Como saber se a impressora esta ligada

procedure TForm1.Imprimir( Porta, Texto : String; Tempo : Integer );
Var TempoFinal : TDateTime ;
    IsTimeOut : Boolean ;
    TP : ThreadEnviaLPT ;
begin
  TempoFinal := IncMilliSecond(now,Tempo) ;
  IsTimeOut  := false ;

  TP := ThreadEnviaLPT.Create( Porta, Texto ) ;
  try
     while (not TP.Terminated) and (not IsTimeOut) do
     begin
        IsTimeOut := (now >  TempoFinal) ;
        sleep(50) ;
        Application.ProcessMessages ;
     end ;
  finally
     TP.Terminate ;
     TP.Free ;

     if IsTimeOut then
        raise Exception.CreateFmt( ´Impressora em: ¬s nao está pronta´,[Edit2.Text]) ;
  end ;

end;

type
  ThreadEnviaLPT = class(TThread)
  private
    { Private declarations }
    fsTexto : String ;
    fsPorta : String ;
  protected
    procedure Execute ; override;
  public
    constructor Create(Porta,Texto : String) ;
  end;

implementation

constructor ThreadEnviaLPT.Create( Porta,Texto : String);
begin
  inherited Create( false) ;  { Rodar Imediatamente }

//  FreeOnTerminate := true ;
  fsPorta := Porta ;
  fsTexto := Texto ;
end;


procedure ThreadEnviaLPT.Execute;
Var ArqPrn: TextFile;
begin
  AssignFile( ArqPrn, fsPorta );

  try
     ReWrite( ArqPrn );
     Write( ArqPrn, fsTexto ) ;
  finally
     System.CloseFile( ArqPrn ) ;
  end ;

  Terminate ;
end;

  Imprimir( ´LPT1´, #0, 100);   { 100 milisegundos }