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This is a very simple task and I understand most of it (already has a solution), but there are some things which I need clarification for.
The problem is: There are two doors (one behind the other), and a card reader next to them. The corresponding door will open if the card is inserted into the reader and if the correct password is typed on the reader's keyboard. The truth table for the card reader looks like this: enter image description here

To unlock the DOOR1 you have to type one of the correct passwords, which are: 101 and 110. To unlock the DOOR2 you have to type one of these passwords: 101 or 011. If the wrong card is inserted or the wrong password is typed, the alarm will turn on.
I have to implement this using only standard logic gates. The problem lies in this truth table below (which is a solution). I don't understand what X, Y and Z are.

enter image description here

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  • \$\begingroup\$ Maybe X is the DOOR1, Y DOOR2, and Z is the alarm? \$\endgroup\$ – A6SE Jan 28 '15 at 20:30
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Yes, your assumption is correct. X is DOOR1, Y DOOR2 and Z is the alarm.

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