A multi-access bus topology used in local-area. In which all node share a singe transmission medium. That is, all node are attached to the same communication line. A node sand a massage to another node, it appends destination address to the massage and checks whether communication lines are free. As soon as line become free, it broadcasts massage on the line. As the massage travels on the line, each node checks whether the massage is addressed to it. This types of network is also know as ‘multi-point’, ‘multi-drop’ or ‘broadcast’ network.