Some typical sources of electromagnetic emissions are transmitters, pulse generators, oscillators, digital logic circuits, switching power supplies and converters, relays, motors, and line drivers. A logic or similar pulse may often exhibit rounding at the start and end of the rising/falling edge, with a subsequent reduction in high-frequency emissions, compared to a pure trapezoidal pulse. From the envelopes of typical wave shapes it is clear that the high-frequency components are at a lower magnitude than the fundamental but can exist at amplitudes that may be problematic to other sections of a system or equipment. It is therefore not surprising that designers are often amazed when equipment fails radiated or conducted emission requirements at frequencies orders of magnitude above the fundamental frequencies used in the equipment. Sometimes the repetition rate of the impulsive noise coincides with a resonance frequency, and a sine wave or damped sinewave is generated. The characteristics and magnitude of noise from the different manufacturers' converters were relatively similar.