code: public int subscribe_event(String attr_name, int event, CallBack callback, String[] filters)
              throws DevFailed {
          if (!useEvents())
              Except.throw_exception("NO_EVENT", "Event system not available", "DeviceProxy.subscribe_event()");
          if (event==TangoConst.INTERFACE_CHANGE)
              Except.throw_exception("BAD_EVENT",
                      TangoConst.eventNames[event] + " cannot be applied to an attribute");
          return deviceProxyDAO.subscribe_event(this, attr_name, event, callback, filters, false);
      }
docs: ==========================================================================