This standard applies to impedance filters in a mains communication system for phase to neutral voltage not exceeding 250 V a.c. and a nominal current not exceeding 125 A, intended for household and similar fixed installation including residential, commercial and light industrial buildings. This standard also applies to "plug-in filters". These filters (see Figure 1) are used to set a suitable impedance, in the nominal frequency range of the mains signalling system, at any point of the low voltage mains network where a low impedance equipment is connected, in order to allow reliable operation of mains signalling system. These impedance filters can be used either in utility or consumer networks. They may also be used in conjunction with incoming filters and segmentation filters.