Reference Priorities: Examples - Spectracom VersaSync User Manual

3.3 Managing References
The only workaround for this is "Using Battery Backed Time on Startup" on page 120. This will
allow VersaSync to apply the User/User reference after a power-cycle without manual inter-
vention.
How to setup the User/User Reference
See "Manually Setting the Time" on page 118.
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 ref-
erence to a valid reference, or from a valid reference to a higher-priority reference that has
become available again, will cause NTP to exit synchronization. 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.
3.3.1.4

Reference Priorities: EXAMPLES

Example 1 – GNSS as primary reference, IRIG as backup:
In this use case, the objective is to use:
GNSS as the primary Time, and 1PPS reference
IRIG as the backup Time, and 1PPS reference.
Step-by-step procedure:
1.
Move the reference which has "GPS 0" in the Time column and "GPS 0" in the 1PPS
column to the top of the table, with a Priority value of 1. Click the Enabled checkbox.
2.
Move the reference which has "GPS 0" in the Time column and "GPS 0" in the 1PPS
column to the top of the table, with a Priority value of 1. Click the Enabled checkbox.
3.
Move the reference which has "GPS 0" in the Time column and "GPS 0" in the 1PPS
column to the top of the table, with a Priority value of 1. Click the Enabled checkbox.
Since both of these references are
added to the Reference Priority table.
Example 2 – IRIG as primary reference, NTP input as backup
In this use case, the objective is to use:
IRIG as the primary reference input
Another NTP server as backup reference
136
default
references, no additional references need to be
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VersaSync User Manual Rev. 6.0