Note: The TAI timescale also does not observe leap seconds. The TAI times-
cale is fixed to always be 19 seconds ahead of GPS time. As of 15-February-
2021 TAI time is 37 seconds ahead of UTC.
SecureSync's System timescale is configured via the MANAGEMENT > OTHER: Time
Management screen, see "System Time" on page168.
Input timescales
Some of the inputs may not necessarily provide time to SecureSync in the same timescale
selected in the System Time’s timescale field. These inputs have internal conversions that
allow the timescale for the inputs to also be independently defined, so that they don’t have
to be provided in the same timescale. For example, the System timescale can be con-
figured as “UTC”, but the IRIG input data stream can provide SecureSync with “local” time,
with no time jumps occurring when the reference is selected.
If an output reference is using the GPS or TAI timescale, and the System Time is set to
“UTC”, then the GPS Offset box in the Edit GPS Offset window must be populated with
the proper timescale offset value in order for the time on the output reference to be cor-
rect. Some references (like GNSS) provide the timescale offset to the system. In the event
that the input reference being used does not provide this information, it must be set in
through the Offsets panel of the Time Management page.
Since the GPS and TAI offsets have a fixed relationship, only the GPS offset can be set. If
only the TAI offset is known, subtract 19 from it to get the GPS offset.
Note: If the System Time is set to the UTC timescale, and all output ref-
erences either use the UTC or “local” timescale, then it is not necessary to
set the GPS and TAI timescale Offsets.
Caution: It is imperative to configure any input reference’s timescales
appropriately. Otherwise, a System Time error may occur!
Output timescales
Some of the available SecureSync outputs (such as the ASCII data module’s outputs, etc.)
won’t necessarily output in the same timescale selected in the System Time’s timescale
field. These outputs have internal conversions that allow the timescale for the outputs to
also be independently defined, so that they don’t have to be provided in the same times-
cale.
170
CHAPTER 3 • SecureSync 2400 User Manual Rev. 2
3.2 System Time
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