be displayed in the lower window. When this switch is
held to the MEM position, one of the six stacked memory
frequencies will be loaded into the preset display.
frequencies through the display ( 2,3,4,5,6,1,2,3 ).
placarded STO, allows up to six preset frequencies to be
selected and entered into the control unit's memory.
After presetting the frequency to be stored, push the
STO switch. The upper window displays the channel
number of available memory (CH 1 through CH 6) while
the lower window continues to display the frequency to
be stored. For approximately 5
seconds, the MEM switch may be used to advance
through the channel numbers without changing the
preset display. Push the STO switch a second time to
commit the preset frequency to memory in the selected
location. After approximately 5 seconds, the control will
return to normal operation.
Tuning knobs. Two concentric
tuning knobs control the preset or active frequency
displays. The larger knob changes the three digits to the
left of the decimal point in 1-MHz steps. The smaller
knob changes the two digits to the right of the decimal
point in 50-kHz steps (or in 25-kHz steps for the first two
steps after the direction
of rotation has been reversed). The numbers will roll
over at the upper and lower frequency limits.
Active switch. The active switch,
placarded ACT, enables the tuning knobs to directly tune
the VHF transceiver, when depressed and held for two
seconds. The bottom window will display dashes and
the upper window will continue to display the active
frequency. Pushing the ACT switch a second time will
return the control unit to the normal two-display mode.
Test switch. This switch placarded
TEST initiates the transceiver self-test diagnostic
routine. (Selftest is active only when the TEST switch is
Light sensor. This built-in light
sensor automatically controls display brightness.
Volume control. The volume control
is concentric with the power and mode switch.
Power and mode switch. The
power and mode switch contains three detented
positions. The ON and OFF positions switch system
power. SQ OFF position
disables the receiver squelch circuits.
control unit contains a MEM (memory) and a TX
illuminates whenever a preset
Active Frequency Display
Power and Mode Switch
Annunciators (MEM, TX)
Preset Frequency Display
Figure 3-4. VHF Communications Transceiver Control Unit