Abstract: A method and apparatus for communicating signals from within an encased borehole including a wireless communications system for transmitting down-hole environmental data signals between a down-hole tool and a surface receiver. The down-hole tool is disposed within a borehole encased in an electrically conductive casing; the receiver is located at the ground surface. The tool includes a conductive upper and lower tool housing, a plurality of down-hole sensors, and a signal generating device. The sensors and signal generating device are housed within the tool. The generating device receives analog or digital signals of the down-hole environmental conditions from the sensors, converts these signals into a modulation pattern signal which is applied to a carrier signal and conducts a modulated carrier signal into the upper and lower tool housings. An upper contactor or spreader electrically connects the upper housing to a first position on an inside wall of the casing.

Abstract: An MWD EM data/control telemetry link between down-hole instruments and ground surface instruments dynamically adapts to the underground electrical environment utilizing a down-hole microprocessor unit and a surface data processing unit (computer) each of which continuously monitors, probes and sweeps the frequency spectrum with EM signals to determine an optimum frequency for signal transmission between the respective units via either the drill string, the surrounding strata, or both, and then generates and digitally modulates a carrier signal at such optimum frequency with data/control signals.

Abstract: Measurement while drilling apparatus for detecting and communicating information relative to downhole parameters and/or characteristics of the earth strata via an electrically conductive drill string composed of a plurality of lengths of metallic pipe connected end-to-end in series and through which a drilling fluid is caused to flow and then return to the surface through the well cavity formed between the exterior wall of the drill string and the interior wall of the well comprising a DC voltage supply for establishing a unidirectional biasing current passing through the electrically conductive drill string, drill bit and surrounding earth strata, a colloidal suspension of ferro-magnetic particles coated with a non-conductive coating forming a part of the drilling fluid and carried by the drilling fluid through the well cavity wherein the ferromagnetic particles are caused by the magnetic field to migrate toward the outer surface of the drill string and to form an insulative coating thereon, a downhole modul

Abstract: An information while drilling apparatus and method for characterizing strata in the vicinity of a drill bit at the lower end of a drill string, including a down-hole module unit and surface receiving and control units. Excitation currents are caused to pass through the drill string, drill bit and surrounding strata and the current flowing through the drill bit is sensed by a first toroidal transformer that encircles the drill string immediately above the drill bit. The sensed current, which characterizes the strata adjacent to and below the drill bit, is detected to form logging signals. A second toroidal transformer couples the logging signals to the electrically conductive drill string for transmission to the surface receiving unit. The frequency of the excitation current is adjustable to permit characterization of the strata at various distances from the drill bit.

Abstract: An improved method and apparatus for underwater communication, the apparatus comprising two dipoles disposed in a common body of water, both dipoles including a pair of separated electrodes, a transmitter connected to one dipole, a receiver connected to the other dipole and a nonconducting hose or tube extending between one of the electrodes of a first dipole and one of the electrodes of the second dipole.

Abstract: A moisture protective housing for a sound transducer located inside the face mask of a diver which face mask is vented to a breathing apparatus, such as a scuba tank with regulator, to maintain the air breathed by the diver at substantially the same pressure as the water surrounding the diver. The housing includes a deformable portion having pin prick perforations or pores therethrough to make that portion porous when formed. The number of perforations or pores, as well as their size, are selected such that the porous portion becomes permeable to air and/or water only if the pressure differential across it exceeds a preselected value.