Orolia Seven Solutions WR-ZEN Series, User Manual

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Stratum 4 and below: Devices that announce this level should only be used for
cross-validation or backup but not as the primary NTP reference to synchronize a
3rd party device.
Stratum 15: It is the last valid stratum level defined by the NTP protocol.
Stratum 16: It is commonly used to indicate that the device is not synchronized and
thus does not provide any valid NTP time.
5.7 Holdover
The WR-Z16 can be ordered with an optional holdover oscillator (OCXO) in order to
ensure an accuracy of 1.5µs even after 24 hours.
If this holdover oscillator is detected, it will be automatically enabled as a timing source.
Otherwise, when UNAVAILABLE, the device will announce itself directly as Free-running
with UNKNOWN accuracy.
When the holdover is detected and enabled it can go through the following states:
1. Locking: During a minimum amount of time the holdover needs to perform a rough
and quick learning on a stable clock reference before using it.
2.
Learning: In order to maintains the best accuracy during enough time the holdover
is learning about its environment using adaptative algorithms. This learning period
has been set to 3 days in order to ensure to fulfill the accuracy specifications.
If the holdover is triggered before this learning time, it will directly enter the
expired state.
3.
Ready: Once the HO has learned enough time to ensure good performance, the HO
will be ready to be triggered at any moment (it will continue learning to slightly
improve its performance).
4. Activated: The holdover has been triggered (by trigger_origin) and it is actually
being the active timing source of the device. The clock info will be modified accord-
ingly and announced to the timing network.
5.
Expired: Reaching the holdover expired state means that the device announce itself
with a Free-Running clock_class and a clock_accuracy to UNKNOWN. This also
means that the corresponding VSC code is CRITCAL and thus if a better timing
source is detected it will switch to this one. Worth mentioning that during the
expired state, the holdover timing source is using the OCXO oscillator that provides
better performance than the internal onboard oscillator.
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WR-Z16 User Manual Rev. v3.4
5.7 Holdover