function removeString(s, t)
{
	i = s.indexOf(t);
	r = "";
	if (i == -1) return s;
	r += s.substring(0,i) + removeString(s.substring(i + t.length), t);
	return r;
}

function AlternarImagen(img)
{
	var searchString = '_ON';
	var imgSrc = img.src.toUpperCase();
	var index = imgSrc.indexOf(searchString);
	if ( index > 0 )
	{
		img.src = removeString(imgSrc, searchString).toLowerCase();
	}
	else
	{
		var ext = imgSrc.substring(imgSrc.length-4, imgSrc.length );
		var leading = imgSrc.substring(0, imgSrc.length-4);
		var trailing = imgSrc.substring(imgSrc.length-4, imgSrc.length);
		img.src = (leading + searchString + trailing).toLowerCase();
	}
}