Current control biasing of a ring laser gyroscope is employed to protect electrode seals. The safety device includes a first valve for closing the oil intake in the filter with a view to dismantle the filter, a second bypass valve that opens when the filter is blocked and a third valve that opens in the event of excess pressure in the hydraulic circuit. At least one layer constituting the second active material layer is formed before forming all layers constituting the first active material layer, thereby preventing heat for forming at least one of the layers constituting the second active material layer from being applied to all layers constituting the first active material layer. Another port from the inner housing discharges water outside the outer housing and defines a static liquid level. Other embodiments provide a data aggregation module that aggregates indexes calculated by the indexing module that may be also be displayed. This movement causes the pressure inside the ink discharge holes to change and, as a result, the ink inside the ink discharge holes is absorbed.