Abstract: In a data transmission system, a given data transmission apparatus or station (STN) transfers a transmission start command (indicating the start of transmission) to an associated terminal thereof when the given station receives a send request signal from a distant terminal (T). Conversely, the given station receives data from the distant station through a high-speed transmission line and at the same time transfers a reception request command (indicating a reception request) to its associated terminal. The given terminal (as opposed to the distant terminal) transfers transmission data for a desired distant terminal to the given station when the command is a transmission start command, and the given terminal is then held in the status waiting state. However, when the command is a reception request command, the given station transfers the reception start signal to the given station and is held in the data waiting state.