HP 54600B User's And Service Manual page 57

Operating Your Oscilloscope
To reduce the random noise on a signal
Use averaging to reduce noise on the displayed waveform.
3
To use averaging follow these steps.
Figure 2–22
On this waveform, 256 averages were used to reduce the noise
2–30
Press , the press the Average softkey.
Display
Notice that Av appears in the status line.
Toggle the # Average softkey to select the number of averages that best
eliminates the noise from the displayed waveform.
The Av initials in the status line indicates how much of the averaging
process is finished, by turning to inverse video as the oscilloscope
performs averaging. The higher the number of averages, the more
noise that is removed from the display. However, the higher the
number of averages, the slower the displayed waveform responds to
waveform changes. You need to choose between how quickly the
waveform responds to changes and how much noise there is on the
signal.