Returns global RTC table.

        Creates the table if it does not exist.

def get_rtc_table(self):
        """Returns global RTC table.

        Creates the table if it does not exist.
        """
        rtc_table = self._global_tables.get(RF_RTC_UC)
        # Lazy initialization of the table.
        if not rtc_table:
            rtc_table = RtcTable(self._core_service, self._signal_bus)
            self._global_tables[RF_RTC_UC] = rtc_table
            self._tables[(None, RF_RTC_UC)] = rtc_table
        return rtc_table