GPS7 GPS Synchronization and Timecode modu le
Notes about SMP
TE309 data usage. If ST309 data is not present on the selected
time reference, then the default SMPTE309 Data mode setting of “Ignore” is the
correct selection. For most applications in which the input time reference does
have the ST309 data, then the setting of “Input” is usually the best choice. While
in “Input” mode, the time zone and DST programming on the input and output a re
independent, with the input set by the ST309 data on the input and the outputs
being set by
the menu in the instrument. This is the best mode of operation even if
all units are set to the same time zone and DST values.
When the SM
PTE309 Data mode is set to “Ignore,” you cannot use the Time Zone
Offset or DST offset controls on the s lave unit to adjust the time code outputs.
The reason for this is that the slave unit assumes that the VITC/LTC inputs are
local time and already have such corrections applied. However, you can offset
the time code on individual outputs using the offset controls for each output. The
local time zone and DST settings do affect the master time-of-day since the offsets
are subt
racted from the input and added to the output, but the net effect is that the
outputs match the inputs unless individually offset.
SMPTE3
09 time zone offset data on individual outputs is not affected by adjusting
time code offsets on individual outputs. The time code offset controls on the
individual outputs does not affect the time zone offset fields in the output time code
data. For example, if the slave unit is configured with a time zone offset of –08:00
and then you also adjust the time code offset on the SDI7 module Channel 1 by
another +03:00 hours, the SMPTE309 data on that output w ill still read –08:00 in
the t
ime zone offset field even though the actual output is UTC –05:00 hours.
Many installations use multiple instruments configured in a master/slave
rel
ationship (for example, when sending signals across time zones). In these
instances, if the master instrument is locked to a GPS/GLONASS signal, is
running in Internal mode, or is genlocked to a source without ST309 data, the
SMPTE309 Data mode on the master instrument should be set to “Ignore.” If the
master instrument is locked to a source providing ST309 data, the SMPTE309
Data mode on the master instrument should be set to “Input” and on the slave
i
nstrument the mode should be set to “Input.”
The DST scheduler system a pplies the DST offset even if the Time-Of-Day
(TOD) source is set to “VITC Input” or “LTC Input” and the SMPTE309 mode is
set to “Ignore” or “Use As Input.” In these cases, the offset is applied whether or
not a valid VITC or LTC input signal is available. For proper DST scheduling,
you need to ensure that the instrument has valid time information and manually
enter the correct time of day if the system is not synchronized to an accurate
time of day source.
The GPS7 module Black outputs (when VITC is enabled) and the LTC outputs
always have the SMPTE309 date, time-zone offset, and DST enabled/disabled
fields included. The content of these fields depends on the current SMPTE309
mode setting (Ignore, Use As Input, or Use As Input/Output).
3–136 TG8000 Multiformat Test Signal Generator User Manual
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