12778474-002-2 Revision F – March 2004
TSG-3800 User’s Guide
97
Operating the TSG-3800
Provisioning the Clock Modules
Locked Mode
In Locked mode, the tau increments until the Clock Module is phase locked and final
tau is achieved, which maintains the output frequency with respect to the input
reference. The processor continues to measure the phase of each input. It adjusts
the control value based on phase changes of the selected reference.
Holdover Mode
When an acceptable input reference is not available, the TSG-3800 automatically
enters
Holdover mode
. In Holdover, all outputs continue to be present without
interruption, but the TSG-3800 stops updating the control value to the oscillator and
uses the average control value of the last 24 hours. Changes in output frequency
are now due to aging and environmental variations only.
When the TSG-3800 leaves Holdover, it compares the phase of the Clock modules
to the reference. If the two phases agree, the TSG-3800 resumes operation in the
phase-locked loop (Locked mode) using the pre-holdover phase setting. If the
phase differs significantly (>110 ns), the TSG-3800 enters Acquire mode before
returning to Locked mode.
Holdover mode may also be entered into manually. When entered into manually, the
Clock module stays in Holdover until the operator changes operating modes.
Provisioning the Operating Mode of the Clock Module
The operator can check the type of Clock modules installed in the shelf, its
operating state and loop time constant. To display this information, type:
CLK
then press
Enter
A typical display is:
TSG->CLK
CLK A, Stratum 2E Rubidium
Status
Reference
Mode: Acquire
Tau: 592
Sigma
3.2e-14
CV: -168
%CV: 49.21
Freq Off:
3.73e-10
Range:+5.76e
-0 8
WarmUp Time:
900
Min Tau: 500
Final Tau: 2500 Max
Tau:
10000
Clk B, Stratum 2E DDS
Status: OK
Mode: Acquire
Tau: 423
Sigma:
8.96e-13
CV: -1510
%CV: 49.38
Freq Off:
3.35e-09
Range:
+-8.95e-0
WarmUp Time:
1800
Min Tau: 100
Final Tau: 1500
Max Tau:
5000
TSG->
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