Abstract: A self-regulating bubble tube assembly is used for determining the hydrostatic pressure exerted by fluids, such as drilling mud. The bubble tube assembly can be used to determine fluid level based upon said hydrostatic pressure and when bubble tubes are used in pairs can be used to determine a pressure differential that will indicate the density of the fluid. The bubble tube assembly comprises a flow of air directed through a diaphragm type pressure regulator. The pressure regulator output is connected to the bubble tube, which is partially submerged in the fluid, through a precision, in-line, flow limiting orifice. A feedback line from the bubble tube runs to one side of the diaphragm of the pressure regulator where the back pressure from the tube will regulate the output pressure from the regulator to maintain a pre-selected constant rate of air flow through the bubble tube.

Abstract: The method and apparatus enables a terminal to access a computer located at a distance therefrom by an uncomplicated, easy-to-understand, log-on procedure. The system includes a group of terminals which are each able to access a host computer. If desired, the host computer is, in turn, adapted to extend the communication path from the terminal, through the host computer, to the remotely located service computer. The user can establish the communication path to the host computer by a single activation of a terminal key. By activating a single other key, the path is then extended from the host computer to the service computer. The activation of a single further key causes the execution of a selected program.