"PREFACE This publication has been prepared by IEC Technical Committee No 25@ Quantities and Units@ sand their Letter Symbols. When Publication 27-1 was originally prepared@ electro technology concerned itself primarily with sinusoidal waveforms Accordingly@ Clause 4 that publication gave special notations suitable for sinusoidal waves@ but did not cover more complicated situations. In modern technology@ there is need to distinguish between ""peak"" and ""maximum"" to indicated values of running averages of various types This publication was therefore developed by TC 25@ not with the intention of changing Publication 27-1 but for purpose of extending its usefulness to the problems of modern practice which involve non-sinusoidal waveforms@ noise and other complications The present publication is therefore a supplement to Publication 27-1"