var Interv = 900;
function startClock2() {
	Interv = Interv - 1;
	
	if (Interv < 0) {
		window.location.href="index.php"; 
		Interv = 900;
	}

	document.getElementById('cas').value = Interv;
	timrID = setTimeout("startClock2()", 1000);
}