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    unit carrier;
    { detects carrier on modem line }

    interface
    uses dos;

    implementation

    Function carrierDetected( ComPort : byte ) : Boolean;
    const
     MSR            = 6;
     BASEPORT      : Array[1..4] Of Word = ($03F8, $02F8, $03E8, $02E8);

    begin
       CarrierDetected := (Port[basePort[ComPort] + MSR] And 128) <> 128;
    {true = no carrier}
    end;

    end.

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