Abstract: The extendible building post includes a telescoping hydraulic cylinder integrated within a construction member externally configured and dimensioned essentially identically to a conventional building construction member, e.g., a four-by-four or six-by-six length of lumber, or alternatively a plastic column. The hydraulic system may be formed of stock plastic pipe and fittings, and may use water as the working fluid. The device may include insulation and a heating system to prevent freezing when used in such an environment, with certain types of insulation also providing additional rigidity for the hydraulic assembly.

Abstract: An apparatus is disclosed for determining a measured direction such as the direction of a ship or airplane relative to an external magnetic field such as the magnetic field of the earth. This apparatus comprises means for establishing a magnetic field rotating at constant angular velocity, located to influence the external magnetic field. The rotating magnetic field vector bears a known angular relationship as a function of time to the measured direction. A detector is located to be influenced by the rotating and external fields for detecting the occurrence of a predetermined angular relationship between the rotating and external magnetic field vectors.