This document discusses Programmable Logic Controllers (PLCs) and Supervisory Control and Data Acquisition (SCADA) systems. It provides background on PLCs, describing them as digital electronic devices that use programmable memory to implement logic, sequencing and other control functions. It then discusses the history and components of PLCs, as well as common brands and applications. For SCADA, it defines the system and describes its components and how it is used to monitor and control industrial processes through remote data collection and centralized monitoring.