Abstract: An Integrated Services Digital Network module includes a time division multiplexed switching network. Subscribers are connected to the time division multiplex network via a number of facility interface cards. These facility interface cards provide for two wire subscriber connection, four wire subscriber connection, T1 line connection and for three port conferencing arrangements. Originating and terminating multiplexers connect the facility interface cards to the time switching network. Another subsystem provides protocol interfaces for HDLC channels. Another subsystem provides interface to central office switching systems. Lastly, a general purpose computer and file computer system provide for the storage of database and form maintenance functions. Each subsystem is controlled via processor which is linked with each of the other processors by an ethernet local area network. This system provides both Primary Rate (23B+D) and Basic Rate (2B+D) interfaces to the subscribers.