Data communication system

A data communication system is disclosed which is particularly suited for "in-house" or localized on-line data transactions. The system includes a central communication processing unit, such as a digital computer, coupled to a plurality of remotely located units through a single, wide bandwidth, bidirectional communication line, such as a coaxial cable. The system includes interface logic for coupling a large number of remote units to the communication line in a "daisy chain" configuration, thereby permitting all remote units to have simultaneous access to the single communication line. An addressing scheme is provided to allow selective data transactions to be carried between the central communication processing unit and individual remote units.