1. A method of synchronizing a data sink with a data source in a data transmission system in which data provided by the data source is encoded as code words (c.sub.L) in a linear block code and such code words are transmitted as messages over a transmission channel in the form of sequentially linked modified code words (c'.sub.L), the modified code words (c'.sub.L) being formed by linking each data code word (c.sub.L) to a protection word (w.sub.L) which is transmitted over such transmission channel, characterized in that: each protection word (w.sub.L) identifies the position within the transmitted message of the code word (c.sub.L) linked thereto; the modified code words (c'.sub.L) are interleaved bit-sequentially, transmitted, and at the receiver are de-interleaved to derive received code words (c.sub.K); and each received code word (c.sub.K) is linked to a check word (w.sub.K) which characterizes the position of such code word (c.sub.K) within the received message.