A data communications system for conveying load control commands, power usage data, and other data on electric power lines. A remote module for reading the power usage meters and controlling loads is disposed at each power usage location. A group of remote modules convey their power usage data to an associated communications terminal to be accumulated, organized and stored. The group also receives load control commands from the communications terminal to cause them to initiate specific load control functions. There are a plurality of communications terminals disposed at various intervals along the primary distribution feeders. A central control unit collects the usage data from the remote modules, generates load control commands, and the like. Communications between the control unit and a destination communications terminal are relayed by the intermediate communications terminals. If an intermediate communications terminal should fail to relay communications properly, the central control unit and the other communications terminals isolate and by-pass the malfunctioning unit. If a communications terminal should fail to communicate properly with its associated group of remote modules, another communications terminal can be programmed to assume its function.