What type of gate is used to indicate the failure in outputs when one of two identical parallel circuits fails?

The correct choice in this scenario is the XOR (exclusive OR) gate. An XOR gate is designed to output a true (or high) signal only when the inputs differ. When employed in a context where two identical parallel circuits are monitored, the XOR gate will indicate a failure if one of the circuits is functioning correctly while the other is not.

Specifically, if both circuits are operational, the output of the XOR gate will be low because the two inputs are the same. Conversely, if one circuit fails and the other operates normally, the outputs differ, prompting the XOR gate to produce a high signal. This functionality—indicating a mismatch between the two inputs—is essential for detecting failures in parallel systems, making the XOR gate the appropriate choice for this scenario.

In contrast, the other gates would not be suitable for this specific need: an AND gate would only signal a failure if both circuits were working (outputting high), while an OR gate would output high if at least one circuit works, failing to provide a clear failure indication. A NOR gate would only output a high signal when both inputs are low, which is not relevant for identifying individual circuit failures. Thus, the design and function of the XOR gate make it the best fit for