Line Impedance Stabilization Networks (LISN) is the standard transducer for measuring conducted emissions in many EMC test standards. They are invasive transducers which must be connected in series with the conductors being tested to standardize their CM and DM impedances. A LISN couples the interference from the EUT connection to the measuring equipment and at the same time presents stable and well-defined impedance to the EUT across the desired frequency range. The actual measured voltage depends on the ratio of the EUT’s source impedance and the LISN’s load impedance, so if the impedance are not stabilized, there would be no repeatability between different test locations. CISPR defines the LISN and its impedance for some different classes of network. The most common is known as the “50Ohms/50µHž +5Ohms” network, since the impedance curve is determined by these values.