Page 42 of 72 EN109-1498751-47 IFU
13 Description – Current waveforms and Ultrasound parameters
4 pole interferential currents
With the interferential current type a medium frequency carrier frequency is used to pass the low
frequency stimulation (beat) frequency through the skin. The relatively low resistance of the skin to the
carrier frequency contributes to the patient comfort that is often associated with this current type.
Interferential currents are all AC currents without any residual DC components. Several variations of
the interferential current type are known, of which the following are available in the 4-series:
Classical interferential
With this therapy method four electrodes are used and two non-modulated currents are generated.
The frequency of one channel is fixed at the carrier frequency, while the other channel has a variable
frequency, based on the Beat frequency and Frequency Modulation settings. Interference occurs
where the two currents intersect in the tissue. The modulation depth (which determines the current
amplitude of the stimulation) depends on the direction of the currents, and can vary from 0 to 100%.
100% modulation depth only occurs at the diagonals (and hence at the intersection) of the two
currents. This is of course a theoretical situation, based on the assumption that the tissue is
homogeneous. In reality, the tissue is heterogeneous, so that the current balance between the two
channels has to be used to obtain the 100% modulation depth (fig 2). The current balance can also be
used to compensate for differences in sensation occurring under the electrodes.
Isoplanar vector
The isoplanar vector technique is intended to increase the area where effective stimulation occurs.
Amplitude modulation occurs in the equipment and a special phase relation between the two
channels ensures a 100% modulation depth between the four electrodes in all positions.
The advantage of this method is that the positioning of the four electrodes to effectively treat the
affected tissue is less critical. The sensation of the Isoplanar vector mode is soft and equally
divided over the treatment area.
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