This part of IEC 61643 covers the application of surge isolation transformers (SITs) that are
used in telecommunication transformer applications with signal levels up to 400 V peak to
peak. These transformers have a high rated impulse voltage with or without screen between
the input and output windings. SITs are components for surge protection and are used to
mitigate the onward propagation of common-mode voltage surges. This document describes
SITs' selection, application principles and related information. This document does not cover
power line communication transformers.