In some cases, the noise current is superimposed on the signal current.
The signal current is generally low frequency, while the noise current in most cases is high frequency.
To reduce noise current, it is desirable to give much greater resistance to the noise current than the signal current. The noise current magnetic flux (the noise current itself) can therefore be reduced by passing the signal line though a ferrite core, which has a high degree of resistance, and where magnetic flux is generated by the noise current.
It works the same as the BLM!
Differential currents, or currents with different directions and different phases, exist in some cases.
They exist in cases in which the directions of the currents are reversed, and the noise affects both cables the same way (common noise).
In such cases, by passing the two cables through the ferrite core, the magnetic fluxes generated by the signal currents cancel each other out, and no resistance is imparted. On the other hand, since the magnetic fluxes generated by the noise currents do not cancel each other out, they are reduced in response to the ferrite's resistance (magnetic resistance), thereby reducing the noise current. Since the impact on the signal current is small, this approach is useful when you want to avoid dulling the waveform.
It works the same as the DLP/DLW!