SCADA (supervisory control and data acquisition)

SCADA (supervisory control and data acquisition) generally refers to industrial control systems (ICS): computer systems that monitor and control industrial, infrastructure, or facility-based processes, as described below:
•    Industrial processes include those of manufacturing, production, power generation, fabrication, and refining, and may run in continuous, batch, repetitive, or discrete modes.
•    Infrastructure processes may be public or private, and include water treatment and distribution, wastewater collection and treatment, oil and gas pipelines, electrical power transmission and distribution, Wind farms, civil defense siren systems, and large communication systems.
•    Facility processes occur both in public facilities and private ones, including buildings, airports, ships, and space stations. They monitor and control HVAC, access, and energy consumption.
A SCADA system usually consists of the following subsystems:
•    A Human–machine interface or HMI is the apparatus which presents process data to a human operator, and through this, the human operator monitors and controls the process.
•    A supervisory (computer) system, gathering (acquiring) data on the process and sending commands (control) to the process.
•    Remote terminal units (RTUs) connecting to sensors in the process, converting sensor signals to digital data and sending digital data to the supervisory system.
•    Programmable logic controller (PLCs) used as field devices because they are more economical, versatile, flexible, and configurable than special-purpose RTUs.
•    Communication infrastructure connecting the supervisory system to the remote terminal units
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