var xmlhttp;

	function doMath()
	{
		var formObj = document.forms[0];	
		document.getElementById('graph').src='images/loader.gif';
		var voltage_clean = formObj.voltage.value.replace(/[^\d]/,'');
		var model = formObj.model.value;
		do_calculation(voltage_clean, model);

	}


function do_calculation(voltage_clean, model)
{
xmlhttp=GetXmlHttpObject();
if (xmlhttp==null)
  {
  alert ("Browser does not support HTTP Request");
  return;
  }
var url="calculation.php";
url=url+"?v="+voltage_clean+"&model="+model;
url=url+"&sid="+Math.random();
xmlhttp.onreadystatechange=stateChanged;
xmlhttp.open("GET",url,true);
xmlhttp.send(null);
}

function stateChanged()
{
if (xmlhttp.readyState==4)
{
document.getElementById("txtHint").innerHTML=xmlhttp.responseText;
}
}

function GetXmlHttpObject()
{
if (window.XMLHttpRequest)
  {
  // code for IE7+, Firefox, Chrome, Opera, Safari
  return new XMLHttpRequest();
  }
if (window.ActiveXObject)
  {
  // code for IE6, IE5
  return new ActiveXObject("Microsoft.XMLHTTP");
  }
return null;
}