The instruments and sensors that measure process parameters and the actuators that control the process. This is the interface between the ICS and the physical process, be it the mixing of chemicals, the management of trains, or measuring of pressures in a gas pipeline.
This is the point in the system where information is collected about the process, modifications are made, and the process is controlled. The sensors or measuring instruments are often referred to as input devices because they “input” data into the ICS. In contrast, switches, valves, and other types of actuators that control the process are called output devices. This input and output information is often referred to as I/O.
Copyright: Cybersecurity & Infrastructure Security Agency