ABSTRACT
Programmable logic controllers (PLCs), which are the leading, stand-alone control tools of industrial processes, can be interconnected with each other to exchange data, information, and control signals. The interconnected systems of PLCs offer to an extensive industrial process, flexibility, transparency, and effective coordination of all its parts. The topologies of networks are derived in two basic ways from their node interconnection, point-to-point connection and multi-point interconnection. The star topology of an industrial network has the advantage that the linking of any two PLCs requires two communication lines at most. According to the Master/Slave protocol, a PLC in a communication network is defined as the master PLC, and thus all the remaining PLCs become slaves. In general, all the physical media for the communication of data transfers for classical public communication networks can also be utilized in the case of the industrial networks. The simplest medium for data transmission in a communication network is a twisted-pair cable.
