Control module through the backplane and each input/output module communication, the site of a variety of measurement, control operation of the signal input to the control module, the control module operation and then output to the output module, and then through the output module sent to the site of each actuator for real-time control. The voltage module inserted on the backplane delivers working power to various modules through the backplane. The communication module inserted on the backplane communicates with the operator station (PC), workstation (WS), upper control unit and other PLC or DCS.