For transmission of serial digitally coded signals over a path having a high-pass frequency characteristic synchronizing signals are transmitted in synchronizing word pairs at the beginning of each data block in which the synchronizing words are either identical or else both have the same number of bits of each of the two binary logic levels, for reduction of d.c. and low-frequency components while permitting the choice of a synchronizing signal word which occurs at most rarely in a television video signal, for example.