How about this one -- designing a circuit?

problem:

In a certain automated manufactoring process, electrical components are automatically inserted in a PC board. Before the insertion tool is activated, the PC board must be properly positioned and the component to be inserted must be in the chamber. A HIGH voltage indicates each of these prerequisite conditions. The insertion tool requires a LOW voltage to activate it. Design a circuit to implement this.

Someone please help.... i just keep confusing myself here!!

Is this a homework question? It helps to know.

Do you need to design a control system for the entire machine or just a circuit to output a low voltage when a high voltage exists at some point? Explain what high and low voltage is - to you.

On any logic circuit like this there is a good brute force method for finding a logic circuit.

If you draw up the whole truth table you can then make a logic circuit that ANDs together all the 1's and NOT 0's in the input for each line in the table that give a 1 as the output. You then Or all these little circuits together. A little boolean algebra and you have your final circuit.

an example for the truth table posted:
Line 1: (P AND Q)
Line 2: nothing because it outputs a F
Line 3: ((NOT P) AND Q)
Line 4: ((NOT P) AND (NOT Q))

Now OR them all together:

(P AND Q) OR ((NOT P) AND Q) OR ((NOT P) AND (NOT Q))

This is a valid circuit but you need to use Boolean algebra to simplify it.

If A is true and B is true then C is false. This is the definition of a NAND gate. Do you have to do this with transistors? Look up SN7400.