Programmable Logic Controller (PLC)
 PLCs have found numerous applications in industrial and other uses. While they have advantages over electromechanical relays, they also have limitations. Discuss the advantages and limitations of PLCs over electromechanical relays. 
 
 A Programmable Logic Controller (PLC) is a specialized computer. It has all the basic elements that any other computer has: a Central Processing Unit (CPU), memory, input interfacing and output interfacing. The CPU is the control portion of the PLC. It interprets the program commands retrieved from memory and acts on those commands. In present day PLC’s, this unit is a microprocessor based system. The CPU is housed in the processor module of modularized systems. 
Programmable Logic Controller (PLC