Are placed on dangerous machinery to detect motion, light, heat, pressure, or another stimulus. their presence protect operators from injury while working on machines.
mirrors
labels
sensors
alarms

Answer;

-Sensors

-Sensors are placed on dangerous machinery to detect motion, light, heat, pressure, or another stimulus. Their presence helps protect operators from injury while working on machines.

Explanation;

-Machinery, safety and factory floor sensors and switches help workers become more productive, efficient, and safe.

-Hazardous machines and systems are frequently equipped with safety elements (safety doors) with a locking mechanism to protect the operator. Their function is to prevent hazardous machine functions if the safety door is not closed and locked and to keep the safety door closed and locked until the risk of injury has passed.

.) the observation by semmelweis that more mothers died of childbed fever when their doctors also worked in the morgue

an electric circuit