TM 1-1510-224-10
4.
Power and mode switch (fig. 3-25) -
ON.
After power is applied, the control unit displays
the same active and preset frequencies that were
present when the equipment was last turned off.
(2) Frequency
selection.
Frequency
selection is made using either the frequency select
knobs, or the XFR/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 (number to the left of decimal point). The
smaller, inner knob changes the frequency in 0.05 MHz
increments. After the desired frequency is set in 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. The ACT annunciator on the control unit flashes
while the receiver is tuning to the new frequency.
NOTE
The ACT annunciator continuing flashing
indicates that the receiver is not tuned to the
frequency displayed in the active display.
The control unit has memory that permits storing
up to four preset frequencies. Once stored, these
frequencies can be recalled to the preset display by
positioning the XFR/MEM switch to the MEM position.
The storage location ( CH 1 through CH 4 ) for the
recalled frequency is displayed in the active frequency
display while the XFR/MEM switch is held in the MEM
position. All four stored frequencies can be displayed
one at a time in the preset display by repeatedly
positioning the XFR/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 XFR/MEM switch
to the XFR position.
During
normal
operation,
all
frequency
selections and revisions are accomplished in the preset
frequency display. However, the active frequency can
be selected directly as described in the direct active
frequency selection paragraph.
(3) 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 receiver is
being retuned.
NOTE
The ACT annunciator continuing flashing
indicates that the receiver 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 control unit automatically
switches to the active frequency selection mode when a
frequency select knob is operated while the STO, TEST,
or XFR/MEM switches are actuated.
(4) Frequency storage. Up to four preset
frequencies can be stored in memory in the control unit
for future recall. 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 4) 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 XFR/MEM switch to the MEM position.
After the desired channel number has been selected,
push the STO switch again to store the frequency.
NOTE
When storing a frequency the second
actuation of the STO switch must be done
within 5 seconds after selecting the channel
number or the first actuation of the STO STO
switch. If more than 5 seconds elapse, the
control will revert to the normal modes of
operation and the second store command
will
be
interpreted
as
the
first
store
command.
After a frequency has been stored in memory, it
will remain there until changed by using the STO switch.
Memory is retained even when the unit is turned off for
an extended period of time.
d.
Self-Test. During self-test, the VIR-32
provides VOR, ILS, and marker beacon test outputs.
The following paragraphs provide the procedures
required and the results to be expected when performing
the self-test.
(1) VOR Self-Test
1.
Tuning knobs (NAV control unit) -
Select a VOR frequency.
NOTE
A specific frequency is not required for the test.
Also, a signal on the frequency will not interfere with
the self-test.
2.
VOR/localizer pushbutton selector
switch (display controller, fig. 3-8) -
Select VOR1 or VOR2, as required.
3-59