// Laden aller Bilder in den Speicher
if (document.images)
{
	but_on = new Image();
	but_on.src ="pics/but_2.gif" ;
	but_off = new Image();
	but_off.src ="pics/but_1.gif" ;

	}

function on (buttonname,imgname)
{
        if (document.images)
        {
                imgOn = eval(buttonname + "_on.src");
                if (imgname)
					document[imgname].src = imgOn;
				else
					document[buttonname].src = imgOn;					
        }
		return true;
}

function off(buttonname,imgname)
{
        if (document.images)
        {
                imgOff = eval(buttonname + "_off.src");
                if (imgname)
	                document[imgname].src = imgOff;
				else
	                document[buttonname].src = imgOff;
        }
		return true;
		

}