def brighten(self, defer_update=False):
        """Brighten the device one step."""
        msg = X10Send.unit_code_msg(self.address.x10_housecode,
                                    self.address.x10_unitcode)
        self._send_method(msg)

        msg = X10Send.command_msg(self.address.x10_housecode,
                                  X10_COMMAND_BRIGHT)
        self._send_method(msg, False)
        if not defer_update:
            self._update_subscribers(self._value + 255 / self._steps)