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High speed half duplex modem with fast turnaround protocol

  • US 4,894,847 A
  • Filed: 05/26/1987
  • Issued: 01/16/1990
  • Est. Priority Date: 05/26/1987
  • Status: Expired due to Term
First Claim
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1. A V.22 bis compatible handshake method for an originating modem for establishing communications with an answering modem at a selected speed of 1200 bits per seconds (bps), 2400 bps, or greater than 2400 bps, comprising:

  • (a) said originating modem sending a first sequence for a first predetermined period;

    (b) said originating modem sending a second sequence for a second predetermined period while listening for said first sequence from said answering modem;

    (c)(1) if said first sequence from said answering modem was not heard by said originating modem, said originating modem commencing communications with said answering modem at 1200 bps;

    (2) if said first sequence from said answering modem was heard by said originating modem, said originating modem sending a third sequence for a third predetermined period while listening for said second sequence from said answering modem;

    (d)(1) if said second sequence from said answering modem was not heard by said originating modem, said originating modem continuing to send said third sequence for an additional period of time and then commencing training and communications with said answering modem at 2400 bps; and

    (2) if said second sequence from said answering modem was heard by said originating modem, said originating modem commencing training and communications with said answering modem at a speed greater than 2400 bps.

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