Abstract: In order to carry out data transfer among the subsystems of a bus oriented data processing system, each subsystem is coupled to the bus by a local bus adapter which controls both source and destination aspects of the information transfer. Each local bus adapter has a unique "busy" line which may be interrogated by any local bus adapter connected to the bus. When a source subsystem wishes to transfer information to a destination subsystem, the source local bus adapter determines from the destination local bus adapter's busy line whether or not the destination subsystem is available to accept the information. If the destination subsystem is available, the source local bus adapter requests access to the bus from priority resolution apparatus.