Spectracom Corporation
Model 9289
NetClock/NTP Network Time Provider Instruction Manual
3-55
Oscillator
Option
Estimated Error Rates
Time to reach 2 ms
TCXO
Standard
1.0 milliseconds / hour (nominal)
2 hours (typical)
TCXO
Standard
7.2 milliseconds / hour (worst case)
17 minutes
Table 3-3: Estimated TCXO Oscillator Error Rates
NOTE:
The TCXO Error rate is a worst-case estimate and not typically this value. The
nominal value assumed has been 1 millisecond / hour yielding 2 hours holdover times.
The TCXO does not estimate error for holdover. Typically, the error rates for a
disciplined oscillator at 25 degrees Celsius will be lower than these values.
Limits on the minimum and maximum length of allowable holdover have been placed on the
oscillator as shown below in Table 3-4.
Oscillator Minimum Length
Maximum Length
TCXO
15 minutes
24 hours
Table 3-4: Minimum and Maximum Allowable Holdover Values
If the user sets the length below or above the limits or if the error is too small or large, the
NetClock will notify the user that this setting is outside its allowable parameters.
If the unit is currently in sync, the changes will take effect immediately. If the unit is in holdover,
the changes will not take effect until the next holdover. To force the changes to take effect
immediately, reboot the NetClock.
Time in Holdover
displays either the amount of time that the NetClock has been in the holdover
mode, or displays a phrase that the unit is not currently in the holdover mode. If the unit is
currently in the holdover mode (Lost external reference but the unit is still “synchronized”), this
field will show the number of days, hours, minutes and seconds that the unit has been in the
holdover mode (Elapsed time from the last good external reference).
If the unit is not currently in holdover mode because it either currently receiving an external
reference or because the variable holdover period has expired and the unit is no longer
“synchronized”, the phrase "Not In Holdover" is displayed instead.
Summary of Contents for 9289
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