Technical data

Installation & Operation Manual GM-TTT
Page 67
5.6 Internal Clock, Automatic DST mode, Binary
Groups with Date and Status
The GM-TTT has an internal clock which counts time and date. The start value after power-on
is 00:00:00:00 and 01.01.2002. The clock is set manually (SET - ... - TIME, SET - ... - DATE)
or by a reference. The time zone of the internal clock is either normal time or DST. Start and
end of a DST is calculated from the input values for the day of the week, week of the month
and month within the validity range 01.01.1998 - 31.12.2097 - see ZONE menu. Time zone
calculation is also carried out every time a new date or hour was set. Any time zone switchover
occurs with the next hour following an announcement.
The automatic DST mode is selected in the REFER - MODE 1 menu.
The automatic DST mode permits to switch over the time zone even in case of an interference
during reception of the reference time, so that the time code remains precise. It is also possible
to use external reception of UTC and generate a random time zone by using offsets. Example
for CET/CEST: Offset 1 = +01, Offset 2 = +02.
If date and status bits are transferred in the binary groups (i.e. USER MODE = 3 STATUS),
external equipment (such as TC60CLS) can precisely receive the “real time“ and the time
zones.
The date corresponds to the date of the internal clock.
The BG7.0 status bit is set to 1, if the reference status shows "lock" when time is adopted from
a reference. The bit remains set for about 24 hours; if the internal clock is not set again in the
"lock" status, it is reset to 0 to indicate that the time code is in free-run.
The BG7.1 and BG7.2 status bits show the current time zone of the internal clock. The time
zone is set to UTC, if the reference supplies UTC and the automatic DST mode of the internal
clock is not activated.
The BG7.3 status bit announces the start/end of DST. When the automatic DST mode is
activated, it is set exactly one hour before the switchover. With the automatic DST mode
switched off, it is transferred from the serial data of the reference after the data have been
checked (i.e. with a delay of about 4 to 5 minutes) - even when the time is not transferred to
the time code.
The BG8.0 status bit announces a leap second. This bit is only set by the serial data of the
reference - in analogy with the BG7.3 status bit.