Figure 28. Typical one-shot circuit.

TM 11-6625-667-45/NAVSHIPS 0969-249-8010/NAVAIR 16-30APM123-22/TO 33A1-3-367-22

C4 drives normally conducting Q2 to cutoff. Its

rising collector potential is coupled by R4 to the

base of Q1, driving Q1 into conduction. Capacitor

C2 then starts discharging. and when discharged.

the base of Q2 is driven positive. The one-shot then

returns to its original state.

c. Gates. OR gates used in the test set are the

simple diode types and are not described. Various

types of AND gates exist and there are several

ways of using them; those used in the test set are

described in (1) and (2) below.

( 1 ) Figure 2-9 illustrates a typical diode

AND gate CR1 and CR2 with the inputs con-

nnected to a typical signal source. This circuit is

presented for analysis and does not represent any

specific one in the test set. Two positive signals

must be present at the input of the diodes fit the

same time to cause an AND gate output. The nega-

tive signal at Q2 stops conducting and its collector

TYPICAL

FLIP-

FLOP

CIRCUIT

potential goes positive. This aiction blocks the cur-

TM6625-667-35-9

rent flow through CR2 and provides an enabling

Figure 2-7. Typical flip-flop multivibrator circuit.

voltage at gate diode CR2. When the negative

pulse appears at the input of Q1, its conduction is

stopped. The AND gate is thus enabled by Q2

cut off by the input, and in turn drives Q3 into

conduction. This is the set state, with Q3 provid-

ing the low 0 output and Q4 a high 1 output.

Resistors R9 and R16 bold the respective inputs

high when their stages are not, conducting, to pre-

vent any additional pulses at the high input from

switching a flip-flop state. Thus, an input to the

conducting stage only will change the state. Flip-

flops that have trigger inputs will assume the op-

posite state with an active signal at the input, of

the concluding stage. The signal is coupled to

both stages to force the change in state.

b. One-Shots. All one-shots in the test set are

similarlv constructed. Some one-shots are trig-

gered from the leading edge. of the input pulse and

some are triggered from the trailing edge. The

major difference, between one-shots is the rc time

constant. that determines the duration of the out-

put. Each one-shot has a control to adjust the

width of its output pulse. Figure 28 illustrates a

typical one-shot circuit. In this circuit, an output,

is taken from each stage. In some circuits, only one

of tile outputs shown is used. The time constant of

TYPICAL

SINGLE-

SHOT

CIRCUIT

TM6625-667-35-10

the one-shot shown is determined by capacitor C2,

resistor R5, and control R6. A trigger applied to

Figure 28. Typical one-shot circuit.

2-14

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