In telecommunication, a transverse redundancy check (TRC) or vertical redundancy check is a redundancy check for synchronized parallel bit streams, (a) that is based on the formation of a block check following preset rules, (b) in which the check-formation rule applied to blocks is also applied to characters, and (c) in which the check is made on parallel bit patterns.

When the TRC is based on a parity bit applied to each character and block, the TRC can only detect, with limited certainty, whether or not there is an error. It cannot correct the error. Detection cannot be guaranteed because an even number of errors in the same character or block will escape detection, regardless of whether odd or even parity is used.

Two-dimensional arrays of bits may be used to represent characters or blocks in synchronized parallel data streams. When a TRC is combined with a longitudinal redundancy check, individual erroneous bits can be corrected.

Source: From Federal Standard 1037C and from MIL-STD-188