LISNs, or line impedance stabilization networks, are instruments used in conducted and radiated EMC emissions and susceptibility testing. Primarily, LISNs provide an accurate impedance and radio frequency to the equipment/device under test (EUT/DUT). The goal of this testing is to get repeatable measurements of the EUT noise that is present at the LISN measurement port. LISNs also play a role in preventing high-frequency noise emitted by a power source from coupling in the system, isolating unwanted radio frequency (RF) signals from the power source. There are a variety of LISNs for analyzing DC, single-phase and three-phase AC power connections. Attributes such as voltage rating, current rating, number of power conductors, and insertion loss are all helpful variables to keep in mind when selecting a LISN to most effectively complete your testing.