markings are illuminated by 21 miniature lamps embedded
required for pilot operation and monitoring of transponder
in the plastic panel. These lamps are not replaceable. Input
systems with AIMS capabilities.
voltage applied to these lamps must not exceed 5 volts DC.
115. DESCRIPTION OF EQUIPMENT.
The panel of the C-6717/APX is red-lighted and that of the
C-7483/APX is white-lighted.
1 16. GENERAL. The transponder set controls, shown in
1 21. MASTER SWITCH. The MASTER switch is a five-
same. The major differences are in the method and color of
position rotary switch. In addition to turning the transponder
panel illumination (paragraphs 119 and 120) and the
set on or off, this switch controls the sensitivity of the trans-
number of mounting fasteners (paragraph 117). Except
ponder receiver and provides for emergency reply operation.
for the differences in input voltage required for panel light-
To prevent accidentally switching to the emergency (EMER)
ing, and the C-6280A(P)/APX which uses six turnlock fas-
or the OFF position, the switch knob must be pulled out
teners for installation, the units are interchangeable. Each
before the switch can be turned to either of these positions.
unit measures 5.75 x 5.25 x 3.09 inches and weighs approx-
1 22. OPERATING MODE SELECTION. The transponder
imately 2.75 pounds. Two knob-actuated rotary switches,
set control includes four mode-enabling switches which are
eight toggle switches, and two press-to-test indicator lights
used to select the operating mode of the transponder set.
are mounted on the panel. The functions of these controls
These are three-position toggle switches which, besides the
and indicators are described in Table 11. No electron
ON and OUT (off) positions, also include a momentary
tubes, semiconductor devices, resistors, capacitors, or in-
position for test signal selection.
ductors are used.
123. REPLY CODE SELECTION. The transponder set
117. INSTALLATION. The transponder set control is
control includes separate groups of thumbwheel switches
designed for installation in a standard aircraft control panel
for selecting the codes for Mode 1 and Mode 3/A replies.
and is equipped with turnlock fasteners for easy installa-
Code selection controls for Mode 2 replies are usually lo-
tion and removal. The C-6280(P)/APX, C-6717/APX, and
cated on one of the other units of the transponder set. Two
C-7483/APX are each equipped with four turnlock fasten-
switches are used for Mode 1 and four are used for Mode
ers while the C-6280A(P)/APX is equipped with six turnlock
3/A. All switches include indication knobs which in com-
fasteners. The unit is installed in a position that is accessible
bination digitally display the selected code number.
to the operator. Electrical connections are made through a
55-pin connector on the rear of the unit. The transponder
124. IDENTIFIER PULSE SELECTION. The transpon-
set control is connected to the other units of the transpon-
der set control includes a three-position toggle switch for
der system through this connector and associated aircraft
identifier pulse selection. The identifier pulse is selected
wiring. External wiring for a typical installation of the trans-
when the switch is held in the momentary IDENT position.
ponder set control is shown in Figure 12.
With the switch set to the MIC position, the identifier pulse
is selected when the microphone keying switch (not part of
118. PANEL ILLUMINATION. The markings on the plas-
the transponder set control) is closed.
tic panel of the transponder set control are illuminated
from behind and glow with a red, white, or blue-white light.
125. TEST PROVISIONS. A three-position toggle switch
The light is also used to illuminate the numerals on the
on the transponder set control is used to select transponder
thumbwheel switch knobs and the lettering on the rotary
test operation. When Transponder Test Set TS-1843( )/APX
is included in the installation, the MON position of the
switch turns on the monitoring circuits of the test set. The
119. On the C-6280(P)/APX and the C-6280A(P)/-APX,
RAD TEST position of the switch is used to enable an
the light is provided by five replaceable incandescent lamps.
appropriately equipped transponder set to reply to TEST
The color of the light is determined by the color of the
mode interrogations from an AN/APM-123(V)( ) or similar
falter in the panel light holder. Since the transponder set
control is designed for use in various aircraft which may have
126. Each of the four mode-enabling toggle switches on
different panel "lighting requirements, it is supplied with
the transponder set control includes a momentary TEST
panel light holders with blue-white, red, or clear falters and
position. The TEST position, when selected, allows a locally-
either 6- or 28-volt lamps. The units can be converted for a
generated interrogation signal from the transponder monitor
different panel lighting requirement by changing the lamps
and holders. A two-letter category, which is stamped on the
(such as Transponder Test Set TS-1843( )/APX) to be applied
to the transponder set. Transponder set replies to the test
packing carton, has been assigned to indicate how the unit
has been equipped. These categories are: A, 6-volt lamps;
signal are indicated by the TEST indicator light.
B, 28-volt lamps; C, blue-white falters; D, red falters; and E,
127. MODE 4 CONTROLS. The controls and indicator
for Mode 4 operation are grouped together along the left side
of the control panel. A MODE 4 ON-OUT toggle switch is
120. On the C-6717/APX and the C-7483/APX, the panel