With the gradual development of smart power plants and large-scale centralized control, there is a need to exchange a large number of signals between different DCS systems and between DCS and PLC systems. Different control systems have different brands and cannot communicate directly via networks. Moreover, due to network security concerns, the main control of unit units and the auxiliary control system of the entire plant cannot communicate directly via networks either. The commonly adopted methods for signal exchange between control systems are hardwiring and 485 communications. Both have obvious drawbacks, where hardwiring requires a large number of channels and cable laying; 485 configuration is difficult, not easy to maintain, and faults are hard to locate. This paper studies how to strike a balance between the two, using a minimal amount of hardwiring to transmit a large number of signals, which is safe, reliable, cost-effective, and can be maintained by any control personnel without network security risks.