how can i design this logic circuit?

Question

* in a simple copy machine, a stpo signal, S, is to be generated to stop the machie operation and turn on an indicator light whenever either of the following conditions exists:
1.there is no paper in the paper try
2.two switches in the paper path are activated,indicating a paper jam
* the presence of paper in the tray is indicated by a HIGH at logic signal P
* each switch produces a logic signal(Q and R) that go HIGH whenever paper is passing over the switch to activate it.


* design the logic circuit to produce a HIGH at output signal S for the stated conditions: simplify the expression and implement the circuit in gates.

Answer 1

S = Not P + Q*R

The expression is as simple as it gets.

So you would just need a NOT gate and an AND gate. You could either throw both these outputs into an OR gate, or you could just join the two outputs together.

Answer 2

dylan nailed the logic, but here's your logic circuit.

http://i83.photobucket.com/albums/j314/Jshwaa/logiccircuit.gif