Microsemi SyncServer S350i, Руководство пользователя

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Distributing GPS Time
5. On the
SERVICES - Startup page, under System Control , select Reboot and click the
APPLY button.
6. (Optional) After the SyncServer restarts, compare the seconds on the front panel time dis-
play with some other accurate time display. The GPS time should be ahead of the UTC
or standard time display by the value of the GPS-UTC Offset.
CAUTION: NTP time is based on the UTC time scale. Distributing GPS time over NTP is
non-standard and can have serious consequences for systems that are synchronized to UTC.
This action should only be performed by a person who is knowledgable and authorized to do
so.
About distributing GPS Time
Network Time Protocol (NTP) is based on UTC. However, some users distribute GPS time
over NTP to avoid leap second adjustments. This is a non-standard practice, and should not
be undertaken without a comprehensive understanding of the effects that it can have on a
timing network.
Coordinated Universal Time (UTC) is a discontinuous atomic time scale that is the basis for
civil timekeeping around the world. Leap second adjustments are periodically applied to UTC
so that it remains consistent with Earth's rotational time, which is variable and gradually slow-
ing.
The Global Positioning System time (GPS time) is a continuous atomic time scale that does
not include leap second adjustments. GPS time was synchronized to UTC at the beginning
of the GPS epoch, on January 6th, 1980. The two time scales "tick" at the same rate, but are
different by the number of leap seconds that have been applied to UTC since that date. This
difference is known as the
GPS-UTC Offset . As of January 1st, 2006, the offset from GPS to
UTC was -14 seconds. This difference will continue to change and probably grow as future
leap second adjustments are applied to UTC.
To generate UTC, the SyncServer gets the GPS-UTC Offset from the GPS navigation mes-
sage and applies it to the GPS time. To generate GPS time, the SyncServer stops applying
the GPS-UTC Offset, and uses unchanged GPS time.
Configuring the SyncServer to use GPS time affects ALL of the SyncServer's timing outputs,
including:
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The IRIG output
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The Sysplex output
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The NTP, SNTP, Time, and DAYTIME protocol outputs on the network ports
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The web user interface
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The front panel time display
Notes:
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While configured to distribute GPS time, the SyncServer does not report Leap Indicator
status or perform leap second adjustments.
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Regardless of the time zone setting, GPS time is reflected by the seconds in the time dis-
play.
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