DXD/PTP/GPS User Manual (rev 2.10)
Page 11
9. Time Menus
9.1 TIME STANDARDS (MENU 7.1)
The following time standards are available on the DXD-8 in addition to the local time:
•
TAI
: International Atomic Time, an atomic coordinated time that has been measuring time continuously since 1955 with
no leap seconds. It is used as a base by other standards such as UTC.
•
UTC
: Coordinated Universal Time is the time zone ‘0’ from which all other time zones are calculated. It is based on
TAI and since 1972 has had leap seconds every year or so, depending on the earth’s rotation.
•
GPS
: Global Positioning System time is used by the atomic clocks in the GPS satellites. It is continuous time (no leap
seconds) measured from the GPS time zero point of midnight January 5, 1980. It is 19 seconds behind TAI.
•
Loran
: Long Range Navigation time based on atomic clocks. Like GPS, it is continuous time with no leap seconds
measured from the time zero point of midnight January 1st, 1958.
•
Local
: Local time is based on UTC and can have adjustments for time zone and Daylight Saving (menu 7.1).
Menu 7.1 lets you pick which of these time standards will be used to display the following DXD times:
•
System Time
, the main Time Of Day clock at the heart of the DXD
•
RTC
, Real Time Clock, a constantly running, battery-backed-up clock inside the DXD
•
Grandmaster
, time received on the Ethernet port from the PTP Grandmaster
•
GPS
, time received from the GPS receiver (
optional
)
To avoid confusion, it is recommended to use one standard for all DXD times. The default value is TAI. But some users may
prefer to use Local Time instead while others may even prefer different standards for different times.
Be aware that, even though the time source may give Time Of Day, it may not correspond to the time indicated on a
wall clock as it would depend on the standard used or even on the accuracy and settings of the source time.
There are 2 other Local Time parameters in menu 7.1:
•
Time Zone
: can be adjusted in hours and minutes with a positive or
negative value, relative to UTC (or GMT)
•
Daylight Saving
: can be adjusted in hours and minutes (typically 1 hr).
DST can only be set manually.
At the bottom of this page a ‘hint’ message appears for setting the time zone
properly: NY -5, Tokyo +9.
9.2 REAL TIME CLOCK (MENU 7.2)
Menu 7.2 lets you set several parameters of the RTC (Real Time Clock), the DXD internal back up clock described in chapter 8
above.
•
Set Time: YYYY/MM/DD
and
HH:MM:SS
: These fields let you enter manually a date and a time that will become
the current date and time of the RTC when the [
ENTER
] key is pressed.
•
System Time Jam From RT Clock
: With ‘Press ENTER to Jam’ selected, the Main TOD Clock (System Time) will
Jam from the internal RTC Time when the [
ENTER
] key is pressed.
Note that depending on the offset between the 2 clocks, this action will most certainly create a certain amount of
‘sync shock’ as all the outputs are locked to the System Time.
•
Auto Update RT Clock
: 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 when the feature is turned on, then every 1.2 hr. Options
are “From GPS” or “Off”.
This field does not appear if the DXD/GPS card is not installed.
At the bottom of this page the RTC Time is displayed along with the Time Standard set up in menu 7.1
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