SIF SELF-TEST MODE

TM 11-4920-296-14&P

the REPLY SAMPLE (DATA) must match, in

VIDEO. If the reply is correct, the KIR-lA

order to generate an SIG GO strobe (U1 -

feeds a TDV signal to the test set, where it

is applied to the second input of the U4 AND

TP4) and eventually therefore, to produce

circuit (whose other input is the coincidence-

the ACCEPT indication.

check pulse). With both inputs receiving cor-

2-43. M O D E - 4 SELF-TEST. As for the

rect signals, the AND circuit then enables the

S I F self-test mode, the counted-down

evaluator U4 circuits to count the reply as a

CLOCK generates a DATA pulse (U3-TP1),

correct reply (in the same manner as it

w h i c h is loaded into the shift-register to

counts SIF GO pulses for SIF modes). Thus

initiate the To pulse. In Mode 4, this To

the U4 circuits will light an ACCEPT lamp if

pulse then initiates generation of a 2-pulse

t h e correct-reply rate exceeds the specified

M4 interrogation (U2-TP10), which is ap-

80, or 40 percent of interrogations (as deter-

plied to the rf module as transmitter modu-

mined by the type of transponder being tested).

l a t i o n (U2-TP8). The last of these interro-

gation pulses is also sent to GTC ST (U3-

2-40. SIF SELF-TEST MODE. For self-

TP8), and generates a GTC GO signal (U3-

t e s t operation, the FUNCTION switch is

TP9) which enables the 3-pulse decoder of

placed in the SELF TEST position, and the

U3 for approximately 78 microseconds.

MODE switch is placed in any of its posi-

t i o n s . In this operation, the counted-down

2-44. I n this M4 self-test mode, the

CLOCK generates a DATA pulse (U3-TP1),

transmitted signal is coupled to the receiver

which is loaded into the shift-register as

c i r c u i t s , where it is processed and then

t h e To pulse (U2-TP4) and results in an

coupled to the digital circuits as the REPLY

SIF P1 pulse (U3-TP5) and a VIDEO GATE

SAMPLE (U3-TP10). T h u s , the two pulses

( U 3 - T P 3 ) to activate the receiver circuits

r e c e i v e d are loaded into the shift-register.

video gating. Additionally, initiation of the

Together with the initial pulse that was gen-

To pulse causes a P1 interrogation pulse

erated, these pulses now appear as the To

(U2-TP8), which is applied to the rf module

p u l s e (U2-TP4), the l-microsecond tap

as the 1030-MHz transmitter modulation.

p u l s e (U2-TP2), and the 2-microsecond tap

p u l s e (U4-TP2). T h e s e signals are now

2-41. S i n c e the receiver circuits are gated-

applied to the 3-pulse decoder circuit of U3

on by the VIDEO GATE while the P1 pulse is

and are evaluated as if they were a normal

b e i n g transmitted, the transmitted P1 pulse

M o d e - 4 reply.

i s received, detected, and appears as a

R E P L Y SAMPLE pulse (U3-TP10) to the

2 - 4 5 . If the Interrogator Computer KIR-lA

d i g i t a l circuits. T h i s REPLY SAMPLE

is not connected to the test set, a TDV sig-

pulse desynchronizes the CLOCK, and

nal is not required to produce the ACCEPT

appears as DATA (U3-TP1) to be loaded

i n d i c a t i o n , since the output of the 3-pulse

i n t o the shift-register stages. When loaded,

d e c o d e r triggers the ACCEPT circuit

this DATA becomes the Cl pulse following

through the normal evaluation path. If the

the F1 pulse that was previously generated.

KIR-lA equipment is connected, during M4

The F1 and Cl pulses are now shifted through

s e l f - t e s t mode, an M4 PRETRIGGER is

t h e register, and at the proper tap, an F2

s e n t to the KIR-lA from the test set. The

p u l s e is generated. This F2 pulse is then

REPLY SAMPLE is then sent to the KIR-lA

sent to the rf module as a modulation pulse,

and if the reply is correct, the KIR-lA re-

and is then channeled back to the digital

t u r n s a TDV signal. This is the correct,

section as a REPLY SAMPLE (DATA) pulse

and required, ACCEPT condition for this

i n the same manner as was the Cl pulse.

mode of operation.

Once loaded into the register, the special

3 - p u l s e code (Fl, Cl, and F2) is shifted

2-46. R F MODULE Al. The rf module Al

through the register as a normal SIF reply.

receives video-type signals from the digital

section of the test set, and produces pulsed

2-42. For this special 3-pulse REPLY, the

rf outputs in response to those inputs. The

f r o n t panel CODE select switches are by-

rf output pulses from the rf module consti-

p a s s e d , and the parity-check circuits are

tute the actual interrogation pulses applied

preset to look for Fl, Cl, and F2. Therefore,

2-12