that are widely separated geographically. A SCADA system uses remote terminal units (RTUs) to send supervisory data back to a control centre. Most RTU systems always had some capacity to handle local control while the master station is not available. However, over the years, RTU systems have grown more and more capable of handling local control.

The boundaries between DCS and SCADA/PLC systems are blurring as time goes on. The technical limits that drove the