Which wiring configuration implements NOR logic?

• A. Two normally-closed switches in series
• B. One normally closed switch
• C. Two normally-open switches in series
• D. Two normally-open switches in parallel

Answer: (A)

NOR logic gives a high output only when both inputs are inactive. In wiring terms, using normally closed switches means the path is complete by default (when the inputs are not activating the switches). Placing two normally closed switches in series creates a path that remains closed only if both inputs are idle. If either input becomes active, its switch opens and the circuit breaks, causing the output to drop. This matches the NOR truth table: the output is high only when both inputs are false.

A single normally closed switch would only invert one input, not both. Two normally open switches in series would require both inputs to be active to complete the path (an AND behavior). Two normally open switches in parallel would complete if either input is active (an OR behavior).