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5−
33
e. The green LOCKED LED indicates that the unit is locked to an input.
f. The yellow FREERUN LED indicates that the unit is in the FREERUN
mode.
g. The green ACTIVE LED indicates that the unit is driving the outputs.
h. The green GPS LED indicates that the unit is tracking the GPS input.
i. The yellow DEGRADED LED indicates that the unit is not in the GPS
tracking mode.
j. The seven segment display indicates the STATUS of the output failure.
k. The HOLD TEST pushbutton causes the microcontroller to execute a
diagnostic routine and display 'H' if successful. The unit returns to normal
tracking in a few seconds. (An internal TEST/RUN toggle, S2, is set in the
RUN mode for normal operation.)
5.8229 Alarm
Output
The HOLD or FAIL condition, or a fault reported by the crystal oscillator,
results in a card alarm output to the 54560 Alarm Interface Card and to the
54550 Information Management Card. A data link to the 54550 card allows
the 54591 card to report its status (tracking, hold, stand-alone, or failed) as
well as control, personality and, with DS1 only, sync messaging data.
5.8230 Clocks A and B
Each of the two 54591 cards in a redundant system drives a Clock A or B
differential clock bus to the ten output card slots. Each card also drives a hold
indicator bus. Selection of the A or B clock is done automatically by logic
circuitry on the output cards; it can be changed manually from a terminal
connected to the 54550 Information Management Card.
5.8231 External 5 or 10 MHz Signal
In addition to the DS1/E1 inputs, the external 5 or 10 MHz signal may also be
selected as a tracking input. Selection is done manually by TL1 or Menu user
command through the interfaces of the 54550 Information Management Card.
Once an external signal has been selected as the tracking reference, the clock
card will stay on it until the user issues a different command. If the signal is
bad during external signal tracking, the clock card will enter the HOLD mode
until the signal recovers. However, the clock card will not go back to tracking
DS1/E1 inputs unless told to do so by command issued via the 54550 card.
5.8232 Monitor
Jack
A front panel DS1/E1 monitor jack (-20 dB referenced to the input) provides
framed all ones at the clock output frequency.
5.8233 One-wire
Interface
A one-wire interface communicates to the 54550 Information Management
Содержание 54500-16
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