Considerations on Customer Access to the ISDN

A concept for a digital customer access to an integrated services digital network (ISDN) is proposed. It is based on a passive bus which conveys information by means of two circuit switched B channels and a channel to support associated signaling (outslot channel) dynamically multiplexed with slow speed packetized data and telemetry. The customer access can support multiple terminal arrangements with simultaneously active users. Information to be conveyed by the channel is transferred in the form of messages, each associated with a logical link which has to coexist with other logical links on the common physical channel. Access to that channel is regulated by level 1 arbitration with collision avoidance. It is possible to connect one X.25 DTE with minimum adaptation to the customer installation.