The diagram above replicates task 8 in the IET Puzzle Panels. The student (or student team) is required to understand electronic logic gates and binary logic operations through this exercise.
A red light represents binary '0' and a green light is binary '1'; white is undefined, unused or unconnected. There are six AND-gates with the rounded shape (if the inputs are X and Y then the output is represented as X.Y). These give an output of '1' iff both inputs are '1'. The OR-gates give an output of one if either input is '1' (the output is written as X + Y). The NOT-gates at the bottom reverse the input (with input X the output is either !X or X). In all cases, if an input is not connected (or connected to a device with an inactive output), the output is undefined.
The task is to use the 4 varying input sigals on the left to exactly match the outer light for each at the 3 independent outputs - there are essentially three separate problems. When completed correctly, the inner and outer light should be remain identical as the lights sequence resulting in one solid colour.
Create jumper leads by clicking on the output and input points that will be the ends of the jumper (in either order; you are not allowed to connect two outputs or two inputs together, they have to be different - like XOR gate rules). Many jumpers can be connected to a single output, but only one jumper can be connected to an input. To remove an existing jumper, click on the input end.
The strategy is to closely examine how the target light responds as the source LEDs change, looking for a pattern or rule. You may need to construct a truth table if the behaviour is complex. Once you have this, convert the rule into an expression involving AND, OR and NOT conditions. These you then implement and test. Unused gates have no effect. If you find you do not have enough gates, you may need to simplify your expression using a technique such as applying de Morgan's rules or Karnaugh mapping. You can also treat the problem in terms of the intersection and union of sets.
To get you started, for Set 1 the solutions are:
Q1 = A.B
Q2 = B+C
Q3 = D
Try implementing these using the appropriate gates.
The exercises are fairly difficult because the lights cycle with a delay of only 1 second, which makes it hard to spot the pattern.