Orolia Spectracom VelaSync 1232, User Manual

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When the Time reference is configured as Local System , VelaSync's System Time
is considered a valid reference, as long as the external 1PPS input reference is valid.
Vice versa, when the 1PPS reference is configured as Local System , VelaSync's
built-in oscillator is considered a valid reference, as long as the external Time ref-
erence is valid.
Use case "Local System Time"
The Local System reference when used for Time allows VelaSync to operate using its cur-
rent Time-of-Day (ToD) for Time, while synchronized to an external 1PPS reference.
While you may intentionally offset the time in this scenario, the second will be precisely
aligned to the external 1PPS reference. Therefore, this use case qualifies as a legitimate,
traceable time source.
Instead of an offset time, Local System can also be used as a backup Time reference (e.g.,
Priority "2"): Should the external Time reference become invalid, the Local System Time
will become the valid backup reference, disciplined by the external 1PPS reference:
VelaSync will transition to the
Local System Time, without going into Holdover.
Use case "Local System 1PPS"
The Local System reference can also be used for 1PPS : This allows VelaSync to operate
using an external ToD for time, while generating 1PPS from its own internal oscillator.
In this rare use case the 1PPS is NOT aligned to any standard, therefore the time may drift,
and must be considered untraceable.
3.3.1.3 The "User/User" Reference
While it is normally not required, it is possible for you as the "User" to override the System
Time (even if it is synchronized to a valid reference) with a manually set time, steered by
an undisciplined oscillator, and use this manually set Time as an output reference. This
concept is referred to as the
User/User reference, because both the Time, and the 1PPS
reference are not linked to any UTC-based external reference, but hand-set by you.
Caution: Since the User/User reference is not traceable to a valid ref-
erence, it does not qualify as a legitimate time source. Operating VelaSync
with a manually set
User time bears the risk of inadvertently outputting an
illegitimate System Time thought to be a valid reference time.
Use cases for the "User/User" reference
The User/User reference is provided for the following use cases:
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3.3 Managing References