Below is the list of the major components of an Industrial Control Systems (ICS):
• Master Terminal Unit (MTU) or SCADA Server. In a SCADA system the SCADA server is device that acts as the master. PLC and RTU located at remote field site usually act as slaves.
• Control Server, the control server hosts the PLC or DCS supervisory control software which is designed to communicate with lower level control devices.
• Remote Terminal Unit, RTU is also called as a remote telemetry unit. It is special purpose control unit and data acquisition designed to support SCADA remote stations.
• Programmable Logic Controller, the PLC is a small industrial computer originally designed to perform logic function that executed by electrical hardware such as, switches, relays, and mechanical timer or counters.
• Intelligent Electronic Devices, IED is a smart actuator or sensor containing the intelligence required to acquire data, perform local processing and control, and communicate to others devices.
• Human Machine Interface, the HMI is hardware and software that allows human operators to monitor the state of a process under control.
• Data Historian, the history of data is a centralized database for logging all process information within an ICS.
• Input/Output Server, the IO server is a control component responsible for collecting, providing and buffering access to process information from control sub components such as, IEDs, PLCs, and RTUs.