Interferential current therapy is essentially a deeper form of TENS. In essence, IFT modulates a high frequency (4000 Hz) carrier waveform with the same signal produced by a TENS unit. The high frequency carrier waveform penetrates the skin more deeply than a regular TENS unit, with less user discomfort for a given level of stimulation. Deep in the tissues, the carrier waveform is cancelled out, resulting in a TENS-like signal deep under the skin.

Interferential electrical stimulation's is a unique way of effectively delivering therapeutic frequencies to tissue. Conventional TENS uses a low frequency electrical signal of 2-160 Hz per second. However, Interferential stimulators use a fixed carrier frequency of 4,000 Hz per second and also a second adjustable frequency of 4,001-4,400 Hz per second. When the fixed and adjustable frequencies combine, they produce the desired signal frequency (Interference frequency). Interferential stimulation is concentrated at the point of intersection between the electrodes. This concentration occurs deep in the tissues as well as at the surface of the skin. Conventional TENS stimulators deliver most of the stimulation directly under the electrodes. Thus, with Interferential Stimulators, current perfuses to greater depths and over a larger volume of tissue than other forms of electrical therapy. This explains why Interferential current may be most suitable for treating patients with deep pain, for promoting osteogenesis in delayed and nonunion fractures and in pseudothrosis, for stimulating deep skeletal muscle to augment the muscle pump mechanism in venous insufficiency, and for depressing the activity of certain cervical and lumbosacral sympathetic ganglia in patients with increased arterial constrictor tone.