var interval = null;
    var activeSlideNumber = 0;
    var numberOfSlides = 4;

    $(function()
    {
        startSlideshow();
    });

    function startSlideshow()
    {
        triggerNextSlide();
        interval = setInterval("triggerNextSlide()", 5000);
    }

    function triggerNextSlide()
    {
        resolveActiveSlideNumber();
        setActiveSlide(activeSlideNumber, false);
    }

    function resolveActiveSlideNumber()
    {
        if (activeSlideNumber == numberOfSlides) 
            activeSlideNumber = 1;
        else 
            activeSlideNumber++;
    }

    function stopSlideshow()
    {
        clearInterval(interval);
    }

    function setActiveSlide(number, doStopSlideshow)
    {
        if (doStopSlideshow)
            stopSlideshow();
    
        var iNumber = parseInt(number, 10);

        if (iNumber <= 0 || iNumber > numberOfSlides)
            iNumber = 1;

        activeSlideNumber = iNumber;

        // reset slides
        $("div[id^='slide_']").removeClass("active_slide").addClass("slide");

        // show active slide
        $("#slide_" + activeSlideNumber).removeClass("slide").addClass("active_slide");
    }