Electromagnetic Interference (EMI, also RFI - Radio Frequency Interference) is an undesirable physical phenomenon or the effect of electric, magnetic or electromagnetic fields, electric currents or voltages of an external or internal source that disrupts the normal operation of technical equipment, or causes deterioration of technical characteristics and parameters of these funds. 
 For the purposes of electronic warfare, a deliberate electromagnetic effect is used aimed at an object, which is undesirable for it, that is, an interference. 
 By origin, interference is divided into natural and artificial. 
 Electromagnetic or radio frequency interference (pickup) in the power supply network and in electronic circuits arises from the operation of electrical machines and electronic devices. They can be reduced by shielding and installing filters on the inputs and outputs (for example, in the power supply). 
 The intensity of all types of interference is measured either in units of electric field strength V / m, mV / m, μV / m, or in units of power flux density W / m2, mW / m2, μW / m2