American Telephone and Telegraph, Co.

At&t Information Systems Inc.

William L Aranguren

Michael J Sidey

Mario A Restrepo

A modular, hierarchical local area network is realizable by using existing twisted pair wiring, for example, in a building together with several elements known as network access units and hub units. A network access unit is connected to a device (microprocessor, display terminal, peripheral device, other local area network, information systems network or the like) in the local area network to give that device access to and from the network. The network access device is designed for simple daisy chaining with other devices to form a node when devices are colocated in the same section or room in the building. The hub unit is the network building block which permits extensive expansion of the local area network. It provides a connection point for access units or other hub units, performs collision detection operations, if necessary, and serves as a loop-back point for the network. Switchably connectable termination impedances and loop-backs are automatically passed to the appropriate points in the local area network. While most small local area networks are considered for intra-building applications, the present network is applicable to inter-building applications, also.

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Wayside, NJ, United States of America

William L Aranguren