CHAPTER THREE
A sample of the MAIN MENU SCREEN is shown below:
Column:
1 5 10 15 20 25 30 35 40
| | | | | | | | |
123.25:59:59 U < DOING GPS CORRECTION >
FRQ:+5437E-12 PRN:03 12 15 21 MODE:D6
Row 1
Row 2
At power up, the type of oscillator installed in the unit and the software version appear on the
first row of the LCD display. The oscillator can be a TCXO, OCXO, LPRO, or X72 (LPRO and
X72 are Rubidium oscillators). The software version appears as DTxxxxxx, where DTxxxxxx is
the Operational Software Version.
The time-of-year is displayed in Row One, starting with Column One and consists of day-of-
year, hour, minute, and second. This can be UTC, or GPS time, or display the local time offset
depending on which mode has been selected via the RS-232 I/O port, or via the front panel LCD
and keyboard. For remote selection, see the paragraph titled “UTC Sync” to select UTC time
synchronization, and the paragraph titled “GPS Sync” to select GPS synchronization in Chapter
Four of this User’s Guide. For local selection, refer to the paragraph titled “Set Time,” under
SET-UP MENU SCREEN in this section, to select UTC or GPS synchronization using the front
panel LCD and keyboard. See paragraph titled “Enter Local Time Offset” in Chapter Four of
this User’s Guide to enter the desired local time offset via the RS-232 I/O port. The local time
offset may also be entered into the unit using the front panel keyboard and LCD. See paragraph
titled “Local Time Offset” under the SET-UP MENU SCREEN in this chapter.
The letter “U” or “G” which is displayed in Row One, Column Fourteen, denotes whether UTC
(U) or GPS (G) synchronization has been selected. An extra letter “L” is displayed next to the
letter “U” or “G” if the local time offset is not equal to zero. An “L” indicates that the time is
offset by a Local Time Offset.
When the GPS TC&FG is synchronized to UTC time, the time-of-year is displayed and the GPS
corrected 1pps output is on-time with UTC within ±125 nanoseconds with SA (Selective
Availability).
When the GPS TC&FG is synchronized to GPS time, there is a time difference between UTC
and GPS time. As of 9 September, 2000, the difference was thirteen seconds because of the leap
second difference. Leap seconds are added to or subtracted from UTC time, but not GPS time.
Status and error messages are displayed in Row One, starting at Column Fifteen. The status and
error messages alternate every ten seconds. At initial power-up, this area will display the
Symmetricom firmware version for a few seconds.
3-6 ET6xxx ExacTime GPS TC & FG (Rev C) Symmetricom Inc
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