M e r i d i a n I I U s e r M a n u a l
120
C H A P T E R T E N
121
M e r i d i a n I I U s e r M a n u a l
R E A R - P A N E L I / O
Alarms
Minor, Major and Critical Alarms are defined below. For further information on each fault refer to
the
gpsstat
command (FLTS field) in
Chapter 3 - Control and Status Commands
. In addition to
the fault types listed below, there will be a Critical Alarm if a serious hardware problem is detected
on the Telecom Module or the Receiver/CPU Module.
Fault Type
Critical
Major
Minor
DAC Control Over-Range
X
No Signal Time-Out
X
FPGA Configuration Fault
X
FLASH Write Fault
X
GPS Comm Fault
X
Time Input Fault
X
No Polling Events
X
Antenna Fault
X
Power A Fault (option)
X
Power B Fault (option)
X
MTIE Exceeds 1 Microsecond*
X
*The first 10 faults listed above are standard system faults. When the telecom board is installed, an
additional fault detection algorithm is active that compares the worst case holdover accuracy to the
telecom industry standard jitter/wander performance masks. This is the last fault listed in the table
above (MTIE Exceeds 1 Microsecond).
The following chart shows the G.823 and T1.101 jitter/wander MTIE mask levels that are pertinent
to the telecom option module. In addition, it shows the specified worst case accumulated time error,
while in holdover, for the various oscillator options that can be installed with the telecom option.
Since the one microsecond level is a good approximate level to the various masks, it is also the
threshold level that will induce an immediate fault on the telecom option alarm relays and SSM bits.
This level is factory configured and not user settable.
If Meridian II loses GPS signal lock then it will drift at a rate dependent upon the installed oscillator.
When it has drifted more than 1 microsecond the MTIE fault will be set and a Major Alarm will oc-
cur. The list below summarizes the chart data. It shows how long in holdover each oscillator will be
until it exceeds the one microsecond threshold:
Medium-Stability OCXO: 1 hour
High-Stability OCXO:
3 hours
Ultra-Stable OCXO:
6 hours
Rubidium:
6 hours
Ultra-Stable Rubidium:
1 day
Summary of Contents for Meridian II
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