Technical data

Installation & Operation Manual GM-TTT
Page 65
5.5 Time Transfer During Normal Operation and Time
Jumps
In the time operating mode, the GM-TTT generates a “real-time“ time code and receives data
from a reference clock. Which of the systems is the "master" and how “wrong“ or “real“ time
jumps are treated, is explained as follows.
“Wrong“ Time Jupms:
Generally, only a reasonable time and a reasonable date are accepted by the reference clock.
Any wrong time jumps might be caused by an interference of the serial interface or a mal-
function of the reference clock. The selection of the operating mode in the REFER - MODE 1
menu now determines that the reference clock or the GM-TTT will be the time master.
• If the reference time is adopted every second, no further check is performed, in this case
the GM-TTT will always follow the reference clock.
• If the automatic DST mode of the internal clock of the GM-TTT is switched off, the
reference clock is rather used as the master. In this case the time is only checked for an
up-counting sequence without any time jump.
• If the automatic DST mode of the internal clock of the GM-TTT is switched on, this
determines that the GM-TTT is principally always generating a valid time and can only be
synchronised to the reference clock in the seconds range. The received time is only
accepted, if it is an up-counting sequence without any time jump and if the hours and
minutes are coincident with the internal clock of the GM-TTT (taking the offset into
account). Exception: A DST switchover or a leap second were correctly announced and
carried out by the reference clock.
“Real“ Time Jumps:
Twice a year, a DST switchover generates a time jump of one hour, additionally seconds
jumps may be generated by inserting a leap second (for adaptation of time to the rotation of
the earth) once or twice a year. If the time code is generated in-sync with the video signal and
the sync generator is not synchronised to the real time reference, a frame jump may be
generated in addition to the above-mentioned time jumps whenever the internal clock is set by
the reference time.
The use of real time for the time code has to be discussed in the system context. Problems may
occur in systems requiring a continuous time code. These time jumps are real, and any auto-
matic setting which will inevitably lead to time code jumps should only be activated, if this does
not result in any system failures. This decision depends upon the following conditions:
1. Priority is given to the precise “real time“ of the time code.
2. Priority is given to a continuous time code without any frame jumps.
3. Both conditions shall be achieved.
As for 1. and 2., the GM-TTT offers to program the automatic setting: the reference sets the
time into the time code in intervals of seconds, days, weeks, months, years, after the start/end
of DST or after a leap second. After the start/end of DST and after a leap second, the time is
only transferred, if an announcement occurred within one hour before the event. The daily/-
monthly/yearly time transfers may be coupled to the synchronisation of the receiver clock.