Andrew Parr is an Industrial Control Engineer, recently retired from ASW Sheerness Steel, Sheerness, UK who worked in the steel industry for over thirty years. In 1980 he began specializing in sequence and closed loop control systems using Programmable Controllers (PLCs) with hydraulic and pneumatic actuators. He has written fifteen books on electronics and process control including Logic Designers Handbook, Industrial Control Handbook, Programmable Controllers, Control Engineering, along with many amateur- level books, among them Introduction to Operational Amplifiers. His books have been widely translated into many languages, including Japanese, Polish, and Swedish. He and has presented papers at various international conferences, including ones on "Automation Systems in the Steel Industry" and on "Automated Fault Diagnostics".