... :High frequency disturbances that occur within a short period of time (milliseconds),RFI & noise are very common in all parts ... noise from nearby equipment,transmittes,mobile phones,switching on/off of certain loads,fiuorescent lights,motor speed controls,light dimmers. ... be instantaneous,severe and irreparsble.What caues it?On return of mains supply after power cuts,under-sized utility oscillating ...