Data link arrangement with error checking and retransmission control
[451 Apr. s, 1975 United States Patent [1 1 Winn et al.  
 [ DATA LINK ARRANGEMENT WITH ERROR CHECKING AND RETRANSMISSION Primary Examiner-Charles E. Atkinson CONTROL Attorney, Agent, or Firm-John T. Winburn Inventors: Melvin Winn, Lombard William R.  
 Wedmore, Glen Ellyn; John S. Young, Addison, all of Ill.  
 [5 7] ABSTRACT At each end of a four wire transmission facility, there is a transmitter and a receiver, used between the base location of a toll service position system (TSPS) and a traffic office having operator positions. The messages [73] Assignee: GTE Automatic Electric Laboratories Incorporated, Nofthlake. are used for functions such as lighting lamps and sig- [221 Filed: Sept. 14, 1973 nalling operation of keys. There are buffer stores for a number of messages, and they are given sequence l PP 397,454 numbers from one to seven. If there is an error such as a sequence number other than one expected next, or a Bose-Chandhuri check error indication, a retransmis- [52] US. 340/1461 BA sion request message is sent. In response thereto, all messages subsequent to the last sequence number cor- [5l] Int. G06f 11/08; G08C 25/02 [58] Field of Search 340/146.1 BA, 172.5  
 rectly received before the error was detected are re- {56] References Cited transmitted, the first retransmitted message having a retransmission flag as a part thereof. At the receiving UNITED STATES PATENTS end all messages received after the erroneous mes- BA sages are rejected until the one with the flag bit set is BA received. The rejected messages are counted, with a g: maintenance request if a given number is exceeded. BA 9 Claims, 70 Drawing Figures Ill-ill McClelland Perrault et Paine et Maggio.........  
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 POSITION STATUS BUFFER RECORD w mg FULL POS. FLAG MESSAGE 51 A STATUS CONTROL (NSG) NEW 1 STATUS OVERVIEW DIAG RAM BUFFER STORE CONTROL SEQUENCE NUMBER COUNTERS (SNC) INPUT SEQUENCE NUMBER -IS7( SPD) ONE 2 (NSCFKRS CKTJ ONE 2 (NSG)KTB ISNO (NSG )-ITB ISNI (SPD) ISN FF ISN2 15m E2 ONEZ RE-TRANSMISSON RECUEST DETECTOR RRP Es-[ Bcc.RRF FFB RRP (me) To f (we) TI E6 &#39;11)- ONE 2 OUTPUT SEQUENCE NUMBER COUNTER I osm (s a moan-FD,  
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