12: Front Panel Assembly
PRC1099A-MS 12-5
the processor. The processor mutes the receive audio when no voice is
detected on the VOICE DET line from the Audio/Filter board (refer to
“Squelch Circuit” on page 3-4).
LSB Position The LSB position selects lower sideband operation. The LSB line is grounded
through the Mode and Option switch center conductor. The LSB signal is
applied to the input demultiplexer U14 on the Processor board and the data is
transferred to Processor U1. The Processor sends a control signal to DDS U9
to change the BFO from 1650 kHz to 1647 kHz.
OPT Position The OPT position selects the AME modulation option that allows AM
receivers to receive single sideband modulation transmissions. The OPTSW
signal to the processor on the Processor board is grounded through the Mode
and Option switch center conductor. This signal in normally pulled high
(+5V) on the Processor board.
The OPTSW signal is applied to input demultiplexer U14 on the Processor
board and the data is transferred to Processor U1. The processor asserts a line
on the Audio/Filter board to turn on AME SW Q20 that enables the
1650 KHZ input from the Synthesizer board (refer to “AME Option” on page
5-6).
12.1.4 Digit and Tune Switch
Digit Switch The front panel DIGIT switch selects frequency digits and channels as well as
Option, Data, and Scan menu items. When you push the switch up or down,
the selected item blinks once to indicate that it is selected.
When you press up on the DIGIT switch, the DIGUP line is grounded through
the switch center conductor. This line is held high (+5V) until it is grounded
using the DIGIT switch. The processor reads the low line level at U14 on the
Processor board and increments the display on the Display board to the next
frequency digit to the right, channel, or option menu. When you press down
on the
DIGIT switch, the DIGDN line is grounded, the processor reads the
change and decrements the display to the next frequency digit to the left,
channel, or option menu.
For more information about specific menu items, refer to the PRC1099A
Operator manual (PRC1099A-MSOP).
Tune Switch The front panel TUNE switch increments or decrements the digit or menu item
selected by the
DIGIT switch. For example, if you select a digit within the
channel frequency with the DIGIT switch, you use the TUNE switch to
increment (push the switch up) or decrement (push the switch down) the digit.
You can also use the
TUNE switch to scroll through the specific menu items in
the Option, Data, and Scan menus.
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