TM 55-1510-215-10
(a) Up (on) position. Permits set to
(c) LIGHT
position.
Permits
only
reply in the selected mode.
REPLY light monitoring.
(b) OUT pos ition. Disables replies.
(c) TEST position. Permits self test in
c. IFF Caution Lig ht. The function of the IFF
the selected mode when test set TS-1843A/APX is
caution light (fig. 2-22), placarded IFF CAUTION, is as
installed. The transponder set can also reply to ground
follows:
interrogations in the selected mode while being tested.
(1) IFF. Indicates that the transponder set
(d) M-1 and M-2 switches . Response
has failed to reply to a valid mode 4 interrogation. It also
to military identification interrogations.
illuminates when mode 4 codes have been zeroized.
(e) M-3/A switch. Response to civilian
d. Transponder Set Operation. If mode 4 operation
identification interrogations.
is required, perform the following procedures after the
(f) M-C switch. Response to altitude
landing gear has been retracted.
reporting interrogations.
NOTE
(6) RAD TEST MON switch.
Provides a
MODE 2 code selectors are located
means of selecting the following:
on
the
transponder
receiver-
transmitter and should be set prior to
(a) RAD
TEST.
Enables
an
flight when required.
appropriately equipped transponder to reply to TEST
mode interrogations.
NOTE
(b) MON position. Turns on circuits in
the transponder test set to monitor for proper replies to
To prevent zeroizing the mode 4
M-1, M-2 or M-3/A interrogations.
function of the transponder, when the
landing gear is down and the struts
(7) IDENT M C switch. Provides a means of
I
compressed, place the CODE control
selecting the following:
momentarily in HOLD position before
(a) IDENT
position.
Activates
either transponder or aircraft power
identification feature.
is turned off. CODE HOLD condition
(b) MIC position. Inoperative in this
will only be removed when the struts
installation.
are extended and the MASTER
control is not in OFF position.
(8) MODE 1 and MODE 3/A code selector.
Selects the desired reply codes for modes 1 and 3A.
1. MASTE R control -STBY (allow 2
minute warmup).
NOTE
Modes
1, 2, 3/A, and/or mode 4 operating
procedure.
MODE 2 code selector is located on
2. MASTER CONTROL - LOW or
the transponder receiver-transmitter
NORM. Set for required receiver
and should be set prior to flight when
sensitivity.
required.
3. M-1, M-2, M-3/A, and/or MODE 4
ON OUT switches -ON. Actuate
(9) MODE 4 IFF ON OUT switch. Provides a
only those switches corresponding
means of selecting the following:
to the required codes.
The
(a) ON position. Permits transponder
remaining switches should be left in
set to decode a mode 4 interrogation.
the OUT position.
(b) OUT position.
Disables mode 4
4. MODE 1 code selectors - Set (if
decoding.
applicable).
(10) AUDIO OUT LIGHT switch. Provides a
5. MODE 3/A code selectors - Set (if
means of selecting the following:
applicable).
(a) AUDIO position. Permits aural and
6. CODE control - Set (as required).
reply light monitoring of valid mode 4 interrogations and
replies.
(b) OUT position.
Disables mode 4
decoding.
3-34 Change 5
