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Frequency shift telegraphy is described and compared with amplitude modulation telegraphy under various conditions found in radio and wire transmission. Experimental data are given to demonstrate the influence of various design factors on the over‐all performance under these conditions. It is shown that the most outstanding characteristic of the frequency shift method is its ability to accept large and rapid changes in signal amplitude. Frequency shift telegraphy thus proves to be of great advantage for use in the H.F. radio range. Frequency shift telegraphy also shows an advantage over amplitude modulation telegraphy with respect to noise. For applications where the level variations are small or slow the advantage of the frequency shift method over amplitude modulation is relatively small.