var previewTimer = 0;
  var previewCounter = 1;
  var previewRunning = false;
  var previewPictures = new Array();
  var previewPath = 'senderklein/';

  function startSwitch(id)
  {
    if (previewRunning)
      return false;

    previewRunning = true;
    doSwitch(id);
    previewTimer = window.setInterval('doSwitch('+id+')',1000);
  }

  function doSwitch(id)
  {
    if (previewPictures[id][previewCounter] == undefined)
      previewCounter = 0;

    document.getElementById('previewPic' + id).style.background = 'url('+previewPath+id+'/t'+previewPictures[id][previewCounter]+'.jpg)';
    previewCounter++;
  }

  function stopSwitch()
  {
    previewRunning = false;
    previewTimer = window.clearInterval(previewTimer);
  }