Line impedance stabilization network (LISN) such as NNB 51/52 are used to measure distortion signals on the mains cord of an electrical equipment under test (EUT). The distortion signals are usually generated or picked up inside of the EUT and the mains cord acts as an antenna. European and international EMC regulations define maximum permissible signal levels and frequency bands for such distortion signals.
The distortion signal to be measured is available on a coaxial N‑connector that is mounted on the front panel of the NNB. For the actual measurement of the distortion signals a measuring receiver can be used. The V-network is part of a complex EMC-test setup that also has been standardised in CISPR 16‑2‑1 (EN 55016-2-1). The NNB is defined in CISPR 16-1-2. The NNB 51/52 are the replacements of the NNB 41/42 and offers now more remote flexibility and ground connections.