Abstract: A data communications system is disclosed which uses a passive communications medium such as coaxial cable for communication between multiple stations connected to the bus. A token concept is employed such that when the token is owned by a station, it allows that station to transmit high level messages over the bus and to command, if desired, other stations to transmit high level messages to it. The communications system is primarily masterless with each station capable of token ownership using the same set of rules to determine the circumstances when perceived events by the station cause that station to change state. Improvements are presented in the initialization of a token list, the addition of stations to an existing token list, duplicate station address protection through random numbers associated with each station, power down patch out of a station from the token list, the joining of two networks (two token lists), timer period randomization, and the use of redundant communication mediums.

Abstract: A data communication system is disclosed that utilizes a synchronized serial bus for communication between multiple stations connected to the bus. A token is employed such that when owned by a station it allows that station to transmit high level messages over the bus and command other stations to transmit high level messages to it if required by the token owner. Fundamental events called primitives are perceived by stations. Each station capable of token ownership embodies the same set of rules, the rules in turn defining the circumstances when perceived events cause a station to change from one state to another.Fundamental sets of rules, or modules, are used in the communication system to achieve a system for the automatic generation of a token list of stations with periodic ownership of the token, as well as for expansion or contraction of this token list. In addition, automatic change in the token pass handshake protocol is described.