Abstract: A method for data regeneration of protected data is provided wherein an error rate of a reception signal with error correcting code is identified. A sampling time and a decision threshold are provisionally varied in a predetermined range until an optimum sampling time and an optimum decision threshold are recovered by identifying the transmission error during this procedure. As a result, additional transmission errors have no influence due to the error correction.

Abstract: A method for transmitting an additional data signal and a useful data signal, via optical connections, in an optical network, wherein the additional data signal is transmitted on the same channel as the useful data channel and converted into code sequences which are, in turn, superimposed on the useful data signal with a small amplitude. At the reception end, the additional data signal is recovered by cross-correlation.

Abstract: For checking transmission and monitoring devices of digital transmission links, it is known to overlay code errors into the digital signals to be transmitted. In accordance with the invention, the code errors are overlaid such that given the prerequisite of a redundant transmission code, no falsification of the informational content of the digital signals arises. In accordance with the invention, this is undertaken in that the mode condition in the connected mode memory is modified and output to the mode input of the code conversion logic as a new sequential mode.