Testing is performed to determine a device's ability to operate in the presence of an interference signal propagated via a conductor. Malfunctions may be caused from either the magnetic (H) field or the electric (E) field component. The interference signal, typically in the range of DC to 400MHz, may be a carrier wave (CW), modulated signal, spike voltage or transient event

At frequencies above 400MHz, the preferred test method is Radiated Susceptibility because signals are much more likely to propagate via free space as opposed to via a conductor.