More complex logic systems

Logic gates are used to build up complex logic systems, such as burglar alarms and combination locks.

• These may be built up of many different primative logic gates.
• Some logic gates may have more than two inputs. However you are only required to understand the logic of the two-input gates.

The diagram below shows a complex logic gate combining three simple gates. Altogether there are three inputs and eight possible outcomes. To complete a truth table do a whole column before moving to the next column. To solve the table below first find D, then E and finally Z. D depends only on A, E depends on B And C, and X depends on E Or D.

Complex logic gate and associated truth table