A system for low data-rate communication over a modulated direct carrier current, designed to convey payload messages, transmitted asynchronously and at an average frequency from one or a plurality of at least two communication transmitters to a same receiver, through a wire bus using direct carrier current connecting the transmitters and the receiver to each other in series, comprising one or a plurality of at least two communication transmitters (6, 8), a communication receiver, a wire bus with modulated direct carrier current forming a shared transmission channel and connecting the communication transmitters (6, 8) from the plurality and the communication receiver, each communication transmitter (6, 8) being configured to form a first raw transmission frame in the form of a first sequence of a first constant number Nt of binary raw data, encoded over two states chosen from among 0 and 1, the binary raw data sequence forming the first frame being subdivided into a unique and different physical address characterizing the transmitter, a payload, and an error detecting code on the first frame determined from the payload and the physical address of the communication transmitter (6, 8), characterized in that each communication transmitter (6, 8) is configured to spread in frequency, by a predetermined spreading factor SF, the first raw transmission frame in a second transmission frame spread in terms of transmission spectrum, the second spread transmission frame assuming the form of a second sequence of chips and being obtained, by first successively encoding the binary raw data of the first raw transmission frame into symbols with a length of a second predetermined number Ns according to a bijective correspondence rule between the set of all possible sequences of binary raw data with length the second number Ns and a set of two to the power Ns symbols, then next by encoding each obtained symbol in a distinct spreading elementary encoding sequence (222, 224, 226, 228) formed by binary chips, encoded over two states chosen from among 0 and 1, the distinct elementary encoding sequence (222, 224, 226, 228) for spreading depending on the symbol and having for length, a third predetermined integer number of chips defined as the spreading factor SF, and modulating and transmitting, over the wire bus, the chips of the second spread frame in a transmitted communication signal according to a predetermined modulation, in that each elementary spreading sequence is chosen from among the possible chip sequences, with spreading factor SF as length, so as to form a balanced code having a central autocorrelation peak having a first level that is clearly higher than that second levels of the correlation products having correlation shifts, the duration of which is greater than or equal to a chip period, in that the elementary encoding sequences for spreading the symbols used by all of the transmitters (4, 6) are identical, and in that the times of the initial transmission of the second spread frames developed by each transmitter (6, 8) are autonomously and freely determined by each transmitter (6, 8), without taking a synchronization signal outside the transmitter into account (6, 8).