Mode 4 Tests.

TM 11-5895-490-20

(4) Press the AN/APM-123A(V) PRESS TO

(a) On the test set, the ACCEPT light should

light.

TEST switch. The ACCEPT indicator should light.

If the REJECT indicator lights, set in the altitude

(b) On the C-6280A(P)/APX, the REPLY light

should light.

code for one increment (100 feet) above or below the

(c) Audio tone should be heard in headset.

test setting. Press the AN/APM-123A(V) PRESS TO

(12) On the C-6280A(P)/APX, place the AUDIO/

TEST switch. An ACCEPT condition indicates the

LIGHT switch to the LIGHT position, and repeat

RT-859/APX-72 reply is normal; this action accounts

the above test. Audio tone should not be heard, but

for the normal deviations of the CPU-66/A.

REPLY light should light.

f. Mode 4 Tests.

(13) On the test set, place the MODE 4 CODE A/

(1) Prepare equipment for nonradiation opera-

B switch to B and briefly depress the PUSH TO TEST

tion (direct coupling) in accordance with instruc-

switch. The REJECT light should light. Return

tions in paragraph 3-10b.

MODE 4 CODE A/B switch to A.

(2) Connect Interrogator Computer KIR-1A/

(14) On the test set, place the MODE 4 VER BIT

TSEC to test set MODE 4 connector using cable

1 switch to 1 and briefly depress the PUSH TO TEST

CX-12216/APM-123( V). The ZEROIZE light on the

switch. The REJECT light should light. Return

test set should light.

MODE 4 VER BIT 1 switch to OFF.

(3) Using Code Changer Key KIK-18/TSEC, key

(15) On the test set, place the MODE 4 VER BIT

the KIR-1A and close the access door. ZEROIZE

2 switch to 2 and briefly depress the PUSH TO TEST

light on the test set should go out.

switch. The REJECT light should light. Return

(4) Install Computer KIT-1A/TSEC in the air-

MODE 4 VER BIT 2 switch to OFF.

craft.

(16) On the test set, place the ISLS switch to ON

(5) Turn the MASTER switch on Transponder

and briefly depress PUSH TO TEST switch. The

Set Control C-6280A(P)/APX to STBY.

REJECT light should light. Return ISLS switch to

(6) Connect headset to aircraft intercom system.

OFF.

(7) Set the controls on the C-6280A(P)/APX

(17) On aircraft with rigid landing gear, set IFF

as follows

CODE HOLD switch located on aircraft instrument

panel to ON. IFF CODE HOLD light located on air-

craft instrument panel should light. On aircraft with

compression or retractable landing gear, make cer-

tain landing gear is in a stable condition so that the

automatic IFF CODE HOLD switch on landing gear

is activated and remains so.

(18) On C-6280A(P)/APX, place CODE switch to

HOLD, then return to A.

(19) Wait at least 15 seconds and then on the C-

(8) On the test set, place the FUNCTION switch

6280A(P)/APX turn MASTER switch to OFF.

to SYSTEM, the MODE 4 DIR/RAD switch to DIR,

(20) Wait at least 15 seconds and then on the C-

the MODE switch to 4, the MODE 4 Code A/B switch

6280A(P)/APX turn MASTER switch to STBY for

to A and the PUSH TO TEST switch to the LOCK

a warmup of about 30 seconds; then turn MASTER

position, and (when operating test set) observe the

following

switch to NORM.

(21) On the test set, briefly depress PUSH TO

(a) On the test set, the REJECT light should

light.

TEST switch. ACCEPT light should light.

(22) On the C-6280A(P)/APX pull out CODE

(b) Audio tone should be heard in headset.

switch and turn to ZERO, and place AUDIO/

(c) IFF CAUTION light located on aircraft in-

LIGHT switch to AUDIO position.

strument panel should light.

(23) On the test set, place PUSH TO TEST

(9) Using KIK-18/TSEC, key the KIT-1A/TSEC

switch to LOCK position, and observe the following:

and close access door. Observe same indications

listed in (8) above. Release PUSH TO TEST switch.

(a) On the test set the REJECT light should

light.

(10) On C-62110A(P)/APX, place the MODE 4

switch to ON.

(b) Audio tone shall be heard in headset.

(c) IFF CAUTION light located on aircraft.

(11) On the test set, briefly depress the PUSH TO

instrument panel should light.

TEST switch and observe the following:

3-11

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