function swapImage(id, source) {
		obj = document.getElementById(id);
		obj.src = source;
	}
	
	function ZoomPlan(id, sens) {
		j=1;
		for (i=1;i<4;i++) {
			obj = document.getElementById(id+i);
			if (obj.style.visibility=="visible") j=i;
			obj.style.visibility="hidden";
		}
		j+=sens;
		if (j==4) j=3;
		if (j==0) j=1;
		obj = document.getElementById(id+j);
		obj.style.visibility="visible";
	}