Electromagnetic Interference EMI and Radio-Frequency Interference RFI is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction.The disturbance could degrade the performance of a circuit or even stop it from functioning completely. In the case of a data path, these effects can range from an increase in error rate to the total loss of data.
Both man-made and natural sources generate changing electrical currents and voltages that can cause EMI: ignition systems, cellular network of mobile phones, lightning, solar flares and auroras. EMI affects AM & FM radio signals, mobile phones, televisions, as well as observations for radio astronomy and atmospheric science.