Signalling systems for submarine telegraph circuits

An account is given of the characteristics of submarine telegraph cables and terminal apparatus and the noise spectra for simplex-and bridge-duplex-operated cables. By using simplified expressions for the noise spectra it is possible to determine the number of signalling conditions for the maximum rate of transmission of information with a given proportion of errors. Synchronous telegraph systems using the 5-unit teleprinter code are described, and a brief account is given of the methods by which the optimum number of signalling conditions may be used for transmission over the cable whilst retaining the advantages of 5-unit working at the terminals.