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A digital logic circuit controls a safety valve in a chemical processing unit. The circuit has two binary inputs:

$X$ , representing whether the pressure is within safe limits ( $\text{True}$ , $\text{False}$ )
$Y$ , representing whether the temperature is within safe limits ( $\text{True}$ , $\text{False}$ )

The safety valve is open when the output signal $S\,$ is 1. The logic governing the output is: $\text{NOT}(X \text{ OR } \text{NOT } Y)$

Complete the truth table for this control system by finding the values of $P$ , $Q$ , $R$ , and $S$ .

$X$	$Y$	$Y)\text{NOT}(X \text{ OR } \text{NOT } Y)$
0	0	[ P ]
0	[ Q ]	1
[ R ]	1	0
1	0	[ S ]

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Truth tables Questions

Practise Edexcel GCSE Computer Science Truth tables with exam-style questions for GCSE Computer Science. 15 questions covering Applying logical operators in truth tables, matched to the Edexcel GCSE Computer Science (1CP2) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.