Technology has advanced beyond physical buttons, switches, and indicator lamps, but these components are still widely used in manufacturing and processing facilities. Even though main control interfaces could be graphic interfaces with touch panels, the physical abuse it receives may easily overwhelm the hardiness of the device. In situations where heavy machinery is utilized or bulky safety gear is worn, a large start-stop button and flashing red light are more effective for operators.
There are standard ratings for the degree of protection, or ruggedness, of equipment components; NEMA or IEC (IP) ratings. Both rate how much physical and environmental abuse a component can withstand, but differ among each other over the exact scaling of the ratings. Something as trivial as a button may be rated quite highly on either scale simply for being designed with repeated pressing in mind, “A case in point is the repeated pressing of a door close button on an elevator when someone is in a hurry.”
Stack lights and indicators are used to give an operator a quick snapshot of the state of a machine. Green lights most often signal everything is in order; red typically indicates some type of problem. NFPA 79 lists some recommended colors for different situations.
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