NewImg = new Array (
"slides/bus1.png",
"slides/bus4.png",
"slides/bus2.png",
"slides/bus5.png",
"slides/bus3.png",
"slides/bus6.png",
"slides/bus7.png"
);
var ImgNum = 0;
var ImgLength = NewImg.length - 1;

//Time delay between Slides in milliseconds
var delay = 6000;

var lock = false;
var run;
function chgImg(direction) {
if (document.images) {
ImgNum = ImgNum + direction;
if (ImgNum > ImgLength) {
ImgNum = 0;
}
if (ImgNum < 0) {
ImgNum = ImgLength;
}
document.slideshow.src = NewImg[ImgNum];
   }
}
function auto() {
if (lock == true) {
lock = false;
window.clearInterval(run);
}
else if (lock == false) {
lock = true;
run = setInterval("chgImg(1)", delay);
   }
}