function slideSwitch(tP) {
  var $active = $('#slideshow'+ tP + ' IMG.active');

  if ( $active.length == 0 ) $active = $('#slideshow IMG:last');

// use this to pull the images in the order they appear in the markup
  var $next =  $active.next().length ? $active.next() : $('#slideshow'+ tP + ' IMG:first');

// Para mostrar las imagenes random
//  var $sibs  = $active.siblings();
//  var rndNum = Math.floor(Math.random() * $sibs.length );
//  var $next  = $( $sibs[ rndNum ] );

  $active.addClass('last-active');

  $next.css({opacity: 0.0})
   .addClass('active')
   .animate({opacity: 1.0}, 1000, function() {
    $active.removeClass('active last-active');
  });
}