var isDOM = (document.getElementById);
var isIE4 = (document.all && !isDOM);
var isNS4 = (document.layers);
var isDyn = (isDOM || isIE4 || isNS4);

function getRef(id) {
if (isDOM) return document.getElementById(id);
if (isIE4) return document.all[id];
if (isNS4) return document.layers[id];
}

atw=new Array(new Array(90,70),new Array(75,65),new Array(70,55),new Array(55,45))
atd=new Array(10,15,18,20,22,24)
var dtxdt, prepinac=0;

function norm(h) { d=h.indexOf(","); return parseFloat((d<0)?h:h.substring(0,d)+"."+h.substring(d+1,h.length)) }
function s(tw1x,tw2x,tdx) { return ''+tw1x+'/'+tw2x+'/'+tdx }
function fdtxdt(tw1,tw2,td,tw1x,tw2x,tdx) {
 if (((tw2x-tdx)/(tw1x-tdx))<0.7) {dt=(tw1-tw2)/(Math.log((tw1-td)/(tw2-td))); dtx=(tw1x-tw2x)/(Math.log((tw1x-tdx)/(tw2x-tdx)))}
 else {dt=(tw1+tw2)/2-td; dtx=(tw1x+tw2x)/2-tdx}
 dtxdt=dtx/dt
}
function f(QT,n) {return Math.round(QT*Math.pow(dtxdt,n)) }
function NS() { //uz se nebude nepouzivat
 var appName=navigator.appName
 var appVer=parseFloat(navigator.appVersion.substring(0,4))
 if (!((appName.indexOf("Microsoft")>-1)&&(appVer>=4))) {
  alert("Přepočet funguje pouze pro Internet Explorer 4 a více!"); return 1}
}
function DOM() {
 if ((!document.getElementById) && (!document.all) && !(document.layers)) {
  alert("Funguje pouze v nověj±ích prohlíµečích!"); return 1}
}
function kontrola(tw1x,tw2x,tdx) {
 if ((tw1x<=tw2x) || (tw2x<=tdx)) {alert("Chyba v zadání teplot teplotního spádu!"); return 1}
}
function prepni() {
 if (DOM()) return;
 var retez
 prepinac=!prepinac
 if (prepinac) {
  var jtwx=atw[getRef('twx').selectedIndex], jtdx=atd[getRef('tdx').selectedIndex];
  getRef('ts').innerHTML='<input id="itw1x" name="itw1x" value="'+jtwx[0]+'" size="1"></input><input id="itw2x" name="itw2x" value="'+jtwx[1]+'" size="1"></input><input id="itdx" name="itdx" value="'+jtdx+'" size="1"></input>'
 }
 else {
  var i,prvni=true,retez='<select id="twx" name="twx" size="1">'
  for (i=0;i<atw.length;i++) {
    retez+='<option'; if ( prvni && ((atw[i][0]<=parseInt(getRef('itw1x').value)) || (i==atw.length-1)) ) {retez+=' selected';prvni=false;}
	retez+='>'+atw[i][0]+'/'+atw[i][1]+'</option>'
  }
  retez+='</select><select id="tdx" name="tdx" size="1">'
  prvni=true
  for (i=0;i<atd.length;i++) {
    retez+='<option'; if ( prvni && ((atd[i]>=parseInt(getRef('itdx').value)) || (i==atd.length-1)) ) {retez+=' selected';prvni=false;}
	retez+='>'+atd[i]+'</option>'
  }
  retez+='</select>'
  getRef('ts').innerHTML=retez
 }
}