In a local area network having a plurality of nodes, wherein the local area network utilizes a token passing scheme for communicating between nodes, each node has an interface apparatus which operates independently of a processor associated with the node. The node can be in an on-line mode or an off-line...http://www.google.com.hk/patents/US4680581?utm_source=gb-gplus-share專利 US4680581 - Local area network special function frames
