var teletextChannel = 'CT1';
var teletextPage = '100';

function updateTeletext()
{
  if (teletextChannel == 'CT1')
  {
    document.images['teletext'].src='http://www.czech-tv.cz/teletext/picture.php?channel=0&page='+teletextPage;
    return;
  }
  if (teletextChannel == 'CT2')
  {
    document.images['teletext'].src='http://www.czech-tv.cz/teletext/picture.php?channel=1&page='+teletextPage;
    return;
  }
  if (teletextChannel == 'Prima')
  {
    document.images['teletext'].src='http://platan.vc.cvut.cz/cgi-bin/httpttx/prima/latest/cp1250/pge320x350/'+teletextPage+'?todo=img320x350';
    return;
  }
  if (teletextChannel == 'Nova')
  {
    document.images['teletext'].src='http://www.ntext.cz/teletext/TTX_Pages/nova/GIF/p'+teletextPage+'A.gif';
    return;
  }
}

function setTeletextPage(page)
{
  teletextPage = page;
  updateTeletext();
}

function setTeletextChannel(channel)
{
  teletextChannel = channel;
  
// standard
  teletextPage = '100';

// exceptions
  if (teletextChannel == 'Prima')
  {
    teletextPage = '100-01';
  }
  
  document.forms['formular'].pagenumber.value = teletextPage;
  updateTeletext();
}