FIELD: communication equipment. SUBSTANCE: data transmission uses duplex transmission line between functional elements, each of which has functional transmission line control unit, which has functional units for starting and controlling data transmission through transmission line using synchronization pieces, which are designed for information exchange between functional transmission line control units. Exchange of synchronization pieces is controlled by means of finite state synchronization automaton, which has three states. In search state, functional transmission line control unit analyzes synchronization piece which is received from transmission line in order to compare it to preliminarily defined synchronization piece combination. In preliminary synchronization state, which arises after detection of preliminarily defined synchronization piece combination, functional transmission line control unit analyzes preset number of synchronization pieces which follow it in order to detect, whether they contain preliminarily defined combination. If this is not the case, then automaton returns to search state. In synchronization state, which is started after detection of preliminarily defined number of synchronization pieces, which contain preliminarily defined combination in the process of preliminary synchronization, method involves data transmission through data transmission line with data check to detect errors. When errors are detected, control procedure switches into search state. EFFECT: increased speed of synchronization and possibility to process data elements of different size. 21 cl, 14 dwg
