FIELD: communication devices operating with first and second formats of signal transmission. SUBSTANCE: synchronous transmission method uses frames, which are transmitted to given positions of frame, and involves preliminary definition of main frame position corresponding to one of given positions in frame in receivers using first format for signal transmission. System values are transmitted and stored in receivers for possibility to check at least one position in frame by receivers. Also at least one frame position is detected from preliminary defined main frame position and system values. Frames of first format for signal transmission are transmitted periodically. Second format for signal transmission is sent between periodic transmission of first format signals. EFFECT: possibility to upgrade existing communication system using short synchronous format to use modern long synchronous format in order to decrease power consumption. 10 cl, 7 dwg
