Spectracom NetClock 9400 Series, User Reference Manual

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On the left side of the screen, Status information is displayed for the System and the
References. Note that the Reference Status panel also displays the latest PHASE OFFSET
reading (1) for active references against the System Ontime Point. The reading is
updated every 30 seconds.
This Reference Phase Offset Data is plotted over time (abscissa) in the Reference Monitor
panel in the center of the screen. Use the check boxes in the References panel (2) to
select the reference(s) for which you want to plot the phase offset data. Use the handles
(3) to zoom in on a time window.
The scale of the axis of ordinate (4) is determined by the largest amplitude of any of the
references displayed in the current time window. Use the checkboxes in the References
panel on the right to remove references from the graph, or add them to it.
3.3.2.2 Smart Reference Monitoring
Spectracom's Smart Reference Monitoring uses phase error validation in combination with
automatic failover :
The phase error validation calculates long-term averages and standard deviations of the phase
offset between the monitored external reference and the internal system reference. The standard
deviation is used to calculate two validity thresholds, a higher and a lower one (the latter acts
as a hysteresis buffer, preventing the status flip/flopping if the actual phase error validation
value varies closely around the outer threshold). The thresholds are not user-configurable.
If the higher threshold value is exceeded, the automatic failover will cause NetClock to fall
back to its next lower reference (if available).
If no other reference is found, the unit will transition into a 1200-second coasting period. Dur
ing this coasting period, the TIME and 1PPS references will continue to be considered valid, but
NetClock's oscillator will flywheel. Note that the
PPS reference status light will turn yellow. After
expiration of the 1200 seconds the unit will transition into Holdover.
3.3 Managing Input References
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