This part of IEC 61869 is a product family standard and covers only additional general requirements for low-power instrument transformers (LPIT) used for a.c. applications having rated frequencies from 15 Hz to 100 Hz covering MV, HV and EHV or used for d.c. applications. This product standard is based on IEC 61869-1:2007, in addition to the relevant product specific standard. This part of IEC 61869 does not cover the specification for the digital output format of instrument transformers. This part of IEC 61869 defines the errors in case of analogue or digital output. The other characteristics of the digital interface for instrument transformers are standardised in IEC 61869-9 as an application of the standards, the IEC 61850 series, which details layered substation communication architecture. This part of IEC 61869 considers additional requirements concerning bandwidth. The accuracy requirements on harmonics and requirements for the anti-aliasing filter are given in the normative Annex 6A.4. The general block diagram of single-phase LPITs is given in Figure 601. According to the technology, it is not absolutely necessary that all parts described in Figure 601 are included in the instrument transformer. As an example, for low-power passive transformers (LPITs without active electronic components) the blocks are composed only with passive components and there is no power supply. Figure 601 - General block diagram of a single-phase LPIT