detection module (24) and an error correction module (12). The received data, RXSIGIN, is bandlimited by bandpass filters (14), with the resultant waveforms provided to the error detection module (24) on lines (29). The FSK decoder section (10) also decode the digital data RXDATA within RXSIGIN, and provides RXDATA to both the error correction detection module (24) on line (21) and the error correction module (12) on line (33). Error detection takes place on a bit-by-bit basis by comparison of the resultant waveforms being compared against an ideal representation thereof, a quality factor is ascribed to each bit on the basis of the comparison, and a determination of which bits are suspected to be in error is made by comparison of the quality factor against a threshold value (30).