function ein(i)
{
  if(document.images)
  {
    var src = document.images[i].src;
    var off = src.lastIndexOf("1");
    if(off != -1)
    {
      var newsrc = src.substring(0,off) + "2";
      document.images[i].src = newsrc + ".gif";
    }
  }
}
function aus(i)
{
  if(document.images)
  {
    var src = document.images[i].src;
    var on = src.lastIndexOf("2");
    if(on != -1)
    {
      var newsrc = src.substring(0,on) + "1" + src.substring(on + 1, src.length);
      document.images[i].src = newsrc;
    }
  }
}