80 SyncServer 600 Series User’s Guide 098-00720-000 Revision D1 – February, 2018
Chapter 4
Status / Information Windows
Holdover Same as prior row but specific additional
conditions are met.
This condition occurs if the current
source is the internal oscillator and the
duration in time holdover has exceeded
the time defined by user in the Timing >
Holdover window.
The unit has been in holdover
for more than a user-specified
duration and the holdover is
based on the SyncServer
internal reference.
In this case the Holdover
Sources row will not contain any
green items.
Relocking SyncServer has selected a qualified
active time input for use and is now in
process of aligning all outputs to it.
1
The main purpose of holdover is to allow the S6xx time server to continue to operate as "normal" using the
internal oscillator or external frequency reference even though the connection the GNSS is lost. The user
defines how long this holdover period will last. During this time the NTP Reference Time Stamp is updated
regularly indicating the S6xx is still connected to a time reference. Once the user defined holdover period is
exceeded the reference time stamp is no longer updated. This is important information to provide to NTP
clients as they can then determine whether or not to continue to synchronize to the S6xx. Once the S6xx
reacquires GNSS and relocks, the NTP Reference Time Stamp will again be updated regularly.
By NTP protocol definition, once an NTP server locks to a time reference and sets the Leap Indicator to 00
from 11 it never returns to 11. In other words, once the unit has left stratum 16 it should never return to
stratum 16. Instead it uses the reference time stamp behavior mentioned above.
Table 4-2. Status - Clock State Descriptions (Continued)
Status Indication Meaning Details
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