function lightButton(oButton) {
         document.images[oButton].src = document.images[oButton].src.substring(0, document.images[oButton].src.length - 6) + "on.gif";
         return true;
 }

 function turnofButton(oButton) {
         document.images[oButton].src = document.images[oButton].src.substring(0, document.images[oButton].src.length - 6) + "of.gif";
         return true;
 }