function showTab()
{ var t1 = document.getElementById("tb1");
  var t2 = document.getElementById("tb2");
  var op = document.getElementById("frmBusca");
  
  if( t1.style.display=="none" )
  { t1.style.display = "block";
    t2.style.display = "none";
    op.tipo.value=0;
  }
  else
  { t1.style.display = "none";
    t2.style.display = "block";
    op.tipo.value=1;
  }
}