Abstract: Local area networks having a high level of network integrity, error detection and correction, message security, expandability and flexibility are disclosed. The system is comprised of a loop controller which may communicate with a host through a standard interface such as an RS232 interface, and to which a plurality of nodes are coupled in a reconfigurable network. Each node has a plurality of modes controlled by the network controller to serve various functions depending upon requests from the controller and/or the needs or condition of the respective node from time to time. In particular, the first node is coupled to the controller through a pair of wires, with each successive node being coupled to the preceding node through a similar pair of wires. In one mode, the respective node monitors the incoming signal from the controller as repeated through any preceding nodes, and itself acts as a signal repeater for the next downstream node.