Digital signal transmission apparatus

A digital signal transmission apparatus in which a digital signal having a header block of a predetermined length is transmitted. The header comprises a synchronization signal and auxiliary data. The auxiliary data is made up of first data or second data and a redundant error detection code. The redundant code is formed so that syndrome patterns of the error detection code are different in order to distinguish the block in which the first data is contained as the auxiliary data on the reception side, from the block in which the second data is contained as the auxiliary data so that a plurality of headers having different contents can be distinguished on the reception side.