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The line $T$ in the following figure is permanently connected to the ground.

Which of the following inputs $(X_1 X_2 X_3 X_4)$ will detect the fault ?

  1. $0000$
  2. $0111$
  3. $1111$
  4. None of these
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8 Answers

1 votes
1 votes

We consider circuit in two different configurations to check the inputs. And then apply the three available inputs to get output values. On doing so, we observe that all inputs give same outputs in both the configurations. Thus None of these is the answer.

kriti_2

kriti_3

0 votes
0 votes

Correct Circuit:

$f = [\{(x_1x_2x_3)’ + x_4\}’ + x_3x_4]’ = [x_1’ + x_2’ + x_3’ + x_4 + x_3x_4]’ = [x_1’ + x_2’ + x_3’ + x_4]’ = x_1x_2x_3x_4’$

Faulty Circuit:

$f = [\{(x_1x_2x_3)’ + x_4\}’ + \mathbb{T}]’ = [\{(x_1x_2x_3)’ + x_4\}’ + 0]’ = x_1x_2x_3x_4’$

which is the same as the correct circuit.

$\therefore$ There is no way to detect the fault.

ANS: (D.)

–2 votes
–2 votes
Answer should be c option as all 1 's will show the significance of grounded line.
–2 votes
–2 votes
Given : line T=X3.X4 is permanentally connected to the ground (i.e. T=X3.X4=0)
final result is depends on only T ' =1
so X3.X4=1
X3=1 , X4=1
final value dont depend on X1 and X2
hence ans is B and C
Answer:

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