we find the process control layer. this level includes the hardware that interfaces with the sensors and actuators and executes the control system logic. any controller or control platform,whether it is a motion controller,loop controller,programmable logic controller (PLC),hybrid distributed control system (HDCS),or distributed control system (DCS),has its processor control module located at this level. this level will also include the networks that communicate from the processors to the input/output (I/O) racks that collect signals as well as the networks that communicate peer to peer between processors.functionality at this level involves any function that monitors process variables and operator commands,executes decision logic based on that data,and sends command signals to the process as a result of those data. in this regard,this level contains the true heart of the control and automation system.