Ideally, the alternating electrical signal output by any device onto the electrical grid should be perfectly sinusoidal in form. A regular, non-sinusoidal signal can be made up of sinusoidal components at integer multiples of the so-called base frequency. These higher frequency components are known as harmonics, and whilst they make music sound nice, they cause problems in electrical networks (see Power Quality). The sinusoidal output from a power electronic converter (PEC) is digitally synthesised and hence is not a perfect sinusoid. Older PECs would inject significant harmonics on to the electrical grid; more modern ones do not.