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5−
9
Two input channels are monitored with loss detector circuits and report loss of
signal through a serial communication path. The LOS LED lights if the current
active input is in an alarm condition.
5.4212 LED
Indicators
Front panel LEDs indicate the following conditions:
a. The red FAIL LED lights when the internal fuse has blown or the power
supply has failed.
b. The green INPUT A/B LEDs indicate which of the two INPUT signals is
being tracked.
c. The green PULSES LED is on if the PLL oscillator is in working condition.
d. The yellow INPUT FAULT LED indicates an internal fault.
e. The red LOS LED indicates either a loss of signal (more than 175 ±75
consecutive zeros).
The LOS condition results in a card alarm output on pin 44 to the 54560 Alarm
Interface Card and to the 54550 Information Management Card.
5.4213 Output
Data
The recovered clock is sent to both track and hold cards via backplane buses.
The recovered clock is also sent on another bus to all output cards for use if
both track and hold cards should fail.
The serial output, serial clock, interrupt, and chip select lines are connected to
both track and hold cards.
There is an Input Select line from the corresponding track and hold card to
