The Gnss Reference - Spectracom PRISMA VelaSync User Manual

Since "Local System" cannot be both Time , and 1PPS input together, in this example the GNSS
input will be set as the 1PPS reference (other use cases may require using different references,
e.g. IRIG.)
As there is no default entry for "Local System" and "GPS", a new entry needs to be added to
the Reference Priorities table in order to use this combination of references.
Step-by-step procedure:
1.
2.
3.
3.3.2 The GNSS Reference
With most applications, VelaSync will be setup such that it utilizes a GNSS signal as the
primary (if not the only) timing reference.
VelaSync's GNSS receiver utilizes the signal provided by the GNSS antenna.
The GNSS receiver analyzes the incoming GNSS data stream and supplies the GNSS time and
1PPS (Pulse-Per-Second) signal to VelaSync's timing system. The timing system uses the data to
control the System Time and discipline the oscillator.
While VelaSync's default GNSS receiver configuration will likely be adequate for most applic-
ations, it is advisable that you review the options and change settings as needed, particularly if
you are experiencing poor signal reception.
CHAPTER •
3 VelaSync User's Manual Rev. 1
Add a reference to the Reference Priority by clicking the PLUS icon. Use the following set-
tings, then click Submit :
In the Priority Level text box, enter 1 . This will give this reference the highest pri-
ority.
In the Time field, select "Local System".
In the PPS field, select "GPS".
Check the Enabled checkbox.
Confirm that the first reference in the Reference Priority table has "Local System" as the
Time input and "GNSS" as the 1PPS input.
After a power cycle or reboot, as soon as GNSS is declared valid, the System Time will
automatically be used as-is, with no manual intervention required.
3.3 Managing References
113