function start_slideshow(start_frame, end_frame, delay) {
        setTimeout(switch_slides(start_frame,start_frame,end_frame, delay), delay);
}

                                                
function switch_slides(frame, start_frame, end_frame, delay) {
        return (function() {
                Effect.Fade('slideshow' + frame, 2.0);
                if (frame == end_frame) { frame = start_frame; } else { frame = frame + 1; }
                setTimeout("Effect.Appear('slideshow" + frame + "', 2.0);", 950);
                setTimeout(switch_slides(frame, start_frame, end_frame, delay), delay + 950);
        })
}

function muestraLetras(){
  Effect.Appear('letras', 2.0);
}

function ocultaLetras(){
  Effect.Fade('letras', 2.0);
}