Abstract: A level device is designed to determine different levelling points in building work to automatically set certain parts, such as the suspension systems for false ceilings when this apparatus is fitted with a bolt-driving attachment, comprising a flexible tube connected to a first chamber closed by a first diaphragm offering very low resistance to the liquid contained, the other end of the tube connected to a second chamber closed by a second diaphragm which second diaphragm offers resistance to the liquid contained and compresses the air contained in the corresponding space whereby in turn this air actuates a diaphragm which has needle-type contact switches, on each side, these circuits to an indicator, with a valve used to locate the apparatus at a point which may be at a higher or lower level than that determined by the first diaphragm.

Abstract: Apparatus for comparing the level of two spaced points, to find which is higher or lower, and possibly also for determining the magnitude of the difference in level of the points. The apparatus comprises two chambers that communicate with each other through a flexible conduit. The conduit and the lower portion of each chamber is filled with liquid, preferably mercury, whose level in each chamber varies as the elevations of the chambers relative to each other. An electric circuit interconnects the chambers; and the circuit is opened or closed upon variation in the relative levels of the chambers; or the amount of current flowing in the circuit is progressively changed with changes in the relative elevation of the chambers. Various embodiments of circuit for achieving this are disclosed, including make-or-break contacts, a variable capacitor, a variable resistance slide wire, and a variable resistance deformable strain gauge.