Abstract: A centralized control system for controlling loads includes local or slave control stations, the number of which corresponds with the number of electric motors as loads, the local control stations each executing control of the making and breaking of each motor main circuit, a start compensating operation, and overload and phase-loss protection operations; a key or master control station for transmitting signals for making and breaking each motor main circuit, data signals associated with a soft starting period, and tripping conditions to each local control station, to thereby control the local control stations in a centralized manner; and optical fiber cables connecting between the key control station and the local control stations for data transmission so that a line of loop signal transmission path is formed. When optical signals are supplied to each local control station from the key control station, the optical signals are converted to electrical signals at each local control station.