HP 70427A User Manual page 263

Softkeys and Displays
0 PM/V default
0 PM/V default
This softkey disables front-panel tuning of the reference chain. The
100 MHz oscillator is locked to the 10 MHz reference and the 600 MHz
oscillator is locked to the 100 MHz oscillator.
Select this sensitivity for applications requiring the lowest possible noise at
all offsets ≤ and where external tuning is not needed.
Path
Ref Chain Tune Sense 0 PM/V default
HP-IB command
REF:TS 0
Figure 10-19 Reference Chain
10-20 HP 70427A/HP 70428A User's Guide