Hi,

I've solved a few problems in my HW where it asks to write the boolean expression describing the function of a circuit.

My main question is if I understand the problem correctly. (There weren't clear examples from the text.) In the attachment, a simple example is problem a). What I'm assuming for the truth table (and subsequent problems), is that if switch A is open (low), then the current flows on the branch between R1 and A, which then "pushes" that unnamed switch closed (high).

In this example, when A = 0 (open), Z = 0 since the unnamed switch is closed, and the wire which the reference point, Zout is on is thus connected to ground.

If A = 1 (closed), then Zout is HIGH, since this shorts the wire in the branch containing A, and the current travels along it to ground. This leaves the unnamed switch open, as there's not enough "electrical pressure" to close it since A was shorted.

It seems to make sense to me. Is this correct, and the way I've thought about it?

 

Your answer to a looks good to me up to the sum of peoducts line. Compare your sum of products to the boolean table.
Look here and I think you will find a more appropriate gate symbol.
b looks good.

 

b looks good.

at the very end ***? "sum of the products"
also the boolean term (wiki -- not the best reference src.) for A=0 ?is A̅ while for A=1 it's A . . . if follow wiki using my understanding of logic
the bt for A=0=A·A̅ and A=1=A+A̅ the same above ***