Beechcraft C-12C Operator And Technical Reference Manual page 364

TM 1-1510-218-10
If two short 800-Hz tones are heard, the
transceiver has detected an internal fault.
Push the TEST button on the transceiver
control unit to initiate self-test and display
the fault code.
Adjust the volume and perform a quick squelch
test by setting the power and mode switch on the
transceiver control unit to SQ OFF and adjusting the
volume level with background noise.
comfortable listening level has been established,
return the power and mode switch to the ON position.
AU background noise should disappear unless a
station or aircraft is transmitting on the active
frequency the fault code.
(2) Frequency
selection is made using either the frequency select
knobs, or the XF / MEM recall switch.
There is usually an installer supplied
8.33/25 kHz select switch in the cockpit.
This switch provides a convenience to the
pilots by not having to "ratchet pass" the
8.33 kHz channels when not operating in
8.33 airspace. The selected position of the
(8.33 or 25) may
annunciated, depending on installation.
After the desired frequency is set into the preset
frequency display, it can be transferred to the active
frequency display by momentarily setting the XF /
MEM switch to XF. At the same time that the preset
frequency is transferred to the active display, the
previously active frequency is transferred to the preset
display. A short audio tone is applied to the audio
system to indicate that the active frequency has been
changed, and the active (ACT) annunciator on the
control will flash while the transceiver is tuning to the
new frequency.
The ACT annunciator continuing to flash
indicates that the transceiver is not tuned
to the frequency displayed in the active
display.
The transceiver control unit's memory permits
storing up to six preset frequencies.
these frequencies can be recalled to the preset display
by positioning the XF / MEM switch to the MEM
position. The storage location (CHAN 1 through
CHAN 6) for the recalled frequency is displayed in the
active frequency display while the XF / MEM switch is
held in the MEM position. All six stored frequencies
3C-10
NOTE
After a
Selection. Frequency
NOTE
or may not
NOTE
Once stored,
can be displayed one at a time in the preset display by
repeatedly positioning the XF / MEM switch to the
MEM position. After the desired stored frequency has
been recalled to the preset display, it can be
transferred to the active display by momentarily
positioning the XF / MEM switch to the XF position.
During normal operation, all frequency selections
and revisions are done in the preset frequency display.
However, the active frequency can be selected directly
as described in the following paragraph.
(3) Direct Active Frequency Selection. The
active frequency can be selected directly with the
frequency select knobs by pushing the ACT button for
about 2 seconds.
mode is indicated by dashes appearing in the preset
display. Also, the ACT annunciator will flash as the
frequency select knobs are turned to indicate that the
transceiver is being returned.
The ACT annunciator continuing to flash
after the frequency has been selected
indicates that the transceiver is not tuned
to the frequency displayed in the active
display.
To return to the preset frequency selection
be
mode, push the ACT button again for about
2 seconds. As a safety feature, the transceiver control
unit switches to the active frequency selection mode
when a frequency select knob is operated while the
STO and TEST buttons, or XF / MEM switch are
actuated.
(4) Frequency Storage.
memory, select the frequency in the preset frequency
display using the frequency select knobs and push the
STO button once.
(CHAN 1 through CHAN 6) will appear in the active
display for approximately 5 seconds. During this time
the channel number can be changed without changing
the preset frequency by momentarily positioning the
XF / MEM switch to the MEM position.
desired channel number has been selected, push the
STO button again to store the frequency.
The active frequency selection
NOTE
To program the
One of the channel numbers
After the