Nemec23–26 promoted the therapeutic use of interferential currents and advocated the use of sinusoidal AC at frequencies around 5 kHz. He argued that the 2 currents of slightly different
frequency “interfere” in tissue, producing maximum stimulation in the region of intersection of the 2 current paths, and that the resulting (endogenous) current at depth would be modulated at the “beat” frequency, which is the difference in frequency of the 2 currents