Programmable Logic Controllers

Before the advent of solid-state logic circuits, logical control systems were designed and built exclusively around electromechanical relays. Relays are far from obsolete in modern design, but have been replaced in many of their former roles as logic-level control devices, relegated most often to those applications demanding high current and/or high voltage switching.

Systems and processes requiring "on/off" control abound in modern commerce and industry, but such control systems are...

Programmable Logic Controllers