var isStart=true;
var nn;
var tt;

nn=1;
setTimeout('change_img()',4000);


function change_img(){
	if(isStart){
		nn++;
 		if(nn>7) nn=1;
 		setFocus(nn);
 	}else{
 		tt=setTimeout('change_img()',100);
 	}
}

function setFocus(i){
	if(tt) clearTimeout(tt);
 	nn = i;
 	selectLayer1(i);
 	tt=setTimeout('change_img()',4000);
}

function selectLayer1(i){
	switch(i){
	case 1:
		document.getElementById("bbs_s1").style.display="block";
		document.getElementById("bbs_s2").style.display="none";
		document.getElementById("bbs_s3").style.display="none";
		document.getElementById("bbs_s4").style.display="none";
		document.getElementById("bbs_s5").style.display="none";
		document.getElementById("bbs_s6").style.display="none";
		document.getElementById("bbs_s7").style.display="none";
 		break;
	case 2:
		document.getElementById("bbs_s1").style.display="none";
		document.getElementById("bbs_s2").style.display="block";
		document.getElementById("bbs_s3").style.display="none";
		document.getElementById("bbs_s4").style.display="none";
		document.getElementById("bbs_s5").style.display="none";
		document.getElementById("bbs_s6").style.display="none";
		document.getElementById("bbs_s7").style.display="none";
		break;
	case 3:
		document.getElementById("bbs_s1").style.display="none";
		document.getElementById("bbs_s2").style.display="none";
		document.getElementById("bbs_s3").style.display="block";
		document.getElementById("bbs_s4").style.display="none";
		document.getElementById("bbs_s5").style.display="none";
		document.getElementById("bbs_s6").style.display="none";
		document.getElementById("bbs_s7").style.display="none";
 	break;
	case 4:
		document.getElementById("bbs_s1").style.display="none";
		document.getElementById("bbs_s2").style.display="none";
		document.getElementById("bbs_s3").style.display="none";
		document.getElementById("bbs_s4").style.display="block";
		document.getElementById("bbs_s5").style.display="none";
		document.getElementById("bbs_s6").style.display="none";
		document.getElementById("bbs_s7").style.display="none";
 	break;
	case 5:
		document.getElementById("bbs_s1").style.display="none";
		document.getElementById("bbs_s2").style.display="none";
		document.getElementById("bbs_s3").style.display="none";
		document.getElementById("bbs_s4").style.display="none";
		document.getElementById("bbs_s5").style.display="block";
		document.getElementById("bbs_s6").style.display="none";
		document.getElementById("bbs_s7").style.display="none";
 	break;
	case 6:
		document.getElementById("bbs_s1").style.display="none";
		document.getElementById("bbs_s2").style.display="none";
		document.getElementById("bbs_s3").style.display="none";
		document.getElementById("bbs_s4").style.display="none";
		document.getElementById("bbs_s5").style.display="none";
		document.getElementById("bbs_s6").style.display="block";
		document.getElementById("bbs_s7").style.display="none";
 	break;	
	case 7:
		document.getElementById("bbs_s1").style.display="none";
		document.getElementById("bbs_s2").style.display="none";
		document.getElementById("bbs_s3").style.display="none";
		document.getElementById("bbs_s4").style.display="none";
		document.getElementById("bbs_s5").style.display="none";
		document.getElementById("bbs_s6").style.display="none";
		document.getElementById("bbs_s7").style.display="block";
 	break;
	}
}