This is an excerpt from a recent educational article by DigiKey:
This article briefly reviews the international safety standards and their applicability. It also examines the uses of the various communications protocols before digging into use cases ranging from tabletop assembly stations to entire factories for types of safety controllers like fixed function, reconfigurable, and expandable models. It presents specific examples using Banner Engineering, Phoenix Contact, Schneider Electric, and Omron Automation products.
Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems (E/E/PE, or E/E/PES), or IEC 61508, is the basic functional safety standard applicable to all industries. It includes methods of applying, designing, deploying, and maintaining automatic protection systems, called safety-related systems. It is based on the idea that any safety-related system must fail in a predictable way that is inherently safe.