In the past, relay devices were the main components for industrial automation control systems, and some existing factories still use them today. But in today’s complicated systems, relays provide limited use, poor flexibility and unreliable stability. Moreover, they are not easily maintained, the control panel is big and heavy, and is not easy to move. With the advent of PLC & PC-based control systems, new systems can easily benefit from easy configuration, high flexibility and high stability. One steel factory was looking to upgrade their system with a new PLC-based control system with a redundant Ethernet network.