Abstract: The invention relates to electrical network communications engineering and can be used in systems for automatic data collection from intrusion protection and fire alarm sensors, electric, heat, water, gas meters and fiscal memory data devices for cash registers. The technical result is significant reduction of power consumption in transmitters of system slave units and/or expansion of its operation. A unique random or pseudo-random set of initial phase differences for the adjacent harmonic pairs is used to encode each character of transmitted data, and these sets of initial phase differences are selected in such a way as to minimize crest factor of a total signal. When a fire-alarm sensor is actuated, it is sufficient to transmit only one symbol to an alarm panel which, unambiguously identifies the location of the active sensor and as a rule is embodied in the form of a conventional number or address pre-allocated to the sensor.