EndRun Sonoma D12, Руководство пользователя

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S o n o m a U s e r M a n u a l 111
"Smarter Timing Solutions"
Appendix
A
Time Figure of Merit (TFOM)
This appendix describes the Time Figure of Merit number. The TFOM number indicates the level of
accuracy that should be included in the interpretation of the time-of-day and ranges from 6 to 9:
6 time error is < 100 us
7 time error is < 1 ms
8 time error is < 10 ms
9 time error is > 10 ms, unsynchronized state if never locked to CDMA
In all cases, the Sonoma reports this value as accurately as possible, even during periods of CDMA
signal outage where the Sonoma is unable to directly measure the relationship of its timing outputs
to UTC. During these CDMA outage periods, assuming that the Sonoma had been synchronized
prior to the outage, the Sonoma extrapolates the expected drift of the Sonoma timing signals based
on its knowledge of the characteristics of the system oscillator - either the Temperature Compensated
Crystal Oscillator (TCXO), Oven Controlled Crystal Oscillator (OCXO) or Rubidium oscillator.
The extrapolated TFOM is based on a conservative estimate of the performance of the oscillator and
should be considered ‘worst case’ for a typical benign ambient temperature environment.
Due to this extrapolation behavior, after initial synchronization, brief periods without CDMA signal
reception will not induce an immediate alarm condition. If the condition persists for long enough pe-
riods, you should see the TFOM character change to indicate a gradually deteriorating accuracy of the
timing outputs. If the signal loss condition persists longer, then the final, unsynchronized state will
eventually be reached. If the Sonoma is unable to re-synchronize within one hour after reaching this
state, the Alarm LED will light and the
faultstat
command will show a No Signal Time-Out fault.
If the CDMA Subsystem reaches the unsynchronized TFOM state, the NTP daemon will cease to use
the timing information returned by the CDMA Subsystem in its polling event timestamps. At this
point, the NTP daemon will report in its replies to network NTP clients that it is running at stratum 16
and the leap indicator bits will be set to the fault state. NTP clients will recognize that and cease to
use the unsynchronized server.