TM 55-1510-215-10
7. RAD TEST
MON
switch
-
MON
(if
operating in code modes 1, 2, and/or
desired).
3/A in response to ground station
interrogations. This type of oper-
8. TEST light - Monitor to determine when
ation is initiated by the operator as
transponder set is replying to a SIF
follows.
interrogation.
1. Modes 1, 2, and/or 3/A -Operating.
9. MODE 4 AUDIO LIGHT switch - Set (as
required to monitor mode 4 interrogations
2. IDENT MIC switch -
Press
and replies).
momentarily to IDENT,
when
directed.
10. AUDIO and/or observe REPLY light -
Listen
and/or
observe
(mode
4
NOTE
interrogations and replies.
11. IFF CAUTION light (instrument panel
Holding
circuits
within
the
transponder receiver-transmitter will
will illuminate if transponder fails to reply
transmit
identification-position
to a mode 4 interrogation or when the
signals
for
approximately
30
mode 4 codes have been zeroized).
seconds. This is normally sufficient
time for ground control to identify the
NOTE
aircraft's position.
During this 30
second period, it is normal procedure
If IFF CAUTION light illuminates,
to acknowledge via the aircraft
check the position of the MODE 4 ON
set,
that
OUT switch immediately.
If the
identification-position signals arc
switch is in the ON position,
being generated.
establish
contact
with
the
interrogating
station
on
a
(3) Shutdown procedure.
communications set and explain the
situation.
NOTE
(1) To
test transponder set operation in
To prevent zeroizing the MODE 4
modes 1, 2, C and/or 3/A.
function of the transponder. when
the landing gear is down and the
NOTE
struts compressed, place the CODE
control
momentarily
in
HOLD
The following self-tests will not
position before either transponder or
prevent transponder set replies to
aircraft power is turned off. CODE
external interrogations.
Test only
HOLD condition will only be removed
those modes that are being used.
when the struts are extended and the
MASTER control is not in OFF
1. M-1, M-2, M-3/A, M-C switches
position.
-Momentarily set switches to test
position, one at a time.
1. CODE control - HOLD (when
required to hold MODE 4 code).
2. TEST light -Observe for indication
as each code switch is held in TEST
2. MASTER control - OFF.
position. If TEST light fails to light,
recheck applicable control settings.
e. Emergency Operation.
If the light does not illuminate after
the control settings have been
NOTE
rechecked, either the transponder or
the self-test feature is faulty.
The
MASTER
switch
on
the
transponder control panel shall be
(2) Transponder
set
identification
position
placed in the EMER position only
operating procedure.
under emergency conditions.
NOTE
1. Modes 1, 2, and/or 3/A -Operating.
2. Master switch -EMER.
The transponder set can make
identification-position replies while
Change 5 3-35
