Spectracom SecureSync User Reference Manual page 182

3.6 OTHER Setup Pages
The System Timescale is configured through the MANAGEMENT/OTHER/Time Management
page.
Some of the available SecureSync inputs (such as the IRIG option module's input, ASCII data
module's inputs, etc.) won't necessarily provide time to SecureSync in the same timescale selec-
ted 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 configured 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 times-
cale offset value in order for the time on the output reference to be correct. 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 Man-
agement page. See also "System Time" on page 164.
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.
Some of the available SecureSync outputs (such as the front panel LED display, the IRIG option
module's outputs, ASCII data module's outputs, etc.) won't necessarily output in the same times-
cale 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
166
NOTE – UTC Timescale is also referred to as "ZULU" time. GPS timescale is the
raw GPS time as transmitted by the GNSS satellites (as of September, 2013, GPS
time is currently 16 seconds ahead of UTC time. UTC timescale observes leap
seconds while GPS timescale does not).
NOTE – The TAI timescale also does not observe leap seconds. The TAI timescale
is fixed to always be 19 seconds ahead of GPS time. As of July, 2015, TAI time is
36 seconds ahead of UTC.
NOTE – If the System Time is set to the UTC timescale, and all output references
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!
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3 SecureSync User Reference Guide Rev. 18