This graphic depicts the ICS process flow. We see the field devices that provide the process data. This is where the actual physical process happens, be it the mixing of chemicals or the management of trains, or the measuring of the pressure of gas at a certain point in a pipeline.
A field controller collects information from field devices and assesses, manages, and processes state information about the process.
The HMI monitors the information and presents it to an operator. The operator uses the HMI to observe the process, watch for events and alarms, and to make decisions or adjust the system to keep the process stable and safe, as required. The operator function can be performed by a person, or a system such as an EMS, DCS, or any a specialized system that may be unique to a particular sector.
