PURPOSE: To attain surely and easily changeover by slave stations in systems I and II by adopting the constitution that a changeover section allows to distribute a reception station number data and an item data of the system I or II and to fetch a reception data of the systems I and II thereby obtaining the reception data of the corresponding slave station.
CONSTITUTION: The changeover section is provided with a decoding circuit 71 decoding a slave station number data of the transmission data, a line state discrimination logic circuit 72 discriminating to which line of the systems I, II of the transmission lines each slave station is connected, a line selection circuit 73 obtaining a line selection command as to a destination slave station of the transmission data from a decoding signal of the decoding circuit and the discrimination output of the logic circuit, a gate circuit 74 outputting distributingly the transmission data to the transmission section of the systems I, II depending on a selection command and a gate circuit 75 fetching the reception data from a couple of reception sections alternately and obtaining the reception data. The transmission changeover is discriminated by the slave station number of the reception data and the item data of the slave station by the system of the reception data and the reception data is obtained by fetching alternately the data of a couple of the reception sections.
TOMINAKA SHIYOUZOU
AOKI KIYOSHI
