Spectracom NetClock 9400 Series, Руководство пользователя

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Vice versa, when the 1PPS reference is configured as Local System , NetClock's built-in
oscillator is considered a valid reference, as long as the external Time reference is valid.
Use case "Local System Time"
The Local System reference when used for Time allows NetClock to operate using its current
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., Pri
ority "2"): Should the external Time reference become invalid, the Local System Time will
become the valid backup reference, disciplined by the external 1PPS reference: NetClock 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 NetClock 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 reference, it
does not qualify as a legitimate time source. Operating NetClock 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:
a.
No external references are available (yet), but you need a reference for testing or setup
purposes. This may be the case e.g., while waiting for a GNSS antenna to be installed.
b.
No external references are required e.g., if NetClock is used solely to synchronize com
puters on a network, with no need for traceable UTC-based timing.
3.3 Managing Input References
CHAPTER
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