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procedure TForm1.Button1Click(Sender: TObject);
var
  CommPort : string;
  hCommFile : THandle;
  ModemStat : DWord;
begin
  CommPort := 'COM2';

  {Open the comm port}
  hCommFile := CreateFile(PChar(CommPort), GENERIC_READ, 0, nil,
  OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
  if hCommFile = INVALID_HANDLE_VALUE then
  begin
    ShowMessage('Unable to open '+ CommPort);
    exit;
  end;

  {Get the Modem Status}
  if GetCommModemStatus(hCommFile, ModemStat) <> false then
  begin
    if ModemStat and MS_CTS_ON <> 0 then
      ShowMessage('The CTS (clear-to-send) is on.');
    if ModemStat and MS_DSR_ON <> 0 then
      ShowMessage('The DSR (data-set-ready) is on.');
    if ModemStat and MS_RING_ON <> 0 then
      ShowMessage('The ring indicator is on.');
    if ModemStat and MS_RLSD_ON <> 0 then
      ShowMessage('The RLSD (receive-line-signal-detect) is on.');
  end;

  {Close the comm port}
  CloseHandle(hCommFile);
end;