Keysight Technologies RP7931A Guide D'utilisation Et D'entretien page 76

2 Installing the Instrument
Ferrite Core Installation - for earlier RP7961A, RP7962A, RP7963A models
For 400/480 VAC input units that have hex-nut
terminal connections (not bolts), install a ferrite
core (p/n 9170-2578) to reduce RFI interference.
Place the core as close as possible to the input
cover as shown.
Place a tie-wrap behind the core to prevent it
from sliding down the power cord.
76 Keysight RP7900 Series Operating and Service Guide