//--------------------------------------------------
function ch(xid)
{
  pfad_o = xid.src;
  pos    = pfad_o.lastIndexOf("_");
  pos++;
  num    = pfad_o.substring(pos,pos+1);
  pfad_n = pfad_o.substring(0,pos);

  if(num == 1)
    num = 2;
  else
    num = 1;

  pfad_n += num + ".gif";

  xid.src = pfad_n;
}
//--------------------------------------------------