HP 81101A Reference Manual page 109

Jitter
Short-term instability of one edge relative to a reference edge. Usually
specified as rms value, which is one standard deviation or "sigma". If
distribution is assumed Gaussian, six sigma represents 99.74% of the
peak-peak jitter.
The reference edge for period jitter is the previous leading edge. That for
delay jitter is the leading edge of the trigger output. Width jitter is the
stability of the trailing edge with regard to the leading edge.
Stability
Long-term average instability over a specific time, for example, hour,
year. Jitter is excluded.
Pulse Levels
Pulse output is specified as pulse top and pulse base (usually referred to
as high level and low level), or as peak to peak amplitude and median
offset. A "window" specification shows the limits within which the pulse
can be positioned.
High Level
Amplitude
Low Level
Zero Volts
Pulse Parameter Definitions
Median
Window
Offset
Specifications
Max
High
Level
Min
Low
Level
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