Glossary:PLC
A PLC or Programmable Logic Controller is a device much used in industry for controlling plant and machinery. It has a number of inputs which would be connected to sensors of different kinds, and outputs through which it can control switches, valves, motors, pumps etc in order for the machine or industrial process to operate correctly and safely. Their pre-electronic origins lie in relay logic and they are still normally programmed by similar ladder logic as their predecessors.