Abstract: An apparatus for sensing the horizontal level of a table or other surface and returning that table or other surface back to level. The apparatus includes a housing within which first and second mercury switches are positioned relative to each other in a manner which permits the electrical contacts of each switch to be positioned on opposite ends of the housing. Two spring clips are provided for securing the first and second mercury switches within the housing. A pivot rod is provided to permit each mercury switch and spring clip assembly to pivot about a transverse axis within the housing. An adjusting screw and stablizing spring pair are positioned adjacent to each of the two mercury switch and spring clip assemblies. The adjusting screws may be turned to set the position of the mercury switch about the axis of the pivot rod relative to the horizontal plane in order to set a dead band wherein neither of the two mercury switches is closed.

Abstract: An apparatus for locking an wheeled table into a fixed location is disclosed. The base of the table is provided with both an electric motor coupled to a hydraulic pump and a manually operated hydraulic pump either of which may provide a source of pressurized hydraulic fluid. Extendable and retractable legs are provided on the base of the surgical table. Hydraulic cylinders disposed adjacent to each of the legs are provided with upper link members pivotally attached to the table's base and lower link members which are pivotally attached to the deployable legs. When pressurized hydraulic fluid is provided by the electrically driven or manually powered hydraulic pumps, the hydraulic cylinders disposed adjacent to the deployable legs are extended. Such extension is translated by means of the respective upper and lower link members into a vertical movement which lowers the supporting legs to fix the table in a specified location.