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SECTION 20
FRONT PANEL (A14)
20-1. GENERAL. The front panel assembly consists of a display board module and the analyzer operating
switches and controls. A schematic diagrmn of the front panel assembly is shown in figure 20-1.
20-2. DISPLAY BOARD. The display board holds and decodes LED data. A display of 27 LEOs is driven by
24 drivers and three inputs from external sources. The keyboard is a 5-row X4-column matrix of momentary
contact switches. Jumper connections on
th~
board are used to route signals between connectors. The display
board consists of three latch/decoders, 24 LED drivers, and a 27 LED display. A display board block diagram is
shown in figure 20-2.
20-3. The three latch/decoders hold and decode input data from the AF DATA BUS 0-3. Signals LSO- LS2 are
latch selects that transfer data from the AF DATA BUS 0-3 to the corresponding latch. Only one LED at a time
can be turned on by any of the three latch selects. Each driver is an open-collector device which sinks current
through its respective
LED.
20-1
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