is a 0 or 5) or a 5 (when the fifth digit is a 2 or 7), there-
fore, the sixth digit does not need to be displayed.
It is possible that erroneous operation could
occur without a fault indication. It is the
responsibility of the pilot to detect such an
reasonableness of operation as displayed on
the associated transceiver control unit and by
Equipment turn-on. The transceiver and the
control unit are turned on by rotating the power and
mode switch on the transceiver control unit to the ON
position. When the transceiver is first turned on it
sounds a brief tone while the microprocessor checks its
own memory. If there is a memory defect the tone
continues, indicating that the transceiver can neither
receive nor transmit. After the memory check, the
transceiver control unit will display the same active and
equipment was last turned off.
If two short 800-Hz tones are heard, the
transceiver has detected an internal fault.
Push the TEST switch on the transceiver
control unit to initiate self-test and display the
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. After a 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.
Frequency selection. Frequency selection is
made using either the frequency select knobs, or the
XFRI MEM (transfer/memory recall) switch Rotation of
either frequency select knob increases or decreases the
frequency in the preset frequency display. The larger,
outer knob changes the frequency in 1-MHz increments
(the number to the left of decimal point). The smaller,
inner knob changes the frequency in 50-kHz increments
when first rotated, or in 25-kHz increments for the first
two increments after the direction of rotation is reversed.
After the desired frequency is set into the preset
frequency display, it can be transferred to the active
frequency display by momentarily setting the XFR/MEM
switch to XFR. 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
The active (ACT) annunciator continuing to
flash indicates that the transceiver is not tuned
to the frequency displayed in the active
The transceiver control unit's memory permits storing
up to six preset frequencies. Once stored, these
frequencies can be recalled to the preset display by
positioning the XFHRMEM switch to the MEM position.
The storage location (CH 1 through CH 6) for the
recalled frequency is displayed in the active frequency
display while the XFR/ MEM switch is held in the MEM
position. All six stored frequencies can be displayed
one at a time in the preset display by repeatedly
positioning the XFRMEM 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 XFR/ MEM
switch to the XFR 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.
Direct active frequency selection. The
active frequency can be selected directly with the
frequency select knobs by pushing the ACT switch for
about 2 seconds. The active frequency selection 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
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 mode,
push the ACT switch 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, TEST, or
XFR/MEM switches are actuated.
Frequency storage. To program the
memory, select the frequency in the preset frequency
display using the frequency select knobs and push the
STO switch once. One of the channel numbers (CH 1
through CH 6) will; appear in the active display for
approximately 5 seconds. During this time the channel
number can be changed with- out changing the preset
frequency by momentarily positioning the XFR/MEM
switch to the MEM position. After