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专利名称：Reconfigurable collision avoiding system,
station and protocol for a two path multipleaccess digital communications system
发明人：Levinson, Frank Howard,Limb, John Ormond申请号：EP84308841.0申请日：19841218公开号：EP0147994B1公开日：19900926
摘要：In order to control the transfer of packets of information among a plurality ofstations, e.g., digital computers, the instant communications system, station and protocolcontemplate first (10) and second (60) oppositely directed signal paths. At least twostations are coupled to both the first and the second signal paths. A station (70-i)includes arrangements for reading (20-i, 40-i) (and writing (30-i, 50-i)) signals from (andon) each of the two-paths. Signals are read from either path by an arrangement whichelectrically precedes the arrangement for writing signals on the path. If the station has apacket to transmit, it can overwrite a busy control field of a packet on either path. Alsohaving read a packet signal from the path, a logical interpretation may be made withinthe station as to whether the path is busy or is not busy. If the path is not busy, thepacket may be written on the path by overwriting any signal thereon. If the path is busy,the station may defer the writing until the path is detected as not busy e.g. by reading abusy control field of another packet. Here the two paths are coupled to form two ringstructures so the packets flow down the path to a destination station. Eventually allpackets will be transmitted and the busy control field loops around to a station which is
designated as a control station (70-(1,N)). The control station, responsive to detectingthat all packets have been transmitted on one of the paths, may transmit a start cyclepacket on the one path, responsive to which event a new cycle may be started byinitializing each station on the one path and by permitting each initialized station totransmit. In the event of an electrical open (500), the system, station and protocol areadapted to reconfigure the system so that the station (70-i) electrically preceding theopen functions as an end station while the station (70-(i+ 11) electrically succeeding theopen functions as a head station.
申请人：AMERICAN TELEPHONE AND TELEGRAPH COMPANY
地址：550 MADISON AVENUE; NEW YORK, NY 10022
代理机构：Buckley, Christopher Simon Thirsk
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