Abstract: Local area networks having a plurality of stations connected to a transmission medium in a daisy chain configuration at the nodes or endpoints experience difficulty in detecting collisions between signals transmitted from two or more stations using standard Manchester violation or lost carrier collision detection techniques. The present invention eliminates collision detection problems in this environment almost entirely by monitoring the signal level coupled from the transmission medium to each station of the daisy chain to detect the presence or absence of collisions and generating a collision detection output signal when the signal level being monitored exceeds a predetermined threshold level.

Abstract: 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.