Measuring conducted emission is the simplest and most affordable method of getting some indication of whether a design can meet EMI/EMC requirements. A LISN (Line Impedance Stabilization Network), like the project we present here in cooperation with Würth Elektronik, is an indispensable part of this. In this article we will discuss what an LISN is for. In part two we will see how the circuit is constructed and how it is used in EMC pre-compliance testing.