Question
(a) Write down the truth table for an OR gate.
[2]
(b)Draw the symbol for a NOR gate.
[1]
(c) Fig. 9.1 shows a digital circuit designed to produce the values shown in Table 9.1 for the output S from the two inputs P and Q.
Table 9.1 is the truth table for the circuit shown in Fig. 9.1.
Table 9.1
P
Q
R
S
0
0
0
0
1
0
1
0
1
1
1
0
Complete the column for point R in Table 9.1. [1]
State which type of gate is used for gate X. Explain your answer.
statement …………………………………………………………………………………………………………..
explanation ………………..[3] [Total: 7]
Answer/Explanation
Ans:
(a) 
(b) two inputs to curved face, sharp end with small circle and one output
c(i) 
(c)(ii)
AND
input 1 and 1 gives output 1
any 0 input gives 0 output