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Page 8
7.2 TIME JAM
The BNC inputs can accept Word Clock, AES, Video Sync or 10 MHz. As none of those signals has date and time information,
when one is selected as reference, the DXD can be set to receive time information from another source (menu 1.2). Current
choices are PTP and GPS. This takes place as a Time Jam since the DXD can only lock to one reference at one time, meaning
that the DXD's System Time will be reset to the time-of-day of the master source before locking to the BNC input.
Time Jam To GPS
With the DXD/GPS option installed, GPS can be selected as a source for a Time Jam in menu 1.2. See chapter 6 above for
more information.
8. Time Menus
8.1 TIME STANDARDS (MENU 7.1)
The following time standards are available on the DXD in addition to the local time:
• TAI: International Atomic Time, (used as a base by other standards such as UTC - no leap seconds).
• UTC: Coordinated Universal Time (time zone '0' - leap seconds).
• GPS: Global Positioning System time (no leap seconds - 19 sec behind TAI and currently 18 sec ahead of UTC).
• Loran: Long Range Navigation time (no leap seconds).
• Local: Local time is based on UTC and can have adjustments for time zone and Daylight Saving (menu 7.1).
With the DXD/GPS installed, menu 7.1 lets you pick which of these time standards will be used to display the time received
from the GPS receiver.
8.2 REAL TIME CLOCK (MENU 7.2)
Menu 7.2 includes several parameters of the RTC (Real Time Clock), the DXD internal back up
clock described in chapter 7 above.
GPS can be used to auto-update the RT Clock (see 7.1 above). When this function is turned on,
the RTC is automatically updated with the date & time information from GPS. This update occurs
within a second of activation, then every 1/2 hr. Choices are "From GPS" or "Off". At the
bottom of this page the RTC Time is displayed along with the Time Standard set up in menu 7.1
8.3 TIME & DATE DISPLAY (MENU 7.3)
In menu 7.3, 2 different DXD times & dates can be selected to be displayed in the Time & Date display (see 10.1.2 below). The
GPS Receiver is added to the list of choices.
The times and dates displayed will match what has been set in menu 7.1 and that setting will appear to the right of the time.
8.4 LEAP SECONDS (MENU 7.4)
Menu 7.4 is used to adjust the current number of leap seconds.
GPS can be used to auto-update that value.
• UTC Leap Second: Menu 7.4 is used to enter manually the number of leap seconds
to be applied to TAI.
• Auto Update: This fields only appears when the GPS receiver is installed and is used
to set the DXD so that the leap seconds will be updated automatically based on data
from GPS. Choices are "From GPS" or "Off".
DXD/GPS/OCXO User Manual (rev 2.10)
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