var anzahl = 4;
var i = 0;

function setactiv(activ)
{
	for(var j = 0; j < anzahl;j++)
	{	
		var slide_name = "slide_" + j;
		var btn_name = "button_" + j;
		if(j == activ)
		{
			document.getElementById(slide_name).style.display='block';
			document.getElementById(btn_name).setAttribute("class", "slider_button_activ");
		}
		else
		{	
			document.getElementById(slide_name).style.display='none';	
			document.getElementById(btn_name).setAttribute("class", "slider_button_inactiv");
		}
	}	
}


function timer(shownr)
{
	i=shownr;
	var activ = i % anzahl;
	for(var j = 0; j < anzahl;j++)
	{	
		var slide_name = "slide_" + j;
		var btn_name = "button_" + j;
		if(j == activ)
		{
			document.getElementById(slide_name).style.display='block';
			document.getElementById(btn_name).setAttribute("class", "slider_button_activ");
		}
		else
		{	
			document.getElementById(slide_name).style.display='none';	
			document.getElementById(btn_name).setAttribute("class", "slider_button_inactiv");
		}
	}	
	i++;
	var endless = window.setTimeout("timer(" + i + ")", 10000);	
}
//Timer starten
timer(0);