 CRCs are calculated before and after transmission or duplication, and compared to confirm that they are equal.A CRC detects all one- or two-bit errors, all odd errors, all burst errors if the burst is smaller than the CRC, and most of the wide-burst errors.Parity checks can be applied to single characters (VRC—vertical redundancy check), resulting in an additional parity bit or to a block of data (LRC—longitudinal redundancy check), issuing a block check character.