SITUATION

A single sensor has been used to detect excessive levels of a contaminant in a chemical process. Its output is "0" for normal conditions and "1" when the impurity level becomes too high. An evaluation program shows that the sensor is subject to occasional false alarms; also, it sometimes fails to operate when the contaminant level is high.

To improve the situation, it is decided to use three sensors and to disregard the indication of any single sensor whose output differs from the other two sensors. It is desired to have a single "correct signal" output which will be "0" for normal conditions and "1" for an excessive contaminant level, and "alarm" output which will be "0" when all sensor outputs are identical ("0" or "1") and which will latch into a "1" output at any time when the three sensor outputs become not identical. Also, an "alarm reset" input is to be provided such that a "1" input to it will reset the alarm output to zero after an alarm condition ceases to exist.

REQUIRED

Design a logic system to meet the above requirements. The system is to be implemented with NOR logic. There are no "fan in" or "fan out" limitations, that is, any NOR gate can have as many inputs as may be needed and can drive any necessary number of gates from its output.

Your solution should include:

1. A truth table for the "correct signal" and "alarm" output.

2. The logic...