Suppression Pulse (P2) Generation

TM 11-6625-667-45/NAVSHIPS 0969-249-8010/NAVAIR 16-30APM123-1/TO 33A1-3-367-99

during self-test operation. Upon being triggered

with the triggering of ISS1, encode enable IFF1

by the P1 and P3 pulses, a negative pulse-pair is

is set. This flip-flop contains transistors A4Q3 and

produced at the 0 output. The duration of each

A4Q4. When set, the 1 output (A4Q4) goes high

pulse is 0.8 microsecond. This duration is adjusted

and establishes the gate enabling voltage at the

with control A4R41. The negative pulse-pair is

P1 and P3 gates. This condition is maintained

gated and inverted by main modulator driver

until IFF1 is reset approximately 25 microseconds

A4Q11 and A4Q12. The pulse are amplified and

later by the P3 pulse from inverter amplifier

applied to the main modulator.

A5Q9/A5Q10. Thus, the 1 output goes low and

disables the P1 and P3 gates after this period.

(4) The positive delay line P3 pulse is gated

b. Interrogation. Pulse-Pair (P1 and P3)

and inverted by the P3 gate and applied to DC

Generation.

amplifier A5Q9 and A5Q10 as a negative pulse.

(1) The interrogation pulse-pair (P1 and

This pulse is again inverted, and the resultant

positive pulse is used to reset IFF1. This action

P3) is first formed in the delay line. This delay

line is common to both the encoder circuit and de-

returns the 1 output to a low state. Thus, the en-

abling voltages are removed from the P1 and P3

coder section of the test set. Six delay line taps

gates approximately 25 microseconds after they

are used for the encoder operation. Any one of the

were enabled The DE pulse is also applied to the

five selectable taps is used for obtaining a P1

decoder section as a decode-enable pulse.

pulse. A tap common to these selectable taps is

used to obtain the P3 pulse. This common tap is

c. Suppression Pulse (P2) Generation. Genera-

25 microseconds down the delay line. As shown in

t ion of the P2 pulse is delayed for 2 microseconds

figure 8-2, the P1 pulse is .selected ahead of this

from the leading edge of the P1 pulse. The leading

tap: therefore, the nominal pulse-pair spacing is

edge of the negative-going P1 gate output is de-

determined by subtracting the value of the selected

veloped from A5Q12 triggers P2 delay generator

P1 tap from the 25-microsecond common trip. For

ISS3, a one-shot multivibrator containing tran-

example. figure 8-2 shows MODE switch A15S5

sistors A4Q5 and A4Q6. When the one-shot multi-

positioned at mode 1. This connects the P1 gate

vibrator (ISS3) is triggered, it produces a

to the 22-microsecond tap. Subtracting 22 micro-

2-microsecond positive pulse the width of which is

seconds from 25 microseconds results in 3 micro-

adjusted with control A4R32. The positive pulse is

coupled by FUNCTION switch A15S6 and

seconds, the nominal mode 1 spacing. Each delay

MODE switch A15S5 to P2 shaper ISS2 during

line output is coupled by an emitter follower to its

all tests except mode 4 and self-test, P2 shaper

respective AND gate.

ISS2 contains transistors A4Q7 and A4Q8 and

(2) The P1 pulse delay time depends on the

functions as a one-shot multivibrator. The trail-

mode selected by MODE switch A15S5. The

ing edge of the 2-microsecond pulse triggers ISS2,

selected P1 pulse applied to the P1 gate is gated

which produces a negative-going, 0.8-microsecond

and inverted by the P1 gate. The resultant nega -

P2 pulse. Thus, the P2 pulse is spaced 2 micro-

tire pulse is applied to the P1-P3 gate and to P2

seconds from P1-pulse. During mode 4 tests, the

delay genealtor ISS3. A negative P3 pulse arrives

rc time constant of ISS2 is changed to produce

later by any of the P3 gate. The negative P3 pulse

0.5-microsecond pulses. Resistor A4R30 is switched

is also applied to DE amplifier A5Q10. The

into the circuit by MODE switch A15S5. Contro]

nominal delays of the P3 pulse for modes 1, 2,

A4R29 provides a common pulse-width adjust-

TEST, 3/A, and C are 3, 5, 6, 5, 8, and 21 micro-

ment. The negative pulse output of ISS2 is coupled

seconds, respectively.

by ISLS switch A15S7 to either the low P2 modu-

(3) The P1P3 pulses, gated and inverted

lator driver or to the main modulator driver. If

by the P1-P3 gate, trigger P1-P3 shaper ISS4.

the switch is set to OFF, the negative pulse will

This one-shot multivibrator (ISS4) contains tran-

be amplified and inverted by the low P2 modu-

sistors A4Q9 and A4Q10. Transistor A4Q9 pro-

lator driver and applied as a positive pulse to the

vides the normally high 0 output and A4Q10 the

normally low 1 output. The 1 output is used only

low P2 pulse modulator in the transmitter. The

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