Abstract: A computer network is disclosed in which a plurality of computer stations are interconnected by a single bi-directional bus and wherein access to the bus is controlled by the computer stations themselves through an adapter unit at each station. Each adapter unit includes a microcontroller, a transmitter, a receiver, a send buffer, a receive buffer, a line activity indicator, a pulse producing device, a read circuit and a write circuit. Each adapter unit has a unique assigned number. When the network is running and stable, control of the bus is continually passed from one live adapter unit to another in numerical sequence according to its unique assigned number and the bus is active with messages, control signals or status signals separated by relatively short intervals. If only one adapter unit is live, control is continually passed to itself.

Abstract: A computer network is disclosed in which a plurality of computer work stations are interconnected for interstation communications by a single electrically continuous bi-directional bus. Each computer work station includes a data processing device and a transceiver. The transceiver includes a receiver section for receiving signals transmitted over the bus and a transmitter section for transmitting signals onto the bus. The receiver section is coupled to the input of the data processing device by a first optical isolator and the transmitter section is coupled to the output of the data processing device by a second optical isolator. The data processing device and the first optical isolator are powered by a first power supply which is connected and grounded to the AC mains while the transceiver and second optical isolator are powered by a second power supply which is connected to the neutral conductor on the bus and is floating.

Abstract: A computer network is disclosed in which a plurality of computer stations are interconnected by a single bus and wherein access to the bus is controlled by the computer stations themselves through an adapter unit at each station. Each adapter unit is assigned a unique number. When the network is running normally, control of the bus is continually passed from one live adapter unit to another in numerical sequence and the bus is active with messages, control signals or status signals from the particular adapter unit that happens to be in control at the time. If, for any reason, there should be no activity on the bus for a preselected time interval, all adapter units detecting this condition enter an election mode to elect from amongst themselves one adapter unit to assume control and resume activity. In the election mode, each participating adapter unit sends a pulse out over the bus and then monitors the bus for activity for a time period directly proportional to its assigned number.