After the line device has been selected and activated successfully with monitoring privileges, you are able to receive call state events. A new incoming call will cause the OnOffering and OnCallState (Offering) events to be triggered.

Use the calls Answer method to answer the call. May you need to check the ownership of the call prior to answer it.

Example:

procedure TForm1.Create(Sender: TObject);
begin
  hbTapiLine1.DeviceName := 'Sample Line Device';
  hbTapiLine1.MediaModes := LINEMEDIAMODE_INTERACTIVEVOICE;
  hbTapiLine1.Privileges.Owner := True;
  hbTapiLine1.Privileges.Monitor := True;
  try
    hbTapiLine1.Active := True;
  except
    on EhbTapiError do
      MessageDlg('Initialization failed!' + E.Message, mtError, [mbOk], 0);
  end;
end;

procedure TForm1.hbTapiLine1CallState(Sender: ThbTapiLine; Call: ThbTapiCall; CallState: Cardinal);
begin
  case CallState of
    LINECALLSTATE_OFFERING :
    begin
      try
        if not Call.Owner then
          Call.Owner := True;
        Call.Answer;
      except
        
      end;
  end;
end;