# Designing Combinational logic circuit

Discussion in 'Homework Help' started by electrogirl, Jul 29, 2010.

1. ### electrogirl Thread Starter Member

May 2, 2010
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0
A bank burglar alarm (B) will activate if it is after banking hours (A) and someone opens the front door (D). The logic level of A is 1 after banking hours and B during banking hours. Also the logic level of the variable D is 1 if the door sensing switch is opened and B if the door sensing switch is closed.
Determine the Boolean expression to activate the burglar alarm.

I'm confused with this statements "The logic level of A is 1 after banking hours and B during banking hours. Also the logic level of the variable D is 1 if the door sensing switch is opened and B if the door sensing switch is closed."

I think there is something wrong with this statement "The logic level of A is 1 after banking hours and B during banking hours." I think the "B" should be "0".
and also in the next statement the "B" should be "0". Is my presumption correct?

If my presumption is right the result would be B = AD which is just an AND gate.

Do you think there might be some clerical error in the problem or am I the one who is wrong?

2. ### Jony130 AAC Fanatic!

Feb 17, 2009
3,993
1,116
Maybe its should go like this
A bank burglar alarm (B) will activate if it is after banking hours (A) and someone opens the front door (D). The logic level of A is 1 after banking hours and B during banking hours. Also the logic level of the variable D is 1 if the door sensing switch is opened and C if the door sensing switch is closed

3. ### JDT Well-Known Member

Feb 12, 2009
658
85
You are correct. The answer is given in the line quoted. You are confusing yourself by the second sentence where "B" should be "0".