Introduction In preceding chapters a.c. supplies have been assumed to be sinusoidal, this being a form of alternating quantity commonly encountered in electrical engineering. However, many supply waveforms are not sinusoidal. For example, saw-tooth generators produce ramp waveforms, and rectangular waveforms may be produced by multivibrators. A waveform that is not sinusoidal is called a complex wave. Such a waveform may be shown to be composed of the sum of a series of sinusoidal waves having various interrelated periodic times.