The LF-R 400 is a passive near-field probe. With its large tip diameter (25 mm), it is more sensitive and thus is able to detect a greater area of the magnetic field than the LF-R 50 (10 mm) or LF-R 3 (3 mm) near-field probes, which both have higher resolutions than the LF-R 400. This probe is small and handy. It has a current attenuating sheath and, therefore, is electrically shielded. It can be connected to a spectrum analyzer or an oscilloscope with a 50 Ω input. The H-field probe does not have an internal terminating resistance of 50 Ω.