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An outstanding characteristic of impulse noise on telecommunication channels is its high variability. A scientifically designed sampling plan was incorporated to conduct a survey of this type of noise on major Bell System carrier facilities. The results show mean impulse noise levels to range from 51 to 66 dBrn, and standard deviation of the nearly normal cumulative distribution functions of the levels to vary from 3.5 to 7.7 dB. Slopes of the peak noise amplitude distribution were found to range from 1.0 to 33.0 dB per decade with 90 percent of them falling in the range of 2.0 to 10.0 dB per decade. The variability of the noise parameters within single carrier groups or common routes was found, on the average, to be considerably smaller than exhibited by the entire system.