Safran SecureSync 2400 User Manual page 227

3.3 Managing References
See also below, "How long will the User/User reference be valid?": The notion of
limiting the validity of the User/User reference also serves as a safety feature.
How long will the User/User reference be valid?
Since the User/User reference does not qualify as a legitimate, traceable time, it
becomes invalid once SecureSync is reset, or power-cycles, or after the Holdover
Time expires (whichever occurs first). It then needs to be set manually and sub-
mitted again (Edit System Time > Manual Time Set).
The only workaround for this is "Using Battery Backed Time on Startup" on
page 193. This will allow SecureSync to apply the User/User reference after a
power-cycle without manual intervention.
How to setup the User/User Reference
See "Manually Setting the Time" on page 191.
Using the "User" Reference with Other References
If the User/User reference is used in conjunction with other, external references
(such as GNSS or IRIG), the System Time should be set as accurately as possible:
Otherwise, the large time correction that needs to be bridged when switching
from a lost reference to a valid reference, or from a valid reference to a higher-pri-
ority reference that has become available again, will cause NTP to exit syn-
chronization. If the difference is under 1 second, NTP will remain in sync and will
"slew" (over a period of time) to the new reference time.
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